Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v11_1/v11_104.txt

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Subject: SPACE Digest V11 #104

SPACE Digest                                     Volume 11 : Issue 104

Today's Topics:
                Re: Cheap DSN?
      [Alan Fernquist <[e-mail]>: HEI]
                  Re: SLC-6
               Re: Spacecraft on Venus
                  Space List
             Re: Power Economics
               Re: Spacecraft on Venus
          Re: Spacecraft drives and fuel efficiency
           antimatter propulsion approaches
               Ariane V36: Mission lost
----------------------------------------------------------------------

Date: 28 Feb 90 16:39:17 GMT
From: zaphod.mps.ohio-state.edu!usc!cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Cheap DSN?

In article <[e-mail]> [e-mail] writes:
>Could we build a better one using a helluva lot of generic satellite reciever
>dishes, a helluva a lot of not-top-of-the-line PC's and a helluva lot
>of very good software written by cheap programmers? ...

In a word, no, probably not.  Many little dishes are not a workable
substitute for a few big ones, and the receiver technology used to get
intelligible signals out of what the dishes pick up is not something
you build in your basement.  Software and such are secondary; just pulling
in the signal from a 75-watt transmitter rounding Saturn is the hard part.
For that you need a big precise dish and very-low-noise receivers.

(Yes, there are techniques for using multiple dishes as if they were one
still-bigger one, but if you thought the technology for *one* dish was
difficult to do in your basement, multi-dish arraying is a whole new order
of magnitude.)
--
"The N in NFS stands for Not, |     Henry Spencer at U of Toronto Zoology
or Need, or perhaps Nightmare"| uunet!attcan!utzoo!henry [e-mail]

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

Date: Wed 28 Feb 90 14:47:23-PST
From: Jay Glass <[e-mail]>
Subject: [Alan Fernquist <[e-mail]>: HEI]
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Date: Wed, 28 Feb 90 13:50:59 PST
From: Alan Fernquist <[e-mail]>
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To: [e-mail], canfield@pluto,
    [e-mail], chuang@pluto, [e-mail],
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Subject: HEI

I thought you might be interested in a memo that came out of
the National Space Council last week on the Presidential Decision
on the Space Exploration Inititative:

"The President has approved the following policy for the Space
Exploration Inititative program:

- The Initiative will include both Lunar and Mars program elements.

- The early program will focus on technology development with a
search for new/innovative approaches and technology.

- The program will include investment in high leverage innovative technologies
with potential to make a major impact on cost, schedule, and/or performance.

- The program will take at least several years defining two or more
significantly different human space exploration reference architectures,
while developing and demonstrating technology broad enough to support
all; selection of a baseline program architecture will occur after
that time.

- The program will perform mission, concept, and system analysis
studies in parallel with technology development.

- The program will include robotic science missions.

- By spurring research and development in high technology fields,
the space program will help promote American economic leadership.

- The program will require the efforts of several agencies.
NASA will be the principal implementing agency.  The Dept. of Defense
and the Dept. of Engergy will also have major roles in the conduct of
technology development and concept definition.  The National
Space Council will coordinate the development of an implementation
strategy for the Exploration initiative by the three agencies.
To facilitate coordination, the Dept. of Energy will be added
as a formal member of the National Space Council."

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

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

Date: 1 Mar 90 23:44:24 GMT
From: [e-mail]  (SERRE GLENN)
Subject: Re: SLC-6

SLC-4E and SLC-4W are Titan launch pads.  SLC-6 will probably be turned into
a Titan IV launch pad.  The Air Force machinery for this has apparently started
to turn.

--Glenn Serre
[e-mail]

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

Date: 1 Mar 90 16:52:06 GMT
From: mailrus!b-tech!kitenet![e-mail]  (Russ Cage)
Subject: Re: Spacecraft on Venus

In article <[e-mail]> [e-mail] (Mike Van Pelt) writes:
>Better, you could build a probe designed to operate at Venus surface
>temperature.  (At 800 degrees?  Right.  It would probably be easier to
>build the heat pump.)  Semiconductors are out....

I would not be so certain.  I'm aware of at least one silicon
technology with an operating temp limit of 300 C (CMOS underlain
with ion-implanted glass), and GaAs runs pretty warm too.  What
I hear about silicon carbide is that it can run extremely hot.
Not sure about 800 F, but maybe it can be pushed that far.  If
your probe operates at ambient, you're set (then you need POWER).
--
  I am paid to write all of RSI's opinions.  Want me to write some for you?
[phone]        Forewarned is half an octopus.
Russ Cage, Robust Software Inc.            [e-mail]

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

Date:    Fri, 2 Mar 1990 9:13:58 EST
From: [e-mail]
Subject: Space List
X-Vmsmail-To: SMTP%"[e-mail]"

Please add me to the Space mailing list.  Thanks.
--scott

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

Date: 2 Mar 90 02:33:39 GMT
From: mailrus!b-tech!kitenet![e-mail]  (Russ Cage)
Subject: Re: Power Economics

(I should mention here that I have been using Ann Arbor as my reference
 point for insolation in Michigan.  Most of Michigan is worse off in
 winter.  None of the surrounding states is even 50% better off, though.)

