Crew Survival Office

1
Crew Survival Offices Position on the
Acceptability of the Proposed Inline RSRB Launch
Vehicle for Crewed LaunchesJuly 15, 2005

• Leo Langston
• Paul Porter
• Clint Thornton
• JSC Crew Survival

2
Agenda

• Objective
• Lessons Learned?
• Crew Survival Office Position
• Applicable HRR Requirements
• Crew Survivals Response to SRB Reliability and
  Survivability Claims
• Launch Failures by Subsystem Root Cause of
  US-Built Expendable Vehicles 1984-2004
• Demonstrated Reliability In Other Solid Based
  Systems
• Reliability and Crew Safety Assessment for Solid
  Rocket Booster / J-2S Based Launch Vehicle
  (SAICNY05-04-1F) - Specific Issues
• CSO Comments on ESAS Integrated SRB Abort
  Assessment
• Conclusion
• Recommendations
• Backup

3
Objective

• Given the limited time to select launch vehicles
  that will meet the Agencys exploration goals,
  the Crew Survival Office (CSO) is concerned that
  cost and schedule and perhaps other
  outside/political pressures may be forcing the
  agency to make a decision to use a launch vehicle
  configuration that will not meet current human
  rating requirements.
• The Crew Survival Office would like to present a
  set of arguments questioning the basis for
  selection of the current proposed crewed launch
  vehicle (13.1) that can be used to allow agency
  management to pause and reconsider the current
  selection before making a commitment to a
  possibly inappropriate design solution.

4
Lessons Learned ?
Words of wisdom from past accident investigations
and other NASA advisory groups should be
providing some important lessons learned to help
guide our selection of the next human launch
vehicle.

• We need to make sure that the next generation
  vehicle is not based on probability but on
  assurability. We need to use the best
  technology we can to assure that the crew
  survives. If we cannot do it in the Shuttle then
  we need to have it in next vehicle. If we do not
  do this now and do some soul searching we
  will be in the same place 20-30 years from now.
• Bernard Harris, Aerospace Safety Advisory Panel,
  March 26, 2003
• Future crewed-vehicle requirements should
  incorporate the knowledge gained from the
  Challenger and Columbia accidents in the
  assessing the feasibility of vehicles that could
  ensure crew survival even if the vehicle is
  destroyed.
• Columbia Accident Investigation Board Report Vol
  I, August 2003

5
Crew Survival Office Position

• It is the position of the Crew Survival Office
  that the use of SRBs (large or small) in any
  crewed launch vehicle present booster
  catastrophic failure modes that make compliance
  with the HRR 8705.2 very unlikely due to the
  inability to successfully abort if those failures
  occur.
• Inability to abort occurs primarily due to the
  lack of sufficient warning time to detect the
  imminent booster catastrophic failure, initiate
  the abort and achieve a safe separation distance
  prior to LV catastrophic breakup or explosion
• The current ATK/SAIC reliability estimates for
  the RSRB in line crew launch vehicle are
  over-optimistic compared to historical evidence
  from solid propellant launch vehicles

6
Applicable HRR Requirements

• The following are excerpts of the applicable
  requirements from the latest NPR 8705.2
• 3.1.7 Space systems shall not use abort as the
  first leg of failure tolerance
• 3.9.3 The space system shall provide crew and
  passenger survival modes throughout the ascent
  and on-orbit profile (from hatch closure until
  atmosphere entry interface) in the following
  order of precedence
• a. Abort. 
• b. Escape by retaining the crew and passengers
  encapsulated in a portion of the vehicle that can
  reenter without crew or passenger fatality or
  permanent disability.
• c. Escape by removing the crew and passengers
  from the vehicle. 
• Note The requirement is for survival modes to
  cover 100 percent of the ascent trajectory. The
  preferred method is for abort to cover 100
  percent of the trajectory, thus returning the
  crew to the Earth in the spacecraft. Some
  architecture options that do not lend themselves
  to the 100 percent abort coverage will need to
  use the other methods to meet the intent of this
  requirement.
• 3.9.4 The program shall ensure that ascent
  survival modes can be successfully accomplished
  during any ascent failure mode including, but not
  limited to, complete loss of thrust, complete
  loss of control, and catastrophic booster failure
  at any point during ascent
• Tailoring of HRR requirements is allowed with the
  following caveat
• Note Tailoring is for requirements that are not
  applicable (e.g., ascent escape requirements do
  not apply to a surface rover). Tailoring is not
  for requirements that are considered
  programmatically undesirable, expensive, or
  technically complicated.
• Underlining provided for emphasis only

7
Crew Survivals Response to SRB Reliability and
Survivability Claims

• Reality does not seem to correspond to the
  predicted paper reliability of SRBs as
  presented by ATK/SAIC

It appears that there are enormous differences
of opinion as to the probability of a failure
with loss of vehicle and of human life. The
estimates range from roughly 1 in 100 to 1 in
100,000. The higher figures come from the working
engineers, and the very low figures from
management. What are the causes and consequences
of this lack of agreement? Since 1 part in
100,000 would imply that one could put a Shuttle
up each day for 300 years expecting to lose only
one, we could properly ask "What is the cause of
management's fantastic faith in the machinery?"
R. P. Feynmann, Personal observations on the
reliability of the Shuttle, Report of the
Presidential Commission on the Space Shuttle
Challenger Accident, Appendix F
8
Crew Survivals Response to SRB Reliability and
Survivability Claims

• In 44 years of human space flight no flight crew
  has been lost during ascent as the result of a
  totally liquid based launch vehicle
• Anticipated failures and robust ascent abort
  system
• Two loss of vehicle events in the manned Soyuz
  program ended in successful launch aborts
• Soyuz 18-1 2nd/3rd staging separation failure
• Soyuz T 10-1 GSE failure pad fire
• However, in 24 years of flight on SRB based
  systems one flight crew has been lost as the
  result of an SRB failure during ascent
• Unexpected and unanticipated failures, and no
  valid abort system
• STS 51L

For a successful technology, reality must take
precedence over public relations, for nature
cannot be fooled. R. P. Feynmann, Personal
observations on the reliability of the Shuttle,
Report of the Presidential Commission on the
Space Shuttle Challenger Accident, Appendix F
9
Launch Failures by Subsystem Root Cause of
US-Built Expendable Vehicles 1984-2004
In the past 20 years there have been more SRB
failures than Liquid Propulsion failures The four
SRB shell failures were probably not
survivable All of the Liquid Propulsion failures
were probably survivable
Failure Type Number of Failures Percent
Liquid Propulsion (Start) Liquid Propulsion (In-flight) 3 3 12 12
Solid Propulsion (Shell) Solid Propulsion (TVC) 4 3 16 12
Stage Separation Fairing Separation 6 1 24 4
Electrical Avionics Other (lightning strike) 2 2 1 8 8 4
TOTAL 25 100
Failure Details
Source Futron Design Reliability Comparison for
SpaceX Falcon Vehicles November 2004
10
Launch Failures by Subsystem Root Cause of
US-Built Expendable Vehicles 1984-2004

• Four of the six liquid failures in the previous
  table were associated with the upper stage and
  none led to a vehicle explosion
• Of the two 1st stage failures
• Atlas I (AC-74) - Inappropriate power down to 65
  - Propellant pressure regulator misconfiguration
• Titan 34D (34D-7) - Premature engine shutdown
  Propellant feed system failure
• Of the seven SRB failures in the previous table
• Four resulted in vehicle destruction with little
  or no warning
• STS 51L
• Titan 34D-9
• Titan 403A K-11 (45F-9)
• Delta 2 7925-10
• The three TVC failures were caused by loss of
  hydraulic fluid

11
Launch Failures by Subsystem Root Cause of
US-Built Expendable Vehicles 1984-2004
Titan 34D-9 18 April 1986 SRB Case Burst at MET
of 8.5 seconds
12
Demonstrated Reliability In Other Solid Based
Systems

• Since 60s the nations defense has relied on
  solid propulsion ICBM systems
• Minuteman family
• Minuteman I - Launches 380. Failures 27.
  Success Rate 92.9 (1/14 failure rate)
• Minuteman II - Launches 194. Failures 2.
  Success Rate 99.0 (1/100 failure rate)
• Minuteman III - Launches 263. Failures 5.
  Success Rate 98.1 (1/53 failure rate)
• Total - Launches 837. Failures
  34 Success Rate 95.9 (1/24 failure rate)
• Peacekeeper
• Launches 51. Failures 1. Success Rate 98.0
  (1/50 failure rate)
• Polaris family
• Polaris A1 - Launches 122. Failures 33. Success
  Rate 73.0 (1/4 failure rate)
• Polaris A2 - Launches 227. Failures 15. Success
  Rate 93.4 (1/15 failure rate)
• Polaris A3 - Launches 271. Failures 8.
  Success Rate 97.1 (1/34 failure rate)
• Trident C-4 - Launches 165. Failures 7.
  Success Rate 95.8 (1/24 failure rate)
• Trident D-5 - Launches 122. Failures 5.
  Success Rate 95.9 (1/24 failure rate)
• Total - Launches 907. Failures 68.
  Success Rate 92.5 (1/13 failure rate)
• These failure rates demonstrate that very high
  total system reliabilities are quite unlikely

