October 2014 

NASA/TM2014-218542 

NESC-RP-13-00921 

 

International Space Station (ISS) External 

Thermal Control System (ETCS) Loop A Pump 

Module (PM) Jettison Options Assessment 

Daniel G. Murri/NESC

Langley Research Center, Hampton, Virginia 

Alicia Dwyer Cianciolo

Langley Research Center, Hampton, Virginia 

Jeremy D. Shidner and Richard W. Powell

Analytical Mechanics Associates, Hampton, Virginia 
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October 2014 

NASA/TM2014-218542 

NESC-RP-13-00921 

 

International Space Station (ISS) External 

Thermal Control System (ETCS) Loop A Pump 

Module (PM) Jettison Options Assessment 

Daniel G. Murri/NESC

Langley Research Center, Hampton, Virginia 

Alicia Dwyer Cianciolo

Langley Research Center, Hampton, Virginia 

Jeremy D. Shidner and Richard W. Powell

Analytical Mechanics Associates, Hampton, Virginia 
Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 

Acknowledgments 

The team would like to acknowledge Forrest Lumpkin, Randy Thurman, Ryan 

Eastand, and James Fenner for their contributions. 

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. 
NASA Engineering and Safety Center 

Technical Assessment Report 

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NESC-RP13-00921 

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NESC Request No.: TI-13-00921 (ISS Pump Module Jettison) 

International Space Station (ISS) External Thermal Control System 

(ETCS) Loop A Pump Module (PM) Jettison Options Assessment

September 18, 2014
NASA Engineering and Safety Center 

Technical Assessment Report 

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NESC Request No.: TI-13-00921 (ISS Pump Module Jettison) 

Report Approval and Revision History 

NOTE: This document was approved at the September 18, 2014, NRB. This document was 

submitted to the NESC Director on September 22, 2014, for configuration control. 

Approved: 

NESC Director Date 

Version Description of Revision Office of Primary 

Responsibility Effective Date 

1.0 Initial Release Daniel Murri, NASA 

Technical Fellow for 

Flight Mechanics, 

LaRC 

9/18/14 

0SJHJOBM4JHOBUVSFPO'JMF 
NASA Engineering and Safety Center 

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Table of Contents 

Technical Assessment Report 

1.0 Notification and Authorization ........................................................................................ 5

2.0 Signature Page ................................................................................................................... 6

3.0 Team List ........................................................................................................................... 7

3.1 Acknowledgements ................................................................................................. 7

4.0 Executive Summary .......................................................................................................... 8

5.0 Jettison Options and Assumptions .................................................................................. 9

6.0 Data Analysis ..................................................................................................................... 9

6.1 Independent Trajectory Simulation ......................................................................... 9

6.2 Analysis................................................................................................................. 11

6.2.1 Determining BN for ISS and PM .......................................................................... 11

6.2.1.1 PM Mass ............................................................................................................... 11

6.2.1.2 ISS BN .................................................................................................................. 13

6.2.2 Results ................................................................................................................... 14

6.2.2.1 Results –Posigrade PM Jettison ............................................................................ 14

6.2.2.2 Results – Retrograde PM Jettison ......................................................................... 16

6.2.2.3 Results – Sensitivity Studies ................................................................................. 18

6.2.2.4 Results - Monte Carlo Analysis ............................................................................ 20

6.2.3 Verification ........................................................................................................... 23

6.2.4 Animation ............................................................................................................. 26

7.0 Findings, Observations, and NESC Recommendations .............................................. 28

7.1 Findings................................................................................................................. 28

7.2 Observations ......................................................................................................... 29

7.3 NESC Recommendations...................................................................................... 29

8.0 Definition of Terms ......................................................................................................... 29

9.0 Acronyms List ................................................................................................................. 30

10.0 References ........................................................................................................................ 31

List of Figures 

Figure 6.1-1. Reference Frames.................................................................................................. 10

Figure 6.2-1. Posigrade Jettison Cone ........................................................................................ 15

Figure 6.2-2. Separation Distances of PM from ISS - Posigrade Jettisons ................................ 15

Figure 6.2-3. Separation Distances of PM from ISS - Retrograde Jettisons .............................. 16

Figure 6.2-4. TOPO Retrograde Jettison Trajectory Ranges for Separation Velocity of 

0.05 m/s ................................................................................................................. 17

Figure 6.2-5. Comparison of PM with Different BN.................................................................. 18

Figure 6.2-6. Separation Distance of PM from ISS for Different Atmospheric Settings ........... 20

Figure 6.2-7. Posigrade MC Results ........................................................................................... 22
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Figure 6.2-8. Retrograde MC Results ......................................................................................... 23

Figure 6.2-9. Comparison of STK and POST2 - Posigrade 0.05 m/s Jettison ........................... 24

Figure 6.2-10. Comparison of STK and POST2 - Posigrade 0.2 m/s Jettison ............................. 25

Figure 6.2-11. Comparison of STK and POST2 - Retrograde 0.05 m/s Jettison ......................... 25

Figure 6.2-12. Comparison of STK and POST2 - Retrograde 0.2 m/s Jettison ........................... 26

Figure 6.2-13. ISS Representation in EVE ................................................................................... 27

Figure 6.2-14. EVE Animations of the PM Motion Relative to ISS ............................................ 27

List of Tables 

Table 6.1-1. Simulation Assumptions ....................................................................................... 11

Table 6.2-1. VIPER PM Mass and Area Values ....................................................................... 12

Table 6.2-2. TOPO PM Mass and Area Values ........................................................................ 12

Table 6.2-3. PM Mass Inconsistencies ...................................................................................... 13

Table 6.2-4. Results of Integration and Time Step Sensitivity Study ....................................... 19

Table 6.2-5. Results of the Gravity Field Resolution Sensitivity Study ................................... 19

Table 6.2-6. Suggested PM MC Parameters ............................................................................. 21
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Technical Assessment Report 

1.0 Notification and Authorization 

The NASA Engineering and Safety Center (NESC) received a request to support the 

International Space Station (ISS) Pump Module (PM) Jettison Assessment on December 16, 

2013. 

Mr. Daniel Murri, NASA Technical Fellow for Flight Mechanics at the NASA Langley Research 

Center (LaRC), was selected to lead this assessment. Mrs. Alicia Dwyer Cianciolo (LaRC) was 

selected as the technical lead. 

The key stakeholder for this assessment was the ISS Program. 
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2.0 Signature Page 

Submitted by: 

Mr. Daniel Murri Date 

Significant Contributors: 

Ms. Alicia Dwyer Cianciolo Date Mr. Jeremy D. Shidner Date 

Mr. Richard Powell Date 

Signatories declare the findings, observations, and NESC recommendations compiled in the 

report are factually based from data extracted from program/project documents, contractor 

reports, and open literature, and/or generated from independently conducted tests, analyses, and 

inspections. 

