Apollo 16 Mission Risk Assessment

¶APPEND IX APOLLO 16 MISSIONRISK ASSESSMENT EXCERPTS AND SUMMARIES The following pages have been extracted as typical examples of the Apollo 16 Mission Assessment Report.

¶"1.2 PURPOSE The purpose of this assessment is to define and evaluate the risks associated with the Apollo 16 flight and lunar surface activities, to provide justification for discounting or accepting these risks, and to present an overall picture of the mission relative to crew safety.

¶"1.3 SCOPE This document is limited to the presentation of the assess - ment of the Apollo 16 mission as related to flight crew safety from lift-off through earth landing. The assessment included analysis of each mission phase, including procedures, configurations, and potential impact of previously-observed anomalies on flight crew safety. This document applies to the MSC Flight Readiness commitments. Subsequent anomalies are evaluated on a day-to-day basis up to the launch time and are incorporated into this document as required.

¶"1.4 CONCLUSIONS

1.4.1 The new risks introduced into the Apollo 16 mission are

¶acceptable and provide no flight constraints.

1.4.2 Assessment of the planned lunar surface activities, including the longer EVA'S, longer traverses, and delta lunar

¶surface experiments has uncovered no safety concerns which preclude the lunar activities or any planned lunar surface experiments. Improvement in the active seismic experiment from Apollo 14 has increased the safety margin for Apollo 16.

1.4.3 Assessment of the rendezvous technique changes which are

¶incorporated for Apollo 16 indicate they should minimize controllable errorsin the rendezvous calculations, thus improving overall mission success and crew safety.

1.4.4 Boom retraction modification of adding.proximity switches

¶has increased safety by.enabling determination if booms are sufficiently retracted before an SPS burn. (See note 1 below. )

1.4.5 Planned CM in-flight demonstrations have been assessed

¶for concerns related to crew safety, and no constraining safety concerns were identified. (See note 2 below.)

¶Note 1. The mass spectrometer and gamma ray spectrometer experiments were extended from the SM Scientific Instrumentation Module by retractable booms. It is critical to have assurance that these booms are properly retracted before attempting an SPS burn; an unretracted boom could conceivably wrap around the SPS nozzle extension. Proximity switches were added on Apollo 16 to provide the crew positive assurance of boom retraction prior to the SPS burn. In addition, a boom jettison capability was added.

¶Note 2. During transearth coast, Apollo 16 crew conducted the following inflight demonstrations, each requiring experiment hardware and procedures which were subjected to safety analysis: (1) ALFMED (Apollo Light Flash Moving Emulsion Detector) (2) MEED (Microbial Ecology Evaluation) (3) Electrophoresis In- Flight Demonstration (4) Biostack Experiment (M211)

1.4.6 Safety assessments of anomalies occurring during manned

¶environmental tests, previous flights, and vehicle ground tests have disclosed no significant safety concerns.

¶"1.5 RECOMMENDATIONS None.

¶'Service propulsion system.

¶Command module.

¶3Service module.

¶??1.6 SAFETY STATEMENT APOLLO 16 MISSION The Safety Office assessment of the planned Apollo 16 mission, spacecraft functions, and hardware failures disclosed no safety concerns which constrain the Apollo 16 flight scheduled for April 16, 1972. The assessment is based on safety analyses performed in coordination with and obtained from the Program Office, E&D, FOD, FCOD, MR&OD, SR&QA, and the hardware contractors. '' Section 2.0 provided a discussion of all constraining and nonconstraining safety concerns evaluated during the mission assessment. These concerns were assessed for crew safety during the period leading to the preparation of the report and were published in the MSC Safety Concerns document, released biweekly. The information included the issue, action, and status of each concern. The following list enumerates the concerns contained in the Apollo 16 Mission Assessment Report.

1. Range/range-rate meter glass shattered

2. Command and service module (CSM) criticality 1 switches

3. Gyro-display coupler aline function

4. Scratched Lexan window shade

5. Loose object in the cabin fan

6. Unexplained pressure increase in the CSM tunnel

7. Broken bacteria filter on water gun

8. Main oxygen regulator failure

9. Premature deployment of main parachute

10. Failure of docking ring to sever

11. Extravehicular glove wear

12. Command module (CM) reaction control system (RCS) fuel tank

¶excessive delta pressure

13. Parachute reefing-line cutter

¶Engineering and Development Directorate; Flight Operations Directorate; Flight Crew Operations Directorate; Medical Research and Operations Directorate; and Safety, Reliability, and Quality Assurance Office.

14. Entry monitor subsystem "thrust on" light

15. Pressure garment assembly qualification test failure

16. Suited or unsuited scientific instrument module door jettison

17. The CM RCS oxidizer tank bladder overpressure

18. Impact test failure of helmet

19. CSM- 113 propellant utilization and gaging system anomaly

20. Trapped CM RCS propellant overpressure

21. Circuit breaker mechanical latch problem

22. Earth landing system main parachute failure

¶The following information is contained in the report covering item 22, which illustrates the depth at which each item ( 1 to 22) was considered.

¶"Issue - The crew verified and photographic coverage confirmed that one main parachute collapsed at an altitude of 6,000 feet during the Apollo 15 mission. Four of the six nylon risers had released their suspension-line load. Loss of one main parachute exposed the crew to higher, but acceptable, loads; however, failure of more than one parachute could result in crew loss.

¶"Action - An NR investigation and analysis revealed the cause of main parachute collapse not to be forward heat shield, the suspension links, or the steel risers being pulled from the flower pot. The most probable cause of the anomaly was the burning raw fuel (monomethylhydrazine) being expelled during later portions of the depletion firing. This resulted in the exceeding of the parachute-riser and suspension-line temperature limits. Corrective action taken has been to change the mode 1A abort timer to 6 1 seconds, to design and qualify new connection links made of Inconel 718, to load propellants to achieve a slightly oxidizer-rich mixture for a possible depletion-burn purge, and to require certification of the CM to land in the water with pressurized propellants onboard. Oxidizer and parachute tests at the NASA WSTF (White Sands Test Facility) are being conducted to investigate the effects of the CM RCS dump burn depletion and purge on the parachute assemblies.

¶Recovery procedures and training are being updated to avoid possible crew exposure to toxic propellants as a result of the single failure points of the pressurized tanks at shutdown.

¶5North American Rockwell Corporation, prime Apollo contractor.

¶"Status - The concern has been closed on the basis of: (a) The decision to land on water with pressurized tanks and 1Z regime. The Safety Office will (b) The decision to extend the mode continue to scrutinize the current WSTF RCS/oxidizer tests for impact. " Section 3. 0 of the Mission Assessment Report contained the Flight Operations Safety Analysis. The analysis was divided into approximately nine areas with each addressing a mission phase; for example, launch through orbit insertion, lunar orbit insertion, lunar module powered descent, lunar surface activities, et cetera.

¶Section 4.0 defined the safety evaluation of flight hardware differences between the mission under assessment and previous missions, the waivers and deviations, and the sneak circuit analyses for the upcoming mission.

¶Section 5.0 covered the manned environmental ground tests pertinent to the upcoming mission performed at the Space Environment Simulation Laboratory at the MSC.

¶Section 6.0 subjected anomalies from previous missions to analysis. Included were numerous anomalies from the previous missions that were evaluated for safety impact; breakdown by command and service module, lunar module, and Government-furnished equipment; and the status of each with respect to the upcoming mission.

¶Section 7.0 was an evaluation of real-time flight problems and was not contained in the first two releases of the Mission Assessment Report; this section was added after splashdown and recovery.

¶NASA-Langley, 1975 S-422