Damon Delap

Glenn Research Center, Cleveland, Ohio

Joel Glidden and Christopher Lamoreaux

Lockheed Martin Space Systems Company, Littleton, Colorado

Development of the Orion Crew-Service Module

Umbilical Retention and Release Mechanism

NASA/TM—2013-216583

September 2013
	
	
	








	



	

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Damon Delap

Glenn Research Center, Cleveland, Ohio

Joel Glidden and Christopher Lamoreaux

Lockheed Martin Space Systems Company, Littleton, Colorado

Development of the Orion Crew-Service Module

Umbilical Retention and Release Mechanism

NASA/TM—2013-216583

September 2013


	



	


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NASA/TM—2013-216583 1 

Development of the Orion Crew-Service Module 

Umbilical Retention and Release Mechanism 

Damon Delap 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Joel Glidden and Christopher Lamoreaux 

Lockheed Martin Space Systems Company 

Littleton, Colorado 80127 

Abstract 

The Orion Crew-Service Module umbilical retention and 

release mechanism supports, protects and disconnects all of the 

cross-module commodities between the spacecraft’s crew and 

service modules. These commodities include explosive transfer 

lines, wiring for power and data, and flexible hoses for ground 

purge and life support systems. Initial development testing of 

the mechanism’s separation interface resulted in binding 

failures due to connector misalignments. The separation 

interface was redesigned with a robust linear guide system, and 

the connector separation and boom deployment were separated 

into two discretely sequenced events. Subsequent analysis and 

testing verified that the design changes corrected the binding. 

This umbilical separation design will be used on Exploration 

Flight Test 1 (EFT-1) as well as all future Orion flights. The 

design is highly modular and can easily be adapted to other 

vehicles/modules and alternate commodity sets. 

1.0 Introduction 

Figure 1 shows the three main modules of the Orion MultiPurpose Crew Vehicle (MPCV). The subject of this paper is 

the umbilical connection between the Crew Module (CM) and 

the Service Module (SM). 

The Crew-Service Module (CM/SM) umbilical retention 

and release mechanism supports and protects all of the cross 

module commodities between the spacecraft’s crew and 

service modules. These commodities include explosive 

transfer lines (ETL), wiring for power and data, and flexible 

hoses for ground purge and life support systems. Its main 

functional duty is to safely disconnect the commodity lines 

and move the hardware out of the way as the CM departs. 

Some of the main driving requirements of the umbilical 

separation mechanism are: 

Separate the commodity connections within a defined 

amount of time to ensure compliance with abort and 

nominal vehicle separation timelines. 

Fully separate the SM side of the umbilical within a 

defined amount of time under nominal conditions. 

Initiate the separation only upon receipt of the 

separation command from the CM. 

Prevent recontact of the SM umbilical hardware and the 

CM for all separation scenarios. 

Meet functional and performance requirements after 

being exposed to acceptance and qualification testing 

environments. 

Figure 2 shows the main components that make up the 

umbilical separation mechanism. The CM bracket assembly 

and the line support assembly are mounted to the CM. These 

components stay with the CM after the umbilical separates. 

The rest of the components are mounted on the SM and travel 

with the SM after umbilical separation. 

Figure 3 shows the parts of the two stage plate separation 

scheme of the umbilical mechanism. The SM plate is shown 

partially tranparent in order to see the details of the parts 

within it. 

1.1 Two Stage Umbilical Concept of 

Operations 

When the CM/SM separation command is received, the 

center separation bolt fires and releases the first stage of 

separation (Stage 1). This allows the separation springs in the 

corners of the SM plate to push the plates apart, which 

separates all of the connections that go across the interface. 

The SM plate assembly rides on the guide pin/linear bearing 

setup and is stopped by a hard stop located on top of the guide 

pins. A short time after the center bolt fires, the two outside 

bolts are fired (Stage 2). This releases the umbilical boom 

assembly and terminates the structural connection of the 

umbilical to the CM. The boom is then pushed away by the 

actuator assemblies and locked out in a position that will not 

interfere with the departing CM (Figure 4). 
NASA/TM—2013-216583 2 

Figure 1.—Orion crew vehicle 

Figure 2.—Umbilical separation mechanism 

Figure 3.—Two stage plate separation components 

Figure 4.—Stage 2 deployment 

Figure 5.—Apollo umbilical 

Figure 6.—Apollo umbilical guillotine cross section 

2.0 Apollo Umbilical 

The Apollo umbilical (Figure 5) separation was performed 

by a pyrotechnically-activated guillotine that had three 

pyrotechnic charges and four cutting blades (Figure 6). 