5FBN4JHOBUVSF1BHFPO'JMF
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3.0 Team List 

Name Discipline Organization 

Core Team 

Daniel Murri Lead, NASA Technical Fellow for Flight 

Mechanics 

LaRC 

Alicia Dwyer Cianciolo 

Technical Lead, Flight Mechanics and 

Trajectory Design LaRC 

Jeremy Shidner Flight Mechanics and Trajectory Design LaRC/AMA 

Richard Powell Flight Mechanics and Trajectory Design LaRC/AMA 

Scott Angster Flight Animation LaRC/AMA 

Sarah Rieger Flight Mechanics and Trajectory Design JSC 

Christopher Cerimele Branch Chief JSC 

Consultants 

Joe Pascucci DM33/ISS Trajectory Operations JSC/ULA 

Yared Mesfin 

Senior Technical Lead, Boeing ISS 

Guidance, Navigation, and Control 

(GN&C) JSC/Boeing 

Charles Gray VIPER Systems Analysis & Integration JSC/ Booz Allen Hamilton 

Neil Dennehy NASA Technical Fellow for GN&C GSFC 

Dave Schuster NASA Technical Fellow for Aerosciences LaRC 

Administrative 

Stephanie Hamrick MTSO Program Analyst LaRC 

Erin Moran Technical Writer LaRC/AMA 

3.1 Acknowledgements 

The team would like to acknowledge Forrest Lumpkin, Randy Thurman, Ryan Eastand, and 

James Fenner for their contributions. 
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4.0 Executive Summary 

On December 11, 2013, the International Space Station (ISS) experienced a failure of the 

External Thermal Control System (ETCS) Loop A Pump Module (PM). To minimize the 

number of extravehicular activities (EVA) required to replace the PM, jettisoning the faulty 

pump was evaluated. The objective of this study was to independently evaluate the jettison 

options considered by the ISS Trajectory Operations Officer (TOPO) and to provide 

recommendations for safe jettison of the ETCS Loop A PM. 

The simulation selected to evaluate the TOPO options was the NASA Engineering and Safety 

Center’s (NESC) version of Program to Optimize Simulated Trajectories II (POST2) developed 

to support another NESC assessment1

. The objective of the jettison analysis was twofold: (1) to 

independently verify TOPO posigrade and retrograde jettison results, and (2) to determine 

jettison guidelines based on additional sensitivity, trade study, and Monte Carlo (MC) analysis 

that would prevent PM recontact. Recontact in this study designates a propagated PM trajectory 

that comes within 500 m of the ISS propagated trajectory. An additional simulation using 

Systems Tool Kit (STK) was run for independent verification of the POST2 simulation results. 

Ultimately, the ISS Program removed the PM jettison option from consideration. However, prior 

to the Program decision, the retrograde jettison option remained part of the EVA contingency 

plan. 

The jettison analysis presented showed that, in addition to separation velocity/direction and the 

atmosphere conditions, the key variables in determining the time to recontact the ISS is highly 

dependent on the ballistic number (BN) difference between the object being jettisoned and the 

ISS. 

 

1 Development of Verification Data for Flight Simulation (NESC #TI-12-00770)
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5.0 Jettison Options and Assumptions 

The jettison options include posigrade (i.e., in the direction of ISS motion) or retrograde (i.e., in 

the opposite direction of ISS motion). To ensure continuous separation of the jettisoned ETCS 

Loop A PM and the orbiting ISS, there must be a minimum BN difference between the objects. 

The BN is given by equation 1: 

 BN = M/(CD*A) (EQ. 1) 

where M is the vehicle mass, CD is the vehicle drag coefficient, and A is the area exposed to the 

flow. 

Posigrade jettison is advantageous for cases where the PM BN is greater than the ISS BN. 

Examples are provided in Section 6. A posigrade PM jettison would be performed at the EVA 

worksite. 

Retrograde jettison is better for PM BNs less than the ISS BN. For the faulty PM, the retrograde 

jettison would be done using the robotic arm from the nadir side truss below the worksite. The 

EVA crew preferred the retrograde option because it provided a better viewing angle during 

initial release. 

Other jettison assumptions included the ISS jettison policy2

 of a minimum separation speed of 

0.05 m/s. This speed is considered worst-case and represents a “drift away” scenario. Although 

past experience has shown that 0.2 m/s is reasonable, EVA performance is based on a braced and 

pushed case. Additionally, the ISS jettison policy requires the assessment of a 30-degree half 

cone angle from the nominal jettison direction, the starboard solar array rotary joint (SARJ) at 

195 degrees, and the PM recontact time (i.e., the time it takes for a propagated PM trajectory to 

come within 500 m of the propagated ISS trajectory) has to be greater than 10 days. This time 

requirement is to accommodate an ISS reboost to avoid recontact. 

6.0 Data Analysis 

6.1 Independent Trajectory Simulation 

The simulation tool selected to evaluate the TOPO options was the NESC’s version of POST2, 

which was developed to support another NESC assessment3

. The simulation was developed to 

model the ISS orbit propagation using the Distributed Space Exploration Simulation Test Plan 

[ref. 1]. The simulation has been demonstrated to provide comparable results to the Johnson 

Space Center (JSC) Trick simulation framework [ref. 2] and was configured with the states and 

models needed to perform the jettison analysis. 

The POST2 simulation models include: 

x Lunar and Solar point mass 3rd body perturbations (i.e., SPICE toolkit using the Jet 

Propulsion Laboratory (JPL) DE405 ephemeris). 

 

2 http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080047307.pdf

3 Development of Verification Data for Flight Simulation (NESC #TI-12-00770)
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x Goddard Earth Model (GEM-T1) Gravity Field (8 × 8). 

x Marshall Engineering Thermal (MET) Model Atmosphere. 

x 3-Degree of Freedom Aerodynamic Drag Only. 

x Non-varying BN (i.e., PM was not tumbling). 

The reference frame used to initialize orientation is the ISS-defined local orbital (i.e., local 

vertical, local horizontal (LVLH)) coordinate system [ref. 3]. The LVLH frame defines the 

+Z-axis as the radial vector toward Earth and the +Y-axis as normal to the orbit plane, as shown 

in the left side of Figure 6.1-1. The ISS Design Reference Frame (DRF), or the Space Station 

Analysis Coordinate System [ref. 3] shown in right side of Figure 6.1-1, has +X-axis (i.e., red 

arrow) initially aligned with +XLVLH, and +Z-axis (i.e., blue arrow) initially aligned along the 

radial vector, +ZLVLH. For purposes in this analysis, the DRF and LVLH frame were assumed to 

be coincident. However, these reference coordinate systems are offset on the order of 5 degrees 

as detailed at the ISS attitude planning website [ref. 4]. The jettison direction is calculated as a 

3(yaw)-2(pitch) Euler angle sequence from the ISS DRF, where the positive yaw direction will 

rotate the jettison object to the right of the ISS, and a positive pitch direction will rotate the 

jettison object above the ISS. 

