Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v15_6/v15no616.txt

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Date: Thu, 31 Dec 92 05:19:54
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #616
To: Space Digest Readers
Precedence: bulk


Space Digest                Thu, 31 Dec 92       Volume 15 : Issue 616

Today's Topics:
                       Aluminum as rocket fuel?
                        averting doom (2 msgs)
Government-run programs  Was: Re: Justification for the Space Program (2 msgs)
         How many flights are Orbiters designed for? (2 msgs)
                 Justification for the Space Program
                          Moon Dust For Sale
                          relocating planets
                         satellite costs etc.
                       Saturn lift capabilities
                             Speculation
                       SSTO vs 2 stage (3 msgs)
        Stupid Shut Cost arguements (was Re: Terminal Velocity
           Terminal Velocity of DCX? (was Re: Shuttle ...)

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Date: Thu, 31 Dec 92 00:13 GMT
From: Karl Dishaw <[e-mail]>
Subject: Aluminum as rocket fuel?

> For final injection, it occurs to me that using gaseous oxygen to "blow"
> the powdered aluminum in might be an option.

We concentrated on not letting the fuel and oxidizer mix outside the
combustion chamber for safety reasons.  That scrapped LOX slurries and
blowing the powder.  Another project team sprayed molten steel over a
blast chamber when their methane/oxygen rocket accidently
mixed propellants in the feed lines, which makes me feel pretty
strongly about the safety criterion.

>
>What are the problems with using molten aluminum sprayed into the reaction
>area?  Keeping the aluminum molten in a vacuum should be relatively easy.

What are the weight and power penalties for keeping a tank of molten
aluminum on your spacecraft?  Could be expensive.  But we kicked
around some far-out ideas too--shaping the Al into fine wire and
burning it off a spool or as a "wool", or feeding the power in through an
airlock and burning it in pulses.

>Another source of information is the External Tank Study published
>by the Space Studies Institute. Cutting up ETs for their aluminum
>was listed as an option. Impulse of such an engine would be in the
>330 second range. Very viable as a Lunar based fuel source.

Is that for a pure Al/O2 engine?  The ETs have leftover H2 on board,
which SSI might've been including.  The exhaust has to be almost all O2
or the energy will be absorbed by the oxide particles with very little
thrust resulting.  My 118 sec Isp calculation was for about 4%
aluminum in the mass flow.


Karl
sold my soul to Uncle Sam . . . now marked down for resale.

------------------------------

Date: 30 Dec 92 23:46:20 GMT
From: Marvin Minsky <[e-mail]>
Subject: averting doom
Newsgroups: sci.space,sci.physics

In article <[e-mail]> [e-mail] (Thomas Clarke) writes:
>Newsgroups: sci.astro
>Path: cs.ucf.edu!news
>From: [e-mail] (Thomas Clarke)
>Subject: Re: averting doom
>Message-ID: <[e-mail]>
>Sender: [e-mail] (News system)
>Organization: University of Central Florida
>References: <[e-mail]>
>Date: Wed, 30 Dec 1992 19:41:39 GMT
>
>In article <[e-mail]> [e-mail] (Thomas
>Clarke) writes:
>> In article <[e-mail]> [e-mail] (John
>> McCarthy) writes:
>> > By the way, it seems to me that if the above idea is sound, it settles
>> > the question of the stability of the solar system - in the negative.
>> ... In the most recent Sci Am or Sky and Telescope
>
>It was Sky and Telescope Feb '93 ppp 13-14.
>I remembered wrong.  A one millimeter perturbation of Mars' orbit
>eventually caused a 500,000 kilometer difference in the position of
>Pluto after 100 million years.
>
>Gerald Sussman and Jack Wisdom used the Supercomputer Toolkit at MIT
>to simulate the solar system.

McCarthy has been discussing the tame-asteroid proposal with Sussman
et al.

