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Subject: SPACE Digest V13 #384

SPACE Digest                                     Volume 13 : Issue 384

Today's Topics:
             Re: Laser launchers
             Re: Fred on the Moon
       Farmers Storm NASA Tracking Station in Australia
             Re: Laser launchers
             Re: Space technology
             Re: Space technology
           Qeustion: OSC's Engineering Dpt. Address
      Re: spacesuits (Was: Re: HST in-orbit Maintenance)
            Re: Launch Technology:
                back-up crews

Administrivia:

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

Date: 9 Apr 91 18:38:17 GMT
From: usc!rpi!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Laser launchers

In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>>If you're willing to settle for 20kg per shot, the laser is still big but
>>is the sort of thing that could reasonably be built as a custom job today.
>>Funding is a much bigger problem than technology.
>
>Even to place a 20 kg payload in orbit would be quite a trick. The only
>laser technology capable of sufficient power is the gas dynamic laser.

Nonsense.  Outfits like Avco will happily build you a CO2 laser of the
required size, if you're willing to pay for it.  (Well, it will be a bank
of lasers rather than a single tube, but the net effect will be the same.)
There is some small risk involved, since it will be an unprecedentedly
large laser, but for a 20kg system it's felt to be a reasonably understood
scaling of existing lasers.

>... It would take at least 100 times
>as much fuel to power such a laser as would be required by a chemical
>rocket to launch the same payload.

The economics of the matter have been studied; they look feasible.  CO2
lasers run on electrical power, not chemical fuels.  The amount of power
needed for a 20kg system is hefty, but not to the point of needing to
build your own power plant.

>And that's if laser launching is
>even possible. The adaptive optics required to deal with the problem
>of atmospheric blooming while handling the enormous power of the beam
>are beyond the current state of the art...

This is not what the LLNL people working on laser launchers say.  SDI, for
all its flaws, has made a lot of progress in things like high-energy optics.
And the beam power for 20kg is not that staggering, especially since it can
be at relatively long wavelengths where the optical problems are easier.

>... The major flaw of laser
>launchers is that they have to deliver all of the power necessary to orbit
>a payload through the thick lower atmosphere for the entire boost phase.

This *is* a nuisance.  Putting the system on a mountaintop would help.

>This incurs a terrible efficiency penalty as well as being incredibly
>loud.

The loud part I'll agree with, especially when the payload is still at
low altitude.  It's manageable.  A rocket is kind of noisy too.

>... Like the chimera of controlled nuclear fusion, they are
>unlikely to deliver any useful results even after hundreds of billions
>of dollars and decades of effort are expended on them.

My my, aren't we negative today? :-)  These systems are somewhat speculative,
but we'd know a whole lot more about how practical they are if we spent, say,
a few hundred million on building and testing prototypes.  The 20kg laser
launcher, win or lose, would not cost billions.

>small clever rockets like Pegasus, and eventually, direct to orbit
>aerospace planes are much more likely to be sucessful at delivering
>payloads to orbit economically and in a realistic timeframe.

Ah, direct-to-orbit aerospace planes.  As Gary Hudson put it, roughly,
"this thing is a cross between the Concorde and the Shuttle and you
think it's going to be cheap and on schedule?".
--
"The stories one hears about putting up | Henry Spencer @ U of Toronto Zoology
SunOS 4.1.1 are all true."  -D. Harrison|  [e-mail]  utzoo!henry

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

Date: 9 Apr 91 18:51:34 GMT
From: eru!hagbard!sunic!mcsun!inesc!unl!unl![e-mail]  (Jose Pina Coelho)
Subject: Re: Fred on the Moon


In article <[e-mail]>
[e-mail] (Henry Spencer) writes:

In article <[e-mail]>
[e-mail] (James Davis Nicoll) writes:
   >    The minimum energy orbit takes, what, about five days?
   Correct.