Figure 6.1-1. Reference Frames 

(Left) LVLH and (Right) Station DRF depictions. 

The nominal simulation assumptions listed in Table 6.1-1 were derived from various sources, 

including: the TOPO assumptions for atmosphere inferred to use max MET values from the 

model, TOPO values for ISS and PM mass, website queries from operational assessments of ISS 

location [ref. 5], and locations of jettison from ISS model inquiries using Exploration 

Visualization Environment (EVE). EVE is a simulation, visualization, and analysis tool 

developed to integrate potentially disparate time-based data with detailed graphical models in a 

real-time virtual environment. Details of the animation tool and its application to this study are 

described in Section 6.2.4. 
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Table 6.1-1. Simulation Assumptions 

Category Parameter Value 

Epoch 2013-352/12:00:00.000 UTC' 

Initial State J2000 Position 3414153.57, 3560080.97, 4670109.53 m 

J2000 Velocity -2847.347311, 6505.836888, -2871.765151 m/s 

F10.7 (Max) 250 

MET Atmosphere Geomagnetic Index (Max) 25 

F10.7 (Mean) 118.0 

Geomagnetic Index (Mean) 1.827 

PM Mass 360.25 kg 

Mass Properties PM Reference Area (Mean) 1.6 m2

ISS Mass 413,309.469 kg 

ISS Reference Area (Mean) 1836.8 m2

Gravitational Constant 3.98600436e14 kg/m3

Rotation Rate 7.29211514670638e-5 rad/s 

Planet Parameters GEM-T1 Gravity Field 8 x 8 order 

Equatorial Radius 6,378,137.0 m 

Polar Radius 6,356,755.38082467 m 

Aerodynamics PM Drag Coefficient 2.0 

ISS Drag Coefficient 2.07 

Pushoff Location Posigrade (DRF) 2, 14, 0 m 

Retrograde (DRF) 0, 14, 10 m 

6.2 Analysis 

The simulation described in Section 6.1 was used to evaluate the PM jettison options. The 

objective of the jettison analysis was twofold: (1) to independently verify TOPO posigrade and 

retrograde jettison results, and (2) to determine general jettison guidelines based on additional 

sensitivity, trade study, and MC analysis that would prevent PM recontact (i.e., approaching 

within 500 m) with the ISS for at least 10 days. The major consideration to determine the time to 

recontact was the BN difference between the PM and the ISS. The analysis accuracy depended 

on the PM and ISS BN accuracy. The ISS BN could be varied with solar array actuation. 

6.2.1 Determining BN for ISS and PM 

This section presents the determination and effect of ISS and PM BNs, and a summary of the 

sensitivity, trade studies, and MC analysis performed. 

It became evident early in this study that characterizing the PM and ISS BNs would be critical to 

determine the time to recontact. This section summarizes what is known about the PM mass and 

volume and the characterization of and mitigation options for the ISS BN. 

6.2.1.1 PM Mass 

The team received two sets of ISS and PM mass and dimension values. The first set included 

values from the Vehicle Integrated Performance Environments and Resources (VIPER) [ref. 6] 

and are provided in Table 6.2-1. The second set was provided by the TOPO and is shown in 

Table 6.2-2. 
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Table 6.2-1. VIPER PM Mass and Area Values [ref. 7] 

Object Mass 

(kg) 

Dimensions 

(m) 

Area 

(m2) 

BN 

(kg/m2) 

ISS 2013 100.0 

Pump Module 360.25 1.750 × 1.270 × 0.910 

Minimum Area 1.16 155.1 

Average Area 1.60 112.4 

Maximum Area 2.23 80.9 

Table 6.2-2. TOPO PM Mass and Area Values [ref. 7] 

Object Mass 

(kg) 

Dimensions 

(m) 

Area 

(m2) 

BN 

(kg/m2) 

ISS 413,309.5 1836.8 108.7 

Pump Module 413.7 1.524 × 1.245 × 0.787 

Minimum Area 0.6 344 

Average Area 1.159 178 

Maximum Area

1.897 109 

To resolve the PM mass and dimension differences, Randy Thurman, and Charlie Gray (JSC-ISS 

Operations) [Barrios Technology, Ltd.], were consulted. Both Thurman and Gray confirmed that 

the PM dimensions were 68.1 × 50.0 × 35.7 in (1.73 × 1.27 × 0.91 m) and consistent with the 

VIPER data. Thurman commented the PM dimensions were accurate to about ±1 inch [refs. 8, 

9]. 

Thurman stated the dry mass of the PM was 919 lbm (417.2 kg). However, because loop system 

pressure was reduced prior to removal, the PM accumulator to mostly empty and the PM wet 

mass would be 935 lbm (424.5 kg), including approximately 16 lbm (7.3 kg) of residual 

ammonia. Gray indicated the 358.9 kg wet mass number was correct, and indicated the 935-lbm 

number included the flight support equipment (FSE), which weighs 182.93 lbs (83 kg). The FSE 

would not be jettisoned with the PM. However, there is a credible contingency scenario that a 

75-lbm (34-kg) grapple bar would be attached to the PM and should be included in total jettison 

mass. Table 6.2-3 attempts to capture the PM mass components to identify which should be 

included in the calculation of the BN. By accounting for the residual ammonia and grapple bar 

as part of the jettison mass, the estimated PM mass was between 357.4 and 368.2 kg. It is noted 

the margined VIPER (±10 lbm) mass falls between the range. 
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Table 6.2-3. PM Mass Inconsistencies 

VIPER Wet Mass TOPO Mass Wet mass from Thurman Component 

413.7 kg 424.5 kg 

-83.0 kg -83.0 kg FSE - not jettison 

+34.0 kg +34.0 kg Grapple bar is jettison 

364.7 kg 375.5 WET MASS 

-7.3 kg -7.3 kg Residual Ammonia 

357.4 kg 368.2 kg DRY MASS 

358.9 kg ±4.54 kg 

There was an inconsistency recognized with the minimum area provided with the TOPO values 

provided in Table 6.2-2. The stated 0.6-m2

 does not correspond to the area of the minimum 

TOPO dimensions (1.245 × 0.787 = 0.979 m2

). Likewise, it is unclear how the average area was 

determined in the TOPO and VIPER data. Assuming a CD = 2 in the BN calculation, the average 

PM area in the VIPER data should be approximately 1.69 m2. This area results in an average BN 

of approximately 106 kg/m2

 versus the VIPER value of 112 kg/m2. This difference, shown in 

Section 6.2.2, is important when determining the recontact time and deciding whether to perform 

a posigrade or retrograde jettison. 

