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3.  Bailout Studies

Since the ejection seat removal, several studies have been conducted on alternative methods of egressing the spacecraft during flight.

Aerodynamic model tests were conducted to determine if a crewman could egress through the side or overhead hatches and use personnel parachutes.  It was concluded that hazardous contact with the wing, tail or OMS pod would result due to aerodynamic flow characteristics, and auxiliary methods were required to provide sufficient delta-V (crew exit velocity) to avoid these obstacles.  Slides and pendant rocket systems were evaluated.  All concepts of bail out require time on the order of "minutes" to get the full crew complement clear of the vehicle; therefore, these concepts have no utility during first stage flight.  The use of these systems would be limited to controlled descent flight.  The results of these studies were presented to Space Shuttle Program Management, but were not implemented due to their limited capability and resulting program impacts.

B.  Orbiter Ditching

Ditching studies were conducted in 1974 and 1975 at Langley Research Center to determine the best procedure to improve the survivability of a water landing.  Results of these studies are shown in figure C12 and C13.  The data presented in these figures show that acceleration loads were measured at water entry as high as 6g longitudinally and 10g in the normal direction.  The key variables are vehicle attitude, velocity, sink rate, and sea state.  It was concluded that Orbiter external shape and mass properties were advantageous to ditching;  however, the high landing velocity and resulting decelerations may cause structural failure of the cabin support ties to the fuselage, thus inhibiting egress and potentially flooding the pressure cabin.  If the pressure cabin remained intact, the flotation attitude should be acceptable for egress.

Figure C14 is a summary of the ditching studies, and figure C15(a) is a comparison of the system design requirements for the cabin link ties and the payloads carried in the payload bay.  The design requirements for the payloads are lower than most of the accelerations measured in the test program;  therefore, it can be expected that there is potential for the payloads to structurally fail and that the resulting debris and/or explosion will be hazardous to the crew.  It should be noted that the g levels in figure C12 and C13, and the summary in C14 may present an optimistic view of the ditching situation.

There are many variables that affect a successful ditching, and they are difficult for the pilot to control.  The high velocities and the difficulty in judging the height over the water, due to few visual cues, limit the ability of the pilot to control the vehicle's entry into the water.  It is reasonable to expect higher acceleration loads than those indicated by the model testing.  These considerations tend to discard the lower-g impact measurements shown in figure C13 as

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Transcription Notes:
This doc has been thoroughly reviewed. Errors corrected in reopining are as follows: Fixed spacing issue in first paragraph Document read resented instead of presented in 2nd paragraph Document read Orbital instead of Orbiter in 3rd paragraph Missing comma in final paragraph