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T,D&E
On Thu, 11 Sep 2003 22:19:54 GMT, (Henry Spencer)
wrote: In article , Doug... wrote: It seems to me that the most difficult T,D&E (transposition, docking @ extraction) in the Apollo program was on Apollo 9. This is because Apollo 9 did it in LEO, where translation maneuvers almost immediately cause non-intuitive relative motions between spacecraft... At least, that's how it seems to this math-deficient brain... does this theory have merit? Alas, not very much. The counter-intuitive effects of orbital dynamics are largely absent when ranges are short and relative speeds are low. ....And, for that matter, if TDE is done with the stack perpendicular to the Earth at the start of the manouver, aren't the translational effects diminished, or am I simply not drunk enough to grasp orbital mechanics again? OM -- "No ******* ever won a war by dying for | http://www.io.com/~o_m his country. He won it by making the other | Sergeant-At-Arms poor dumb ******* die for his country." | Human O-Ring Society - General George S. Patton, Jr |
#13
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T,D&E
Kevin Willoughby wrote:
No, I really meant McDivitt and Young. There were wifferdills on both Gemini IV and Gemini X. GT10's wifferdill was the result of a bad guidance load. D. -- The STS-107 Columbia Loss FAQ can be found at the following URLs: Text-Only Version: http://www.io.com/~o_m/columbia_loss_faq.html Enhanced HTML Version: http://www.io.com/~o_m/columbia_loss_faq_x.html Corrections, comments, and additions should be e-mailed to , as well as posted to sci.space.history and sci.space.shuttle for discussion. |
#14
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T,D&E
In article ,
Henry Spencer wrote: In article , Doug... wrote: ... after all, GT-IV was separated (IIRC) from the Titan second stage at about the same velocity as the CSM was separated from the S-IVB, and they were supposed to do pretty much the same thing that Apollo crews did... While it's hard to find numerical details on Gemini, the best picture I can put together at the moment has Gemini 4 separating at 3m/s (vs. a nominal 0.3m/s for Apollo 9) and starting maneuvering at about 200m (vs. Apollo 9 nominally turning and halting separation at 15m). That is, they went out an order of magnitude farther and faster. Big difference. Still, it seems to me that the real rule of thumb should be that "The counter-intuitive effects of orbital dynamics are largely absent when the whole maneuver takes only a small fraction of an orbit". That is, although increased range increases the weirdness, increased speed decreases the weirdness. If Gemini 4 had separated, moved out to 200m, then instead of trying to rendezvous with their target, pulled out a rifle and fired at it, they wouldn't have had to adjust their aim much (if at all) for orbital-dynamic factors, since the travel of the bullet between the two spacecraft would have occurred so quickly that, to a very good approximation, both the spacecraft and the bullet would have been moving in a constant, uniform gravitational field, in which ordinary notions of dynamics would apply. On the other hand, when one thrusts a tiny amount "forward" (starting from a circular orbit), then waits until the orbit has traveled 90 degrees around the Earth, the direction of that "forward" thrust will, in the new reference frame, be "up", not "forward". And that is only the beginning of the complexity; when you are farther up, the gravity is less, so the orbit is slower, and you fall behind. -- Norman Yarvin |
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