6.2.1.2 ISS BN 

The TOPO develops orbit averaged frontal array areas for each ISS configuration involving five 

ranges of solar beta angles, with and without drag reduction enabled. The orbital averaging takes 

into account alpha joints motion (e.g., SARJs), which go through one "cycle" per orbit. In the 

"no drag reduction" mode, the SARJs go through one rotation at a constant rate for the orbit. 

The drag reduction mode is the normal ISS operational mode. This joint rotation with the use of 

the beta gimbals, which account for the effect of the angle of the Sun to the orbital plane, keep 

the arrays pointed at the Sun when not in eclipse. With drag reduction enabled, strategies were 

employed to reduce the drag. This includes feathering the arrays when in eclipse, and trading 

power production by off pointing from the Sun. The strategy is repeated every orbit producing 

periodic array operations with orbital frequency. The specific strategies vary depending on the 

beta angle. 

The TOPO computes the expected projected areas for the next several years, which is updated 

quarterly. Using these projections, examples of the ISS BN effects resulting from changes in 

assumed array orientations are obtained. 

The 1836.8-m2

 in the "nominal case" (Table 6.2-2) corresponds to the ISS configuration for a 

beta angle (i.e., absolute value) range of 0 to 15 degrees. As the absolute value of beta increased 

over a 2-week period, the solar beta magnitude exceeded 60 degrees on December 30, 2013. The 

projected area will decrease as the beta gimbal angles point the arrays more into the ISS 

Y-direction to direct them at the Sun. This orientation feathers the arrays with respect to the ISS 

velocity vector, which is nearly aligned with the ISS X-axis. For example, for the beta range of 

60 to 75 degrees (i.e., the maximum range in the TOPO tables), the projected area reduces to 
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1299.3 m2. Alternatively, if drag reduction is disabled for the 0 to 15 degree beta range, the 

projected area increases to 2321.9 m2. 

Along with changes to the ISS projected area, the vehicle experiences variations in drag 

coefficient that range between 2.04 and 2.2 [ref. 10]. 

Therefore, the BNs for these three cases are: 

Nominal case 108.7 kg/m2

High beta, drag reduction 153.7 kg/m2

Low beta, no drag reduction 86.0 kg/m2

If the jettison option is selected, then a retrograde release is the best option, allowing for efforts 

to lower ISS drag. It could also be desirable to combine a retrograde jettison with a preemptive 

debris avoidance maneuver (i.e., in effect a re-boost) to reduce the likelihood of PM recontact. 

6.2.2 Results 

Using the simulation described in Section 6.1, the PM mass, and PM and ISS BN uncertainties, 

the analysis for comparison with the TOPO provided nominal trajectories utilizes following 

assumptions: 

x BN

• ISS – 108.7 kg/m2

• PM minimum – 80.9 kg/m2

• PM average – 112.4 kg/m2

• PM maximum – 155.1 kg/m2

x Pushoff velocity for 0.05 and 0.20 m/s

x Posigrade pushoff attitude

• Pitch = 30 degrees, Yaw = -15 degrees 

x Retrograde pushoff attitude

• Pitch = -30 degrees, Yaw = 160 degrees 

6.2.2.1 Results – Posigrade PM Jettison 

For each pushoff attitude, a nominal set of dispersed trajectories was considered. The 

trajectories, obtained by taking a sweep of clock angles from 0 to 360 degrees in 30-degree 

increments with a constant 30-degree cone angle from the nominal 30-degree pitch and 

-15-degree yaw angles, are shown in Figure 6.2-1. 
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Figure 6.2-1. Posigrade Jettison Cone [ref. 7] 

The results of the posigrade jettison dispersed trajectories are shown in Figure 6.2-2. This figure 

illustrates the difference in range, or distance between the PM and the ISS, for a posigrade 

separation using two different pushoff velocities. The left side of Figure 6.2-2 illustrates the 

range after 10 days using the minimum pushoff velocity of 0.05 m/s. If the PM has a BN near 

80 kg/m2

 (shown in green), which is less than the assumed average ISS BN of 108 kg/m2, then it 

could recontact the ISS in less than 1 day. However, if the PM BN is greater than the ISS BN, 

then recontact will take longer than 10 days. Recontact designates a propagated PM trajectory 

that comes within 500 m of the ISS propagated trajectory. The right side of Figure 6.2-2 

illustrates the effect of increasing the pushoff velocity to 0.2 m/s. In this case, the possibility of 

PM recontact, for PM BNs less than the ISS, is extended to almost 3 days. 

Therefore, in the cases of posigrade jettison, the jettison object must have a BN greater than that 

of the ISS to maximize the time to recontact. 

Figure 6.2-2. Separation Distances of PM from ISS - Posigrade Jettisons 

Figures on the left and right show results using 0.05 and 0.2 m/s separation velocity, respectively. 
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6.2.2.2 Results – Retrograde PM Jettison 

Figure 6.2-3 shows the range between the ISS and PM after 10 days for the case of retrograde 

jettison with the pushoff velocities (left: 0.05 m/s, right: 0.2 m/s) considered in the posigrade 

analysis. The sweep of clock angles (i.e., 0 to 360 degrees in 30-degree increments) is the same 

as those used in the posigrade analysis. However, the nominal retrograde pitch angle is 

-30 degrees and the nominal yaw angle is 160 degrees. In this case, the PM BN near 155 kg/m2

predicts recontacts in just over 1 day. Therefore, to ensure positive separation of a retrograde 

jettison, the PM BN must be less than the ISS BN to prevent recontact in 10 days. However, 

similar to posigrade jettison analysis, the increase in separation velocity does delay the time to 

recontact. This analysis highlights the substantial effect that a BN mismatch and, to a lesser 

extent, the effect of jettison velocity can have on ISS recontact time. 

Figure 6.2-3. Separation Distances of PM from ISS - Retrograde Jettisons 

Figures on the left and right show results using 0.05 and 0.2 m/s separation velocity, respectively. 

One purpose of the analysis was to verify TOPO trajectories for similar trajectory conditions. 

Figure 6.2-4 is an example of the TOPO provided trajectory results for retrograde jettison 

analysis using the 0.05-m/s separation velocity and similar PM BN range. Though the plots are 

on different scales, Figure 6.2-4 and the left side of Figure 6.2-3 show the PM returning for 

particular cases in just over 1 day, while lower PM ballistic trajectories maintain positive 

separation during the same time period. 
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Figure 6.2-4. TOPO Retrograde Jettison Trajectory Ranges for Separation Velocity of 0.05 m/s 

Having validated TOPO results, and with the retrograde jettison option remaining as part of the 

contingency, additional analyses were performed using only retrograde jettison. 

Recognizing the significant impact of the BN difference on time to recontact, a study was 

performed to determine the BN difference required to prevent recontact for 10 days using a 

0.2-m/s separation velocity. The retrograde case with a 0.2-m/s jettison velocity and a BN of 

155 kg/m2

 that returned in the shortest time (~3.5 days) had a pitch angle of -30 degrees, a yaw 

of 160 degrees, a clock angle of 30 degrees, and a cone angle of 210 degrees. This case is shown 

in blue in Figure 6.2-5. To delay recontact to 10 days, PM BN must be less than 120 kg/m2

. 

This case is shown in red in Figure 6.2-5. Since BN is a function of mass and area, and 

assuming a constant drag coefficient CD = 2, the PM would require an area increase of 

approximately 0.34 m2, or a mass reduction of 82 kg to achieve the a BN of 120 kg/m2 . Though 

some mass reduction could be gained by draining the remaining ammonia, it is not likely the PM 

mass could be reduced to this level. The more likely mitigation technique would be to add a 

drag device (e.g., inflatable, tethered balloon, etc.). 

Currently, there are no simple solutions available on the ISS to increase a jettison objects drag 

area. One recommendation from this study (i.e., R-6) is to consider development and crew 

training to use some type of deployable decelerator specifically for these situations. 
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In addition to drag mitigation features for the jettison object, there are ISS BN drag mitigation 

options (see Section 6.2.1.2) that should be considered if the jettison options are exercised. 

Further work is needed to characterize how much ISS drag mitigation would be needed on each 

orbit and for how many orbits. The result will likely be jettison case-specific. 

Figure 6.2-5. Comparison of PM with Different BN 

The BN of the object was reduced from 155 kg/m2 to 120 kg/m2 to illustrate the effect BN number has 

on the time to recontact. 

6.2.2.3 Results – Sensitivity Studies 

To understand simulation sensitivities, additional analyses were performed to characterize the 

PM/ISS range at 10 days to the effects of simulation integration step size, gravity model, and 

atmosphere. The analysis considered effects on the nominal trajectory defined in Section 6.2.2 

(i.e., ISS BN = 108.7 kg/m2; PM BN = 112.4 kg/m2, pushoff pitch angle = -30 degrees, pushoff 

yaw angle = 160 degrees, pushoff velocity = 0.05 m/s). The results are provided in the following 

three subsections. 

Sensitivity to Simulation Integration Step Size 

Due to the time being considered for orbit propagation (i.e., 10 days), it was important to 

understand the effect of and differences in propagated trajectories due to the simulation 

integration type and step size. Three integrators were evaluated in the POST2 simulation: 

Runge-Kutta 4, Runge-Kutta 8, and Enche using a Runge-Kutta 4 at start up. Additionally, three 

time steps were considered: 0.1 s, 1.0 s, and 10 s. The ISS-to-PM range difference after 10 days 

is shown in Table 6.2-4. Note the Runge-Kutta 8 simulation with a 0.1-s time step took the 

longest to complete. As the results indicate, integration type and step size do not have a 

substantial effect on the propagation results. Therefore, the Runge-Kutta 4 with a 1-s time step 

was used for the remaining analyses. 
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Table 6.2-4. Results of Integration and Time Step Sensitivity Study 

Integrator with time step Resulting difference in PM to ISS 

distance after 10 days (m)

Range (RK4, dt = 0.1) – Range (RK4, dt = 1.0) 0.003 

Range (RK4, dt = 10) – Range (RK4, dt = 1.0) 0.4 

Range (RK8, dt = 0.1) – Range (RK8, dt =1.0) 0.03 

Range (RK8, dt = 10) – Range (RK8, dt = 1.0) 0.09 

Range (Enche + RK4, dt = 0.1) – Range (Enche + RK4, dt =1.0) 0.006 

Range (Enche + RK4, dt = 10) – Range (Enche + RK4, dt = 1.0) 0.3 

Sensitivity to Gravity Model 

A second sensitivity study compared the ISS and PM propagated range after 10 days considering 

gravity models of different resolution. The three resolutions considered were 4 × 4, 8 × 8, and 

36 × 36 order fields. The GEM-T1 gravity model was used for the analysis as it extends to a 

360 × 360 order field resolution. The highest resolution currently available in the POST2 

simulation was the 36 × 36. Should longer propagation periods be considered, higher order 

gravity models may be necessary. The nominal simulation was run changing only the gravity 

resolution. The difference in PM and ISS distance at the end of 10 days was compared with the 

results shown in Table 6.2-5. The effect of increasing the gravity model resolution was a 

difference in propagated range at the end of 10 days of only about 50 m. Therefore, only the 

4 × 4 model was used for the study. 

Table 6.2-5. Results of the Gravity Field Resolution Sensitivity Study 

Gravity Models Resulting difference in PM to ISS 

distance after 10 days (m)

Range (8 × 8) – Range (4 × 4) 40.3 

Range (36 × 36) – Range (8 × 8) 7.3 

Sensitivity to Atmosphere 

The atmosphere model used in the POST2 simulation was the MET model, which is a modified 

Jacchia 1970 model [ref. 11]. In this model, the daily solar flux 10.7 cm can be varied 

(i.e., minimum = 70, mean = 128.8, maximum = 250.0) as can the geomagnetic index 

(i.e., minimum = 0.0, mean = 15.7, maximum = 25.0). Therefore, the atmosphere sensitivity 

study considered the effect of the maximum, minimum, and mean atmosphere settings on the PM 

and ISS separation range trajectories for posigrade and retrograde jettison simulations assuming 

a PM BN of 112.4 kg/m2

 and a ISS BN of 108.7 kg/m2. The plots in Figure 6.2-6 show the 

difference in range at the end of 10 days for both cases. The minimum atmosphere settings 

(i.e., generating the least atmospheric density and drag) result in posigrade jettison encountering 

the ISS sooner. In this case, since the BN of the PM is higher than the ISS, the lower density 

slows the separation as compared to higher density atmosphere. The maximum atmosphere 

settings (i.e., highest density) stress the retrograde jettison because the higher drag allows the 

PM, with a higher BN than the ISS, to overtake the ISS more quickly and results in potential 

recontact sooner than a low-density (i.e., low-drag) atmosphere. It is expected that these results 
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would be reversed if the PM BN were lower than the ISS BN. The atmosphere conditions at the 

time of the study recorded the F10.7 to be near 118.0, and a geomagnetic index of approximately 

1.827 [ref. 5]. 

Figure 6.2-6. Separation Distance of PM from ISS for Different Atmospheric Settings 

ISS versus PM range using different atmosphere settings for (left) posigrade jettison and (right) 

retrograde jettison. 

It is important to note the “stress” case atmosphere is different for posigrade jettison than for 

retrograde jettison scenarios and should be considered when evaluating jettison options. 

