NASA/TM-2009-215570 

NESC-RP-05-114/05-013-E

 

Kennedy Space Center (KSC) Launch Complex 

39 (LC-39) Gaseous Hydrogen (GH2) Vent Arm 

Behavior Prediction Model Review Technical 

Assessment Report 

Timmy R. Wilson/NESC 

Kennedy Space Center, Kennedy Space Center, Florida 

Geoffrey Beech and Ian Johnston 

Marshall Space Flight Center, Huntsville, Alabama 

March 2009 
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NESC-RP-05-114/05-013-E

 

Kennedy Space Center (KSC) Launch Complex 

39 (LC-39) Gaseous Hydrogen (GH2) Vent Arm 

Behavior Prediction Model Review Technical 

Assessment Report 

Timmy R. Wilson/NESC 

Kennedy Space Center, Kennedy Space Center, Florida 

Geoffrey Beech and Ian Johnston 

Marshall Space Flight Center, Huntsville, Alabama 

National Aeronautics and 

Space Administration 

Langley Research Center 

Hampton, Virginia 23681-2199 

March 2009 
The use of trademarks or names of manufacturers in the report is for accurate reporting and does not 

constitute an official endorsement, either expressed or implied, of such products or manufacturers by the 

National Aeronautics and Space Administration. 

Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 
NASA Engineering and Safety Center 

Technical Assessment Report

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Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

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NESC Request No. 05-013-E 

Kennedy Space Center (KSC) Launch Complex 

39 (LC-39) Gaseous Hydrogen (GH2) Vent Arm 

Behavior Prediction Model Review 

Technical Assessment Report

October 6, 2005 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

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Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

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NESC Request No. 05-013-E 

TABLE OF CONTENTS 

Volume I: Technical Assessment Report 

1.0 Authorization and Notification........................................................................................ 3 

2.0 Signature Page................................................................................................................... 4 

3.0 Team Members, Ex Officio Members, and Consultants............................................... 5 

4.0 Executive Summary.......................................................................................................... 6

5.0 Assessment......................................................................................................................... 7 

6.0 Description of the Problem, Proposed Solutions, and Risk Assessment...................... 8 

7.0 Data Analysis................................................................................................................... 12 

7.1 Wind Loading ....................................................................................................... 12 

7.2 Kinematics Analysis ............................................................................................. 12 

7.3 Stiffness Verification ............................................................................................ 15 

8.0 Findings, Observations and Recommendations........................................................... 17 

8.1 Findings................................................................................................................. 17 

8.2 Recommendations................................................................................................. 17 

9.0 Lessons Learned.............................................................................................................. 18 

10.0 Definition of Terms......................................................................................................... 18 

11.0 Minority Report (Dissenting Opinions) ........................................................................ 18 

Volume II: Appendices

Appendix A. ITA/I Request Form (NESC-PR-003-FM-01)................................................... 20 

Appendix B. Vent Pipe Sensitivities......................................................................................... 24 

Appendix C. Pictures of the FE Model and the Associated Calculations............................. 27 

Appendix D. List of Acronyms ................................................................................................. 31 

List of Figures

6.0-1 Tank Vent Umbilical Retraction Mechanism ..................................................................... 9 

6.0-2 Static Lanyard Drop-Weight Function.............................................................................. 10 

6.0-3 Umbilical Retention Mechanism ...................................................................................... 11 

7.2-1 Haunch Pivot Arm Slots (HPAS) ..................................................................................... 13 

7.2-2 The HPAS at Approximately 40 Degrees to the Vent Arm.............................................. 14 
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NESC Request No. 05-013-E 

 Volume I: Technical Assessment Report 

1.0 Authorization and Notification 

The request to conduct an independent technical assessment (ITA) was submitted to the NASA 

Engineering and Safety Center (NESC) on March 29, 2005. 

Mr. Ralph Roe, Director of the NESC, approved this activity in an out-of-board action on April 

4, 2005. 

The ITA Plan was developed by Timmy R. Wilson and approved in an out-of-board action by 

the NESC Review Board (NRB) on May 5, 2005. Follow-up updates to the Plan were approved 

by the NRB on May 12, 2005. 

The NESC team review of the Kennedy Space Center (KSC) Launch Complex 39 (LC-39) math 

model took place between April 28, 2005 and July 27, 2005.

The final Technical Assessment report was presented to the NRB on October 6, 2005. 
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NESC Request No. 05-013-E 

2.0 Signature Page 

Assessment Team Members 

Timmy R. Wilson Geoffrey Beech 

NESC Chief Engineer, KSC Systems Analysis Team Lead, MSFC 

Lead 

Ian Johnston, MSFC 

Structural and Dynamics Analysis Branch, MSFC 
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3.0 Team Members, Ex Officio Members, and Consultants 

Timmy R. Wilson, NESC Chief Engineer (NCE) 

Geoffrey Beech, MSFC 

Ian Johnston, MSFC 
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NESC Request No. 05-013-E 

4.0 Executive Summary 

The NESC Assessment Team reviewed a computer simulation of the LC-39 External Tank (ET) 

GH2 Vent Umbilical system developed by United Space Alliance (USA) for the Space Shuttle 

Program (SSP) and designated KSC Analytical Tool ID 451 (KSC AT-451). The team verified 

that the vent arm kinematics were correctly modeled, but noted that there were relevant system 

sensitivities. Also, the structural stiffness used in the math model varied somewhat from the 

analytic calculations. Results of the NESC assessment were communicated to the model 

developers.

Two significant issues were identified, as follows: 

1. The wind environment at the vent arm is not directly measured, but is estimated from data 

taken at remote locations. 

2. The model is not fully validated. 

It is recommended that the wind measurement equipment at LC-39 Pads A and B be upgraded to 

better characterize the wind speed and direction at the vent arm, and additional tests be 

performed to validate the model. 
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NESC Request No. 05-013-E 

5.0 Assessment 

The scope of this assessment was limited to examining and peer reviewing the GH2 vent line 

math model. A plan for this effort was completed and approved by the NRB on May 12, 2005. 
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6.0 Description of the Problem, Proposed Solutions, and Risk Assessment 

The GH2 vent arm is a pad structure designed to support the Ground Umbilical Carrier Panel 

(GUCP) and seven-inch hydrogen vent line flex hose during the Space Shuttle pad processing 

(refer to Figure 6.0-1). At T-0, the GUCP separates from the Space Shuttle ET by means of a 

pyrotechnic device and the arm drops away from the vehicle and into a restraint (refer to Figures 

6.0-2 and 6.0-3). 

During the STS-108 launch (December 5, 2001), the arm failed to engage the restraining device 

and impacted the pad structure with resultant damage to both the arm and the pad. Debris was 

liberated during the incident which could have caused significant damage to the Space Shuttle 

flight vehicle had it made contact. Subsequent investigation identified two major contributors: a 

Pivot Arm shock absorber did not operate properly causing the Pivot Arm to twist and rotate the 

vent arm to the side as it dropped; and relatively high crosswinds (10-18 knots) during launch 

pushed the vent arm over. 

There were other factors that were considered minor contributors. Drawing and requirements 

changes were implemented to ensure the pivot arm shocks are lab-tested and adjusted prior to 

each launch. Additionally, the openings on the Umbilical Retract Deceleration Units at both LC39 Pads A and B were widened. Clearance on the south side of both Pads A and Pad B 

Deceleration Unit openings was increased by 9-1/4 inches over STS-108. 

The USA-developed computer simulation, KSC AT-451, simulates the kinetics of the relevant 

subsystems of the ET GH2 umbilical system when subjected to the two contributors (mentioned 

previously) and the initial conditions due to the Space Shuttle Main Engine (SSME) startup 

transient (a.k.a. “twang”). Simulations conducted using this model resulted in reduction of the 

vent arm wind limit, from 34 to 24 knots, specified by the SSP Launch Commit Criteria (LCC). 

