Message-ID: <4c3xYYa00WBwQaUk5y@andrew.cmu.edu>
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Date: Sat, 20 Apr 91 02:01:09 -0400 (EDT)
Subject: SPACE Digest V13 #431

SPACE Digest                                     Volume 13 : Issue 431

Today's Topics:
			Transportation Tethers
		 Re: Questions about pioneer/Voyager
		   Re: Advancing Launch Technology
			 Re: Laser launchers
		  NASA Prediction Bulletins, Part 1

Administrivia:

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

Date: 16 Apr 91 17:14:33 GMT
From: unisoft!fai!sequent!crg5!szabo@ucbvax.Berkeley.EDU  (Nick Szabo)
Subject: Transportation Tethers

In article <HESKETT.91Apr15124737@polymnia.titan.tsd.arlut.utexas.edu> heskett@titan.tsd.arlut.utexas.edu (Donald Heskett) writes:

>Could you explain what you mean by "tethers"? (Sorry if it has been
>hashed and re-hashed

Unfortuneately, it has been neither hashed nor rehashed.  So, in the
hopes that it will be, here are some possible transportation tether 
configurations:

* A "tether" is simply a cable or wire of material with high tensile 
  strength used for structural or momentum transfer purposes.   A LEO 
  tether rotates, hooking a launched payload and accelerating it from 
  suborbital to orbital trajectory, while decellerating a similar 
  payload into the earth's atmosphere.  This counterweight could be a 
  dead satellite, a payload needing reentry, or a piece of captured 
  asteroid or comet.  This reduces the cost of the ground launcher by 
  over 2/3, since we can now use something like the Starbird to merely 
  poke our head above the atmosphere, rather than building large launchers 
  to go all the way into orbit by themselves.

* A tether can be used on an airplane to swing a payload carried by that
  airplane into a suborbital  trajectory.  The payload can then be swung
  into orbital trajectory by a LEO tether.  This was proposed by Keith
  Henson.

* Given a medium-sized comet or carbonaceous chondrite asteroid captured 
  into GEO and a mature space manufacturing industry, a Kevlar "beanstalk" 
  might be built from GEO all the way to the Earth's surface.  The 
  operational cost of this would not be much more than the energy cost of 
  elevators riding up and down this structure (about $4/kg).  

* Tethers can be used in deep space for various OTV purposes, for example
  in getting materials between asteroids.  Given two asteroids opposite
  directions from earth, LEO, and a tether at each, we can launch payloads 
  between these three locations with a near zero energy cost.   We need to 
  arrange the orbital trajectories from the asteroid, and schedule the 
  payloads, so that the incoming payload's cumulative effects on the LEO 
  tether orbit balance out.  With more sophisticated scheduling, we can 
  also use the incoming mass to boost payloads such as mining equipment 
  from LEO to the asteroid, also at near zero energy cost.

The main research problems are creating high-tensile, low mass fibers
beyond Kevlar for such structures, and learning how to manufacture them
from space materials.

I am sure there are other possibilities along these lines which I haven't
heard of.  Tethers, like gravity assist and aerobraking, are another good
example of substituting brain power for rocket power -- letting the solar
system do the work for us.



-- 
Nick Szabo			szabo@sequent.com
"The biscuits and the syrup never come out even" -- Robert A. Heinlein
The above opinions are my own and not related to those of any
organization I may be affiliated with.

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

Date: 16 Apr 91 16:11:50 GMT
From: unisoft!fai!sequent!crg5!szabo@ucbvax.Berkeley.EDU  (Nick Szabo)
Subject: Re: Questions about pioneer/Voyager

In article <1991Apr14.180423.29686@kuhub.cc.ukans.edu> utagikar@kuhub.cc.ukans.edu writes:

[Pioneer/Voyager to Jupiter etc. questions]

>1) How was the collision with astroid belts avoided?

Other than minimal micrometeorite protection, no precautions were taken.
Space is _big_ and it turns out that even the millions of rocks in the
asteroid belt are easy to miss.  This wasn't clear when the first Pioneer
went to Jupiter, though, so there was a lot of figurative breath-holding
when it passed through the belt.