6.2.2.4 MC Analysis Results 

Simplified analysis can reveal the initial implications of the mass, area, and drag coefficient 

dispersions. Figure 6.2-5 illustrated that a 30-percent decrease in BN can increase the recontact 

time from 3.5 to almost 10 days. Throughout this study, it was evident the PM mass, mean 

projected area, and drag coefficient are not consistently defined. The uncertainty in PM mass, 

area and drag coefficient effect the BN and the calculation of recontact time. Consider a 

10-percent variation in the PM mass, area, and drag coefficient. A 10-percent change in any 

single PM BN quantity while the others remain at their nominal value would result in a 

10-percent BN change. However, a 10 percent increase in mass with area and drag dispersions 

that are 10 percent lower than the nominal result in a 35-percent difference in PM BN. Likewise, 

a 10 percent decrease in mass dispersion with area and drag dispersions that are 10 percent high 

result in a 25 percent difference in PM BN from the nominal. This simplified BN sensitivity 

analysis demonstrates the impact of parameter variations on calculating time to recontact. It 

highlights the importance of obtaining a precise knowledge of the ISS BN and drag mitigations 

options that factor into time to recontact calculations. 

To assess the impact of additional dispersions affecting the ISS-to-PM range after 10 days in 

more detail, relevant MC parameters were identified. The primary parameters with their 

considered nominal values, perturbations, and dispersions are provided in Table 6.2-6. The 
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purpose of the MC analysis was to review the nominal values and dispersions to determine 

optimal PM jettison options. 

Table 6.2-6. Suggested PM MC Parameters 

Parameter Nominal Perturbation Distribution Rationale 

Mass Properties 

PM Mass (kg) 424.49 417.23 to 

429.03 

Uniform Randall Thurman email 12/15/13: 

“dimensions should be good to within 5-10 

lbm... Weight/Mass 919 lbm dry; 935 lbm 

with ammonia when removed from system 

(only 16 lbm residual ammonia because 

loop system pressure is reduced prior to 

removal, causing the PM accumulator to 

mostly empty).” 

PM Area: in (m2) 4 1.10 to 2.28 Uniform Randall Thurman email 12/15/13: 

“dimensions should be good to about 

+/- one inch...Envelope dimension 

(inches): 68.1 x 50.0 x 35.7” 

PM BN (kg/m2) 91.62 to 195.55 Not explicitly dispersed 

Aerodynamics 

PM Drag 

Coefficient CD

2 1.8:2 Uniform If drag coefficient goes down, then need 

more area and less mass to keep PM BN > 

ISS BN 

Jettison Velocity 

Velocity (m/s) 0.2 0.1 to 0.25 Uniform 0.05 m/s policy min is unrealistically low 

Initial Attitude 

Posigrade cone 

angle (degrees) 

0 -30:30 Uniform 30 degree half angle cone – Jettison Policy 

Posigrade clock 

angle (degrees) 

0 0:360 Uniform 

Retrograde cone 

angle (degrees) 

0 -30:30 Uniform 30 degree half angle cone – Jettison Policy 

Retrograde clock 

angle (degrees) 

0 0:360 Uniform 

Gravity 

Gravity Model 8 × 8 40 × 40, 

65 × 65, 

or 360 × 360 

Truncated GEM-T1 

Only single version used per MC

Atmosphere 

MET Model 250 ±10 percent Uniform Solar Flux 10.7 cm setting; Nominal MC 

value set equal to the maximum, therefore, 

resulting densities are higher than the 

maximum expected for this analysis 
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During the course of this study, the ISS Program removed the retrograde jettison from the EVA 

PM contingency options, so MC analysis was performed on only a subset of the dispersions. 

Selected MC results are shown in Figures 6.2-7 and 6.2-8. For these cases, the average ISS BN 

was 108.7 kg/m2

. As mentioned, to ensure continuous positive separation for posigrade jettison, 

the PM BN value and difference compared to the ISS BN is important. The plot in the left of 

Figure 6.2-7 shows the ISS/PM range versus time for the 8001 simulated trajectories. Of those 

cases, 6780 show continuous positive separation for 10 days following jettison. Of the 

remaining 1221 posigrade trajectories, all but 136, or total of 1085 of the trajectories, showed 

recontact (i.e., within 500 m of the ISS) in the following 10 days. All of the recontact cases had 

PM BN less than 108.7 kg/m2

. The BN of the posigrade trajectories were plotted as a function of 

pushoff velocity and days to recontact, as shown in the right side of Figure 6.2-7. Note that the 

maximum BN of the returning trajectories was 103.8 kg/m2

, and establishes the lower limit on 

the PM BN necessary to ensure no recontact for a posigrade jettison. 

More retrograde jettison cases showed ISS recontact in 10 days (i.e., almost 1400) compared to 

the 1085 cases in the posigrade jettison MC results. As mentioned, to ensure continuous positive 

separation for retrograde jettisons, the PM BN needs to be lower than the ISS BN. The cases that 

most often predict recontact is when the PM and ISS BNs are similar (i.e., within ~5 kg/m2

), and 

there is a lower pushoff velocity. The retrograde jettison MC results are shown in Figure 6.2-8. 

Figure 6.2-7. Posigrade MC Results 

(Left) Plots of MC trajectories of posigrade jettison PM to ISS range over 10 days. (Right) BN and 

pushoff velocities of the cases that returned to within 500 m of the ISS in the same time period. 
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Figure 6.2-8. Retrograde MC Results 

(Left) Plots of MC trajectories of retrograde jettison PM to ISS range over 10 days. (Right) BN and 

pushoff velocities of the recontact cases in the same time period. 

For this particular jettison object, under the assumptions made for the MC analysis, the results 

indicate that to prevent recontact in 10 days, the PM must have a BN greater than 103.8 kg/m2 

for a posigrade jettison and a BN less than 115.3 kg/m2 for a retrograde jettison. 

6.2.3 Verification 

To verify the analysis performed using the POST2 simulation, STK was used to recreate the 

nominal cases. The cases run in STK used the following assumptions: 

x BN

• ISS – 108.7 kg/m2

• PM minimum – 80.9 kg/m2

• PM average – 112.4 kg/m2

• PM maximum – 155.1 kg/m2

x Pushoff velocity for 0.05 and 0.20 m/s

x Posigrade pushoff attitude

• Pitch = 30 degrees, Yaw = -15 degrees 

x Retrograde pushoff attitude

• Pitch = -30 degrees, Yaw = 160 degrees 

Cases run in STK were sample cases intended to verify the results of POST2, but not to recreate 

the entire POST2 analysis. These cases were run using Astrogator with Runge-Kutta-Fehlberg 

integration. The Earth gravitational parameter was set to 3.986004418e14 m3

/s2and the initial 

state was set using the same vector used in POST2. 

While some initial differences were seen between the STK and POST2, it was determined 

different pushoff locations were used for the retrograde jettison, and different notations were 
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used for geomagnetic index. After the retrograde pushoff location was changed and the 

geomagnetic index notations were reconciled, the results agreed. Therefore the cases run using 

STK verify the results of the POST2 analysis. Figures 6.2-9 and 6.2-10 show the POST and 

STK results for the posigrade jettison with a 0.05 and 0.20 m/s pushoff velocities, respectively 

for the three PM BNs. Figures 6.2-11 and 6.2-12 show the simulation results for the retrograde 

jettison with a 0.05- and 0.2-m/s pushoff velocities, respectively. 

