Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V09_3/V9_359.TXT

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Date: Wed, 12 Apr 89 00:18:39 -0400 (EDT)
Subject: SPACE Digest V9 #359

SPACE Digest                                      Volume 9 : Issue 359

Today's Topics:
         Soviet Mir space station in trouble
               Gigantism of SPS
         Assaying likely asteroids from afar
           Re: Assaying likely asteroids from afar
        Re: Success with cold fusion reported
               Reminders for Old Farts
              Re: Hubble Space Telescope
         jim benz and kicking us off dis heah planet
        Re: more on Liberty Bell 7 (and other s'craft)
       Re: far side of the Moon photo mission (ussr's)
       constant-boost fusion spaceships, power requirements of
----------------------------------------------------------------------

Date: Tue, 11 Apr 89 23:57:37 EDT
From: Glenn Chapman <[e-mail]>
To: [e-mail], [e-mail],
        [e-mail]
Subject: Soviet Mir space station in trouble

     The Soviet Union has suffered a serious problem with its Mir
space station.  What exactly is wrong was not stated but on April 11
Radio Moscow announced that the current crew (Dr. Valrey Polyakov,
Alexander Volkov and Sergei Krikalev) will be returning to earth on
April 27th.  They are currently preparing the station for operation in
an unmanned automatic mode.  Originally Soyuz TM-8 was scheduled for
launch on April 19th to bring a two man crew of Alexander Viktorenko
and Alexander Balandin.  It is not likely that the problem is with the new
crew (there is always a backup team) or the launcher/capsule.  If that
was the case they would probably just have ordered the current crew to
stay up there another two months until the next launch window, in mid
June.  There Soyuz TM-7 is about 4 months old at this point, 6 is the
maximum they keep capsules up there for.  Also, they have in the
past sent a Soyuz up on automatic to a space station to replace a capsule
that was suspect (in June 1979 Soyuz 34 was sent up to Salyut 6 to replace
the Soyuz 32 which had exceed the [then] 90 day limit because of the
failure of Soyuz 33 to dock to the station).  All of this suggests that
there has been some failure on board the Mir station.  There have been
some rumors that there were problems with the gyroscopes in the Kvant
section, but if these were true that should not be reason for leaving
Mir unmanned (it was run without them for many months even with the
Kvant module attached).  However, it cannot be a life threatening problem;
an emergency landing at this time would be relatively safe, and the
normal Mir launch/landing window opens on April 19th.  Thus this crew
is coming down near its expected time of April 29th.  There was no statement
as to the cause of the problem, not in the keeping with the current
Glasnost tendency.  After the Phobos II loss and the sinking of the Mike
class nuclear submarine it appears that one more failure was a bit more
than the news service could take in a one month period.  One can
speculate that they are studying the situation and will send up a repair
crew after the proper equipment has been manufactured.
     Thus it appears that there will be a hiatus in the permanent presence
of humans in space.  The Russians came close, but it looks like they will
not pull it off.  On the other hand they did get a 26 month run - mankind's
best result so far.

                                                      Glenn Chapman
                                                      MIT Lincoln Lab

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

Date: 9 Apr 89 15:55:42 GMT
From: rochester![e-mail]  (Paul Dietz)
Subject: Gigantism of SPS

In article <[e-mail]> [e-mail] (Ray Lubinsky) writes:

>I hate to break the news to you, but SPS never had a chance anyway.  For
>starters, it requires a huge infrastructure, massive startup costs, and
>potential biohazard (at least, I'll pass on living anywhere near the microwave
>collectors, thank you).

SPS gets more practical if you posit the existence of moderately
efficient sun-pumped lasers.  At constant beam power density, the
power output of an SPS scales linearly with the wavelength of the
beam.  If a lambda = 1 cm system needs 10 GW, a 1 micron system could
operate at 1 MW.  The aperture of the transmitter and receiver shrink
by a factor of 100.  Probably it pays to make the beam a bit more
intense to burn through clouds.

Of course, you'd need some way of efficiently converting laser light
to electricity.  That should be easier than converting sunlight, since
laser light is far brighter and is monochromatic.  I believe 50%
efficiency has already been attained with PV cells with the proper
bandgap.

The start-up costs of making the SPS factory are still exorbinant.

> Personally, I imagine that after some substantial (on orbit) research
> of 0 G materials processing, there will be hundreds of reasons for the
> development and habitation of LEO and the Moon.

This man is an optimist.  I think zero-gee materials processing will
have very limited market penetration, and will no more promote
habitation of the Moon than did the comsat industry.

