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4. Ascent Flight Envelope Expansion

For a discussion of the ascent flight envelope, see reference 1. In summary, the approach to verifying the data base and obtaining the date required to remove ascent placards and constraints is conservative. The envelope, in fact, had been reduced as a result of data obtained on previous flights. There are no attempts to reduce the launch margins or pressures to perform dynamic tests that would result in the Space Shuttle flying outside of the conservatively established ascent envelope. The expansion of the envelope is dependent on obtaining data from flights on an instrumented Orbiter with large planned performance margins. These flights were planned for future missions. In general, the expansion of the ascent flight regime is still in the development phase.

5. Entry Flight Envelope Expansion

A discussion of the entry flight envelope is contained in reference 2. The capability of the Orbiter to perform the entry flight phase is a function of many complex systems, developed by many disciplines, and integrated by members of the disciplines working together. These systems have performed well and the Orbiter capabilities are considered verified to specification requirements (except for landing and rollout system; see appendix B). There are a small number of open issues being actively worked to expand the Space Shuttle entry envelope. These include expanding the system performance capabilities outside of the specification envelope and development of abort propellant dump capabilities to control center of gravity and total landing weight.

In general, Space Shuttle entry capability for flights launched from the Eastern Test Range (ETR) is considered to be operational. For flights from the Western Test Range (WTR), the thermal/structural capabilities continue to be assessed due to high predicted entry temperatures and thermal gradients.

Entry testing continues on a flight-by-flight basis. The approach is conservative, and no pressure has been placed on the system to fly outside of the conservatively established entry flight envelope.

6. Payload Safety

The payload safety process ensures that each payload is safe to fly and that the total integrated cargo complement does not create a hazard. The implementation of this process is consistant [[consistent]] with the overall program policy to minimize NSTS involvement in the payload design process; that is, the payload developer is responsible for assurrance [[assurance]] of safety and verification of compliance with requirements. The safety panel safety and hazard control assessments are based on material presented by the payload developer. The NSTS Safety Review Panel is chaired by the Assistant Manager for Payload Safety of the STS Integration and Operations Office. The responsibilities of the

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