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Subject: SPACE Digest V10 #430

SPACE Digest                                     Volume 10 : Issue 430

Today's Topics:
          NASA Prediction Bulletins:  Space Shuttle
       Name The Next Space Station Contest (Forwarded)
                 Space Digest
            Re: Nuclear Reactors in Space
     Re: Why did Solar Max fall but space junk stays up?
     Re: Why did Solar Max fall but space junk stays up?
     Re: Why did Solar Max fall but space junk stays up?
        Re: reactors in space, active control
          Re: How do they commercially produce Pu238
            Re: Nuclear Reactors in Space
----------------------------------------------------------------------

Date: 15 Jan 90 18:51:41 GMT
From: helios.ee.lbl.gov!ncis.tis.llnl.gov!blackbird![e-mail]  (TS Kelso)
Subject: NASA Prediction Bulletins:  Space Shuttle


The most current orbital elements from the NASA Prediction Bulletins are
carried on the Celestial RCP/M, [phone], 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
elements for the current shuttle mission are provided below.  The Celestial
RCP/M may be accessed 24 hours/day at 300, 1200, or 2400 baud using 8 data
bits, 1 stop bit, no parity.

STS 32
1 20409U 90  2  A 90 15.13545784  .00103876  00000-0  53946-3 0   220
2 20409  28.5019  99.9336 0002294 149.3184 210.8985 15.79458337   890
--
Dr TS Kelso                           Asst Professor of Space Operations
[e-mail]          Air Force Institute of Technology

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

Date: 15 Jan 90 05:44:38 GMT
From: rsc.cpfz.nasa.gov![e-mail]  (Public Affairs Office)
Subject: Name The Next Space Station Contest (Forwarded)


Homer Simpson/Deborah Norville
Reagan Space Center, Havana, CPFZ            January 15, 1998


NASA ANNOUNCES "NAME THE NEXT SPACE STATION" CONTEST

Release 98-15


NASA Administrator Roald Sagdeev today announced that a nationwide
contest will be conducted to name the nation's new space station,
currently in the design phase and designated SS-201.

The new station will replace Space Station Freedom, which was lost
shortly after initial deployment through alleged terrorist action.

At the request of President Quayle, the new armored station is to be
given a name chosen by qualified contestants at all Southland and
Pik-Pak convenience stores throughout the 53 states, US territorial
possessions and the Cuban Protective Free Zone.

"The replacement Station symbolizes this country's determination not to
be pushed around any more," Sagdeev said.  "Its name should evoke the
quest for truth and a zest for lasting dominance."

The contest winner will be offered a position as Mission Support
Technician on board the STS-97 mission in 2002, the third flight of the
new Space Shuttle orbiter Hawkeye (OV-107) currently under construction
in Japan.  If the winner is ineligible to fly for health or political
security reasons, a cash award will be made.

For more information on setting up a "Name The Next Space Station"
kiosk, including profit margins, promotional astronaut appearances and
payment terms, contact:

    Henry Spencer
    NASA Office of Promotional Spin-Offs
    Resettlement Zone 36 / Industrial Facility
    New Toronto, AZ   85909
    602-555-1812

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

Date: 13 Jan 90 20:16:25 GMT
From: snorkelwacker!ira.uka.de!smurf!gopnbg!altger![e-mail]  (serpent)
Subject: Space Digest

Hi, please include <serpent@altger> for distribution of Space Digest.
Thanks a stack !

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

Date: 15 Jan 90 14:49:14 GMT
From: rochester![e-mail]  (Paul Dietz)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Christopher Neufeld) writes:

>>How does one synthisize Pu238, anyway? What material does one start out with,
>>and what does one then bombard it with?
>>
>   According to the CRC, Pu238 was first synthesized in 1940 at the 60 inch
>cyclotron at Berkeley by bombarding uranium with deuterons.

It is now made in reactors.  When U-235 absorbs a thermal neutron, it
has a 14% chance of not fissioning, but instead making U-236.  U-236
is not fissionable by thermal neutrons, so it builds up in the fuel
elements (its half-life against alpha decay is 23.4 megayears).  It has
a moderate (5.1 barns) cross section for absorbing thermal neutrons.
The resulting isotope, U-237, decays to Np-237 with a half-life of 6.75
days.

Np-237 has a half-life of 2.14 megayears.  It has a neutron absorption
cross section of 180 barns (fission cross section .02 barns).  On
absorbing a neutron it makes Np-238.  Np-238 decays to Pu-238
with a half-life of 2.117 days.

I believe they make Pu-238 as follows.  Let some spent reactor fuel
decay a bit.  Extract the neptunium isotopes (this leaves behind the
plutonium that is also present in the spent fuel element).  Irradiate
this neptunium in a reactor.  Since Np-238 has a high fission cross
section, it may make sense to irradiate it for a short period, then
chemically separate the Pu-238, then irradiate the remaining Np, etc.

In the future, I suppose we might see direct separation of Pu-238 from
other plutonium isotopes direct from commercial reactor waste; the
government is (was?) seriously planning on building a special isotope
separation facility for atomic vapor laser separation of Pu isotopes
(for military purposes).