------------------------------

Date: 31 Dec 92 00:32:41 GMT
From: Dave Michelson <[e-mail]>
Subject: averting doom
Newsgroups: sci.astro,sci.space,sci.physics,sci.environment

In article <[e-mail]> [e-mail] (Andrew - Palfreyman) writes:
>I like the simplicity of this idea (moving the Earth instead of
>trying to shield it), but what the heck's all this "elastic
>collisions" stuff? Surely you're not serious about the "broken
>Kepler" business?
>
I think John's "broken Kepler" method is essentially the "patched conic"
approximation.  Please correct me if I've misinterpreted this...

--
Dave Michelson
[e-mail]

------------------------------

Date: Wed, 30 Dec 1992 23:00:13 GMT
From: "Dr. Norman J. LaFave" <[e-mail]>
Subject: Government-run programs  Was: Re: Justification for the Space Program
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]> Paul Dietz,
[e-mail] writes:
>You have to be careful with polls.  A poll in which people are asked
>"do you want a manned space program?" will ellicit a generally
>positive response.  However, similar questions on other issues, like
>education, health care, and so on, ellicit much more positive
>responses.  The *relative* support of the space program is not very
>high.

Another Dietz assertion-without-proof... Please
provide data which shows the relative support.

Norman

Dr. Norman J. LaFave
Senior Engineer
Lockheed Engineering and Sciences Company




When the going gets weird, the weird turn pro
                               Hunter Thompson

------------------------------

Date: Thu, 31 Dec 1992 01:59:03 GMT
From: Paul Dietz <[e-mail]>
Subject: Government-run programs  Was: Re: Justification for the Space Program
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]> Dr. Norman J. LaFave <[e-mail]> writes:

>>You have to be careful with polls.  A poll in which people are asked
>>"do you want a manned space program?" will ellicit a generally
>>positive response.  However, similar questions on other issues, like
>>education, health care, and so on, ellicit much more positive
>>responses.  The *relative* support of the space program is not very
>>high.

> Another Dietz assertion-without-proof... Please
> provide data which shows the relative support.


Well, Doc, I can't, because I do not recall where or just when this
poll was conducted (it was some years ago).  However, if you wish to
call me a liar about it, I shall try to cope.

    Paul F. Dietz
    [e-mail]

------------------------------

Date: 30 Dec 92 20:49:25 GMT
From: Chris Marriott <[e-mail]>
Subject: How many flights are Orbiters designed for?
Newsgroups: sci.space

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What is the design lifetime of a shuttle orbiter?  ie, how many times is
it designed to be reused?

Chris
--
--------------------------------------------------------------------------
| Chris Marriott                           | [e-mail]    |
| Warrington, UK                           | BIX: cmarriott              |
| (Still awaiting inspiration              | CIX: cmarriott              |
|  for a witty .sig .... )                 | CompuServe: 100113,1140     |
--------------------------------------------------------------------------


------------------------------

Date: 30 Dec 92 22:53:42 GMT
From: Henry Spencer <[e-mail]>
Subject: How many flights are Orbiters designed for?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>What is the design lifetime of a shuttle orbiter?  ie, how many times is
>it designed to be reused?

If memory serves, they are supposed to be good for 100 flights each.
Doubts have been expressed about whether they are actually good for
that lifetime.
--
"God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
       -Gene Cernan, the Moon, Dec 1972 |  [e-mail]  utzoo!henry

------------------------------

Date: Wed, 30 Dec 1992 17:55:18 GMT
From: Joe Trott <[e-mail]>
Subject: Justification for the Space Program
Newsgroups: talk.politics.space,sci.space

[e-mail] (Dave Jones) writes:

>John McCarthy ([e-mail]) wrote:
>> Let me add to the previous post the estimate that the total amount of
>> matter humanity has processed in its history is less than 10^12 tons.
>> --
>> John McCarthy, Computer Science Department, Stanford, CA 94305
>> *
>> He who refuses to do arithmetic is doomed to talk nonsense.
>>
>So let's do arithmetic: assume 5e10 people have lived to date.  That's
>20 tons per person across all of human history.  Divide by a human life:
>0.5 to 0.3 tons per year.  Say a few pounds a day.  Well, I think we know
>what kind of processing this number figures to represent.  Alimentary, my
>dear Watson.