Galileo will intentially steer towards the asteroids Gaspra and Ida 
on the way to Jupiter to get a closer look.  Good idea -- asteroids are 
important for both space science and space development.


>2) How were/are they powered? If with nuclear power; how come NASA
>doesn't quote its sucess to the people demonstrating against nuclear
>powered crafts?

Plutonium radioisotope thermal generators (RTG's).  There was little 
controversy about this until the Galileo launch in 1990, for which NASA 
was taken to court by the Christic Institute and Jeremy Rifkin, largely 
to gain publicity for the latter groups.  The judge soon threw it out.  
I find it hard to believe that NASA did not point out the success of 
Pioneer and Voyager during that court battle.


>3) People who must have watched "First Contact" the episode in
>Star Trek The Next Gen might recollect the government making the
>decision on whether to disclose the contact.. Now considering Earth
>with many different countries/governments, who made the decisions on
>revealing our presence and technological prowess? 

The decision to make contact was made by the folks who set up all
the high-power TV stations.  Seriously, there is no way to control
who contacts whom on this end, at least.  There are idealists who are
sure that ETI will be benevolent and are eager to send out our signature
to the cosmos.  Others would try to arrange things so that we find out
about them before they find out about us.   Either way, SETI is not
taken seriously enough by governments for this issue to be a significant
concern.


-- 
Nick Szabo			szabo@sequent.com
"The biscuits and the syrup never come out even" -- Robert A. Heinlein
The above opinions are my own and not related to those of any
organization I may be affiliated with.

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

Date: 19 Apr 91 13:01:36 GMT
From: agate!bionet!uwm.edu!caen!ox.com!hela!aws@ucbvax.Berkeley.EDU  (Allen W. Sherzer)
Subject: Re: Advancing Launch Technology

In article <21561@crg5.UUCP> szabo@crg5.UUCP (Nick Szabo) writes:

>I am sorry it violates your wishes.  Now sit down, get the data for 
>launch costs between 1957-1991, and fit the curve for yourself.

Perhaps you could give us the figures you are using and the sources? Ever
since you incorrectly claimed that Titan was more expensive per pound than
Delta I have been wondering where you get your numbers.

   Allen
-- 
+-----------------------------------------------------------------------------+
|Allen W. Sherzer | If you love something, let it go. If it doesn't come back |
|   aws@iti.org   | to you, hunt it down and kill it.                         |
+-----------------------------------------------------------------------------+

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

Date: 19 Apr 91 17:28:27 GMT
From: agate!bionet!uwm.edu!wuarchive!rex!rouge!dlbres10@ucbvax.Berkeley.EDU  (Fraering Philip)
Subject: Re: Laser launchers

In article <2753@ke4zv.UUCP> gary@ke4zv.UUCP (Gary Coffman) writes:

>I wasn't arguing that R&D engineering problems need to be solved so
>much as I was arguing that fundamental physical laws prevent the system 
>from being a practical, efficient, alternative to rockets. We could
>throw hundreds of billions into an R&D engineering program to develop
>anti-gravity too, but fundamental physical laws would have to be broken
>for it to pay off. At the power levels required to loft real payloads
>into orbit, atmospheric blooming is an intractable physical problem.
>Once the air is ionized into a plasma, the plasma is optically opaque
>cutting off further power transfer. Talk to the guys who have actually
>fired high power lasers, the laser fusion folks, and see what they
>say about the absolute necessity of having a hard vacuum to fire the
>beam through.

Oh boy, here we go again. Nick, does that phrase "intractable physical
problem" look familiar to you? 

Did everyone notice in his post how he said the only laser that could
do it is the gas dynamic (and that the CO2 has intractable cooling
problems?) and that the implosion fusion program experience seems to
indicate that laser launching is impossible?