The KSC Independent Technical Authority (ITA) and Ground Operations Chief Engineer’s 

Office requested the NESC review the math model to ensure it was not providing overly 

conservative or restrictive results. 
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NESC Request No. 05-013-E 

215 FT

203 FT

195 FT

186 FT

HAUNCH

79K05845

HAUNCH PIVOT ARM

79K05845

GH2 VENT

HARD LINE

S77KL16005

GH2 VENT FWD

FLEX HOSE

79K32629

STATIC

LANYARD

80K51097

GH2 VENT AFT

FLEX HOSE

79K17193

DECEL CABLE

S77KL16015

DECEL SHOCK

ABSORBER

S77KL16015

DROPWEIGHT

RATCHET

BAR ASSY

80K51097

FWD FLEX

HOSE SUPPORT

S77KL16013

STATIC GUCP (REF)

LANYARD

DROPWEIGHT

80K51097

Figure 6.0-1. Tank Vent Umbilical Retraction Mechanism 
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NESC Request No. 05-013-E 

Trunnion 

Pivot Arm 

Withdrawal 

Weight Cable 

Withdrawal Arm 

(Vent Line Centering 

Device) 

Vent Line 

GUCP

Aft Flex Hose 

Facility Hard 

Line

Withdrawal 

Weight 

Figure 6.0-2. Static Lanyard Drop-Weight Function 
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Figure 6.0-3. Umbilical Retention Mechanism 
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7.0 Data Analysis 

7.1 Wind Loading 

Wind force predictions on the GH2 vent arm are extrapolated from the measured winds. Two of 

the most significant measurements are taken using anemometers on top of 60-foot weather 

towers in unobstructed areas 1,200 feet from the Pad in the northwest (NW) and southeast (SE) 

directions. The weather towers are in approximately the same configuration for both Pads A and 

B. The GH2 vent arm is at 220 feet elevation and on the Pad, out of the free stream. Winds at 

the arm are not directly measured. 

The wind loads are calculated using American Society of Civil Engineering (ASCE) 7-98. These 

loads generally are based on the cross-sectional geometry of the vent arm, and the perpendicular 

velocity of the wind to this cross-section. This calculated drag is proportional to the square of 

the wind velocity. For this reason, only high winds perpendicular to the vent pipe will yield loads 

that could result in an anomaly similar to STS-108. This is problematic since there is not a good 

correlation between the measured wind data and the wind speed at the vent arm. For this reason, 

it is recommended that a localized wind measurement system on the vent arm, or in close 

proximity on the Fixed Support System (FSS), be employed. 

There are non-moving, ultrasonic type wind anemometers currently on the market at low cost 

that would not create a debris hazard and could be attached directly to the vent arm to accurately 

assess the wind speed. 

7.2 Kinematics Analysis 

MSFC verified the system kinematics of the ET GH2 Vent Umbilical retraction using an 

independent kinematics model developed in Delmia’s Envision (www.delmia.com). The 

kinematics represented in KSC AT-451 was verified to be consistent with the hardware and 

accurate for nominal and off-nominal situations, such as the STS-108 anomaly. Kinematics 

analysis at MSFC included the haunch pivot arm, trunnions/slider, vent arm, and pivot arm 

retraction weights and shocks. 

The vent arm is guided inside the capture envelope of the Deceleration Unit by two features. 

First, while the vent arm is roughly horizontal, the pivot arm retraction weights center the vent 

arm. A cable attaches a 1,500-lb withdrawal weight to the pivot arm through a pivot, which 

creates equal tension (750 lb) on either side of the cable. The cable is attached to the withdrawal 

arm link that contacts the trunnion and leverages the cable tension. This resulting contact force 
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is 1,500 lbs on the trunnion on either side of the haunch pivot arm creating a restoring moment of 

2,250 ft-lbs. 

The second centering force occurs when the vent arm is not parallel with slots on the pivot arm. 

The Haunch Pivot Arm Slots (HPAS) develop contact force between the slider block, which 

surround the trunnions, as the vent pipe rotates down. The slots in the haunch pivot arm are 

initially parallel with the vent arm pipe while the GUCP is attached to the ET (refer to Figure 

7.2-1). This allows the vent arm to yaw side to side to accommodate the motion of the ET just 

prior to Solid Rocket Booster (SRB) ignition (“twang’). 

Figure 7.2-1 Haunch Pivot Arm Slots (HPAS) 

 The arrow indicates the contact force on the slider blocks from the retraction weights. 

Once the pipe has rotated so that it is no longer parallel with the HPAS (refer to Figure 7.2-2), 

any clearance between with the HPAS and the slider block is initially bottomed out, and out-of-
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plane excursions cause a contact force between the slider block and the top and bottom of the 

HPAS. This contact force bottoms-out one trunnion and drives the other trunnion up the HPAS, 

which will lift the retraction weights as in the first scenario. There will also be an associated 

vent pipe to roll along its axis, which will twist the aft flex line. 

It is expected that the contact forces between the HPAS and the slider blocks vary substantially 

for different operational conditions and could have been very large. If the forces are large 

enough, the slider blocks, HPAS, and the bushings and/or bearings will be damaged. Periodic 

inspections and replacement of this hardware should catch visible damage, but tolerances 

between parts will vary. Wear and tear tolerances were reviewed subsequent to STS-108 and 

documented in the investigation report; this was not considered a significant factor in the 

anomaly. 

Figure 7.2-2. The HPAS at Approximately 40 Degrees to the Vent Arm 

Excursions in this position will cause the vent arm to roll and bend the aft flex base. 

The out-of-plane excursions of the vent pipe, as it enters the deceleration unit, are sensitive to 

torsional flexure of the pivot arm and to any slope in the pivot arm to slider block joint or the 

slider block to trunnion joint. These sensitivities are illustrated in Appendix B. 
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Kinematics of the MSFC model as well as the KSC AT-451 represents idealized motion and 

perfect surface contact between links. Uniqueness of actual parts due to the flaws in the 

manufacturing process, nominal and off-nominal use of the system, wear and tear on the parts, 

bushings and bearings, etc., will create differences between an idealized system and an actual 

system. These differences can be characterized through tests and then be incorporated into the 

computer model for improvement. If it is expected that the system changes due to wear and tear 

or other circumstances, then the computer model should be updated for each expected use. 

Because of the system’s sensitivity to torsion flexure of the pivot arm and potential clearances in 

the joints, it is recommended that a mechanical hanging (fish) scale be utilized to document the 

system stiffness on either side of the Deceleration Units of both Pads A and B (reference A-23 of 

KSC-5600-5969).

7.3 Stiffness Verification 

MSFC independently calculated component stiffness and compared them to the values used in 

the KSC AT-451. The two largest components, most susceptible to flexure are the pivot arm and 

vent arm. The stiffness of these components is critical to predicting the performance of the ET 

GH2 umbilical system in high wind conditions. As there is no validation (empirical measured) 

data for either these components or the performance of the system in as a whole under high wind 

conditions, the verification and validation of the model is incomplete. 

A Finite Element (FE) model of the pivot arm was created using MSC PATRAN®. The FE 

model was subjected to a known torque at the cross-section corresponding to the interface of the 

pivot arm and pivot arm shocks. The resulting angular rotation at this cross-section provides the 

stiffness for the first section of the pivot arm (stiffness between hinge and shock interface 

location) using the formula K = M/T. This approach was then repeated by applying a torque at 

the trunnion location. The angular rotation at the trunnions was then used to compute the overall 

stiffness of the pivot arm. From the following relationship, the second section stiffness (stiffness 

between shock interface location and the trunnions) can be computed as: 1 / Kt = 1 / K1 + 1 / K2.

These stiffnesses were then compared to those used in the KSC AT-451. 

The calculated stiffnesses were 38 percent lower for the first section stiffness and 20 percent 

lower for the second section. This difference was discussed with Roy Burton of USA. It was 

stated that the pivot arm stiffness had to be adjusted by this amount to correlate drop test timing 

results with the model. Pictures of the FE model and the associated calculations are provided in 

Appendix C. 
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A hand-calculated stiffness value of the vent pipe was computed using the known pipe sizes of 

the primary double-walled pipe. This stiffness value was approximately half of the stiffness 

value used in the KSC AT-451. This difference was discussed with Roy Burton/USA and 

resulted in the discovery of erroneous values in the KSC AT-451. The values were corrected in 

the model, but resulted in only minor changes in results. The hand calculations are also provided 

in Appendix C. 