All the commodities were packaged into two rectangular 

blocks that were cut by the redundant blades. These blocks 

consisted of wires, tubes and four thin metal straps potted in 

epoxy. Figure 7 shows the severed commodity blocks on the 

Command/Service Module (CSM) 117 capsule that was used 

on the Skylab 3 mission. 
NASA/TM—2013-216583 3 

Figure 7.—Severed commodity bundles (CSM 117) 

The wires, tubes, metal straps and epoxy were the only 

structural attachment to the CM. Once they were cut, the 

umbilical arm was free to swing away. 

3.0 Guillotine/Connector Trade Study 

Very early on in the design of the umbilical mechanism, a 

trade study was completed between the guillotine method used 

by Apollo and the concept of using separation connectors. 

Lockheed Martin (LM) chose the concept utilizing separation 

connectors for the following main reasons: 

1. It increased the flexibility and decreased the cost at the 

component level. The guillotine is a one use item and 

different tubing for each test run would be needed. The 

connectors would allow the mechanism to be refurbished/reset more quickly and cheaply. The connectors 

could also be designed for several separations. 

2. It was estimated to have less mass by about 40 to 

50 percent. 

3. The connectors were considered to have a higher technology readiness level (TRL) and need less development. A guillotine system to cut multiple fluid and 

electrical lines would be a custom design that would 

need a large development program. 

4. Connectors simplified the assembly and integration 

process. They are safer to handle and easier to install. 

4.0 Baseline Plate Separation Design 

Development testing of LM’s baseline plate separation 

design resulted in binding due to connector misalignments. As 

a result, the plate separation was redesigned into the two stage 

scheme described in the Introduction. This section outlines the 

details of the baseline design and describes its key features. 

Figure 8.—Baseline design exploded view 

Figure 9.—Baseline design cross section 

The function of the baseline plate separation scheme was to 

provide a guided linear separation of the fluid and electrical 

connectors during the first moments of the umbilical separation in order to inhibit connector binding. The basic assumption for preventing binding was that the connector plates and 

linear guide components needed to provide angular and lateral 

control of the connector separation within the advertised 

misalignment capabilities of the fluid and electrical connectors. Figure 8 and Figure 9 show the baseline plate separation 

design and identify the key components. 

The connector halves were mounted to the CM and SM 

plates. The motion of these plates disconnected the commodity 

connections. 

The spring pack in the middle of the connector plates provided the force to separate the plates and overcome any 

hindering forces that may be a result of binding, misalignment 

or damage in the linear guide system or connectors. The 

springs were packaged this way to reduce mass and make the 

overall plate design more compact. 

The guide pins (x2) on SM plate and bushings (x2) on CM 

plate provided the guidance for the linear separation within the 

stated misalignment limits of the fluid and electrical connectors. 
NASA/TM—2013-216583 4 

Figure 10.—Zero separation force (ZSF) connector 

The separation bolts (x2) were designed to fire simultaneously. This single event released the plates as well as the 

umbilical’s structural connection to the CM. 

4.1 Fluid and Electrical Connectors 

The fluid connectors in the umbilical mechanism are a 

proprietary LM design. They utilize a dual o-ring seal with 

tight tolerances in order to meet stringent leakage requirements. In the baseline design, the mounting allowed the fluid 

connectors to float laterally and angularly to accommodate 

misalignments. 

The electrical connectors are a zero separation force (ZSF) 

design similar to the one shown in Figure 10. 

These connectors provide a “zero force separation” by using 

the wave springs on the plug side to disengage the pins from 

the sockets. Ideally, an external force is not needed for the 

connector to separate. 

5.0 Baseline Plate Separation Development Testing 

During development testing, the plates were fully populated 

with the fluid and electrical connectors and slowly separated 

using a tensile testing frame. The test frame measured the 

force needed to separate the plates. The displacement of each 

corner of the SM plate was also measured so that the relative 

plate angle could be calculated. 

The first instance of binding occurred with the plates at less 

than one degree relative angle. The plates had separated 

enough to expose the o-rings from the fluid connectors, 

indicating that they were not the source of the binding. The 

plates were decoupled from the test fixture, but the electrical 

connectors remained mated. A gentle force was applied to the 

low edge of the SM plate, which caused the connectors to selfseparate. Once the connectors were dis-assembled from the 

plates, it was found that the connectors would not self-separate 

with their own weight and a slight moment (produced by the 

wire bundle hanging off to the side). 

LM tested a second configuration in which the plates were 

populated with only the fluid connectors. In this configuration, 

the plates bound up at about 2° relative angle. Loosening the 

bolts on one of the fluid connectors relieved the binding. 

A third configuration was tested which was the same as the 

second one, but with one modification: the fluid connectors 

were given freedom to float. The design of the fluid connectors had features that allowed them to float laterally and 

angularly after being mounted. However, in hindsight LM 

realized that the mounting scheme of the test setup had 

counteracted these features and the connectors were not 

allowed to float as intended during testing of the second 

configuration. With this change, the plates separated successfully and consistently four times. 

After review of the data and results, LM determined that the 

root causes of the baseline design failure were: 

1. The electrical and fluid connectors did not have the 

misalignment capabilities that were expected. 

2. The mechanism displayed an instability, or tendency to 

misalign, which was not anticipated. 

LM concluded that the basic premise of the separation 

method had to change and the team decided to pursue alternate 

solutions. 

6.0 Two Stage Separation Design and 

Analysis 

6.1 Design Description 

After evaluating many potential solutions, LM selected the

two stage separation design described in the Introduction (see 

Figure 3). 

Stage 1 is the closely constrained linear separation of the 

plates and connectors. Stage 2 is the release of the structural 

connection to the CM and the rotational motion of the entire 

umbilical arm. Splitting the umbilical release into two stages 

allows much more control over the separation event and 

reduces the binding potential of the mechanism. One of the 

biggest advantages of this solution is that it preserved the 

majority of the baseline parts. Most of them, because of 

schedule constraints, had already been released and were in 

fabrication at the time of the development testing. The key 

design features/changes are described in the following 

subsections. 

6.1.1 Separation Springs Moved to Corners 

The separation springs were moved from the center of the 

SM plate to the corners. The force balancing of the baseline 

configuration with a bound connector is shown in Figure 11. 
NASA/TM—2013-216583 5 

The spring forces are represented by the dots in the center of 

the plate and the bound connector by the dot in the lower 

right-hand corner. 

When one of the connectors binds, it becomes the pivot 

point of the separation, and the force required to separate 

increases with the relative plate angle. In other words, the 

separation force acting on the bound connector goes to zero 

until something else in the system becomes the new pivot 

point. Connector binding in this scenario is likely unrecoverable, as was witnessed in the development testing of the 

baseline design. 

With the spring moved to the corners (Figure 12), the separation force on the bound connector cannot go to zero. 

Although it is recognized that the spring closest to the bound 

connector has a moment disadvantage relative to the other 

three springs, the closest spring to it will apply and increasing 

separation force as the plate angle increases. 

6.1.2 Additional Separation Bolt 

In order to perform two discrete separation stages, one more 

separation bolt was added to the design. Figure 13 shows the 

mechanism prior to Stage 1 initiation. 

The first stage is released by firing the center bolt. This 

severs the connection holding the two plates together and 

allows the SM plate to slide along the guide pins. Figure 14 

shows the position of the plates at the end of Stage 1, just prior 

to Stage 2 initiation. 

The second stage is started by firing the two outside bolts 

after the linear motion is completed. This releases the structural connection between the umbilical boom and the CM and the 

umbilical arm is free to rotate away. 

6.1.3 Larger Guide Pins and Linear Bearings 

The diameter and length of the guide pins and linear bearings were increased. They are also more closely toleranced, 

resulting in a tighter control of plate orientation and more 

precise plate and connector location. The guide rods do not 

cross the separation plane as they did in the baseline design 

and the SM plate rides along the guide rods for the entire 

Stage 1 stroke. 

6.1.4 Redesigned Electrical Connectors 

Due to the tendency of the original off-the-shelf electrical 

connectors to easily bind up, it was apparent that modifications to the design were necessary. LM worked with the 

vendor to identify changes that would decrease the tendency 

for the connectors to bind up. The vendor made some preliminary modifications to the baseline connectors and performed 

tests to verify that the performance of the connectors improved. LM then developed a specification that they used to 

procure the flight connectors. 

Figure 11.—Force balance of baseline configuration 

Figure 12.—Force balance with springs in corners 

Figure 13.—Connector plates before Stage 1 initiation 

Figure 14.—Connector plates at the end of Stage 1 
NASA/TM—2013-216583 6 

6.1.5 Redesigned Fluid Connector Mounting 

Binding occurred in the fluid connectors at much less of 

angle than anticipated. However, the new plate separation 

scheme with a tighter control on plate position and relative 

angularity minimized the needed changes to these connectors. 