That sounds like a lot of crap to me!

(Sorry, I couldn't resist...:))

-JTT

------------------------------

Date: Wed, 30 Dec 1992 23:02:13 GMT
From: Mike Ross <[e-mail]>
Subject: Moon Dust For Sale
Newsgroups: sci.space,sci.astro,alt.sci.planetary

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>>...2 inch piece of transparent tape which has some Moon dust on it.  This is
>>the first time that Moon dust is being offered for sale.   The Moon dust
...
>>to be genuine by Superior Galleries and is expected to be sold
>>in the price range of $75,000 to $100,000...
>

>unless things have changed recently, the ownership of this Moon dust is
>best described as "disputed".  NASA's position is that all, repeat all,
>lunar material returned by Apollo is US government property, and any
>offered for private sale is stolen goods.
>

If NASA 'officially' knows this and allows the sale, does it waive future
rights to go after Moondust Marauders?  I'd love to know how much the
original technician got out of the whole deal.

- mike
--
******************************** [e-mail] *****
* Michael L. Ross/C33 | Lockheed Engineering & Sciences Co.   *
* Robotics Department | 2400 Nasa Rd. 1, Houston, TX 77062    *
*[phone] voice,[phone] fax**********boring, eh?****

------------------------------

Date: Wed, 30 Dec 1992 17:14:30 MST
From: "Richard Schroeppel" <[e-mail]>
Subject: relocating planets

There's no need for the nuclear reactors to move Ceres.
You can use a much smaller asteroid to tranfer angular momentum & energy
between Ceres & (say) Vesta.  Ceres needs to be moved only enough to
either approach Mars, or a resonance with Jupiter; probably the resonance
is closer.  And, of course, the smaller asteroid could be manipulated
with a still smaller asteroid, etc.  The same scheme could be used to
eject Ganymede from its orbit around Jupiter, giving you a larger working
mass.  Of course, the tides from even a Ceres close approach might be
a problem:  Assuming Ceres's mass is 1/8 that of the moon, it would cause
equivalent tides at 1/2 the Lunar distance, ~ 30 Earth radii.  If it
passes at 1 Er, that's 27000 times the tidal force.  Could be fun to
watch, from a safe distance.

Wrt accurate gravity measurement & orbit prediction, I'd guess that the
uncertainty principle is the greatest problem; you can't know Ceres
position & velocity accurately enough to predict more than (say) 100
encounters ahead.  The steering rockets would have to be capable of
influence exceeding hbar; pea shooters would do.

Rich Schroeppel  [e-mail]

------------------------------

Date: 31 Dec 92 00:29:00 GMT
From: Gary Coffman <ke4zv!gary>
Subject: satellite costs etc.
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Pat) writes:
>In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>
>Actually, henry.  both of you are sticking to the clarke orbit model.
>
>Most of the effort in the Telecom industry is oriented towards
>LEO comm sats.  store and forward or multiple fast relay satellittes.
[deleted]
>Oncve again,  for LEO  commsats,  rendevous is quite feasible.
>
>you could even use the shuttle to  grab them up.

I'd note that we haven't actively been using LEO commsats since Telestar
for video or other high bandwidth downlinks. The Iridium concept is a
narrow band quasi-cellular phone proposal. Seamless handoff for video
and high bandwidth data is a thorny problem, but can likely be solved
as we move from analog to digital transmissions. High bandwidth still
requires high link budgets, however, and Earth stations are not necessarily
going to get cheaper unless the satellites get much more powerful, and
larger, than is currently projected for LEO. Clarke orbit has the real
advantage of allowing high gain fixed dishes to set the link margin.

