NASA/TM—2010-216247

Liquid Oxygen Propellant Densifi cation Production

and Performance Test Results With a Large-Scale

Flight-Weight Propellant Tank for the X33 RLV

Thomas M. Tomsik and Michael L. Meyer

Glenn Research Center, Cleveland, Ohio

May 2010
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NASA/TM—2010-216247

Liquid Oxygen Propellant Densifi cation Production

and Performance Test Results With a Large-Scale

Flight-Weight Propellant Tank for the X33 RLV

Thomas M. Tomsik and Michael L. Meyer

Glenn Research Center, Cleveland, Ohio

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

May 2010
Acknowledgments

The authors would like to extend their appreciation to the technical staff members of Sierra Lobo Inc., Milan, Ohio, for their

signifi cant contributions to the densifi cation program including conducting LOX PDU assembly, build-up facility systems and

providing test operations support at the NASA GRC S40 facility during the LOX PDU test series. South-Forty facility design,

build-up and test operations with the LO2 PDU and the STA test articles, were also acknowledged and gratefully supported by

contributions from other groups including NASA GRC research engineers, the GRC Facility and Test Engineering Division,

contractor employees from the Dynacs Engineering Company, and several individuals from the LMMSS company, principally

Mr. Timothy Knowles.

Trade names and trademarks are used in this report for identifi cation

only. Their usage does not constitute an offi cial endorsement,

either expressed or implied, by the National Aeronautics and

Space Administration.

Level of Review: This material has been technically reviewed by technical management.

Available from

NASA Center for Aerospace Information National Technical Information Service

7115 Standard Drive 5301 Shawnee Road

Hanover, MD 21076–1320 Alexandria, VA 22312

Available electronically at http://gltrs.grc.nasa.gov
TABLE of CONTENTS

i. ABSTRACT ...................................................................................... 3

ii. LIST of FIGURES ............................................................................. 5

iii. LIST of TABLES .............................................................................. 10

iv. NOMENCLATURE ............................................................................ 11

1. INTRODUCTION ............................................................................... 13

1.1 Background ............................................................................... 13

1.2 Benefits of Densified Propellants ....................................................... 14

1.3 LO2 Densification GSE Design and Analysis ........................................ 16

1.4 LO2 Densification Test Objectives .................................................... 20

2. DENSIFIER HARDWARE TEST ARTICLES .......................................... 21

2.1 LO2 Densification Skid (LO2 PDU) .................................................. 21

2.2 LO2 Recirculation Pump ................................................................ 23

2.3 LO2 Heat Exchangers ................................................................... 24

2.4 GN2 Compressor System ................................................................ 26

2.5 VJ and Process Piping .................................................................. 28

2.6 PDU Utility Gas Systems ............................................................... 29

2.7 LO2 Densifier Electrical Systems ..................................................... 29

2.8 Skid Instrumentation and Controls ................................................... 30

2.9 Densifier Operator Interface and Data Logging ..................................... 31

3. STA TEST ARTICLE – LO2 PROPELLANT TANK .................................. 32

3.1 LO2 STA Tank Description ............................................................ 32

3.2 STA Mechanical Design ................................................................ 32

3.3 STA Insulation ........................................................................... 33

3.4 STA Fluid Interfaces .................................................................... 34

3.5 STA Structural Support Platform ..................................................... 35

3.6 STA Tank Internal Instrumentation ................................................... 35

4. SOUTH FORTY TEST FACILITY ......................................................... 37

4.1 General Facility Description ............................................................ 37

4.2 Liquid Nitrogen System – Dewar N-71 .............................................. 38

4.3 Liquid Oxygen System – Dewar N-83 ................................................ 38

4.4 Gaseous Nitrogen System .............................................................. 39

NASA/TM—2010-216247 1
5.

6.

TABLE of CONTENTS (continued)

4.5 Gaseous Helium System ................................................................ 40

4.6 Facility Vacuum Jacketed Piping ...................................................... 40

4.7 S40 Facility Test Article Vents ........................................................ 42

4.8 S40 Electrical Systems .................................................................. 43

4.9 Facility Safety Systems .................................................................. 43

4.10 Facility Instrumentation and Controls ................................................ 44

TEST OPERATIONS and PROCEDURES ............................................... 44

5.1 Gaseous Nitrogen Compressor Check-Out Test Procedures ...................... 45

5.2 LO2 Pump Check-Out Test Procedures .............................................. 45

5.3 LO2 and LN2 Performance Test Procedures with LOX PDU ..................... 47

5.4 STA Boil-Off Test Procedure with LO2 or LN2 .................................... 49

5.5 LO2 or LN2 Closed-Loop Thermal Stratification Test Procedures

with the LOX PDU ..................................................................... 50

TEST RESULTS ................................................................................ 51

6.1 Test Results Summary .................................................................. 51

6.2 Gaseous Nitrogen Compressor Tests .................................................. 52

6.3 LO2 Pump Performance Tests ......................................................... 60

6.4 STA Structural Loading Tests with NBP LN2 ....................................... 63

6.5 STA Boil-Off Testing ................................................................... 68

6.5.1 LN2 Boil-Off Result ........................................................... 68

6.5.2 LO2 Boil-Off Result ........................................................... 69

6.6 LN2 Performance Tests with LOX PDU ............................................. 70

6.6.1 LN2 Performance Test Results – DLN2 Loading of STA ............... 70

6.6.2 LN2 Closed-Loop Thermal Stratification Test 5A Results ............... 76

6.7 LO2 Performance Tests with LOX PDU ............................................. 79

6.8 STA Closed-Loop Thermal Stratification Testing with LO2 ....................... 86

CONCLUDING REMARKS .................................................................. 92

REFERENCES ................................................................................... 94

APPENDIX A – LO2 PDU TEST ARTICLE INSTRUMENTATION ................. 95

APPENDIX B – STA TANKING TABLE .................................................. 99

APPENDIX C – S40 FACILITY INSTRUMENTATION ................................ 103

APPENDIX D – GN2 COMPRESSOR TEST DATA .................................... 106

APPENDIX E – LO2 RECIRCULATION PUMP TEST DATA ...................... 118

APPENDIX F – LN2 PERFORMANCE TEST DATA with LOX PDU ............... 123

APPENDIX G – LO2 PERFORMANCE TEST DATA with LOX PDU .............. 131

APPENDIX H – LO2 PDU and S40 FACILITY FLOW SCHEMATICS ............. 141

7.

8.

NASA/TM—2010-216247 2
i. ABSTRACT

The NASA Glenn Research Center (GRC) has led the nation’s effort in the development

of practical densified cryogenic propellants for aerospace and launch vehicle applications. The

technology of sub-cooling cryogenic propellants below their normal boiling point (NBP), and

thereby making the fluid denser, is one of the key process technologies necessary to meet the

challenge of single-stage-to-orbit (SSTO) and second-generation reusable launch vehicles (RLV).

Densified propellants are critical to achieving lower launch costs because they enable additional

cryogenic propellant to be packed into a given unit volume, thereby improving the performance

of a launch vehicle, effectively reducing its overall size and dry weight. Density improvements of

8% greater for LH2 and 10% for LO2 are expected to substantially reduce the gross lift-off

weight of a launch vehicle system, as studies project by up to 20 percent.

Glenn research engineers were formerly working on providing a method, hardware and

critical test data for the continuous production of densified liquid hydrogen (LH2) and densified

liquid oxygen (LO2) at a large scale. Both propellant densification production units were

configured with a high-efficiency, sub-atmospheric boiling bath heat exchanger to cool the

working fluid. A near triple-point liquid hydrogen boiling bath was used to condition and subcool

hydrogen product down to 27 oR, and a nitrogen boiling bath at 117 oR to provide the heat sink to

cool liquid oxygen down to 120 oR. Multistage high-speed centrifugal compressors, operating at

cryogenic inlet conditions were used to maintain the ullage pressure in each heat exchanger bath

below one atmosphere pressure. The LO2 propellant densification unit (PDU) that was

constructed by GRC had a processing capacity of 30 lbm/sec while the LH2 unit was designed to

produce 8 lb/sec of high-density hydrogen. Both of the these larger cryogenic densification

systems were 15:1 and 4:1 scaled-up versions, respectively, of a prototype 2.0 lb/sec LH2

densifier previously designed, built and tested at the GRC Plum Brook Station in 1996 [ref. 1, 2].

The purpose of this paper is to describe in-detail a test program that was initiated at the

Glenn Research Center (GRC) involving the cryogenic densification of liquid oxygen (LO2). A

large scale LO2 propellant densification ground support system (GSE) sized for the X-33 LO2

propellant tank, was designed, then fabricated and tested at the GRC. Multiple objectives of the

test program included validation of LO2 production unit hardware and characterization of LO2

densifier performance at both design and transient conditions. First, GSE performance data is

presented for an initial series of LO2 densifier screening and check-out tests using liquid nitrogen

(LN2) as a surrogate fluid to be densified. The second series of test results described in this

report is performance data collected during LO2 densifier operations and testing with liquid

oxygen as the product fluid. Densifier experimental results will be summarized and compared

against known design point values and predicted analytical conditions. Other key topical areas

that this paper will address includes a general discussion of the thermodynamic model and

process for super-cooling LO2 propellant, a description of the LO2 GSE system hardware, an

explanation of the GRC South-Forty (S40) facility test-site and details of operational run

procedures that were used during LO2 densifier testing.

NASA/TM—2010-216247 3
Finally, one other very important facet of the overall test program that needs to be

mentioned was that it was organized in collaboration with the Lockheed Martin Michoud Space

Systems (LMMSS) group. A technology development plan was developed for the program with

the objectives of investigating LO2 tank loading operations and testing the thermal stratification

phenomenon inside of a flight-weight launch vehicle propellant tank. An overview of the LO2 X33 tanking, de-tanking and loading tests with the 20,000 gallon Structural Test Article (STA) is

reported on here.

In conclusion, the demonstration and testing of the LO2 propellant densification system,

and its operational capability, was successfully completed at the GRC in December 2000. In

excess of 200,000 gallons of densified LO2 at 120 o R was produced with the Propellant

Densification Unit during the demonstration program. In tank thermal stratification conditions

were also demonstrated during the densification of the STA propellant tank. These were

milestone achievements in the field of cryogenic propellants that will allow subsequent private

industry commercialization of a new technology having benefit to space applications involving

potential future launch vehicle systems like VentureStar, Space-Liner 100, Kistler K1, Second

Generation RLV and ARES V.

NASA/TM—2010-216247 4
ii. LIST of FIGURES

Fig 1. Propellant densification GSE integration concept with RLV ................................ 13

Fig 2. The Liquid Oxygen Propellant Densification Unit (PDU) in the final stages of

check-out and assembly at the NASA GRC Hangar ......................................... 14

Fig 3. The LMMSS tank designated the Structural Test Article (STA) shown integrated

with the densification unit at the GRC South Forty Test Facility ........................... 14

Fig 4. Propellant densification was base-lined for use on the Lockheed Martin reusable

launch vehicle VentureStar ...................................................................... 15

Fig 5. Propellant densification mission benefits include increased payload capability over

NBP cryogenic bi-propellants ................................................................... 15

Fig 6. Liquid oxygen density and vapor pressure curves illustrates fluid property

enhancement by super-cooling .................................................................. 16

Fig 7. Recirculation of Liquid Oxygen from X-33 tank through ground based Propellant

Densification Unit (PDU) ........................................................................ 17

Fig 8. Thermal stratification of STA tank and temperature equilibrium condition at

completion of LO2 densification process ...................................................... 17

Fig 9. Liquid oxygen propellant densification skid equipped with five major components:

the GN2 cryogenic compressor, two LO2-to-LN2 heat exchangers in series, a phase

separator and the LO2 recirculation pump .................................................... 20

Fig 10. LO2 propellant densification skid equipment layout and overall size of 65’ long

x18’ wide x 11’ tall .............................................................................. 22

Fig 11. Simplified process flow diagram of the LO2 PDU ........................................... 22

Fig 12. Liquid oxygen centrifugal recirculation pump, drive motor and VFD ..................... 24

Fig 13. LO2-to-LN2 heat exchanger vessels in series designed to subcool LO2 (top view) ......24

Fig 14. LO2 heat exchanger pancake coil D-shaped tube bundle assembly ........................ 26

Fig 15. Three stage GN2 compressor system .......................................................... 26

Fig 16. GN2 compressor system stage number 3 – top and front view ...............................27

NASA/TM—2010-216247 5
ii. LIST of FIGURES (continued)

Fig 17. The GN2 phase separator final assembly ...................................................... 27

Fig 18. LO2 densifier process piping, GN2 vents, LO2 VJ lines, and LN2 VJ system ........... 28

Fig 19. The LO2 densifier is self-contained and modular for ease of transportability

as illustrated by this move at the NASA GRC in 1999 ..................................... 29

Fig 20. Operator interface and control console for LO2 densifier ................................. 31

Fig 21. Installation of the STA Tank at the GRC South Forty Test Facility ...................... 32

Fig 22. CATIA general arrangement model of the LO2 STA tank densification test article .... 33

Fig 23. STA tank forward cover plate fluid interfaces ............................................... 34

Fig 24. STA tank 4” VJ fill and drain line – Aft cover plate interface with S40 test site ........ 34

Fig 25. STA tank structural support platform (T153) and access scaffold at S40 ............... 35

Fig 26. STA internal instrumentation mounting arrangement – horizontal view ................. 36

Fig 27. GRC South Forty (S40) LO2 propellant densification test facility ........................ 37

Fig 28. Working end of 13,000 gallon liquid nitrogen dewar N-71 at South Forty ..................38

Fig 29. Liquid oxygen supply dewar N-83 during cryogenic flow testing ......................... 39

Fig 30. South Forty high pressure GN2 storage system rated at 2400 psig and

300,000 scf GN2 capacity ...................................................................... 39

Fig 31. Gaseous helium system schematic for facility LO2 densification test article ............. 40

Fig 32. Densification process facility schematic for LO2 and LN2 systems ....................... 41

Fig 33. South-Forty facility GN2 compressor exhaust vent system ................................. 42

Fig 34. STA test article vent / valve package assembly ............................................. 43

Fig 35. Building 100 control room set-up for LO2 densification test operations ................ 44

Fig 36. Barber-Nichols (BN) and Cryo-Mach (CM) LO2 pump performance curves ........... 46

NASA/TM—2010-216247 6
ii. LIST of FIGURES (continued)

Fig 37. Cryo-Mach spare LO2 pump used during Barber-Nichols pump seal failure

and repairs ........................................................................................ 47

Fig 38. Simplified schematic of LO2 or LN2 Performance tests of LO2 Propellant

Densification Unit at S40 ....................................................................... 48

Fig 39. Simplified schematic of LO2 or LN2 closed-loop thermal stratification tests

of LO2 PDU at S40 ............................................................................. 50

Fig 40. GN2 compressor speed vs. time profile ....................................................... 53

Fig 41. Compressor interstage pressure profile ....................................................... 53

Fig 42. Compressor interstage gas temperature vs. time ............................................ 54

Fig 43. Compressor mass flow rate and gas bypass flow vs. time .................................. 54

Fig 44. Compressor over-current (OC) fault shut-down ............................................. 55

Fig 45. Compressor flow coefficient surge instability shut-down ................................... 55

Fig 46. GN2 compressor high vibration shut-down event ............................................ 56

Fig 47. Compressor high motor winding temperature performance issue ......................... 56

Fig 48. Compressor current and motor winding temperature vs. time ............................. 58

Fig 49. Compressor motor current oscillation vs. speed anomaly .................................. 58

Fig 50. Mechanical shaft seal leakage of LN2 during 9/1/00 pump check-out test ............... 60

Fig 51. Barber-Nichols pump performance test results with LN2 .................................. 61

Fig 52. Cryo-Mach pump performance with LN2. Flow and AP map vs. speed ................. 61

Fig 53. LN2 mass flow rate by manual pump speed control against increasing STA

Back pressure due to changing elevation head ............................................... 62

Fig 54. Cryo-Mach pump performance with LO2. Flow and AP map vs. speed ................. 62

Fig 55. Original STA design twenty-four strut tank support configuration ....................... 64

NASA/TM—2010-216247 7
ii. LIST of FIGURES (continued)

Fig 56. Modified STA support strut configuration on the X-33 LO2 tank for propellant

densification testing ............................................................................. 64

Fig 57. Final as-tested STA eight strut configuration with alternate J-struts installed ........... 66

Fig 58. STA strut test loads during NBP LN2 tank fill .............................................. 67

Fig 59. STA strut test loads during densified LO2 tank fill .......................................... 67

Fig 60. STA tank boil-off test result – GN2 mass flow rate profile ................................. 68

Fig 61. Ice formation and thermal performance loss on the X33 tank SOFI insulation

by mechanical breakage, weathering, cracking and moisture penetration ............... 69

Fig 62. STA tank boil-off test result – gO2 mass flow rate profile ................................. 69

Fig 63. STA vertical temperature gradient during DLN2 loading test 1A ........................ 71

Fig 64. GN2 compressor speed vs. time profile during LN2 performance test 4A ............... 73

Fig 65. GN2 compressor interstage pressures during LN2 performance test 4A ................. 73

Fig 66. LN2 mass flow rate data for LN2 performance test 4A ..................................... 74

Fig 67. STA LN2 vertical temperature gradient at end of DLN2 loading test 4A ................ 74

Fig 68. Compressor outlet GN2 mass flow rate during LN2 performance test 4A ............... 75

Fig 69. Gaseous nitrogen temperature change from 2nd stage heat exchanger ullage

to GN2 compressor first stage suction inlet during LN2 performance test 4A ........... 75

Fig 70. STA LN2 liquid level during recirculation test 5A .......................................... 76

Fig 71. LN2 recirculation and replenishment flow rate profile during test 5A .................... 77

Fig 72. Facility LN2 primary recirculation flow loop temperatures for test 5A ................... 78

Fig 73. STA vertical diode temperature profile during DLN2 recirculation test 5A ............. 78

Fig 74. STA lateral diode temperatures at end of DLN2 recirculation test 5A ..................... 78

NASA/TM—2010-216247 8
ii. LIST of FIGURES (continued)

Fig 75. STA LN2 vertical temperature gradient at end of DLN2 recirculation test 5A

indicating a thermally stratified tank at end of run .......................................... 79

Fig 76. LO2 flow rate and skid outlet pressure – test abort high facility filter

differential pressure .............................................................................. 81

Fig 77. LO2 flow rate and skid outlet pressure - test abort high facility filter

differential pressure - Test 2B ................................................................... 82

Fig 78. LO2 stream temperatures across two-stage heat exchanger system........................ 83

Fig 79. Compressor stage speeds during LO2 performance test 4B ................................ 84

Fig 80. Compressor interstage pressure profile - LO2 performance test 4B ...................... 84

Fig 81. Compressor flow coefficient profile during LO2 performance test 4B ................... 84

Fig 82. Densified LOX flow rate - LO2 performance test 4B ....................................... 85

Fig 83. Dewars N83 and N71 volume change during LO2 performance test 4B .................. 85

Fig 84. STA vertical diode temperature profiles - LO2 performance test 4B ...................... 85

Fig 85. STA thermal stratification temperature profiles with circulating LOX - Test 1C........ 88

Fig 86. STA inlet DLO2 flow rate and STA tank LOX make-up rate............................... 89

Fig 87. STA thermal stratification temperature profiles with circulating LOX - Test 2C........ 89

Fig 88. STA liquid level capacitance probe data with recirculating LOX - Test 3C .............. 90

Fig 89. STA thermal stratification temperature profiles with circulating LOX - Test 3C........ 90

Fig 90. STA ullage pressure during LO2 thermal stratification test 4C ............................. 91

Fig 91. STA thermal stratification temperature profiles with circulating LOX - Test 4C........ 91

Fig 92. STA LO2 resaturation temperature vs time – densified propellant heat-up............... 92

NASA/TM—2010-216247 9
iii. LIST of TABLES

Table 1.0: LO2 recirculation pump design and performance specifications ....................... 23

Table 2.0: LO2 heat exchanger system design and performance data .............................. 25

Table 3.0: GN2 compressor design point conditions ................................................. 28

Table 4.0: STA test article internal instrumentation .................................................. 36

Table 5.0: Program summary of South-Forty LOX densification test activities .................. 52

Table 6.0: Gaseous nitrogen compressor hardware failures and operational issues .............. 57

Table 7.0: Gaseous N2 compressor performance check-out test data and

steady-state (SS) results ..................................................................... 59

Table 8.0: Performance test results with Barber-Nichols LO2 recirculation pump .............. 63

Table 9.0: Test summary – STA structural loading tests with NBP liquid nitrogen ............ 65

Table 10.0: STA boil-off test results summary ........................................................ 68

Table 11.0: Test summary – LN2 performance and closed-loop recirculation testing

ofLO2 PDU ................................................................................. 70

Table 12.0: Steady-state LN2 performance test data measurements with LO2 PDU ............ 72

Table 13.0: Test results summary – LO2 performance testing of LO2 PDU ....................... 79

Table 14.0: Steady-state LO2 performance test data measurements with LO2 PDU............ 80

Table 15.0: Test results summary – LO2 closed-loop thermal stratification testing

ofLO2 PDU .................................................................................. 86

Table 16.0: Steady-state LO2 performance test data measurements with LO2 PDU

during closed loop thermal stratification testing........................................ 87

NASA/TM—2010-216247 10
iv. NOMENCLATURE

A Area, ft2

BHP Brake horsepower

BN Barber-Nichols, Inc. (pump and compressor manufacturer)

CATIA Computer aided three-dimensional interactive application

CM Cryo-Mach Corporation (pump manufacturer)

Cm2 Meridional fluid velocity, ft/sec

DLN2 Densified liquid nitrogen

DLO2 Densified liquid oxygen

FS Full scale

GLOW Gross lift-off weight, lb m

GHe Gaseous helium

GN2 Gaseous nitrogen

GO2 Gaseous oxygen

GRC Glenn Research Center

GSE Ground support equipment

h Enthalpy, Btu/lbm

H Head, ft

Hg Mercury

HP Horsepower

IspvVacuum specific impulse, sec

KVA Kilovolt-amperes

LH2 Liquid hydrogen

LMMSS Lockheed Martin Michoud Space Systems

LN2 Liquid nitrogen

LOX, LO2 Liquid oxygen

LT Level transducer

M Mass, lbm

MAWP Maximum allowable working pressure, psi

MSFC Marshall Space Flight Center

N Speed, rpm

NBP Normal boiling point

Ns

Specific speed, N Qv 0.5 / H 0.75

OC Over-current

OD Outside diameter

OEM Original equipment manufacturer

P Pressure, psia

PC Personal computer

PID Proportional, Integral, Derivative (controllers designed to automate the process)

PDT Differential pressure transducer

PDU Propellant densification unit

PLC Programmable logic controller

PT Pressure transducer

Qe

Environmental heat transfer rate, Btu/sec

NASA/TM—2010-216247 11
iv. NOMENCLATURE (continued)

Qv Volumetric flow rate, ft3/sec

RCI Reusable cryogenic insulation

RLV Reusable launch vehicle

S40 South Forty Densification Test Facility at GRC

SCF Standard cubic feet

SiD Silicon diode

SLI Sierra Lobo, Inc.

SOFI Spray-on foam insulation

SS Steady-state or stainless steel

SSTO Single-stage-to-orbit

STA Structural Test Article

t Time, sec

T Temperature, oR

TC Thermocouple

TP Triple point

TSP Test Support Platform (T153 tool)

U Internal energy, Btu/lb m

U2 Impeller tip speed, ft/sec

V Volume, ft3

VAC Voltage alternating current

VFD Variable frequency drive

VJ Vacuum -jacketed

W Mass flow rate, lbm/sec

Greek symbols:

A Difference or change

`P Head coefficient

(D Flow coefficient

77 Efficiency

P Density, lbm

/ft

3

Subscripts:

1 in

2 out

NASA/TM—2010-216247 12
1. INTRODUCTION

1.1 Background

The propellant densification demonstration subproject under the X-33 and Advanced

Space Transportation Programs was a NASA led Glenn Research Center effort primarily

conducted in-house to validate densification technology at the X-33 scale. The densification units

and project plan were originally

established to be integrated with the

X-33 launch facility at Edwards Air i t

Force Base (figure 1) and to culminate

in actual flight testing with densified

propellants during the X-33 flight test •_

series. During program changes, the

X-33 densified propellant flight test h. A

was eliminated, but the densification ` • . f

effort was redirected to a ground ,^ • ' . ;,

demonstration test of a liquid oxygen _ r

densifier and fabrication and check-out i 1^

of the hydrogen densifier. Glenn LO2 Densifier

Research Center was ultimately

selected to perform the liquid oxygen

LH2 Densifier

and liquid hydrogen propellant Figure 1. Propellant densification GSE integration concept with RLV.

densification testing.

The densification units were designed to subcool propellant in the X-33 propellant tanks

within 2 hours to 27 oR for hydrogen and 120 oR for oxygen. The units were to be portable but

large with a 65-ft long by 18-ft wide footprint and about a 12-ft height. They each included heat

exchangers, compressors, pumps, a structural skid, electrical and instrumentation and controls as

major subsystems. The liquid oxygen test set-up included LN2/LO2 supply dewars, vent stacks,

safety and controls hardware, and a full-sized X-33 LO2 tank, all of which were located at the

Glenn South Forty (S40) test area. A subsequent second-generation RLV program subproject was

funded to test the “sister” hydrogen densifier with liquid nitrogen and a different propellant tank

configuration in the same test area with much of the installation in common with the LO2

densifier. The total combined densification effort spanned over a 4 year schedule to allow

completion of the designs, fabricate the units, build-up the S40 facility and execute the testing.

A liquid oxygen densification unit, shown in figure 2, was designed, built and tested in

December 2000 at the NASA Glenn Research Center (GRC). Development of system

requirements and preliminary design work began at GRC in September 1997. The X-33 scalable

unit was designed to process subcooled liquid oxygen at a nominal rate of 30 lbm/s down to an

outlet temperature of 120 oR. A full-up steady state demonstration and performance verification

test series was then conducted. Testing started in October 2000 and continued through December

2000. Upon completion of the GRC test matrix, a series of five thermal stratification tests with

LO2 were run in collaboration with Lockheed Martin Michoud Space Systems (LMMSS) using

the 20,000 gallon Structural Test Article (STA) LO2 propellant tank from the X-33 program. It

NASA/TM—2010-216247 13
becomes very important in terms of

quantifying the propellant

inventory by test through the

verification of in-tank thermal

stratification characteristics over a

range of inlet recirculation flows as

demonstrated by previous

investigators [ref. 3, 4].

This report presents the

results of LO2 Propellant

Densification Unit (PDU)

performance testing and thermal

stratification tests obtained during

the STA closed-loop recirculation Figure 2. The Liquid Oxygen Propellant Densification Unit (PDU) in the

and cryogenic tankage experiments final stages of check-out and assembly at the NASA GRC Hangar.

conducted at the S40 test facility

seen in figure 3. In general, test

operational and performance goals

with the 30 lbm/sec LO2 densifier ,^• . ^1-^ 1^- f zR

_-.^

were successfully demonstrated with ^.;'0.'i-^..

^ ^ X-33 STA sustained production of densified Tank

LO2 at 120 oR. The achievement of

the planned LO2 demonstration Y r

testing was identified as a “Level 1

Advanced Space Transportation

Program milestone”, and the design

of the densifiers was given the first I•^ - '^

LO2 Densifier Access to Space Turning Goals Into

Reality (TGIR) Award in 1998.

Some of the difficulties and

problems that were overcome during

the LO2 PDU test demonstration Figure 3. The LMMSS tank designated the Structural Test Article (STA) shown

included structural mounting of the

integrated with the densification unit at the GRC South Forty Test Facility.

X-33 LO2 STA tank on its support platform, rework of facility electrical deficiencies that

occurred during original construction, funding gaps, and technical problems including hardware

failures with LO2 pumps, GN2 compressor stages and control systems are described herein as

lessons learned.

1.2 Benefits of Densified Propellants

Propellant densification was identified as a critical enabling technology in the

development of single-stage-to-orbit (SSTO) reusable launch vehicles (RLV). The densification

of a cryogenic propellant through active sub-cooling allows approximately 8 % to 10 % more

propellant mass to be stored in a given unit volume. This allows for a higher propellant mass

fraction than would otherwise be possible with conventional normal boiling point (NBP)

NASA/TM—2010-216247 14
Figure 4. Propellant densification was base-lined for use on the

Lockheed Martin reusable launch vehicle VentureStar.

Data from Various Sources

......................................................._

TP LH2

V 50% SLH2

...........: __________________________________________

DLH2/DLO2

._

..__.__.__*_ ............. _.............. _..............

Earth-to-Orbit OTV LTV MTV Orbiting Depot

Mission Type

Figure 5. Propellant densification mission benefits include increased

payload capability over NBP cryogenic bi-propellants.

cryogenic propellants. In 1998,

densified propellants were base-lined

(figure 4) and considered an enabling

technology for the Lockheed Martin

RLV, designated the VentureStar as a

result of the significant advantages to

be derived from their use.

The enormous benefits

involved for using densified

propellants not only contribute to

vehicle weight reductions, reported to

be on the order of 15 – 25 percent

according to engineering trade studies

[ref. 5, 6, 7 & 8], but densified

propellants could also lower launch

vehicle capital and operating costs by

11 percent or more

and significantly 30

increase mission

payload capability for 25

a^

various launch 20

vehicles and mission a

scenarios. Figure 5 15

illustrates typical

mission payload 10

enhancements from ^m

several data sources, 5

results of which a Z

indicate a range from 0

2 – 26 percent

increase in payload

capability [ref. 9].

