Questions about STS ascent and descent

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rfoshaug

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I've got a couple of questions about the ascent and descent phases of space shuttle missions. I've been trying to fly some shuttle missions in Orbiter (www.orbitersim.com - excellent sim BTW) and want to do it as realistically as possible.<br /><br />1. For a mission to ISS, the ascent phase must of course be timed so that the orbital plane of ISS passes over the launch site at the time of launch (or probably a few seconds/minutes before launch to give the shuttle some time to accelerate - but how much?). But once the shuttle is in orbit, there's bound to be some deviation between shuttle orbit and ISS orbit. This deviation must be compensated for by orbital plane adjustments using the OMS engines. I'm quite satisfied if I get below 1 degree difference between my orbit and that of the ISS. How large a deviation is normal in real shuttle operations?<br /><br />2. When, or more specifically, where does the de-orbit burn start? How many miles/kilometers from the landing site? For example for a return to KSC from the orbital plane of ISS - where does the burn start?<br /><br /><br />3. What is the altitude at the point of the de-orbit burn? I usually place the orbiter in a 200-to-250-kilometer circular orbit before the de-orbit burn instead of de-orbiting directly from ISS altitude. Is this how it's done on the real orbiters?<br /><br /><br />4. How long is the burn? I read somewhere 2.5 minutes, but what determines the length of the burn and the delta-v? Is it to place the calculated impact point (assuming no atmosphere and assuming that the perigee of the orbit is placed below the surface) at a specific place, or is it to place the perigee at a specific altitude?<br /><br /><br />5. How much (percentage) OMS fuel is usually in the tanks at various flight stages such as ISS docking, start of de-orbit burn and after landing?<br /><br /><br />If anyone knows this stuff, any answers would be highly appreciated. <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#ff9900">----------------------------------</font></p><p><font color="#ff9900">My minds have many opinions</font></p> </div>
 
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