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In article ,
Robert Briggs writes: Alan Minyard wrote: At apogee there would be almost no control authority (lack of sufficient air molecules). Do they have a thruster system for control at that altitude?? If there is *any* remotely usable control authority then the thing ain't in space for any reasonable value of "space". A couple or three points: Control Authority doesn't have to mean aerodunamic controls - SS1 has a cold-gas RCS system for attitude control a very low EAS. There is no such thing a "a reasonable value of 'space'". It's not like there's a definite dividing line between Atmosphere adn Vacuum - the density of the atmosphere thrails off as height increases, but it doesn't entirely go away. Aerodynamic drag, and the variations in that that occur was the Earth's atmosphere expands and contracts due to Solar Radiation, are a significant factor in the lifetime of an orbiting satellite. (Remember Skylab). That Orbital Decay that you hear so much of is mostly caused by atmospheric drag. (By the same token, I'd like to punch Eugene Sanger, or his translators, in the nose for starting that whole like of crap about "skipping" off the Earth's atmosphere with a lifting spacecraft. It doesn't and can't happen that way. The only way to change your vector with such a craft while re-entering is to fly up, rather than bounce up - you've got to be flying fast enough, in thick enough air, to allow a normal pull-up. (As a reference, note that Columbia had almost reached an EAS that would have allowed a pull-up, but hadn't yet)) The definition of where "space" starts is completely arbitrary. The USAF specifies it as 50 miles MSL. The FAI specifies it as 100 km. -- Pete Stickney A strong conviction that something must be done is the parent of many bad measures. -- Daniel Webster |
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