Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_5/V13_545.TXT

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Subject: SPACE Digest V13 #545

SPACE Digest                                     Volume 13 : Issue 545

Today's Topics:
              Re: Why the space station?
          Re: Energia (was Re: Saturn V blueprints)
             Re: Laser launchers
               Re: Saturn V and the ALS
             Re: Why the space station?y
       Re: Ethics of Terraforming (was Re: Terraforming Venus)
                Barbara Boxer
                   Re: NASP
                2001 and NASP
              Re: 2001 and NASP

Administrivia:

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

Date: 11 May 91 22:30:32 GMT
From: [e-mail]  (Clark Brooks)
Subject: Re: Why the space station?

[e-mail] (George William Herbert) writes:

>We're going to fly 17 shuttle missions to lift and assemble Freedom, and at
>25 tons each this is about 425 tons-equivalent to orbit.  If instead we
>were to build it in a plug-cans-together manner (no truss, etc) we could
>very likely get the same capability for a lot less weight to orbit.  I.E.
>5 to 10 Titan launches (100-200 tons).  This is the approach that MIR was
>built under.

Oliver Harwood used to work for one of the aerospace companies
around here. He combined this idea with a knowledge of Fuller's space frame
and a love of modularity to produce a truss FROM cans-plugged-together.
It's a marvel of design. It's only flaw is that it's so modular that
Congress could cut its budget down to 2 (two) shuttle construction-flights
without totally killing it.

        -- clark@csvax
If we knew what we were doing, it wouldn't be science.

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

Date: 30 Apr 91 14:22:00 GMT
From: unisoft!hoptoad!pacbell!pacbell.com!mips!zaphod.mps.ohio-state.edu!caen!ox.com!fmsrl7![e-mail]  (Ron Carter)
Subject: Re: Energia (was Re: Saturn V blueprints)

In article <[e-mail]> [e-mail] (/dev/null) writes:
>In article <[e-mail]>, [e-mail] (Doug Mohney) writes:
>>They need the cash too badly...they'd provide decent services. There's nothing
>>which NASA needs to lift into orbit on Energia which couldn't wait a couple of
>>years in case of disruption of launch services from the Soviet Union ....
>Yeah, but the couple of years disruption might turn into no more launchers
>from the USSR, and then where would we be?

Has anyone considered:

a.)    Buying the plans and tooling from the Soviets, and

b.)    Producing Energiya's (or Protons, or SL4s) here under license?

If the USSR succumbs to political unrest, you can hold royalty payments
in your bank account drawing interest (and maybe never have to pay ;-).

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

Date: 10 May 91 16:18:13 GMT
From: cis.ohio-state.edu!sample.eng.ohio-state.edu!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!ox.com!fmsrl7![e-mail]  (Ron Carter)
Subject: Re: Laser launchers

In article <[e-mail]>, [e-mail] (Gary Coffman) writes:
>Sorry, but a laser launch system must carry "reaction mass" to be heated
>by the laser beam. This *dead weight* produces no useful energy input.
>It's mass and tankage mass must still be carried aloft by energy input
           ^^^^^^^^^^^^^^^^
>from the laser beam alone.

Current concepts have eliminated the tankage by carrying the propellant
as a solid (ice).  This eliminates materials costs for the tankage and
gives a huge savings in manufacturing costs; freezers are very very
cheap to run and reproduce simple shapes (like slugs) quite well!

Incidentally, the fuel cost of launching a rocket is a tiny part of
the total cost.  If LH2 costs $10/kg, the fuel for a Space Shuttle
launch is only about a million bucks.  Inflating the fuel cost by
an order of magnitude while cutting the hardware cost by the same
factor is a huge gain.

>Granted that at very low altitudes the
>atmosphere itself may be used as a working fluid, but above roughly
>5 km the atmosphere is not dense enough to carry the energy load and
>internal reaction mass must be carried. It makes little sense to carry
>*dead weight* when that same mass could release useful chemical energy.

Only in the naive case.  There are two points to consider:

1.)    Exhaust velocity.  Laser propulsion can impart far
    more energy to a gram of propellant than can chemical
    reactions.  This lowers the mass-ratio and the total
    energy required.

2.)    Cost of carrying chemical fuels.  They require tankage,
    nozzles, pumps for liquids, heavy walls for solids, and
    material and manufacturing for all of these.  Laser
    propulsion has the potential to eliminate them entirely.

Are you at all capable of thinking beyond the naive case?

>Using a space based laser is even worse in some respects than using a
>ground based laser. At least on the ground there is a large sink for
>the waste heat produced in the process of generating the beam. At least
>on the ground the massive tankage required for the laser reactants doesn't
>have to be heaved into space.
>... the mass required to be delivered to orbit to operate the
>laser far exceeds the mass of fuel needed to deliver the payload directly
>to orbit.