The connectors were changed to a flange mounted scheme that 

eliminated the angular float and reduced the lateral float. A 

small amount of lateral float was preserved to help the 

connector halves self-align while mating. 

6.2 Analysis Description

An analysis was performed to explore the susceptibility of 

the two stage linear guide system to binding. This analysis 

evaluated the geometry of the linear guide system relative to 

the assisting and hindering forces of the springs and connectors. Specifically, Equation (1) and (2) (Ref. 1) were used 

to assess the binding condition: 





2

1

s

L (binding condition) (1) 





2

1

s

L (no binding condition) (2) 

where L is the driving moment arm of the load, s is the vertical 

spacing between the two bushings within the linear bearing 

and μ is the coefficient of friction between the bearings and 

the guide pin (see Figure 15). 

The value of s was determined by the geometry of the design, the value of μ was assumed based on materials and 

expected surface finishes and a critical L (Lcrit) was computed. 

For the purposes of evaluating this design, Lcrit corresponded 

to maximum equivalent moment arm of the combined assisting and hindering forces which would result in a no-binding 

condition. Once Lcrit was calculated, it was compared to the 

equivalent moment arm calculated by summing all the forces 

and moments in the umbilical plate separation (Figure 16) to 

determine if binding is expected to occur. 

LM used the binding analysis as the basis for a Monte Carlo 

simulation to analytically tune the design and assess its 

susceptibility to binding under varying conditions and assumptions. The simulation allowed for rapid assessment of numerous trades and contingency scenarios. The variables included 

spring out scenarios as well as variations in spring force, 

electrical connector self-separating force, hindering force from 

the fluid connectors and the forces expected from bending the 

fluid lines and electrical harnesses. The four separation springs 

and the electrical connector springs were simulated individually. A ±10 percent spring force tolerance was used. Each seal 

port was also simulated individually, but because of more 

Figure 15.—Binding equation variables 

Figure 16.—Resulting moment arm of the forces 

present during plate separation 

uncertainty in the hindering forces, a ±84 percent tolerance 

was used on the force. The variance in the forces required to 

bend the fluid lines and electrical harnesses were reflected in 

the analysis as a change in the center of gravity (CG) of the 

SM plate assembly. 

Four different configurations were simulated: 

1. Four in-tolerance separation springs. 

2. Three in-tolerance separation springs and one with one 

coil out. 

3. Zero electrical connector forces. 

4. Double electrical connector forces. 

Ten thousand iterations per configuration were run for 

assessing binding. Because binding and spring strength affect 

the mechanism’s ability to separate within its prescribed time 

limit, LM also ran 255 iterations per configuration to evaluate 

the plate separation time duration. 
NASA/TM—2013-216583 7 

6.3 Analysis Results 

Figure 17 shows an example of the results that were obtained from the Monte Carlo analysis for binding. This 

particular plot shows the resultant moment arm location for 

Configuration 1. The dashed circle represents the region that 

corresponds to a no-binding condition (i.e., the resultant 

equivalent moment arm is less than Lcrit). In this configuration, 

zero binding cases were found. Similar plots were generated 

for the other configurations and all cases were found to be 

well within the no-binding region. The data indicates that the 

design is most sensitive to variances in the CG location. 

Figure 18 shows an example of the results from the timing 

evaluation and represents the data from Configuration 1. It 

indicates that the plates separate well within the required time. 

In this case it performs the full travel, on average, in about 

half the required time. Plots for all the configurations showed 

similar results and LM found that the plate separation happens 

well within the required time frame. 

Further simulations were run to find the binding envelope of 

the design. The system was found to have positive margin on 

binding as well as timing with up to six coils out on one 

spring. Overall, the analysis demonstrated that the linear guide 

system is robust and LM was confident that the binding issues 

that were seen in the baseline design had been resolved. 

7.0 Two Stage Separation Design 

Development Testing 

The analytical validation was followed by a repeat of the 

initial testing suite, plus test cases at thermal extremes and test 

cases with spring out scenarios (to demonstrate fault tolerance). 

The mechanism was then exposed to the qualification vibration 

environment. Finally, functional testing of the full umbilical 

deployment was performed at full speed with live ordnance. 

7.1 Stage 1 Testing 

The primary objective of this test was to determine the force 

supplied by the springs during Stage 1 and to verify that no 

binding occurs. The matrix for this test is displayed in Table 1. 

