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caution. Waveoffs for marginal situations should be readily accepted and applauded at all levels of management throughout the program.

For further discussion on weather, refer to appendix B.

b. Crew Escape Systems
The NSTS considered all known methods of providing Orbiter and/or crew recovery from emergency situations during the first stage of ascent flight. Ejection seats and pressure suits were provided for the Orbital Flight Test (OFT) Program, although they afforded limited capability. Additional methods for the post OFT period were either baselined and then deleted or considered and not implemented because of one or a combination of limited utility, technical complexity, lack of reaction time and appropriate cues, cost and schedule, and/or performance and mission objectives impact (see app. C). Because of these factors, the NSTS adopted the philosophy that the reliability of first stage ascent must be assured through conservative design, testing, and certification to preclude time critical failures that prohibit the continuation of flight through SRB burnout. On the other hand, Orbiter avionics software changes were pursued aggressively to enhance survivability for cases beyond the accepted program risk level of Fail-Safe. Many of these proposed software changes were incorporated because of the low cost-to-benefit ratio. 

During the Space Shuttle development period, the question of first stage abort provisions was revisited many times by all levels of NASA management from 1973 to 1983 with no change in the philosophy that reliable first stage ascent must be assured. The options available to the program today to enhance crew escape capability from emergency situations appear to be identical to those considered early in the program, with the added complication that implementing major changes, such as escape pods, within the current Orbiter design would not be possible. Ejection seats limit the crew size and, thereby, the utility of the Space Shuttle. Furthermore, they provide very limited increase in survivability for the total range of potential first stage failures. Bailout options offer an escape path for the crew in the contingency abort cases that result in water ditching, but utilization in first stage contingency situations is impossible. 

First stage intact Orbiter abort options require major changes in the Space Shuttle system and would result in major performance impacts. Also, these options would not recover the Orbiter for all failures throughout the first stage. An escape pod can offer an opportunity for crew escape at all altitudes during first stage contingency situations if the pod is not damaged to the point that it cannot function. The implications of implementation are a significant redesign of the Orbiter and major loss of payload capacity. An escape pod with termination of SRB thrust theoretically offers the widest range of crew escape options. However, the implications of full implementation are development of SRB thrust termination, redesign of the forward SRB-ET attach fittings, design and certification of a technique for quick shutdown of the SSME's, significant redesign of

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