Figure 6.2-9. Comparison of STK and POST2 - Posigrade 0.05 m/s Jettison 
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Figure 6.2-10. Comparison of STK and POST2 - Posigrade 0.2 m/s Jettison 

Figure 6.2-11. Comparison of STK and POST2 - Retrograde 0.05 m/s Jettison 
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Figure 6.2-12. Comparison of STK and POST2 - Retrograde 0.2 m/s Jettison 

6.2.4 Animation 

EVE was used to assist in the visualization of the PM jettison analysis results generated using 

POST2. EVE enables a user to gain better understanding of the system by exploring data in time 

and space within the context of the mission, rather than only in plots and charts. EVE has an 

established history of supporting NASA missions, programs, and projects, including the ISS 

within the VIPER team’s engineering efforts and the mission operations team activities. In 

addition, many NASA missions supported by the EVE team have included data generated from 

POST2. The EVE and POST2 communities have been working to better facilitate data exchange 

between these two systems. Therefore, EVE was ideally situated to assist in the visualization of 

the PM jettison analysis. 

The development of a mission within EVE requires the engineering data and the graphical 

models for incorporation into the scene. As a base, EVE provides the context of the solar 

system, including planetary and moon graphical models and SPICE-based trajectory data. 

Spacecraft are added to the scene using the orbital body reference frames as a basis. For the ISS 

graphical model, a representative configuration was used based on historical Revision Q ISS 

assembly complete models. The ISS was placed in a baseline orbit around Earth using a 

Kepler® propagation model (see Figure 6.2-13). The ISS was put in a nominal 0,0,0 attitude in 

an LVLH flight mode. The PM was added to the ISS as a child element, using a scaled sphere to 

model the PM size. All POST2 time-based PM position data was provided relative to the ISS 

DRF, which was output at 5-second intervals. 
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Figure 6.2-13. ISS Representation in EVE 

Two different animations utilizing the same data set, but different perspectives, were created to 

help visualize the PM motion. Each animation showed the ISS, the PM motion, a line between 

the ISS and PM for reference, and a real-time calculation of the ISS-to-PM separation distance. 

This distance was displayed with the simulation time. The first animation displayed the PM 

relative to the ISS DRF, as provided by POST2. However, this perspective provided a nonintuitive display of the motion, showing the PM first moving away from the ISS, then returning 

towards the ISS in spiraling motion (see the top of Figure 6.2-14). The second animation 

displayed the same data in the Earth-centered inertial frame, which provided a more intuitive 

view of the PM orbit, and highlights the difference in orbit eccentricity between the PM and the 

ISS, as shown in the bottom of Figure 6.2-14. 

Figure 6.2-14. EVE Animations of the PM Motion Relative to ISS 

(Top) ISS DRF; (Bottom) Earth-Centered Inertial Frame. 
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7.0 Findings, Observations, and NESC Recommendations 

Several findings, observations, and NESC recommendations emerged as a result of the PM 

jettison option study. The determination to do a retrograde or posigrade jettison was not as 

straightforward as initially thought. The analysis showed that in addition to separation velocity, 

attitude, and the atmosphere conditions, the key to determining the time to recontact the ISS was 

highly dependent on the ISS and jettisoned object BNs. 

7.1 Findings 

F-1. A BN mismatch is needed between the PM and ISS to provide the best separation 

characteristics over subsequent orbits. 

x For posigrade PM jettisons, the best separation characteristics are obtained when the 

PM has a BN higher than the ISS. 

x For retrograde PM jettisons, the best separation characteristics are obtained when the 

PM has a BN lower than the ISS. 

F-2. The minimum BN mismatch is determined by the requirements on minimum time to 

recontact. 

F-3. Considerations for achieving a desired BN mismatch: 

x To increase the BN mismatch for posigrade jettison where the ISS BN is lower than 

jettison object, efforts to increase the drag area of the ISS for subsequent orbits is 

preferred. 

x To increase the BN mismatch for retrograde jettison, the ISS drag should be 

minimized on subsequent orbits, where the number of orbits and duration of drag 

mitigations efforts can be determined by analysis and operational considerations on a 

case-by-case basis. 

x Adding a drag device to the jettison object (e.g., an inflatable) can increase the BN 

mismatch. 

x Adding or removing mass from a jettison object (i.e., draining fluids, attaching extra 

mass, etc.) can increase BN mismatch. 

F-4. The preferred jettison direction is retrograde because it results in continuous altitude 

degradation of the jettison object and may reduce the long-term likelihood of an ISS 

reboost to avoid collision. 

F-5. Higher jettison velocity increases time to recontact for posigrade and retrograde jettisons. 

F-6. The "stress" case atmosphere resulting in the shortest recontact times is different for 

posigrade and retrograde jettison options. For the case where the BN of the PM is higher 

than the BN of the ISS: 

x The maximum atmosphere (e.g., highest density) results in the shortest recontact 

times for retrograde jettison. 
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x The minimum atmosphere (e.g., lowest density) produces shortest recontact times 

for posigrade jettison. 

7.2 Observations 

O-1. Having the NESC version of the POST2 simulation, developed to support another NESC 

assessment, made it possible to complete the PM jettison analysis in a timely manner 

(i.e., initial analysis in 3 days). 

O-2. The EVE animation capability was helpful in understanding and visualizing the 

simulation results. 

O-3. Low jettison tip-off rates are preferred to allow the object to achieve a trim condition 

sooner thereby reducing it BN dispersions. 

7.3 NESC Recommendations 

The following NESC recommendations were identified and directed towards the ISS Program: 

R-1. Perform unique jettison analyses based in case specific assumptions. (F-1 through F-6)

R-2. Optimize the difference between ISS to jettison object BNs (e.g., change ISS drag, or 

change drag and/or mass of jettisoned object) to maximize recontact interval. 

(F-1, F-2, F-3)

R-3. Ensure jettison objects have a BN higher than ISS for posigrade jettison, or jettison 

objects have a BN lower than ISS for retrograde jettison. (F-1)

R-4. Utilize retrograde jettison when possible as it results in continuous altitude degradation of 

the jettison object and may reduce the long-term likelihood of ISS reboost to avoid 

recontact. (F-4)

R-5. Employ high jettison velocities and low tip-off rates. (F-5, O-3)

R-6. Consider developing attachable drag devices to jettison objects to guarantee positive ISS 

separation and object deorbit. (F-3) 

R-7. Consider development methods and procedures to add or remove jettison object mass to 

optimize ISS to jettison object BN mismatch. (F-3)

8.0 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 relevant factual conclusion and/or issue that is within the assessment 

scope and that the team has rigorously based on data from their 

independent analyses, tests, inspections, and/or reviews of technical 

documentation. 
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #: 

NESC-RP13-00921 

Version: 

1.0 

Title:

ISS ETCS Loop A PM Jettison Options 

Page #: 

30 of 31

NESC Request No.: TI-13-00921 (ISS Pump Module Jettison) 

Lessons Learned Knowledge, understanding, or conclusive insight gained by experience 

that may benefit other current or future NASA programs and projects. 