In article <[e-mail]> [e-mail] (Rob Kleinschmidt) writes:
[on cogeneration and heat/electricity needs]
>Well they sync fairly nicely by season, with the generator running
>only in mid winter months.  [much deleted]

That's one house.  What about thousands of houses, plus factories
and offices?  I am thinking a little bigger than you are, I believe.
I think domestic cogeneration is a great idea, if the generators are
very cheap, safe and reliable.  If they aren't, if they cost too much,
have dangerous failure modes or break down very often, the average
person won't want one.  Storing heat is not very practical; the Luz
solar-steam plants in the Mojave don't even try.  Storing electricity
is costly too.  If you don't need heat at the same instant you need
juice, or vice versa, you are talking storage.

(I would love to see someone try Lofstrom loops for energy storage,
they might change the whole equation.  But the failure modes...  If
Keith Lofstrom is still on the net, maybe he'll give us an update.)

>Out of curiousity, I would like to ask about:
>
>1) What are the general dimensions of the collector and ground based
>antenna for a delivered kwh of electricity? Even assuming only a
>fraction of a meter per capita (probably not enough to match peak
>demand ??), this sounds like a fair amount of stuff in orbit.
>Interesting disposal problems also when end of lifetime is reached.

1a.)    Numbers:  Our US population is about 2.5e8, US generating
    capacity is about 6.5e11 watts.  This works out to 2.6 KW
    per capita.  If microwave conversion, transmission and
    rectification are 50% efficient, solar cells on the SPS are
    10% efficient, and incident sunlight is 1360 W/m^2, then
    you need 38 m^2 of orbital collector per capita.  (6.5e11 W
    figure from the 1/'90 _Audubon_, p. 65.  I believe that
    includes peaking generators.  Base load is much less.)
    I've calculated the necessary satellite size, it's doable.

    Power density to the rectenna is around 150-200 W/m^2 avg.
    The rectenna is mostly holes, sun shines right through.
    The area beneath would be perfectly suited for farming.
    Rectennas would come in about 5x7 mile ellipsoids, and
    could be sited anywhere.  This includes lakes & oceans.

1b.)    Yes, it's a fair amount of stuff in orbit.  You'd build
    it from material already in orbit (the moon, for example).
    This is far more energy- and cost-efficient than launching
    everything from the ground, but takes a bit more R&D.

1c.)    Disposal problems?  What disposal problems?  The space in
    geosync is at a premium, any obsolete powersat would be
    scavenged for raw materials in short order (like junk cars).
    The level of space activity needed to construct and maintain
    large numbers of SPSs would have no trouble disposing of one.

>2) How well does the rate of delivery match to real demand. A pretty
>fair amount of human activity does track daylight. If you deliver
>equal amounts of power at 3 am. what do you do with it?

Try recharging electric-car batteries, at 30+ KWH apiece overnight.
(Ground-based solar cannot do this without adding a second set of
battery losses.)  Or electrolyzing hydrogen to make ammonia for
fertilizer (replacing natural gas).  In summer, freezing ice for
daylight air-conditioning or desalinating salt water (replacing
eco-problem aqueducts).  For ocean-based collectors, electrically
pulling carbonates out of solution to get CO2 for fuel synthesis (or
just to pipe to the ocean floor).  I'm sure we can think of more uses.

I expect that cheap, abundant baseload power will cause changes in the
way we use energy (like loading things on at night).  And if overnight
battery charging for electric vehicles is cheap, there will be more
incentive to use them.  Ground-based solar is not suited for powering
base loads in the absence of cheap storage.

>Seems like the delivery problems inherent here are the flip side of
>those found in the ground based array.

Exactly!  Which is why we have two types of electric generating
plants, base-load and peaking.  The former are capital-intensive
and use cheap fuel, the latter are cheaper and use more expensive
fuels.  Ground-based solar can handle many peaking requirements,
but not the base load or new nighttime loads (like charging car
batteries).  SPS can handle base loads without needing storage.
SPS is perfectly suited to replacing nuclear and coal-fired
baseload capacity, which ground-based solar is not.  Since coal
is the major culprit behind acid rain and greenhouse-gas
emissions and nobody likes nukes, SPS is worth a great deal
of attention and investment.
--
  I am paid to write all of RSI's opinions.  Want me to write some for you?
[phone]        Forewarned is half an octopus.
Russ Cage, Robust Software Inc.            [e-mail]

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

Date: 2 Mar 90 06:42:19 GMT
From: [e-mail]  (Charles Daffinger)
Subject: Re: Spacecraft on Venus

