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Date: Thu, 28 Mar 91 01:39:24 -0500 (EST)
Subject: SPACE Digest V13 #309

SPACE Digest                                     Volume 13 : Issue 309

Today's Topics:
		     Re: Galileo asteroid imaging
	   Physical results of known processes (Velikovsky)
			   Re: He3 on moon
		 Need source for manned space flights
			Re: Astronaut Smokers
		    Re: Japan Moon Probes article
			      Minicomets
			   Linear launchers
			   Re: He3 on moon

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

Date: 21 Mar 91 22:49:10 GMT
From: uhccux!tholen@ames.arc.nasa.gov  (David Tholen)
Subject: Re: Galileo asteroid imaging

17001_1511@uwovax.uwo.ca writes:
 
> In November 1990 I spoke to Joe Veverka at Cornell about this - he is
> planning the observation sequences. The range is about 1000 km (not miles)
> but is not known very precisely because of uncertainty over the asteroid
> ephemeris (especially its range from Earth).

I would normally consider Veverka a very reliable source of information, but
if your conversation was in November, then it preceded the team meeting on
December 6 that resulted in the final decision.  Mike Belton, the imaging
team leader, gave me the 1600 km (or about 1000 miles) figure.  We've been
working on the asteroid's ephemeris.  I'd have to ask Don Yeomans for a
definitive answer (and I already have), but my guess is that we probably
know the asteroid's location to perhaps 50 km, maybe as bad as 100 km, at
the present time.

> Lightcurves suggest about
> a 9 hour period if I recall correctly (see a recent ICARUS paper), so
> about 4.5 hours before closest approach the view is of the side which will
> not be seen close up, assuming a low latitude approach (and we know very
> little about the axis orientation).

Just a tad over 7 hours (and that is authoritative -- I've observed the
lightcurve, and, in fact, am currently at Mauna Kea to do another, starting
tonight, weather permitting).  The intent is to have a low latitude approach,
and the trajectory chosen in December was based on the best information
available at the time.  I think we know more about the axis orientation than
you've suggested, and our paper will be submitted within days.  If our run
this weekend is successful, we should have a confirmation in hand of our
prediction of a high obliquity.

> Those images will resolve few features
> but will give an idea of shape. At closest approach the asteroid should
> overflow a single frame, as Miranda did at Uranus, so a mosaic will be needed
> for full coverage. The problem is with the image motion compensation - the
> rate depends on the exact flyby distance and there seems little chance it will
> be well known in time. The strategy will be to take as many redundant frames
> as possible with different image motion compensation rates, in order to get
> at least a few frames with very little smear. At least, that was the plan in
> November. The lightcurve variations suggest a complex shape, and the images
> may be quite dramatic.

Complex?  I'd prefer the term "asymmetric".  More egg-shaped than the usual
tri-axial ellipsoids used for modeling lightcurves.  I'm confident that the
images we do get will be dramatic, but I'm biased.  We will probably also
get a lot of blank frames, because the asteroid's location won't be known
that well, but we're working on it.

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

Date: 21 Mar 91 14:17:54 GMT
From: SUN4.JHUAPL.EDU!jwm@ucbvax.Berkeley.EDU  (James W. Meritt)
Subject: Physical results of known processes (Velikovsky)


Assume that Earth was in orbit around saturn, and that saturn was green-hot.

1. How close could earth approach saturn before tidal forces destroyed
it i.e. what would Roche's limit (sp) be?

2. What would the gravitational effects on the surface of the earth be
at this distance within a gravitational gradient?  I think it would
vary from 1G (at the optical horizon to saturn) to some value less
(at the nearest point and the farthest point)

3. Would the earth be tidally locked?  How long would it take for
it to become locked?  

4. If locked, what would be the effects if the lock were perpendicular
to the axis of rotation (like luna)?  If it were along the axis? CAN
something tidally lock along the axis of rotation, or would the
gyroscopic torque effects as the secondary orbits the primary prevent
it?

5. What would be the effects on the atmosphere of a nonuniform "felt
gravity"?  For instance, would super-hurricanes develop as the surface
pressure varied?  How low could the pressure get before the planet
would no longer sustain a N2/O2 mix (escape velocity > RMS velocity)

6. What would be the black-body temperature of earth if it were at the
orbitsl distance of saturn from sol and the distance (1) from a 
green-hot saturn?

Any other answerable questions, and their answers?

Opinions expressed are solely those of the author, and do not necessarily
represent those opinions of this or any other organization.  The facts,
however, simply are and do not "belong" to anyone.
    jwm@sun4.jhuapl.edu or jwm@aplcen.apl.jhu.edu or meritt%aplvm.BITNET

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

Date: Thu, 21 Mar 91 14:01:09 EST
From: John Roberts <roberts@cmr.ncsl.nist.gov>
Disclaimer: Opinions expressed are those of the sender
	and do not reflect NIST policy or agreement.
Subject: Re: He3 on moon


>From: sgeels@athena.mit.edu (Scott A Geels)
>Subject: Re: He3 on Moon?
>Date: 20 Mar 91 19:50:12 GMT
>Organization: Massachusetts Institute of Technology

[Excellent description of lunar He3 abundance and extraction - thanks!]

