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Subject: SPACE Digest V13 #385

SPACE Digest                                     Volume 13 : Issue 385

Today's Topics:
             Re: Laser launchers
              Re: SPACE Digest V13 #364
        Re: comsat cancellations and lawsuits
        Re: comsat cancellations and lawsuits
               Voyager CD-ROMs On-Line
            Re: Launch Technology:
        Re: comsat cancellations and lawsuits
            SPACE Digest V13 #377
             Re: Space technology

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
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----------------------------------------------------------------------

Date: 9 Apr 91 19:17:52 GMT
From: sun-barr!newstop!exodus!concertina.Eng.Sun.COM![e-mail]  (Steve Hix)
Subject: Re: Laser launchers

In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>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.

Shouldn't that be "currently capable"?

Free-electron lasers have been listed fairly commonly as potential future
laser launch candidates.

So far, any type of laser is still only a candidate for laser launch system.





--
------------
  The only drawback with morning is that it comes
    at such an inconvenient time of day.
------------

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

Date: 8 Apr 91 22:20:44 GMT
From: orca!bambam![e-mail]  (Bob Pendleton)
Subject: Re: SPACE Digest V13 #364

In article <[e-mail]>, [e-mail] writes:
> >I agree that chemical rockets haven't much future beyond LEO. But I'm
> >rather fond of fission torch rockets myself. I want to get there NOW,
> >not next year. :-)
>
> But where can you go?  You certainly won't be using fission in MY back
> lagrange point (oops, I mean yard) |-)
>
> Actually, with Ion systems, since the ISP is so high, you can accelerate for
> the entire trip.  Toward your destination at first, and slowing down
> after the half-way point.  You'll start out at only a few meters/minute, since
> the amount of mass is so low.  But after a day you'll be moving 76400 times
> faster.  after a week, 534800 times, and after a year, 2.7e+7 times. (.90c)
> This is all ignoring relativity, of course.   As an example, at .9c, a trip to
> Alpha Cent. would appear (th those on earth) to take 4.4 years.  But you would
> feel like it only took about 2.5 years.  That's 2 times the speed of light!

Right, I've read a high school physics text too. :-) Trouble is that
you still have to get the energy to do all that accelerating from
somewhere. If you use a nuclear reactor to generate the electricity
for your ion rocket you have to convert the heat to electricity, use
the electricity to accelerate the ions and dispose of the waste heat.

Lots of weight added for radiators. Very low thrust. Slow. I don't
like it.

Now the fission torch aka the gas core nuclear reactor is a whole
'nuther matter.  The reactor is uranium hexafloride gas mixed with
hydrogen gas. The fission heat is transfered directly to the hydrogen
by collisons between the fission products and the hydrogen. Everything
flows out the nozzle producing thrust.

High thrust. No radiators. Fast.


>
> Either way, I hope it happens soon enough for me to see it.
>
> Tommy Mac
> 18084tm@msu
> Acknowledge-To: <18084TM@MSU>

--
              Bob Pendleton, speaking only for myself.
   [e-mail] or decwrl!esunix!bpendlet or utah-cs!esunix!bpendlet

                         Tools, not rules.

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

Date: 9 Apr 91 19:41:54 GMT
From: sdd.hp.com!usc!rpi!uupsi!pbs.org![e-mail]
Subject: Re: comsat cancellations and lawsuits

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
>
> As I said in my original posting:  there was ample cause to *renegotiate*
> the shuttle launch contracts, perhaps shifting them to expendables.  That's
> not what happened.
> --
How can you *renegotiate* a shuttle launch contract to launch something the
shuttle is now *prohibited* from launching?

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

Date: 9 Apr 91 13:22:24 GMT
From: fernwood!uupsi!pbs.org![e-mail]
Subject: Re: comsat cancellations and lawsuits

In article <[e-mail]>, [e-mail] (Michael V. Kent) writes:
> In article <[e-mail]> [e-mail] writes:
>>Considering passed performances and some questionable over charging, I'm
>>not sure that Hughes or any other aerospace firm has a "right" to be ticked
>>off.  Call it poetic justice.  This law suit, no matter who wins, is going to
>>cost the U.S. taxpayer.  Since Henry is Canadian he doesn't have to worry,
>>though. :-)
>
> Hughes -- and any other firm for that matter -- has a right to be ticked off
> anytime they are given a raw deal, whether it is by the U. S. government or
> another private organization.  Although I would not like to see space
> exploration reduced because of such a lawsuit, it might be worth it if the
> U. S. government starts respecting its own law.
>
It has not yet been established that a raw deal has in fact occurred in this
situation.  Even if it has it could be a bit counter productive for Hughes to
make too big a stink.  There are future contracts to be awarded down the road.
How much do want to bet that if Hughes and another company are the finalists
AND their proposals are ABOUT EVEN, the other company gets it because they are
not Hughes.