Gary

--
Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems |    we break it.     | uunet!rsiatl!ke4zv!gary
534 Shannon Way             |    Guaranteed!      | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244     |                     | emory!ke4zv![e-mail]

------------------------------

Date: Thu, 31 Dec 1992 01:02:56 GMT
From: Dave Michelson <[e-mail]>
Subject: Saturn lift capabilities
Newsgroups: sci.space

A lot of people obviously feel that Skylab was worth saving.  Was it?

Although items such as food and clothing could have been replenished
rather easily, I'm under the impression that oxygen and nitrogen could
not.  Skylab was essentially designed as a "throw-away" workshop not
a real space station.  I assume that there was a comfortable safety margin
built into Skylab, but how much life support capability was left after
the last crew departed?

I suppose that one could have docked an "environmental module" with
replenishable O2 and N2 tanks at the docking port and, with suitable
ventilation, kept the workshop habitable.  Were plans for such a
"life extension" module ever considered?

--
Dave Michelson
[e-mail]

------------------------------

Date: Thu, 31 Dec 92 00:14 GMT
From: Karl Dishaw <[e-mail]>
Subject: Speculation

>The most straightforward way to impart a delta-v to Ceres is to install
>a large number of nuclear reactors on it, and use the energy to expel
>fragments of Ceres in a desired direction and at an appropriate velocity.

Gives you some perspective on the "Delta Clipper
can/will/should/may/won't work" controversy, doesn't it?  ;-)


Karl
sold my soul to Uncle Sam . . . now marked down for resale.

------------------------------

Date: Wed, 30 Dec 1992 22:52:56 GMT
From: "Edward V. Wright" <[e-mail]>
Subject: SSTO vs 2 stage
Newsgroups: sci.space

In <[e-mail]> [e-mail] (Charles Pooley) writes:

>People keep debating the merits of 2sto vs ssto, and are overlooking what
>I think is the main consideration.

>The 2nd stage will have the highest Isp possible, a large nozzle for the
>vacuum conditions, and little or no consideration for aerodynamics.

Unfortunately, you have what Max Hunter calls "Isp on the brain."

The goal of the SSTO development program is not to maximize Isp,
minimize mass ratio, or build "the most powerful launcher in the
West" (whatever the hell that means).

It is to reduce the cost of putting payload into orbit.  Period.

------------------------------

Date: 30 Dec 92 22:51:28 GMT
From: Henry Spencer <[e-mail]>
Subject: SSTO vs 2 stage
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Charles Pooley) writes:
>So, for the 1st environment, the 1st stage should have the durability to
>cope with the aerodynamic loads and have engines optimised for use in
>atmpsphere...

In practice, even first-stage engines are necessarily a compromise between
atmosphere and vacuum operation.  If you look at the cutoff altitudes of
typical first stages (ignoring little strap-ons and the like), a substantial
fraction of their burn time is spent in near-vacuum.

>The general idea, it seems, is not to take any component or capability
>of the rocket past the point it is needed.  ie, wings, landing gear,
>parachutes, rugged construction etc for low altitude conditions not go
>beyond staging point...

Of course, the same is true for aircraft.  The design of an aircraft's
wings, in particular, is heavily driven by takeoff and emergency-landing
requirements.  (Normal landings, at least for long-haul aircraft, are
made at substantially lower weights than takeoffs and worst-case emergency
landings.)  Would it make sense to build two-stage aircraft, with the
upper stage optimized for high speed at high altitude (plus landing at
relatively low weights after fuel is burned)?  Well, yes, in a way, and
it's even been done occasionally, for research aircraft like the X-15.
But nobody would buy a commercial aircraft built that way, even though
performance would be better, because staging is simply too much trouble
and expense when one-stage designs work fine.

There will be a place for staging throughout the foreseeable future.
No propulsion system likely to be practical soon would be capable of
launching a short-flight-time mission to Pluto without staging; even if
the DCs work perfectly, missions like that will use upper stages.