But you can't have something like a Saturn V fueled, so we have a
minimun of 3 days of trip plus time to get the emergency solutioning
equipment ready and assembled plus(1) time to fuel the beast(2).

Other inconveniences:
  Supplies: the energy difference between getting them into low orbit
  and getting them to the moon is quite big.

  No 0G.

  Basicaly the startup cost is dozens/hundreds of times that of LEO.
  Politics, politics, politics ...

(1) - Nobody is going to start piling things on a fueled rocket.
(2) - How long did it take to fuel them ? Henry ?


--
Jose Pedro T. Pina Coelho   | BITNET/Internet: [e-mail]
Rua Jau N 1, 2 Dto          | UUCP: ...!mcsun!unl!jpc
1300 Lisboa, PORTUGAL       | Home phone: (+351) (1) 640767

- If all men were brothers, would you let one marry your sister ?

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

Date: 9 Apr 91 22:47:38 GMT
From: usc!samsung!munnari.oz.au!yoyo.aarnet.edu.au!sirius.ucs.adelaide.edu.au!levels![e-mail]
Subject: Farmers Storm NASA Tracking Station in Australia

The Advertiser, Monday, April 8, 1991, p.1 writes [comments in square brackets
are my own]

WA [Western Australian] FARMERS STORM US SPACE BASE

   Perth: Angry WA wheat farmers stormed a United States tracking station
yesterday to protest over American wheat subsidies and warned that more
radical action would follow.
   About 100 farmers used chains and tractors to force their way into the
Yaragadee tracking station, near Mingenew, 500 km north of Perth, before
dumping truck loads of wheat.
   Once inside they chained up machinery, painted slogans on a number of US
trucks and buildings, and used used a facsimile machine to send a strongly
worded message to the Prime Minister, Mr. Hawke.
...
   The unmanned tracking station - used by the National Aeronautical and Space
Administration (NASA) to track its space shuttles - is protected only by a
cyclone fence.
...

[Just to fill you in, Australian wheat is currently not subsidised by the the
government and the farmers are seeking subsidies due to losses in sale caused
by the American wheat subsidies]

[Disclaimer: I have absolutely no connection with these farmers]

--
Steven Pietrobon, Australian Space Centre for Signal Processing
School of Electronic Engineering, University of South Australia
The Levels, SA 5095, Australia.          [e-mail]

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

Date: 9 Apr 91 14:09:21 GMT
From: usc!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!wa4mei!ke4zv![e-mail]  (Gary Coffman)
Subject: Re: Laser launchers

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>
>It depends on the size of your payload.  A system to lift manned spacecraft
>would require gigawatt lasers, well beyond the current state of the art.
>If you're willing to settle for 20kg per shot, the laser is still big but
>is the sort of thing that could reasonably be built as a custom job today.
>Funding is a much bigger problem than technology.

Even to place a 20 kg payload in orbit would be quite a trick. The only
laser technology capable of sufficient power is the gas dynamic laser.
If you think the turbopumps on the shuttle main engines are a nightmare,
you should consider the ones needed for a laser launcher. Lasers in general
are very inefficient with less than ten percent of their input power delivered
as usable energy in the beam. It would take at least 100 times
as much fuel to power such a laser as would be required by a chemical
rocket to launch the same payload. And that's if laser launching is
even possible. The adaptive optics required to deal with the problem
of atmospheric blooming while handling the enormous power of the beam
are beyond the current state of the art. The cooling systems for the optics
alone would be enormous. The control systems to drive the optics and
control the laser haven't been designed, and system control for such a
system is much tougher than most folks imagine. The major flaw of laser
launchers is that they have to deliver all of the power necessary to orbit
a payload through the thick lower atmosphere for the entire boost phase.
This incurs a terrible efficiency penalty as well as being incredibly
loud.

Another technique discussed here recently is the railgun. While this
system is feasible for specialized payloads, it has it's own set of
drawbacks. First, it's only suitable for rugged payloads, large solar
arrays are out. Second, there is a substantial mass penalty due to the
required heavy structural components and the heat shield. Third, there
are serious restrictions on the configuration of the payload due to
the necessity of maintaining a high ballistic coefficent. And talk about
loud, the hypersonic shockwave would be an enviornmental disaster. Both
railgun and laser launched payloads will require sophisticated active
guidance systems to achieve anything but a random orbit.

In my view, these technologies are orders of magnitude more complex than
even the shuttle. Like the chimera of controlled nuclear fusion, they are
unlikely to deliver any useful results even after hundreds of billions
of dollars and decades of effort are expended on them. Big dumb boosters,
small clever rockets like Pegasus, and eventually, direct to orbit
aerospace planes are much more likely to be sucessful at delivering
payloads to orbit economically and in a realistic timeframe.

Gary

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

Date: 9 Apr 91 19:01:14 GMT
From: salt.acc.com!opal![e-mail]  (Art Berggreen)
Subject: Re: Space technology

In article <[e-mail]> [e-mail] (Nick A. Bucci) writes:
>
>   I recently got into a "discussion" (argument is a better term) with
>my father about the need for a space program.  Being an old fashioned,
>middle class, construction worker, he disagrees with the concept of
>spending "a lot of money for nothing."  I tried to show him how our
>lives have benifited directly from space exploration:  New products, new
>technology, etc., but he remains unconvinced.
>    I would greatly appreciate any list of products, etc., that came as
>a direct result of the Space program (both U.S. & international).  Maybe
>if I give him enough tangible evidence, I can win him over.
>    Also, let me know if I should post a comprehensive list as one is
>formed.  I apoligize in advance for any errors, I'll just list what I'm
>given, though I'd appreciate feedback on the list so I can correct any
>mistakes.
>    Thanks in advance.
>                -Nick A.Bucci

I feel that it's pretty hard to separate the space program from the entire
technological infrastructure of our modern society.  Each technology tends
to support the development of the others.  Also, don't concentrate just on
the manned space program, a lot of technology has been developed from the
nonmanned sector.  It's also hard to remember exactly how things used to be
before the development of technology that we now take for granted.

As for the cost, all of those dollars are not floating around in space,
they filtered down to a lot of folks through primary, secondary, etc.
jobs and were a significant piece of our economy.  I'd just as soon have
my tax dollars go to these kinds of national efforts than many of the
ways the government has discovered to spend money.

As for specifics, I think the biggest benefits are hard to see because they
are part of our everyday lives rather than being a few specific items.
(Yeah some people point to things like Corning-Ware, Teflon, etc.)
But let's look at things like our communications infrastructure.  We
surely wouldn't have immediate access to world-wide, instantaneous news
(if that's really good ;->),  the wealth of cable TV programming or
the kinds of international telephone service.  It's been stated that
much of the modern biomedical monitoring devices came directly as a
result of the space program.  For all we think of weather forcasts,
things like torneado warnings and hurricane warnings would not be as
good as they are today.

Just a few ramblings....

Art

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

Date: 9 Apr 91 19:42:33 GMT
From: [e-mail]  (Phil OKunewick)
Subject: Re: Space technology

[e-mail] (Art Berggreen) writes:
>I feel that it's pretty hard to separate the space program from the entire
>technological infrastructure of our modern society.  Each technology tends
>to support the development of the others.  Also, don't concentrate just on
>the manned space program, a lot of technology has been developed from the
>nonmanned sector.  It's also hard to remember exactly how things used to be
>before the development of technology that we now take for granted.

   If I remember my childhood and history classes right, the U.S. was
highly intimidated by the USSR putting Sputnik into orbit.  In
response, and partly to get one up on the Soviets, it was decided that
"We can put a man on the moon in this decade."

