ZeeNL - 20/12/2006 2:05 AMOk, question: in the very unlikely event they can't get the orbiter down on one of the three landing sites on Friday, what will the plan be?
eeergo - 19/12/2006 6:06 PMWhile feeling wordlessly amazed by the images, I was thinking...How does this maneuver work? Still learning orbital mechanics... I figured that maybe they caused some extra velocity in the zenith direction by firing the thrusters, along with some velocity in the aft direction... and because of not having enough orbital velocity to achieve a higher orbit, they fall slowly again. Or do they continously fire the thrusters to control the maneuver? I didn't see any plume though... What I can't grasp is why the shuttle is always properly oriented with respect to their movement...Maybe this should go in the Q&A section, but it seemed on the point right now... however, feel free to change its place, Chris
ZeeNL - 19/12/2006 7:48 PMQuick question: Due to what force does the orbiter separate from the ISS? I imagine it can't be a spring force in the docking ring, because the docking port is not in line with the CG of the orbiter. Hmm, the commentator just said that it were indeed the springs Next question: it must induce a slight rotation then, at what distance from the ISS can they use the RCS system?
ZeeNL - 19/12/2006 9:05 PMI don't know if this is still the right place to ask this, but is the force of the RCS jets limited near the ISS and do they worry about the impact of RCS firings on the ISS?
ZeeNL - 19/12/2006 6:48 PMQuick question: Due to what force does the orbiter separate from the ISS? I imagine it can't be a spring force in the docking ring, because the docking port is not in line with the CG of the orbiter. Hmm, the commentator just said that it were indeed the springs Next question: it must induce a slight rotation then, at what distance from the ISS can they use the RCS system?
Jorge - 20/12/2006 3:59 AMQuoteZeeNL - 19/12/2006 6:48 PMQuick question: Due to what force does the orbiter separate from the ISS? I imagine it can't be a spring force in the docking ring, because the docking port is not in line with the CG of the orbiter. Hmm, the commentator just said that it were indeed the springs Next question: it must induce a slight rotation then, at what distance from the ISS can they use the RCS system?Right, the springs in the docking mechanism impart the initial opening rate, but also cause the orbiter to pitch nose-down. When the PLT sees out the aft window that the docking petals are clear, he punches a button allowing the digital autopilot (DAP) to control attitude, using RCS jets to null the pitch rate. For undocking, the DAP is configured to control pitch with the tail upfiring jets with a 10-second delay between firings to minimize plume impingement on ISS. This further increases the opening rate. The PLT then pulses the translational hand controller (THC) to increase the opening rate gradually, first to 0.15 fps, then to 0.2 fps. The PLT maintains 0.2 fps (or faster) until starting the flyaround.-- JRF
ZeeNL - 19/12/2006 8:29 PMThanks for your answer, Jim. I have found this information: "Depressing the low Z push button inhibits all up-firing jets in order to prevent plume damage to payloads or injury to extra-vehicular activity crew members. If a plus Z translation is requested, plus X and minus X jets are fired simultaneously, producing a downward translation because the X jets are oriented in such a way that they have small plus Z thrust components."
ZeeNL - 19/12/2006 9:05 PMDo they use the low Z switch in the early stage? And do they only use the vernier thrusters?
Jorge - 20/12/2006 4:22 AMQuoteZeeNL - 19/12/2006 9:05 PMDo they use the low Z switch in the early stage? And do they only use the vernier thrusters?I think I answered the first question in an earlier post... to answer the second, they use the primary thrusters initially for attitude control (there are no up-firing vernier jets), and select vernier jets one minute after separation.-- JRF
