Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!floyd!harpo!seismo!hao!hplabs!sri-unix!weems%umass-cs@CSNet-Relay From: weems%umass-cs%CSNet-Relay@sri-unix.UUCP Newsgroups: net.space Subject: Grabbing Lost Satellites Message-ID: <16589@sri-arpa.UUCP> Date: Thu, 9-Feb-84 22:14:00 EST Article-I.D.: sri-arpa.16589 Posted: Thu Feb 9 22:14:00 1984 Date-Received: Sat, 11-Feb-84 10:06:33 EST Lines: 43 From: Charles WeemsIt's not as simple as just grabbing them any old place you can get ahold of them and pulling them back into the payload bay of the shuttle. The satellites are purposely spun up to a fairly high rotation rate (I saw the figure 50 RPM quoted in one article). The problem is that you must grab onto them at a point on the spin axis and gradually slow them down before they can be brought into the bay. A sudden stop would destroy the satellite. This requires that there be something to grab onto at only one of two points. One of those points is at the "top" of the satellite where antennas and such are deployed. Grabbing onto something here would probably do a great deal of damage. On the other end is the point that the PAM connects -- but nobody knows for sure now just what is there. Mangled booster pieces? Another problem is that most of these satellites are programmed to fully deploy antennas and booms and such some fixed time after the burn. This way even if things don't quite go right (an understatement in this case) the satellite can start transmitting and trying to pick up corrective orders from the ground. How much volume does a fully deployed communications satellite take up? Can it fit back into the shuttle without "breaking pieces off"? If not, it will have to be brought home for repairs, thus requiring a total of three shuttle launches to get it into orbit (not to mention the cost of all of the repairs, testing, reconfiguring for launch and strapping on another PAM). Then there is the problem of getting the shuttle into the "difficult" orbits that the satellites are in -- and it really must be able to match the orbit closely because the time required to hook on and spin down will probably be several orbital periods long. All in all, it's easier to collect the insurance. A note on Solar Max -- it is also true that Solar Max is spinning like Westar and Palapa-B. Solar Max, however, was DESIGNED to be serviced by the shuttle. It was known that it would be in an orbit reachable by the shuttle and in an uncharacteristic fit of forethought its designers built a special adapter into one end of it that will allow the suttle to grab on easily and spin it down for service (and back up for redeployment). Because these communications satellites were intended to operate at geosynchronous orbit, beyond the range of the shuttle, it was considered a waste of weight to put shuttle servicing adapters on them just in case something unlikely (such as what happened) occurred. We all have 20-20 hindsight now. chip weems