In the post flight investigation, the out-of-plane stiffness of the vent arm was measured while the 

vent arm was hanging vertically from the pivot arm near the Deceleration Unit. It is assumed 

that the pivot arm was latched in the haunch for all of these tests. While this test was performed 

to identify any obvious malfunctions of the system, rather than to characterize the stiffness of the 

system, the results are useful. These tests showed the overall system stiffness to be much less 

than that of any of the components discussed above (reference A-23 of KSC-5600-5969). This 

indicates that the overall out-of-plane system stiffness is dependent on additional factors. A 

mechanical hanging (fish) scale test of the system would validate the overall stiffness employed 

by the model. 
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8.0 Findings, Observations and Recommendations 

8.1 Findings 

While KSC AT-451 represents an exceptional effort at modeling the GH2 vent arm kinetics, it 

has not been substantially validated and relies on estimated wind data, not on measurements 

made at the arm. The relative contribution of the pivot arm shock anomaly to the impact of the 

vent arm on the Deceleration Unit on STS-108 cannot be understood without further testing. 

With regard specifically to lowering the LCC for wind loads, it is recommended that the LCC be 

lowered for future Space Shuttle missions as described in the briefing prepared by Armand 

Gosselin and Gary Hopkins of USA in the interest of safety and conservatism. 

8.2 Recommendations 

If the LCC is to be relaxed to the pre-STS-114 criteria, the Assessment Team recommends the 

following:

R-1. Use a mechanical hanging (fish) scale to measure the flexibility of the vent arm system at 

horizontal, 45 degrees, and vertical. Measurements should be taken at half-inch 

excursion intervals for both Pads A and B, and in both NW and SE directions. This data 

should be used to validate the KSC AT-451. 

R-2. Add a wind measurement device to the vent arm structure. LCC should be based on this 

measurement. 

R-3. Add instrumentation, such as cameras, infrared, targets, etc., as necessary to ascertain the 

motion of the vent arm on future missions, for sustained engineering and on-going 

validation.
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9.0 Lessons Learned 

No significant lessons-learned were generated. 

10.0 Definition of Terms 

Corrective Actions Changes to design processes, work instructions, workmanship practices, 

training, inspections, tests, procedures, specifications, drawings, tools, 

equipment, facilities, resources, or material that result in preventing, 

minimizing, or limiting the potential for recurrence of a problem. 

Finding A conclusion based on facts established during the assessment/inspection 

by the investigating authority.

Lessons Learned Knowledge or understanding gained by experience. The experience may 

be positive, as in a successful test or mission, or negative, as in a mishap 

or failure. A lesson must be significant in that it has real or assumed 

impact on operations; valid in that it is factually and technically correct; 

and applicable in that it identifies a specific design, process, or decision 

that reduces or limits the potential for failures and mishaps, or reinforces a 

positive result. 

Observation A factor, event, or circumstance identified during the 

assessment/inspection that did not contribute to the problem, but if left 

uncorrected has the potential to cause a mishap, injury, or increase the 

severity should a mishap occur. 

Problem The subject of the technical assessment/inspection. 

Requirement An action developed by the assessment/inspection team to correct the 

cause or a deficiency identified during the investigation. The requirements 

will be used in the preparation of the corrective action plan. 

Root Cause Along a chain of events leading to a mishap or close call, the first causal 

action or failure to act that could have been controlled systemically either 

by policy/practice/procedure or individual adherence to 

policy/practice/procedure.

11.0 Minority Report (Dissenting Opinions) 

There were no dissenting opinions during this consultation. 
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Volume II: Appendices

A ITA/I Request Form (NESC-PR-003-FM-01) 

B Vent Arm Sensitivities 

C Hand Calculations 

D List of Acronyms 
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Appendix A. ITA/I Request Form (NESC-PR-003-FM-01) 
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NESC Request No. 05-013-E 
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NESC Request No. 05-013-E 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

1.0

Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

Page #: 

23 of 32

NESC Request No. 05-013-E 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

1.0

Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

Page #: 

