Date: Tue, 24 Jun 1997 11:44:13 -0700 (PDT) From: "Brian N. Handy" <handy@sag.space.lockheed.com> To: "Jonathan M. Bresler" <jmb@FreeBSD.ORG> Cc: chat@hub.freebsd.org Subject: Re: BSD io Message-ID: <Pine.OSF.3.96.970624113727.22856c-100000@sag.space.lockheed.com> In-Reply-To: <199706241733.KAA26618@hub.freebsd.org>
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On Tue, 24 Jun 1997, Jonathan M. Bresler wrote: > why do spacecraft rotate ~180 degrees during take-off? > the shuttle shows this clearly, i have been told all > rockets do it, but the cylindrical symmetry of the others > obscure the motion (unless you watch the printing) I spoke with our local shuttle expert -- a guy who used to work on the shuttle teams doing life support. (He worked the '85 Challenger mission, incidentally...) Anyway, the deal with the space shuttle is it takes off, then rotates so that the big external tank is on top and the shuttle itself is underneath. The explanation they gave for that was aerodynamic loading, which is to say, less drag on the whole system as it heads for orbit. Now the interesting part is this: if they had a problem and had to do what's known as an "abort to orbit", they have to turn the thing around and come in and land. But they're still upside down and they still have this giant tank attached. So, with whatever problem they have, they have to nose the shuttle back over the top (so the astronauts, upside down, are now pulling negative G's), level off, ditch the external tank and then glide back into Kennedy, for example. You'll guess correctly that launch control always let a big sigh of relief when they were able to ditch the external tank as part of SOP. I'm not sure what's up with other rockets, since in general they are pretty symmetric. It may be to get the fins in the right orientation for the best control as they head for orbit. But I don't really know. My expertise is actually more in designing telescopes and such, not so much rockets and missiles and stuff. Some of my co-workers worked on the Hubble telescope and now we're building some neat solar telescopes. The one that my PhD is partly based on may get launched in December. (URL below.) Happy trails, Brian -- (http://www.space.lockheed.com/TRACE)
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