>Now for some of the problems:
>1) To process the 20t of 3He, 2.4 BILLION tonnes of lunar regolith must be
>processed per year. This regolith must be heated to ~900 C, which will take
>an enormous amount of energy even with a highly efficient process.

There is an enormous amount of energy from sunlight striking the moon. 
Concentrated and passed through a fused quartz window (softening point ~1665 C)
perhaps this could provide the heating needed.

>2) There must be an extremely large isotope separation plant to remove the
>relatively useless and much more abundant 4He. About 42000t of He must be
>separated to obtain the 20t of 3He.

With ~33% difference in mass, why should it be so hard? It's not like trying
to separate U235 from U238.

>3) Superfluid He will be very difficult to store both on the moon and on
>the return to Earth trip.

He3 does not form a superfluid. Even ordinary liquid He4 only becomes a 
superfluid if cooled down below 2.18K.

>4) D-3He fusion is not feasible at this point in time.

Do you mean "not economically", or that it has never been accomplished at all?

>Scott Geels
>Martin Marietta Astronautics Group

>Reply to: sgeels%fred.den.mmc.com@everest.den.mmc.com (or post)

         John Roberts
         roberts@cmr.ncsl.nist.gov

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

Date: 22 Mar 91 19:39:40 GMT
From: sco!erics@uunet.uu.net  (eric smith)
Subject: Need source for manned space flights


Can anyone point me to a source that lists all manned space flights
to date? The reference materials I know about only list "selected"
missions, generally ones with some outstanding feature.

I have a list that's complete up through about 1986, but I would
like to be able to stay current.

Thanks in advance!


-------------------------------------------------------------------------------
| Eric Steven Smith |   "And there was no smith in all the land of Israel:    |
| erics@sco.com     |   for the Philistines said, Lest they make them         |
| uunet!sco!erics   |   swords or spears."   -   1 Samuel 13:19-20            |
-------------------------------------------------------------------------------

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

Date: 21 Mar 91 10:14:36 GMT
From: eru!hagbard!sunic!mcsun!ukc!icdoc!syma!andy@bloom-beacon.mit.edu  (Andy Clews)
Subject: Re: Astronaut Smokers

From article <1991Mar18.222356@helga1.acc.Virginia.EDU>, by rnm8s@helga1.acc.Virginia.EDU:
> The Japanesse reporter who went to the
> Mir space station was a chain smoker - three packs a day!

No wonder he felt so ill when he got back to Earth!


-- 
Andy Clews, Computing Service, Univ. of Sussex, Brighton BN1 9QN, England
JANET: andy@uk.ac.sussex.syma        BITNET: andy%syma.sussex.ac.uk@uk.ac

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

Date: 22 Mar 91 16:25:18 GMT
From: news-server.csri.toronto.edu!utzoo!henry@rutgers.edu  (Henry Spencer)
Subject: Re: Japan Moon Probes article

In article <7435@idunno.Princeton.EDU> elturner@phoenix.Princeton.EDU (Edwin L Turner) writes:
>>... The story says the probes will be
>>ready in Spring, 1996.
>
>And you can safely bet that they will be, too.

Wait until we see how many years behind schedule the H-2 ends up being
before you say that.  (They're probably not using the H-2 to launch these,
but the point is that the Japanese are not superhuman -- they do hit
delays now and then.)
-- 
"[Some people] positively *wish* to     | Henry Spencer @ U of Toronto Zoology
believe ill of the modern world."-R.Peto|  henry@zoo.toronto.edu  utzoo!henry

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

Date: 20 Mar 91 19:26:30 GMT
From: zephyr.ens.tek.com!tektronix!sequent!crg5!szabo@beaver.cs.washington.edu  (Nick Szabo)
Subject: Minicomets

Some questions about minicomets:

* If I understand the theory correctly, it predicts that c. 1 minicomet/hr
  is hitting earth's moon?
* This frequency corresponds to what size range (eg 1-10 meters diameter)?
* Using the theory, how many minicomets have been captured into earth
  orbit?
* Do we have any way of detecting these comets (radar, optical, infrared,
  etc.)?

  thanks in advance,


-- 
Nick Szabo			szabo@sequent.com
"If you want oil, drill lots of wells" -- J. Paul Getty
The above opinions are my own and not related to those of any
organization I may be affiliated with.