In addition to the benefit of a smaller tank size and greater payload capability, other

physical properties (figure 6) of subcooled and densified LO2/LH2 are improved as a function of

temperature (T iO,). Liquid oxygen at its NBP of 162.4 oR has a density of 71.2 lb/ft3 and a vapor

pressure of 14.7 psia. Subcooling LO2 from the NBP to 120 oR, the density is increased 9.7

percent giving a piO, of 78.1 lb/ft3 . At this reduced temperature there is a significant improvement

due to its vapor pressure, which naturally is lowered to 0.50 psia. The benefit derived from a

propellant with a lower vapor pressure allows the tank design pressure, or the MAWP, to be

reduced accordingly, thereby permitting thinner walled tanks of less mass to be used on an RLV.

Finally, lower vapor pressure results in a cryogenic fluid with inherently more stability that is

safer to handle. This results from the fact that over-pressurization of a containment vessel

NASA/TM—2010-216247 15
becomes more difficult as it would take more time to absorb energy in comparison to a fluid at its

NBP because of the additional sensible heat available that the subcooled fluid would absorb

before it begins to boil. Lower vapor pressure reduces the potential for propellant vapor leaks as

the absolute AP between tank and the environment is less for a pressurized vessel containing

densified fluid.

80.0

76.0

w

72.0

.y

68.0

64.0

25.0

20.0

15.0 y

n

10.0

d

`o

n

m

5.0 >

0.0

110 115 120 125 130 135 140 145 150 155 160 165 170

Temperature (oR)

Figure 6. Liquid oxygen density and vapor pressure curves illustrates

fluid property enhancement by super-cooling.

1.3 LO2 Densification GSE Design and Analysis

The densification of liquid oxygen is based on the well-characterized thermodynamic

venting process [ref. 10, 11]. In this section, some fundamental equations for modeling the

performance of the LO2 densification process are presented. The basic densification GSE unit

itself, when integrated with an STA propellant tank as depicted in figure 7, consists of an LO2

recirculation pump, a pair of LN2-to- LO2 heat exchangers in series and a gaseous nitrogen (GN2)

compressor. Assuming a pseudo-steady-state process and constant liquid volume inside of the STA

tank, the LO2 volumetric mass balance around the propellant tank to be densified becomes

L0202 W1 _ 

W L

(1) LO2

LO2

p

1 p2

Equation (1) is based on maintaining a constant fluid volume inside the tank, thus implying

zero liquid level change, resulting in the inlet and outlet volumetric flows being equal (Qv1 = Qv2).

To elaborate the point, by specifying the inlet temperature (T1

LO2) as a design requirement, the inlet

fluid density (p1LO2) is established. Assuming ideal conditions, whereby the propellant tank is

perfectly stratified, the outlet temperature will be at or near the saturation temperature at the tank

operating pressure. Conversely though, the outlet temperature could also be the initial bulk

temperature of the propellant at the start of the densification process. Either of these known

boundary conditions establishes the outlet fluid density ( p2LO2). Therefore, a priori knowledge of

the recirculation flow rate, defined as the inlet mass flow (W1LO2) to STA along with inlet (p1LO2)

and outlet fluid densities (p2LO2), the mass flow rate exiting the propellant tank (W2

LO2

) is easily

determined with the above simplified identity.

NASA/TM—2010-216247 16
XO-2304 and

PVT-2, 3, 4

166 o

120 o

XO-2401 or

XO-2501 —

STA

Outlet

Temp(s)

STA Inlet

Temp

AT = Tout - Tin = constan

THERMAL

EQUILIBRIUM

Figure 7. Recirculation of Liquid Oxygen from X-33 tank through ground based Propellant Densification Unit (PDU).

Thermal stratification

enhances the densification process

by maximizing the temperature

difference between the fluid exiting

the tank and the cold sink that’s used

to extract heat from the propellant. In

order to achieve and maintain the

propellant tank at thermally stratified

conditions, a very important aspect

in the overall performance of the

densification process in terms of the

time (At) required to accomplish the

desired densification (figure 8),

warm saturated liquid is withdrawn

off the top (W2

LO2

), physically using

either a siphon tube or fluid manifold

and the subcooled propellant from

the GSE is returned to the bottom

(WJLO2).

Time (min) 0

Figure 8. Thermal stratification of STA tank and temperature

equilibrium condition at completion of LO2 densification process.

Cold denser fluid entering the bottom displaces the warmer less dense LO2 propellant

vertically upward in what could be described as an ideal “plug-flow” pattern. An inlet propellant

diffuser located at the bottom of the tank can be used to uniformly disperse the propellant.

Relatively low bulk fluid velocity at near laminar flow conditions tends to promote the plug flow

NASA/TM—2010-216247 17
^.!

^LO2

= W1

LO2

(

9O2

− h1

LO2

) = Uo A ∆TLMT'D = Uo A

T

LO2

− T

LO2

1 2

(T

LO2

− T

LN2

 ) 1 at ln (

T

LO2

− T

LN2

 ) 2 sat

(5)

pattern and the thermal stratification gradient that develops inside of the tank. The theoretical timeline ∆t required to densify the initial mass Mi

LO2 of NBP LO2 propellant in a propellant tank is

presented in-terms of an ideal and generalized energy equation for achieving both a net fluid

internal energy change (∆U

LO2) and a mass gain (∆MLO2) of the STA tank contents.

∆t = 

M

LO2

∆ U

LO2

+ U

LO2

∆M

LO2

( ) 2

¢

j„ L

Q − W

LO2

(hi− 

ρ

2 LO2 O2

)

ρ

1 LO2 „

2

The production of super-cold LO2 temperatures is essentially accomplished by

withdrawing saturated liquid oxygen (W2LO2) off the top of the thermally stratified STA tank

through a vertical siphon tube outlet, circulating it through the LO2 pump and heat exchangers of

the propellant densification unit, and returning the propellant subcooled at 120 o

R from the GSE

back into the bottom (W1

LO2

) of the STA tank. Sub-atmospheric pressure LN2 boiling at 2.4 psia

provides the 117 o

R thermal heat sink required to condition the propellant in the LO2 second stage

heat exchanger. The first stage of the heat exchanger system cools LO2 down to about 142 o

R using

multiple parallel coils submerged in an NBP bath of LN2. The LN2 coolant mass feed rate (W1

LN2)

into the critical stage-two heat exchanger is derived from an energy balance on the exchanger that’s

given by:

W1

LN 2

= 

WLO2

(h1 

O2 

− h2

LO2

) + 

WgN2

(h1

gN2

− h

r2

)

(h2

gN2

− h 1

M

)

(3)

The GN2 vent rate (W2

GN2)

from the 2nd stage heat exchanger is then derived from the

nitrogen overall mass balance on the exchanger, whereby this gas flow rate directly feeds the inlet

to the first stage GN2 compressor.

W

gN2

= W

LN2

+ W

gN2

2 1 1

The tubes make-up a large surface area (A) of the GSE heat exchanger and are submerged in

a low temperature boiling bath of LN2 maintained at sub-atmospheric pressure. To generate subcooled LO2 at 120 oR, the heat exchanger bath operating filled with LN2 is reduced to a lower

pressure of 2.4 psia causing the liquid to boil at the saturation temperature (TsatLN2) of 116.9 oR.

The design and performance equation for the cryogenic heat exchanger in terms of the heat

rejection rate from the fluid (QLO2), the overall heat transfer coefficient (Uo) and the log mean

temperature difference (∆TLMTD) allows prediction of the LO2 outlet temperature (T2LO2) albeit a

trial-and-error approach, assuming Uo is known or calculable.

(4)

A low temperature nucleate pool boiling heat transfer process provides the thermal

conditions required to remove heat from the propellant. The inlet LO2 stream is gradually

subcooled as it flows through the D-shaped extruded tubes of the heat exchanger’s constant

temperature bath and exits at the desired 120 o

R outlet temperature (assuming the surface area is

sufficient). The outside heat transfer coefficient ( ho) on the shell-side is best represented by the

NASA/TM—2010-216247 18
nucleate pool boiling heat transfer correlation based on a modified Kutateladze equation correlated

by Brentani & Smith [ref. 12, 13] while the Dittus and Boelter empirical relation for turbulent flow

heat transfer inside a tube of known diameter (di) can be used for calculating the inside heat transfer

coefficient (hi).

(c

1.5 k1.282 P1.75)

ho = 4.87 × 10−11

 (λPV )

1.5 σ

L

0.906 

μ 

0.626 (∆T) 1.5 (6a)

L

h; = 0.023 kL Re 0.8 Pr 0.3 (6b)

d;

Uo =

1

(7)

1



+ A; ln d° 1 + 

1

h; d; 2π km ho

The symbols shown in the heat transfer equations (6a), (6b) and (7) above are defined as follows:

cpL = saturated liquid specific heat, J/g-K

kL = saturated liquid thermal conductivity, W/cm-K

P = pressure, dynes/cm2

∆T = temperature difference, K

λ = heat of vaporization, J/g

ρv = sat’d vapor density, g/cm3

σ = liquid surface tension, dynes/cm

μL = saturated liquid viscosity, g/cm-sec

Re = Reynolds number

Pr = Prandtl number

hi = inside forced convection heat transfer coefficient, W/cm 2-K

ho = nucleate pool boiling convection heat transfer coefficient, W/cm2-K

km = tube wall thermal conductivity, W/cm-K

di = tube inside diameter, cm

do = tube outside diameter, cm

A; = tube inside area, cm2/cm

The LO2 recirculation pump on the PDU is sized to provide sufficient motive energy (BHP)

to force the flow through the complex circuitry of the GSE-STA-VJ piping systems and heat

exchangers. The theoretical work required for the recirculation pump is expressed in terms of the

LO2 volumetric flow rate (Qv

LO2), the total pressure rise (∆PLO2) and pump efficiency (η).

^LO2 ^LO2

BHP = ^!v

(8)

3.82 η

The GN2 compressor is a high-speed centrifugal machine designed to maintain the heat

exchanger ullage pressure constant at 2.4 psia and to reject the boiled-off GN2 inlet saturated vapor

to the atmospheric pressure vent. The basic performance equations for the GN2 compressor are

defined in terms of the dimensionless head ( Ψ ) and flow ( Φ ) coefficients and, the ideal head rise

NASA/TM—2010-216247 19
2nd Stage Heat

Phase Separator 1st Stage Heat Exchanger

Exchan er

Figure 9. Liquid oxygen propellant densification skid equipped with five

major components: the GN2 cryogenic compressor, two LO2-to-LN2 heat

exchangers in series, a phase separator and the LO2 recirculation pump.

(H) done on the gaseous nitrogen based on isentropic, adiabatic compression.

H = zR T1 kk 1 ( (P2/P

)

(")lk

− 1.0) (9)

U2=

π720

and Ψ = Wigc

 then Φ= QvU (10)

2 Am 2

where, the GN2 compressor performance variables have the following definitions:

Am = flow discharge area of the stage, ft 2

T1 = suction temperature, oR

P1 = suction pressure, psia

P2 = discharge pressure, psia

Z = compressibility factor = 0.990

k = specific heat ratio = Cp/Cv = 1.40 at T1 > 200 oR

R = molecular weight constant = 55.171 ft-lb/lbmoR

N = compressor stage speed, rpm

D = impeller diameter = 14.0 inch (constant for all three stages)

H = compressor stage adiabatic head rise, ft

U2 = impeller stage tip speed, ft/sec

gc = gravitational acceleration constant = 32.174 ft/sec 2

With the preceding fundamental relationships, some of the key propellant densification processes

and the basic GSE performance may be either designed or analyzed at an engineering level of

accuracy.

1.4 LO2 Densification Test Objectives

The primary research

objectives were to conduct testing to

demonstrate flight-similar processes

for large scale, in-tank, cryogenic

propellant densification and, to

provide engineering data for the

validation of mathematical

simulations of these processes. In

the approach taken to accomplish

the objectives, the X-33 LO2 STA

tank was used in combination with

the X-33 LO2 propellant

densification unit (figure 9) that

was fabricated by NASA GRC to

explore the effects of different

densified propellant production,

loading and recirculation scenarios

so that the process of densification

NASA/TM—2010-216247 20
for launch vehicles can be further optimized and better understood. The specific test objectives of

the LO2 densification and STA tank thermal stratification experimental program can be

summarized by the following verifications that were performed:

• Evaluate LO2 densifier performance operations including start-up, shutdown and steady

state operations over a range of flow rates and heat exchanger bath pressure operating

conditions.

• Demonstrate densifier performance and verify in-tank thermal stratification characteristics

over two discrete inlet LO2 recirculation mass flow rates, 20 lbm/sec and 30 lbm/sec.

• Vary the STA inlet flow path of LO2 to determine their affects on tank thermal

stratification. The LO2 inlet flow paths tested would be through both bottom lobes, the

instrumented lobe and the un-instrumented lobe.

• Obtain sufficient LO2 PDU performance data including recirculation and tanking

operations to allow validation of mathematical, analytical tank models under development

by GRC and LMMSS [ref. 14].

• Characterize the STA tank environmental heat leak by LN2 and LO2 boil-off testing.

• Demonstrate operational densified propellant production, loading and recirculation

processes using a tank and ground support equipment (GSE) similar to that which would

be used on a flight vehicle with LO2.

2. DENSIFIER HARDWARE TEST ARTICLES

2.1 LO2 Densification Skid (LO2 PDU)

The LO2 densification system was comprised of a cryogenic pump, a two-stage LO2-toLN2 heat exchanger, a phase separator, a three-stage GN2 compressor, and all the necessary

valves, instrumentation, flow elements, piping, tubing, and electrical hardware. All of these

components seen in figure 10 were attached to a skid frame made-up of welded structural steel

sections. By connecting the LO2 densifier to a facility propellant test tank (i.e. the STA), a

closed-loop system was created. The LO2 densifier as designed could be used in any cryogenic

facility that has such a propellant tank, consumables including LO2, LN2, GHe, and GN2,

sufficient electric power, and enough space for the 65’ x 18’ x 11’ skid.

The PDU was designed so that densified LO2 could be provided to a propellant tank at a

maximum flow rate of 30 lbm/sec and a temperature as low as 120 oR. The cryogenic pump first

forces LO2 to flow through the tube bundle of the first stage heat exchanger. Here is where it

would be partially cooled to 142 oR by the atmospheric pressure normal boiling point LN2. Then

the LO2 passed through the tube bundle of the heat exchanger second stage where the cooling

was completed through the use of sub-atmospheric pressure LN2. The three-stage compressor

created the sub-atmospheric pressure condition on the shell-side of the heat exchanger second

stage ullage. The heat exchanger second stage bath could be operated at pressures ranging from

2.5 psia up to 10 psia in order to achieve different temperature levels of sub-cooled LO2. A phase

separator installed upstream of the compressor removed any entrained LN2 droplets from the

NASA/TM—2010-216247 21
Command & Control

PLC Cabinet Interface Cabinet

Power Cabinet

rte_.w

Disconnect +=^

LO2-to-LN2

Heat Exchanger

Stage 1

LO2-to-LN2

Heat Exchanger

Stage 2 _ _

kid

LN2/GN2 Phase

LO2 Pump Separator

VFD

Transformer " - °J \

-^`P GN2 Compressor

480V

Panelboard GN2 Compressor

Splice Exhaust and Surge

Box Control Line

Figure 10. LO2 propellant densification skid equipment layout and overall size of 65’ long x 18’ wide x 11’ tall.

gaseous GN2 entering the first stage of the compressor. Automatic compressor controls with a

PLC were used to regulate the heat exchanger ullage pressure and to provide surge control. The

compressor discharge gas was sent directly to a facility vent stack. A simplified process flow

diagram of the LO2 PDU, shown in figure 11, indicates the typical operating conditions of the rig.

INLET

from Test Tank Test

X316 secl P3dllryL02 ^ TtVVq STAGE L'a2

rEPLENISH 16UR HEAT EXGHANGEF 7.5 "sia

E46

+secl

LN2 BATH ,°R, MAKEUPSias

Figure 11. Simplified process flow diagram of the LO2 PDU.

NASA/TM—2010-216247 22
2.2 LO2 Recirculation Pump

The LO2 recirculation pump was a full emission, horizontal-shaft, closed impeller,

centrifugal type pump with a design head rise of 50 psid at a volumetric flow rate of 190 gpm

and operating speed of 4200 rpm. The pump, shown in figure 12, had the following general

design and construction features: ASME/ANSI class 150 flat-face flange connections;

mechanical foam insulation (SOFI) with a metal protective outer cover; integral support

structure; an accelerometer (0 – 0.5 in/sec) for vibration monitoring; a Variable Frequency Drive

(VFD) controller; 460 VAC three phase, 2-pole induction motor rated for 10.5 HP at 70 Hz and

directly coupled to the pump; and provisions for a GHe purge to the pump seals. All components

but the VFD were mounted on a rigid, stainless steel pump support pallet. The LO2 mass flow

rate was controlled by varying the pump motor speed with the VFD based on a 4 – 20 mA input

control signal from a 3-inch Coriolis mass flow meter (FT-535) measurement. This allowed

adjustment and control of the pump speed to produce any desired head and LO2 flow rate within

the available power range of the variable speed drive. Details of the technical specifications for

the LO2 recirculation pump are seen listed in Table 1.0.

Table 1.0: LO2 recirculation pump design and performance specifications.

Design Parameter

Hydraulic Design Point Data

BNCP-42-000

Manufacturer (OEM) Barber-Nichols Inc.

Fluid Liquid Oxygen

Volumetric flow rate, gpm 190.

Mass flow rate, lbm/sec 33.1

Pump AP, psid 50.

Design speed, rpm 4200.

Inlet temperature, o

R 120.

Suction pressure, psia 60.

Impeller size, inch 4.8

NPSHR, psia 2.8

Specific speed, Ns 91.9

Head coefficient, T 0.41

Flow coefficient, (D 0.09

Efficiency, % 72.1

Shaft power, HP 7.7

Electric Motor Data 72

Power, HP 10.5

Voltage/Current/Phase/Poles 460 / 13. / 3 / 2

Enclosure TEFC

Base frequency, Hz 40

Speed, rpm 4200.

Mechanical Data

Mech. design pressure, psig 150.

Dimensions, in (w x h x l) 29.7 x 24.5 x 36.6

Weight, lbs 450

Inlet / Outlet size, in 3.0 x 1.5

NASA/TM—2010-216247 23
Figure 12. Liquid oxygen centrifugal recirculation pump, drive motorand VFD.

2.3 LO2 Heat Exchangers

The LO2 heat exchanger system was fabricated by PHPK Technologies, Inc. and is

pictured in figure 13. The heat exchanger assembly consisted of two ASME-rated, single-pass,

shell and tube heat exchanger stages arranged in series. LO2 would flow through the tube

bundles while LN2 filled the shell-side baths. Each stage had the following construction features:

ASME/ANSI class 150 raised-face flange process connections; an aluminum tube bundle; a LN2

silicon diode temperature rake; a liquid level capacitance probe and transmitter; an LN2 bath

supply control valve; a low-point LN2 drain; an internal phase separator to remove LN2 droplets

from the GN2 vent gas; temperature and pressure transmitters at the LO2 inlet/outlets; and

redundant temperature transmitters in both the ullage space and LN2 bath.

The first heat

exchanger stage was vented to

atmosphere through an 8 inch

SS line. The vessel was

insulated with two layers of

3.5 inch thick Foam Glass

insulation, with a thin metal

protective outer cover

installed. The second stage

exchanger was a vacuum

jacketed pressure vessel. The

pressure relief system was set

for a nominal 50 psig relief

pressure, even though the

design pressure of the vessels

and coils was 150 psig. The

stage two vent discharged gas

Figure 13. LO2-to-LN2 heat exchanger vessels in series designed to subcool LO2

(top view).

NASA/TM—2010-216247 24
into a 16 inch VJ line leading to the phase separator that was attached to the GN2 compressor

inlet. The second stage heat exchanger contained an internal diffuser/bubbler tied into the GN2

compressors’ surge control recirculation line. When the compressor approached a surge

condition, the compressor recirculated some of the GN2 from its stage 3 discharge, back into the

second stage LN2 bath to increase the GN2 boil-off flow rate into the compressor, and prevent a

surge from occurring. The interconnecting LO2 piping between stages was 3 inch vacuum

jacketed, except for the flanges. All flanges were covered with Foam Glass insulation.

The basic design of the exchanger surface area was a group of parallel pancake style coils

(figure 14) attached to 4 inch supply and return manifolds, submerged in a horizontal tank of

liquid cryogen. The pancake coils were formed in a “D” shape to provide maximum vapor space

above the coils and reduce the vapor velocity at the liquid-gas interface as much as possible to

give good separation and minimize entrainment. The manifolds, which extended the full length

of the inner vessel, distributed the heat load uniformly throughout the liquid bath. All coils were

formed from extruded “D” shaped 3003 aluminum tubing. The tubing was 1 inch OD net with

1/8 inch thick walls. The heat exchanger tube bundles in Stages 1 and 2 comprised 72 parallel Dshape coils with each pass having lengths of 64 feet and 96 feet, respectively. Table 2.0 presents

some of the pertinent design and performance requirements for each of the heat exchanger stages.

Table 2.0: LO2 heat exchanger system design and performance data.

Design Parameter 1

st Stage LO2 2nd Stage LO2

Tube Side

Inlet flow rate, lbm/sec 30. 30.

Inlet temperature, oR 168. 142.

Inlet pressure, psia 110 100

Outlet temperature, oR 142. 120.

Max. allowable AP, psid 7.5 7.5

Total tube length, ft 4608 6912

No. of parallel coils 72 72

Surface area, ft2 905 1357

Mech. design pressure, psig 150. 150.

Shell Side

Bath temperature, oR 139. 117.

Bath pressure, psia 14.6 2.5

GN2 vent flow rate, lbm/sec 3.7 3.3

Max.GN2 surge (270 oR) lbm/sec – 1.8

Surface area, ft2 1372. 2057.

Volume (total), gal 3630 3460

Volume (operating), gal 3230 2540

Inner vessel OD, inch 78. 78.

Mech. design pressure, psig 150. 150.

Insulation Foam Glass VJ

NASA/TM—2010-216247 25
Figure 15. Three stage GN2 compressor system.

Figure 14. LO2 heat exchanger pancake coil D-shaped tube bundle assembly.

2.4 GN2 Compressor System

The GN2 compressor system, fabricated by Barber Nichols Inc., was a three-stage, full

emission, centrifugal unit designed to control and maintain the heat exchanger second stage

ullage pressure between 2.5 psia and 10.0 psia. The compressor system (figure 15) itself was a

completely self-contained assembly that came with all of the necessary auxiliaries. These

included a motor cooling system, instrumentation, VFD motor drives and a PLC-based controller

system. At the nominal inlet design conditions of 2.4 psia at 118 oR, the compressor was

designed to pump up to 3.3 lbm/sec of GN2 from the heat exchanger second stage, and compress

it to 15.6 psia at 251 oR. The compressor system design had the following general mechanical

and construction features: a vacuum -jacketed, LN2 phase separator vessel; ASME/ANSI class

150 raised-face process flange connections; a closed-loop water propylene glycol cooling system

for the compressor motors; a perlite insulation filled enclosure vessel; a GHe pressure purge for

the compressor enclosure; Motor Cooling • -T 77,

annubar flow meters in the I ^ r _ System

Stage 1 Motor ' Compressor lki

exhaust and surge piping; a 4 Compressor— ^^ ;- Enclosure Of

inch surge bypass control ... 

Outlet f

Yk valve; silicon diode

temperature sensors; pressure -

transducers; and a PLC device.

Each of the three

compressor stages (figure 16)

had near identical components

that included VFD controlled

460 VAC three phase, 4-pole

electric inverter duty motors

(70 HP) directly mounted to

and hermetically sealed from

NASA/TM—2010-216247 26
the compressor housing

(i.e. this means there were

no rotating seals), an

accelerometer for vibration

health monitoring, motor

winding thermocouples,

and interstage pressure and

temperature transmitters.

The pressure ratio across

each stage was balanced by

design such that it allowed

PLC control or adjustment

of the compressor speed to

produce any desired suction

pressure within the available power operating range of

the drive. The compressor stage subassemblies including

electric motors, VFD enclosures, and all related piping

were directly supported by a horizontal cylindrical

carbon steel enclosed vessel. In addition, all

interconnecting piping in-between the stages were

routed and supported inside of the compressor

enclosure. At the inlet of the GN2 compressor, a vaporliquid phase separator (figure 17) was installed to

maintain a gas quality range in-between 98 and 100% at

the compressor inlet. The phase separator was a vertical

mounted cylindrical VJ tank with hemispherical endcaps and was supported by three legs that were welded

to the bottom.

Figure 16. GN2 compressor system stage number 3 – top and front view.

There were two major control loops in the GN2 8” GN2 Inlet '.;^

compressor system. These included suction pressure Figure 17. The GN2 phase separator final assembly.

control, achieved by varying stage speeds and, one loop

to prevent the compressor from going into surge, both of which used active PID software control.

To avoid compressor surge at low GN2 flow rates, a GN2 recirculation line as part of a surge

avoidance system was utilized. During compressor operation, if the compressor PLC determined

that surge was imminent via flow coefficient ( 0) monitoring, the gas bypass recirculation control

valve opened. This would happen when the mass flow rate falls below the design control setpoint (Φsp = 0.18), in which case the valve positioned itself to maintain the flow coefficient at or

above the predetermined surge avoidance line where (D equals 0.18. The recirculated flow was

then injected back into the heat exchanger second stage LN2 bath, through an 8 inch perforated

diffuser/bubbler pipe, to increase the GN2 boil-off flow rate to the compressor inlet and prevent

the compressor surge instability. If in the event that the first stage inlet (D would fall below 0.12

then an automatic surge shut-down would be initiated by the PLC. Table 3.0 summarizes the

GN2 compressor stage design point characteristics.

NASA/TM—2010-216247 27
Table 3.0: GN2 compressor design point conditions.

Stage No. → 1 2 3

Inlet temperature, o

R 118. 163. 208.

Inlet pressure, psia 2.40 5.44 9.73

Discharge temperature, o

R 161. 206. 251.

Discharge pressure, psia 5.64 9.93 15.6

Mass flow rate, lb m/sec 3.3 3.3 3.3

Head rise, ft 6224 5835 5742

Pressure ratio 2.35 1.82 1.60

Stage pressure rise, psid 3.24 4.49 5.87

Speed, rpm 10,060 9,840 9,670

Impeller diameter, in 14.0 14.0 14.0

Tip speed, ft/sec 615. 601. 591.

Specific speed, Ns 112.5 90.2 75.8

Head coefficient, T 0.53 0.52 0.53

Flow coefficient, (D 0.33 0.30 0.28

Shaft power, hp 49.4 49.0 49.0

Stage efficiency, % 75.7 71.4 70.4

Motor nameplate hp @ max. N =

11,500 rpm, 400 Hz

70. 70. 70.

Stage outlet area, Am, ft20.1784 0.1480 0.1264

Mech. design pressure, psig 50. 50. 50.

2.5 VJ and Process Piping

All process piping (figure 18) on the LO2 densifier was designed, fabricated and tested in

accordance with the ASME B31.3 Process Piping code requirements. Both the inner line and

vacuum jackets were fabricated from Schedule 5 or Schedule 10 stainless steel, ASTM A312,

Type 304/304L. With the exception of process flanges and compressor exhaust piping, all

cryogenic piping and components not previously mentioned, were vacuum jacketed with a design

pressure rating of 150 psig. 3” LO2 VJ

The flanges and compressor - - -

exhaust piping were non-VJ

but instead were covered by

removable mechanical Foam '', y

Glass insulation. The LO2

piping and LO2 components

were each cleaned to meet

the oxygen cleanliness

specification requirements 2” L N2 Drain

defined by MSFC-SPEC164B, Level IIIA for nonr 8”SS GN2 Vent ':•'= volatile residue (NVR) and -

particulate matter.

Figure 18. LO2 densifier process piping, GN2 vents, LO2 VJ lines, and LN2 VJ system.

NASA/TM—2010-216247 28
2.6 PDU Utility Gas Systems

The LO2 densifier was designed with both utility GN2 and GHe support systems. These

systems were essentially, manually operated pressure reduction stations consisting of hand

isolation valves, hand loaded regulators, relief valves, filters, pressure gages, pressure switches,

and pressure transmitters. The GHe system on the skid reduced the facility supply pressure,

typically at 500 psig, to those pressure levels required for purging hardware and piping from 25

to 100 psig. The GN2 utility system reduced the test facility delivery pressure from 500 psig to

three levels required for low-pressure purging the electrical enclosures (10 psig) and purging the

LN2 piping (40 psig) on the LO2 densifier, in addition to the 125 psig GN2 for actuation of all

the remote operated valves on the densifier.

2.7 LO2 Densifier Electrical Systems

The densifier electrical system consisted of four major parts: power; control and

instrumentation; fail safe shutdown; and operator interface and data logging. Each of the parts,

with the exception of operator interface and data logging, were physically located on the densifier

skid so that the densifier function was self-contained and relatively easily transported as shown

by the PDU skid being moved in figure 19. The facility interface to each of these systems was

minimized in order to simplify the integration of the densifier at its test destination. The

recommended electrical feeder size from the facility was 500 KVA of power to run the densifier.

The entire LO2 densifier skid was classified electrically as a Class 1, Division 2 Group D

hazardous area per the National Electric Code. The electrical area hazard requirement of the LO2

rig was driven by the initial integration plans of the PDU with the X-33 launch facility at

Edwards Air Force Base.

The LO2 densifier skid . .

required a single 460 VAC three

phase feed conductor from the

test facility. Once tied into the i

skid, the power was distributed

through a panel board to three

^- ^m 

major on-skid feeders to supply - ^ ' ' k -

the individual densifier loads.

K IM". 