Now you are assuming chemical lasers.  Why would anyone carry a
chemical laser, which needs reactants which are used once and
exhausted, into space to launch things with?  Why not excimer
lasers, or free-electron lasers, or solar-UV-pumped gas lasers?

When you were knocking efficiency, you were talking about
electrically driven CO2 lasers on the ground (worst case, except
perhaps He-Ne lasers).   Now that you're bashing space-based
lasers, you are talking about chemical reaction lasers (worst
possible choice).  You can't have it both ways!

Take your straw-man engineering proposals and compost them, please.

>The higher exhaust velocity for a given heat input that light molecules
>like H2 give you is extremely valuable in increasing performance.

You can't get any significant exhaust velocity out of H2 without
supplying energy to it externally; you can't react H2 with H2.
If you burn it with O2, you've got H2O.  Laser-launch systems
will probably use (surprise!) H2O!

>The blooming problem is more than just a defocusing of the beam that
>can be solved by adaptive optics. At the beam power levels required,
>the atmosphere is turned to a superheated plasma....

Pray tell what those power levels are, and why we have to have
these high power levels anywhere except in the immediate vicinity
of the back end of the target.  Tell me why we can't just plug
in this power density limit as a design criterion for the optical
system.

>A one square inch kelvar tether to geosync orbit would weigh 45.2 million
>pounds. I don't have the handbook here at the terminal, but kelvar doesn't
>approach 45 million pounds per square inch tensile strength by orders of
>magnitude. It couldn't support itself, much less a usable payload.

More oversimplifying.  This ignores reduced weight as altitude
increases, tapering and improvement in materials.  To quote
one of the experts (lightly editted):

-From: andrew.cmu.edu!hm02+ (Hans P. Moravec)
-Newsgroups: sci.physics
-Subject: Orbital elevators (was Ringworld)
-Message-Id: <[e-mail]>
-Date: 21 Nov 90 04:05:39 GMT
-
[material deleted]
-    For Earth the taper with Kevlar would be 10^11, and the cable could
-hoist only about one trillionth of itys own mass -- which I admit makes
-it impractical!   But the required taper is exponential in the weight to
-strength ratio of the material, and a material only five times better than
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Kevlar (within the measured strength/weights of single crystals of various
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-substances) would bring the taper ratio to 160 and the mass fraction to
 ^^^^^^^^^^^
-1/2000.

So much for "physical impossibility".  It is just something that
materials science can't quite do today.  It is quite possible.

>Strength of materials ultimately depends on fundamental science. The bond
>strength of elements and compounds *are* physical limits. Diamond rods
>and certain graphite whiskers already approach physical limits quite
>closely, and those limits are still orders of magnitude too low.

"How wrong can someone be and still take himself seriously?", Ron
asks himself rhetorically.

>Now, now. I'm not anti-progress. I just don't see laser launchers or tethers
>as the solution for sound technical reasons.

So far, you have not demonstrated the soundness of your technical
reasons.  They sound more like closed-mindedness.  I'd like to see
you put numbers behind your "excessive power density" claims, a
reference for your "factor of 1000 to 1000000" claim, et cetera;
they would make me take you a great deal more seriously.

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

Date: 10 May 91 16:55:12 GMT
From: aio!icarus.jsc.nasa.gov![e-mail]  (Brad Mears)
Subject: Re: Saturn V and the ALS

In article <[e-mail]>, [e-mail] (Allen W. Sherzer) writes:
|> First explain to me why it costs $10 billion and ten years to do what
|> McDonnell and Martin say can be done for $500 million and four years.
|> What's wrong with their approach?
uh - less overhead? :)  Seriously, I haven't seen their proposals and can't
comment on them.  My "seat-of-the-pants" comment is that their low-bid could be
a low-ball.The quotes I saw from Rockwell to build Shuttle-C were a great deal
more $500M.  What will McDonnell and Martin do differently than Rockwell?

|> Why is NASA the only agency who can build things?
I don't want to imply that they are.  I know the Navy is working on SeaLar, and I
wish them luck.  I restrict my comments to NASA because that is what I know about.

|> What did NASA learn from the Shuttle?
They learned a LOT about what goes into performing routine space operations.  This
is the knowledge that they hope to use in construction of the next vehicle.

|> From what I see they think everything
|> is fine (except that Congress should buy more orbiters). This is also not
|> a flame but a serious question.
I don't know how to address that.  It seems to be more a matter of perception than
a matter of fact.  As far as asking for more orbiters, NASA asks for more because
they think they need(?) a fleet with N orbiters.  Until they get N, they keep
asking.

