ROD%SU-AI@sri-unix.UUCP (02/13/84)
From: Rod Brooks <ROD@SU-AI>
a208 1017 12 Feb 84
AM-Shuttle-Satellites, Bjt,650
Rescuing Failed Satellites Possible, But Maybe Not Feasible
By PAUL RECER
AP Aerospace Writer
SPACE CENTER, Houston (AP) - NASA could use the shuttle in an
attempt to salvage the two $75 million communications satellites now
drifting in useless orbits about the Earth, but the difficulty and
expense might outweigh the benefits, experts say.
The Westar VI and Palapa-B satellites - owned respectively by
Western Union and the government of Indonesia - failed to reach their
designated 22,300-mile-high orbits after they were launched from the
shuttle Challenger on the flight that ended Saturday.
Officials at Hughes Aircraft Co., which made the satellites, said in
both cases rocket boosters snuffed out early, stranding the
satellites in lopsided orbits that bring them as close as 165 miles to
Earth at times, and as far as 650 miles at others.
Data from the craft indicate they are healthy and could function
normally if they were in the high orbit. But neither has enough
remaining rocket power to be nudged to the proper elevation, although
NASA did just that with a Tracking and Data Relay Satellite that went
astray after launch last year.
At a post-landing briefing Saturday, shuttle director Lt. Gen. James
A. Abrahamson called the idea of using the orbiter to rescue the
satellites ''an exciting prospect to think about.''
''If they (the owners or insurers) ask us to look into it, then
we'll begin to do more serious planning,'' he said.
The shuttle is already planning to rescue a satellite in April, but
that assignment poses far less difficult problems.
On that mission, Challenger will rendezvous in low orbit with the
Solar Maximum, a science satellite that stopped working because of an
electrical problem. Astronauts using a jet-pack and a robot arm will
bring the Solar Max into the cargo bay for repairs and then release
it back into orbit.
Such a rescue is possible on Solar Max because - unlike the
communications satellites - it is in a low orbit and was designed to
be snared by the shuttle if necessary.
Before salvage of the communications satellites could start,
scientists would have to bring them to a lower orbit within the
shuttle's range, by firing rocket thrusters on board the craft.
The shuttle, by special thrusting at launch, can reach an orbit of
about 260 miles - as it will on the April flight.
''If the satellite was brought down to an orbit of 260 miles or so,
it would be theoretically possible,'' said Dick Young, chief of the
flight planning branch at the Johnson Space Center.
But even if the satellites were within rendezvous range of the
shuttle, there would be significant hardware problems.
Both satellites are spinning at about 50 rpm, a twisting motion that
keeps them stable but is far too fast for safe approach. There are
rockets on board designed to stop the spin, but these might be
expended in lowering the orbit, according to Bill Ziegler, a Westar
expert with Western Union.
Terry Neal, a Johnson flight crew equipment expert who helped plan
the April mission, said that even if the spin could be stopped, there
would still be the problem of grabbing and holding the satellites.
''It would take some modifications to the orbiter (shuttle
spacecraft),'' said Neal. ''And there would have to be some sort of
grapple device attached to the satellites.''
Once such a device is attached to the satellite, the shuttle robot
arm could grasp the craft and bring it into the cargo bay. Then, said
Neal, there would have to be some sort of ''cradle'' to hold the
satellite securely in the cargo bay.
If the satellite could be secured in the cargo bay, said Neal, it
could be brought to Earth for repairs.
All this would be expensive for the satellite owners. Total cost of
a launch now runs to an estimated $250 million.
Ziegler said salvaging Westar ''probably wouldn't make economic
sense at all,'' but, he added, it ''would certainly be fun.''
ap-ny-02-12 1316EDT
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