24 of 32

NESC Request No. 05-013-E 

Appendix B. Vent Pipe Sensitivities 

Figure B.1. End of Vent Arm as it Enters Deceleration Unit 

Model contains post STS-108 update to the Structure and a horizontal clearance of 19.07”. 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

1.0

Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

Page #: 

25 of 32

NESC Request No. 05-013-E 

Figure B.2. Pivot Arm Flexure Sensitivity 

End of vent arm clearance with the Deceleration Unit when the pivot arm is flexed 3 degrees 

from joint with FSS and joint with Slider Block. Clearance is reduced from 19.07” to 10.5” on 

the modified Deceleration Unit. 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

1.0

Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

Page #: 

26 of 32

NESC Request No. 05-013-E 

Figure B.3. Joint Stop Sensitivity 

End of arm clearance with the Deceleration Unit when the two joints between the pivot arm and 

the Slider Block and the Slider Block and the Trunnions have a combined slope equal to one 

degree. Clearance is reduced from 19.07” to 14.41” on the modified Deceleration Unit. 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

1.0

Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

Page #: 

27 of 32

NESC Request No. 05-013-E 

Appendix C. Pictures of the FE Model and the Associated Calculations 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

1.0

Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

Page #: 

28 of 32

NESC Request No. 05-013-E 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

1.0

Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

Page #: 

29 of 32

NESC Request No. 05-013-E 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

1.0

Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

Page #: 

30 of 32

NESC Request No. 05-013-E 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

1.0

Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

Page #: 

31 of 32

NESC Request No. 05-013-E 

Appendix D. List of Acronyms 

ASCE American Society of Civil Engineering

AT Analytical Tool 

ET External Tank 

FE Finite Element 

FSS Fixed Support System 

GH2 Gaseous Hydrogen

GUCP Ground Umbilical Carrier Panel 

HPAS Haunch Pivot Arm Slot 

KSC Kennedy Space Center 

LC-39 Launch Complex 39 

LCC Launch Commit Criteria 

MSFC Marshall Space Flight Center 

NASA National Aeronautics and Space Administration 

NCE NESC Chief Engineer 

NESC NASA Engineering and Safety Center 

NW Northwest 

SE Southeast 

SRB Solid Rocket Booster 

SSME Space Shuttle Main Engine 

SSP Space Shuttle Program 

USA United Space Alliance 
NASA Engineering and Safety Center 

Technical Assessment Report

Document #: 

RP-05-114

Version: 

1.0

Title:

Kennedy Space Center (KSC) Launch Complex 39 (LC39) Gaseous Hydrogen (GH2) Vent Arm Behavior 

Prediction Model Review Technical Assessment Report

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NESC Request No. 05-013-E 

Approval and Document Revision History 

Approved: Original signed on file 10/17/05

NESC Director Date

Version Description of Revision Office of Primary 

Responsibility

Effective

Date

1.0 Initial Release NESC Chief Engineer’s 

Office

10/17/05
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Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std. Z39-18 

01-03-2009 Technical Memorandum March 2005- October 2005

Kennedy Space Center (KSC) Launch Complex 39 (LC-39) Gaseous

Hydrogen (GH2) Vent Arm Behavior Prediction Model Review Technical

Assessment Report

510505.01.07.01.06

Wilson, Timmy R.; Beech, Geoffrey; Johnston, Ian.

NASA Engineering and Safety Center

Langley Research Center

Hampton, VA 23681-2199

L-19605 NESC-RP-05-114/05-013-E

National Aeronautics and Space Administration

Washington, DC 20546-0001

NASA

NASA/TM-2009-215570

Unclassified - Unlimited

Subject Category 20 Spacecraft Propulsion And Power

The NESC Assessment Team reviewed a computer simulation of the LC-39 External Tank (ET) GH2 Vent Umbilical system

developed by United Space Alliance (USA) for the Space Shuttle Program (SSP) and designated KSC Analytical Tool ID 451

(KSC AT-451). The team verified that the vent arm kinematics were correctly modeled, but noted that there were relevant system

sensitivities. Also, the structural stiffness used in the math model varied somewhat from the analytic calculations. Results of the

NESC assessment were communicated to the model developers.

ET, GH2, GUCP, LC-39, SSP

UU UU UU UU 37

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