   One way to get public support for the program was to paint these
daredevels and test pilots as heroes, and televise every significant
achievement.  And it worked - the public _loved_ the space shots.
Allocating a considerable percentage of our national budget was no
problem.

   So, the initial goal of the U.S. space program was manned.  Could
one conclude that the U.S. unmanned space ventures were spinoffs of
the manned space program; therefore all spinoffs are from the manned
program?

   (This cause-and-effect technology stuff is _so_ complicated...)

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

Date: 10 Apr 91 01:03:32 GMT
From: agate!headcrash.Berkeley.EDU![e-mail]  (George William Herbert)
Subject: Qeustion: OSC's Engineering Dpt. Address


    The subject says it all... I need to talk to someone in Orbital
Sciences Corp's engineering department (I need some specs on Pegasus), and
all I've got is their marketing dpt's address (who aren't very helpful...).
Mail/address is preferred.

Thanks,
-george william herbert
[e-mail]

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

Date: 10 Apr 91 01:48:42 GMT
From: agate!headcrash.Berkeley.EDU![e-mail]  (George William Herbert)
Subject: Re: spacesuits (Was: Re: HST in-orbit Maintenance)

In article <[e-mail]> [e-mail] (Fraering Philip) writes:
>Better spacesuits would help your idea and many others as well.
>Any ideas?

Better spacesuits are being worked on.  NASA's funding prioririties, however,
aren't geared towards actually building the new suit ideas.  Both Johnson SC
and Ames groups have demonstrated technology (soft and hard suits respectively)
that would make great space station suits, but it seems like there's only
enough money to rerate the Shuttle suit to 8 PSI (no prebreathe...).

sigh.

[of course, the Mars Spacesuit group is well underway...right on schedule for
our predicted 2020ish launch 8-)  but that's a different story...]

  == George William Herbert ==   * UNIX ate my last .sig, Waiting for Plan 9! *
 == JOAT for Hire: Anything, ==  #########  I do Naval Architecture, ##########
===+++ Anywhere, my price +++=== # Spacecraft Design, UNIX Systems Consulting #
 ==   [e-mail]   ==  # RPG writing/development, and lots of other #
  ==   [e-mail]   ==   ## random stuff, of course.  I'm a JOAT 8-) ##

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

Date: 9 Apr 91 16:15:49 GMT
From: usc!snorkelwacker.mit.edu!thunder.mcrcim.mcgill.edu!bonnie.concordia.ca!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Launch Technology:

In article <[e-mail]> [e-mail] (Donald Heskett) writes:
>... This was achieved with near-satanic propellant combination of
>lithium, fluorine and hydrogen. Does anyone know if any further work
>was ever done with this propellant combination?

I don't think so.  There was a little bit of work done in the 60s on the
slightly more mundane hydrogen-fluorine rockets, but it too went on the
back burner when hydrogen-oxygen was picked for the Saturns.  And all
serious advanced propulsion work died in the post-Apollo cutbacks.

This one doesn't sound very promising to me anyway.  Mixing two liquids
and one solid is not simple, and when two out of three of them have
nasty handling problems, the result is likely to stay a lab curiosity.
Even hydrogen-fluorine was judged to be in that category when the Saturn
planning was being done:  between handling problems, exhaust toxicity,
and the primitive state of engine development, the performance advantage
over hydrogen-oxygen wasn't thought worthwhile.
--
"The stories one hears about putting up | Henry Spencer @ U of Toronto Zoology
SunOS 4.1.1 are all true."  -D. Harrison|  [e-mail]  utzoo!henry

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

Date: 9 Apr 91 19:45:48 GMT
From: [e-mail]  (Adam R. Brody)
Subject: back-up crews

Since they abolished back-up crews since STS 4, what is the plan if
someone gets sick or for some reason cannont make the flight?  How long
before the flight do the crew go into quarantine to prevent catching
someone's cold or the flu?

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

End of SPACE Digest V13 #384
*******************