"Jorge R. Frank" wrote ...
As far as the ion propulsion goes, the basic concepts were proven with
DS1,
but that was a smaller beast than HST. To transfer HST to ISS inclination
in a reasonable time (on the order of months rather than years), you'd
need
a larger engine than has been successfully developed so far. Some
development cost but no show-stoppers that I can see.

The concept as I imagined it was several DS1 class bolted together, or even
an array of lesser thrusters. The idea is based upon an article that gave a
transition time of about 18 months.

The biggest development headache may well be automated rendezvous and
capture of HST. All the automated systems developed to date require their
targets to be cooperative to some degree (i.e. equipped with navaids for
the chaser vehicle). The Russian Kurs system requires a rather elaborate
set of RF antennas/avionics on the target vehicle. The systems under
development for ATV and HTV require the target vehicle to have a GPS
receiver and an array of laser retroreflectors.

It's as much of a problem as you make it. If you can park the hubble within
a few hundred meters from the ISS you can effectively attach a line and real
it in. Even if this is impractical, get it close enough in terms of
deltaV and the shuttle could grab it and then rondavouz with the ISS in
'perfect' safety.

The easiest way to dock the OTV to the ISS would be to give it a false
docking hatch. That way it can be attached to any number of hard-points.

Trouble is, HST has *none* of those things - it's a completely passive
target, save the (visual) aids on its RMS grapple fixtures and berthing
mechanism. Attaching the navaids to HST becomes a chicken-and-egg
problem -
any automated system that could attach the navaids to HST needs the
navaids
to be already there in order to get there in the first place.

Call me simplistic, but what's wrong with putting the OTV near the hubble,
pointing the two at each other manually and then pressing the 'go forward'
button? Add a few dozen 100gram cameras to make sure everything's perfectly
lined up and hen press the 'dock' button.

Besides, the base of the hubble is one big circle with the docking mechanism
in the middle. You can't really get a better bulls eye. By measuring the
apparent size of the circle 'on screen' you can tell how far away it is,
it's closing speed, how far off axis it is and in what direction that off
axis is. Measuring the shape of the circle tells you if the hubble is going
off axis by measuring circle/eclipse

That is not to say that it's impossible to develop an automated system to
rendezvous and capture a non-cooperative, inert, and (by 2007-08) possibly
slowly tumbling target. But the challenge of developing such a system
will,
IMO, be greater than that of getting the ion propulsion to work.

Whatever docking systems required for hubble needs to be developed anyway
for the derbit module. Unless of course NASA wants to harpoon it and 'tow'
it out of orbit. Which would actually kind of work...

John