The three main power feeders _ 

^,

were directed to the compressor j^^,

system motors, the LO2 pump, -

and the densifier

instrumentation and controls.

Each feeder was protected at the

panel board by a circuit breaker. Figure 19. The LO2 densifier is self-contained and modular for ease of

A single 460 VAC power feed transportability as illustrated by this move at the NASA GRC in 1999.

was used to tie into the Barber-Nichols compressor motor system. This feeder was tapped and

fused for each individual motor/VFD unit. To reduce potential VFD induced harmonics

generated from the three 70 hp motors, line reactors and filters were used at the VFD power

inputs. The LO2 pump feeder supplied a fuse protected 10.5 hp motor/VFD unit. A line reactor

NASA/TM—2010-216247 29
and filter was also used here to reduce the harmonics induced by the pump VFD. The third major

electrical feeder on the densifier skid was tied into a 15 KVA transformer to supply 120/208V

power for instrumentation and control. The transformer was a filtered-shielded type to reduce AC

transients and noise from the large motors connected nearby. With these devices, data

transmission signals were un-affected by the AC drives during motor operation.

2.8 Skid Instrumentation and Controls

The LO2 densifier skid was fully equipped with all of the necessary hardware to perform

data acquisition and control with minimal interfacing and outside intervention. A skid-mounted

Programmable Logic Controller (PLC) communicated with locally mounted sensors and effectors

on the skid for densifier operation. The PLC had dual functions for basic process control and data

acquisition. The PLC system controlled the densifier propellant mass flow rate, heat exchanger

bath level, control valves and safety-health monitoring systems. Sensors consisted of those

elements for pressure, temperature, flow, speed, vibration, level, and position. Effectors included

control valves, isolation valves, and the VFD motor on the LO2 pump.

The PLC controlled motorized, air-actuated, and solenoid valves in addition to

performing interlocking of critical safety systems. The PLC also performed sequenced startup

and shutdown of certain systems. Emergency shutdown circuitry was hardwired and operated

independently of the PLC by removing power from the select devices. A PLC scan-loss would

generate an emergency shutdown while an Input/Output module failure would generate an alarm.

A separate embedded control system (slave controller) was installed on the GN2 compressor

assembly to allow the control of that process to remain autonomous. Although the compressor

PLC system was independent from the skid, all of its data and control parameters were accessible

to the densifier operators. At the skid, a single control-data bus fiber optic cable linked the LO2

densifier system to the facility control room.

The LO2 PDU had five basic types of research and control instrumentation. Temperature

sensors used on the PDU system were predominantly silicone diode (SiD) type probes made by

LakeShore Cryotronics with a typical accuracy of +/- 0.5 oR. A total of twenty-six installed SiDs

provided temperature data for the LO2 recirculation system, heat exchangers, LN2 subsystem and

GN2 compressor systems. Twenty-two capacitance type pressure transducers made by Setra and

Rosemount were installed on the PDU to indicate LO2, LN2 and GN2 system pressures ranging

from less than 5 psia to over 50 psia. Pressure measurements had an accuracy of ± 0.11% FS. Three

Micro Motion Coriolis mass flow meters accurate to ± 0.15% FS and located on the liquid cryogen

fluid transfer systems provided data for LN2 heat exchanger feed, LO2 recirculation and LO2 tank

make-up flow rates. Capacitance type liquid level sensor elements by American Magnetics were

installed inside each heat exchanger stage for bath level indication to ± 0.1 % accuracy.

Differential pressure transducers sensing AP for each of the two Deiterich Standard

annubar flow meters provided information for calculating compressor mass flow rates including

discharge and surge bypass flow at ± 0.1% accuracy. There were also AP transducers installed

across each of the three process filters to verify whether a filter became fouled or clogged. The

VFD’s themselves provided feedback and data on motor run parameters like voltage, current,

speed and torque. Piezoelectric quartz accelerometers were installed on each skid located VFD

NASA/TM—2010-216247 30
pump and compressor motors to monitor abnormal vibration conditions (0.0 – 0.5 in/sec) in the

event of a bearing problem. Three Type T thermocouples, each bonded to the stator inside each

of these VFD motors, allowed continuous health monitoring of motor operating temperatures that

normally were designed to run at about 200 – 250 oF. The LO2 PDU test article instrumentation

listing and details are provided in Appendix A.

2.9 Densifier Operator Interface and Data Logging

The LO2 PDU control room was located in a protected environment and remote from the

hazardous densification area. Here, a video graphics control station (figure 20) provided operator

interface to the PLC via a Modbus Plus network. At this site the operator had access to the

densifier process through the control panel which consisted of a rack-mounted industrial PC

computer, touch-screen displays, and a hardwired interface consisting of an emergency stop

button, reset, and master key switch. Through the touch-screens the operator could manually

command the process or issue high level script commands to execute a sequence of events. In all

cases the PLC, mounted locally at the skid, executed the commands and provided closed-loop

process control.

A variety of touch- ^` ^_ E-Stop

screens could be accessed to I - ^'

allow the operator as fine a 04 Touch Screen {,

p Display

level of detail as necessary to T^_ -^^^^ n n^

perform the desired function. Operator

Typical operations were Stations

performed from one or two

window screens to minimize a , r *_

effort and confusion. In case

of alarm conditions the PC / Data

operator interface utilized an Acquisition

annunciator function which ;^-!J

required the operator to

perform any necessary actions Figure 20. Operator interface and control console for LO2 densifier. to restore the process. Since

the PLC always maintained control, it could shut down the densification process if the operator

did not respond. Conventional push button operators were provided for emergency shutdowns.

First-out annunciation through the PLC provided visual and audible indication of alarm and

shutdown conditions. Data logging was accomplished at the operator workstation using the PC

and its mass storage capabilities. A continuous one scan per second log of all instrumentation

data channels to the densifier control and data acquisition systems, as well as operator commands

issued, were stored on a 4.3 GB hard disk drive.

NASA/TM—2010-216247 31
3. STA TEST ARTICLE – LO2 PROPELLANT TANK

3.1 LO2 STA Tank Description

The next most significant test article of the LO2 PDU test program was a propellant tank

designed and built by the Lockheed Martin Michoud Space Systems (LMMSS) group. It was the

structural test article (STA) for the X-33 RLV liquid oxygen tank. The LO2 STA tank was a

critical item of the X-33 Vehicle: it was to provide storage of the oxidizer for the X-33 Linear

Aerospike Main Engines; and its structure would form part of the main load carrying path of the

vehicle. The Liquid Oxygen Tank would be used to provide oxygen propellants to the X-33 main

propulsion system and provide the vehicle’s primary structure for the forward landing gear and

the aeroshell support.

The STA tank employed during the GRC test was identical to the tank that would have

flown on the X-33 vehicle and the tank was designed and built specifically for simulated ground

load testing that was previously conducted at the MSFC. The test tank article was a dual-lobe,

conformal design, constructed of Al 2219 aluminum. Empty the tank weighed approximately

6,900 lbm and when filled with densified LO2, the combined tank and propellant mass exceeded

203,000 pounds. Sitting in the

vertical position, as it was for

the S40 densification test, the

STA was nearly 27 ft. tall, 18 • • '

ft. long, and 10 ft. wide. The :k '

propellant tank, shown being I •

erected in the vertical position

at the GRC S40 test facility in 4^ S S

1{I• / 6 4'

figure 21, required a two-crane ` r '•, • fib lifting procedure, was mounted •^ ;— ,

on a structural support platform :1^ •^^ S. -°^ :tip ^ '^ 9' '^ •^

and was fixtured by a series of

_ ^►

cylindrical steel struts located

around the two barrel sections

of the STA’s base.

Figure 21. Installation of the STA Tank at the GRC South Forty Test Facility.

3.2 STA Mechanical Design

The LO2 STA tank was described as a dual-lobe, axisymmetric, flight-weight prototype

tank, designed and constructed of Type 2219 aluminum with a nominal capacity of 20,000

gallons. The tank accommodated two aft tank outlet fittings for the LO2 fill and drain system and

three outlet fittings forward for the LO2 syphon outlet, vent/relief valve, and ullage

pressurization line. The tank was capable of being purged and pressurized with either helium or

nitrogen gas through a forward opening. Purge flow into the STA could be achieved through

either the fill, the syphon, and drain line and/or the pressurization line. Vent gas flow could exit

the tank via the fill, syphon and drain line and/or the 3 inch vent line. A CATIA diagram of the

STA tank in the upright horizontal position without applied insulation is shown in figure 22.

NASA/TM—2010-216247 32
Figure 22. CATIA general arrangement model of the LO2 STA tank densification test article.

The STA geometric volume at ambient pressure and temperature was 2,596 ft 3 or 19,420

gallons. The normal fill and operating volume of the STA was 18,860 gallons for LO2 densifier

testing. The tank had a maximum design and operating pressure of 37.0 psig. The minimum

operating pressure was not less than 0.0 psig as the STA was not designed for the stresses of

vacuum. The design relief valve set pressure on STA was 25.0 psig based on a hazards analysis

and safety requirements since the tank was not an ASME rated pressure vessel. The tank was

designed for a maximum bottom pressure of 60.0 psig in the aft domes when filled and

pressurized with cryogen. For the S40 testing, the STA tank normal operating pressures would

range from 28 to 32 psia, and were nominally run at 30 psia ullage pressure during densifier

closed-loop recirculation testing. Appendix B provides the STA tanking-detanking table with

information regarding fill height, percent liquid and ullage volume, diode sensor locations and

theoretical densified propellant mass loads for both LN2 and LO2.

3.3 STA Insulation

The STA tank had a Reusable Cryogenic Insulation (RCI) protection system bonded to

the outer surface. Insulation design was based on spray-on foam insulation (SOFI) with thermal

characteristics much like that used for the Space Shuttle External Tank. The SOFI was sized to

meet the specified X-33 propellant delivery requirements, to maintain propellant quality during

all cryogenic tanking operations, and for control of thermal stresses associated with extreme

temperature gradients. A nominal baseline thickness of 1.0 inch of RCI was applied to the STA

tank exterior cryogenic surfaces. Additional thickness was applied to areas that would experience

NASA/TM—2010-216247 33
localized heating. Another RCI design requirement was to preclude air condensation external to

cryogenic systems that could result in hazards to personnel, hardware, or cause operational

anomalies during ground testing. The predicted heat leak value estimated by LMMSS designers

was 130,600 Btu/hr with the tank filled with NBP LO2 at a 2.9 percent ullage volume. Based on

the average STA tank surface area of 1,058 ft2, the as-designed analytical heat flux was 123

Btu/hr-ft2.

3.4 STA Fluid Interfaces

LO STA L0261 

Tank pressurization interfaces FWO.Cove Plate

utilized LMMSS hardware designed to 4L.- L02-62 000 000

comply with the interface requirements of .` GH 01 00o 000

the GRC LO2 Densification Unit and the

S40 Facility Control System. A forward o

cover plate was equipped with an internal

3.0"Relief!

siphon tube (figure 23) to support the Outlet 1 0" Pressurization

LO2 densification recirculation P0^

4 0" 4.0" Deneifi er

experiments. A 1.0 inch straight pipe-line Siphon Tube

Recirculation Line

on the forward plate was provided for

GHe/GN2 inlet gas pressurization. A 3.0

inch straight pipe line was also installed

here for pressure venting and relief. The

LO2 tank aft feedline interface also

^^

utilized LMMSS designed hardware. The

twin aft feedline cover plates were

designed to comply with the interface Figure 23. STA tank forward cover plate fluid interfaces.

needs of the densification test. The aft

cover plates (figure 24) each featured an internal splash plate to support fluid dispersion during

the LO2 densification experiments. Connections to the densifier inlet and recirculation lines

utilized 4.0 inch PHPK PBA-40 vacuum -jacketed male and female bayonet type fittings that

interfaced with the densifier inlet VJ hoses. Here on the STA side, two 4.0 inch VJ bayonet male

fittings were provided to interface with the densifier fill and drain lines.

Figure 24. STA tank 4” VJ fill and drain line Aft cover plate interface with S40 test site.

NASA/TM—2010-216247 34
3.5 STA Structural Support Platform

The STA tank was mounted in the vertical upright position on the Test Support Platform

(TSP) also identified as the “T153 Tool”. The tank was structurally fixtured to the TSP with

rack-and-pinion strut pedestals welded to the T153 base and connected to steel cylindrical strut

members. There were twenty-four (24) original struts attached to the Test Support Platform.

These length-wise adjustable struts were the main static and dynamic load bearing members to

transmit forces from the STA to the support platform. During cryogenic LN2/LO2 testing with

STA, only 7 of the 24 struts were installed to support the combined loads. This change in

philosophy regarding the strut design was based on extensive thermal stress analyses conducted

by LMMSS. Their results indicated that the STA was “structurally over-constrained” with the

original 24-strut arrangement as thermal stresses develop at cryogenic temperatures that were

considered in the operation.

A significant amount of time and effort was expended in the field to “balance” the STA

on the seven struts at S40. These alignment adjustments were based on field transit

measurements and strain gage data before a full tanking test could safely be performed. The T153

platform was positioned over a massive 42 ft x 30 ft x 4 ft concrete foundation, serving as the

primary structural support for the 100 ton plus LO2 STA Tank when fully loaded with DLO2. An

access platform

surrounding the STA

was constructed of

scaffolding. The scaffold

structure was designed

to support operations

personnel as well as the

required forward and aft

interface piping and

instrumentation loads

generated by the

cryogenic test profiles.

Figure 25 provides a

generalized view and

orientation of STA on

the TSP with scaffolding

in-place. Figure 25. STA tank structural support platform (T153) and access scaffold at S40.

3.6 STA Tank Internal Instrumentation

The STA tank was equipped with internal liquid level and temperature data measurement

capability (figure 26) for the LO2 PDU loading and recirculation experiments. The STA

instrumentation and data collected was via the S40 test facility data acquisition system. The STA

specific instrumentation transducers consisted of the following: internal STA vertical and lateral

silicon diodes; LO2 inlet and outlet temperatures at the boundaries of STA; tank ullage pressure;

STA liquid level; and LO2 mass flow rates which included both tank inlet and STA make-up

flow via the PDUs Coriolis mass flow meters.

NASA/TM—2010-216247 35
Figure 26. STA internal instrumentation mounting arrangement – horizontal view.

The capacitance liquid level probe, manufactured by B.F. Goodrich, was located internal

to STA and was positioned on the right lobe. The probe was used to monitor and control

propellant liquid levels within the STA. The design utilized one 32 inch long capacitance level

probe sensor positioned 13.5 inches below the forward cover plate. Temperature transmitters

included forty (40) silicon diodes (SiD) mounted on a rake inside the left lobe or “instrumented

lobe” of STA.

The instrumented rake assembly consisted of an aluminum structure, silicon diode

temperature sensors and associated wiring. The rake assembly was located approximately along

the centerline axis of the left hand lobe of the STA. The SiD temperature sensors used on the

rake assemblies were sensors manufactured by Lakeshore Cryotronics, model DT470-SC-11A,

with an accuracy of +/- 0.5 oR over an operating temperature range of 3.6 – 180 oR. Table 4.0

shows measurement requirements and internal instrumentation specific to STA thermal

stratification test run data output. Vertical and laterally mounted silicon diodes were used to

allow characterization of STA propellant temperature gradients that developed during thermal

stratification and closed-loop recirculation testing.

Table 4.0 : STA test article internal instrumentation.

ID Number Measurement Type X-Coord. / Location † Left Right Total

Lobe Lobe Sensors

LL1 Liquid Level Capacitance Probe Fwd Cone Strongback - 1 1

PVT1 - PVT25 Temperature Silicon Diode Sensor Vertical Rake – 14 to 25 - 25

302 inch Level

PLT1 - PLT5 Temperature Silicon Diode Sensor Lateral Rake - 98 inch 5 - 5

Level

PLT6 - PLT10 Temperature Silicon Diode Sensor Lateral Rake - 160 inch 5 - 5

Level

PLT11 - PLT15 Temperature Silicon Diode Sensor Lateral Rake - 218 inch 5 - 5

Level

Total — — — 40 1 41

Note: † The X coordinate designation for the STA is from top at X = 0 inch to the tank bottom at X = 306 inch.

NASA/TM—2010-216247 36
4. SOUTH FORTY TEST FACILITY

4.1 General Facility Description

The main South Forty (S40) test facility and integrated hardware – designed, acquired and

built-up over the course of more than one-year’s time for the LO2 PDU test series – consisted of

the following nine major facility subsystems:

• LN2 Facility Dewar (N-71, 13,000 gallon)

• LO2 Facility Dewar (N-83, 28,000 gallon)

• GN2 Vaporizer w/LN2 Supply Dewar (N-43, 4,000 gallon)

• GN2 High-Pressure Bottle Farm (2400 psig, 221,000 scf, total capacity)

• GHe High-Pressure Tuber Stations (2400 psig, 70,000 scf, qty. two)

• LO2/LN2 Vacuum-Jacketed Piping

• Pressurization, Vent and Safety Relief Systems

• S40 Facility Instrumentation Systems

• Building 100 Control Room

The following sections of this report present brief technical descriptions of each of these

common elements including how they were integrated as a facility. Figure 27 shows some of the

major subsystems and features associated with the S40 densification test site at GRC, which

required an overall foot-print area size of approximately 180 ft. by 140 ft.

-'• w.^,^^...• !^ N-83 N-71

q r: ^: .t, ,^', •^ *=" . Dewar ^• , _ Dewar

^'' AS ^. II. •. •^• a ^.

• r^O^^G. ^i^Y^[ll''• `^sir'I+r^^^ s• s^ • ^7!^•.

GHe .: ,^^ . • . ,^

Tuber

Stations

X33

STA

LO2

Densif ier

Figure 27. GRC South Forty (S40) LO2 propellant den sification test facility.

NASA/TM—2010-216247 37
4.2 Liquid Nitrogen System – Dewar N-71

Liquid Nitrogen (LN2) was used during facility LN2 cold shock procedures and densifier

checkout and performance testing. Two different facility dewars would be used in LN2 service.

Dewar N-83 supplied LN2 for the LN2 densification checkout tests of the LO2 Propellant

Densifier Unit (PDU). Dewar N-71 was used to supply LN2 for the heat exchangers on the LO2

PDU during both LN2 and LO2 testing. Note that dewar N-83 also acted as the principal LO2

supply dewar for LO2 testing of the LO2 PDU.

Dewar N-71 was a a ^. a © _

13,000 gallon capacity liquid '^ p^,;,1

nitrogen stationary dewar ^, I

which was installed at the S40 a ►^' ^^ ^`

area specifically for these tests. ^` ^, ! t ''.

The dewar, with the working

end shown in figure 28, had a

double-wall vacuum jacketed

construction that was backfilled with perlite insulation. '• ' ^ ^ ^^ ^: "

working pressure for N-71 was

The maximum allowable R ''y

,^

89 psig, however the dewars’

primary relief valve was set at

50 psig. During PDU testing,

N-71 was filled from the Figure 28. Working end of 13,000 gal. liquid nitrogen dewar N-71 at South Forty.

supplier’s mobile dewars with

a fill station located at the southern most corner of the storage vessel. Pressurization of this

dewar was accomplished using an external GN2 source for ullage pressure control, operated at

nominally 30 psig during PDU testing. Dewar N-71 was equipped with a remote operated vent

valve, a back-pressure control valve, pressure safety relief devices, an LN2 fill/drain control

valve and the operator fill station. Instrumentation and controls for this dewar included silicon

diodes for liquid and ullage temperature measurement, a AP level indicator gage and a pressure

transducer for remote ullage pressure indication and control.

4.3 Liquid Oxygen System – Dewar N-83

Dewar N-83 was a 28,000 gallon capacity LO2 storage vessel designed to supply LO2 for

testing of the LO2 PDU as well as LN2 during checkout testing of the densifier with LN2. The

dewar (figure 29) was modified to handle both LN2 and LO2 cyrogenic fluids and N-83 plans

would be to warm, purge and inert the dewar before loading the dewar with different cyrogenic

fluids during the transition. Pressure in N-83 was controlled at approximately 60 psig during a

PDU test. Approximately 13,000 to 25,000 gallons of cryogenic fluid was expelled from N-83

while in a test mode. External pressurization of the dewar was by a GN2 pressurant gas supply

line that was regulated by remote control valve XO-8315. This vacuum jacketed stationary dewar

had a maximum operating pressure below 80 psig.

NASA/TM—2010-216247 38
Early on in facility build-up, the

dewar was cleaned in accordance with

MSFC Spec 164B for liquid oxygen service.

Remote operated valves installed on N-83

included liquid discharge, vapor vent, and

gaseous nitrogen pressurization valves.

Following each PDU test the sub-cooled

cryogens, either LN2 or LO2, were

reconditioned (i.e. warmed back up to NBP)

and then were back-transferred from the

STA tank to N-83. Vacuum jacketed piping

on N-83 was installed to permit the dewar to

be filled from the government supplier’s

mobile dewar at a remote fill station located

to the north of N-83 near the site entrance.

Instrumentation and controls for N-83

consisted of silicon diodes for liquid and

ullage temperature measurement, a AP level

indicator gage and a pressure transducer for

remote ullage pressure indication and

control. Figure 29. Liquid oxygen supply dewar N-83

.during cryogenic flow testing.

4.4 Gaseous Nitrogen System

The Propellant Densification test site in the Upper South Forty area made use of the

old Rocket Engine Test Facility (RETF) 4000 psig GN2 bottle farm (figure 30) that supplied the

nitrogen needed for the testing. A portable LN2 vaporizer system consisting of a high-pressure

pump, LN2 vaporizer coils, air fan, automatic controls and a 4,000 gallon LN2 Supply Dewar (N43) was installed down at RETF

adjacent to the C-Stand. This kWh

equipment was used to continuously ^ Six 90 ft3

maintain pressure in the GN2 bottle

cri2 bottles

ft3

- -1 bo N2 farm at approximately 2400 psig. An

existing 2 inch pipeline from the 4000 ►vi ^^^

psig bottle farm to the upper South

Forty fed nitrogen gas to the boundary

of the densifier test site. Gaseous 183 ft3

nitrogen was used for purging and GN2

? r bottle

pressurization during the liquid 1

nitrogen and liquid oxygen tests of the

LO2 PDU. This arrangement was

chosen due to the very high nitrogen

usage requirements. The total capacity Figure 30. South Forty high pressure GN2 storage system rated at 2400 psig

of the eight high pressure cylinder. and 300,000 scf GN2 capacity.

bottles was 1283 cu.ft (water volume). When fully pressurized, the system provided a reserve of

nearly 300,000 standard cubic foot (scf) of gaseous nitrogen. All gaseous nitrogen flowing from

NASA/TM—2010-216247 39
the RETF bottle farm was initially regulated down to 450 psig. Nitrogen then fed into a lowpressure GN2 distribution system and was routed to the various points-of-use including valve

actuators, the LO2 PDU, facility purge points and pressurization for N-71, N-83, and the STA

tank. A new 2 inch gaseous nitrogen XXS stainless steel line was extended, from the S40 ridge

where the line from RETF ended, and was run inside a trench before terminating at the facility

GN2 pressure reduction station. The XXS nomenclature is a standard designation for an extra

heavy wall pipe thickness which in this case was 0.436 inches for the 2 inch GN2 line.

4.5 Gaseous Helium System

The gaseous helium system (figure 31) for the propellant densification testing consisted

of two GHe tuber stations installed at the S40 test site. Each supply station was a NASA tuber

trailer with a 70,000 scf rated capacity per tuber. This system provided up to 140,000 scf of GHe

maximum reserve. The trailers had an initial charge pressure of 3100 psig. Each tuber was

connected to a common new 1.5 inch SS piping manifold that was routed to a single GHe

pressure reduction and valve station. Here the GHe pressure was regulated down to 450 psig

before the gas entered the low-pressure distribution and piping system. Gaseous helium was

provided at 450 psig to the STA pressurization system and to the LO2 PDU interface. Other

helium uses at the S40 test site included purges located at the STA vent and various facility

purges to VJ transfer lines.

Low Pressure Side

High Pressure Side

Densifier

HELIUM Tuber#1 500

psig

70,000 scf STA

Press’n

33

psig

3100 psig 450

psig STA Vent

30 Purge

HELIUM Tuber # 2 psig

70,000 scf

VJ Lines

Purge

LO2 PD Testing Helium Usage 22,800 - 25,800 scf per Run Day

110

H-56

psig I Press’ n

I GN2

100 System

psig Back-Up

Figure 31. Gaseous helium system schematic for facility LO2 densification test article.

4.6 Facility Vacuum Jacketed Piping

The S40 facility vacuum jacketed (VJ) piping system consisted of ten prefabricated piping

spool sections of sizes 2 , 3, and 4 inch diameters. These VJ lines were used to interconnect the

LO2 densifier with the dewars and the STA tank. The densifier/STA test articles and a simplified

facility flow schematic of cryogenic fluid systems is seen in figure 32. Specifically the VJ piping

system design accomplished the following:

NASA/TM—2010-216247 40
• For LO2 PDU testing, the vacuum -jacketed piping layout interconnected the LO2 densifier

skid with the STA tank, and dewars N-71 and N-83.

• Critical fluid temperature and pressure sensors at the boundaries of the skid and STA were

incorporated into the facility VJ piping systems.

• The VJ piping provided an easy bypass drain system from STA back to N-83.

• Miscellaneous foam insulated piping spools between dewars N-71, N-83, and the LO2 PDU

facilitated other operations like post-test LN2 draining of the heat exchangers.

Figure 32. Densification process facility schematic for LO2 and LN2 systems.

Although much of the VJ piping for the S40 test was built and reconfigured from existing

facility lines, the piping system had the following seven general design features: (1) the inner and

outer lines of the VJ piping spools were constructed of Schedule 5 type 304 seamless or welded SS

pipe per ANSI Process Piping Code B31.3; (2) the inner line design pressure was 150 psig at 530

oR while normal design operating temperature was 120 oR – 170 oR; (3) the inner line was wrapped

with fifteen layers of aluminized mylar insulation and supplied with a chemical gettering system;

(4) the vacuum annulus had a maximum acceptable vacuum level of 30 microns of Hg; (5) each

spool assembly was fabricated with a seal-off and relief valve, a bellows sealed isolation valve and

a thermocouple vacuum gauge tube; (6) mechanical bayonet field joints with warm O-ring seals and

V-band connections were installed at the end of each spool piece to allow ease of field assembly

and maintenance; and (7) expansion joints and VJ piping supports were located to allow for the

thermal movement and flexibility of the finished piping system.

NASA/TM—2010-216247 41
4.7 S40 Facility Test Article Vents

There were two principal facility test article vents installed at the S40 area: the

densification unit 12 inch atmospheric vent for compressor exhaust; and the STA vent/valve

package system. The design basis for the compressor discharge facility vent was defined from

requirements for another densification system built at the GRC. This sister unit was an 8 lbm/sec

LH2 densifier with a four stage GH2 compressor and, this PDU too was also sized for the X-33.

The gaseous hydrogen compressor on the LH2 densifier was designed to vent up to 1.1

lbm/sec of GH2 to the atmosphere. In order to safely disperse this very high gH2 flow rate by a

non-flared type of system and stay within the allowable pressure drop margin (< 1.0 psid) of the

compressor, a 12 inch vent system was designed and installed. This newly fabricated vent line at

the S40 tied the exhaust of the compressor into a 12 inch Schedule 5 main trunk-line. The main

vent line extended 210 feet horizontally and east away from the PDU skid. The line intersected

with a 12 inch tee-branch and was split into five 6 inch vertical pipes that were terminated with a

tee to further divert the flow both left and right. The calculated pressure drop for this system

venting GH2 was 0.8 psid maximum. A thermocouple installed at each 6 inch vent outlet would

allow monitoring gas temperature

R 8” Sch 5 SS in the event of an accidental GH2 Vapor vent

: 6” Vent Stacks light-off ignited by static electrical 210 ft horiz. run!; • from PDU

discharge. During LO2 PDU

r

testing, this same 12 inch facility '

I [w 2 GN2 flow

J'.

vent system (figure 33) was I ^ ^°^^^ ^ ;,

connected to the GN2 three-stage 8” Exp. Joint

compressor exhaust to allow safe

dumping of GN2 away from the

densifier skid. This safety feature

was designed into the system in GN2 Out

the likelihood that operators 12” Sch 5 SS

needed to be present near the LO2 Thrust Anchor

unit while the GN2 compressor j

was running. Figure 33. South-Forty facility GN2 compressor exhaust vent system

The STA vent and valve package assembly was designed to prevent over-pressure of the

STA as well as control tank ullage back-pressure by vent valve operation. This 3inch diameter

Schedule 10 system (figure 34) consisted of two burst-disks in parallel each at 25 psig cracking

pressure downstream of a 3-way valve (XO-2105), a 2 inch back-pressure control valve (XO2104) and a 3 inch main vent valve (XO-2109) set to open by the facility PLC at a high ullage

pressure of 24 psig. Instrumentation provided with the system included temperature and pressure

transducers and an orifice run designed to measure the STA heat leak by a boil-off gas

determination. The line size of the 3 inch assembly was increased to 6 inch Schedule 10 in a

vertical riser section downstream to reduce gas pressure drop at high vent flow conditions. This

particular system could vent several types of vapor during STA loading tests including GN2,

GO2, GH2 and GHe. The nominal design value for venting GH2 vapor through the system was

0.5 lbm/sec. (Note: Hydrogen densifier testing with the LH2 PDU and STA tank was cancelled by

the MSFC Program Office. The LH2 densifier was however cold flow tested with liquid nitrogen

at the S40 in 2002).

NASA/TM—2010-216247 42
Figure 34. STA test article vent / valve package assembly.

