Re: Hubble man vs robot repair

From: Jorge R. Frank (jrfrank_at_ibm-pc.borg)
Date: 08/14/04 

Date: Sat, 14 Aug 2004 13:17:19 -0500

Brian Thorn <bthorn64@cox.net> wrote in
news:10jsh0lmida335st09cd70uae3egf3k4u6@4ax.com:

> On Sat, 14 Aug 2004 00:11:17 -0500, "Jorge R. Frank"
><jrfrank@ibm-pc.borg> wrote:
>
>
>>> A lot less. Exactly how much depends on the Shuttle's budget and
>>> number of flights in the budget year. Probably $500-600 million.
>>
>>Hmm, that's annual program cost. The marginal cost is quite a bit
>>lower, and that's the proper figure of merit for comparing the cost of
>>adding a single mission in a given year. Especially considering that
>>the payloads are already built and paid for.
>
> But that's being somewhat deceptive.

No, it's not. If you add an HST robotic servicing mission, NASA's budget
has to go up by $1-1.6 billion. If you add an HST shuttle servicing
mission, NASA's budget only has to go up by $100-200 million. That's the
*definition* of "marginal cost". In this case, it is deceptive if you
*don't* use marginal cost.

> I suspect the ISS team would be
> pretty pissed that you get a Shuttle mission for $100 million while
> they have to fork out $500 million for each of their's.

The ISS program has *never* had to pay for shuttle flights. Neither has any
other internal NASA customer. GSFC has never shelled out a dime for SPARTAN
flights, or TDRS flights, for example. It's all bookkept within the shuttle
budget.

> A far saner
> idea is to divide the total cost of the program that year against the
> number of flights you make that year. If you add a flight, that extra
> $100 million gets tacked on to the total and the new annual figure is
> divided into the new total number of flights.

I consider that more deceptive, because it implies that adding an HST
shuttle servicing mission requires that $500-600 million be added to NASA's
budget. It doesn't. It requires an additional $100-200 million. That fact
that the amortized cost of the other shuttle flights goes down in that
particular fiscal year is an internal bookkeeping matter - from a public
policy point of view, all that matters is how much the *total* goes up or
down.

>>> The problem is, they probably aren't possible at any cost.
>>
>>Hmm, I'd dispute that, too. The only CAIB recommendation that applies
>>to an HST mission, but not to an ISS mission, is standalone
>>inspection/repair capability.
>
> Which is my point. I don't think standalone repair capability will
> ever exist for 107-class damage.

I don't think it *needs* to exist for 107-class damage. The CAIB
recommendation specified "widest possible" range of damage. Absent context,
that could mean almost anything, but Adm. Gehman has provided two
statements of clarification since then.

One statement (sorry, don't have the exact text handy) was to the effect of
"If you allow big pieces of foam to fall off the tank, you have to be able
to repair big holes. But if you mitigate the foam shedding such that all
that comes off are itty bitty pieces of foam, you only have to be able to
repair itty bitty holes."

The second statement, given when Gehman responded to O'Keefe's request for
an independent opinion on HST servicing, made clear that the CAIB does not
expect standalone repair capability to match what is possible at ISS. It
was basically, "do the best you can."

> NASA's fallback position is safe
> haven on ISS. Only they don't want to come right out and say "we can't
> fix the Orbiter in orbit, so we'll just have to keep the crew alive
> until rescue." Instead, they're avoiding the issue by not flying the
> Shuttle anywhere but ISS and hoping the Powers That Be don't ask too
> many questions.

I agree, especially the last sentence, only that what they don't want to
come out and say is really, "we can fix the Orbiter in orbit, but we have
very little confidence the repair will hold up through entry, and we think
the crew has better odds waiting for rescue."

>>> Why a Rescue Shuttle isn't being considered for the one remaining
>>> HST mission, I have no idea. Yes, it would be a scheduling problem,
>>> but isn't HST worth a half-year (if even that) pause in ISS
>>> launches?
>>
>>You've got that almost exactly backwards. A rescue shuttle was not a
>>CAIB recommendation (and quite deliberately so), but NASA considers it
>>a requirement for an HST mission.
>
> Well, no, NASA has ruled out a Shuttle mission to HST, so by default
> NASA is *not* considering a standby Shuttle mission.

OK, we're talking past each other. NASA considers a rescue shuttle a
requirement for an HST mission. For that reason (among others), NASA does
not want to do an HST mission. 

-- 
JRF
Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

Relevant Pages

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