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

Date: 8 Apr 91 05:58:36 GMT
From: snorkelwacker.mit.edu!usc!elroy.jpl.nasa.gov!jato!kelvin.jpl.nasa.gov![e-mail]  (baalke, ron)
Subject: Voyager CD-ROMs On-Line


     Peter Yee and I are pleased to announce a major addition to the SPACE
archive at NASA Ames Research Center.

     There are eight CD-ROMs that contain about 16,000 images taken by
Voyager 1 and Voyager 2 on their encounters with Jupiter, Saturn and Uranus.
Images from these Voyager CD-ROMs are now available on-line at the Ames SPACE
archives.  A CD-ROM drive has been installed at the Ames site allowing direct
access to the CD-ROM via anonymous ftp to ames.arc.nasa.gov (128.102.18.3).
The images are in the /pub/SPACE/CDROM directory.  The plan is to rotate
the CD-ROMs on a weekly basis.  The first CD-ROM currently on-line is the
Voyager Saturn Encounter, Volume 4.  A new Magellan CD-ROM and three new
Neptune CD-ROMs are also available, and will be quickly be placed on-line when
Peter receives them.

     The Voyager images are stored in compressed format on the CD-ROM with each
compressed image being about 220K.  Source code for the decompression program,
decomp.c, is available on the CD-ROM.  When the images are uncompressed, they
will be about 670K in size, so a large hard disk is recommended.  An IBM PC
version of the decompression program, PCDCOMP, and an image display program
that also runs on an IBM PC computer, IMDISP, are also stored at the Ames site.
The most recent versions of the PCDCOMP (version 2.0) and IMDISP (version 5.6)
programs can obtained from pub/SPACE/SOFTWARE directory under the filename
imdisp56.zip.

     The CD-ROMs are also available to the general public from the NSSDC
(National Space Science Data Center) at the Goddard Space Flight Center.
You can contact the NSSDC at:

        National Space Science Data Center
        Request Coordination Office
        Goddard Space Flight Center
        Code 633
        Greenbelt, MD  20771

        Telephone: [phone]

        Email address:   [e-mail]


We would like to thank the following people and organizations:

Dr. Bradford A. Smith, Team Leader, Voyager Project
Planetary Data System, Jet Propulsion Laboratory
National Space Science Data Center, Goodard Space Flight Center
Randall Robinson, NASA Ames Research Center Communications Operations Branch
------------------------------------------------------------------------------

      ___    _____     ___
     /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
     | | | |  __ \ /| | | |     Jet Propulsion Lab |
  ___| | | | |__) |/  | | |__   M/S 301-355        | Change is constant.
 /___| | | |  ___/    | |/__ /| Pasadena, CA 91109 |
 |_____|/  |_|/       |_____|/                     |

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

Date: 9 Apr 91 14:47:58 GMT
From: sun-barr!olivea!samsung!zaphod.mps.ohio-state.edu!caen!news.cs.indiana.edu!maytag!watmath!watdragon!watyew![e-mail]  (James Davis Nicoll)
Subject: Re: Launch Technology:

In article <[e-mail]> [e-mail] (Donald Heskett) writes:
>The book "Ignition!" (written in the '60s, I think) mentioned that the
>highest specific impulse that had been achieved at that time was 542
>seconds. 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?
>
>Needless to say, 1) it's probably not a good idea to operate
>fluorine-fueled propulsion systems in proximity to population areas or
>the ozone layer and 2) it's not a good idea to carry this stuff in
>the Shuttle's payload bay.  The combination would only seem to make
>sense in the upper stage of an expendable launcher.

    What's the cost per tonne of lithium, fluorine and hydrogen,
what's the cost of storing and using them and how do those two costs
compare to the costs associated with standard fuels? A wild guess might
that the higher Isp is nice, but that the problems of handling fluorine
drove costs up above the level of standard fuels.

                            James Nicoll

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

Date: 9 Apr 91 16:53:01 GMT
From: news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: comsat cancellations and lawsuits

In article <[e-mail]> [e-mail] writes:
>It should also be remembered the White House Commission set up to study the
>CHALLENGER disaster and suggest remedial action, included representatives from
>the aerospace industry.  It was the Commission's suggestion that comsat
>launches, among other activities, be taken away from the space shuttle...