Three test runs were completed for each condition. The spring 

out condition was assessed in Test 9 (i.e., only three active 

springs). 

The unit functioned as expected and the results were very 

repeatable from run to run. Temperature had little to no 

discernable effect on the separation and pressure in the fluid 

lines assisted the separation. All the test runs showed healthy 

margins, including the spring out case. The test data is shown 

in Figure 19. The figure also indicates the points in the data 

where key events occurred. 

Figure 17.—Binding analysis results for Configuration 1 

Figure 18.—Separation timing results for Configuration 1 

TABLE 1.—TEST MATRIX FOR STAGE 1 

SEPARATION VERIFICATION 

Test Electrical 

connectors 

Fluid 

connectors 

Pressurized 

fluid lines 

Temperature 

level 

1 No No No Ambient 

2 Yes Yes No Ambient 

3 Yes Yes No Cold 

4 Yes Yes No Ambient 

5 Yes Yes No Hot 

6 Yes Yes Yes Ambient 

7 Yes Yes Yes Cold 

8 Yes Yes Yes Hot 

9* Yes Yes Yes Ambient 
NASA/TM—2013-216583 8 

Figure 19.—Stage 1 separation verification results 

Figure 20.—Vibration test setup

7.2 Vibration Testing 

The primary objective of the vibration test was to subject 

the umbilical development assembly to qualification vibration 

environments in preparation for the functional test. The 

entire development umbilical assembly was used for this test 

(Figure 20). 

Results showed that the desired levels were achieved in all 

three axes with no significant issues. 

7.3 Functional Testing 

This set of testing had two main objectives: 

1. Measure and record the source shock environment associated with the actuation of the three pyrotechnic separation bolts used in the separation event. 

2. Demonstrate that the two stage separation design successfully separated after exposure to qualification vibration levels. 

During this test both Stage 1 and Stage 2 were activated. 

Two test runs were completed, with minor refurbishment 

required in between the test runs. 

The results showed that the measured shock from the umbilical separation bolts did not pose a threat to the umbilical 

hardware and the shock models needed only minor alterations. 

From a mechanisms standpoint, the two stages separated as 

expected. Post-test inspections showed no unexpected damage 

or wear in the condition of the hardware. Based on the results 

from this test, LM decided to move forward with the two stage 

design for the flight umbilical mechanism. 

8.0 Lessons Learned 

The linear guide system needed to be the dominant element 

for controlling the plate orientation and connector positioning. 

Allowing too much play in the guide system and connector 

mounting (in an attempt to allow the connectors to float to 

prevent binding) did not work well. Dividing the umbilical 

separation into two carefully constrained and timed events 

addressed the root cause of the binding failures by providing 

better control of the plate orientation. 

The off-the-shelf electrical connector design did not perform as expected in the umbilical mechanism application. The 

cost and schedule impacts from writing a specification and 

purchasing validated connectors could have been partially 

mitigated by verifying the actual performance of the off-theshelf connector design. 

The separation force from the plate springs is more effective 

when distributed to the corners of the plates. This provided a 

more stable application of the separation force. Furthermore, it 

ensured that there would never be zero separation force being 

applied to a bound connector. 

The Monte Carlo simulation was very effective in dealing 

with the number of variables affecting the separation and the 

uncertainty associated with each one. It allowed for rapid 

assessment of numerous trades and contingency scenarios. 
NASA/TM—2013-216583 9 

The envelope of the design was quickly and effectively 

identified. It gave LM confidence that this separation configuration met force and timing margins. 

Finally, development testing of the CSM umbilical retention 

and release mechanism proved to be essential in discovering 

unknown and unanticipated issues and helped to validate 

analytical predictions. 

9.0 Conclusions 

The analysis and testing results of the two stage plate separation design indicate that the mechanism will operate well during 

flight acceptance and qualification testing as well as the 

EFT-1 mission. The method of separating a cluster of fluid, 

electrical and pyrotechnic connectors used in the CM/SM 

umbilical mechanism can be used in many applications. The 

analysis methods for assessing the binding potential and 

mechanism timing can be easily changed to accommodate 

different connector configurations and commodity sets. LM will 

continue to develop this umbilical connection for Orion missions beyond EFT-1 and hopes to use it in future applications. 

References 

1. PBC Linear (2009). PBC Linear Motion Catalog. Online 

at http://www.pbclinear.com (as of 10 July 2013), p. 48.