13
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues

• SAIC, p. 7 The simplest designs of the EELVs,
  which offer the greatest potential for inherent
  reliability, are the single core variants. These
  single core EELVs with an effective crew escape
  system should provide the greatest crew safety.
• CSO Crew Survival agrees with this statement.
  Any all liquid launch vehicle with an effective
  crew abort/escape system should provide the
  greatest crew safety. Mercury, Gemini, Soyuz and
  Apollo programs demonstrate this.
• SAIC, p. 8 Simple Inherently Safe Design A
  single human-rated SRB first stage matured
  through years of experience with over 176 flights
  of the current design for launching crew
• CSO This statement, while true of the current
  shuttle RSRB, is not necessarily applicable to
  the proposed new 5 segment RSRB or RSRB inline
  configuration. Also, is the shuttle RSRB human
  rated because it truly meets human rating
  requirements or because there were no viable
  alternatives to it for the shuttle system? Is it
  truly human rated or human rated because humans
  ride on it?

14
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues

• SAIC, p. 8 Historically Low Rates of Failure
  In the space shuttle system only the 51-L event
  (a non-catastrophic failure of the SRB) has
  marred a perfect record in 226 SRBs, with 176
  consecutive successful uses of the redesigned
  SRBs. This 1 in 226 history, or 0.996 launch
  success rate is perhaps the best of the best in
  launcher history.
• CSO Non Catastrophic? Did vehicle breakup before
  the SRB could have had a catastrophic event? The
  JSC Greenbook list 17 additional significant gas
  sealing problems, most recently STS-79, making
  the demonstrated failure rate 18/226 or a success
  rate of 92 (Greenbook extract)
• SAIC, p. 8 Non-Catastrophic Failure Mode
  Propensity Solid rocket booster history, and
  specific design features of the SRB suggest a
  propensity for gradual thrust augmentation
  failures which present less of a challenge for
  crew survival in the inline configuration, should
  they occur.
• CSO This historical record from 1985-2004 shows
  this to not be the case only 1 out of 6 SRB
  failures demonstrated thrust augmentation
• CSO suggest a propensity is wishful thinking
  not, a valid engineering conclusion

15
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues

• SAIC, p. 8 Process Control The proposed
  design offers the benefits of using propulsion
  suppliers with mature in-plant process control
  systems to minimize human error, which has proven
  to be a significant contributor to risk.
• CSO Current 4 segment RSRB processes may not be
  applicable to the new proposed 5 segment design.
  RSRB refurbishment, segment pouring, testing,
  hazardous shipping and storage, and KSC stacking
  still require substantial human labor and
  inspection with corresponding potential for
  human error
• SAIC, p. 8 Failure Precursor Identification and
  Correction The design capitalizes on the
  significant failure precursor identification and
  elimination benefit from recovery, and post
  flight inspection of the recovered SRBs.
• CSO Post flight failure examination is of little
  use to the crew on the flight with the problem
• CSO The data may be used incorrectly as in the
  Challenger and Columbia accidents.
• CSO Not all precursors are recognized

16
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues

• SAIC, p. 10 1. The proposed design has a
  significant potential of meeting, and even
  exceeding, the 1 in 1000 mission astronaut office
  risk goal proposed by the crew even when
  conservative accident failure criteria have been
  applied (see Figure 1.1 indicating worst case
  condition), and even with significant further
  conservative variation in key risk driving
  parameters.
• CSO Paper rockets are well known for having
  significant potential in whatever aspect is
  important. In reality, the actual vehicle most
  often never achieves its significant
  potential.
• SAIC, p. 10 SAIC assumed that all worse case
  accidents, that is, case burst events, would not
  be survivable. The SAIC physical models indicate
  that some at least, if not all, of the accidents
  would allow for the possibility of crew escape
  and recovery
• CSO HRR compliance requires more than some at
  least, if not all, of the accidents would allow
  for the possibility of crew escape and recovery.
• CSO The unknowable accident environment renders
  analysis somewhat less than reliable.

17
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues

• SAIC, p. 11 The proposed design offers
  significant, as much as an order of magnitude,
  improvement in crew survival during ascent as
  compared to the current shuttle system.
• CSO Since the shuttle has no ascent crew
  survival capability during a first stage SRB
  failure this statement means something is better
  than nothing.
• SAIC, p. 11 The primary risk-driving elements
  of the design are forecasted to be contained in
  the second stage J-2S based system because it is
  a new development of a system without flight
  experience.
• CSO The lack of flight experience would also be
  true of the 5 segment design or the inline 4
  segment design.

18
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues

• SAIC assumptions
• SAIC, p.24 2. The 1995 Shuttle PRA 5,
  specifically the portions of that document that
  relate to the participation of the solid rockets
  in the shuttle risk, is representative.
• CSO Failure rates from other large SRB programs,
  at a minimum, should be included as well as the
  other failures in the STS SRB program
• SAIC, p. 24 4. The SRB/J-2S developed integrated
  design will be fully qualified for its launch
  environment. Specifically any additional launch
  vibrational loads or other environments will
  either be demonstrated to have fallen within the
  existing shuttle qualification envelop or will
  undergo delta qualifications for those
  environments that are not contained.
• CSO It is not apparent that the shuttle
  qualification envelope is appropriate to the new
  design.
• CSO Delta qualification could encounter
  unforeseen challenges or show stoppers

19
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues

• SAIC assumptions
• SAIC, p. 24 4 The SRB/J-2S design will be fully
  tested with an integrated test program including
  full scale flight tests to demonstrate flight
  readiness before crewed flights.
• CSO Full envelope qualification of the launch
  abort system in the presence of catastrophic SRB
  failures is likely to be difficult and expensive.
• SAIC, p. 25 11. There is sufficient warning
  time, and signals for 80 of the loss of control
  (thrust augmentation) failures.
• CSO There is no analysis that supports the 80
  claim.
• SAIC, p. 25 12. An escape system can be designed
  for the CEV that will provide escape capability
  after loss of control.
• CSO The Titan IV-A LOC (8/12/98) suggests that
  this may be difficult.
• 1.7 seconds elapsed between the full pitch
  command and vehicle breakup at an alpha of 13
  degrees. The time between a reasonable launch
  abort redline (5 degrees) and breakup was much
  smaller.

20
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues

• SAIC, p.96 SRB failure rates were developed
• By combining component failure rate data in an
  assessment tree a bottom-up approach was used
  to estimate a failure rate of approximately one
  in 7000 motor-flights,
• Through Bayesian update of U.S. solid rocket
  booster experience as recommended by a
  NASA-commissioned Independent Peer Review Panel
  (approximately one in 1500 motor-flights)
• Through an expert elicitation using Thiokol
  managers as experts, combined with a Bayesian
  update to estimate a failure rate of one in 3058
  motor-flights.
• CSO The differences in these three estimates is
  troubling given that the demonstrated shuttle SRB
  failure rate is, optimistically, 1/266 or
  realistically 1/15 (18/266).
• These discrepancies suggest something is askew in
  the world of reliability estimates.
• The current industry team LOV estimate for the
  inline RSRB configuration is 1/438

21
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues
Including other large SRB failures changes the
picture considerably
Initiator LOV Prob. (1/X) Crew Survival Events Crew Survival Events Crew Survival Events Crew Survival Events    
Initiator LOV Prob. (1/X) Crew Survival Events Crew Survival Events Crew Survival Events Crew Survival Events    
Initiator LOV Prob. (1/X)         Total Crew Survival LOC Prob. (1/X)
Initiator LOV Prob. (1/X)         Total Crew Survival LOC Prob. (1/X)
Initiator LOV Prob. (1/X) Escape Possible Escape-Separation Decell/Landing Recovery Total Crew Survival LOC Prob. (1/X)
SRB Control 320 100.00 80.00 100.00 99.00 79 1538
SRB-Immediate 160 0.00 100.00 100.00 100.00 0 160
Staging 13459 100.00 95.00 100.00 99.00 94 224317
Upper Stage 625 100.00 99.00 95.00 95.00 89 5867
Total 90     Integrated Survivability (1-90/141) Integrated Survivability (1-90/141) 36 141
22
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues

• Arbitrarily assuming all SRB failures are
  non-survivable yields a Loss of Crew Probability
  of 1/1750

Initiator LOV Prob. (1/X) Crew Survival Events Crew Survival Events Crew Survival Events Crew Survival Events    
Initiator LOV Prob. (1/X) Crew Survival Events Crew Survival Events Crew Survival Events Crew Survival Events    
Initiator LOV Prob. (1/X)         Total Crew Survival LOC Prob. (1/X)
Initiator LOV Prob. (1/X)         Total Crew Survival LOC Prob. (1/X)
Initiator LOV Prob. (1/X) Escape Possible Escape-Separation Decell/Landing Recovery Total Crew Survival LOC Prob. (1/X)
SRB Control 3086 0.00 80.00 100.00 99.00 0 3086
SRB-Immediate 13858 0.00 100.00 100.00 100.00 0 13858
Staging 13459 100.00 95.00 100.00 99.00 94 224317
Upper Stage 625 100.00 99.00 95.00 95.00 89 5867
Total 482     Integrated Survivability (1-90/141) Integrated Survivability (1-90/141) 72 1750
Since this LOC exceeds the desired 1/1000, CEV
weight growth and decreasing launch vehicle
perfomance margins could lead to pressure to
delete the 10,000lb ascent abort system.
23
Reliability and Crew Safety Assessment for Solid
Rocket Booster / J-2S Based Launch Vehicle
(SAICNY05-04-1F) Specific Issues

• SAIC, p. 120 Launcher reliability has a large
  impact on crew safety. Regardless of the launcher
  type, assuring crew safety after a failure is
  uncertain. Given the limited number of test and
  flight opportunities it will be difficult to gain
  sufficient understanding of the dynamics to
  create an escape system that can provide high
  assurance of escape. Unknown-unknowns will
  dominate the reliability of crew escape systems.
  Since there undoubtedly will be significantly
  more launch experience than abort experience, the
  uncertainty in the likelihood of launch failure
  will be less than the uncertainty in abort
  reliability. Furthermore, a good design should be
  focused on achieving safety inherently, not by
  adding safety systems as a crutch. This is
  because the operating environment for the safety
  system is almost always less known (and therefore
  cannot be counted on to be highly reliable),
  therefore the safety focus of design should
  always be directed at achieving the highest
  possible reliability and recovery failure systems
  added only afterward.
• CSO This philosophy seems contradictory to the
  findings, recommendations, and observations of
  previous accident investigation boards. (link)

24
CSO Comments on ESAS Integrated SRB Abort
Assessment

• The comparison should be between the Single Stick
  SDLV and a liquid fueled vehicle. (link)
• Side mount SDLV has already been ruled out
• Safety Drivers omits relevant facts from Single
  Stick claims (link)
• Thrust Augmentation leads to slower single stack
  break-up is an assertion for which there is very
  little substantiating analysis.
• Thrust Augmentation can lead to interactions
  between stages on the Single Stick
• Thrust Augmentation can lead to upper stage
  propellant mixing/conflagration on the Single
  Stick

25
Conclusion

• It is the opinion of the CSO that the ATK/SAIC
  Loss of Crew prediction for the inline RSRB
  configuration is over-optimistic and should not
  be the basis for selecting the next crewed launch
  vehicle.
• Historical data suggests that exceeding a 99
  launch success rate for solid propellant vehicles
  is improbable.

26
CSO Recommendations

1. Non-selection of the inline SRB design for the
   crewed launch vehicle based on inability to meet
   the current Human Rating Requirements, NPR
   8705.2.
2. If the inline SRB design is pursued, establish an
   independent analysis and review effort to assess
   SRB success rates, failure modes, failure
   dynamics, failure detectability, and to define
   the catastrophic failure environments in which
   any launch abort system would have to
   successfully operate and determine the
   appropriate test and qualification program for
   that launch abort system.
3. The agency perform a detailed comparison between
   the inline RSRB and EELV derived or other all
   liquid LV configurations using consistent
   criteria as to what counts in the reliability
   statistics

The Agency is in the process of selecting a human
launch vehicle that will most likely be used for
the duration of the exploration program.
Historical evidence and the lessons from past
accidents should be applied in that
selection. Those who cannot remember the past
are condemned to repeat it. George Santayana
27
BACKUP