But it's not necessary or desirable for hauling payloads into low
Earth orbit; we have the technology to do without it, and doing so
has potential to reduce costs quite substantially.
--
"God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
       -Gene Cernan, the Moon, Dec 1972 |  [e-mail]  utzoo!henry

------------------------------

Date: Thu, 31 Dec 1992 01:51:57 GMT
From: Paul Dietz <[e-mail]>
Subject: SSTO vs 2 stage
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Edward V. Wright) writes:

>>chemical rocket propulsion, for rather fundamental reasons.  It is
>>therefore not inconceivable that multistage launchers would be
>>appropriate even though multistage aircraft are not.

>I didn't ask if you could say "It is not inconceivable."  I asked
>if you could prove it.


No, what you did was deride a careful and thoughtful analysis by Bruce
Dunn by offering a strained analogy between aircraft and spacecraft.
I merely pointed out your analogy was flawed.

Since Bruce was the one who posted the quantitative argument, it
seems to me that it is incumbent on *you* to offer concrete evidence
why he is wrong.

    Paul

------------------------------

Date: 30 Dec 1992 20:05 CST
From: [e-mail]
Subject: Stupid Shut Cost arguements (was Re: Terminal Velocity
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Allen W. Sherzer) writes...
>In article <[e-mail]> [e-mail] (Brian Stuart Thorn) writes:
>

>>    GRO and UARS are both candidates for return to earth.
>
>Doing that would cost more then they are worth. It would be cheaper to
>build new ones and launch them commercially.
>

I would dearly love to see your cost analysis on this Allen. Since the
marginal cost for a Shuttle mission is only 37 million dollars, this is
what it would cost for a reflight. By the way your Titan IV cannot lift
a payload like HST due to its adverse dynamic envelope. For a reference NASA
publishes a guide to the environments of all major vehicles. Titan is about
1.5 times more harsh from a dynamics standpoint than the Shuttle. Many
Shuttle payloads are dynamically designed for the realtively benign
environment of the Shuttle. (+/- 10 g in the thrust direction, +/- 6 g for
the other two axes) This is worst case dynamic load. The 3 g max acceleration
helps to keep the true values much below this on an average basis.  This
helps the designer of a large sat flying on the shuttle to build a lighter
satellite or this can be used to build a structure (such as HST) that would
have a hard time on Titan. Don't drag our your tired tale of the Spy sats
either. You have no idea what actually goes into them other than their mass.

>>    LDEF and
>
>LDEF would have been better flown as a series of smaller platforms.
>Under those conditions it would be simple to build a vehicle which
>returns them to Earth. That way each experimenter would get custom
>time on orbit and the taxpayers would save billions.
>

That is your opinion Allen not an engineering judgment. There was much
value in flying the LDEF like it was. One thing is that this gave a level
environment for all of the experiments. If they were flown seperately, and
at different times and orbits, there would be no conclusive comparative data
to allow the careful analysis of the properties of the materials flown.


>>    The Hubble repair could still prove too much for orbiting
>>    astronauts and thus require return to Earth for mirror replacement,
>
>No for two reasons: 1) it would be cheaper to build another and fly it
>and 2) in testimony before the House the program manager said Hubble
>wouldn't survive the return trip.

For 1) see the above. For 2) from what I have heard from the HST program
manager at Marshall, they could bring it back down. That is a contingency if
the solar array replacement goes awry.

>
>To date there are no payloads which can be returned by Shuttle in a
>cost effective manner.
>

Again this is your opinion that simply is not based upon the facts.


>>    All I'm saying is that Shuttle
>>    did not meet its objectives, so don't be so sure about DC.
>

I hope very much that DC meets all of its objectives. I support the DC
program.

>Same old arguement. I guess Boeing better cancel plans for the 777.
>After all, Shuttle failed so 777 will as well.
>

No what this poster is saying Allen is that the claims that you are making
for the DC are exactly the claims made for the Shuttle. You through all of
your postings have made it clear that the DC can do everything the shuttle can
and more, which is untrue.


>>    A few weeks ago I mentioned one way that we could have kept some of
>>    that market in the U.S. until NLS, DC or whatever was ready. You
>>    said that it (maintaining Shuttle launches of commercial payloads)
>>    was too costly. Maybe so (definitely so) but those subsidies would
>>    have at least kept customers in the U.S.
>
>And at the same time killed any chance of a sustainable independent
>commercial effort. If your going to do that it would be cheaper to
>simple end all space activity.
>

Fact is no one wanted the capablility. The great leap in the market for
communications satellites did not come until the 80's. The market for
small LEO sats did not exist until the late 80's and now. Fact is that the
Shuttle proved the viability of the large lift capability that is now
embodied by its competitor the Titan IV. This market did not exist and I
submit that it would not now if the Shuttle had not been there for designers
to design big payloads for.


>>    Why wasn't DC-X built in 1983
>
>You mean when the government was spending billions killing competition
>with Shuttle subsidies? You can't be serious; who would be that stupid?
>

You left out the most important reason in your ad hominim attack. The materials
technology to support the possibility of the DC series SSTO did not exist
prior to 1987. It was those pesky government supported programs like the
B2 bomber and the NASP that provided the new generation of materials that
allows the DC to do its job. This is straight off of the MacDac and SDIO fact
sheet Allan.

>>    your argument that the next generation of boosters be a commerical
>>    endeavor? What is it they say about building a better mousetrap?
>
>It is hard to convince investors when they see that the largest customer
>doesn't care about cheaper costs.
>

By the way that largest customer is that same pesky government that is keeping
all of your space dreams from coming true. The largest customer has a great
case of CYA. That customer cares more about the safest way to get a payload to
space, not the cheapest. That is why uncle sugar spent three quarters of a
billion on new boosters and over a half a billion on pad modifications.

By the way you never answered my qestion of whether you would be willing to
include the 1960 dollar cost of the development of the Atlas (5 billion) and
the cost of the development of the Titan (5 billion for Titan I) and add
another 4 billion for II and III.

Also from what I have read, inflation is about 375% of the 1967 level today.
That precludes a 400% rise from 74 to 86.

Also to jump to another subject. The 1993 farmers Almanac lists that there are
111 operating nuclear plants in the US generating 21.7 percent of our
domestic electrical energy needs. There are 8 construction permits that are
in progress.

Dennis, University of Alabama in Huntsville

------------------------------

Date: 31 Dec 92 00:19:42 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Terminal Velocity of DCX? (was Re: Shuttle ...)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Pat) writes:
>Consider that the russians/CIS/USSR  built a major space program with
>the GNP the size of France.   And by the Way,  unlike the germans, or chinese
>i dont believe the russians have ever been charged with using slave
>labor.  Now the russians had a strange command economy,  but things still
>cost, but there were major problems in distribution.  the russian/SU
>economy was sorta like massachusetts meets new york via sweden.
>
>high taxes,  severe rent control and social provision of major services.
>
>SUre,  they didnt pay their scientists what we paid them here,  but they
>provided them with housing, medicine, etc.   Also,  the motivation of most
>russian space workers was so great,  that they didn't mind the bad conditions.
>
>the problems within the russian system, were of productivity,  design cycle,
>and provision of consumer goods.
>
>The chinese use slave labor,  and then sell it over here.  the russians
>paid their workers poorly,  and the workers pretended to work.
>
>the gulags were not used as factories to my knowledge.

I agree with all of this. My point was that all those social services,
which in our system are paid out of worker salaries, were paid out of
a different account that wasn't charged against their space program.
So using their numbers is an invalid comparison with numbers from a
differently organized economy because many of their costs are "hidden"
in other government accounts. That looks like it's changing, and we
may soon discover that Russian costs *aren't* really much lower than
ours for similar launchers.

Gary
--
Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems |    we break it.     | uunet!rsiatl!ke4zv!gary
534 Shannon Way             |    Guaranteed!      | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244     |                     | emory!ke4zv![e-mail]

------------------------------

End of Space Digest Volume 15 : Issue 616
------------------------------