Well, here I go:

1. The cooling problem of CO2 lasers is probrably not nearly as bad as
is currently solved in the current generation of rocket engines, and a
CO2 cooling system on the ground wouldn't have the weight penalties.
For that matter, back when Robert Bussard was trying to build cheap
and dirty fusion reactors, he had an 'intractable cooling problem'
too. If I recall right, however, it was the only problem he really
solved. 

2. The beam intensities needed by the implosion people is probrably
higher than what you would find in a laser propulsion system. I recall
that the beam is focused in the propulsion chamber on several designs
to an intensity where blooming takes place, and the beam is blocked,
keeping the chamber walls from being illuminated by the laser's full
force (uncertianty alert!)

3. There are several different ways of building a laser propulsion
system. If it really needs to go to vacuum, let's put it in vacuum:
You put the laser in orbit, and use it to accelerate the upper stages
of a suitable launch vehicle to orbital velocity. All the lower stages
have to do is put the payload and laser motor up to where the
atmospheric blooming is no longer a problem, and the rest is left as
an exercise for the reader. I know that sun-pumped lasers in orbit
have been proposed.

4. And now the most important point: fnord




fnord.

So you see, building a laser launcher is easy, fun, and profitable.
Send your investment money, preferably in large cash denominations, to...
:-) :-) :-) :-)




--
Phil Fraering
dlbres10@pc.usl.edu
"The Soviet Union has neither soviets nor unions." - Eric Hoffer in 1974.

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

Date: 20 Apr 91 00:42:52 GMT
From: udecc.engr.udayton.edu!blackbird.afit.af.mil!tkelso@tut.cis.ohio-state.edu  (TS Kelso)
Subject: NASA Prediction Bulletins, Part 1


The most current orbital elements from the NASA Prediction Bulletins are
carried on the Celestial BBS, (513) 427-0674, and are updated several times
weekly.  Documentation and tracking software are also available on this
system.  As a service to the satellite user community, the most current of
these elements are uploaded weekly to sci.space.  This week's elements are
provided below.  The Celestial BBS may be accessed 24 hours/day at 300,
1200, or 2400 baud using 8 data bits, 1 stop bit, no parity.