1. Crew Survival Definitions
2. Launch Failures by Subsystem Root Cause of
   US-Built Expendable Vehicles 1984-2004
3. SRB Anomalies from JSC19413 (Greenbook)
4. ESAS Integrated SRB Abort Assessment

28
Crew Survival Definitions

• Abort Termination of the nominal mission that
  allows the crew and passengers to be returned to
  Earth in the portion of the space system used for
  nominal entry and touchdown.
• Escape Removal of crew and passengers from the
  portion of the space system normally used for
  reentry, due to rapidly deteriorating and
  hazardous conditions, thus placing them in a safe
  situation suitable for survivable return or
  recovery. Escape includes, but is not limited
  to, those modes that utilize a portion of the
  original space system for the removal (e.g.,
  pods, modules, or fore bodies).
• Rescue The process of locating the crew,
  proceeding to their position, providing
  assistance, and transporting them to a location
  free from danger.
• Safe Haven A functional association of
  capabilities and environments that is initiated
  and activated in the event of a potentially
  life-threatening anomaly and allows human
  survival until rescue or repair can be affected

29
Launch Failures by Subsystem Root Cause of
US-Built Expendable Vehicles 1984-2004
Source Futron Design Reliability Comparison for
SpaceX Falcon Vehicles November 2004
30
SRB Anomalies from JSC19413 (Greenbook)
STS Vehicle Description
2 102 RH SRM aft field joint gas leak to primary O-ring with erosion
6 99 Gas paths on both SRM nozzle-to-case joints
8 99 Abnormal erosion pattern of nozzle nose rings
41C 99 Gas leak and erosion to primary O-ring of RH SRM nozzle-to-case joint
41D 103 RH SRM forward field joint erosion LH SRM gas leak and erosion to primary O-ring of nozzle-to-case joint
51A 103 LH SRM nozzle throat inlet ablative ring separation from housing
51C 103 LH SRM forward field joint gas leak and erosion to primary O-ring RH SRM primary O-ring gas leak and erosion at center field joint Gas leaks to primary O-rings at nozzle-to-case joint on both SRMs
51D 103 RH SRB nozzle throat ring developed erosion pockets Gas leak and erosion in both SRM nozzle-to-case joints
51B 99 RH SRB gas leak at primary O-ring of forward field joint Gas leak and erosion in both SRM nozzle-to-case joints. Erosion to secondary O-ring on LH SRM
51G 103 Gas leaks and erosion on both SRM nozzle-to-case joints Gas leaks, but no erosion in either SRM igniter joint
51F 99 LH SRM nozzle throat inlet ablative ring separation from housing Gas leak in the RH SRM nozzle-to-case joint Gas leak but no erosion to LH SRM igniter joint
31
SRB Anomalies from JSC19413 (Greenbook)continued
STS Vehicle Description
51I 103 Gas leak in the LH SRM nozzle-to-case joint Gas leaks in both inner and outer seals of LH SRM igniter joints. No seal damage Gas leaks, but no erosion to outer gasket of RH SRM igniter joint
61A 99 LH center and aft field joints had gas leaks to primary O-rings RH forward field joint gas leak at primary O-ring Gas leaks occurred at both SRM nozzle-to-case joints. O-ring erosion to the right joint but not the leak. Gas leaks, but no erosion to outer seal of both SRM igniter joints
61B 104 Gas leaks and erosion in both SRM nozzle-to-case joints Gas leaks but no erosion to outer seal of both SRM igniter joints
61C 102 LH SRB aft field joint gas leak and erosion at primary O-ring Gas leak in the LH SRM nozzle-to-case joint Gas leak and erosion in the RH SRM nozzle-to-case joint Gas leaks, but no erosion to outer seal of both SRM igniter joints
27 104 Ignition/igniter heaters charred. Some heat damage and charring was evidenced by discoloration at two locations of both igniter heaters.
29 103 Approximately 95 percent of the glass cloth phenolic insulator and 100 percent of the carbon cloth phenolic liner was missing from the left SRM aft exit cone.
28 102 Right SRM aft center segment ply separations of internal insulation. During postflight inspection operations at KSC, a ply separation was identified in the internal insulation of the right SRM aft center segment.
33 103 The left SRB ETA ring aft IEA end cover experienced hot gas flow (aft to forward) through its interior from the tunnel side, resulting in sooting and varying degrees of heat exposure to 16 operational flight reusable cables.