4.8 S40 Electrical Systems

The South-Forty electrical system could provide up to 1000 KVA of power to the

densification unit test site upper area. The main power supply cable ran from feeders located

inside Building 202 to the densifiers 480 V, 3-phase, 60 Hz interface power feeder panel on the

skid. The Substation at Building 202 was equipped with a 1200 Amp breaker which provided

sufficient over current margin for densifier operations. The power supply requirements for the

LO2 and LH2 densification units were 500 KVA and 750 KVA, respectively. The LO2 and LH2

PDU’s would require up to 500 Amps and 800 Amps at 480 VAC, 3 Φ and 60 Hz, respectively.

In a GH2 test environment, electrical devices installed at the S40 test site were rated for

Class I, Division II, Group B per the National Electric Code (NEC) for hazardous substances

given the potential presence of hydrogen in the area during LH2 PDU testing. Other S40

electrical safety design features implemented to conform to the NEC included the use of purged

electrical NEMA 4 cabinets, intrinsically safe circuits and explosion proof enclosures. The

facility was equipped with lightening protection in the form of an aerial seven strand copper clad

steel wire running diagonally over the test site. Three closed-circuit video cameras with zoom

lens and pan/scan capability were positioned through-out the facility. The video cameras by

Panasonic allowed remote visual monitoring of the STA tank, facility dewars and the densifier

skid. An elaborate perimeter grounding system was constructed with 4/0 ground loops and 10 ft x

0.75 inch diameter grounding rods. Electrical grounds were installed on all facility dewars, the

STA tank, the densifier skid as well as other required electrical and mechanical subsystems.

4.9 Facility Safety Systems

All systems at S40 were designed and installed to provide fail-safe, trouble-free

operation. Design practices required that engineered systems conformed to the NASA Glenn H2

& Pressure Systems Safety Manuals and the Occupational Safety & Health Administration rules.

To further assure quality assurance and worker safety, other standard design codes employed for

facility systems included the ANSI/ASME B31.3 Process Piping Code, ASME Section VIII Div I

NASA/TM—2010-216247 43
Pressure Vessel Code, MSFC Spec 164B for LO2 Cleanliness and the Compressed Gas

Association Standard CGA S-1.3 for Pressure Relief Devices. Other features of safety devices

implemented for the S40 test site included PLC health monitoring of critical system parameters

and GH2 detectors in the event of LH2 testing. All pressure relief valves that were out-of-service

for longer than one year were checked-out and re-certified by flow test.

4.10 Facility Instrumentation and Controls

The control room used for the S40 PDU testing was the Rocket Operations Building

(ROB), commonly referred to as ROB, Bldg. 100. The building 100 control room was located

approximately 2100 feet north-west of the S40 upper area. Temporarily located inside the control

room (figure 35) was the densification skid operator control station, a S40 facility operator

control station, four researcher PC work stations and video monitors with camera controls. A

fiber-optic cable linked

the densifier PLC with the --raw,

PDU operator control R'• ' : '

station. South Forty " _ ,.F . • • ..

facilityinstrumentation ^' r `r` '^ Ir • _,

associated with the PDU + "t , I Y - - _ u

testing included silicon

diodes, pressure

transmitters, differential

pressure indicators, flow ^' ^•_ `_: `^

meters, thermocouples

and capacitance liquid

level probes. The densifier

PC was set-up to be ^' ' • , f ^^

responsible for all facility

data acquisition = '^^.^^^ mac. ,^. •:.:••••".^ ..[ _x

requirements. Facility data Figure 35. Building 100 control room set-up for LO2 densification test operations.

was recorded at a

maximum record rate of one scan per second. Approximately 220 facility Input/Output

data/Control channels fed the S40 facility PLC which was linked to the densifier IBM PC mass

data storage via a ModBus Plus coaxial cable. Presented in Appendix C is a listing of the S40

facility instrumentation that was utilized at the test site.

5. TEST OPERATIONS and PROCEDURES

The following sections of the report provide general descriptions and a discussion of

operations and test procedures with the LO2 propellant densification unit (PDU), the STA tank

and S40 facility systems. Due to the scope of the program, testing would involve several different

test setups and two different test fluids, which were LN2 then LO2. The planned test events at the

GRC S40 densification site in the order of their occurrence were:

• GN2 Compressor Check-Out Tests

• LO2 Pump Check-Out Tests with LN2

NASA/TM—2010-216247 44
• LN2 Performance Testing with LO2 PDU

• STA Boil-Off with LN2

• LN2 Thermal Stratification Tests with STA

• LO2 Performance Testing with LO2 PDU

• STA Boil-Off with LO2

• LO2 Thermal Stratification Tests with STA

5.1 Gaseous Nitrogen Compressor Check-Out Test Procedures

The purpose of the compressor tests were too evaluate compressor controls software, tune

PID surge and pressure control loops, trouble-shoot hardware, verify start-up procedures, identify

and test transients and achieve steady-state operation. Compressor start-up and check-out tests

involved running the GN2 compressor under no external exchanger heat load. This means

without an LN2 or LO2 flow stream moving through the heat exchanger tubes. Inlet gas flow rate

conditions to the compressor were satisfied with the surge bypass system that dumped warm gas

into the liquid bath causing nitrogen vapor to boil-off. Initially dewar N-71 was pressurized to 30

psig (45 psia) and was placed in a back-pressure control mode. Following line chill-down, the

stage 2 heat exchanger bath level was replenished with LN2 to its normal operating level of 48

inches and the level controller was engaged. All of the appropriate LN2/GN2 valves positions

were verified prior to compressor start. A “Reset” on the operator control console was activated

which established a “Ready” light meaning proper communication existed between the PLCs. A

test pressure control set-point in-between the control limit range of 2.4 – 10.0 psia was

established and the compressor “Start” button depressed. The compressor spin-up process would

begin as the rig would accelerate through two phases of ramp and then its speed would level-out

as the test inlet pressure set-point at pressure transducer PT-715A was approached, at which

point the compressor speed would stabilize to a constant value. The compressor would be

allowed to run for a long enough period of time to demonstrate steady state conditions and then

the test was stopped. After the compressor coasted to a stop following the aborted or controlled

shutdown, the subcooled LN2 in the second stage heat exchanger would be re-warmed and

brought back up to its NBP by GN2 injection into the LN2 bath.

5.2 LO2 Pump Check-Out Test Procedures

The purpose of tests with only the LO2 pump in operation were to verify actual pump

performance in terms of measured head rise (∆H) and delivered flow rate (Qv). In addition, the

testing was designed to trouble-shoot and tune the flow control loop of the pump’s variable speed

control logic. The test operations involved initially pressurizing the pre-chilled STA to 30 psia.

Before pressurizing, the STA vessel would normally contain some small quantity of liquid that

wetted a lower vertical diode sensor near PVT-24. Dewar N-83 was pressurized with GN2

anywhere from 25 – 35 psig and then placed in a back-pressure automatic control mode with

valve XO-8313. To add flow resistance to the fluid transfer system downstream of the LO2

pump, the skid control valve FCV-555 was manually throttled back to a designated percent open

position. In the manual performance mapping tests, the LO2 pump was started and ran at a

constant predetermined speed for a short period of time to allow collection of pump pressure rise

(∆P) and mass flow rate data points. As the test progressed, either the position of control valve

FCV-555 was manually varied or the pump speed was step-changed, both over the allowable

NASA/TM—2010-216247 45
power capability of the motor drive at that particular operating speed. The range of operating

speeds for test ranged from approximately 1000 rpm to 4200 rpm (design speed), and with

control valve positions anywhere between 30% and 100% open. The flow path direction in these

pump check-out tests was from dewar N-83, through the LO2 pump, across the densifier skid and

then into the STA tank which acted as a collector vessel. The other variation of the pump test

procedure was for control loop tuning purposes. In this test, a designated mass flow rate on the

operator control console was selected, the pump started and then it was monitored for proper

response of the pump to achieve and maintain the desired mass flow (W). Pump speed control

was accomplished by an analog 4 – 20 mA control signal corresponding to a synchronous speed

range of 0 – 4800 rpm.

Figure 36 shows the calculated AP-flow curve for the Barber-Nichols LO2 pump at its

rated design speed of 4200 rpm. A reduced speed curve displays the predicted performance at

2660 rpm, and the dashed line indicates an intermediate LO2 pump performance envelope at

3530 rpm. For initial tests of the LO2 pump with LN2 as the test fluid, the differential pressure

rise across the pump were different than design values and would naturally be reduced due to the

lower LN2 density at the same pump operating point. A performance curve for a 200 gpm LO2

pump with a 15 FIP close-coupled drive manufactured by the Cryo-Mach Corporation is also

presented in the figure 36 performance curve (CM). This particular centrifugal pump ( figure 37)

was used as a spare back-up during a significant portion of the LO2 PDU test series. Early on in

the testing, the originally furnished LO2 pump from Barber-Nichols suffered reoccurring

mechanical shaft seal leakage problems. Seal redesign and repairs were made, successfully

correcting the problem near the end of the six-month LO2 PDU test program.

Figure 36. Barber-Nichols (BN) and Cryo-Mach (CM) LO2 pump performance curves.

100

90

80

70

a

Q 60 BN Design Pt •

50 n ,., n .. n .

Q

v

+'f.

40

a 30

20

10

)K 2500 rpm (CM)

• 4200 rpm (BN)

n 3530 rpm (BN)

A. 2660 rpm (BN)

0

0 50 100 150 200 250 300 350

Flow (gpm)

NASA/TM—2010-216247 46
TEFC Motor

15 HP, 460 V

Figure 37. Cryo-Mach spare LO2 pump used during Barber-Nichols pump seal failure and repairs.

5.3 LO2 and LN2 Performance Test Procedures with LOX PDU *

The LOX densifier performance test procedure with liquid oxygen involved pumping

NBP LO2 from the N-83 supply dewar through the densifier skid heat exchangers where the fluid

was subcooled by an indirect heat transfer process as previously described. The densified LO2 at

approximately 120 oR to 130 oR, this dependant upon compressor set-point pressure, exited the

skid and was admitted into the STA which served as a receiver vessel or catch tank. The densifier

performance flow test was continued until the STA tank became nearly filled to a normal

operating liquid level set at 28 inches from the top of the tank. These STA Fast-Fill loading tests

were conducted with both the GN2 compressor and the LO2 pump in concurrent operation. A

simplified flow diagram (figure 38) of the LO2 PDU performance testing conducted with either

LO2 or LN2 depicted the major flow-paths and test setup configurations utilizing the S40 facility

dewars and the STA tank. The operational test procedures with LN2 as the product fluid exiting

the densifier was essentially identical to when running performance tests with LO2.

General operations of the LO2 PDU performance test was first to pressurize the dewar N71 to 30 psig (45 psia) for LN2 heat exchanger bath level maintenance. For these tests dewar N83 was always filled or partially loaded with at least 20,000 gallons of liquid oxygen to

accommodate the STA total fill volume available. The LO2 supply dewar ullage pressure was set

to 35 psig (50 psia) by placing its controller (PIC-8390) in an automatic back-pressure mode

while valve XO-8313 regulated GN2 pressurant flow to maintain the ullage set-point pressure.

Prior to test, a liquid oxygen chill down of the following systems would take place: LO2 facility

transfer lines; LO2 densifier skid fluid subsystems; and initial STA receiver tank chill-down and

“partial” fill up to diode PVT-24 located at the 1,340 gallon mark. Liquid nitrogen facility

transfer lines and skid LN2 systems were prechilled and primed from dewar N-71.

* The densifier performance test procedures used for LO2 and LN2 were the same. The only significant process

difference noted was the N-83 dewar service change, depending on the cryogen to be tested and the use of GHe

purges on select LO2 transfer systems.

NASA/TM—2010-216247 47
The STA would then be pressurized with GN2 to 30 psia and was placed in automatic

back-pressure control regulated by a pressurant supply valve (N-2214) and a vent control valve

(XO-2104) both working in tandem to maintain the set-point pressure within ± 0.5 psi based on

feed-back from the STA ullage pressure transducer (XO-2103). Three solid-state video cameras

mounted near the skid were positioned to view the STA and skid test articles during the

performance testing.

GN2

Vent

1I SD PT

Legend LT v

LN2 Flow

LO2 Flow ^I

n

El

PDT PT

STA

CJ Closed Open L Tank

GHe GN2

1 Lobe2

3” SSVJ

^1 ^p1p

m mp

3” SSVJ LO2

LO2

PDU

o

3” SSVJ LO2 ^ ro

O GN2 O Vent

12” SS

gN2

6” SS

Figure 38. Simplified schematic of LO2 or LN2 Performance tests of LO2 Propellant Densification Unit at S40.

At the PDU, the LN2 supply flow path and continuous bath level control on both skid

heat exchangers would be established, this originating at dewar N-71. Here, the liquid level

control (LT-620) on the 1

st stage heat exchanger LN2 bath was set to 51.8 inches while the 2 nd

stage bath level transducer (LT-615) set-point was 48.1 inches. A verification of valve positions

was made for both the compressor and then subsequently the LO2 pump operation. Initially the

start-up procedure of PDU rotating machinery consisted of GN2 compressor start with no heat

load until stable operation was reached and then start-up of the LOX pump at a preset and

constant speed to achieve the test mass flow rate of LO2. Typically the LO2 mass flow rate

would be varied during the course of an STA loading test by changing control valve FCV-555

position to obtain performance mapping data of the PDU across a range of LO2 flows.

Densified LO2 entering the STA would be into both bottom inlet lobes for all of the FastFill performance tests conducted. Termination of the LO2 performance test occurred when liquid

oxygen reached a level associated with diode sensor PVT-3 at which point the LO2 pump was

NASA/TM—2010-216247 48
stopped and then the compressor was shut-down. Following rpm coast spin-down of the GN2

compressor, approximately 1,200 gallons of subcooled LO2 would be drained-back from STA to

increase ullage volume as the fluid warmed and expanded during the 48 – 56 hour hold period

inside the STA. Ambient heat leak to the STA would essentially re-saturate the fluid and warm

the LO2 back to its natural NBP state of 162 oR. It’s noted that due to the lower mass present and

smaller temperature difference, the warm-up time for densified LN2 in the STA was only 24 – 36

hours. Prior to start of the next densifier performance test cycle, the 17,400 gallons of NBP LO2

inside of STA was back-transferred to dewar N-83 for reuse.

5.4 STA Boil-Off Test Procedure with LO2 or LN2 *

A single boil-off test would be run with the STA filled with normal boiling point (NBP)

liquid nitrogen and, later on in the program with NBP LO2. The test was designed to measure the

tank’s steady-state heat leak and provide data for the LMMSS thermodynamic tank models. The

general procedures for conducting a boil-off test of the STA tank would involve filling the tank

with NBP LO2 to the 28 inch liquid level up to silicon diode PVT-2. The LO2 volume at the

initial fill point was about 18,835 gallons of liquid, this corresponding to an ullage volume of 0.9

percent. The STA main vent valve (XO-2190) was closed while the orifice run isolation valve

(XO-2112) would be opened. The GO2 boil-off vapor vent path would be through a 3 inch SS

Sch 10 vent line where a square-edged orifice plate with a 2.12 inch ID was installed. Inlet gas

temperature (T1 ), upstream pressure (P 1 ) and orifice ∆P measurements were taken at one-second

intervals. The boil-off test was continued for a minimum of three hours or until a steady-state

thermal condition in the tank was reached while data was continuously recorded. The test was

terminated after sufficient steady-state data was gathered as indicated by a constant boil-off mass

flow rate (W1 ). The orifice equation (eqn. 11), combined with the ideal gas law (eqn. 12) were

used in the post-test data reduction process of the LN2 and LO2 STA boil-off tests conducted.

W1 = 0.525 Y C d, ∆P ρ

1

(11)

= 

P1 MW

ρ1 (12)

Z R T1

where

C = orifice flow coefficient = 0.67

do = orifice diameter, inch = 2.120 inch

MW = molecular weight = 28.0 lb/lb-mol GN2 ; 32.0 lb/lb-mol GO 2

P1 = upstream pressure, psia

∆P = orifice pressure drop, psi

R = gas constant = 10.7315 psia-ft 3

/lb-mol oR

T1 = upstream temperature, oR

W1 = gaseous nitrogen or oxygen boil-off mass flow rate, lb m/sec

Y = expansion factor = 0.99

Z = compressibility factor at 14.7 psia, 200 o

R = 0.986 GN2 ; 0.982 GO2

ρ1 = upstream gas density, lb/ft3

* The STA boil-off test procedures used for both LO2 and LN2 were the same with the exception of minor

differences in the post-test data reduction equations for vapor density ρ1 used to compute boil-off vent rates.

NASA/TM—2010-216247 49
5.5 LO2 or LN2 Closed-Loop Thermal Stratification Test Procedures with the

LOX PDU *

The densifier closed-loop thermal stratification test procedure involved recirculating LO2

from the pre-filled STA and through the densifier skid where the fluid was subcooled. Initially

the tank started out fully loaded with NBP LO2 at a constant 162 o

R and then the recirculating

flow would begin. The subcooled LO2 exiting the skid at 120 oR – 122 oR was then readmitted

into one or both bottom lobes of the STA tank. The recirculation flow test would continue until

the STA tank reached its thermal equilibrium limitation. This would take up to 4 hours

depending on the recirculating mass flow rate during the test. The equilibrium condition by

definition occurred when STA became completely chilled down with densified LO2 as indicated

by the characteristic stabilization of the syphon outlet temperature at facility diode sensor XO2305. A simplified process flow diagram ( figure 39) of the STA tank with principal interfaces

and S40 facility tie-ins illustrated the major fluid flow paths that were employed during an LO2

or LN2 closed-loop thermal stratification test. The operational run procedures with LN2 as the

recirculating fluid were identical to the thermal stratification tests conducted with LO2.

GN2

Vent 3” SSVJ

SD PT

Legend

I ^J LT

PDT

C^ L PT Tank

GHe GN2

Lobe 1 1 Lobe2

D

D

T S L1

3” SSVJ El SD

LN2

Z O

^ 1^1

M M H

3” SSVJ LO2

LN2 LO2

M

PDU

LO2 2” SSVJ

r Mi

T D o

3”SSVJ LO2

^z I

^' GN2

O Vent

O

? m

Cl) 0 12” SS

gN2

6” SS

Figure 39. Simplified schematic of LO2 or LN2 closed-loop thermal stratification tests of LO2 PDU at S40.

* The densifier closed-loop thermal stratification test procedures used for LO2 and LN2 were the same. This only

exception to this was the N-83 dewar service change, depending on the cryogen to be tested, LN2 or LO2, and the

use of GHe purges on select LO2 fluid transfer systems.

NASA/TM—2010-216247 50
A key test article of operational importance, used during the LN2 and subsequent LO2

closed-loop thermal stratification testing, was the STA dual-lobe liquid oxygen tank. The

significance of the test was to simulate on a large scale the production and loading operations of

densified LO2 that would be used in an actual launch pad environment. The normal mode of

operation for a typical LO2 closed-loop recirculation–thermal stratification test involved filling

STA with NBP LO2 from dewar N-83 by pressure transfer. After liquid top-off, the STA ullage

was pressurized to 30 psia with GN2 and set in a back-pressure control mode. Final chilling and

priming of the LO2 syphon line 4 inch downcomer would take place by flowing from the top of

STA and through the LO2 skid. High point and low-point bleeds in the STA outlet piping

connecting the skid enhanced the operation for pre-establishing the flow. Operation of skid

mounted equipment including pump, compressor and heat exchangers was as previously

described. Closed loop flow of LO2 would be established by turning on the LO2 recirculation

pump. The LO2 pump start-up occurred only after the GN2 compressor, that was pre-started

earlier, had stabilized and reached its inlet pressure set-point typically running at 2.8 psia.

The LN2 supply dewar N-71 pressure was maintained at 45 psia for LN2 bath heat

exchanger make-up and level control. The LO2 N-83 dewar pressure was held constant at 50

psia. The facility valves in-between N-83 and the LO2 PDU were configured to allow LO2 makeup flow to maintain the STA liquid level constant as a result of the densification process which

lowered the fluids specific volume (1 /ρLO2). The LO2 makeup valve on the skid was controlled

based on the STA capacitance level probe (LIC-2000) which had a control set-point of 24.0

inches. A steady-state thermal stratification was achieved within about 4 hours of continuous

recirculation of the densified cryogen. Steady-state was defined to occur when the STA siphon

outlet temperature at diode XO-2305 stabilized with respect to the incoming fluid inlet

temperature at diodes XO-2402/XO-2502 and this delta temperature ( ∆TLO2 = Tout – Tin) reached

a minimum and steady condition. Like in the PDU performance test procedures, following

shutdown of the GN2 compressor, approximately 1,200 gallons of subcooled LO2 was drainedback from STA to increase ullage volume and allow room for fluid expansion during the groundhold. The densified fluid would then go into a hold period while it was stored in the STA to

allow the fluid to re-saturate to its NBP, this typically being 24 – 36 hours for a load of LN2 and

48 – 56 hours for densified LO2. Prior to start of the next thermal stratification test cycle, the

STA level was replenished with NBP LO2 from dewar N-83.

6. TEST RESULTS

6.1 Test Results Summary

This section of the report provides detailed results of each phase of testing conducted at

the NASA GRC with the X-33 LO2 PDU, its components and the STA. In general, these monthlong efforts culminated in successful demonstrations of the production and loading of densified

LO2 inside the large-scale STA propellant tank. In excess of 150,000 gallons of densified LO2

and over 200,000 gallons of densified LN2 each at about 120 oR were produced with the PDU

during the demonstration program. Of the original planned experimental matrix, the following

major test accomplishments were completed during the five-month test campaign at the S40

facility: four PDU performance tests with LN2; one closed-loop thermal stratification test with

NASA/TM—2010-216247 51
LN2; five PDU performance tests with LO2; and, four closed-loop thermal stratification tests

with LO2. At the beginning of the program an STA LN2 cold shock test followed by a pneumatic

proof pressure test at 60 psia were conducted with the STA tank as well. In addition, over 150

individual GN2 compressor start-up/performance tests and in excess of ten LO2 pump

mapping/check-out test series were run. Table 5.0 provides a chronological summary of the S40

test activities along with the date or period of actual test completion.

Table 5.0: Program summary of South-Forty LOX densification test activities.

Chronological Densification Test Events

6/30 - 7/10/00 S40 facility LN2 cryogens on-site.

7/11/00 STA LN2 cold shock test.

7/13/00 STA pneumatic proof pressure test.

7/15 - 8/3/00 GN2 compressor start-up, trouble-shooting & check-out tests, Phase 1.

7/7 - 8/25/00 STA LN2 loading tests. Strain gage refurbishment & strut characterization.

7/21 - 9/15/00 BN LOX pump check-out, trouble-shooting & seal repairs.

8/22 - 10/4/00 GN2 compressor start-up, trouble-shooting & check-out tests, Phase 2.

8/25/00 STA boil-off test with LN2.

9/29/00 Replacement Cryo-Mach LO2 pump installed & tested.

9/22 - 10/7/00 LN2 performance tests of LO2 PDU (qty 4).

10/8/00 LN2 closed-loop thermal stratification test with LO2 PDU (qty 1).

10/10 - 10/14/00 S40 facility conversion from LN2 to LO2. LO2 cryogens on-site.

10/14 - 11/15/00 LO2 performance tests of LO2 PDU (qty 5).

10/26/00 STA boil-off test with LO2.

11/18 - 12/5/00 LO2 closed-loop thermal stratification tests with LO2 PDU (qty 4).

12/12/00 BN LO2 pump reinstalled, tested OK then LO2 STA loading test (qty 1).

12/13 - 1/15/01 Termination of densification testing. S40 facility clean-up of LO2.

The next eight sections of this report cover major test results, anomalies, tanking and detanking operations, ground hold of STA with densified fluids and densifier performance data for

the following series of check-out and test events: GN2 compressor check-outs; LO2 pump

performance tests; STA boil-off measurements, LN2 performance runs with LOX PDU, LO2

performance runs with LOX PDU, STA LO2 closed-loop thermal stratification testing, and

finally a summary of system performance analysis results made in comparison to select design

points of the densifier.

6.2 Gaseous Nitrogen Compressor Tests

A series of gaseous nitrogen (GN2) compressor and associated auxiliary system checkout

tests were conducted over the course of eight weeks. This work started the week of July 15, 2000

in preparation for the start of actual S40 Propellant Densification planned test matrix runs.

Through two phases of compressor testing, a total of approximately 150 individual GN2

compressor start-up and check-out test runs were ultimately made. On average at least 15 – 20

start-up tests were run during any given week, while in-between test runs, the transient and

steady-state performance data was analyzed and corrective actions were made prior to re-test.

NASA/TM—2010-216247 52
representative, a

systematic GN2

compressor start-up, 16

trouble-shooting and

check-out test program 14

began. Typical

compressor speed, 12

interstage pressure

profiles, gas interstage 10

temperature profiles

N

and GN2 mass flow 8

rate transients as they

developed during a 6

nominal compressor

start-up test are as 4

shown in figure 40

through figure 43,

respectively.

2

Figure 41. Compressor interstage pressure profile.

Test No. 79

PT715D 3rd Stg Outlet 07/31/00

— PT715A

— PT715B

— PT715C

— PT715D

PT715C

PT715B

PT715A 1

st Stg Inlet

0 10 20 30 40 50 60 70 80

Time (min)

Preliminary start-ups of the GN2 compressor conducted early-on by GRC research

personnel resulted in identification of numerous premature shut-down problems associated with

specific compressor

hardware and its PLC Figure 40. gN2 compressor speed vs. time profile. code. Even though the

compressor was

originally tested by the 12000

3rd Stg

OEM in a series of SC715C

shop air tests at their 10000

plant, new untested

problems would only 8000

become evident while 1 st Stg

running fully loaded SC715A

with the actual GN2 6000

a^

test fluid at cryogenic cn

conditions and near 4000 Test No. 79

compressor design 07/31/00

point speeds. 2000

— SC715A

— SC715B

Beginning in late July, — SC715C

and with the assistance

and on-site support 0

from a Barber-Nichols 0 20 40 60 80

technical Time (min)

NASA/TM—2010-216247 53
TT715D 3

rd Stg Outlet

2nd Stg Outlet

1

st Stg Outlet

TT715A 1

st Stg Inlet

Figure 43. Compressor mass flow rate and gas bypass flow vs. time.

3.5

3.0

2.5

h FT715 Compressor Outlet Flow

2.0

p FT715S Gas Bypass Flow

Ii 1.5

1.0

Test No. 79

07/31/00

FT715

FT715S

0.5

0 20 40 60 80

Time (min)

Initially several PLC tuning parameters and compressor control software changes were

made and then tested. The majority of these changes resulted in gradual improvement to obtain a

more stable, lengthy and fault-free operation of the compressor. Troubleshooting of the

compressor PLC settings continued on with the goal of achieving the desired inlet pressure

design point condition of 2.4 psia without a fault shutdown occurring.

NASA/TM—2010-216247 54
Figure 45. Compressor flow coefficient surge instability shut-down.

0.80

FC3

0.70

Start of surge

Test No. 116

0.60 09/19/00

FC2

0.50 ^- FC 1

C

a) t FC2

— FC3 E: 0.40 a) 0

U

0 0.30

FC1 1 st

LL

Stg

0.20

Am 0.10

0.00

0 3 6 9 12 15

Time (min)

Four prevalent types of fault shut-downs the test team faced included the following: 1)

over-current (OC) shut-down events indicated in figure 44; 2) a surge instability shut-down as

illustrated in figure 45 with resultant loss or reversal of flow; 3) nuisance high “spike” vibration

shutdowns shown in

figure 46; and 4) a high Figure 44. Compressor over-current (OC) fault shutdown.

motor winding

temperature shutdown 140

that affected all three

stages. The vibration 120

shutdown was

perceived as a nuisance 100

issue because the high E

vibration data peak 80

lasted just C

momentarily. Issue 60

number four was likely

the most challenging of 2 40

0

6

these problems. This

problem would 20

repeatedly occur during

normal sustained

compressor operation

and then lead into an

early shutdown (figure

47) on a high motor

winding temperature

redline specified at

Tmotor > 310 oF (770 oR)

that developed after

only about two-hours of

run-time. It is noted that

the LOX densification

production timeline

requirement for X-33

was 2.5 hours.

Numerous PLC tuning

parameters and

compressor control

software changes were

made, downloaded to

the slave PLC and then

retested. These included

for example, stage

speed ratio constants,

flow coefficient control

Stage 2 OC fault

Test No. 118

09/19/00

+ C715A_Amps

3

rd St --F- C715B_Amps

9

C715C_Amps

1 st Stg

0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Time (min)

NASA/TM—2010-216247 55
set-points, PID gain constants for inlet pressure and surge avoidance control, high and low shutdown limits, and internal PLC scaling parameter adjustments.

0.45

0.40

0.35

0.30

0.25

c

0.20

12

0.15

0.10

0.05

0.00

Figure 46. GN2 compressor high vibration shutdown event.

0 2 4 6 8 10 12 14

Time (min)

Test No. 26

07/18/00

+- VT715A

-M- VT715B

-}- VT71 5C

A remote RS485 interface from the Building 100 control room to the compressor PLC

located at the S40 site was subsequently set-up and put into operation. This added feature helped

allow expedite changes being made to the compressor controls software. The compressor control

problems appeared to be effectively resolved after about six weeks of continuous onsite set-up,

testing and adjustments by Barber Nichols and GRC research engineers. These operating

successes were compounded by several critical hardware failures and performance issues which

NASA/TM—2010-216247 56
had occurred with the GN2 compressor skid during the six month S40 test program. Table 6.0

describes the more significant GN2 compressor hardware problems that GRC encountered during

test operations with follow-on descriptions of key activities briefly discussed below.

Table 6.0: Gaseous nitrogen compressor hardware failures and operational issues.