- Current NASA Prediction Bulletins #837a -
Alouette 1 
1 00424U 62B-A  1 91102.16227732  .00000403  00000-0  47023-3 0  3971
2 00424  80.4702 351.3044 0021773 224.7920 135.1386 13.67508692423552
ATS 3      
1 03029U 67111  A 91 99.79553794 -.00000076  00000-0  99999-4 0  5200
2 03029  13.5673  18.6770 0017280 228.8932 130.9740  1.00272933 85769
Cosmos 398 
1 04966U 71 16  A 91108.46825889  .00125583  19526-4  61577-3 0  5704
2 04966  51.5029 163.0806 2053127  25.3519 343.5150 11.53567171626088
Starlette  
1 07646U 75010  A 91 98.35919790  .00000036  00000-0  75551-4 0  2029
2 07646  49.8200  73.7602 0205614  86.2479 276.1896 13.82154507816603
LAGEOS     
1 08820U 76039  A 91102.35471075  .00000005  00000-0  99999-4 0  2209
2 08820 109.8367  97.6155 0044262 174.8990 185.1807  6.38664302 93047
GOES 2     
1 10061U 77048  A 91101.78169883 -.00000257  00000-0  99999-4 0  5806
2 10061   8.7702  60.1271 0003940  21.8864 338.1519  1.00254745 52001
IUE        
1 10637U 78012  A 91 98.90692571 -.00000180  00000-0  79862-4 0  2248
2 10637  32.7698 114.0796 1408565   1.1900 359.2080  1.00287730  9433
GPS-0001   
1 10684U 78020  A 91101.10802193  .00000004  00000-0  99999-4 0  6150
2 10684  63.8990  80.3210 0127367 200.4223 159.0745  2.00553485 81821
GPS-0002   
1 10893U 78 47  A 91100.11242070 -.00000022  00000-0  99999-4 0  3375
2 10893  64.2312 321.2043 0172427  23.9267 336.9049  2.00533682 94622
GOES 3     
1 10953U 78062  A 91106.09771458  .00000101  00000-0  99999-4 0   621
2 10953   7.6692  62.7145 0004509  98.4289 261.5901  1.00285530   113
SeaSat 1   
1 10967U 78064  A 91102.30722896  .00002008  00000-0  72557-3 0  4903
2 10967 108.0153 217.8309 0003072 223.1321 136.9680 14.36462424669391
GPS-0003   
1 11054U 78093  A 91 98.85784464 -.00000021  00000-0  99999-4 0  3628
2 11054  63.7466 317.3902 0064432 116.8109 243.8969  2.00572320 91614
Nimbus 7   
1 11080U 78098  A 91 99.75409735  .00000223  00000-0  23130-3 0  7391
2 11080  99.1734   2.6496 0009330  15.0547 345.0882 13.83534068629041
GPS-0004   
1 11141U 78112  A 91101.47731067  .00000004  00000-0  99999-4 0  1461
2 11141  63.8332  80.1746 0061474 311.4816  47.9903  2.00546280 90364
GPS-0005   
1 11690U 80 11  A 91100.11889813  .00000005  00000-0  99999-4 0  1083
2 11690  64.3401  82.5110 0123254 203.0580 156.4258  2.00552430 96196
GPS-0006   
1 11783U 80 32  A 91 95.92533111 -.00000021  00000-0  99999-4 0  4068
2 11783  63.5636 316.9772 0162889  59.3932 302.2320  2.00576960 80196
GOES 5     
1 12472U 81049  A 91 98.04615071  .00000136  00000-0  99999-4 0   663
2 12472   4.2014  72.1400 0003117 282.6346  77.4892  1.00252445 35183
Cosmos 1383
1 13301U 82 66  A 91 94.01230107  .00000267  00000-0  30280-3 0  6939
2 13301  82.9292  87.6399 0029159  78.0258 282.4149 13.67901179437435
LandSat 4  
1 13367U 82 72  A 91101.49171165  .00001277  00000-0  29286-3 0  7349
2 13367  98.1340 162.4737 0002403 318.4307  41.5649 14.57168420464744
IRAS       
1 13777U 83  4  A 91 98.04024139  .00000354  00000-0  26878-3 0  9132
2 13777  99.0138 295.0951 0012066 296.1180  63.8750 13.98920624 88166
Cosmos 1447
1 13916U 83 21  A 91102.18198900  .00000234  00000-0  23571-3 0  7890
2 13916  82.9456 151.0215 0039715  27.4985 332.8244 13.74132163403735
TDRS 1     
1 13969U 83 26  B 91102.09494060  .00000127  00000-0  99999-4 0  3029
2 13969   5.1952  63.1215 0003509 328.3069  31.6948  1.00276849  2345