    Paul F. Dietz
    [e-mail]

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

Date: 9 Apr 89 11:35:29 GMT
From: amdahl!drivax![e-mail]  (MacLeod)
Subject: Assaying likely asteroids from afar


 ;To supply the whole world at this (first world) rate requires 5e12 Kg total.
 ;Assuming 3% ore @ 3.5gm/cc, this is an equivalent sphere 4.5 Km in diameter,
 ;weighing 5e9 tons or 5e12 Kg.
 ;There exist at least 40,000 asteroids larger than 5 Km in diameter.
 ;
 ;2. Asteroid mining energy considerations
 ;----------------------------------------
 ;The deltaV from the Belt to Earth is 7 Km/s. Moving 5e12 Kg of asteroid
 ;needs 1e20 joules (about 1% of world's annual (1978) energy use).
 ;
 ;Reproduced without permission from "A Step Farther Out" by Jerry Pournelle

In a note to Mike Van Pelt I suggested that we take one of the one-shot SDI
lasers, aim it at a likely asteroid, and light if off.  This should give us
enough reflected signal to spectrographically assay the rock (or metallic
lump, we would hope).

Mike replied that it sounded feasible except for the political constraints of
the treaty which bans atomic explosions in space.  I'm sure he's correct, but
it would be nice, in the current thaw in the cold war, if we could convince
them that we weren't up to something.  After all, I'm sure they would rather
see them pointed someplace else.

Michael Sloan MacLeod  (amdahl!drivax!macleod)

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

Date: 9 Apr 89 20:38:58 GMT
From: pyramid!nsc![e-mail]  (andrew)
Subject: Re: Assaying likely asteroids from afar

In article <[e-mail]>, [e-mail] (MacLeod) writes:
> In a note to Mike Van Pelt I suggested that we take one of the one-shot SDI
> lasers, aim it at a likely asteroid, and light if off.  This should give us
> enough reflected signal to spectrographically assay the rock (or metallic
> lump, we would hope).

What immediately springs to mind here is the possibly of _in situ_ smelting.
It's been suggested by others that a solar mirror melting arrangement might
do it, but (without doing the calculation) this sounds impractical.
Such a laser would come in very handy. I'm not sure whether it would be
practical to leave it in earth orbit though; fine control at this range
and relative velocity would make smelting haphazard and dangerous for the
local-to-asteroid miners B^) Smelting before transportation can be extremely
cost-effective, especially if the ore is not particularly rich.

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

Date: 7 Apr 89 03:48:12 GMT
From: attcan!lsuc!ncrcan!moegate![e-mail]  (Norman S. Soley)
Subject: Re: Success with cold fusion reported

In article <[e-mail]> [e-mail] (Richard Frost) writes:
>In article <[e-mail]>, [e-mail] (The Polymath) writes:
>> In article <[e-mail]> [e-mail] (Mark Armstrong SOFT) writes:
>> [...]
>> }Why do you think it would be more efficient to produce your own electricity
>> }instead of buying it from utilities?? What would be the cost of such system,
>> }$5,000 sounds realistic. ...
>>
>> That's about what I cost it out to.  I'd cheerfully pay $5000 to be energy
>> independent.
>
>Although utility companies are required to by any excess power you generate
>YOU are responsible for purchasing a synchonous interface to the grid ( a
>synchronous inverter if you're generating DC) plus a new meter and pay for
>periodic calibration inspections by the utility company.
>
>So if there is any merit to the giant 'hill of salt' speculation that we
>could all have fusion generators in our backyard, be prepared to add an
>additional $1500 to your overhead costs plus $100 to your annual cost.

OK let's take it as a given that the Pons & Flieshmann experiment, refined,
optimised, and engineered for a few years results in practical generators
small enough to bury in one's backyard (personally I think that, initially
at least, P&F derived fusion will only be economically practical in power
plant sizes).

In order for the current power grid to work it is necessary to balance
the input and output of the system, or at least attempt to. The amount of
power generated by windmills and small hydro-electric plants is a drop in
the bucket so the utilites don't worry about it. Most utilities have a
centre where they do load balancing, turning on and off generating
capacity as it's needed. It's a complex and delicate system, for example
the infamous New York blackout of the 60's resulted from a single blown
relay near Kingston, Ontario that took enough load off the grid suddenly
to crash the whole shooting match, everyone turning their TV's off
at the end of the Tiny Tim's wedding episode of the Tonight show came "this
close" to putting the whole continent in darkness. A power grid consisting of
large numbers of small generators, if possible at all, would require a
massive automated control system, and think of the administrative headache of
deciding who's generators to take off-line at any point in time. Of course one
might ask: if small generators are that cheap and easy why tie them into a
grid at all?
--
Norman Soley - The Communications Guy - Ontario Ministry of the Environment
Until the next maps go out:    moegate![e-mail]
if you roll your own:     uunet!{attcan!ncrcan|mnetor!ontmoh}!ontenv!moegate!soley
I'd like to try golf, but I just can't bring myself to buy a pair of plaid pants

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

Date: Sun, 9 Apr 89 04:00:11 PDT
From: Eugene Miya <[e-mail]>
Subject: Reminders for Old Farts

Hints for old users (subtle reminders) You'll know these.