Date(s) Location / Stage Failure / Fault Condition Corrective Action Taken

No.

8/1/00 Stage 3 drive Motor winding ground fault short Motor stator replaced by BN

8/31/00 Stage 2 VFD VFD control and genius card Parts replaced inside VFD2

failures

9/13/00 Stage 2 VFD Internal corrosion on contacts New VFD installed on Stage 2

causing VFD fault shut-downs

10/04/00 Stages 2 and 3 Current induced harmonics on drive Reduced operating speeds to stay

motors below 10,000 rpm critical speed

where currents would fluctuate.

10/31/00 Stage 1 drive Lower bearing failure New bearings installed by BN

As-built All Stages High motor winding temperatures at Reduced flow coefficient

less than design full load current controller set-point from 0.25 to

0.18. De-rated inlet pressure

performance from 2.4 to 2.8 psia

As previously mentioned, the GN2 compressor AC drive motors were found to run too hot

at or near the normal design point of the compressor system. The lowest attainable set-point

pressure the PDU could be operated at would be 2.8 psia which is 0.4 psi above design. It was

determined that this would be a necessary condition in order to prevent the compressor system from

shutting down by a high-motor winding temperature shut-down during a sustained compressor test

run. According to BN the OEM, the normal expected SS motor operating temperature should be

about 220 oF while the shutdown was automatically setup in the PLC to occur at 310 oF. This

protected the motor internals from insulation burn-out. The de-rated operation resulted in a

moderate performance loss on the expected PDU outlet LO2 temperature by about 1 – 2 o R because

of a resultant 3 – 4 oR higher stage two heat exchanger bath temperature. The high motor winding

temperatures was later diagnosed to be due to an inadequate thermal design of the glycol cooling

system on the 70 HP drive motor system. This deficiency attributed to marginally low ∆T

measurements (~ 3 oF) of the coolant fluid. Internally generated heat could not be sufficiently

removed from the motor stator walls when the compressor was running “near fully-loaded” at the

2.2 to 2.4 psia design inlet pressure while drawing current well below its rated design Full Load

current of 88 amps as shown in the figure 48 plot of motor temperature and current transients

during LN2 performance Test 1A run on 09/22/00.

Another operational issue associated with the GN2 compressor was an observed currentinduced harmonics phenomena as shown in figure 49. A high amplitude current oscillation was

typically found to occur on Stages 2 and 3 but only when the GN2 compressor would approach

and was operated at approximately 10,000 rpm. Neither the GRC test operations team nor the BN

field service engineers could identify the cause or resolve this current oscillation problem. This

therefore became another reason for “de-rating” the compressor design point speeds by at least

100 rpm to stay below the 10,000 rpm “critical-speed” region where the Stage 2 and 3 currents

were observed to start to fluctuate.

NASA/TM—2010-216247 57
oug severa wee s

time until GRC

160

engineers corrected or

140

developed “work- 120

arounds” of all issues

E 100

and finally became "r= -

satisfied with 80

compressor 60

performance, reliability

and operation. As of 40

October 4, 2000 the final 20

set of PLC tuning

0

C715A AMPS Motor temps

• C715B AMPS

C715C AMPS 1

st St

...... TT715M1A '^""^^-_ •

.... - . • TT715M2A 2^d Stg

• TT715M3A

----- 88 FLA max. . N^h

F-Motor currents 3

rd

1

st Stg

The troubleshooting Figure 48. Compressor current and motor winding temperature vs. time.

activities continued on

hr h l k

LN2 Performance Test No. 1.9/22/00 t 350

300

250

200

150

100

50 0

0

-50

-100

parameters and 0 50 100 150 200 250

compressor control Time (min)

software changes were

made and then tested. Figure 49. Compressor motor current oscillation vs. speed anomaly.

The test team made the

decision that compressor 75 12000

SC715C_AMPS Test No. 110 control and performance { 3rd Stg SC715A 09/14/00

issues had been 70 10000

satisfactorily corrected C715A AMPS Speed

C715B_AMPS during the check-outs. 65 C715C AMPS 8000

E

_

CL

Those issues reconciled SC715C

included surge avoidance 60 ''^ 6000 Na

tuning, resolving over- 2 t

current shutdowns, 55 1 4000 in

elimination of nuisance

vibration shutdowns and 50 2000

SC715A AMPS debugging of high drive 1

st Stg

motor operating 45

i

0

temperatures. The 0 10 20 30 40 50 60 70 80

modified target goal of Time (min)

2.8 psia inlet pressure

into the first compressor stage were routinely demonstrated during at least ten long duration ( >

120 minute) system tests of the GN2 compressor. These particular tests resulted in a controlled

system shutdown (“OFF button depressed”) and gave performance that closely achieved the LOX

PDU production goal of 30 lbm/sec of LO2 at 120 oR outlet. Results of six representative GN2

compressor check-out tests during this specific Phase of the program, each at a steady-state

condition, are tabulated in Table 7.0. Appendix D contains two complete sets of representative

GN2 compressor start-up data plots (Test no. 79, 7/31/00) as the rig was operated both prior to

final PLC tuning changes completed on October 4, 2000 and then during the follow-on LN2 and

LO2 performance tests (Test no. 144, 10/27/00).

NASA/TM—2010-216247 58
Table 7.0: Gaseous N2 compressor performance check-out test data and steady-state (SS) results.

Tag

ID

Description – GN2 compressor

steady state data ‡

No. 73

7/29

No. 79

7/31

No. 82

8/22

No. 84

8/23

No.110

9/14

No.144

10/27

N/A GN2 compressor run time, min 61 84 70 88 74 92

SC715A Stage 1 speed, rpm 10740 9912 10254 10432 9718 9332

SC715B Stage 2 speed, rpm 11062 10202 10560 10744 10012 9612

SC715C Stage 3 speed, rpm 10416 10504 10866 11058 10304 9894

FT715 Compressor vent flow, lb/sec 2.06 2.19 2.17 2.09 2.12 2.05

FT715S Compressor surge flow, lb/sec 2.51 1.80 1.87 1.67 1.91 0.72

FT607 Heat exchanger bath fill, lb/sec 1.40 0.62 1.05 1.17 0.87 1.11

FC1 Stage 1 flow coefficient, 01 0.228 0.256 0.257 0.255 0.249 0.238

FC2 Stage 2 flow coefficient, 02 0.189 0.221 0.220 0.214 0.214 0.213

FC3 Stage 3 flow coefficient, 03 0.176 0.191 0.189 0.180 0.186 0.188

PT715 Stage 2 ht-exer, ullage press, psia 3.09 2.78 2.71 2.70 2.86 3.02

TT703A Stage 2 ht-exer, ullage temp, oR 120.5 119.4 120.7 124.1 119.8 122.6

PT715A Stage 1 inlet pressure, psia 2.39 2.38 2.41 2.02 2.42 2.80

TT715A Stage 1 inlet temp., oR 152.1 234.5 143.0 142.2 163.2 139.8

PT715B Stage 2 inlet pressure, psia 4.94 4.88 4.84 4.50 4.94 5.45

TT715B Stage 2 inlet temp., oR 166.9 200.5 167.3 163.2 160.1 167.9

PT715C Stage 3 inlet pressure, psia 9.05 8.67 8.73 8.39 8.69 9.31

TT715C Stage 3 inlet temp., oR 216.4 225.0 220.7 217.8 207.4 219.7

PT715D Stage 3 outlet pressure, psia 14.62 14.64 14.80 14.66 14.55 14.72

TT715D Stage 3 outlet temp., oR 262.4 221.5 282.6 281.5 264.7 269.4

C715A VolQ Stage 1 outlet volume flow rate, cfm 1601 1662 1725 1742 1580 1450

C715B VolQ Stage 2 outlet volume flow rate, cfm 1133 1222 1262 1246 1163 1111

C715C VolQ Stage 3 outlet volume flow rate, cfm 850 930 954 923 886 862

C715A Volt Stage 1 motor voltage, volts 460.0 433.8 449.1 456.8 425.9 408.9

C715B Volt Stage 2 motor voltage, volts 460.0 447.0 460.0 460.0 438.6 421.3

C715C Volt Stage 3 motor voltage, volts 456.3 460.0 460.0 460.0 451.3 433.4

C715A Amps Stage 1 motor current, amps 66.0 52.7 53.5 51.9 52.3 47.1

C715B Amps Stage 2 motor current, amps 70.5 55.7 56.5 57.0 54.6 48.5

C715C Amps Stage 3 motor current, amps 68.7 61.1 63.5 61.8 58.0 48.0

TT715M1A Stage 1 motor winding "A" temp. oF 250 235 245 257 217 187

TT715M1B Stage 1 motor winding "B" temp. oF 213 201 210 220 185 161

TT715M1C Stage 1 motor winding "C" temp. oF 237 225 233 243 207 183

TT715M2A Stage 2 motor winding "A" temp. oF 231 222 231 239 209 176

TT715M2B Stage 2 motor winding "B" temp. oF 233 224 234 243 206 174

TT715M2C Stage 2 motor winding "C" temp. oF 234 237 242 250 225 193

TT715M3A Stage 3 motor winding "A" temp. oF 206 233 255 263 224 180

TT715M3B Stage 3 motor winding "B" temp. oF 202 228 255 263 222 183

TT715M3C Stage 3 motor winding "C" temp. o F 189 214 252 261 222 177

VT715A Stage 1 vibration sensor, in/sec 0.167 0.120 0.129 0.118 0.135 0.127

VT715B Stage 2 vibration sensor, in/sec 0.118 0.101 0.132 0.112 0.172 0.083

VT715C Stage 3 vibration sensor, in/sec 0.099 0.096 0.007 0.007 0.084 0.071

ZT715 Gas bypass control valve FCV715

position transmitter, % closed

16.7 29.8 28.5 28.3 25.2 53.1

N7113 Dewar N-71 LN2 total outflow, gal 1260 530 580 760 510 1180

N7117 Dewar N-71 pressure, psig 17.9 19.8 20.1 23.2 20.1 20.0

Note: ‡ LN2 or LO2 recirculation flow rate at FT535 was zero for all compressor check-out test runs reported above.

NASA/TM—2010-216247 59
6.3 LO2 Pump Performance Tests

A series of LOX pump checkout tests began during the week of 7/23/00 in preparation for

the start of the South Forty Propellant Densification planned test matrix. An immediate problem

developed, however during initial start-up tests of the skids’ LO2 pump while flowing with LN2

at relatively low upstream and downstream pressures. The problem was that a significant leakage

problem with the pumps’ shaft mechanical seal had apparently occurred.

Replacement of the Barber-Nichols LOX pump seal was initiated. The test team

concluded that the seal appeared not to have failed on the very first cryogenic pump flow test

attempt with LN2. The pump was removed from the system and a component repair and changeout was accomplished. Repair inspections showed that the LOX pump seal was not physically

damaged, out-of-tolerance or worn. Several mechanical changes per BN recommendations were

made in the field by SLI technicians despite the intact appearance of the seal. These included

hardware surface re-polishing and replacement of the flexible Variseal. The pump was later

reinstalled on the LOX propellant densification unit on 7/28/00. A repeat LN2 cryogenic pump

flow test was conducted in-parallel with a planned STA loading experiment on 7/30/00 but

showed no real

improvement to LN2

leaking from the shaft seal •``

of the pump as indicated by

the radial pattern of spray Pump .• }

emitted seen in figure 50. C. Motor Housing +'

The BN pump was ••i

removed from the PDU I ••`

skid and return shipped to

the OEM shop for seal _

M Shaft seal leak

design reassessment, radial spray of

warranty repair and testing. _ LN2 jets

The failed LOX pump

remained at the

manufacturers shop for .

about four weeks and then 

Figure 50. Mechanical shaft seal leakage of LN2 during 9/1/00 BN pump check-out test.

arrived back at GRC on

August 26th for retest evaluation. The LOX pump was reinstalled on the densifier skid with

checkout tests completed on 09/01/00. These efforts resulted in a second pump seal failure that

was worse than the original leakage rate initially observed. The seal design changes were

ineffective with the pump rotating and while it was very cold at LN2 temperatures. Pump LN2

performance test data was however obtained, while the BN pump was operated for a short

duration with the leaking shaft as shown in figure 51.

In order to continue on with the S40 densification test program, an alternate pump was

required. It was decided that the program would utilize a spare cryogenic LOX transfer pump on

the PDU skid that was available and had been procured as a replacement pump for another

program, while the BN pump was sent back to the OEM. This spare Cryo-Mach LN2 pump was

temporarily installed on the PDU on Sept-29-2000 while the BN pump was at the OEM shop for

NASA/TM—2010-216247 60
repairs and in-house check-out test during most of the S40 campaign. The BN pump was not ready

for PDU service until the very end of the S40 program and for the very last test conducted with the

LOX densification rig.

The LN2 test results with the replacement centrifugal pump were encouraging and showed

that performance mapping tests based on head and flow with the back-up Cryo-Mach pump ( figure

52) were very close to meeting the 30 lbm/sec LO2 recirculation flow rate goal. One minor problem

encountered, however, with

the Cryo-Mach was that the Figure 52: Cryo-Mach pump performance with LN2. Flow and AP map vs. speed.

spare pump’s closed-loop

mass flow controller could 35

not be made functional by

GRC controls engineers.

This would in fact cause 30

some operational difficulties N

later on in the follow-up LO2

tests when trying to maintain 25

a constant mass flow rate o

(figure 53) “manually” N

through the PDU against a

variable system resistance 20

(i.e. changing STA head).

Subsequent pump

perf rm e tet nd ted 15 s s co uc 0

70

60

50

Z

40

30 N

20

10

o anc

with liquid oxygen as the 1000 1500 2000 2500 3000 3500 4000

test fluid were run with the Speed (rpm)

NASA/TM—2010-216247 61
Cryo-Mach pump as well in late October. These tests verified the LO2 pump flow rate and head

rise as a function of drive speed. Pump performance results were considered nominal and varied

from 130 – 195 gpm of LOX at 5 – 37 psid head rise in-between 1000 and 2000 rpm pump speed

as presented in the figure 54 summary mapping data. These test values confirmed the acceptance

of the Cryo-Mach pump performance versus requirements for this system component to support

the planned LO2 densifier tests with liquid oxygen. Reported in Appendix E are two complete

data sets of the Cryo-Mach LOX pump performance plots recorded during open-loop pump

mapping tests with both LN2 and LO2 as the test fluids.

Figure 53: LN2 mass flow rate by manual pump speed control against

increasing STA back pressure due to changing elevation head.

27 30

24

21

N

.2 18

aj2 15

3

12

WM

m 

E 9

N

z 6

3

0

0 30 60 90 120

Time (min)

Figure 54: Cryo-Mach pump performance with LO2. Flow and AP map vs. speed.

27 

rn.y

a

24 vii U)

a

a)

21 c

N

zJ

H

18 Cn

15

150

LN2 Performance Test

No. 4A, 10/07/00

Flow into both STA Lobes

FT535

LN2

Flow

xO0607

Inlet

Pressure

— FT535

—xO0607

35

0 

30

a^

N

OJ 25

3

0

N

N

f6

20

40

35

30

25 Nn

dN

20

N

15

(L

10

5

0

1000 1500 2000 2500

Speed (rpm)

Pump Test n

No. 10

10/17/00

n

•

• Mass flow

n Delta P

500

NASA/TM—2010-216247 62
One final remark worthy of mention was that on December 12, 2000, GRC completed a

LOX pump performance test with the “re-built” Barber Nichols pump. The totally redesigned

pump shaft seal worked perfectly this time with no indication of LO2 leakage observed during a

short 30 minute pump mapping test (Table 8.0) followed by a lengthy 2.5 hour LO2 loading test

of the STA. This pump test was the last and final experiment GRC conducted with the LOX

PDU during the test campaign at S40. The test operations team would then begin the lengthy

process of removing LOX from the system by allowing it to boil-off from inside the STA. It was

estimated that it would require two to three weeks time to get all of the LOX out of the systems

during S40 facility clean-up.

Table 8.0: Performance test results with Barber-Nichols LO2 recirculation pump.

Test Description: BN LO2 pump performance ¶

 mapping, 12/12/00. Test fluid: LO2

SC535 FT535 PT540 – PT525 P535_Amps ZT555

Pump speed,

rpm

LO2 flow rate Pump AP,

psid

Motor

current,

amps

FCV-555 position,

% Open lbm/sec gpm

1960 21.8 137.9 4.2 4.4 100.

2500 24.9 157.5 11.6 5.1 100.

3000 28.3 179.0 19.7 6.1 100.

3500 30.4 192.3 27.5 7.2 100.

¶ Note: Barber-Nichols LO2 pump design point is 190 gpm at 50.0 psid and 4200 rpm

6.4 STA Structural Loading Tests with NBP LN2

The purpose of the STA structural load testing was to verify the load carrying capability

and safety of the modified STA support strut configuration. As previously discussed (refer to

Section 3.5), there were twenty-four (24) original rack-and-pinion cylindrical strut members

(figure 55) attached to the Test Support Platform (TSP). These were used to support the tank at

MSFC during ambient load tests. Based on thermal modeling and stress analysis results by

LMMSS, only 7 of the 24 struts were installed by GRC on the STA because the model results

indicated that the tank was structurally over-constrained at cryogenic temperatures. This

modified support configuration would then first require testing and after validation, could be

used to support the cryogenic LN2/LO2 combined loads during densifier runs as shown in the

figure 56 schematic. The STA mass on-board was expected to range from 135,000 to 198,000

pounds of high-density propellant. In order to measure strut static and dynamic load

characteristics, each of the seven to eight struts were equipped with a single triaxial strain gage.

The strain gage output was monitored in real-time during the first several tanking operations with

NBP LN2. The strut strain gage test redline limits defined by LMMSS structural engineers would

be 65.7 kips compression (-) and 11.0 kips tension (+) maximum applied stress. If any one strut

approached or exceeded the maximum allowable force based on strain gage data, the test would

be scrubbed.

NASA/TM—2010-216247 63
EAST WEST

tained Strut

Figure 55. Original STA design twenty-four strut tank support configuration.

SOUTH

L

NORTH

L

Figure 56: Modified STA support strut configuration on the X-33 LO2 tank for propellant den sification testing.

A summary of the structural loading test results conducted in July through August is

reported in Table 9.0. The first four LN2 loading attempts resulted in run termination before the

tank was completely filled. Even though the stress analysis showed that the seven to eight struts

would be structurally adequate with margin, the strain gage test results obtained during Tests 1 –

4 gave indications of higher than allowable loads.

NASA/TM—2010-216247 64
Table 9.0: Test summary – STA structural loading tests with NBP liquid nitrogen.

Test $

No.

Date Percent

STA

filled

(%)

Approx.

propellant

loaded

mass (lbm)

Qty.

of

struts

Strain gage data for strut

loading at end of fill

Test Termination

/ Remarks

Strut ID Force ¶

(kips)

1 7/7/00 58.4 75,250 7 D-east + 12.0 High tension,

D-east strut

2 7/11/00 96.9 124,790 7 G-west + 13.0 High tension,

G-west strut

3 7/21/00 30.6 39,350 7 G-west + 8.0 G-west strut

drifting towards

high tension

4 8/4/00 78.5 101,020 8 B-east + 10.2

High tension,

B-east strut

B-west - 55.7

D-east + 4.4

D-west + 3.9

G-east - 23.5

G-west + 6.2

L-east - 28.5

L-west - 4.7

5 8/25/00 98.8 127,130 8 B-east - 37.0 All strut forces

were below max.

redline limit,

Tank filled OK to

normal operating

cap. probe level,

LTN2 = 22.7”

B-west - 22.1

G-east + 0.3

G-west + 0.6

J-east - 3.1

J-west - 8.2

L-east -20.9

L-west - 30.5

4B$ 10/24/00 96.9 190,680 8 B-east - 44.7 LO2 densifier

performance test

with LO2. STA

filled to PVT3

with LO2 inlet

temp = 121.3 oR

B-west - 41.6

G-east + 4.9

G-west + 0.4

J-east - 6.1

J-west -8.2

L-east - 33.2

L-west - 43.5

Notes: ‡ Test 4B was a densifier performance test conducted with LO2 and is shown for comparison purposes.

¶ Force conversions: 1 kip = 1,000 lbf = 4,448 newtons

Following the next two cryogenic load test attempts completed between 7/21/00 and

8/4/00, several issues were worked in parallel by the test operations team in order to help resolve

the inconclusive strain gage loading data that was obtained:

• STA strut strain gage recalibration with attached tank support members was completed.

NASA/TM—2010-216247 65
EAST WEST

tained Strut

• A redundant set of portable strain gage monitoring equipment was installed on all struts for

subsequent LN2 loading tests.

• Additional structural analysis cases were run by LMMSS including input geometry

reflecting the actual T153 support platform orientation.

• Strut angles, gaps and alignment, extended length, tank position relative to struts, and TSP

configuration relative to STA were all verified and were reset as necessary.

• Field readjustments of the struts were made based on direction from LMMSS test

engineers.

• A second “G” strut was added on the STA to increase the total number of support struts

from seven to eight for Test no. 4.

• After Test No. 4, the two D-struts were removed from the TSP and replaced with two

installed J-struts for Test no. 5 as shown in the figure 57 modified strut lay-out.

SOUTH

NORTH

Figure 57: Final as-tested STA eight strut configuration with alternate J-struts installed.

The above rework activities of the STA tank strut support system eventually resulted in a

successful tanking and detanking test. Following the J-strut change-over, the LN2 tank loading

test conducted at S40 on August 25th showed encouraging results as all eight struts yielded strain

gage data that were within the allowable stress limits (-65.7 kips, +11.0 kips) after tank filling to

the 98.8 percent level. Two contrasting data plots of STA strut force measurements as they had

developed during the 8/25/00 NBP LN2 loading test and a subsequent densified LO2 tanking

operation that was performed in late-October are presented in figures 58 and 59, respectively.

NASA/TM—2010-216247 66
Tension

AL

IF

Compression

iD

"UY

730000

755000

-40,000,

Tension

Compression IF

2

73,0000

-4,6060'

750000'.

NASA/TM—2010-216247 67
6.5 STA Boil-Off Testing

A single boil-off test was run with the STA filled with normal boiling point liquid

nitrogen and, then later on in the program while STA was filled with NBP LO2. The hardware

and tests were designed to measure the tank’s steady-state heat leak and provide LMMSS with an

important piece of information required for validation of their tank thermodynamic models. A

summary of the key boil-off test results for each fluid is presented in Table 10.0 below.

Table 10.0: STA boil-off test results summary.

Boil Steady Calc’d steady

Off Date Percent Test STA Liquid state boil- state heat leak

Test STA duration ullage temp. @ off mass

No. filled (min) pressure PVT-3 flow rate

Fluid

(%) (psia) (

oR) (lbm/sec) Btu/hr Btu/

hr fl2

1

8/25/00 98.8 130 14.4 139.8 0.112 34,540 32.6

LN2

2

10/26/00 99.2 204 14.4 162.8 0.140 46,250 43.7

LO2

6.5.1 LN2 Boil-Off Result

The LN2 boil-off test conducted with STA on 08/25/00 resulted in an experimental steady

state heat leak (Qenv) determination of 34,540 Btu/hr. The SS boil-off rate ( figure 60) during the

130 minute long test averaged 0.112 lbm/sec GN2. As later reported, the STA Qenv degraded ove

time due to spray-on

foam insulation (SOFI) Figure 60: STA tank boil-off test result - GN2 mass flow rate profile.

age-related problems 0.300 STA — Boil —Off Test

(figure 61) that had

developed. These 0.250

included mechanical

breakage, weathering,

cracking and moisture a 

0.200

penetration, all of which 3

resulted in extensive ice 0.150

formation on the tanks CU

exterior. When it (Qenv) 6 0.100 was measured again

during a similar LOX z

boil-off test as 0.050

described below, the

tank environmental heat 0.000

leak had increased by 0 30 60 90 120

33.9 percent. Time (min)

150

NASA/TM—2010-216247 68
STA Boil-Off

Test No. 2,

10/26/00 Test

Fluid: LO2

0.160

0.140

0.120

0.100

0.080

0.060

0.040

0.020

0.000

Figure 61: Ice formation and thermal performance loss on the X33 tank SOFI insulation

by mechanical breakage, weathering, cracking and moisture penetration.

6.5.2 LO2 Boil-Off Result

The LOX boil off test was conducted on 10/26/00 to reconfirm the experimentally

determined heat leak into the STA tank when filled with liquid oxygen in comparison to LN2. On

pre-run day (10/25/00), the STA initially contained LO2 at the PVT-10 diode elevation so that it

was completely chilled-down before boil-off testing was started. On Run-Day the tank was

topped-off from dewar N83 with NBP LO2 to the 28 inch liquid level point based on the BF

Goodrich capacitance probe output. The GO2 boil off vent flow rate was measured across a 2.12

inch ID orifice with

AP transducer Figure 62: STA tank boil-off test result - GO2 mass flow rate

XO2111. Tank profile.

pressure and gas

temperature at the

orifice run were

steady throughout the

test. The tank boil off

rate was recorded for

approximately 200

minutes. As data was

taken, the GO2 flow

rate, with the boil-off

profile shown in

figure 62, remained

constant indicating a

steady-state thermal

condition had been

NASA/TM—2010-216247

0 30 60

69

90 120 150 180 210

Time (min)
reached very quickly into the test.

Review of the test data indicated a heat leak much less than the LMMSS predicted value.

The original analytically predicted heat leak value was 130,600 Btu/hr for LO2. Based on an

average STA tank surface area of 1058 ft2, the calculated analytical heat flux was 123 Btu/hr-ft2.

The average STA tank boil-off rate measured during the S40 test was 0.140 lbm/sec GO2. Based

on saturated LO2 at 14.4 psia, the experimental boil-off rate converts to an average thermal heat

leak of 46,250 Btu/hr giving a test surface heat flux of 43.7 Btu/hr-ft 2

 which was 35.5% of

theoretical but 33.9% larger than the previous LN2 test result.

6.6 LN2 Performance Tests with LOX PDU

As mentioned earlier in the results summary, four PDU performance tests were conducted

with LN2 while five performance tests with LO2 were run with the X-33 densifier. One closedloop thermal stratification check-out test was completed with LN2 when the facility was still

configured for liquid nitrogen, and then in late-November following facility conversion to LOX,

four closed-loop recirculation tests were conducted with LO2. Detailed results of the PDU

testing with LN2 are provided in the next two sections below. These S40 test results reported on

include: 1) Performance testing with LN2 and subsequent loading of STA with DLN2, and, 2)

One closed-loop thermal stratification test with recirculating DLN2.

6.6.1 LN2 Performance Test Results – DLN2 Loading of STA

Liquid nitrogen densification check-out testing officially started at the S40 on September

22, 2000 and was completed by the first week of October. Table 11.0 provides a general run

summary of the LN2 performance tests completed during the LO2 PDU system check-out phase

of the program. All of the LN2 performance tests shown below went through to planned

completion and were without any of the “mid-run” aborts or out-of-limit shut-downs experienced

earlier during individual component check-out tests. At the end of each of these tests, the STA

was fully loaded with densified LN2 (DLN2). This was achieved in a 1.8 – 2.5 hour time period

depending on the DLN2 product outlet mass flow rate established. The STA had a final ullage

volume of 2 – 3 percent and contained up to approximately 132,000 pounds of densified and

thermally stratified LN2.

Table 11.0: Test summary – LN2 performance and closed-loop recirculation testing of LO2 PDU.

LN2 GN2 LN2 Outlet Test

Test ‡ Outlet Compressor Temp. Duration

No. Date Flow Set-Point from PDU Test Description

Range Pressure (

oR) LN2

Flow (lbm/sec) (psia) (min)

1A 9/22 8 – 20 2.2 120 122 LN2 flow into both Lobes.

2A 10/4 10 – 20 5.6 128 144 LN2 flow into both Lobes.

3A 10/5 10 – 20 3.6 125 151 LN2 flow into both Lobes.

4A 10/7 10 – 24 2.8 122 107 LN2 flow into both Lobes.

SA 10/8 9 – 18 2.8 121 198 Closed loop LN2 recirculation

flow into both Lobes

Note: ‡ Tests 1A – 4A were LN2 performance tests while test 5A was a thermal stratification closed-loop test with LN2.

NASA/TM—2010-216247 70
400

350

2 300

Q..

250

a^

a

E

a^

~ 200

150

100

0 50 100 150 200 250

The vertical temperature gradient was very steep in the upper quadrant of the STA tank

and typically ranged from 122 oR at the bottom to saturated LN2 at 151 oR and 30 psia near the

top liquid surface for runs 2A – 5A. As tank operating pressure was reduced, a lower vertical

temperature gradient would develop as shown in figure 63 for Test 1A which ended up stratified

from 121 oR at the STA inlet to 141 oR and 16 psia near the top liquid surface.

Figure 63: STA vertical temperature gradient during DLN2 loading test 1A.

Time (min)

The key objectives of the LN2 densification performance tests were primarily to evaluate

the GSE as a total integrated system and to also gain operating experience with the PDU equipment

and S40 facility before proceeding with the more hazardous liquid oxygen testing. Although the

densifier was designed to process LO2, analysis of the GSE equipment performance specifications

resulted in the following “nominal” target run condition ranges for the LN2 densification trials: 10 –

25 lbm/sec LN2 mass flow rate; 2.4 – 6.0 psia heat exchanger ullage pressure; and 8,000 – 9,500

rpm GN2 compressor operating speed. Table 12.0 indicates select steady-state experimental

performance test conditions run for each of the five LN2 densification runs completed during this

LN2 system check-out phase of the program. In all of the LN2 performance tests that were run, the

recirculation mass flow rate was “step-change” varied for test mapping purposes, and therefore, the

data as reported in Table 12.0 represents a stable and steady-state set of operating conditions at the

reported given mass flow and averaged over a discrete period of operating run-time.