--
Brad Mears
[e-mail]

----------------------------------------------------------------------------
Opinions are expressly forbidden.  | "It is better to die on your feet
I speak for myself and no other.   |  than live on your knees"
                                   |                    - Dolores Ibarruri
----------------------------------------------------------------------------

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

Date: 9 May 91 17:15:16 GMT
From: usc!rpi!crdgw1!gecrdvm1![e-mail]
Subject: Re: Why the space station?y

In article <[e-mail]>,
[e-mail] (Frank Crary) says:
>
>In article <[e-mail]> [e-mail] writes:
>
>I was talking about the difficulties of manuvering into close proximity to the
>station (or any large, open structure). While the RMS will do fine for the
>final docking, that arm is only 15 meters long.  Alot of effort may be
>needed to get within 15 meters of the dacking adaptor without hitting the
>trussd, solar pannels or heat radiators. This is a particular problem is
>there is a docking failure. For example, due to a damaged radar beacon
>the Progress M7 resupply craft almost rammed the Mir space station. A
>ground controlled noticed in time, and aborted the docking. As the
>Progress passed the station (after failing to dock) it nearly hit a solar
>pannel. I feel this sort of accident is a much greater risk for Freedom,
>with so many things sticking out in so many directions.
>
>                                        Frank Crary
>                                        UC Berkeley
I thought I read something about this in a recent AW&S(forget the last
letter). If I recall correctly, concern was greater now that Freedom
has shrunk (as if adding a mountain of papers to something non-existant
can make it shrink) due to the lack of manuevering space and the need
to be that much more precise so as not to hit the closer modules.
Henry will probably write about it in a couple of months when he does
his summary of the issue :-).

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

Date: 10 May 91 04:37:04 GMT
From: VAX1.CC.UAKRON.EDU!mcs.kent.edu!usenet.ins.cwru.edu!agate!lightning.Berkeley.EDU![e-mail]  (Frank Crary)
Subject: Re: Ethics of Terraforming (was Re: Terraforming Venus)

In article <[e-mail]> [e-mail] (will) writes:
>
>...It is strange that humanity
>    thinks that in order for intelligent life to exist somewhere there must
>    be citys and space shuttles at least before it is considered intelligent
>
No, we think that there must be:
1) water, or at least SOME liquid to act as a solvent.
2) lower, e.g. less evolved, forms of life
3) ANY complex organic chemicals AT ALL on the surface.
The viking life science experiments were tested in the most desolate
places possible, including the dry valleys in antarctica. Even 100's
of km from ANY life, they still gave positive results. On Mars they\
did not. Even the idea of life evolving on Mars before the climate
went cold does not mean intelligent life. At most it means coral or
such like. At worst, it means pond scum.

>    Also, if there was life before, and it was lost, it should be discovered
>    and studied.  A lot must be done before we go and wipe out a planet just
>    for our own use.  Seems very selfish to me.
It may very well be selfish. However I am an avowed racist: I am strongly
biased in favor of the human race. If the growth and welfare of the
human race requires the loss of fosilized Martian pond scum, or even
now living micro organisims, I say the Martians loose.

                    Frank Crary
                    UC Berkeley

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

Date: 9 May 91 17:45:32 GMT
From: [e-mail]  (Adam R. Brody)
Subject: Barbara Boxer

Anybody know Barbara Boxer's views on space?  I just got a
solicitation for some campaign funds and was wondering if
she was worthy of any.

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

Date: 30 Apr 91 17:47:31 GMT
From: att!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!wuarchive!rex!rouge![e-mail]  (Fraering Philip)
Subject: Re: NASP

In article <[e-mail]> [e-mail] (Doug Mohney) writes:

>NASP is quite probably liberally building on "Aurora" and other black
>hypersonic projects.

What if it isn't? I get the strong feeling that a lot of duplication
of effort is going on.

--
Phil Fraering
[e-mail]
Joke going around: "How many country music singers does it take to
change a light bulb? Four. One to change the bulb, and three to sing
about the old one."

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

Date: 11 May 91 20:03:20 GMT
From: cleveland.Freenet.Edu![e-mail]  (Robert Clark)
Subject: 2001 and NASP


   Has anyone noticed the remarkable resemblance between
the proposed National Aerospace Plane and the space transport
in 2001: A Space Odyssey?
   Chalk up another one for Kubrick and Clarke.

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

Date: 12 May 91 19:09:09 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!samsung!news.cs.indiana.edu!maytag!watmath!watdragon!watyew![e-mail]  (James Davis Nicoll)
Subject: Re: 2001 and NASP

In article <[e-mail]> [e-mail] writes:
>
>   Has anyone noticed the remarkable resemblance between
>the proposed National Aerospace Plane and the space transport
>in 2001: A Space Odyssey?
>   Chalk up another one for Kubrick and Clarke.

    Wasn't the space plane in 2001 nuclear powered (NERVAesque,
if I recall correctly)?

                            James Nicoll

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

End of SPACE Digest V13 #545
*******************