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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 1973-1983 with no change in the philosophy that first stage ascent must be assured.

B. Summary of the Options for Augmenting First Stage Aborts

1. Ejection Seats

Ejection seats and pressure suits are not viable Space Shuttle options because they limit the crew size and, therefore, prevent the Space Shuttle from accomplishing many of its mission objectives. Furthermore, they provide very limited increase in survivability for the total range of potential first stage failures.

2. Bailout

Bailout options are limited to cases in which the Orbiter is in controlled flight because of the precise Orbiter flight conditions and long times required for crew preparation and egress. Optimum utility appears to be involved in cases in which the Orbiter, through a contingency situation, is constrained from access to a prepared runway. Bailout will allow the crew to egress the Orbiter and avoid a very hazardous landing. Utilization during first stage contingent situations is impossible. The number of first stage contingencies that result in long periods (10's of seconds) of controlled flight are small in comparison to the total. This option offers an escape path for the crew in the contingency abort cases that result in water ditching.

3. First State Intact Orbiter Abort

First stage intact Orbiter aborts are defined as the process of safely removing the Orbiter from the ET-SRB "stack" during first stage burn, and of returning it safely to a landing site (fig. C21).

• 50 < mission elapsed time (MET) < 70 seconds:
RECOVER ORBITER AND CREW: Requires:
- SRB thrust termination
- Redesign of ET-SRB forward attach
- Significant guidance, navigation, and control (GN&C) design and development for the separation and glideback flight
- Substantial aerodynamic data base development to support the GN&C design
- Design and certify a "quick" SSME shutdown technique

-C15-          

Transcription Notes:
Reopened only to correct one spelling error. This document has been thoroughly reviewed and is ready for completion.