NASA/TM—2010-216247 71
Table 12.0: Steady-state LN2 performance test data measurements with LO2 PDU.

Tag

ID

Description – PDU data Test ‡

1A

Test

2A

Test

3A

Test

4A

Test ¶

5A

FT535 LN2 recirc mass flow, lb/sec 16.19 19.83 10.31 23.64 14.13

TT530 Pump inlet temp, o

R 141.6 143.6 143.7 143.3 140.8

PT525 Pump inlet pressure, psia 67.5 34.1 47.8 28.7 34.3

TT545 Pump outlet temp, oR 141.6 144.7 144.9 144.1 141.5

PT540 Pump outlet pressure, psia 57.7 92.4 109.5 65.1 51.7

TT550 Stage 1 ht-exer, outlet temp, o

R 140.1 140.4 140.0 140.7 139.4

PT550 Stage 1 ht-exer, outlet press, psia 57.4 91.8 109.3 64.4 51.7

TT565 Stage 2 ht-exer, outlet temp, o

R 118.9 127.4 122.3 121.5 120.3

PT560 Stage 2 ht-exer, outlet press, psia 56.3 90.2 109.1 62.4 51.1

FT607 Heat exchanger bath fill, lb/sec 2.47 1.78 1.45 3.02 1.92

PT715 Stage 2 ht-exer, ullage press, psia 2.80 5.82 3.74 3.34 3.10

TT602A Stage 1 ht-exer, bath temp, oR 139.7 140.0 139.9 140.3 139.0

TT603A Stage 2 ht-exer, bath temp, oR 119.2 127.9 123.0 121.8 120.9

TT703A Stage 2 ht-exer, ullage temp, o

R 119.1 128.0 123.0 121.1 120.3

TT574 PDU skid outlet LN2 temp, o

R 120.0 128.5 124.9 121.9 121.1

FT715 Compressor vent flow, lb/sec 2.85 2.52 2.11 2.93 2.27

FT715S Compressor surge flow, lb/sec 0.63 0.81 0.73 0.0 0.35

SC715A Stage 1 speed, rpm 10,200 6,610 8,360 8,920 9,090

SC715B Stage 2 speed, rpm 10,510 6,800 8,610 9,190 9,370

SC715C Stage 3 speed, rpm 10,810 7,000 8,860 9,450 9,640

FC1 Stage 1 flow coefficient, (D1 0.285 0.258 0.235 0.325 0.260

FC2 Stage 2 flow coefficient, (D2 0.245 0.262 0.220 0.281 0.228

FC3 Stage 3 flow coefficient, (D3 0.198 0.249 0.198 0.238 0.197

PT715A Stage 1 inlet pressure, psia 2.21 5.60 3.59 2.78 2.80

TT715A Stage 1 inlet temp., o

R 129.1 151.3 138.2 131.4 133.8

PT715B Stage 2 inlet pressure, psia 4.72 7.96 6.11 5.16 5.30

TT715B Stage 2 inlet temp., oR 158.9 153.2 161.9 145.6 157.0

PT715C Stage 3 inlet pressure, psia 8.48 10.87 9.67 9.08 9.18

TT715C Stage 3 inlet temp., o

R 209.6 181.7 204.9 189.1 203.8

PT715D Stage 3 outlet pressure, psia 14.85 14.68 14.53 14.87 14.71

TT715D Stage 3 outlet temp., oR 260.7 204.5 244.4 230.7 248.2

N7113 Dewar N-71 LN2 total outflow, gal 2,533 2,485 3,038 2,808 6,150

XO8309 Dewar N-83 LN2 total outflow, gal 13,445 16,610 17,610 16,817 1,790

N/A GN2 compressor run time, min 184 193 205 155 321

N/A LN2 mass flow duration, min 122 144 151 107 198

N7117 Dewar N-71 pressure, psig 30.0 20.0 20.0 20.0 30.0

XO8311 Dewar N-83 pressure, psig 60.0 35.0 35.0 35.0 35.0

XO2103 STA ullage pressure, psia 16.0 30.0 30.0 30.0 31.0

N/A Approx. STA liquid fill volume, % 96.9 96.9 96.9 98.5 98.9

N/A STA uppermost diode wetted PVT3 PVT3 PVT3 PVT2 PVT2

Notes: ‡ LO2 pump was not operated due to shaft seal problem. LN2 flow during Test 1A was by AP transfer.

¶ Test 5A was the only closed-loop thermal stratification test conducted with LN2. Refer to Section 6.6.2.

NASA/TM—2010-216247 72
PT715D 3rd Stg Outlet

trr wrr r+^ra+w ri++W tea'

PT715C

—PT7 1

- PT71

— PT7

— PT7

1

1

PT715B LN2 Perfo

Test no.

10/7/0

rm

0

PT715A 1

st Stg Inlet

^^j

0 25 50 75 100 125 150 175

Time (min)

s oppeen-%j a

run. Reported in

16

Appendix F is one 14

complete data set

showing all graphical 12

test results for LN2

PDU performance test 10

no. 3A completed on C

October 5, 2000, this in 8

addition to STA LN2 a

loading data and post- 6

test LN2 resaturation

time-lines indicating 4

the warm-up rate of

propellant during a 2

24hr ground-hold.

5A

5B

5C

5D

ance

4A

Typical start-up transients and the resulting steady-state performance of the LO2 PDU

while operating with and producing densified LN2 (DLN2) are represented by the data given in

figures 64 through 67 for LN2 check-out Test No. 4A conducted on October 7, 2000. The

compressor start-up transient illustrated in figure 64 shows how the compressor speed would

spin-up, with each of the three stages accelerating at 900 rpm per minute. The rig then would

transition into an active pressure PID control mode at which point the speeds were regulated by

the PLC until the set-point inlet pressure was established as illustrated in the figure 65 interstage

compressor pressure profile. Figure 66 shows five characteristic constant LN2 mass flow rates

that were run during

Figure 64:GN2 compressor speed vs. time profile during LN2 performance test 4A. this particular test at 10,

15, 18, 21 and 24 10000

lbm/sec of LN2. After

completion of the 1.8

hour STA loading 8000

process with 122 oR

densified LN2 exiting 6000

the PDU, the initial E

warmer fluid layer in

the bottom of the tank 4000

was displaced upwards

by the colder and more

dense inlet LN2 as 2000

illustrated by the

vertical STA thermal

0

3

rd Stg

—SC715

1

st Stg

SC715A

LN2

Performance

Test no. 4A

10/7/00

— SC715A

— SC715B

— SC715C

temperature distribution

measurements (figure 0 25 50 75 100 125 150 175

67) at the point in time Time(min)

when the LN2 flow Figure 65:GN2 compressor interstage pressures during LN2 performance test 4A.

was t d t d fNASA/TM—2010-216247 73
25

20

U

N

N

a^ 15

3

0

CM

OUR 10

M

E

N

ZJ

5

mance

. 4A

00

FT535

Figure 66: LN2 mass flow rate data for LN2 performance test 4A.

0

0 25 50 75 100 125 150 175

Time (min)

Figure 67:STA LN2 vertical temperature gradient at end of DLN2 loading test 4A

PVT3 LN2

Performance

Test no. 4A

10/7/00

t = 148 min.

t PVT-x

PVT12

PVT 24

115

30 80 130 180 230 280

Height from Top (in)

The most significant results and conclusions based on the LN2 performance check-out tests

with respect to anticipated densifier unit performance with LO2 in the follow-on test series are

summarized by the following remarks and test result observations.

The 3.3 lbm/sec design point compressor GN2 mass flow rate could not be simulated or

achieved during either the previous GN2 compressor checkout tests or the LN2 performance

testing. Figure 68 indicates the “best” or maximum compressor outlet flow rate developed

during any single test to date which was approximately 3.0 lbm/sec. The three primary

155

150

145

140

135

CL

aEi 130

125

120

NASA/TM—2010-216247 74
Figure 69: Gaseous nitrogen temperature change from 2nd stage heat

exchanger ullage to GN2 compressor first stage suction inlet during LN2

performance test 4A.

Test no. 4A

10/7/00

— TT715A

TT715A Compressor Inlet TT720

TT703B

TT703B

HtX Ullage

Phase

Separator

TT720

0 25 50 75 100 125 150 175

Time (min)

180

160

CDE 140

H

120

100

contributing Figure 68: Compressor outlet GN2 mass flow rate during LN2performance test 4A.

causes for this 9.0 3.5

% mass flow

performance 3.0

reduction from the

intended design 2.5

point were: 1) the

high motor 2.0

winding

temperature issues 1.5

alluded to above 3

in Section 6.2;

0

1.0

2) the inability of z.

the Cryo-Mach 0.5

spare pump to

deliver 25 lb /sec lbm/sec .0

or more of LN2 0 25 50 75 100 125 150 175

which drives the Time (min)

boil-off rate; and,

3) the higher than expected GN2 temperatures at the inlet of the 1

st compressor stage. The inlet

gas temperature situation would be attributed to a combination of primarily higher than desired

SS thermal heat leak through compressor piping and the phase separator, and, to a lesser extent,

the very long duration thermal transient that would be required to reduce all the upstream metal

mass temperatures to lower values approaching the saturation temperature in the Stage 2

exchanger.

Maximum compressor

SS test inlet flow rate

—FT715

—FT715S

FT715 Compressor

Outlet Flow

Surge

bypass flow LN2

Performance

Test no. 4A

15S

The compressor did

exhibit start-up variation

tendencies depending on

upstream hardware and

metal wall starting

temperatures. Figure 69

illustrates a typical GN2

inlet temperature transient

with a final SS plateau of

132 oR in comparison to

the BN aerodynamic inlet

design value of 118 oR

entering the 1

st 

compressor

stage. It’s further noted that

in order to “thermally”

simulate the 2nd stage heat

exchanger boil-off rate for

LOX service and jointly

satisfy the real compressor

NASA/TM—2010-216247 75
design point inlet conditions with LN2 flowing through the exchanger tube-side, the required

LN2 mass flow would be 25 lb m/sec with a necessary AT across the exchanger of 22 oR. These

conditions were never achievable with the Cryo-Mach Pump and the BN GN2 compressor

operating together as a system in tandem.

In summary, as an outcome of the LN2 check-out tests, the maximum densifier

performance achievable was nominally 20 lbm/sec LN2 flow rate at a minimum compressor inlet

pressure set-point of 2.8 psia. The upper limit on LN2 flow rate was fixed by the maximum flow

rate capability delivered by the Cryo-Mach pump while the lower limit on compressor stage 1

inlet pressure was the lowest stable pressure that could be operated at without overloading the

drive motors, causing a VFD fault or shutting down on a surge instability event like the one

previously shown in figure 45. Scaled from the LO2:LN2 fluid density ratio, the corresponding

maximum LO2 flow rate expected would be 28 lb m/sec based on the resultant Cryo-Mach pump

performance assuming the same head requirement. These “as-tested” performance conditions,

specifically on the GN2 compressor and LO2 pump established the baseline conditions for the

subsequent runs to be performed with LOX.

6.6.2 LN2 Closed-Loop Thermal Stratification Test 5A Results

This section describes X-33 tanking results and the ensuing STA data obtained during the

single densified LN2 closed-loop thermal stratification test 5A that was run at the S40 on

October 8, 2000. The main objectives of the test were to evaluate densifier system performance

and verify the yet “un-tested” GRC developed operational procedures for densifying an 18,830

gallon batch of pre-loaded NBP LN2 inside the STA in a closed-loop recirculating mode.

Initially the Figure 70: STALN2liquid level during recirculation test 5A.

STA was pre-filled LN2 Recirculation

with NBP LN2 to a 30.0

nominal capacitance

probe liquid level of 25.0

22 inches. This

corresponded to an 20.0

approximate starting .5

mass of 127,400 lbm 15.0

of LN2 while the level

operating point would 10.0

be located in-between

diodes PVT1 and

PVT2. Tank level 5.0

control (figure 70)

w hLN2 00.

replenishment flow 0 30 60 90 120 150 180 210 240

control set-up and Time (min)

maintained by skid

control valve LCV-500 was satisfactory through-out the test. The STA ullage pressurization and

back-pressure control systems operated as designed and without control-related issues like

NASA/TM—2010-216247 76
overshoot or oscillation as the pressure was held at the desired nominal 30 psia set-point. The

GN2 compressor was started at an inlet pressure set-point of 2.8 psia and zero thermal load on

the exchanger tube-side (i.e. no LN2 mass flow). The total time required for compressor spin-up,

stage 2 heat exchanger ullage pump down to 3.1 psia and attainment of stable compressor

operation was at around 45 minutes following the start. The compressor stage speeds leveled out

at 9,090, 9,370 and 9,640 rpm for stages one through three, respectively. It’s noted that for

pressure balance control purposes, the speed ratios for the two down-stream stages were scaled

off the first stage at 1.03 and 1.06 times the first stage speed which was designated the “control

stage” in terms of inlet pressure and flow coefficient (0) management.

The fluid outlet syphon line was chilled and primed with LN2 and then the closed-loop

LN2 flow was initiated from STA thru the LOX densifier and back into STA. The Cryo-Mach

pump was set to run at a constant preset speed of 1,550 rpm and the head rise it provided was

18.0 psid. The LN2 outlet flow rate from the skid ( figure 71) was held approximately constant

during the test. It was nominally 14 lbm/sec while the flow was directed into both STA bottom

lobes. The LN2 replenishment flow rate (FT515) downstream of LCV-500 was constant at about

1.0 lbm/sec over a period of 146 minutes for STA make-up and level control. The recirculation

flow rate was stopped after about 200 minutes of LN2 flow time by shutting down the pump

when STA had reached thermal equilibrium per SS indications from silicon diode sensor

XO2305 found downstream from the 4 inch VJ outlet siphon of the tank. Facility LN2

temperature data in the primary LN2 recirculation flow loop including the inlet to STA

(XO2402), the outlet from STA (XO2305) and the return inlet temperature to the LOX skid

(XO0107) are indicated in figure 72. The vertical thermal stratification profile measurements

inside the STA during the complete recirculation and densification process are as shown in

figure 73. Additional data sets including tank lateral temperatures (figure 74) at three elevations

indicated that no radial

thermal gradients in excess Figure 71: LN2 recirculation and replenishment flow rate profile during test 5A.

of 1.0 oR AT had

developed during the 20.0

process. Based on an 18.0

approximate end-of-run 16.0

final bulk average

temperature of 123 oR, this y 14.0

depicted in figure 75 when 12.0

the recirculating flow was 10.0

stopped, indicated that the 8.0

final STA loaded mass N

was 133,700 pounds LN2,

Z 6.0

representing a 4.9 percent 4.0

mass increase. 2.0

Recirculation test #5A 0.0

represented the completion 0 30 60 90 120 150 180 210

of the planned LN2 Time (min)

performance check-out

testing to allow for facility conversion activities over to LOX test service.

LN2 Recirculation

Test no. 5A

10/8/00

NASA/TM—2010-216247 77
a y

i XO0107 14

PDU Inlet 'F

XO2402 STA Inlet .

145.0

140.0

2 135.0

2

m

E 

130.0

H

125.0

120.0

115

XO2402

XO2305

XO0107

Figure 72: Facility LN2 primary recirculation flow loop temperatures for test 5A.

150.0 LN2 Recirculation

XO2305 STA Outlet Test no. 5A

10/8/00

.0

0 30 60 90 120 150 180 210 240

Time (min)

Figure 73: STA vertical diode temperture profile during DLN2 recirculation test 5A.

150

145

140

0

135

a 130

Ea^

125

120

115

0 30 60 90 120 150 180 210 240

Time (min)

Figure 74: STA lateral diode temperatures at end of DLN2 recirculation test 5A.

PVT5

PVT10

PVT15

PVT21

PVT24

125.0

124.0

o 123.0

CL

C

122.0

121.0

120.0

80 120 160 200

Height from Top (in)

240

ASA/TM—2010-216247 78
Figure 75:STA LN2 vertical temperature gradient at end of DLN2 recirculation

test 5A indicating a thermally stratified tank at end of run.

LN2

125.0

124.0

^- 123.0

Su

CL

E 

122.0

H

121.0

120.0

30 80 130 180 230 280 330

Height from Top (in)

6.7 LO2 Performance Tests with LOX PDU

Following the LN2 system check-out tests of the PDU and S40 facility conversion from

LN2-to-LO2 which was completed on October 14th, liquid oxygen densification performance

testing began in mid-October 2000 and was finished by mid-November.

A total of five LO2 densification performance tests were executed at GRCs’ S40. Table

13.0 provides a general run summary of the experimental conditions for the five LOX densifier

performance tests carried out during this phase of the program. A closer review of the test results

summary table shows that of the five tests conducted, only Test 4B was completed as originally

planned in that the STA was fully loaded with densified LO2 by the end of run. Four LO2 PDU

performance tests with associated STA loading resulted in the following early terminations: Tests

1B and 2B – run abort for anomalous high facility filter AP downstream of the LO2 PDU; Test 3B

– automatic abort of GN2 compressor VFD by a fault shutdown due to a thermal relay overload;

Test 5B – intermittent LOX recirculation pump high over-current VFD fault shutdowns.

Table 13.0: Test results summary – LO2 performance testing of LO2 PDU.

Test No. Date

LO2

Outlet

Flow

Range

(lbm/sec)

GN2

Compressor

Set-Point

Pressure

(psia)

LO2 Outlet

Temp.

from PDU

(oR)

Test

Duration Test Description

LO2

Flow (min)

1B 10/14 10 – 14 2.8 121 96 LO2 flow into both Lobes.

2B 10/17 12 2.8 121 72 LO2 flow into both Lobes.

3B 10/20 10 – 16 2.8 121 138 LO2 flow into both Lobes.

4B 10/24 16 – 22 2.8 121 167 LO2 flow into both Lobes

5B 11/15 24 – 30 2.8 121 84 LO2 flow into both Lobes.

NASA/TM—2010-216247 79
It’s noted that the dew point of the STA system was verified prior to introducing LO2

flow for the first time. The results of the dew point test conducted on the STA tank was 31 ppm v

of moisture over a 1 hour test. This corresponded to a 398.8 oR (–61.2 oF) dew point which was

considered acceptable.

Table 14.0 shown below indicates select steady-state experimental performance

conditions for four of the five LO2 densification tests made during the LO2 system performance

phase of the program. In each of the LO2 performance tests conducted, the LOX recirculation mass

flow rate was varied for test mapping purposes, and therefore, the data as reported in Table 14.0

represents a stable and steady-state set of densifier operating conditions at the given mass flow and

were averaged over a discrete period of operating run-time. Even though four of five tests reported

herein resulted in early shutdown, valuable PDU performance operating data was obtained at LO2

mass flows from 10 – 20 lbm/sec. In addition, certain newly experienced problems associated with

the start of processing and producing densified LO2 were corrected prior to the final phase of the

test program with the LMMSS VentureStar tank involving closed-loop thermal stratification tests

with the STA using LOX. A discussion of significant points of interest for LO2 performance Tests

1 B – 4B are provided in the next four subsections below.

Table 14.0: Steady-state LO2 performance test data measurements with LO2 PDU.

Tag

ID

Description – PDU data Test

1B

Test

2B

Test

3B

Test

4B

FT535 LO2 recirc mass flow, lb/sec 10.10 11.94 14.15 20.05

TT530 Pump inlet temp, oR 148.8 158.5 165.5 165.3

PT525 Pump inlet pressure, psia 50.5 49.7 48.6 43.3

TT545 Pump outlet temp, oR 149.1 158.7 165.7 165.5

PT540 Pump outlet pressure, psia 77.6 76.8 73.3 66.2

TT550 Stage 1 ht-exer, outlet temp, oR 140.0 140.3 140.4 140.9

PT550 Stage 1 ht-exer, outlet press, psia 77.6 76.8 73.2 65.9

TT565 Stage 2 ht-exer, outlet temp, oR 119.7 119.8 119.7 120.3

PT560 Stage 2 ht-exer, outlet press, psia 77.3 76.2 72.5 64.6

FT607 Heat exchanger bath fill, lb/sec 1.41 1.56 1.75 2.08

PT715 Stage 2 ht-exer, ullage press, psia 2.99 3.01 2.98 3.10

TT602A Stage 1 ht-exer, bath temp, oR 139.8 139.8 140.0 140.4

TT603A Stage 2 ht-exer, bath temp, oR 120.5 120.4 120.3 120.8

TT703A Stage 2 ht-exer, ullage temp, oR 120.8 121.0 120.0 120.5

TT574 PDU skid outlet LO2 temp, oR 121.0 121.0 120.8 121.1

FT715 Compressor vent flow, lb/sec 2.13 2.12 2.24 2.43

FT715S Compressor surge flow, lb/sec 0.71 0.59 0.55 0.21

SC715A Stage 1 speed, rpm 9,290 9,290 9,350 9,230

SC715B Stage 2 speed, rpm 9,570 9,570 9,630 9,510

SC715C Stage 3 speed, rpm 9,850 9,850 9,910 9,780

FC1 Stage 1 flow coefficient, Φ1 0.242 0.243 0.253 0.272

FC2 Stage 2 flow coefficient, 02 0.218 0.220 0.227 0.243

FC3 Stage 3 flow coefficient, 03 0.189 0.192 0.196 0.208

PT715A Stage 1 inlet pressure, psia 2.82 2.80 2.80 2.79

NASA/TM—2010-216247 80
due to an anomalous 16.0

high AP across the 14.0

facility filter element

XO-0602 located 12.0

down stream of the

PDU and upstream of a 10.0

the STA inlet in a 4 8.0

inch section of VJ o

transfer line. An 6.0

excessively high J

back-pressure at

4.0

PT560 (skid outlet P) 2.0

resulted (figure 76)

0

LO2

Performance

4--- LO2 Flow

Test no. 1 B

FT535 FT535

PT560

Pressure----p.

PT560

LO2 Pump

Shut Down

Table 14: Steady-state LO2 performance test data measurements with LO2 PDU. (continued)

Tag

ID

Description – PDU data Test

1B

Test

2B

Test

3B

Test

4B

TT715A Stage 1 inlet temp., oR 132.2 138.7 133.3 140.0

PT715B Stage 2 inlet pressure, psia 5.44 5.44 5.43 5.45

TT715B Stage 2 inlet temp., oR 163.5 165.4 163.3 160.3

PT715C Stage 3 inlet pressure, psia 9.26 9.27 9.29 9.33

TT715C Stage 3 inlet temp., oR 214.1 217.0 214.6 209.2

PT715D Stage 3 outlet pressure, psia 14.74 14.75 14.91 15.08

TT715D Stage 3 outlet temp., oR 262.2 264.8 261.2 254.7

N7113 Dewar N-71 LN2 total outflow, gal 2,390 1,890 3,930 4,580

XO8309 Dewar N-83 LO2 total outflow, gal 6,150 4,620 9,450 17,920

N/A GN2 compressor run time, min 150 129 192 245

N/A LO2 mass flow duration, min 96 72 138 167

N7117 Dewar N-71 pressure, psia 44.7 44.7 44.7 44.7

XO8311 Dewar N-83 pressure, psia 49.7 49.7 49.7 49.7

XO2103 STA ullage pressure, psia 30.0 30.0 30.0 30.0

N/A Approx. STA liquid fill volume, % 30.6 39.2 47.7 96.9

N/A STA uppermost diode wetted PVT22 PVT21 PVT20 PVT3

6.7.1 LO2 PDU Performance Test 1B

The plans for this performance test were to initially run at an LO2 slow-fill flow rate of

10 lbm/sec and then incrementally increase to a fast-fill rate of 20 lbm/sec. During the course of

the test, the LO2 pump was manually shut down early after only 96 minutes into the slow-fill

flow portion of the

STA loading. A Figure 76: LO2 flow rate and skid outlet pressure - test abort high facility filter

problem occurred differential pressure.

160

140

120 ..

m

100 2N

80 2

60 0

0

40 

a

20

due to a plugged or .0 0

clogged facility filter 0 25 50 75 100 125

Time (min)

element in the LOX

transfer line between

NASA/TM—2010-216247 81
the skid and STA. This began to restrict the free flow of LOX from the PDU into the STA tank.

The abort shutdown occurred after DLO2 crossed the STA vertical diode PVT22 resulting in a

final STA loading of only approximately 5,800 gallons of LOX in the tank.

6.7.2 LO2 PDU Performance Test 2B

Liquid oxygen performance Test no. 2B had also resulted in an abort, early into the run

due to the same anomalous high ∆P condition causing loss of DLO2 flow (figure 77) across the

facility filter element. This occurred after only 72 minutes of DLO2 flowing time. GRC research

engineers began an investigation into the cause of these two recent early and un-explainable run

aborts by what appeared to be “filter clogging”. It was hypothesized that the apparent viscosity of

DLO2 was significantly increased at the lower 120 oR subcooled outlet temperature and this was

causing the high

filter element Figure 77: LO2 flow rate and skid outlet pressure - test abort high facility filter

differential differential pressure - Test 2B.

pressure. This was

compounded by 14 0

the fact that the

filter element 12.0

specified by

LMMSS had a 10.0

very small pore

size distribution. _- 8.0

To resolve the 3

problem and N

6.0

continue on with 4.0

testing, the 10 μm

filter element on 2.0

XO-0602 was

removed and 0.0

6.7.3 LO2 PDU Performance Test 3B

The LO2 performance Test #3B conducted on October 20th began very well, as stable

operating conditions were maintained through the first three test mass flows. The plan was to

conduct an STA fast-fill loading test with both the LOX pump running and compressor operating

at a set-point of 2.8 psia ullage pressure. The LOX flow rate would be incrementally increased

from 10 – 20 lbm/sec with each mass flow rate time continued for a time increment of about 30

90

80

70

60

50 y

40 6

30 0

IL

20

10

0

replaced with a 0 20 40 60 80 100 120 140 160

300 μm (50 mesh) Time (min)

SS in-line basket

strainer inside of the original VJ filter element housing. This facility modification effectively

solved the problem as the operating ∆P across the course strainer was reduced to a more normal

range of 2 – 3 psid during subsequent DLO2 performance tests as discussed below. This

hardware fix allowed test operations to proceed, but it did not provide any further insight into the

true reasons behind these high ∆P events across the filter.

NASA/TM—2010-216247 82
minutes. Figure 78 indicates the “flatness” of the LO2 temperature profile as it flowed through

the PDU heat exchanger train and became densified. After 19 minutes of operating time at the 16

lbm/sec LO2 flow rate point, an unexpected fault shut-down occurred on the stage-two

compressor VFD resulting in an early termination of the test. A restart was not possible, so after

the S40 facility was secured, a site entry was made and the problem was diagnosed as a

previously un-experienced thermal relay overload with a VFD stage-two fault. This problem was

subsequently corrected by a simple adjustment of the cabinet set-point temperature on the VFDs’

electrical enclosure air-conditioning unit designed to maintain the enclosure temperature normal.

Figure 78: LO2 stream temperatures across two-stage heat exchanger system.

180 LO2 18

Performance

170 1

st Stg Inlet

Test no. 3B

10/20/00 16

160 LO2 Flow

14

FT535 12 Q_ 150 n

Z 2nd Stg Inlet TT550 10 S

aa) 140 E 8 0

0 130 N

6

J 2nd Stg Outlet TT565

120 TT545 4

TT550

110 TT565 2

FT535

100 0

0 25 50 75 100 125 150 175

Time (min)

6.7.4 LO2 PDU Performance Test 4B

Near total success was finally realized during LO2 PDU performance Test 4B run with

LO2 mass flows ranging from 16 – 22 lbm/sec. In this test and for the first time during the

program the STA was fully loaded with DLO2 as testing went through the full planned duration.

During LO2 performance Test No. 4B conducted on October 24, 2000, some of the key measured

start-up transients and resulting steady-state performance of the LO2 PDU while operating with and

producing densified LO2 are presented in figures 79 through 84.

The GN2 compressor start-up and operating speed transient ( figure 79) resulted in final

stage steady-state speeds cruising in-between 9,230 and 9,780 rpm. Given the now very well refined

compressor start-up process, the resulting interstage pressure pump-down transient (see figure 80)

to go from an atmospheric pressure ullage to 2.8 psia required 38 minutes of run time and the

overall performance compression ratio was 5.4:1. Motor stator winding temperatures on the rig

leveled out at 200 – 210 oF and showed no further sign of increase while motor currents varied from

45 – 55 amps during test. The compressor flow coefficient (0) history given in figure 81 illustrated

the complexity of the dynamics for both the compressor start-up and normal operation. The authors

point-out two interesting features of the flow coefficient data-set: 1) the surge avoidance controller

was very reactive during the first 95 minutes of the run, this necessary to maintain the Stage 1 inlet

NASA/TM—2010-216247 83
12000

10000

8000

E

i?

6000

c.

U)

4000

2000

0

0 50 100 150 200 250

Time (min)

Figure 80: Compressor interstage pressure profile - LO2 performance test 4B.

16.0 3

rd Stg Outlet

PT715D

14.0

LO2 PT715D

Performance PT715C

12.0 Test no. 4B

10/24/00

PT715B

PT715A I

v 10.0

PT715C

N

^ 8.0

EL

6.0 A

PT715B

4.0 1

st Stg Inlet

PT715A

2.0

0 50 100 150 200 250

Time (min)

Figure 81: Compressor'floy ,coefficient profile,during L62 performance test 4B.

Figure 79: Compressor stage speeds during LO2 performance test 4B.

01 above the controllers set-point

value of 0.18 to prevent a surge

shut-down at 0.12; and 2) the

discrete step-changes seen with

each of the stages (D as the LO2

mass flows were changed, thereby

reflected the gradual increase in

compressor mass flow throughput that varied from 1.8 – 2.5

lbm/sec GN2 vent rate over the

test range of LOX flows.

