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Subject: SPACE Digest V12 #85

SPACE Digest                                      Volume 12 : Issue 85

Today's Topics:
              Re: Multiple probes (long)
              Re: Nasa's budget
        Re: Is an asteroid capture possible/feasible?

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Date: Mon, 16 Jul 90 18:14:49 EDT
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Re: Multiple probes (long)


>From: mojo![e-mail]  (Doug Mohney)
>Subject: Re: Multiple probes

[somewhat edited]
>>>Maybe it's time to start rethinking our whole policy of space exploration.
>>>Back in the "Old Days" we would build two or three of everything just in
>>>case. Now, we come up with one and if it fails...
>>If Galileo fails, we concentrate on Venus, Mars, and Saturn. If Magellan
>>fails, we concentrate on Mars, Jupiter, and Saturn. The planets don't seem
>>to be going away anytime soon.
>Naw, we just throw away money on a failed attempt the first time 'round.
>And would you like to be a planetary scientist who's put in 7-10 years
>of your life riding on one probe which croaks on a faulty chip?

If the first attempt fails, you've thrown away money regardless of the approach.
Sending a second specialized probe *right then* to an object that's going to
be there at least for millions of years is a political ploy to make sure you
get at least *some* results from the project, so it doesn't look as though you
got skunked as badly as you did. (Unless, as I said, there's some specific
time limit for the mission.) In order to obtain this political insurance, you
either commit two less capable probes, or spend a batch more money on the
project than you would have making just one probe. (Does anybody have a
good guess for the relative cost of a typical second probe? How about storage
costs?)

>>While building a second probe for a specific
>>mission may be cheaper than building the first one, you still may have
>>decreasing marginal scientific returns for your dollar. Making duplicates
>>on a fixed budget may force compromises in quality or ability of each probe.
>Duplicates are NOT bad. Magellen is built out of leftovers, as I seem to
>recall. If the probe dies or finds something VERY interesting, you send in
>probe #2, with modified parameters to do a more detailed survey.

Your point about specific scientists being disappointed is valid.
Keep in mind, however, that holding off launch of the second probe may well
have the same result. Spare hardware is also politically troublesome - people
think their money's been wasted, as in many cases it has. Hardly a week goes
by without somebody on the net complaining about the hardware sitting around,
such as the spare Skylab. The implication is that if we bothered to build it,
we should launch it. If we do launch it, or even if we just build the spares,
costs for a specific set of mission objectives goes up. If the budget is
pretty much fixed, that means we have to cut down on the number of projects.
So, for instance, if we could improve the odds of a successful Galileo mission
by 30% but the additional expenditures would force us to forget Venus, Mars,
and Saturn for the next 20 years (as an extreme example) would the sacrifice
be worth it?

>>...it may make the most economic sense to allocate only one for each mission.
>You still miss the cost of being screwed if your single probe dies.
See above.

>>Multiple probes for one mission might be defended as *political* insurance.
>... B) You launch one and see what happens. Number #2 stays on the ground
>and in a clean room until you see what happens with #1.
How much did HST cost per year to store?

Some additional points:

 - If you use all-new custom hardware for each mission, and build spares, it's
   virtually guaranteed that a lot of it will never be used.

 - Suppose you build a Galileo probe and launch it for $1.5 billion, and get
   a bargain-basement rate on a second probe at only $500 million. Now suppose
   you launch the first probe, and it fails after five years due to an
   unforseen design defect. Now you have to find some way to fix the second
   probe and send it, even though it was built with 1970's technology and is
   known to have several problems. You can't weasel out of it and get a nice
   new probe because you have so much money invested in the spare. If you're
   lucky, you do save a couple of years on the time a new design would take.

 - Now look at an alternative, which I mentioned in the previous posting, and
   which Henry Spencer and others have described. Instead of highly specialized
   custom design jobs for each project, you develop a general-purpose probe,
   configured so that it can be upgraded, and specialized instruments and other
   equipment can be attached. Instead of storing these probes for years, you
   launch them as they are completed and as missions come up. If a previous
   mission fails, you just grab a fresh probe with all the latest features from
   production, attach specialized equipment (which can be stockpiled) as
   needed, and launch it. Since the general-purpose probes are (relatively
   speaking) mass-produced, it is likely that the cost per probe would drop
   substantially.
         John Roberts
         [e-mail]

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Date: 14 Jul 90 05:06:42 GMT
From: usc!elroy.jpl.nasa.gov!zardoz.cpd.com!dhw68k!ofa123![e-mail]  (Mark Perew)
Subject: Re: Nasa's budget



>>And, if the shuttle is so expensive why are Saenger and Hermes being
>>built and why did Glavkosmos build Buran?

>There is nothing wrong with the Shuttle concept. Had they used
>available technology instead of pushing the envelope everywhere;
>The shuttle was premature.
>At any rate, it doesn't matter what others do.

So the shuttle was premature then, but not now.  OK, if we hadn't built
the shuttle then how would anyone have the technology to do it now?
But you keep comparing NASA vs. Arianespace and KSC vs. Kourou.  Seems
to me that what others do is an important part of your position.

>>>As to Freedom, that program is totally out of control....
>>It would help if our Congresscritters would decide once and for all
>>just how much money we will spend on this and leave it alone.
>That is a factor but not a major one. ... They made every project
>use it just so funding would be protected. It 'worked' for the shuttle
>(much to our shame) but it isn't working for Freedom.

Seems to me that you just proved my point.  Congress wouldn't give a
funding commitment so NASA had to oversell the project.  If Congress
had given the space station the funding it needed when it needed it
then NASA would not have needed to resort to politcal games to get the
money the project needs.


--
Mark Perew
Internet: [e-mail]
BBS:      714 544-0934   2400/1200/300

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Date: 16 Jul 90 11:33:28 GMT
From: mcsun!unido!rwthinf![e-mail]  (Dieter Kreuer)
Subject: Re: Is an asteroid capture possible/feasible?

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
> In article <[e-mail]> [e-mail] writes:
> >    This may have been asked before, but have there ever been any
> >studies or projections on the resources needed to do an asteroid capture? I
> >have wondered what might be required to place a small asteroid in a stable
> >Earth orbit...
>
> The main problem is that even a small asteroid is an enormous mass by the
> standards of current space propulsion.  Chemical fuels just can't do
> this job at all.  You can do it with nuclear pulse propulsion -- that is,
> using lots of large hydrogen bombs as your energy source -- or with a
> solar-powered mass-driver mining the asteroid itself for fuel (and taking
> a long time).  Neither of these propulsion systems is off-the-shelf
> technology at the moment, although both could be made practical in fairly
> short order if enough money was available.

There has been a fairly long discussion about nuking earthbound asteroids
in sci.astro recently. While I totally agree to try everything to move
such a dinosaur-killer in any other direction than towards Earth, I would
strongly refuse to bring such a thing intentionally close to our planet.
If something went wrong (perhaps they calculate the wrong specs; yes,
such things sometimes happen...), the laws of Murphy will probably direct
the rock straight towards collision with Earth (KSC will be the most probable
impact point). As long as the risks of space exploration (and exploitation>
are restricted to those people directly involved in the concerning projects,
they may be acceptable, but if other people or even the whole world is in
danger, they are absolutely not. If you want to exploit asteroids, go there.
Or, dig into the ground of the moon.
Remember, we've only got one Earth...

(No flames please, I am not an environmentalist, but I love my life)

-------------------------------------------------------------------------------
     Dieter Kreuer, Lehstuhl Informatik IV, RWTH Aachen, D-5100 Aachen
          [e-mail] = [e-mail]
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End of SPACE Digest V12 #85
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