Minimize cross references, [Do you REALLY NEED to?]
Edit "Subject:" lines especially if you are taking a tangent.
Send mail instead, avoid posting follow ups. [100 mail messages mean more than 1
follow-up.]
Read all available articles before posting a follow-up. [Check all references.]
Cut down attributed articles.  Summarize!
Put a return address in the body (signature) of your message (mail or
article), state institution, etc. don't assume mail works.

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

Date: 8 Apr 89 20:42:50 GMT
From: !cmx!amax.npac.syr.edu![e-mail]  (Anand Rangachari)
Subject: Re: Hubble Space Telescope


  Did anybody read the interesting article in the journal Nature about
the Hubble space telescope?

It seems that 6 important bolts which hold a mirror assembly within
the tube are not properly secured with epoxy and may come loose
due to the vibration caused by the launch.

Right now, a special platform is being constructed which will allow
a worker to enter the telescope without touching the sides of the tube.
The worker will then apply the six tiny blobs of epoxy.

The whole thing will cost $350,000.

R. Anand            Internet: [e-mail]
                    Bitnet:   ranand@sunrise

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

Subject: jim benz and kicking us off dis heah planet
From: [e-mail] (Nicholas C. Hester)
Date:    Sun, 09 Apr 89 15:00:59 EDT

jim- i'm sorry, but i refuse to leave this planet if i'm not allowed back on to
live. i was borne here and no one has the right to move me off.

=nick=
[e-mail]
[e-mail]

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

Date: Sun, 9 Apr 89 12:47:53 PDT
From: Peter Scott <[e-mail]>
Subject: Re: more on Liberty Bell 7 (and other s'craft)

m2c!wpi![e-mail]  (Tom [Chris] Murphy) writes:

>In article <[e-mail]> [e-mail] (Mark Robert Thorson) writes:
>>A few years ago, someone mentioned some Apollo hardware was in the ocean
>>(I think it was the LEM from Apollo-13).

>There's no way a LEM could survive re-entry.  The thing is EXTREMELY flimsy,
>I once heard (in a book by Michael Collins I think) that a technician once
>dropped a wrench through the hull.

I believe that the LEM carried an RTG which was projected to survive re-entry
intact.

Peter Scott ([e-mail])

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

Date: 9 Apr 89 21:51:32 GMT
From: ames.arc.nasa.gov![e-mail]  (Mike Smithwick)
Subject: Re: far side of the Moon photo mission (ussr's)

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Doug Mink) writes:
>>*Surveyor 4      Apr. 17, 1967  Soft-landed on moon; returned photos and soil data
>
>Check your data, please, Surveyor 4 was a failure if I'm not mistaken.
>Its transmitter went dead in mid-flight.  It conceivably may have made a
>successful landing, since landing was completely automatic, but it returned
>no data of any kind.
>--

The Surveyor 4's signal abruptly cut off about 40 seconds after the beginning
of the main retromotor ignition, about 1 1/2 seconds before burnout. The
spacecraft was at 49,000 feet above the lunar surface. JPL tried for the
next day to re-establish contact, but was unable to.

After a "thorough investigation", the review board could not determine the
cause of the failure, but concluded that it was a fluke so no spacecraft
resdesign was carried out.


mike

          *** mike (cerbral GURU, insert M&Ms to restart) smithwick***
"Oh, I'm just a NOP in the instruction set of life, oh, ohhhh, hmmmmm"

[disclaimer : nope, I don't work for NASA, I take full blame for my ideas]

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

Date: 10 Apr 89 02:34:50 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: constant-boost fusion spaceships, power requirements of

In article <[e-mail]> [e-mail] (Mark A. Sobolewski) writes:
>><....the power requirements are not merely high, but staggering, if
>
>    For the record... I get 1 gigawatt for a 20 kilo-ton (metric) mass
>accelerating at 1g.  (P=E/t, delta(v)=g*delta(t) (1 second),E=0.5mv^2,
>20,000,000kg)  (minimum power consumption of course).

Ah, but that's for acceleration from 0 to (roughly) 10 m/s.  Do the same
computation for 1000 to 1010 m/s and you get about 10 terawatts.  Yet
obviously the same rocket hardware would do either job using the same
amount of fuel and energy.  Clearly you're not measuring what you think
you are.  What you are measuring is the amount of energy needed to do
that bit of accelerating by pushing on a fixed object.  That is, with
a catapult rather than a rocket.  The math is right, but you have to
apply it to what you're actually pushing on, which for a rocket is its
exhaust jet.

