orbital plane question

Status
Not open for further replies.
R

radarredux

Guest
Exposing my ignorance, I have several [I think] related questions.<br /><br />Shuttle Guy mentioned that being able to launch the shuttle at night (an issue with the CAIB) would increase the probability of completing the ISS "on time" (i.e., 2010 -- or pretty close to that).<br /><br />I have also read where the shuttle has certain windows when they can launch to rendezvous with ISS. For example, it might be 3 weeks in October, and then the next window not opening until December (dates made up for illustration purposes).<br /><br />Are these windows of time associated with the orbital plane of the ISS?<br /><br />If the US had launch assets on or near the equator that would allow us to put something in an orbital plane along the equator, would this significantly open up the launch window opportunities?<br /><br />Is there a chart on the web that shows the launch windows for the shuttle to the ISS?<br /><br />Thanks
 
N

najab

Guest
The optimum launch instant for a Shuttle going to the ISS is when the plane of the ISS's orbit passes directly over the launch site. This happens at least once every day (I think). The launch window that the program has chosen is five minutes either side of that optimum instant - the Shuttle could probably reach the ISS for a few more mintues outside of that launch window, but the additional burns would eat into the margins that they like to keep in reserve.<p>If that was the only consideration, then we could launch to the ISS any day. However, there are periods when we cannot launch the Shuttle to the ISS due to beta-angle cutouts. Basically these are periods when a docked Shuttle would interfere with power generation from the solar arrays. As I understand it, the beta-angle (angle of the arrays to the sun) would be too great since the docked station has to fly in a fixed attitude (Shuttle heatshield forward) while the orbiter is docked. The Solar arrays can only be tilted so far - so there are periods when the Station cannot generate enough power with a Shuttle docked. So we're already down from daily oportunities to daily oportunities during limited periods.<p>Added to this is the post-Columbia requirement for daylight during ascent. It would be bad enough if the requirement was only for daylight over KSC - since the daily launch opportunity shifts by about 1/2 an hour every day - but the requirement is for daylight for the entire ascent <b>and for ET sep</b> ! This means that it has to be daylight from KSC all the way around to just East of Europe. A look at the map shows that the ET sep region is about 4 time zones from the US. So in other words it cannot be late afternoon at KSC or it will be dark by the time they get to ET sep.<p>So, the available launch windows exist when (a) the ISS orbit plane is directly overhead, (b) the ISS is not in beta-angle cutoff and (c) it's mid-morning to early afternoon. The result is that the launch windows are <b>very</b> limi</p></p></p>
 
R

radarredux

Guest
> <i><font color="yellow">I read this line as if the question was: "if the NEXT ISS was in a zero inclination orbit, would it be easier to reach from the Equator."</font>/i><br /><br />Yes and no. On the "yes side" I was thinking of "What would Bigelow do?" for a launch site and orbital plane for his inflatable orbital facilities.<br /><br />On the "no side" I was thinking of a modular lunar or mars mission where at least one docking or maybe some limited assembly in orbit is needed. If element 1 (e.g., a space tug with additional supplies) was launched, and then only once it achieved orbit and checked out cleanly would element 2 (e.g., a crew-based CEV vehicle) be launched to dock with the tug.<br /><br />How much of an effect does an orbital plane have to do with a good cislunar excursion?</i>
 
Status
Not open for further replies.

ASK THE COMMUNITY

Latest posts