 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| HomeDiscussion GroupsSpace ScienceAstronomyAmateur AstronomySpace FlightSpace StationShuttleSpace HistorySpace PolicySETI SpaceKB.com Contact UsLink To UsSearch & Site Map |
Space Forum / Shuttle / December 2007NASA: Space Station "moves away" from shuttle after undocking
NASA: Space Station "moves away" from shuttle after undocking The page below has a cool image of the ISS with the boot of Italy and the west coast of Greece in the background -- classical human historical sites with 'classical' and easily recognizable shorelines. But instead of identifying the region, the caption suggested that after undocking with STS-118, the space station "moved away" from the shuttle. Call me geocentric, or even target-centric, but in MY day in the trench, it was usually the shuttle that moved away from passive targets. I guess it's all relative. http://www.nasa.gov/mission_pages/station/main/index.html http://www.nasa.gov/images/content/164461main_s118e09467.jpg Image above: Backdropped by Earth's horizon and the blackness of space, the International Space Station appears to be very small as it moves away from Space Shuttle Endeavour. Earlier the STS-118 and Expedition 15 crews concluded nearly nine days of cooperative work onboard the shuttle and station. Image credit: NASA > NASA: Space Station "moves away" from shuttle after undocking > [quoted text clipped - 6 lines] > usually the shuttle that moved away from passive targets. I guess it's all > relative. Actually, both vehicles get a nudge to their inertial state vectors at undocking due to the spring plungers in the docking mechanism. Early in the ISS assembly sequence, ISS was less massive than the orbiter so it received most of the momentum change from the pushoff. The tipping point was, I think, flight 98/5A in 2001 - the orbiter was more massive than the station at docking, but after US lab installation ISS was more massive at undocking. Since then the majority of the spring pushoff has gone into the orbiter state, but the change in the station state is still detectable to the FDOs/TOPOs. And of course, the orbiter crew performs RCS firings after undocking that cause much larger changes in the orbiter state. But yeah - from the viewpoint of either crew, it's all relative. >From Jorge: <snip> > ISS was less massive than the orbiter so it > received most of the momentum change from the pushoff. Sir Isaac would beg to differ with that statement! ~ CT > >From Jorge: > <snip> >> ISS was less massive than the orbiter so it >> received most of the momentum change from the pushoff. > > Sir Isaac would beg to differ with that statement! You are correct. The momentum change is the same, but the delta velociy is different. Danny Deger > ~ CT >> >From Jorge: >> <snip> [quoted text clipped - 5 lines] > You are correct. The momentum change is the same, but the delta velociy > is different. Well, to beat this one to death... The momentum change would be equal *magnitude* and opposite direction. Momentum is a vector quantity, p=mv, where p and v are vectors. If the shuttle and ISS spring apart, you would have p_s == -p_iss. Or m_s * v_s = - m_iss * v_iss Since m_s and m_iss are positive quantities, v_s and v_iss will be opposite direction values. Further, if m_iss > m_s, then |v_iss| < |v_s| This all assumes a reference frame where p_s + p_iss == 0. High school physics? - -- Steve Williams "The woods are lovely, dark and deep. steve at icarus.com But I have promises to keep, http://www.icarus.com and lines to code before I sleep, http://www.picturel.com And lines to code before I sleep." > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 [quoted text clipped - 13 lines] > Momentum is a vector quantity, p=mv, where p and v are vectors. If > the shuttle and ISS spring apart, you would have p_s == -p_iss. Or Oops, yes. Fingers typed faster than brain. Momentum change equal and opposite, velocity change larger for ISS (at that time). But I agree with Jim's original point about Prox Ops. The station is the target. No matter what it is doing, the thing that counts is your relative movements around it. ...kinda like flying a rejoin in T-38s. No matter what lead is doing, it is up to the wingman to get into the proper position relative to lead. If lead drags a wingman, then the wingie is moving away from lead, irrespective of the fact that both jets are flying forward and that lead is flying faster than 2. That is the operator's perspective. The only one that counts for preventing collisions and stuff like that. Relativity in action! ~ CT > But I agree with Jim's original point about Prox Ops. The station is > the target. No matter what it is doing, the thing that counts is your [quoted text clipped - 10 lines] > > ~ CT For The atheists here, you are in for a surprise http://www.godtube.com/view_video.php?viewkey=8f1da580cbfd9b0fecd3 |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.