In article <[e-mail]> [e-mail] (Russ Cage) writes:
o In article <[e-mail]> [e-mail] (Mike Van Pelt) writes:
o >Better, you could build a probe designed to operate at Venus surface
o >temperature.  (At 800 degrees?  Right.  It would probably be easier to
o >build the heat pump.)  Semiconductors are out....
o
o I would not be so certain.  I'm aware of at least one silicon
o technology with an operating temp limit of 300 C (CMOS underlain
o with ion-implanted glass), and GaAs runs pretty warm too.  What

As to typical Si. process temperatures:

Boron diffusion may be done at between 300 and 900 deg C, Phosphor diffusions
at about 900-1400 deg. C, and Antimony diffusions at approx 600-650 deg C.
Oxidation is done at anywhere from 800 to 1400 deg C.

This tells me that if you want to use Si based semiconductors, you probably
will want to cool them.  Otherwise they won't be semiconductors for long.
I don't know about GaAs or any of the more esoteric semiconductors, but
I doubt they will be useful at such temperatures for long.


-charles
--
Charles Daffinger  >Take me to the river, Drop me in the water<  [phone]
[e-mail]
Home of the Whitewater mailing list:    [e-mail]

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

Date: 2 Mar 90 17:53:09 GMT
From: samsung!aplcen!aplvax.jhuapl.edu![e-mail]  (Jim Meritt)
Subject: Re: Spacecraft drives and fuel efficiency


Take off in the "torch" ships (antimatter/fusion) from at sea.

Ashore, towers melt and pads may too, but water is rather easy to replace.
Land there, too.  We KNOW that works.

Unless, of course, your exhaust is other than real, real hot.


That that is is that that is. That that is not is that that is not.
That that is is not that that is not.  That that is not is not that that is.
And that includes these opinions, which are solely mine!
[e-mail]  - or - [e-mail]  - or - meritt%aplvm.BITNET

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

Date: 2 Mar 90 18:57:30 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: antimatter propulsion approaches

In article <[e-mail]> [e-mail] (SERRE GLENN) writes:
>Probably the simplest way to use antimatter to power a launch vehicle would
>be to inject a very small stream of it into the combustion chamber of a rocket
>and use the matter-antimatter reaction to heat propellent instead of using
>a chemical reaction to do so...

This would be the normal approach for use within the solar system.  Getting
near-100% annihilation and using the charged particles that result gives
maximum exhaust velocity but relatively low thrust (for a given flow
of antimatter).  The exhaust velocities available are so enormous that for
anything short of interstellar missions, it makes sense to trade off some
velocity for the sake of higher thrust, and the way to do that is to use
small amounts of antimatter to heat much larger amounts of reaction mass.
--
MSDOS, abbrev:  Maybe SomeDay |     Henry Spencer at U of Toronto Zoology
an Operating System.          | uunet!attcan!utzoo!henry [e-mail]

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

Date: 27 Feb 90 14:56:49 GMT
From: mcsun!hp4nl!esatst![e-mail]  (Neil Dixon)
Subject: Ariane V36: Mission lost

The following is copied  from ESTEC News 14 Feb 1990.

-----------------------------------------------------------------------
    Ariane V36: Mission lost

The series of successful Ariane flights, 17 perfect launches in a row
since September 1987, has unfortunately stopped on February 22 with
flight V36. About 1 minute and 40 seconds after lift-off, the Ariane 4
launcher exploded In the sky above Kourou, French Guiana.

The launcher, which was carrying two Japanese satellites, lifted off
at 20:17 hrs, Kourou time, after a nominal countdown. The pressure in
the chambers of the 4 engines of the 1st stage propulsion bay and of
the 4 liquid strap-on boosters was nominal till 6.2 seconds after
ignition (HO + 6.2s).

At that moment, the pressure in the combustion chamber of one of the 4
engines (engine D) dropped, in half a second, from the nominal value
of 58 bars down to approximately 30 bars and remained around this
value until HO + 101 s.

Within HO + 6 and HO + 8.5 s, the attitude control system had sent to
engines A and C swivelling commands of 1,2 degrees amplitude in order
to compensate for the insufficient thrust of engine D. At
approximately HO+90 s, no further corrections were possible as the
engines of the 1st stage propulsion bay had reached the maximum of
their swivelling range.

At H0+101 s, the high dynamic pressure attained created excessive
stresses on the structure and triggered the explosion of the launcher
at an altitude of about 9 km and 12.5 km away from the launch pad.

An inquiry board is at work as of today. All Ariane flights are
suspended until the causes of this accident have been fully understood
and corrected.



--
Neil Dixon <[e-mail]> UUCP:...!mcvax!esatst!neil, BITNET: NDIXON@ESTEC
Thermal Control & Life Support Division (YC)
European Space Research and Technology Centre (ESTEC),
Noordwijk, The Netherlands.

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

End of SPACE Digest V11 #104
*******************