In article ,
Josh Gigantino wrote:
I seemed to remeber having read that they were looking to modify the shuttle
to fly unmanned. Is this really a possibililty?
It is not impossible in principle, but a lot of detail changes would be
needed...

In your opinion, would it be simpler to modify a Shuttle for robotic
flight, or make a new type of upper stage capable of delivering the
modules via ELV?

I was thinking just of plain shuttle flights, not considering the ISS
angle. If by "robotic flight" you mean ISS visits and module drop-off,
that gets you into nasty complications like the US's lack of an automated
docking system, and the need to teleoperate the arm.

Either one's going to be a big job. My gut feeling is that neither is an
obvious winner, in vehicle terms. Starting with the shuttle means you
don't have to build certain subsystems from scratch, but you have to
modify the controls, and you're subject to the shuttle's constraints --
one of which is that the three remaining flightworthy orbiters are
irreplaceable assets which must not be endangered.

(In a rational world, unmanned shuttle operations make no sense -- the
orbiters are far more valuable than the crews, so it makes sense to have
at least a couple of pilots on board, just because they might save the
orbiter if the automation screws up. Cargo aircraft always have pilots.)

As JRF noted, it's very awkward to fit a new launcher into the assembly
plans now, since the modules waiting to fly are built for shuttle launch.
I think that's the deciding factor. If you absolutely insist on unmanned
delivery, modifying an orbiter is the right thing to do, painful though
it is.

Also, what are your thoughts on orbital rendevous with a separate tug,
per Jorge's post?

In general, it makes all kinds of sense to base a tug at the station, and
send it down to haul cargo shipments (and even crews) up from a lower
orbit. Even given the need to bring up fuel for the tug, it's a sizable
net win, especially with reusable or semi-reusable launchers where the
orbiter much outweighs the payload.

However, this isn't something you can easily retrofit into ISS now, not
least because of the lack of a suitable tug.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |