Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v08/v8_296.txt

Internet Message Format | 1991-07-08 | 17KB

Return-path: <[e-mail]>
X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail
Received: from po2.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr1/ota/space/[e-mail] (->+dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl) (->ota+space.digests)
          ID </afs/andrew.cmu.edu/usr1/ota/Mailbox/po2.andrew.cmu.edu.278.0.0>;
          Tue, 26 Jul 88 04:09:50 -0400 (EDT)
Received: from andrew.cmu.edu via qmail
          ID </afs/andrew.cmu.edu/service/mailqs/q003/QF.andrew.cmu.edu.22ec3ddb.9c1131>;
          Tue, 26 Jul 88 04:07:58 -0400 (EDT)
Received: by andrew.cmu.edu (5.54/3.15) id <AA00294> for +dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl; Tue, 26 Jul 88 04:07:21 EDT
Received: by angband.s1.gov id AA01819; Tue, 26 Jul 88 01:05:47 PDT
    id AA01819; Tue, 26 Jul 88 01:05:47 PDT
Date: Tue, 26 Jul 88 01:05:47 PDT
From: Ted Anderson <[e-mail]>
Message-Id: <[e-mail]>
To: [e-mail]
Reply-To: [e-mail]
Subject: SPACE Digest V8 #296

SPACE Digest                                      Volume 8 : Issue 296

Today's Topics:
             Re: Ramscoop engine
     US/USSR delegations to meet on space cooperation (Forwarded)
            Re: Electromagnetic Launchers
             Re: Von Braun quote
              Re: Rocket engine
              Re: Hubble Space Telescope
     Re: advance space news from June 6 AW&ST -- Pegasus!
            Re: Electromagnetic Launchers
              Re: Hubble Space Telescope
----------------------------------------------------------------------

Date: 11 Jul 88 12:30:09 GMT
From: aplcen!aplcomm!warper.jhuapl.edu![e-mail]  (Tony Nardo)
Subject: Re: Ramscoop engine

In article <[e-mail]> [e-mail] (Tom Neff) writes:
>Whenever ramscoops come up, somebody always mentions that you could get
>to the Andromeda Galaxy in 25 years, ship time.  This has always struck
>me as nonsense.  Where are you supposed to find the fuel between the two
>galaxies to continue that 1G acceleration?

If you kick your speed up to that close to 'C' while you're in the galaxy,
then you don't need to continue accelerating once you leave.  By the time
the interstellar hydrogen runs too thin to use, you should be out of the
galaxy's gravity well.

I have a different concern.  With relativistic effects, will the reaction
time of your navigation computer slow down?  How you avoid collisions with
unanticipated objects (gee, we never *did* chart that rather dim protosun
now, did we?...) at such speeds, if so?

==============================================================================
ARPA:   trn@[e-mail]       \  one of these should work,
        aplcen!isl![e-mail]    }    but you may have to route
        [e-mail] /     thru ucbvax.berkeley.edu
UUCP:    aplvax!trn@warper
USnail: c/o Johns Hopkins University/APL, Room 7-53
    Johns Hopkins Road
    Laurel, Md. 20707

"You can't win, you can't break even, you can't even quit the game."
==============================================================================

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

Date: 12 Jul 88 00:13:02 GMT
From: [e-mail]  (Peter E. Yee)
Subject: US/USSR delegations to meet on space cooperation (Forwarded)

Debra J. Rahn
Headquarters, Washington, D.C.                     July 11, 1988

RELEASE: 88-95

US/USSR DELEGATIONS TO MEET ON SPACE COOPERATION


     A U.S. delegation headed by Samuel Keller, deputy associate
administrator for space science and applications, will meet with
Soviet counterparts in Moscow, July 14 and l5, to discuss
implementation of the enhanced US/USSR space cooperation agreed
to at the US/USSR Summit.

     Discussions will focus on planning for the exchange of
flight opportunities to fly scientific instruments on each
other's spacecraft and how to coordinate exchanging results of
independent national studies of future unmanned solar system
exploration missions.

     The two sides are expected to present preliminary
information on the types of scientific instruments for which
cooperative flights might be of interest and summary lists of
solar system exploration mission studies underway.  They will
discuss guidelines for selection of experiments for flight
opportunities identified by either side, respecting normal
selection practices and administrative procedures for contacts
with their respective scientific communities.  Finally, they plan
to outline formats and mechanisms for reporting results of
unmanned solar system mission studies.

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

Date: 11 Jul 88 22:17:02 GMT
From: cat.cmu.edu![e-mail]  (David Pugh)
Subject: Re: Electromagnetic Launchers

In article <[e-mail]> [e-mail] (Paul F. Dietz) writes:
>...
>The vehicles could not just be unguided projectiles, like bags of
>lunar material launched using a mass driver, since vehicles are
>placed onto elliptical orbits with perigee beneath the Earth's surface.
>...

Why? If the package managed to _hit_ the station at apogee (and sticks),
it wouldn't need any rockets at all. Of course, the station would have
to be rather sturdy....

Seriously, this might not be such a bad delivery method for raw materials.
Just have an armored, high-Isp "catcher" which catches several bundles and
reboosts itself to the station. By making the catcher unmanned and launching
the packages such that their apogee is << the station's altitude, it should
be safe and cheap.
--
"Good ol' JT."  "On the QT, I hear it was    David Pugh
EDB..." "Gee! Just like DB and the PCB's..."    ....!seismo!cmucspt!cat!dep
"Yep, DOA." "And the FDA said it was OK?"
"Well the EPA put out an SOS ASAP." "Poor SOB." "RIP."

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

Date: 12 Jul 88 08:08:39 GMT
From: thumper![e-mail]  (Phil R. Karn)
Subject: Re: Von Braun quote

Henry, I'm impressed. You *have* been reading up on us, haven't you!

But since you like to quote anecdotes, let's pick the Solar Max rescue
mission. Remember how George ("Pinky") Nelson grabbed one of the solar
arrays in an attempt to stop the satellite from spinning? Not only did
he not stop the spin, but he precessed it so much that the solar arrays
were shadowed and the spacecraft was nearly lost when the batteries
almost ran down.  And I won't even mention the strong likelihood that
the rescue mission cost more than a simple replacement would have.

I've never understood why it's so necessary to put humans into space in
order to benefit from their ability to react to unforseen circumstances.
In many situations, it makes far more sense to keep such people on the
ground instead of sending them along with the payload, especially since
the state of the communications art has gotten so good. Keeping your
human "crew" on the ground has many advantages. The payload is
enormously simpler, because it doesn't have to provide man-rated life
support and a means to return the crew. Your human "crew" can be much
bigger, and you can easily change them after launch. They need not be
prime physical specimens; they can be chosen solely for their technical
skills and perhaps even their understanding of the basic physics of
rotating bodies (unlike Pinky Nelson).

Your arguments represent a convincing case for versatile remote control,
not for manned spaceflight. In the case of Oscar-10, those of us on the
ground had plenty of opportunity to exercise our ability to react to
unforseen circumstances. With the help of a versatile on-board computer
that can be completely reprogrammed from the ground,  we were able to
save the mission.

Phil

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

Date: 11 Jul 88 08:37:50 GMT
From: mcvax!enea!kth!draken![e-mail]  (Per Hammarlund)
Subject: Re: Rocket engine

In article <[e-mail]> [e-mail] (Phil R. Karn) writes:
>It's probably safe to say that bomb design, like rocket design, is more
>art than science. Otherwise the comprehensive test-ban treaty wouldn't
>be such a big issue. The whole point of a test ban is to inhibit the
>development of new weapons. If computer simulation were all that is
>needed, I'd think we'd find the hawks on the American side strongly
>supporting a ban because of our considerable computational advantage
>over the Soviets. But it's the hawks on our side that oppose it most
>vigorously.

Does anybody have a ratio between "testing of new weapons" and "just
checking the old stuff"?

I don't think that the whole point of a test-ban treaty is to inhibit
the development of new weapons, though it IS one aspect! Another point
is that a test-ban would add insecurity about whether the hardware you
have in stock actually works, and that this would make "traditional
warfare" more desirable or at least more reliable.


I gather the hawks you mention are politicians!?

I think every engineer likes to make a prototype of his/hers work and
then test it, no matter how sure he/she is that it will work!?! (If
you are constructing something like the space shuttle you will at
least make prototypes of the subsystems and then test them.) Even if
computers is all it takes to construct a bomb you would still like to
test it, if nothing else to see how it performs.

When the x-ray laser was developed, read "Aviation - or Defense leek",
the theory was "right" and it had most likely been heavily simulated
but it was tested anyhow.


Even if computer simulations come close to reality, reality is reality
is..

    /Per Hammarlund

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

Date: 11 Jul 88 23:03:27 GMT
From: sco![e-mail]  (Allan J. Heim)
Subject: Re: Hubble Space Telescope

It's true, turning the HST downwards would fry the instruments
aboard it.  But the KH-12 (the reconnaissance satellite based
on the HST) doesn't use the same instruments.  The optics and
overall structure are similar to the Hubble instrument, but
the equipment aboard is designed for a reconnaissance role.

al

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

Date: 12 Jul 88 10:55:31 GMT
From: agate![e-mail]  (William Baxter)
Subject: Re: advance space news from June 6 AW&ST -- Pegasus!

>>William Baxter

>Henry Spencer

>Having the government as a customer is very different from having it
>as a partner.  Unless I am much mistaken, DARPA will pay only for launches,
>not for promises.  That's a BIG difference.

There is a lot of room for wonder when the contract is signed so far in
advance of full development.  It seems that DARPA is going for two in
the bush when, after two and a half years without a shuttle launche,
they purchase a launch from a company that promises a cheap launch on an
undeveloped booster rather than buying them from another company which
uses proven equipment.  Someone remarked that the Conestogas use motors
that the Delta uses.  This argues in their favor, not against them.

I have heard that Hercules is having problems with cost overruns and
production delays on their other motor development projects.  If true,
this would raise more serious questions about the wisdom of DARPA in
signing on at this stage.  Please correct me if you know otherwise.

>             I would speculate that the B-52 is being provided on
>a basis of "until we have our own carrier aircraft, the customer has to
>supply it".

And a company with a ground launched vehicle should be able to launch
from Cape Canaveral for free so long as the government is the customer?
This rather artificially alters the price of the launch.

>The problem with Space Services is that they've taken so long to deliver;

I beg to differ.  The problem with Space Services is that they got into
the game a bit too early, and ran into ridiculous government resistance
to development of private launch services.  Their chances for success
increased dramatically with the explosion of Challenger.  But in the two
and one half years since then, how many launches has the government
purchased from the private sector?  And how many companies are going to
risk their satellite on a private vehicle that the government does not
trust enough to use?

>the problems with Amroc and Pacific are that they insist on developing
>new technology, and that they too are showing signs of having trouble
>delivering soon (I for one consider it a bad sign when the design of the
>vehicle changes repeatedly, over a period of years, before anything actually
>flies).

The fact that a vehicle design changes repeatedly "before anything
actually flies" is not a problem--that is simply development.  Amroc is
conducted so many tests that they may well understand the motor they
have *before* they use it in a launch. In contrast, the Pegasus will be
flown without verification launch or booster calibration (AW&ST June
27).

>> What happens when there are cost overruns and production delays?

>Presumably, existing contracts would have to be renegotiated (unless there
>were provisions for such already present), leading to possible loss of
>business.

If they end up with long delays or lose the contract after a couple of
years they will hurt the whole industry, by degrading further the
reputation of launch companies for investment, and in delay of
contracts for other companies.

OSC and Hercules are risking a lot on Pegasus, and they will probably
deserve whatever they get.  I too am glad to see someone attempting this
approach to building as launch vehicle.  But it is not *the* correct
way.

William Baxter

ARPA: web@{garnet,brahms,math}.Berkeley.EDU
UUCP: {sun,dual,decwrl,decvax,hplabs,...}!ucbvax!{garnet,brahms,math}!web

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

Date: 12 Jul 88 14:13:42 GMT
From: [e-mail]  (Paul F. Dietz)
Subject: Re: Electromagnetic Launchers

In article <[e-mail]> [e-mail] (David Pugh) writes:
>>The vehicles could not just be unguided projectiles, like bags of
>>lunar material launched using a mass driver, since vehicles are
>>placed onto elliptical orbits with perigee beneath the Earth's surface.
>
>Why? If the package managed to _hit_ the station at apogee (and sticks),
>it wouldn't need any rockets at all. Of course, the station would have
>to be rather sturdy....

The catcher would have to be pretty massive.  The requirement that
the catcher be at the package's apogee would restrict the orbits the
system could launch to.  GEO would work, but I don't see how to launch
to HEEO.

Their is a guidance problem.  In O'Neill's scheme, the lunar soil
packets are very carefully tweaked after launch, so the velocity
error is something like 1 meter per *hour*.  There is no way you can
achieve that kind of accuracy firing through the atmosphere.  Also,
in the orbits I mentioned, apogee position is a sensitive function
of the initial velocity.

I was imagining each vehicle would have maneuvering rockets for
course corrections as well as to raise the apogee.  Given that
complexity, it would be a shame to smash the carrier after each use.

On the other hand, there's no reason why the vehicle would have to get
smashed.  It could carefully release its payload, say, ten minutes
before hitting the station, and gently move aside.  I would then reenter,
having never gone into orbit.

    Paul F. Dietz
    [e-mail]

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

Date: 12 Jul 88 15:33:57 GMT
From: ncar!noao!stsci![e-mail]  (Jim Berry)
Subject: Re: Hubble Space Telescope

From article <334@scolex>, by [e-mail] (Allan J. Heim):
> It's true, turning the HST downwards would fry the instruments
> aboard it.  But the KH-12 (the reconnaissance satellite based
> on the HST) doesn't use the same instruments.  The optics and
> overall structure are similar to the Hubble instrument, but
> the equipment aboard is designed for a reconnaissance role.
>
> al

No, pointing HST 'downwards' will not fry the instruments.  At least
one of the instruments, the Wide Field/Planetary Camera, requires that
the telescope be pointed at the sunlit Earth in order to approximate
a flat field (several 'smears' are taken at different angles resulting
in a uniform gray field).  In addition, since HST will be in a low-Earth
orbit, it will not be unusual for a target to be 'eclipsed' by the
Earth.  Rather than slewing around so as not to point 'down', the
telescope will typically maintain its attitude.

On the other hand, it is quite possible to damage some of the instruments
by leaving their detectors active while slewing through a bright Earth,
but simply pointing HST at the Earth won't necessarily do it.

There is a bit of folklore around here that tells how the first HST objective
mirror 'got lost', and another had to be made.  Cute story, regardless
whether it's true or not.

======================================================================
Jim Berry                         | UUCP:{arizona,decvax,hao}!noao!stsci!berry
Space Telescope Science Institute | ARPA:   [e-mail]
Baltimore, Md. 21218              | SPAM:   SCIVAX::BERRY, KEPLER::BERRY

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

End of SPACE Digest V8 #296
*******************