    Paul F. Dietz
    [e-mail]

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

Date: 15 Jan 90 19:22:52 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Why did Solar Max fall but space junk stays up?

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>I doubt that an explosion in near-reentry orbit sends much debris into
>long-lived orbits.  For good physical reasons, a near-reentry orbit is
>generally close to circular, which means that any orbit resulting from
>an explosion there will have a near-reentry perigee and won't last long.

This is true for natural decay when a satellite has a nearly circular
orbit to begin with.  My sketchy notes indicate that many Soviet
military birds have decidedly noncircular orbits and are deliberately
de-orbited by ground control when their useful life runs out.

Controlled de-orbit lets them aim at their own territory and so minimize
the security issues; exploding them first was designed to make sure no
large chunks survive re-entry for ANYONE to find.

There has been international pressure from us and the Europeans to stop
this practice, as well as to clean up our own problems like bad paints.

Debris control will grow in importance as and if space industry becomes
a reality; not only because industrial facilities will need protection,
but because they are potential debris sources.
--
When I was [in Canada] I found their jokes like their   * Tom Neff
roads -- not very long and not very good, leading to a  * [e-mail]
little tin point of a spire which has been remorselessly
obvious for miles without seeming to get any nearer. -- Samuel Butler.

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

Date: 14 Jan 90 11:43:28 GMT
From: van-bc!rsoft!mindlink![e-mail]  (Bruce Dunn)
Subject: Re: Why did Solar Max fall but space junk stays up?

The title question is most interesting!  For some background information on
space junk, I can quote a NASA contractor report (#3536) which looked at the
degree of protection a reusable orbital transfer vehicle would have to have at
a space station altitude of 370 km.  The 1982 report quotes an article by
Kessler and Cour-Palais in the Journal of Geophysical Research, Volume 83.  The
report states that as of 1980, NORAD was tracking (presumably by radar)
approximately 5000 objects of 10 cm or greater diameter.  Of these,
approximately 60% were fragments resulting from explosions, 20% were mission
related (shrouds etc.) and 20% were payloads (dead or alive).  The predicted
flux for 1990 was approximately 8000 objects. And this is just the large junk!
Added to this will be a tremendous amount of small stuff that NORAD can't
track.
     Not all of the junk will be in neat circular orbits.  When an object
explodes, some of the pieces will acquire extra velocity in the direction of
the orbit.  This will propel them into elliptical orbits with the high end of
the orbit well away from atmospheric drag.  For example, orbital velocity in
low earth orbit is very roughly 8000 m/sec.  If a piece of junk acquires an
additional 500 m/sec of velocity as a result of an explosion, it will enter an
elliptical orbit with an apogee of roughly 2500 km  and a perigee at its
original orbital altitude.  The junk will spend most of its time at high
altitude (travelling slower near apogee than perigee) but will make periodic
passes through the low earth orbit space.  Such junk will be much longer lived
than objects which stay totally in low earth orbit.
     For paint flecks etc. which are in low earth orbit, I can't myself see any
way that they should not rapidly de-orbit.  The answer to the question for such
material is probably that it does *not* stay up, but gets renewed from year to
year by new material.

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

Date: 15 Jan 90 16:56:40 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Why did Solar Max fall but space junk stays up?

In article <[e-mail]> [e-mail] (Peter Scott) writes:
>>>And every so often the Soviets render a dying
>>>military satellite worthless to scavengers by simply exploding it!
>>Normally this is done only for birds that are about to make an uncontrolled
>>reentry anyway...
>Thereby propelling back into orbit fragments that otherwise wouldn't be
>there.  Space debris is more of a problem than what's left of a satellite
>making an uncontrolled reentry hitting the ground.

The Soviets don't do this because they want to be nice to the folks on the
ground; they do it because they don't want an intact military bird coming
down on foreign soil where it might be given a customs and excise inspection
so thorough that it comes back to the USSR as a crate of disassembled parts.
(Which is what happened to the MiG-25 that Belenko defected with.)

I doubt that an explosion in near-reentry orbit sends much debris into
long-lived orbits.  For good physical reasons, a near-reentry orbit is
generally close to circular, which means that any orbit resulting from
an explosion there will have a near-reentry perigee and won't last long.
--
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry [e-mail]

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

Date: 16 Jan 90 00:31:56 GMT
From: sco![e-mail]  (Nathaniel Ingersoll)
Subject: Re: reactors in space, active control

In article <[e-mail]> [e-mail] (Kenneth Ng) writes:
:
:Um, most nuclear reactors in the United States have passive controls.
:For example, if the temperature rises, the reaction rate slows due to
:the laws of physics, not an active control mechanism.  In BWR reactors
:when more steam is generated, the lower density of water lowers the
:effectiveness of the water slowing down the neutrons, thus lowering
:the number of neutrons that can substain the reaction, thus slowing
:the reaction down.

I may not understand the above right, but -
water stops, or at least slows, neutrons in order to capture
some of their energy, turning it into heat.  Neutrons that are
slowed do not take further part in the nuclear reaction;
if the reaction gets too hot (coolant flow ie water flow gets
turned off, for instance), the water vaporizes, which as you
said lowers the effectiveness of the water in slowing down the
neutrons.  This has the effect of increasing the rate of
the reaction, which produces more heat, etc etc, meltdown.

:
:The only reactor design I know of that has positive feedback is the
:Chernobyl reactor.  Note: my reactor design books dated from the
:early 80's, so my comments may be out of date.


Turn off the coolant flow in most GE fission reactors here in the
US, without replacing the Boron (?) neutron-absorbent reaction
control rods, and the reactor becomes positive feedback.

--
________________________________________________________________________

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

Date: 15 Jan 90 18:21:48 GMT
From: rochester![e-mail]  (Paul Dietz)
Subject: Re: How do they commercially produce Pu238

In article <[e-mail]> [e-mail] (Andrew J Hasara) writes:

>   Pu 238 is produced in breeder reactors.  The nuclear reactions were
>given earlier on the net, so I won't get into that.
>   Breeder reactor are, in a simplistic model, a U235 heavy water
>reactor.  As far as I can recall, There are no modifications off of
>the simple "pile-in-water" design, except that the pile is made to be
>removed, ground up (or similarly broken up), and then filtered.
>  Because breeder reactors are heavy-water reactors, the US gov.
>regulates heavy water (deuterium oxide) and has some heavy
>restrictions on heavy-water reactors, and I think (with a lot of
>uncertainty) that there are no commercial heavy water nuclear power
>stations in the US.

>P.S.  I don't remember which isotope is weapons-type Pu, but it is
>also produced by breeder reactors, because Pu is VERY rare, more so
>than Radium.  This is beacause of the complex nuclear reaction, which
>requires slow neutrons.

Breeder reactors are any reactors that produce more fissionable
material than they consume.  They need not use heavy water.  Fast
breeders use no moderator at all.  I believe U233/Th232 has a breeding
ratio of about 1 with a graphite moderator.  The extraction of
plutonium is more complicated than just "filtering".

Production of Pu-239 merely requires irradiating U-238 with neutrons.
It does not require a breeder reactor; conventional PWRs make a lot of
plutonium too (they just can't refuel themselves).  The neutrons need
not be slow.  The nuclear reaction is not "complex", it's just neutron
capture followed by two beta decays.

D2O is restricted not because it is necessary to make a breeder
reactor, but because a heavy-water moderated reactor can be fueled
with unenriched uranium, which is widely available all over the world.

    Paul F. Dietz
    [e-mail]

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

Date: 15 Jan 90 21:29:45 GMT
From: ecsvax.uncecs.edu![e-mail]  (D Gary Grady)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Tim Maroney) writes
(in response to my admonition that he seek more technically reliable
sources than The Nation):
>
>Technically reliable sources like NASA's own reports, which were
>quoted verbatim in the Nation and served as the basis of the article?

Yes, the original NASA reports, though not the minuscule out-of-context
extracts by Grossman and Long in The Nation, would be a good start.  You
might also look into the independent reports by the Federation of
American Scientists, a left-leaning group opposed to SDI and to nuclear
reactors in space, which is be no means a pro-NASA bunch.  They said the
RTGs were nothing to worry about.

I appreciate your advice, but I thought I had made it clear in my
posting that I had already read the Nation article and the follow-up
comments in the letter column.  (In fact, I evidently read them more
carefully than you, since I didn't get confused about which report said
what, and I didn't omit the reference to "unlimited" funding being
required to make the CSA conversion in such a short time period.)  I
have found The Nation to be an interesting source of information and
opinions, but on this matter they are simply not reliable, as I think
you would quickly realize if you looked into the technical issues more
deeply.

>I'm sorry to hear that someone has been giving you doctored copies of
>the magazine.  They responded in detail...

Not in the copy The Nation sent me as a subscriber.  They responded at
some length without addressing a single technical point.  Instead they
held to their practice of out-of-context quotation from NASA documents
of any paragraph that seemed to agree with them.  It's interesting that
they chose to tar Casani with the same brush, but his quotation seems
far more contextually sound than theirs.  Grossman and Long have
consistently ignored the fact that the studies in question were done on
a hypothetical basis well into the development of Galileo.  They also
have never bothered to explain how NASA could be so opposed to solar
energy on these missions and yet spend money studying the
possibilities.

The NASA research in question suggests that if the time, funding, and
launch vehicle power were available, Galileo-class missions could be
accomplished with solar power.  Those are rather big ifs, and it's
reasonable not to bet the farm on them.

From reading what they've written it seems likely to me that Grossman
and Long are sincere amateur investigative journalists who have gotten
in over their heads and are not trying to save face by whatever debating
tactics come to hand.  Otherwise, why would they respond to the
technical points made?
--
D Gary Grady
[phone]
USENET:  ...!mcnc!ecsvax!dgary
BITNET:  [e-mail]

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

End of SPACE Digest V10 #430
*******************