As I said in my original posting:  there was ample cause to *renegotiate*
the shuttle launch contracts, perhaps shifting them to expendables.  That's
not what happened.
--
"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

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

ReSent-Message-ID: <[e-mail]>
Resent-Date:  Tue, 09 Apr 91 17:39:25 EDT
Resent-From: TommY Mac <[e-mail]>
Resent-To: [e-mail]
Date:         Tue, 9 Apr 91 01:53:05 EDT
Reply-To: [e-mail]
From: [e-mail]
Subject:      SPACE Digest V13 #377
Comments: To: [e-mail]
To: david polito <[e-mail]>, Tom McWilliams <[e-mail]>

Subject: Re: Fred on the Moon

>>   I think it sounds like a great idea.  Other Advantages:
>>
>>   Radio telescopes; far side:  No interference from microwaves, tv, etc
>>   Interferometry;   base line of 450000km possible
>>   (one on earth, one on moon)

>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^ And how do they compare the data ?
>From the far site it is *hard* to see earth

The same way any interferometer does.  By comparing signals read at the same
times.  Or were you arguing about the details of a *speculatory* enterprise.

>>  Space Telescope; All the advantages of atmospherelessness and no drawbacks,
>>                    like frequent temp changes and oscillations.

>They don't need to be frequent, they just need to be the direct
>irradiation to space alternated every 14 days with direct sunlight
>(And I think you'll have to re-calibrate the whole thing every 14
>days.)

Unless you do something really radical, like putting it in a dome.

>>   Inter planetary launches;  even better speeds than the equator, not to ment
   on
>>                             the lower energy to escape.

>That's not Fred, that's a FULL moon colony with the capacity to
>produce fuel and rocket's etc ...

And you beleive, perhaps, that we should use 'FRED ON THE MOON' till it breaks,
and then come home and forget the whole thing?

>>   BEST REASON:   We'd be on our way to building a Mining/Production/Energy-
>>                 harvesting Space Infrastructure.

>WORST REASON:
>Emergency: 3 days to get some kind of assistance from earth. (Assuming
>something as energetic as a saturn V is fueled and on launch pad)

Or, assuming there's a bailout shuttle ON THE MOON, or L5, or in Lunar orbit.

As long as you want to think up the worst case scenario, here's the best case:

Step 1:  Fred gets built, has a few screw-up, takes too long, but noone dies
step 2:  It begins R&D on the mining of iron, oxygen, silica
Step 3:  Initial successes cause a stock option to sell at 4 times asking
Step 4:  With it's new industrial capacity, moon begins building more space
         on the surface, rail-launcher, greenhouses, etc
Step 5:  Moon becomes self-sufficient, exports material, energy, etc
Step 6:  Space bases around the planets become the great ports to the heavens
Step 7:  Large ships and colonies start getting built.  Exploration beyond the
         solar system starts.  More people now live off the planet, than on.
Step 8:  Huge immigration begins, allowing the greatest range of human freedom
         ever known or imagined, since you can always go somewhere else.
Step 9:  Some geek complains becuase he thinks it's a waste to try to get to
         the magellenic clouds.  "we've never done that before"

It's amazing what you can do if you really drop the reins on a 'what if..' sort
of argument, huh?

Tommy Mac
18084tm@msu
Acknowledge-To: <18084TM@MSU>

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

Date: 10 Apr 91 00:55:33 GMT
From: [e-mail]  (Eugene Miya)
Subject: Re: Space technology

RE: Constructor worker's son skeptical of space.

I am seeing this in the geology group (as I don't have time to
read space anymore).  My Dad, an architect (deceased) and a stauch
Republican (private enterprise business) also believed like your father
(my Dad  also wanted to nuke Russia, but that's another story).

As far am I am concern, we live in the space age.  Perhaps the
most pervasive argument I can think is that of weather satellites
which affects the lives of construction workers and architects.
The next time, during hurricane season, suggest to him:
"Let's turn off the weather satellite."

It's kind of an extreme example, but I can remember the days before
those satellites.  Our forecasts ARE more accurate, the data goes
into prorgams for forecasting.  When your Dad realizes, we should
let those folk in the path die, maybe he will wake up.
Skinner called this behavior by consequences.  We have a short memory.

We have a situation of some truth: our satellites are dying slowly.
We are doing too good a job to patch the situation up.  Given time,
we will revert to a new sort of stone age.  We could do the same for
communications satellites.  Maybe we need to charge more for research
and development issues.  Complex issues, not space related.

--e.n. miya, NASA Ames Research Center, [e-mail]
  Resident Cynic, Rock of Ages Home for Retired Hackers
  {uunet,mailrus,most gateways}!ames!eugene

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

End of SPACE Digest V13 #385
*******************