>    While not a very large ship....  It still has enough room...

Actually it's pretty sizable, I'd say.  That's the size of an Invincible-
class aircraft carrier.  For solar-system work we can build them a lot
smaller.  However, let's assume that mass for convenience.  Now, the
power requirement to expel a jet with a mass flow of (dm/dt) and an
exhaust velocity of v_exh is 0.5 * (dm/dt) * v_exh^2.  So we need to
figure out the mass flow and exhaust velocity.

Mass flow depends on how long a mission we want to fly and how much
fuel we want to carry.  Let's say we're going to the asteroid belt
and back.  In very round numbers, that's a round trip of 1e9 km.
For continuous acceleration (i.e. one half of each leg of the trip),
time = sqrt(2*distance/acceleration) = sqrt(2*250e9/10) = 224000.
That's a quarter of the trip, so the whole thing is 900000 seconds,
about 10 days.  As for fuel, if we don't want the fuel tank to
dominate the whole ship, a fuel fraction of maybe 10% is tops.
So that's 2e6 kg of fuel, giving a fuel flow of about 2 kg/s.  Clearly
fuel pumps, at least, will not be a problem.

Now, what about exhaust velocity?  There are roundabout ways to
compute that, but thrust = (dm/dt) * v_exh due to conservation of
momentum, so we can do it fairly directly.  Thrust to push 20e6 kg
along at 1 gee will be about 200e6 newtons.  (We assume a constant
thrust; in practice one would throttle back a bit as the ship burned
off fuel, to keep acceleration constant, but that complicates the
arithmetic no end and does not affect the result much.)  So v_exh =
200e6/2 or about 100e6 m/s.  The numerate reader will have gone
"gulp!" on seeing that number, since it is about 1/3 of the speed
of light.  Clearly spaceship Invincible's engines are going to be
a pretty remarkable piece of engineering.  But we press on...

We now have the numbers we need.  Assuming 100% efficiency and no
losses whatever, spaceship Invincible's fusion generator output needs
to be 0.5 * 2 * 100e6^2 = 10 petawatts.  The numerate reader is
having a terrible coughing fit at this point.  For the innumerate:
a petawatt is a million gigawatts, and the entire power output of Earth,
right down to cooking fires, is a small fraction of *one* petawatt.
Clearly, Invincible's generators are, um, impressive pieces of
engineering in their own right.

Clearly 100% efficiency is optimistic.  Let's say it's only 99.99%.
Then Invincible's cooling system has to dissipate a mere terawatt
of heat.  (The numerate reader's coughing fit returns.  A terawatt
roughly equals the electrical power generation of North America.)
The easiest way of cooling something is with flowing fluid; radiating
heat into space is much more hassle.  Assume we use water; it's cheap
and available in quantity, and it's a good coolant.  Melting from
ice and boiling to steam both introduce hassles, so let's say our
input is water just above freezing and output is water just below
boiling.  That's a temperature rise of about 100 C.  The heat capacity
of water is roughly 4200 joules/kg/C, so each kilo absorbs 420e3 J.
So to carry away 1e12 W, we need about 2400 tons per second.  Oops.
Spaceship Invincible has a *bad* cooling problem.

What's more, the numerate reader, having recovered from his coughing,
observes that since E=mc^2, boosting the fuel to 1/3 of the speed of
light requires converting about 5% of its mass to energy (we speak
sloppily here for clarity; physicist readers will please keep quiet).
No wonder the power requirement was massive.  The n.r. goes on to
observe that fusion simply doesn't convert that big a fraction.
Invincible's power requirement just cannot be met by fusion, period.
Antimatter might do; Invincible would need to burn about 50 grams
per second (remember that each gram annihilates its own mass in
normal matter).  Optimistic fans of antimatter propulsion think that
straightforward application of current technology might perhaps get
antimatter prices down to $1M/mg.  Invincible's operating costs will
then be fifty billion dollars per second.  I don't think even DoD
can afford to fly this spaceship.

I could go on, computing things like radiation output from the power
system, size of heat radiators, etc., but the numbers all come out to
be preposterous.  Not just difficult, but beyond current abilities by
so many orders of magnitude that straightforward extrapolation of
today's technology won't do -- breakthroughs will probably be needed.

The moral of the story is, don't get intoxicated by the possibility of
easy fusion.  It may give us the solar system, but it will not give us
1G constant-boost spaceships.  They are fundamentally hard to build;
still better technology will be needed.
--
Welcome to Mars!  Your         |     Henry Spencer at U of Toronto Zoology
passport and visa, comrade?    | uunet!attcan!utzoo!henry [e-mail]

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

End of SPACE Digest V9 #359
*******************