Representative Space Transfer Vehicles

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Each OMV has approximately the same OEW as indicated in Figures 5.6, 5.7 and 5.9. But each has a different configuration that is determined by the characteristics of the individual propulsion system, as depicted in Figure 5.18. The two chemical rocket-powered OMVs are similar and conventional. Although having different gross weights, they are similarly sized. The satellite attaches to an equipment module mounted on the front end of the propellant tank, where the guidance and control systems and all subsystems are housed. There would be a stowed communications antenna and solar panels for power in the equipment module (not shown). The solar electric propulsion system would require much larger solar panels than shown. Current communications satellites have solar panels in the 25 to 30 m (82 to 98 ft) total span for thrusters with less than one-tenth the thrust required for the solar electric OMV. Some of the limitations of this system are the current low thrust levels; the continuously degrading solar panel output; and the unwieldy size of the solar panels for such a vehicle. Nuclear electric has the same problem as the solar electric in that current thrusters have less than one-tenth the thrust required for the nuclear electric OMV. This system does have the advantage that the power output is sufficient and constant. There is a requirement for large radiators to dissipate the rejected thermal energy from the reactor to space. Their exact size depends on the nuclear

Figure 5.18. Relative size and general configuration of OMVs.

system chosen and the thermodynamic cycle to power the electric generators. The nuclear reactor will be a space-designed reactor and not based on Earth-based nuclear power stations. A most likely candidate is some type of gas-cooled reactor.

A round trip operational OMV that travels from LEO to GSO and returns is shown in Figure 5.19. The solar panels are just sufficient to power the system electronics and other electrical subsystems. A communications link to Earth and space-based ground stations is indicated. Because the intended life is years, and recalling the damage one of these authors (PC) witnessed on the LDEF satellite, a

Figure 5.19. LEO-GSO-LEO two-way OMV with shield.

Hydrogen/oxygen

Hydrogen/oxygen

Figure 5.20. OMV for impulse turn and hypersonic glider for aerodynamic turn.

shield over the tank structure and engine is necessary, as shown in phantom. The equipment module can be made robust enough not to require a separate shield. As with the MIR orbital station, the solar panels on an operational OMV will probably have to be replaced within its lifetime.

The orbital plane change OMV can change the orbital plane by an impulse turn in orbit or an aerodynamic turn in the upper atmosphere. The impulse plane change OMV is very similar to the OMV shown in Figure 5.19 and is shown in the left side of Figure 5.20. The aerodynamic plane change OMV is shown in the right side of Figure 5.20. Both are sized for a 32-degree plane change with a 2,268 kg (5,000 lb) satellite. The OMV cannot enter the Earth's atmosphere, so it is limited to space operations. The glider has the capability to enter the atmosphere to operate as a rescue vehicle. The glider has a glide range equal to the Earth's circumference and can return to Earth without any prior preparation or waiting in orbit. With a payload bay of 36.5 m 3 (1,289 ft3) capacity it could accommodate nine to twelve persons in pressure suits in an emergency situation.

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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