Probably Stupid Idea for Saving Hubble

John Penta wrote:

It's been proposed. It's not an easy mission, because the orbits are
quite different; this is *much* harder than de-orbiting Hubble. With
chemical fuels it's impractical, but with ion propulsion -- now more or
less an off-the-shelf item -- it actually could be done, although it
would take a while.


How is ion propulsion an off-the-shelf item?

I haven't heard of its being used in LEO satellites, for one, only
deep space probes...

It's been used on Hughes (now Boeing) 702 comsats for a while. There
have been some reliability issues with them (and sputtering problems),
but they're an operational technology.

In article ,
Andrew Nowicki wrote:
... but with ion propulsion -- now more or less an off-the-shelf item
-- it actually could be done, although it would take a while...

It would take about one year to haul the Hubble to
the ISS orbit by a small, economical ion thruster...

Uh, no -- you need a battery of sizable ion thrusters and some very large
solar arrays to get it there in reasonable time. Ion thrusters have some
nice capabilities but they are not magic, and Hubble is big and heavy.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

In article ,
John Penta wrote:
How is ion propulsion an off-the-shelf item?
I haven't heard of its being used in LEO satellites, for one, only
deep space probes...

To date, only a few experimental deep-space probes have used it as
*primary propulsion*. But it's in commercial use for stationkeeping
propulsion on geostationary comsats. (And the "no primary propulsion"
part has to come with some caveats, now, because some of those have used
their ion thrusters to help with orbit insertion.)
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

On Sun, 15 Aug 2004 21:51:38 GMT, Rand Simberg
wrote:


It's been used on Hughes (now Boeing) 702 comsats for a while. There
have been some reliability issues with them (and sputtering problems),
but they're an operational technology.

Ya learn things every day.:-)

Thanks, Rand.:-)

HAESSIG Frédéric Pierre Tamatoa wrote:

It's also not worthwhile to launch a robot mission solely for the purpose
of deorbiting the telescope.


Why? If the purpose is controled deorbitation, as opposed as a risk of
crashing it on NYC?

The risk of HST crashing on NYC is zero.

The risk of HST crashing somewhere and killing someone is about .001.
It's idiotic public policy to spend (say) $100 M to prevent 1/1000th
of a death.

Paul

Rand Simberg wrote:

If we're going to continue to fly Shuttle at all, it makes as much sense
to use it for Hubble as anything else.

This is called 'damning with faint praise'.

Paul

Paul F. Dietz wrote:

If we're going to continue to fly Shuttle at all, it makes as much
sense to use it for Hubble as anything else.

This is called 'damning with faint praise'.

Indeed.

(Royalties to Instapundit)

Paul F. Dietz wrote:

The risk of HST crashing somewhere and killing someone is about .001.

Do you have a cite for that number? I'd be amazed if it was that high.

I once calculated that the normal chance of killing someone from an
uncontrolled reentry is roughly 100,000:1 IRC- annoyingly high, but not
devastatingly so.

Paul

Ian Woollard wrote:
Paul F. Dietz wrote:

The risk of HST crashing somewhere and killing someone is about .001.


Do you have a cite for that number? I'd be amazed if it was that high.

I once calculated that the normal chance of killing someone from an
uncontrolled reentry is roughly 100,000:1 IRC- annoyingly high, but not
devastatingly so.

Google finds some estimates quite quickly. Here

http://www.space.com/news/hubble_trmm_040209.html

is a report stating the risk of a human casualty is 1 in 700.
Granted, not all these are fatalities.

Remember, the reentering satellite breaks up into many objects,
some fraction of which can be dangerous.

Paul

Paul F. Dietz wrote:
Google finds some estimates quite quickly. Here

http://www.space.com/news/hubble_trmm_040209.html

is a report stating the risk of a human casualty is 1 in 700.
Granted, not all these are fatalities.

I don't absolutely know if this is the same model, but atleast one model
used for this is notoriously pessimistic, atleast from what I heard. I'd
be surprised if they had very many different models.

I vaguely recall hearing that the expected casualties from Columbia was
10 or something like that; although it is possible the model has been
updated in the light of experience I guess.

Paul