Design Considerations for Orbital Transport Systems 670383
Applications of Earth orbital platforms like communication satellites have already achieved a commercial value in their own right. Other Earth centered operations like weather satellites offer the possibility of a commercial status since they affect our daily lives by supplying information on the state of nature around us.
We, therefore, feel justified in assuming that a solid basis for expansion of Earth-orbital operations exists. Present projections of manned and unmanned orbital launch requirements indicate that more economic means of space transportation will be needed.
Starting from our present day hardware, the key question is, should we simplify or sophisticate our vehicle concepts? The paper addresses the two following problem areas:
The implications of operational “requirements” on systems design, performance and cost: These considerations include mission parameters, considerations of man's safety and comfort, overflight of populated areas, sonic boom, abort and flyback capability, vehicle turn-around, etc.
The implementation of the systems development: Do we propose a quantum jump requiring a large, concentrated development expenditure, or is there an alternative in a more modestly paced evolutionary approach in which annual funding and development risk are limited?
Various development approaches and their systems sensitivities were put into context with a mission model and evaluated for utility, cost and development risk.
The first new development seen is that of a reusable passenger vehicle designed for orbital use to replace the Apollo command and service modules. Next, or concurrent, are improvements in economy and operations of the launch vehicle. Partially reusable transportation systems appear most promising on the basis of the mission model used. Relatively small additional savings, associated with high uncertainties, may be expected from a fully reusable system. A choice will have to be made on the basis of economical growth potential and operational considerations.
In the case of funding-intensive developments, such as reusable launch vehicle stages, an evolutionary development provides a capability extension at a reduced annual funding rate resulting in only a Slight penalty in total program cost.