For the purposes of this exercise, an attempt was made to configure such a Powersat into a realistic design. The purpose was not to propose an optimal technical or economic solution, but rather to demonstrate what could be practical with more or less existing technology and systems. The overall configuration is shown in Figures 4.2-2 & -3. The main driver for this Powersat configuration was for it to be launchable on one Ariane 5. and operate autonomously for 5-10 years before being replaced. In was not considered practical to incorporate a servicing capability into Powersat simply because Hermes’ limited pay load and flight rates mean it is simply incapable of performing such servicing missions. Further, high launch costs might make a servicing mission as expensive as launching a new Powersat in the first place. The Shuttle could potentially perform the servicing function. However, all of its yearly missions are expected to be tied up in meeting Freedom’s support needs. Beyond these two vehicles, the only other possibility is to develop a variant of the proposed Ariane V Transfer Vehicle (see Section 5) that is capable of performing an automatic rendezvous and docking with the Powersat. However, even here servicing operations would need to be limited to propellant loading only. Any other activities, such as replacing failed units, would probably be more expensive than launching a new Powersat because the telerobotic and other systems would be discarded. For all of these reasons, it was decided that the most suitable Powersat configuration would be one that is similar in configuration to today’s highly integrated communications satellites, although considerably larger. Approximately 200-300, 250 W space-qualified TWT amplifiers (12 GHz) are arranged at 200 mm intervals along the space-facing radiator walls. These tubes w'ere chosen over the use of one or more large klystron or gyrotron microwave generator sources for a number of reasons. Most notably, a suitable klystron or gyrotron generator does not exist in Europe for space applications. The TWTs,
RkJQdWJsaXNoZXIy MTU5NjU0Mg==