32
SRB Anomalies from JSC19413 (Greenbook)concluded
STS Vehicle Description
31 103 The RSS crossover bracket on both SRB's is sooted around the P2 connector jam nut. Also, ballooning of the heat shrink tubing was observed on one cable in the right SRB RSS transition housing.
41 103 During the postflight inspection of both the left and right SRM igniters, the outer joints were found to have a blow-hole in the putty. Also, cadmium plating damage and sooting was observed. Abnormal erosion of the internal insulation (at the forward edge) was observed in both the left and right SRM aft dome-to-stiffener and stiffener-to- stiffener factory joints.
35 102 During the follow-on postflight inspection of the left RSRM nozzle joint 3 at TC, a 1.5-inch gas path was observed through an RTV void at 195 deg, resulting in heat effects to the CCP surface and sooting to the primary O-ring.
39 103 Excess erosion on right RSRM nozzle cowl and outer boot ring.
48 103 During postflight inspection of the right SRB lower strut, a black mark with flow lines was observed at the ET/SRB strut segment interface.
44 104 During the SRB recovery operations, the retrieval team reported structural damage to the left SRB forward skirt, systems tunnel, and ETA ring.
42 103 The left and right RSRM nozzle-to-case joints had gas paths through the poly-surfide adhesive with erosion and sooting of the wiper O-rings. Gas penetration on the left side was more extensive as blowby was observed at the wiper O-ring.
71 104 Nozzle internal joint 3 gas path/primary o-ring erosion
70 103 Nozzle internal joint 3 gas path/primary o-ring erosion
75 102 Dual gas paths through the polysulfide to the wiper O-ring-in the nozzle-to-case joints of both RSRM's
78 102 Sooting/heating effects beyond the insulation J-leg tip on field joints.
79 104 Right-hand nozzle striated axial erosion on the throat and forward exit cone
33
ESAS Integrated SRB Abort Assessment
MSFC Solid Hybrid Propulsion Systems
Branch, Abortability Assessment RSRM, April 2005.
34
ESAS Integrated SRB Abort Assessment (contd)
MSFC Solid Hybrid Propulsion Systems
Branch, Abortability Assessment RSRM, April 2005.
35
ESAS Safety Drivers - Boost Stage
Reliability Drivers Single Stick SRB Shuttle EELV (Triple Core)
Simplicity Single Element 2 SRBs plus 3 Staged Combustion Engines 3 Engines ( with 2 Turbo Pumps) 3 Feedback Control Systems (1 Staged Combustion) 3 Propellant Management Systems 3 Purging Systems
Dynamics (Moving Parts) 1- TVC 5 TVCs, 6 High Performance Turbo Pumps with Pre-Burners 3- TVC 6 Turbo Pumps, 3 Throttle Valves, Numerous Prop Management Valves
Understanding of the Environment (Margin) 226 Flight Operations, with post flight inspection 113 Flight Operations 1 EELV Heavy flight, conflagration during Delta launch, LOx Rich Environment(RD-180)
Process control and feedback Post Flight Inspection, production process controls Post Flight Inspection (except ET), production process controls No post flight inspection Rely on process control in flight (red-lines)
Survivability Drivers
Trajectory (g- loads on abort re-entry) Crew escape Flatter Trajectory with mild G-Loads No crew escape system Crew escape more lofted trajectory with higher loads on crew (more so with Delta). Can be mitigated with new upperstage.
Accident environment Thrust Augmentation leads to slower single stack break-up SRB Thrust augmentation leads to immediate break-up and potential propellant mixing/conflagration Thrust imbalance or engine shutdown can lead to interactions between stages, LH2 Explosions (Below 10K), RP explosions at higher elevations, no empirical data on explosive environments
36
ESAS RSRB - Safety and Reliability

• Simple Inherently Safe Design
• Design Robustness
• Historically Low Rates of Failure
• Non-Catastrophic Failure Mode Propensity
• Process Control
• Failure Precursor Identification and Correction

The estimated reliability for a 4-segment SRB,
based on QRAS2000 model, is 99.97
Demonstrated Shuttle RSRB reliability is more
than 3 times that of other large SRBs
Major redesign conducted after the Challenger
accident significantly increased the expected
reliability of the SRB
37
ESAS Significant Benefit for Post Flight
Inspection
Number of Shuttle SRB Post Flight Issues vs.
Flights