As in previous tests the

LO2 test mass flow rates as

shown in figure 82 were

manually controlled, in this

case by running the Cryo-Mach

LO2 pump at a constant speed

of 1,540 rpm and then

throttling the LO2 skid control

valve (FCV-555) from 67 – 84

percent open at maximum flow.

During this test, DLO2 was

produced at constant and steady

outlet conditions of 121 o

R and

65 psia exiting the skid. The

consumables transferred from

LN2 dewar N-71 and the LO2

supply dewar N-83 are

provided in figure 83.

Approximately 4,600 gallons of

LN2 were consumed during the

thermodynamic venting process

to subcool nearly 171,000

pounds of DLO2. The STA

vertical temperature profile

changes that took place and the

ultimate thermally stratified

condition of the LOX during the

course of the densification and

loading process is indicated in

figure 84.

NASA/TM—2010-216247
Figure 82: Densified LOX flow rate - LO2 performance test 4B.

LO2

Performance

Test no. 4B

10/24/00

FT535

LO2 Pump

25.0

20.0

U

N

15.0

3

0

N 10.0

O

J

5.0

0.0 i I'

0 50 100 150 200 250

Time (min)

Figure 83: Dewars N83 and N71 volume change during LO2 performance test 4B.

24000

21000

18000

m

9 15000

N

E

6 12000

`m

0 9000 q

6000

3000

0

LO2

Performance

Test no. 4B

10/24/00

LO2 Dewar N-83 —XO8309

XO8309 N7113

LN2 Dewar N-71

N7113 \

 1i

0 50 100 150 200 250

Time (min)

Figure 84: STA vertical diode temperature profiles - LO2 performance test 4B.

LO2 PVT5 200 Performance

Test no. 4B

10/24/00

PVT10

PVT15

PVT5

PVT21 —PVT1

PVT1

PVT24

PVT2

PVT2

180

92.

Su

cD 160

n

E

S

OJ

140

120

0 50 100 150 200 250

Time (min)

0

5

1

4

NASA/TM—2010-216247 85
6.8 STA Closed-Loop Thermal Stratification Testing with LO2

The last Phase of the S40 program was started in late-November and culminated with

four closed-loop LOX thermal stratification tests completed by December 5, 2000. These

particular tests and the corresponding test matrix were conducted under a collaboration with

GRC and the LMMSS. Table 15.0 indicates the general PDU performance results summary for

each of the test conditions that were run. With respect to specific LO2 densification unit

performance, all of these tests, with the exception of Test # 4C that was run at the nominal LO2

design flow rate of the rig, were very similar in performance to the previously discussed LO2

Test 4B at the 20 lbm/sec operating point. Some mention will however be made of the densifier

performance findings while conducting Test 4C which was very close to the nominal GSE design

point value of 30 pounds per second of DLO2 production. Additional test data obtained during

these runs are reported in Appendix G.

Table 15.0: Test results summary – LO2 closed-loop thermal stratification testing of LO2 PDU.

LO2 GN2 LO2 Outlet Test

Test No. Date Outlet Compressor Temp. Duration Test Description

‡

Flow Set-Point from PDU LO2 (lbm/sec) Pressure (

oR) Flow (psia) (min)

1C 11/18 20 2.8 121 230 Closed loop LO2 recirculation

flowing into both Lobes

2C 11/22 21 - 22 2.8 121 231 Closed loop LO2 recirculation

flow in un-instrumented Lobe

3C 11/30 21 2.8 120 230 Closed loop LO2 recirculation

flow into instrumented Lobe

4C 12/5 28 – 30 2.8 121 - 122 190 Closed loop LO2 recirculation

flow into both Lobes.

Note: ‡ Cryo-Mach LO2 back-up pump was used for all four LOX thermal stratification tests.

For all the test matrix runs per Table 15.0, densified fluid inlet temperature to the STA

from the LO2 PDU was controlled between 120 – 122 °R. This inlet LO2 temperature

corresponded to a second stage heat exchanger ullage pressure of 2.8 psia. Table 16.0 shown

below indicates select steady-state experimental performance conditions for each of the LO2

closed-loop thermal stratification tests made during this final phase of the program.

6.8.1 STA LO2 Closed Loop Thermal Stratification – Test 1C

A closed loop thermal stratification test with LO2 was conducted on the morning of

11/18/00. The STA was first loaded with NBP LO2 and then the tank was topped off to its

normal operating liquid level on the capacitance probe. The GN2 compressor was started-up at

08:42 with no heat load on the LO2 heat exchangers. The compressor was operated at an inlet

pressure set-point of 2.8 psia. After stabilization of the GN2 compressor suction/discharge

operating conditions, the LO2 pump was started at 09:55. The LO2 pump was set-up to run at

1500 rpm with skid control valve FCV-555 adjusted to about 87% open which provided a

nominal LO2 mass flow rate of 20 lb/sec into the STA.

NASA/TM—2010-216247 86
Table 16.0: Steady-state LO2 performance test data measurements with LO2 PDU

during closed loop thermal stratification testing.

Tag

ID

Description – PDU data Test

1 C

Test

2C

Test

3C

Test

4C

FT535 LO2 recirc mass flow, lb/sec 20.1 22.0 21.5 28.4

TT530 Pump inlet temp, oR 126.7 126.3 126.5 127.1

PT525 Pump inlet pressure, psia 35.4 35.9 35.6 30.4

TT545 Pump outlet temp, oR 127.0 126.4 126.7 127.3

PT540 Pump outlet pressure, psia 60.7 60.4 60.6 59.3

SC535 LOX pump speed, rpm 1516 1516 1516 1704

TT550 Stage 1 ht-exer, outlet temp, oR 131.5 131.1 131.3 131.2

PT550 Stage 1 ht-exer, outlet press, psia 60.3 60.1 60.2 58.4

TT565 Stage 2 ht-exer, outlet temp, oR 120.1 120.1 120.3 121.1

PT560 Stage 2 ht-exer, outlet press, psia 59.2 58.5 58.9 56.2

PT709 Stage 2 ht-exer, ullage press, psia 3.20 3.22 3.21 3.42

TT602A Stage 1 ht-exer, bath temp, oR 132.1 131.7 131.9 132.1

TT603A Stage 2 ht-exer, bath temp, oR 120.5 120.7 120.6 121.4

TT574 PDU skid outlet LO2 temp, oR 120.7 120.9 120.8 121.5

FT715 Compressor vent flow, lb/sec 2.06 2.02 2.04 2.31

PT715A Stage 1 inlet pressure, psia 2.81 2.81 2.80 2.77

TT715A Stage 1 inlet temp., oR 133.7 135.7 134.7 131.0

PT715D Stage 3 outlet pressure, psia 14.55 14.56 14.57 14.48

XO2103 STA ullage pressure, psia 29.9 29.9 29.9 30.1

LT02 STA capacitance probe level, inch 24.1 25.9 23.2 25.9

XO2102 STA vent gas temp., oR 446.4 423.9 345.8 405.5

XO2302 STA siphon outlet pressure, psig 12.7 12.5 12.6 11.5

XO2305 STA siphon outlet temp., oR 125.4 125.1 125.1 126.3

PLT1 STA internal temp. lateral, 98”, oR 123.2 123.0 123.0 124.2

PLT5 STA internal temp. lateral, 98”, oR 123.0 123.0 123.0 124.2

PLT6 STA internal temp. lateral, 160”, oR 122.3 122.1 122.2 123.6

PLT10 STA internal temp. lateral, 160”, oR 121.8 121.8 121.8 123.0

PLT11 STA internal temp. lateral, 218”, oR 121.2 121.2 121.3 122.5

PLT15 STA internal temp. lateral, 218”, oR 121.2 121.2 121.3 122.5

PVT1 STA internal temp. vert., 14”, oR 292.3 283.3 258.0 270.5

PVT2 STA internal temp. vert., 28”, oR 168.8 167.4 168.8 167.8

PVT3 STA internal temp. vert., 44”, oR 124.4 124.4 124.1 125.3

PVT5 STA internal temp. vert., 50”, oR 124.4 124.2 124.1 125.1

PVT10 STA internal temp. vert., 80”, oR 123.5 123.3 123.2 124.2

PVT15 STA internal temp. vert., 134”, oR 122.6 122.4 122.4 123.6

PVT18 STA internal temp. vert., 170”, oR 121.8 121.6 121.9 123.2

PVT21 STA internal temp. vert., 212”, oR 121.2 121.3 121.5 122.7

PVT24 STA internal temp. vert., 278”, oR 120.9 121.2 120.7 122.1

N/A GN2 compressor run time, min 314 286 288 245

N/A LO2 mass flow duration, min 230 228 230 190

N/A Approx. STA liquid fill volume, % 98.8 98.6 98.8 98.6

N/A STA uppermost diode wetted PVT2 PVT2 PVT2 PVT2

Test 1 C: Steady state data points @ t = 200 minutes, 1:05 pm, row 4982

Test 2C: Steady state data points @ t = 200 minutes, 3:00 pm, row 2702

Test 3C: Steady state data points @ t = 200 minutes, 6:25 pm, row n/a

Test 4C: Steady state data points @ t = 150 minutes, 12:30 pm, row 902

NASA/TM—2010-216247 87
Recirculation of densified LO2 continued during Test 1 C until steady state temperatures

were achieved. Steady-state was defined to occur when the STA siphon outlet temperature at

diode XO2305 stabilized with respect to fluid inlet temperature at diodes XO2402/XO2502 and

this AT reached a minimum and steady condition. The LO2 inlet temperature entering the STA

through both lobes was a constant 120 oR. A steady-state stratification condition ( figure 85) was

eventually attained within STA after approximately 200 minutes (3.3 hrs) of closed-loop LO2

recirculation. During the test the following pressure conditions were maintained: 30 psia STA; 45

psia N-71; and 50 psia N-83. Upon completion of the test, the STA was drained back to diode

PVT-10 and the remaining sub-cooled LO2 was held in STA to allow the fluid to re-saturate to

original NBP conditions by natural heat-leak into the system. This operational scenario was

typical for all subsequent LO2 recirculation tests performed with STA for these runs.

Figure 85: STA thermal stratification temperature profiles with circulating LOX - Test 1 C.

180

170

160

e..

150

a)

a

E

a)

~ 140

130

120

LO2 Thermal

Stratification

Test no. 1C

11/18/00

STA outlet

PVT15

PVT21

PVT24

0 50 100 150 200 250

STA Inlet Time (min)

6.8.2 STA LO2 Closed Loop Thermal Stratification – Test 2C

The second closed loop thermal stratification test with LO2 was conducted on the morning

of 11/22/00. The conditions for this test were the same as Test No. 1C with the exception of the

STA inlet flow path. Densified oxygen was directed to flow into STA through the un-instrumented

lobe which is across valve XO-2403. Total time of LO2 recirculation flow ( figure 86) at 20 lb/sec

during this test was 223 minutes with LO2 entering the STA nominally at 121 oR. A steady-state

thermal condition (figure 87) was observed within STA after approximately 200 minutes (3.3 hrs)

of closed-loop LO2 run time.

NASA/TM—2010-216247 88
Figure 86: STA inlet DLO2 flow rate and STA tank LOX make-up rate.

25

0

FT535 DLO2 Recirc Flow

LO2 Thermal

Stratification

Test no. 2C

11/22/00

FT535

• FT515

FT515

LOX Make-Up Flow

­.-r, ' Mn A-!Mn.

0 50 100 150 200 250

Time (min)

Figure 87: STA thermal stratification temperature profiles with circulating LOX - Test 2C.

20

v

15 30

ca

E 10

N

0J

5

180

LO2 Thermal

Stratification

Test no. 2C

170 11/22/00

STA outlet

160

PVT15 2

12 150

a)

CLE PVT21

~ 140

130

PVT24

120 0 

'Lr STA Inlet 50 100 150 200 250

Time (min)

6.8.3 STA LO2 Closed Loop Thermal Stratification – Test 3C

This LO2 closed-loop recirculation test began late in the day of 11/30/00. The GN2

compressor was first brought on-line at 14:18 and it ran smoothly on the very first start-up

attempt. Liquid oxygen recirculation flow was started at 15:18 at a 20.5 lb/sec mass rate. The

flow was through the STA inlet valve XO-2503 which was on the instrumented side of the tank.

The STA liquid level controller had very accurately maintained liquid level at typically a 24.6

inch set-point for this test (figure 88) as well as during previous runs. The LO2 inventory in N83

was however marginal, and the test was continued as planned until N-83, that was used for

providing make-up LO2, was drained empty. When this occurred, the LOX make-up supply

valve (LCV-500) was closed at 17:29 and the test proceeded, allowing STA liquid level to

slightly drop by 2 inches below its set point. The GN2 compressor was shutdown at 19:05 and

NASA/TM—2010-216247 89
180

170

2 160

12 150

a)

CL

E

140

130

120

0

STA Inlet

50 100 150 200 250

Time (min)

LO2 Thermal

Stratification

Test no. 3C

11/30/00

STA outlet

PVT15

PVT21

PVT24

the LO2 pump was stopped at 19:06. The final test operation was a drain-back of STA to just

below diode PVT-10 and the S40 facility was secured. End-of run temperature conditions ( figure

89) for this test were similar to the previous two runs.

Figure 88: STA liquid level capacitance probe data with recirculating LOX - Test 3C.

30.0

25.0

r LL1

U

20.0

a4.

f6U

V

15.0

a^

a^

m

10.0 LO2 Thermal

Stratification

a

Test no. 3C

11/30/00

5.0

0.0

0 50 100 150 200 250

Time (min)

Figure 89: STA thermal stratification temperature profiles with circulating LOX - Test 3C.

6.8.4 STA LO2 Closed Loop Thermal Stratification – Test 4C

On 12/5/00 the GRC Propellant Densification Test Operations Team completed the final

test of the matrix with a 30 lbm/sec closed-loop LO2 recirculation run. The GN2 compressor was

successfully ramped-up at 09:16 with no heat load on the LO2 heat exchangers. At approximately

09:50, the pressure at the inlet to the compressor had stabilized and reached 2.8 psia. The CryoNASA/TM—2010-216247 90
180

170

160

Q..

150

Q

CL

EQ

~ 140

130

120

50

ST A Inlet

Mach LO2 pump was started at 10:08 and was operated between 1750 – 2000 rpm with skid

outlet LOX control valve FCV-555 100% wide open to achieve the target 30 lbm/sec test flow

rate. Due to high current loads at the increased mass flow rate, the LO2 pump was incapable of

sustained operation at 2000 rpm (30 lbm/sec), and so, the recirculation flow rate was slightly

reduced to 28 lbm/sec to avoid a nuisance over-current shutdown. The facility dewar systems, the

LO2 densification skid and the STA ullage pressures ( figure 90) were all controllable and

remained steady throughout the test. A steady-state thermal condition ( figure 91) was achieved

within STA after approximately 160 minutes (2.7 hrs) of closed-loop LO2 recirculation. A

controlled shutdown of the LO2 pump and GN2 compressor occurred at 13:18 to conclude the

run. The facility was

then secured and the Figure 90: STA ullage pressure during LO2 thermal stratification test 4C.

STA was drained back 35.0

to from diode PVT2 to

PVT10 to allow the

subcooled LO2 to 30.0

recondition to its NBP.

Figure 92 shows a

typical LOX re- ; 25.0

N

saturation temperature a

profile as the densified

propellant warmed up 20.0

to 162 oR inside the

STA over a 44 hour

perido 15 0

Time (min)

Figure 91: STA thermal stratification temperature profiles with circulating LOX - Test 4C.

LO2 Thermal

Stratification

XO2103 Test no. 4C

12/05/00

Drain back

to PVT10

Press'n

.

II

I

0 50 100 150 200 250

NASA/TM—2010-216247 91
Figure 92:STA LO2 resaturation temperature vs time - densified propellant heat-up.

180 -

170 -

160

12 150

N

CL

E

N

~ 140

130 -

120 -

NBP LOX 162 oR

PVT10

PVT10

PVT24 PVT15

PVT18

PVT15 PVT21

PVT21 PVT24

DLOX @ 124 oR

0 5 10 15 20 25 30 35 40 45

Time (hr)

7. CONCLUDING REMARKS

A liquid oxygen propellant densification unit was designed, built and tested at the NASA

Glenn Research Center (GRC). The steady state demonstration and performance test series was

conducted with the densifier to simulate LO2 propellant tank loading, recirculation and thermal

stratification of the liquid oxygen loaded inside of a flight weight tank. The X33 scale LO2

densification unit was designed to process subcooled cryogen at a nominal rate of 30 pounds per

second. The densification process subcools NBP LO2, thereby effectively lowering the

temperature of the fluid from 168 oR down to an outlet product temperature of 120 oR.

Test operational and performance goals with the 30 lbm/sec LO2 densifier were

successfully demonstrated during the course of the program. With the STA tank volume at

around 20,000 gallons, the initial loaded mass of NBP LO2 inside of STA at the onset of the

densification process was approximately 180,200 pounds. Following completion of the 20 – 30

lbm/sec densification flow testing, experimental results indicated that by the end of the process

and based on an average bulk measured temperature of 123 oR, the final loaded mass of LO2 was

approximately 196,300 pounds. This additional loaded mass of 16,100 pounds represented on

average an 8.9 percent increase in on-board LO2 propellant. Test results confirmed the presence

of thermally stratified oxygen layers inside the tank. These layers varied in the vertical direction

from 122 oR for the colder, denser fluid at the bottom to 166 o R for the warmer less dense liquid

oxygen near the top outlet of the STA tank.

NASA/TM—2010-216247 92
Other significant conclusions and lessons learned resulting from these tests were the following:

• The design-point temperature of the LO2 densification unit was demonstrated at the 20 lb/sec

LO2 outlet mass flow rate. The outlet temperature at the higher flow test of 28 – 30 lb/sec

was below the target but within +2 oR of the 120 o R design outlet temperature of the rig.

• The temperature performance condition noted above was correctable. With appropriate GN2

compressor coolant-system modifications, the compressor could have the capability to run at

slightly lower inlet pressure settings than GRC was able to operate during the LMMSS tests.

• STA densification times to reach steady state were 190 – 210 minutes for the first three closedloop thermal stratification tests run at 20 lb/sec LO2 mass flow rate. For the higher flow rate

test at 28 lb/sec, the densification time-line was proportionately reduced to approximately 160

minutes.

• Based on a known tank volume and level, the initial loaded mass of NBP LO2 inside of STA

at the onset of the densification process was approximately 180,200 pounds for all tests. At

the end of run using an average measured test bulk temperature of 123 oR, the final calculated

loaded mass was around 196,300 pounds. This loaded mass differential becomes 16,100

pounds which represented an 8.9% increase in on-board LO2 propellant.

• The densified LO2 inlet flow-path into the STA lobes had no noticeable affect on fluid

thermal conditions inside the tank. No radial temperature gradients were evident from the

STA test data.

The experimental goals of the test program were satisfactorily achieved. The liquid oxygen

closed-loop recirculation testing had demonstrated three very key technologies:

• The feasibility of high-volume LOX densification production operations.

• Establishing the syphon line outlet flow and top-to-bottom recirculation of LO2 during

test operations was successful.

• Thermal stratification conditions were achievable in a flight-weight LO2 propellant tank

using this unique processing method.

Throughout the course of the test program, GRC had produced in excess of 150,000 gallons

of 120 oR densified LO2. This included the combined GRC LO2 densifier performance testing

and the closed-loop recirculation tests that would typify an on-the-pad loading operation. During

LN2 performance checkout tests of the LO2 densifier systems, over 200,000 gallons of densified

LN2 at 120 oR was produced as well.

NASA/TM—2010-216247 93
8. REFERENCES

1. Tomsik, T. , "Performance Tests of a Liquid Hydrogen Propellant Densification Ground

System for the X33/RLV", NASA TM 107469, AIAA-97-2976, July 1997.

2. McIntosh, G. E., Stochl, R. J., and Tomsik, T. M., “Liquid Hydrogen Densification Heat

Exchanger”, Adv. Cryogenic Engr., Vol. 43, Plenum Press, New York, 1997.

3. Jurns, John, Tomsik, Thomas and Greene, William, “ Testing of Densified Liquid

Hydrogen Stratification in a Scale Model Propellant Tank”, 1999 Cryogenic Engineering

and International Cryogenic Materials Conference, Montréal, Québec, Canada., (NASA

TM 2001-209391).

4. Bailey, T., Vandekoppel, R., Skardtveldt, G., and Jefferson, T., " Cryogenic Propellant

Stratification Analysis and Test Data Correlation”, AIAA Journal, Vol. 1, Number 7,

pp.1657-1659.

5. Greene, W. D., Tomsik, T. M., and Knowles, T. E., "Propellant Densification for Launch

Vehicles: Simulation and Testing”, AIAA-99-2335, June 1999.

6. Greene, William and Vaughan, David, “Simulation and Testing of In-Tank Propellant

Densification For Launch Vehicles,” AIAA-98-3688, July 1998.

7. Lak T., Lozano, M., and Tomsik, T. M., "Advancement in Cryogenic Propulsion System

Performance through Propellant Densification ", AIAA-96-3123, July 1996.

8. Lynn, E., and Graham, B., “Effect of Propellant Densification on Winged-Body RLV

Weight”, NASA MSFC, October 10, 1995.

9. Haberbusch, M. S., “Study Task for Determining the Effects of Boost Phase Environments

on Densified Propellants Thermal Conditions for Expendable Launch Vehicles”, NASA

CR– 2002–210808, April 2002.

10. Tomsik, T. M., "Recent Advances and Applications in Cryogenic Propellant

Densification Technology", NASA TM-2000-209941, March 2000.

11. Fazah, M. M., "STS Propellant Densification Feasibility Study", NASA Technical

Memorandum 108467, September 1994.

12. Brentani, E. G., and Smith, R. V., “Nucleate and Film Pool Boiling Design Correlations

for O2, N2, and H2 and He”, Adv. Cryogenic Engr., Vol. 1 0B, Plenum Press, New York,

1965.

13. Giarratano, P. J., and Smith, R. V., “Comparative Study of Forced Convection Boiling

Heat Transfer Correlations for Cryogenic Fluids”, Adv. Cryogenic Engr., Vol. 11, paper

H-1, pp. 492– 506, Plenum Press, New York, 1965.

14. Anthony, Miranda and Greene, William, "Analytical Model of an Existing Propellant

Densification Unit Heat Exchanger", AIAA-98-3689, July 1998.

NASA/TM—2010-216247 94
APPENDIX A

LO2 PDU TEST ARTICLE

INSTRUMENTATION

NASA/TM—2010-216247 95
APPENDIX A – LO2 PDU TEST ARTICLE INSTRUMENTATION

Channel ID

Description Range Location

Type ID Number Limits Units Facility Densifier STA

ET C715A_Volt Stage 1 Compressor Motor Voltage 0 - 500 volt X

ET C715B_Volt Stage 2 Compressor Motor Voltage 0 - 500 volt X

ET C715C_Volt Stage 3 Compressor Motor Voltage 0 - 500 volt X

FT FT515 Replenish LO2 Mass Flow Rate 0 - 3.1 lb/sec X

FT FT535 LO2 Pump Discharge Mass Flow Rate 0 - 30 lb/sec X

FT FT607 Stage 2 Exchanger LN2 Make-Up Flow Rate 0 - 5.6 lb/sec X

FT FT715 gN2 Compressor Vent Mass Flow Rate 0 - 3.3 lb/sec X

FT FT715S gN2 Surge Mass Flow Rate to Stage 2 Exchanger 0 - 1.8 lb/sec X

FXQ C715A_VolQ Stage 1 Compressor Outlet Volume Flow Rate 0 - 3000 cfm X

FXQ C715B_VolQ Stage 2 Compressor Outlet Volume Flow Rate 0 - 3000 cfm X

FXQ C715C_VolQ Stage 3 Compressor Outlet Volume Flow Rate 0 - 3000 cfm X

IT C715A_Amps Stage 1 Compressor Motor Current 0 - 150 amp X

IT C715B_Amps Stage 2 Compressor Motor Current 0 - 150 amp X

IT C715C_Amps Stage 3 Compressor Motor Current 0 - 150 amp X

LT LT615 Stage 2 Heat Exchanger LN2 Bath Level 0 - 51 inch X

LT LT620 Stage 1 Heat Exchanger LN2 Bath Level 0 - 60 inch X

PDT PDT502 Differential Pressure across LO2 Filter F-502 0 - 5 psid X

PDT PDT522 Differential Pressure across LO2 Filter F-522 0 - 5 psid X

PDT PDT630 Differential Pressure across LN2 Filter F-630 0 - 5 psid X

PT PT505 Facility LO2 Make-Up Pressure to Densifier 0 - 115 psia X

PT PT525 LO2 Pump Inlet Pressure 0 - 115 psia X

PT PT540 LO2 Pump Outlet Pressure 0 - 115 psia X

PT PT550 Stage 1 Heat Exchanger Outlet Pressure 0 - 115 psia X

PT PT560 Stage 2 Heat Exchanger Outlet Pressure 0 - 115 psia X

PT PT605 Facility LN2 Pressure at Densifier Inlet 0 - 165 psia X

PT PT707 Stage 1 Heat Exchanger Ullage Pressure 0 - 65 psia X

PT PT709 Stage 2 Heat Exchanger Ullage Pressure 0 - 65 psia X

PT PT715 Stage 2 Heat Exchanger Ullage Pressure 0 - 5 psia X

PT PT715A Inlet Pressure to Compressor First Stage 0 - 50 psia X

PT PT715B Inlet Pressure to Compressor Second Stage 0 - 50 psia X

PT PT715C Inlet Pressure to Compressor Third Stage 0 - 50 psia X

PT PT715D Discharge Pressure at Compressor Third Stage 0 - 50 psia X

PT PT715S Pressure at Compressor Surge Line Flow Meter 0 - 50 psia X

PT PT755 Local Atmospheric Pressure in LO2 Skid Area 0 - 20 psia X

PT PT800 500 psig Helium Supply Pressure to Skid 0 - 600 psig X

PT PT805 100 psig Helium System Pressure 0 - 150 psig X

PT PT807 25 psig Helium System Pressure 0 - 50 psig X

PT PT815 Helium Pressure in Compressor Enclosure 0 - 40 psia X

PT PT850 500 psig Nitrogen Supply Pressure to Skid 0 - 600 psig X

NASA/TM—2010-216247 96
APPENDIX A – LO2 PDU TEST ARTICLE INSTRUMENTATION (cont’d)

Channel ID

Description Range Location

Type ID Number Limits Units Facility Densifier STA

PT PT855 125 psig Nitrogen System Pressure 0 - 150 psig X

PT PT857 40 psig Nitrogen System Pressure 0 - 50 psig X

SI SC535 LO2 Pump Speed 0 - 5000 rpm X

SI SC715A Stage 1 Compressor Speed 0 - 12000 rpm X

SI SC715B Stage 2 Compressor Speed 0 - 12000 rpm X

SI SC715C Stage 3 Compressor Speed 0 - 12000 rpm X

TE TT510 LO2 Makeup Inlet Temperature 2.5 - 855 oR X

TE TT530 LO2 Pump Inlet Temperature (1 of 2) 2.5 - 855 oR X

TE TT532 LO2 Pump Inlet Temperature (2 of 2) 2.5 - 855 oR X

TE TT535A LO2 Pump Motor Winding "A" Temperature -100- 400 oF X

TE TT535B LO2 Pump Motor Winding "B" Temperature -100-400 oF X

TE TT535C LO2 Pump Motor Winding "C" Temperature -100-400 oF X

TE TT545 LO2 Pump Outlet Temperature 2.5 - 855 oR X

TE TT550 Stage 1 Heat Exchanger Outlet Temperature 2.5 - 855 oR X

TE TT565 Stage 2 Heat Exchanger Outlet Temperature 2.5 - 855 oR X

TE TT574 Densifier Skid Exit LO2 Temperature 2.5 - 855 oR X

TE TT592 LO2 Pond Vent Temperature 2.5 - 855 oR X

TE TT602A Stage 1 Heat Exchanger LN2 Bath Temperature 2.5 - 855 oR X

TE TT602B Stage 1 Heat Exchanger LN2 Bath Temperature 2.5 - 855 oR X

TE TT603A Stage 2 Heat Exchanger LN2 Bath Temperature 2.5 - 855 oR X

TE TT603B Stage 2 Heat Exchanger LN2 Bath Temperature 2.5 - 855 oR X

TE TT610 Facility LN2 Supply Temperature to Densifier 2.5 - 855 oR X

TE TT680 Heat Exchanger LN2 Drain Line Temperature 2.5 - 855 oR X

TE TT702A Stage 1 Heat Exchanger Ullage Temperature 2.5 - 855 oR X

TE TT702B Stage 1 Heat Exchanger Ullage Temperature 2.5 - 855 oR X

TE TT703A Stage 2 Heat Exchanger Ullage Temperature 2.5 - 855 oR X

TE TT703B Stage 2 Heat Exchanger Ullage Temperature 2.5 - 855 oR X

TE TT715A Inlet Temperature to Compressor First Stage 2.5 - 855 oR X

TE TT715B Inlet Temperature to Compressor Second Stage 2.5 - 855 oR X

TE TT715C Inlet Temperature to Compressor Third Stage 2.5 - 855 oR X

TE TT715D Discharge Temperature at Compressor Stage 3 2.5 - 855 oR X

TE TT715E Vent Gas Temperature at FT715 Flow Meter 2.5 - 855 oR X

TE TT715M1A Stage 1 Compressor Motor Winding "A" Temp. -100-400 oF X

TE TT715M1B Stage 1 Compressor Motor Winding "B" Temp. -100-400 oF X

TE TT715M1C Stage 1 Compressor Motor Winding "C" Temp. -100-400 oF X

TE TT715M2A Stage 2 Compressor Motor Winding "A" Temp. -100-400 oF X

TE TT715M2B Stage 2 Compressor Motor Winding "B" Temp. -100-400 oF X

TE TT715M2C Stage 2 Compressor Motor Winding "C" Temp. -100-400 oF X

TE TT715M3A Stage 3 Compressor Motor Winding "A" Temp. -100-400 oF X

TE TT715M3B Stage 3 Compressor Motor Winding "B" Temp. -100-400 oF X

TE TT715M3C Stage 3 Compressor Motor Winding "C" Temp. -100-400 oF X

TE TT715S Temp. at Compressor Surge Line Flow Meter 2.5 - 855 oR X

NASA/TM—2010-216247 97
APPENDIX A – LO2 PDU TEST ARTICLE INSTRUMENTATION (cont’d)

Channel ID

Description Range Location

Type ID Number Limits Units Facility Densifier STA

TE TT720 Gas Temperature in Phase Separator 2.5 - 855 oR X

TE TT861A PLC Cabinet Temperature 0 - 120 oF X

TE TT861B 208V Cabinet Temperature 0 - 120 oF X

TE TT861C 480V Cabinet Temperature 0 - 120 oF X

TE TT862 Instrumentation Cabinet Temperature 0 - 120 oF X

VE VT535 LO2 Pump Vibration Sensor 0 - 1.0 in/sec X

VE VT715A Compressor First Stage Vibration Sensor 0 - 1.0 in/sec X

VE VT715B Compressor Second Stage Vibration Sensor 0 - 1.0 in/sec X

VE VT715C Compressor Third Stage Vibration Sensor 0 - 1.0 in/sec X

XFC FC1 Flow Coefficient at Compressor First Stage 0 - 1.0 d-less X

XFC FC2 Flow Coefficient at Compressor Second Stage 0 - 1.0 d-less X

XFC FC3 Flow Coefficient at Compressor Third Stage 0 - 1.0 d-less X

ZT ZT715 Gas Bypass Valve FCV715 Position Transmitter 0 - 100 % close X

Instrumentation Legend:

ET voltage transducer

FT mass flow transducer

FXQ volumetric flow rate (calculated)

IT current transducer

LT level transducer

PDT differential pressure transducer

PT pressure transducer

SI speed indicator

TE temperature element

VE vibration element

XFC flow coefficient, (D (calculated)

ZT position transmitter

NASA/TM—2010-216247 98
APPENDIX B

STA TANKING TABLE

NASA/TM—2010-216247 99
APPENDIX B – STA TANKING TABLE

Table B.1: STA test bed tanking and cryogenic loading data.