The experience may be positive, as in a successful test or mission, or 

negative, as in a mishap or failure. 

Observation A noteworthy fact, issue, and/or risk, which may not be directly within the 

assessment scope, but could generate a separate issue or concern if not 

addressed. Alternatively, an observation can be a positive 

acknowledgement of a Center/Program/Project/Organization’s operational 

structure, tools, and/or support provided. 

Posigrade In the same direction as the velocity vector of the ISS. 

Problem The subject of the independent technical assessment. 

Proximate Cause The event(s) that occurred, including any condition(s) that existed 

immediately before the undesired outcome, directly resulted in its 

occurrence and, if eliminated or modified, would have prevented the 

undesired outcome. 

Recommendation A proposed measurable stakeholder action directly supported by specific 

Finding(s) and/or Observation(s) that will correct or mitigate an identified 

issue or risk. 

Retrograde In the opposite direction of the velocity vector of the ISS. 

Root Cause One of multiple factors (events, conditions, or organizational factors) that 

contributed to or created the proximate cause and subsequent undesired 

outcome and, if eliminated or modified, would have prevented the 

undesired outcome. Typically, multiple root causes contribute to an 

undesired outcome. 

Supporting Narrative A paragraph, or section, in an NESC final report that provides the detailed 

explanation of a succinctly worded finding or observation. For example, 

the logical deduction that led to a finding or observation; descriptions of 

assumptions, exceptions, clarifications, and boundary conditions. Avoid 

squeezing all of this information into a finding or observation 

9.0 Acronyms List 

BN Ballistic Number 

DRF design reference frame 

ETCS External Thermal Control System 

EV Extravehicular

EVE Exploration Visualization Environment 

FSE Flight Support Equipment 

GEM Goddard Earth Model 
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #: 

NESC-RP13-00921 

Version: 

1.0 

Title:

ISS ETCS Loop A PM Jettison Options 

Page #: 

31 of 31

NESC Request No.: TI-13-00921 (ISS Pump Module Jettison) 

GN&C Guidance, Navigation, and Control 

ISS International Space Station 

JPL Jet Propulsion Laboratory 

JSC Johnson Space Flight Center 

LaRC Langley Research Center 

LVLH Local Vertical, Local Horizontal 

MC Monte Carlo 

MET Marshall Engineering Thermal 

MTSO Management Technical Support Office 

NESC NASA Engineering and Safety Center 

NRB NESC Review Board 

PM Pump Module 

POST2 Program to Optimize Simulated Trajectories 

SARJ Solar Array Rotary Joint 

STK Systems Tool Kit 

TOPO Trajectory Operations Officer 

V&V Validation and Verification 

VIPER Vehicle Integrated Performance Environments and Resources 

10.0 References 

1. Crues, E. Z.: “Distributed Space Exploration Simulation.” SISO Spring SIW 2006. Space 

Environment and Dynamics Comparison Simulation and Graphics Branch, 2101 NASA 

Parkway, Houston, Texas, 77058, Revision 0.5, May 26, 2006. STI ID 20080031615. 

2. Vetter, K.: “Trick Simulation Environment: User Training Materials.” National 

Aeronautics and Space Administration, Johnson Space Center, Automation, Robotics & 

Simulation Division, Simulation and Graphics Branch, 2101 NASA Parkway, Houston, 

Texas, 77058, Trick 2005.0 release edition, April 2005. 

3. Sauceda, F.: “International Space Station Program Space Station Reference Coordinate 

Systems.” Revision F, 26 October 2001. 

4. https://iss-www.jsc.nasa.gov/nwo/avionics/ai/gnc_ppl/web/PredictedAttitude.shtml

5. http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaSSOP/orbit/ISS/SV

POST.html

6. https://viperweb.jsc.nasa.gov/team_viper/web/

7. Pascucci, J.: “Pump Module Jettison Options,” presentation, December 15, 2013. 

8. Email communication, December 15, 2013. 

9. Email communication, December 15, 2013. 

10. Lumpkin, F.: “Special Study: High Fidelity ISS Drag Computations.” Peer Review 

Presentation, February 16, 2005. 

11. Jacchia 1970: Computational Procedure used in the Development of the MSFC Modified 

Jacchia Model Atmosphere, 1967/ 19700031574. 
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE

Technical Memorandum

4. TITLE AND SUBTITLE

International Space Station (ISS) External Thermal Control System (ETCS) 

Loop A Pump Module (PM) Jettison Options Assessment

5a. CONTRACT NUMBER

6. AUTHOR(S)

Murri, Daniel G.; Cianciola, Alicia Dwyer; Shidner, Jeremy D.; 

Powell, Richard W.

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

NASA Langley Research Center

Hampton, VA 23681-2199

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

8. PERFORMING ORGANIZATION

REPORT NUMBER

L-20488 NESC-RP-13-00921

10. SPONSOR/MONITOR'S ACRONYM(S)

NASA

13. SUPPLEMENTARY NOTES

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category 37 Mechanical Engineering

Availability: NASA CASI (443) 757-5802

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email: help@sti.nasa.gov)

14. ABSTRACT

On December 11, 2013, the International Space Station (ISS) experienced a failure of the External Thermal Control System 

(ETCS) Loop A Pump Module (PM). To minimize the number of extravehicular activities (EVA) required to replace the PM, 

jettisoning the faulty pump was evaluated. The NASA Engineering and Safety Center (NESC) received a request to support 

the International Space Station (ISS) Pump Module (PM) Jettison Assessment on December 16, 2013. The objective of this 

study was to independently evaluate the jettison options considered by the ISS Trajectory Operations Officer (TOPO) and to 

provide recommendations for safe jettison of the ETCS Loop A PM. This document contains the outcome of the NESC 

assessment.

15. SUBJECT TERMS

International Space Station; Pump Module; Jettison; Analysis; NASA Engineering and Safety Center

18. NUMBER

OF

PAGES

36

19b. TELEPHONE NUMBER (Include area code)

(443) 757-5802

a. REPORT

U

c. THIS PAGE

U

b. ABSTRACT

U

17. LIMITATION OF

ABSTRACT

UU

Prescribed by ANSI Std. Z39.18

Standard Form 298 (Rev. 8-98)

3. DATES COVERED (From - To)

December 2013 - September 2014

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

869021.03.07.01.16

11. SPONSOR/MONITOR'S REPORT

NUMBER(S)

NASA/TM-2014-218542

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