Single-point failure
Philip Chien (kc4yer@amsat.org)
Tue, 27 Feb 1996 11:35:23 -0400
"Rob Matson" <Rob_Matson@cpqm.saic.com> said:
>On 2/26 Ray Talipsky wrote:
>> The momentum transfer gave the satellite an 80 foot per second
>> boost and shot it into a 324 x 171 nm orbit. NASA would not risk
>> putting a national asset and the astronaut lives in harms way to
>> retrieve an italian satellite!
well, they did risk national assets and astronaut lives unnecessarily to
retrive an Intelsat satellite, but that's besides the point.
>Assuming the Shuttle had the necessary fuel reserve (and I gotta believe an 80
>fps velocity change is well within the fuel margin)
you believe wrong. First the shuttle would need an 80 fps additional
margin to go running after the satellite. Then it would need additional
propellant for the rendezvous and stationkeeping ---- that's a *LOT* of
prop!
>there would have been no
>more risk to the Shuttle and its astronauts than for any of the prior
>satellite retrieval missions. That is, if it weren't for the tether.
True enough, but as I noted in another post, there is - and never was - any
pressing need to return the satellite. I talked with two of the NASA HQ
scientists before launch about the mission success criteria. The key task
was to get beyond 12 km. (which they did) and perform the science at
station 1 for at least ten hours (which they didn't). Nowhere in the
mission success criteria is returning the satellite mentioned! However, as
he put it, they would certainly be upset if they didn't return it since it
was one of the goals. So they didn't return it, and didn't accomplish all
of the goals. But retriving the satellite was never an absolute necessity.
>1. What are some of the events which could cause the tether to break? How
>likely are they?