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

Date: Thu, 21 Mar 91 13:23:11 EST
From: John Roberts <roberts@cmr.ncsl.nist.gov>
Disclaimer: Opinions expressed are those of the sender
	and do not reflect NIST policy or agreement.
Subject: Linear launchers


>From: henry@zoo.toronto.edu (Henry Spencer)
>Subject: Re: railguns and electro-magnetic launchers
>Date: 17 Mar 91 03:24:53 GMT

>In article <1991Mar15.103927.19905@leland.Stanford.EDU> gooch@leland.Stanford.EDU (Carl Gooch) writes:
>>Especially when you think about the peak heating and peak aero loads
>>for a projectile thrown from the surface with enough energy to reach
>>orbit.  Simply put, it would burn up before it got there.

>Nope, not true.  You simply have to design for a second or two in a very
>nasty environment.  People have seriously proposed it.

>Actually, a more fundamental problem is that anything launched to less
>than escape velocity from Earth's surface ends up in an orbit that
>intersects the surface.  It needs at least a *bit* of apogee kick anyway.

Is there any hope of getting a deflection from the atmosphere (i.e. 
aerobraking) over the course of one or two passes, of sufficient magnitude
to circularize the orbit to a point at which use of thrusters could be put off
for several more orbits?

If not of sufficient magnitude for that, perhaps aerodynamic maneuvering could
be used to adjust the planes of the orbits so that projectiles launched at
different times of day could be brought together.
     John Roberts
     roberts@cmr.ncsl.nist.gov

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

Date: 21 Mar 91 21:29:20 GMT
From: sgeels@athena.mit.edu  (Scott A Geels)
Subject: Re: He3 on moon

In article <9103211901.AA20428@cmr.ncsl.nist.gov> roberts@CMR.NCSL.NIST.GOV (John Roberts) writes:
>
>>From: sgeels@athena.mit.edu (Scott A Geels)
>>Subject: Re: He3 on Moon?
>>Date: 20 Mar 91 19:50:12 GMT
>>Organization: Massachusetts Institute of Technology
>
>[Excellent description of lunar He3 abundance and extraction - thanks!]
>
>>Now for some of the problems:
>>1) To process the 20t of 3He, 2.4 BILLION tonnes of lunar regolith must be
>>processed per year. This regolith must be heated to ~900 C, which will take
>>an enormous amount of energy even with a highly efficient process.
>
>There is an enormous amount of energy from sunlight striking the moon. 
>Concentrated and passed through a fused quartz window (softening point ~1665 C)
>perhaps this could provide the heating needed.
>

Assuming:
T(surface) = 111 C (ave, day)
Cp of regolith = 0.228 cal/g-C (basalt)
Production on lunar day only - 182 days of year

Q = m Cp (900C - T(surface))
Q = 1.8064 E+18 J of energy to heat up the rocks (assuming no recovery)

Therefore, over 182 days, and assuming 1350 W/m2 insolation:
Area of arrays (assuming 100% eff (only want thermal E)) = 8.51 E+07 m2

This implies a 9.2 km square area of solar concentrators
I don't know off hand if this is feasible, but it doesn't sound too realistic. 
Perhaps a fusion reactor to get the energy? That way you could use the 
product of the process in the process itself.

More energy will then be required to lower the temperature of the volatiles 
(although the quantity of volatiles will be much less than the rock mass).


>>2) There must be an extremely large isotope separation plant to remove the
>>relatively useless and much more abundant 4He. About 42000t of He must be
>>separated to obtain the 20t of 3He.
>
>With ~33% difference in mass, why should it be so hard? It's not like trying
>to separate U235 from U238.
>

You are right - this probably won't be too difficult. The problem is more the 
quantity of hardware required to perform this separation than the process
itself. 

>>3) Superfluid He will be very difficult to store both on the moon and on
>>the return to Earth trip.
>
>He3 does not form a superfluid. Even ordinary liquid He4 only becomes a 
>superfluid if cooled down below 2.18K.

I should have said cryogenic fluid, not superfluid. You have to store the 3He 
at less than 3.2 K. This may be somewhat difficult, but shouldn't be 
impossible. 

Actually (according to my outdated sources) 3He may become superfluid at T <
0.0055 K. This may or may not be true anymore, and is not relevant to storage
problems anyway.

>>4) D-3He fusion is not feasible at this point in time.
>
>Do you mean "not economically", or that it has never been accomplished at all?
>
It has been accomplished, but most of the past fusion research has been 
done with DD or DT reactios, not D-3He. And even these reactions have not 
reached the "break-even" point, where they produce more energy than is
put into the reaction. Depending on who you talk too, this "break" point
may occur anywhere from tomorrow until 100 years down the line to never.


My point is not to discourage the use of 3He for an energy source, just
to be realistic about it. There are a number of "layering" new technologies 
that have to be solved before this will be a realistic commercial
energy source, not the least of which is finding a cheaper way to get the 
tonnes of equipment necessary for this operation to the moon.


>         John Roberts
>         roberts@cmr.ncsl.nist.gov

Scott Geels
MMAG

sgeels%fred.den.mmc.com@everest.den.mmc.com

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

End of SPACE Digest V13 #309
*******************