Total STA Tank Volume = 2556.68 ft 3

LN2 NBP Density = 50.36 lb/ft 3LO2 NBP Density = 71.23 lb/ft3

Height STA Cold Cold Percent NBP Liquid NBP Liquid

from Top Vertical Volume in Volume in Ullage Nitrogen Oxygen

(inch) Diode ID Tank Tank Volume Mass Mass

PVT-X (gal) (ft3) (%) (lbm) (lbm)

0 - 19126 2556.7 0.0 128754 182112

14 1 19012 2541.4 0.6 127984 181023

28 2 18835 2517.7 1.5 126791 179335

44 3 18538 2478.0 3.1 124790 176506

46 4 18493 2471.9 3.3 124486 176076

50 5 18396 2459.1 3.8 123839 175161

56 6 18237 2437.8 4.6 122768 173645

62 7 18059 2414.0 5.6 121569 171949

68 8 17861 2387.5 6.6 120235 170062

74 9 17642 2358.2 7.8 118759 167975

80 10 17401 2326.0 9.0 117135 165678

88 11 17043 2278.1 10.9 114726 162271

98 12 16534 2210.1 13.6 111301 157426

110 13 15827 2115.6 17.3 106540 150691

122 14 15006 2005.9 21.5 101017 142880

134 15 14096 1884.2 26.3 94889 134213

146 16 13148 1757.5 31.3 88508 125188

158 17 12175 1627.5 36.3 81960 115926

170 18 11178 1494.2 41.6 75248 106432

182 19 10157 1357.7 46.9 68376 96712

194 20 9113 1218.1 52.4 61346 86769

212 21 7503 1002.9 60.8 50508 71439

230 22 5845 781.3 69.4 39346 55652

254 23 3562 476.2 81.4 23980 33918

278 24 1343 179.6 93.0 9044 12791

302 25 28 3.8 99.9 191 271

306 - 0 0.0 100.0 0 0

NASA/TM—2010-216247 100
APPENDIX B – STA TANKING TABLE (cont’d)

Figure B.1: STA cold fluid volume vs. height profile.

20000

16000

0rn

E 12000 0

0 8000

U)

4000

0

0 50 100 150 200 250 300

Height from Top (in)

NASA/TM—2010-216247 101

APPENDIX C

S40 FACILITY INSTRUMENTATION

NASA/TM—2010-216247 103
APPENDIX C – S40 FACILITY INSTRUMENTATION

Channel ID

Description Range Location

Type ID Number Limits Units Facility Densifier STA

LT LTO2 STA Liquid Level Capacitance Probe for LO2 0 - 32 inch X

LT LTN2 STA Liquid Level Capacitance Probe for LN2 0 - 32 inch X

PDT N7113 N-71 Liquid Level AP Transducer (LN2 Volume) 0 - 13000 gallons X

PDT XO0602 Densifier Product Outlet AP across Filter 0 - 5 psid X

PDT XO2111 STA Boiloff Rifice Meter AP Transducer 0 - 5 psid X

PDT XO8309 N-83 Liquid Level AP Transducer (LO2 Volume) 0 - 28000 gallons X

PT H1102 GHe Tuber Manifold Pressure 0 - 3000 psig X

PT H1110 GHe Pressure to LO2 Densifier 0 - 550 psig X

PT H1208 GHe Purge Pressure at 30 psig 0 - 40 psig X

PT H1508 GHe Purge Pressure to STA Tank 0 - 40 psig X

PT N1102 GN2 Tuber Manifold Pressure 0 - 3000 psig X

PT N1110 GN2 Pressure to LO2 Densifier 0 - 600 psig X

PT N1208 GN2 Pressure to Purge 0 - 40 psig X

PT N1508 GN2 Pressure to Valve Actuators 0 - 150 psig X

PT N1513 GN2 Pressurant Gas to Dewar N-71 0 - 75 psig X

PT N7117 N-71 Dewar Internal Pressure 0 - 50 psig X

PT XO0104 LO2 Densifier Skid Inlet Pressure 0 - 50 psig X

PT XO0607 STA Tank Liquid Inlet Pressure 0 - 50 psig X

PT XO2103 STA Tank Internal Ullage Pressure 0 - 60 psia X

PT XO2302 STA Syphon Line Outlet Pressure 0 - 50 psig X

PT XO8311 N-83 Dewar Internal Ullage Pressure 0 - 75 psig X

TE N7105 N-71 Dewar Liquid Nitrogen Temperature 2.5 - 855 oR X

TE N7107 N-71 Dewar Ullage Temperature 2.5 - 855 oR X

TE N7109 N-71 Dewar Liquid Nitrogen Temperature 2.5 - 855 oR X

TE PLT1 STA Internal Temperature, Lateral Rake, 98” level 2.5 - 855 oR X

TE PLT2 STA Internal Temperature, Lateral Rake, 98” level 2.5 - 855 oR X

TE PLT3 STA Internal Temperature, Lateral Rake, 98” level 2.5 - 855 oR X

TE PLT4 STA Internal Temperature, Lateral Rake, 98” level 2.5 - 855 oR X

TE PLT5 STA Internal Temperature, Lateral Rake, 98” level 2.5 - 855 oR X

TE PLT6 STA Internal Temperature, Lateral Rake, 160” level 2.5 - 855 oR X

TE PLT7 STA Internal Temperature, Lateral Rake, 160” level 2.5 - 855 oR X

TE PLT8 STA Internal Temperature, Lateral Rake, 160” level 2.5 - 855 oR X

TE PLT9 STA Internal Temperature, Lateral Rake, 160” level 2.5 - 855 oR X

TE PLT10 STA Internal Temperature, Lateral Rake, 160” level 2.5 - 855 oR X

TE PLT11 STA Internal Temperature, Lateral Rake, 218” level 2.5 - 855 oR X

TE PLT12 STA Internal Temperature, Lateral Rake, 218” level 2.5 - 855 oR X

TE PLT13 STA Internal Temperature, Lateral Rake, 218” level 2.5 - 855 oR X

TE PLT14 STA Internal Temperature, Lateral Rake, 218” level 2.5 - 855 oR X

TE PLT15 STA Internal Temperature, Lateral Rake, 218” level 2.5 - 855 oR X

NASA/TM—2010-216247 104
APPENDIX C – S40 FACILITY INSTRUMENTATION (cont’ d)

Channel ID

Description Range Location

Type ID Number Limits Units Facility Densifier STA

TE PVT1 STA Internal Temperature, Vertical Rake, 14” level 2.5 - 855 oR X

TE PVT2 STA Internal Temperature, Vertical Rake, 28” level 2.5 - 855 oR X

TE PVT3 STA Internal Temperature, Vertical Rake, 44” level 2.5 - 855 oR X

TE PVT4 STA Internal Temperature, Vertical Rake, 46” level 2.5 - 855 oR X

TE PVT5 STA Internal Temperature, Vertical Rake, 50” level 2.5 - 855 oR X

TE PVT6 STA Internal Temperature, Vertical Rake, 56” level 2.5 - 855 oR X

TE PVT7 STA Internal Temperature, Vertical Rake, 62” level 2.5 - 855 oR X

TE PVT8 STA Internal Temperature, Vertical Rake, 68” level 2.5 - 855 oR X

TE PVT9 STA Internal Temperature, Vertical Rake, 74” level 2.5 - 855 oR X

TE PVT10 STA Internal Temperature, Vertical Rake, 80” level 2.5 - 855 oR X

TE PVT11 STA Internal Temperature, Vertical Rake, 88” level 2.5 - 855 oR X

TE PVT12 STA Internal Temperature, Vertical Rake, 98” level 2.5 - 855 oR X

TE PVT13 STA Internal Temperature, Vertical Rake, 110” level 2.5 - 855 oR X

TE PVT14 STA Internal Temperature, Vertical Rake, 122” level 2.5 - 855 oR X

TE PVT15 STA Internal Temperature, Vertical Rake, 134” level 2.5 - 855 oR X

TE PVT16 STA Internal Temperature, Vertical Rake, 146” level 2.5 - 855 oR X

TE PVT17 STA Internal Temperature, Vertical Rake, 158” level 2.5 - 855 oR X

TE PVT18 STA Internal Temperature, Vertical Rake, 170” level 2.5 - 855 oR X

TE PVT19 STA Internal Temperature, Vertical Rake, 182” level 2.5 - 855 oR X

TE PVT20 STA Internal Temperature, Vertical Rake, 194” level 2.5 - 855 oR X

TE PVT21 STA Internal Temperature, Vertical Rake, 212” level 2.5 - 855 oR X

TE PVT22 STA Internal Temperature, Vertical Rake, 230” level 2.5 - 855 oR X

TE PVT23 STA Internal Temperature, Vertical Rake, 254” level 2.5 - 855 oR X

TE PVT24 STA Internal Temperature, Vertical Rake, 278” level 2.5 - 855 oR X

TE PVT25 STA Internal Temperature, Vertical Rake, 302” level 2.5 - 855 oR X

TE XO0107 Densifier Skid Liquid Inlet Temperature 2.5 - 855 oR X

TE XO0606 STA Facility Liquid Inlet Temperature 2.5 - 855 oR X

TE XO2102 STA Vent Gas Temperature 2.5 - 855 oR X

TE XO2122 STA Boil-Off Gas Temperature 2.5 - 855 oR X

TE XO2305 Syphon Line Outlet Temperature 2.5 - 855 oR X

TE XO2402 STA Lobe 1 Fill Temperature 2.5 - 855 oR X

TE XO2502 STA Lobe 2 Fill Temperature 2.5 - 855 oR X

TE XO8304 N-83 Dewar Liquid Temperature 2.5 - 855 oR X

TE XO8306 N-83 Dewar Ullage Temperature 2.5 - 855 oR X

TE XO8308 N-83 Dewar Liquid Temperature 2.5 - 855 oR X

Instrumentation Legend:

LT level transducer

PDT differential pressure transducer

PT pressure transducer

TE temperature element

NASA/TM—2010-216247 105
APPENDIX D

GN2 COMPRESSOR TEST DATA

NASA/TM—2010-216247 106
Figure D.1: GN2 compressor speed vs. time.

3rd Stg

10 20 30 40 50 60 70 80

Time (min)

12000

10000

8000

ECL

a 6000

d

d

CL

CD

4000

2000

0

0

No. 82

2/00

SC715A

SC715B

SC715C

10 20 30 40 50 60 70 80

Time (min)

16

14

12

ca

a 10

2

n 8

d

6

4

2

0

o. 82

/00

T715A

T715B

T715C

T715D

APPENDIX D – GN2 COMPRESSOR TEST DATA

Figure D.2: Compressor interstage pressure profile.

NASA/TM—2010-216247 107
APPENDIX D – GN2 COMPRESSOR TEST DATA (cont’d)

T;esG^

TT715D 3rd Stg Outlet

2nd Stg Outlet

—TT,7.

1

st Stg Outlet

_^,

_TT,7

TT-7;

TT715A 1

st Stg Inlet

NASA/TM—2010-216247 108
APPENDIX D – GN2 COMPRESSOR TEST DATA (cont’d)

NASA/TM—2010-216247 109
10 20 30 40 50 60 70 80

Time (min)

70

65

60

a^

0 55

U

50

c

0

y 45

0

0_

40

m

35

30

25

0

. 82

00

T715

Figure D'.8 Compressor motor'uoltage'vs. time.

3

rd Stg

APPENDIX D – GN2 COMPRESSOR TEST DATA (cont’d)

Figure D.7: Compressor surge bypass valve position vs. time.

NASA/TM—2010-216247 110
APPENDIX D – GN2 COMPRESSOR TEST DATA (cont’d)

NASA/TM—2010-216247 111
o. 144

7/00

- SC715A

- SC715B

- SC715C

APPENDIX D – GN2 COMPRESSOR TEST DATA (cont’d)

Figure D.12: GN2 compressor speed vs. time.

3rd Stg

10000

9000

8000

7000

E 6000

5000 N

N

cn 4000

3000

2000

1000

0

0 20 40 60 80 100

Time (min)

NASA/TM—2010-216247 112
APPENDIX D – GN2 COMPRESSOR TEST DATA (cont’d)

NASA/TM—2010-216247 113
APPENDIX D – GN2 COMPRESSOR TEST DATA (cont’d)

NASA/TM—2010-216247 114
APPENDIX D – GN2 COMPRESSOR TEST DATA (cont’d)

NASA/TM—2010-216247 115
1 st Stg

C715A

3

rd Stg

C715C

406 -

,35D'. -

250

146

W

D

APPENDIX D – GN2 COMPRESSOR TEST DATA (cont’d)

NASA/TM—2010-216247 116
0.3

0.3

o. 144

7/00

80 100

0.0

0.1

VT715A

VT715B

VT715C

0.2

c

0 0.2

N

> 0.1

40 60

Time (min)

APPENDIX D – GN2 COMPRESSOR TEST DATA (cont’d)

Figure D.22: Compressor motor vibration history.

0 20

NASA/TM—2010-216247 117
APPENDIX E

LO2 RECIRCULATION PUMP

TEST DATA

NASA/TM—2010-216247 118
APPENDIX E – LO2 RECIRCULATION PUMP TEST DATA

Figure E.1 ,Cryo-Mach pump speed vs. time.

NASA/TM—2010-216247 119
APPENDIX E – LO2 RECIRCULATION PUMP TEST DATA (cont’d)

NASA/TM—2010-216247 120
APPENDIX E – LO2 RECIRCULATION PUMP TEST DATA (cont’d)

NASA/TM—2010-216247 121
1717545 Outlet

APPENDIX E – LO2 RECIRCULATION PUMP TEST DATA (cont’d)

1717532 Inlet

NASA/TM—2010-216247 122
APPENDIX F

LN2 PERFORMANCE TEST DATA

with LOX PDU

NASA/TM—2010-216247 123
mance

. 3A

00

C715A

C715B

C715C

40 80 120 160 200 240

Time (min)

18

16

14

12

a

10

N

a 8

6

4

2

0

mance

. 3A

00

T715A

T715B

T715C

T715D

APPENDIX F – LN2 PERFORMANCE TEST DATA with LOX PDU

Figure F.1: gN2 compressor speed vs. time.

10000

9000

8000

7000

E 6000

CLL

Q

5000

Q

CL 4000

3000

2000

1000

0

0 40 80 120 160 200 240

Time (min)

Figure F.2: Compressor interstage pressure profile.

NASA/TM—2010-216247 124
TT715A LN2 Perfo

TT715B Test n

TT715C 10/5

TT715D

TT715D 3rd Stg Outlet

2nd Stg Outlet

1

st Stg Outlet

TT715A 1

st Stg Inlet

420

370

IY 320

0,

E

12 270

Q

CL

E

N

220

170

120

rmance

. 3A

00

APPENDIX F – LN2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure F.3: Compressor interstage gas temperature vs. time.

4

0 40 80 120 160 200 240

Time (min)

Figure F.4: Compressor discharge mass flow and gas bypass flow vs. time.

FT715 LN2 Performance

FT715S Test no. 3A

FT607 10/5/00

3

U

N

N 2

3

0

LL

1

0

0 40 80 120 160 200 240

Time (min)

NASA/TM—2010-216247 125
70

60

N 50

CL

E

m

c

40

30

0

0

20

10

0

0 40 80 120 160 200 240

Time (min)

ormance

o. 3A

/00

APPENDIX F – LN2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

0.60

0.50

0.40

C

a^

0.30

0

U

3

0.20

0.10

0.00

0

Figure F.5: Compressor flow coefficient profile vs. time.

40 80 120 160 200 240

Time (min)

Figure F.6: Compressor motor current draw vs. time.

FC1

FC2

FC3

LN2 Performance

o. 3A

/00

NASA/TM—2010-216247 126
APPENDIX F – LN2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure F.7: Cryo-Mach outlet LN2 mass flow rate vs. time.

20

U

N

15

a^

m

3

r0° 10

N

ZJ

5

25

0

0

180

170

160

Q2

150

N

CL

E

N

F- 140

130

120

0

40 80 120 160 200 240

Time (min)

Figure F.8: LN2 stream temperatures across PDU skid vs. time.

TT530 LN2 Performance

TT545 Test no. 3A

TT550 10/5/00

TT565

------ TT574

TT530

Pump Inlet f

TT545

Pump Outlet

TT550

Stg 1 HtExer

Outlet

120 160 200 240

Time (min)

TT574 i

PDU Skid

Outlet

40 80

NASA/TM—2010-216247 127
APPENDIX F – LN2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure F.9: LN2 stream pressures across PDU skid vs. time.

PT540

120 Pump Outlet

LN2 Performance

110 Test no. 3A

10/5/00

100

PT525

90 PT540

Cal

80 PT550

o- PT560

PT560

2 70 Stg 2 HtExer

w Outlet

2 60

a

50

40

30

PT525

20 Pump Inlet

0 40 80 120 160 200 240

Time (min)

Figure F.10: Heat exchanger LN2 bath and ullage temperatures vs. time.

165

155

145

N

CL

E 135

a^

H

125

115

LN2 Performance TT602A

Test no. 3A TT603A

10/5/00 TT702A

TT703A

TT702A

Stg 1 Ullage

TT602A -^- -

Stg 1 Bath

TT603A

Stg 2 Bath

TT703A

Stg 2 Ullage

0 40 80 120 160 200 240

Time (min)

NASA/TM—2010-216247 128
50 100 150 200 250

Time (min)

300

Q.. 2

N

250

CL

E

a^

H

200

400

350

150

100

0

LN2 Performance

PVT5

PVT10

Test no. 3A

10/5/00 PVT5 PVT15

PVT10 PVT21

PVT24

PVT15 ---- XO2502

PVT21

PVT24

XO2502 1

STA Inlet

APPENDIX F – LN2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure F.11: STA vertical diode temperture profile during DLN2 fill.

Figure F.12 :STA LN2 vertical temperature gradient at end of DLN2 loading test 3A

155 LN2

PVT3 Performance

150 Test no. 3A

10/5/00

145

t = 200 min.

Qom, 140

t PVT-x

N

135

CL

aa) 130

125

PVT12

PVT25

120

115

30 80 130 180 230 280 330

Height from Top (in)

NASA/TM—2010-216247 129
APPENDIX F – LN2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure F.13: Dewar N83 and N71 volume change during PDU test operation.

22000

LN2 Performance

Test no. 3A

10/5/00

18000

N83 Volume X8309

XO8309 N7113

m

14000

a^

E

0

z 

10000 J

N71 Volume

N7113

6000

2000

0 50 100 150 200 250

Time (min)

Figure F.14: DLN2 resaturation and warm-up temperature during storage in STA.

146

144

142

140

138

= 136

CL 134

E

H 132

130

128

126

124

PVT10

PVT10

PVT15

PVT18

PVT20

PVT20 PVT24

DLN2 Ground

Hold Test in STA

PVT24

10/5/00 - 10/6/00

0 5 10 15 20

Time (hr)

NASA/TM—2010-216247 130
APPENDIX G

LO2 PERFORMANCE TEST DATA

with LOX PDU

NASA/TM—2010-216247 131
175

165

155

N

Q

145

CL

E

N

~ 135

125

115

PVT21

PVT24

XO2402 STA Inlet

APPENDIX G – LO2 PERFORMANCE TEST DATA with LOX PDU

Figure G.1: STA inlet LO2 flow and LO2 STA tank make-up rate.

25

20

U

N

y

J^

^- 15

3

0

CP

y

y

E 10

N

0

J

5

0

0

LO2 Thermal

Stratification

C

35

15

50 100 150 200

Time (min)

Figure G.2: STA thermal stratification temperature profile data.

250 300

LO2 Thermal

>n

C

Stratificatii

STA Outlet Test no. 2

XO2305 11/22/00

XO2305

PVT15

PVT21

PVT24

PVT15 XO2402

0 50 100 150 200 250 300

Time (min)

NASA/TM—2010-216247 132
APPENDIX G – LO2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure G.3: STA liquid level capacitance probe data.

LT02

30

25

U

c

20 0

m

U_

15

5

a^

^ 10 0

5

0

0

LO2 Thermal

Stratification

Test no. 2C

11/22/00

50 100 150 200 250

Time (min)

Figure G.4: Compressor inlet and discharge pressure vs. time.

300

16

14

12

co

0 10

8

a.

6

4

2

PT715D 3rd Stg Outlet

PT715D

PT715A

LO2 Thermal

Stratification

Test no. 2C

11/22/00

PT715A 1 st Stg Inlet

0 50 100 150 200 250 300

Time (min)

NASA/TM—2010-216247 133
50 100 150 200 250 300

Time (min)

4

3

N 3

a^

m 2

3

0

crw 2

m

E

Nz 1

1

0

0

APPENDIX G – LO2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure G.5: Compressor mass flow rate history.

Figure G.6: LO2 stream temperatures vs. time.

180

170

160

02 150

m

N

E 140

Q

H

130

120

110

0

TT530 Pump Inlet

Stg 1 HtExer

TT550 Outlet

TT574

PDU Skid O

TT565 Stg 2 HtExer

Outlet

50 100 150 200

Time (min)

LO2 Thermal

Stratification

Test no. 2C

11/22/00

TT545 TT530 Pump Outlet

TT545

TT550

TT574

TT565

250 300

NASA/TM—2010-216247 134
o. 2C

2J00

APPENDIX G – LO2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure G.7: LO2 stream pressure history.

LO2 Thermal

ctratification 65

60

55

m

50

45

a

40

35

30

0 50 100 150 200 250 300

Time (min)

NASA/TM—2010-216247 135
6

LO2

Therm

Stratifica

Test no.

11/22/

PT709

PT7

PT715 PT7

5

al

tion

2C

0

4

c^

n

3

;v

a.

2

09

15

1

0

0 50 100 150 200 250 300

Time (min)

Figure G.10: STA inlet LO2 flow and LO2 STA tank make-up rate.

50 100 150 200 250

Time (min)

35

30

25

3 20

0

CP

W

cNO 15

E

N

10

5

0

0

APPENDIX G – LO2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure G.9: Heat exchanger ullage pressure history - stage 2.

LO2 Thermal

NASA/TM—2010-216247 136
50 100 150 200 250

Time (min)

2 155

12 145

a)

CL

E

a^

~ 135

175

165

125

115

0

APPENDIX G – LO2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure G.11: STA thermal stratification temperature profile data.

Figure G.12: STA liquid level capacitance probe data.

30

25

O

C

20

O

m

O

a

15

5

a^

-0 10

0

a.

5

0

0 50 100 150 200 250

Time (min)

NASA/TM—2010-216247 137
LO2 Thermal

50 100 150 200 250

Time (min)

4

3

U

N 3

a^

2

3

0

N 2

CU

E

N Z 1

rn

1

0

0

APPENDIX G – LO2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure G.13: Compressor inlet and discharge pressure vs time.

16

14

12

Q 10

m

8 N

d

6

4

2

PT715D 3rd Stg Outlet

PT715D

PT715A

LO2 Thermal

Stratification

Test no. 4C

12/05/00

PT715A 1

st Stg Inlet

0 50 100 150 200 250

Time (min)

Figure G.14: Compressor mass flow rate history.

NASA/TM—2010-216247 138
APPENDIX G – LO2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure G.15: LO2 stream temperatures vs. time.

180 LO2 Thermal

Stratification

Test no. 4C

170 TT530 Pump Inlet 12/05/00

TT545

Pump Outlet

160 TT530

TT545

150 TT550

Stg 1 HtExer

Outlet TT550 TT574

TT565 E 140

a^

TT574

130 PDU Skid Outlet

120

TT565 Stg 2 HtExer

Outlet

110

0 50 100 150 200 250

Time (min)

Figure G.16: LO2 stream pressure vs. history.

LO2 Thermal

Stratification

75 Test no. 4C

` 12/05/00

65

PT540 Pump Outlet

""11110#1Y 5WO

'Vi 55

a^

w

i PT550 PT560 St Stg 2 HtExer gO1

1 

HtExer

Outlet - _

PT540

PT550 45

d rw PT560

PT525

•miw., yT wad + Pump Inlet

35 PT525 \-a

! J off,

• }FF

25

0 50 100 150 200 250

Time (min)

NASA/TM—2010-216247 139
50 100 150 200 250

Time (min)

5.0

4.5

m

Q 4.0

Q2 3.5 a

3.0

2.5

LO2 Thermal

St tifition

C

APPENDIX G – LO2 PERFORMANCE TEST DATA with LOX PDU (cont’d)

Figure G.18: Heat exchanger ullage pressure history - stage 2.

0

NASA/TM—2010-216247 140
APPENDIX H

LO2 PDU and S40 FACILITY FLOW

SCHEMATICS

NASA/TM—2010-216247 141
XT A Q A /rVM—2 0 1 0-2 1 6247
NASA/TM—2010-216247 145
NASA/TM—2010-216247
NOTE: Numbers in parentheses refer to specific

explanatory notes in Section 5,1 of ANSI / I SA - S5.1

NASA/TM—2010-216247 149
NASA/TM—2010-216247 151

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01-05-2010 Technical Memorandum

4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER

Liquid Oxygen Propellant Densification Production and Performance Test Results with a

Large-Scale Flight-Weight Propellant Tank for the X33 RLV 5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S) 5d. PROJECT NUMBER

Tomsik, Thomas, M.; Meyer, Michael, L.

5e. TASK NUMBER

5f. WORK UNIT NUMBER

WBS 095240.04.02.24.03

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION

National Aeronautics and Space Administration REPORT NUMBER

John H. Glenn Research Center at Lewis Field E-17234

Cleveland, Ohio 44135-3191

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITOR'S

National Aeronautics and Space Administration ACRONYM(S)

Washington, DC 20546-0001 NASA

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REPORT NUMBER

NASA/TM-2010-216247

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Subject Category: 28

Available electronically at http://gltrs.grc.nasa.gov

This publication is available from the NASA Center for AeroSpace Information, 443-757-5802

13. SUPPLEMENTARY NOTES

14. ABSTRACT

This paper describes in-detail a test program that was initiated at the Glenn Research Center (GRC) involving the cryogenic densification of

liquid oxygen (LO2). A large scale LO2 propellant densification system rated for 200 gpm and sized for the X-33 LO2 propellant tank, was

designed, fabricated and tested at the GRC. Multiple objectives of the test program included validation of LO2 production unit hardware and

characterization of densifier performance at design and transient conditions. First, performance data is presented for an initial series of LO2

densifier screening and check-out tests using densified liquid nitrogen. The second series of tests show performance data collected during

LO2 densifier test operations with liquid oxygen as the densified product fluid. An overview of LO2 X-33 tanking operations and load tests

with the 20,000 gallon Structural Test Article (STA) are described. Tank loading testing and the thermal stratification that occurs inside of a

flight-weight launch vehicle propellant tank were investigated. These operations involved a closed-loop recirculation process of LO2 flow

thru the densifier and then back into the STA. Finally, in excess of 200,000 gallons of densified LO2 at 120 oR was produced with the

propellant densification unit during the demonstration program, an achievement that’s never been done before in the realm of large-scale

cryogenic tests.

15. SUBJECT TERMS

Propellant densification; Subcooled cryogens; Liquid oxygen

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON

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