GOES 6     
1 14050U 83 41  A 91101.03196172  .00000113  00000-0  99999-4 0  3984
2 14050   2.9783  74.7008 0001160 303.1214  57.1540  1.00282225  1127
OSCAR 10   
1 14129U 83 58  B 91 97.32732770  .00000024  00000-0  99999-4 0  6462
2 14129  25.8493 151.9623 6008503 231.4593  58.2833  2.05882614 30790
GPS-0008   
1 14189U 83 72  A 91 98.84920780  .00000003  00000-0  99999-4 0  9079
2 14189  63.5206  78.5948 0143419 225.3179 133.5023  2.00568376 56699
LandSat 5  
1 14780U 84 21  A 91108.66838580  .00000427  00000-0  99999-4 0  6212
2 14780  98.2380 169.8199 0005504 168.8677 191.2646 14.57108271379208
UoSat 2    
1 14781U 84 21  B 91108.60790668  .00004729  00000-0  85566-3 0  9969
2 14781  97.9080 155.6266 0012633   7.3169 352.8348 14.66747077380719
GPS-0009   
1 15039U 84 59  A 91 96.03099321  .00000002  00000-0  99999-4 0  1797
2 15039  63.2702  77.7993 0028346 227.0133 132.7493  2.00565525 49915
Cosmos 1574
1 15055U 84 62  A 91106.71270673  .00000318  00000-0  33011-3 0   439
2 15055  82.9614 198.5420 0026787 195.5239 164.5101 13.73444883341732
GPS-0010   
1 15271U 84 97  A 91101.95929275 -.00000021  00000-0  99999-4 0   246
2 15271  63.0471 316.1858 0112634 332.4467  27.0237  2.00564691 47147
Cosmos 1602
1 15331U 84105  A 91101.99618395  .00006628  00000-0  86677-3 0  5235
2 15331  82.5354  83.6497 0024656  76.0288 284.3674 14.80115320352259
NOAA 9     
1 15427U 84123  A 91102.28360107  .00000955  00000-0  53396-3 0  7252
2 15427  99.1729 114.2159 0014121 248.7678 111.1989 14.12944064326211
GPS-0011   
1 16129U 85 93  A 91 99.18533417  .00000003  00000-0  99999-4 0  7387
2 16129  64.0418  78.9192 0122971 147.7498 213.0202  2.00564741 40296
Mir        
1 16609U          91107.85243023  .00080629  00000-0  81916-3 0  3804
2 16609  51.6067 233.4307 0010040 120.4867 239.7062 15.64417562295695
SPOT 1     
1 16613U 86 19  A 91102.74200439  .00001385  00000-0  66853-3 0  2860
2 16613  98.6955 177.8183 0002034  69.5548 290.5845 14.20015950106447
Cosmos 1766
1 16881U 86 55  A 91102.09729676  .00004628  00000-0  61353-3 0  3778
2 16881  82.5255 142.2634 0023067  91.2586 269.1663 14.79497609253317
EGP        
1 16908U 86 61  A 91 97.19363411 -.00000043  00000-0 -30202-4 0  3443
2 16908  50.0083  72.1433 0011329 223.6359 136.3561 12.44393894211464
NOAA 10    
1 16969U 86 73  A 91 97.93691543  .00001129  00000-0  50757-3 0  5672
2 16969  98.5720 123.9135 0014050 129.2742 230.9686 14.24039231236559
MOS-1      
1 17527U 87 18  A 91108.71213158 -.00000022  00000-0 -33126-5 0  8213
2 17527  99.0731 181.8043 0003907  10.1253 350.0261 13.94872872211854
GOES 7     
1 17561U 87 22  A 91 98.75349979 -.00000045  00000-0  99999-4 0  7547
2 17561   0.0537 120.5656 0007317 286.6767 312.8294  1.00272554  8533
Kvant-1    
1 17845U 87 30  A 91108.68282024  .00073000  00000-0  73933-3 0  5718
2 17845  51.6057 229.2136 0009666 118.6038 241.5881 15.64543445230577
DMSP B5D2-3
1 18123U 87 53  A 91102.89041825  .00001345  00000-0  72014-3 0  8964
2 18123  98.8153 294.4855 0013557 250.2382 109.7330 14.14502568196769
RS-10/11   
1 18129U          91107.90229248  .00000521  00000-0  56128-3 0  5860
2 18129  82.9219 103.4085 0011775   1.9123 358.2087 13.72176641191329
Meteor 2-16
1 18312U 87 68  A 91106.88724636  .00000366  00000-0  32139-3 0  6235
2 18312  82.5533  49.5731 0013275 113.0284 247.2280 13.83767496184988
Meteor 2-17
1 18820U 88  5  A 91106.46001087  .00000189  00000-0  15809-3 0  4712
2 18820  82.5405 109.3736 0015812 187.6611 172.4317 13.84469815162149
DMSP B5D2-4
1 18822U 88  6  A 91102.95451567  .00001455  00000-0  67610-3 0  8333
2 18822  98.6045 340.1762 0007581 118.1611 242.0338 14.21933682165416
Glonass 34 
1 19163U 88 43  A 91101.59514302  .00000020  00000-0  99999-4 0  2257
2 19163  64.9161 149.1941 0007175 201.8186 158.2458  2.13102739 22504
Glonass 36 
1 19165U 88 43  C 91101.65199750  .00000020  00000-0  99999-4 0  2162
2 19165  64.8912 149.1814 0005346 319.8173  40.2355  2.13102997 22504
AO-13      
1 19216U 88 51  B 91 78.38609337  .00000215  00000-0  44351-3 0  2424
2 19216  56.8112 104.6916 7140389 249.8316  25.0884  2.09695125 21173
OKEAN 1    
1 19274U 88 56  A 91102.22969024  .00005506  00000-0  74687-3 0   865
2 19274  82.5136 240.8774 0020219 224.0264 135.9793 14.78617279149087
Meteor 3-2 
1 19336U 88 64  A 91101.92664892  .00000121  00000-0  29681-3 0  7199
2 19336  82.5444  66.0743 0016059 288.9946  70.9502 13.16919571130273
Glonass 39 
1 19503U 88 85  C 91102.14100201 -.00000018  00000-0  99999-4 0  1428
2 19503  65.4541  28.5082 0004507 197.9840 162.0067  2.13103614 20009
NOAA 11    
1 19531U 88 89  A 91 99.26633402  .00001228  00000-0  69016-3 0  4775
2 19531  99.0242  53.5690 0012222 164.8291 195.3252 14.12059942130744
TDRS 2     
1 19548U 88 91  B 91 97.94047857  .00000114  00000-0  99999-4 0  2362
2 19548   0.8528  80.4427 0001776 287.8629 351.6825  1.00276298  7877
Glonass 40 
1 19749U 89  1  A 91102.18244873  .00000020  00000-0  99999-4 0  9270
2 19749  64.8596 148.8338 0007247 274.0599  85.9462  2.13102027 17539
Glonass 41 
1 19750U 89  1  B 91102.24053305  .00000020  00000-0  99999-4 0  9806
2 19750  64.8804 148.8565 0007357 256.7635 103.2498  2.13102416 17530
GPS BII-01 
1 19802U 89 13  A 91 58.17527061  .00000017  00000-0  99999-4 0  2319
2 19802  55.0455 187.3559 0050904 163.2354 196.8890  2.00558153 14865
Akebono    
1 19822U 89 16  A 91101.96661259  .00043357  00000-0  23984-2 0  9891
2 19822  75.0846  90.5502 4100135  28.4707 348.9686  7.26602355 21280
Meteor 2-18
1 19851U 89 18  A 91106.72821041  .00000464  00000-0  40683-3 0  4243
2 19851  82.5248 346.6084 0012671 233.9489 126.0499 13.84119466107553
MOP-1      
1 19876U 89 20  B 91 83.49540771  .00000025  00000-0  99999-4 0  1840
2 19876   0.2910  50.4188 0001552 314.1531 355.4087  1.00273956  3471
TDRS 3     
1 19883U 89 21  B 91104.55447587 -.00000237  00000-0  99999-4 0  2376
2 19883   0.8772  77.6129 0041876 329.3605 313.6292  1.00271603 77911
GPS BII-02 
1 20061U 89 44  A 91 58.00437706 -.00000034  00000-0  99999-4 0  2332
2 20061  54.8640   5.4895 0089842 183.4176 176.5173  2.00566400 12602
Nadezhda 1 
1 20103U 89 50  A 91106.84603771  .00000296  00000-0  30378-3 0  3176
2 20103  82.9586  61.1570 0036160 274.3790  85.3247 13.73678121 89403
GPS BII-03 
1 20185U 89 64  A 91 57.34599602  .00000016  00000-0  99999-4 0  1766
2 20185  54.8906 188.1900 0021289 164.8064 195.2144  2.00568043 11161
GPS BII-04 
1 20302U 89 85  A 91 41.91577973 -.00000024  00000-0  99999-4 0  1785
2 20302  54.4598 307.3315 0032510 329.9999  29.8633  2.00556091  9656
-- 
Dr TS Kelso                           Assistant Professor of Space Operations
tkelso@blackbird.afit.af.mil          Air Force Institute of Technology

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

End of SPACE Digest V13 #431
*******************