Newsgroups: sci.space.shuttle Path: utzoo!henry From: henry@utzoo.uucp (Henry Spencer) Subject: Re: Misc Shuttle questions Message-ID: <1989Dec6.164948.632@utzoo.uucp> Organization: U of Toronto Zoology References: <32253@cci632.UUCP> Date: Wed, 6 Dec 89 16:49:48 GMT In article <32253@cci632.UUCP> lmm@cci632.UUCP (Lance Michel) writes: > 1. Couldn't a (removable) additional fuel tank be mounted > in one of the shuttles. And say (for sake of discussion) > that this tank took up most or all of the payload area. Then > could the shuttle reach high orbits, maybe even geosync. orbit? > Would there be any advantage to such a mod? Well, it could probably be done. Of course, if it's fuel for the main engines, as opposed to the OMS engines (I'm not sure which would be preferred. The main engines have a significantly higher exhaust velocity, but hydrogen is very bulky. It would depend on whether the cargo-bay tanks turned out to be weight-limited or volume-limited, I guess.), that brings back the hysteria about cryogenic fuels in the payload bay. It would get you to a somewhat higher orbit. I don't think it would get you to Clarke orbit, though: the orbiter is much heavier than its payload, and the added performance would be relatively modest. Just getting up to somewhat higher orbits than usual is not spectacularly useful; in particular, you do *not* want to take a manned mission higher than about 1000km for any length of time unless you're going straight out at high speed, because the inner Van Allen belt is not a good place for humans. It's also not clear what use such a mission would be without any payload, unless it was something like a repair mission for a high-value satellite. > 2. If a sat. is in geosnyc, is it very stable there? Or does it > require hydozine adjustments like other lower sats? Will a > geosync ever come down if left unattended? The orbital lifetime that high up is very long, infinite for all practical purposes. However, if you want a satellite to stay in *one spot* in Clarke orbit, then you do need stationkeeping thrusters. Various small perturbations -- for example, lumpinesses in the Earth's gravitational field -- make satellites in Clarke orbit drift slowly, and periodic corrections are needed. Some of the newer comsats actually use small ion rockets for this (!), since stationkeeping fuel is often the limiting factor in comsat lifetime. > 3. What about the LDEF. When Columbia brings it down it will be > a record landing weight correct? ... Actually, I think one of the Spacelab missions may hold that distinction, but I'm not sure and I don't have numbers handy. > ...Could any of > the shuttles perform this task, or does it require the "Mack > Truck" of the fleet? ... No, or they wouldn't send Columbia! Compared to the later orbiters, Columbia is somewhat overweight to begin with. > 4. This question I just have to ask: Henry S. (In Toronto), how > do you know all this stuff? Where do you get these resources? A lot of it is just persistent interest and a lot of reading and following of cross-references. For the shuttle, there is actually a lot of technical detail in NASA's Shuttle News Reference, which is intended to answer most technical questions that the media might have. The National Space Society and several other groups sell reprints of it. For more detail, World Spaceflight News (Box 98, Sewell NJ 08080) publishes a long list of special reports based on NASA material which go into nitty-gritty detail about shuttle systems and equipment. (WSN itself publishes things like the complete flight plan and cargo manifest for each shuttle flight, the postflight reports, and complete texts of things that are hard to find elsewhere [e.g. the Kerwin medical/forensic report on Challenger, the entire Ride Report, Feynman's appendix to the Rogers Commission report, etc.]. Highly recommended.) > ... Do you make any public appearances regarding > space technology, if so when and where, (I'll be there!) Not unless you count an occasional talk at the Canadian Space Society meetings here, and regular attendance at the BIS parties at the World Science Fiction Conventions. -- 1233 EST, Dec 7, 1972: | Henry Spencer at U of Toronto Zoology last ship sails for the Moon. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu