Message-ID: <AZpEJeu00VcJEIMU5S@andrew.cmu.edu>
Reply-To: space+@Andrew.CMU.EDU
From: space-request+@Andrew.CMU.EDU
To: space+@Andrew.CMU.EDU
Date: Sun, 11 Feb 90 01:25:47 -0500 (EST)
Subject: SPACE Digest V11 #32

SPACE Digest                                      Volume 11 : Issue 32

Today's Topics:
			 Re: More Info On SSX
		      Re: Space Shuttle Question
		    Re: metric vs. imperial units
		      Computer Stellar Modelling
		       Re: Recreation in Space
		   Frequently asked SPACE questions
			 Re: More Info On SSX
		       Re: Space Station Costs
			 Re: More Info On SSX
		    Re: Kepler fudged the Numbers?
----------------------------------------------------------------------

Date: 10 Feb 90 18:00:44 GMT
From: rochester!dietz@louie.udel.edu  (Paul Dietz)
Subject: Re: More Info On SSX

In article <1089@mindlink.UUCP> a752@mindlink.UUCP (Bruce Dunn) writes:

>     One complication about talking about the density of propellants is
> that it is not just the density of the fuel that matters, but the
> overall density of the propellant mix, including oxidizer.  For
> hydrocarbon fuels, the maximum specific impulse is always for a
> fuel-rich mixture, not for a stochiometric mixture.  One reference I
> have has a chart which indicates that the maximum specific impulse for
> LOX and RP-1 occurrs at a bulk density of about 1.04.  The
> corresponding figure for LOX and CH4 is about 0.84, with the specific
> impulse for the LOX and CH4 being about 3% higher than for LOX and
> RP-1.

I calculate the bulk density of stoichiometric RP-1 (CH1.953; density
= .81 at 289 K) and LOX (90 K) is 1.014, so a fuel-rich mixture would
have lower bulk density than 1.04.  Perhaps your reference assumed the
LOX or fuel was colder?  The density of LOX increases from 1.14 at 90
K to 1.23 at 77.6 K and 1.306 at 54.4 K.

My reference (Sutton) says the Isp of LOX + RP-1 (which depends on
chamber pressure and nozzle pressure ratio) has a broad maximum around
a LOX/fuel ratio of 2.2-2.3, which is only slightly fuel rich
(stoichiometric mixture is ~2.29).  The F-1 engine had a mixture ratio
of 2.27.

> Researchers modeling single stage to orbit vehicles have found it
> advantageous to have both hydrocarbon engines and hydrogen engines on
> board - the former for the beginning of the ascent and the latter for
> the end of the ascent.

But isn't the SSX, as proposed, supposed to have only one kind of
engine?  Presumably putting twice as many engines in increases the
complexity of the vehicle.

	Paul F. Dietz
	dietz@cs.rochester.edu

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

Date: 10 Feb 90 22:37:21 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu  (Henry Spencer)
Subject: Re: Space Shuttle Question

In article <27460005@hpcvia.CV.HP.COM> 10e@hpcvia.CV.HP.COM (Steven_Tenney) writes:
>In addition to the Space Shuttle question, does anyone have any opinion of
>how a space station in geosynchronous orbit would be effected by a similar
>disaster to the world's oil supply? ...

Immediate effects would be minimal, due to the existence of substantial
reserves.  Long-term effects would depend on the priority given to keeping
the station running and the amount of resupply it needed (there is no
fundamental obstacle to making that amount very small if the station were
designed for it).

Note that geosynch orbit is a bad place to put a space station, since it
is in the fringes of the outer Van Allen belt and is an unhealthy place
to live unless heavy shielding is provided.
-- 
SVR4:  every feature you ever |     Henry Spencer at U of Toronto Zoology
wanted, and plenty you didn't.| uunet!attcan!utzoo!henry henry@zoo.toronto.edu

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

Date: 11 Feb 90 00:05:24 GMT
From: zephyr.ens.tek.com!wrgate!mrloog!dant@beaver.cs.washington.edu  (Dan Tilque)
Subject: Re: metric vs. imperial units

gregw@otc.UUCP (Greg Wilkins) writes:
>dant@mrloog.WR.TEK.COM (Dan Tilque) (me) writes:
>>
>> [Reasons why the shuttle should keep using nautical miles and feet.]
>
>You guys just keep making excuses!!!!   Yes an entire country can convert
>from imperial to metric -> Eg Australia and we have the safest airline in
>the world.  If any airline or spaceflight relies on the pilots ability to
>do mental arithmetic in his native units, then it aint safe!!

Actually, even Australian aviation still uses nm and feet, at the
very least for international flights.  And it's not so much mental
arithmetic, it's the ingrained reflexes that consider 2000 feet separation
safe, 1000 feet marginal and less than that unsafe (the numbers may be
slightly wrong, but that's the general picture).  This applies not just to
the shuttle pilots, but to the air (space) traffic controllers sitting on
the ground.

I think, in this regard, the shuttle should keep using whatever general
aviation is using.

>
>The whole point is that metric has many big points in its favour:

I agree.  I wouldn't mind converting, provided we do it the right way.

>I am told that America is the most inwardly looking nation on the planet,
>and boy does it show!!!  

Albania still has us beat, inward looking-wise.  But we're working on it
:-).


---
Dan Tilque	--	dant@mrloog.WR.TEK.COM

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

Date: 11 Feb 90 03:49:48 GMT
From: pasteur!sting!scott@ucbvax.Berkeley.EDU  (Scott Silvey)
Subject: Computer Stellar Modelling


    I am a physics student taking a course on stellar structure and
evolution.  Since I also have a strong interest in computers (they're
big toys), I've been implementing some of the simple theories we've been
learing in C code.  However, I realize that much of what you learn in a first
course of this sort is rather elementary and that what I am doing is really
behind the times.  So, in the interest of learning, I asked my professor if
he knew of any serious software that uses contemporary techniques to model
stars.  Unfortunately, his specialty is neither in stellar astronomy,
nor has he done much work with computer simulations.  Thus, the best he could
offer was a 300 line Basic program for the PC, plus references to the
two people here at UCB who are doing stellar atmosphere modelling.

    Does anyone know of any UNIX based software that uses at least
somewhat contemporary techniques and information in order to model stars?
I realize that such software could get pretty hairy, but that's fine, I
want to learn.  I can handle code in C, Fortran, and (if it has to be) Pascal.
I would prefer perhaps something that handles an entire star at once, and
would be really interested in something that deals with the evolution of
the star (especially as stars leave the main sequence).

   I would really appretiate any leads to software, or people doing this
kind of research.  What sort of journals, magazines, or books should I
look for that would cover this subject?  If anyone else is interested in
the help people send me, let me know.

Thanks a lot,

Scott Silvey (scott@xcf.berkeley.edu)

PS:  I have access to fairly fast machines (DecStations, a Mips 5400, a 12
processor Sequent, and probably even our idle Cray XMP-14).

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

Date: 9 Feb 90 19:24:33 GMT
From: van-bc!ubc-cs!fornax!zeke@ucbvax.Berkeley.EDU  (Zeke Hoskin)
Subject: Re: Recreation in Space

In article <1037@watserv1.waterloo.edu>, a1wrkshp@watserv1.waterloo.edu (WATMOST Groups 9) writes:
> Greetings sci.space Readers!
> 
> I am working on an undergraduate research project studying the need for
> recreational activities during prolonged periods in space (e.g. on a space
> 
> Finally, do what would YOU like to do if you were a crewman on the Space
    Assuming there were also crewwomen 
      I'd like to participate in organic docking maneuvers.
pa
dd
in
g

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

Date: Sat, 10 Feb 90 04:00:22 PST
From: Eugene Miya <eugene@amelia.nas.nasa.gov>
Subject: Frequently asked SPACE questions

This list does change.

This is a list of frequently asked questions on SPACE (which goes back
before 1980).  It is in development.  Good summaries will be accepted
in place of the answers given here.  The point of this is to circulate
existing information, and avoid rehashing old answers.  Better to
build on top than start again.  Nothing more depressing than rehashing
old topics for the 100th time.  References are provided because they
give more complete information than any short generalization.

Questions fall into three basic types:
1) Where do I find some information about space?
Try you local public library first.  You do know how to use a library, don't
you?  Can't tell these days.  The net is not a good place to ask for
general information.  Ask individuals if you must.  There are other sources,
use them, too.  The net is a place for open ended discussion.

2) I have an idea which would improve space flight?
Hope you aren't surprised but 9,999 out of 10,000 have usually been
thought of before.  Again, contact a direct individual source for
evaluation.  NASA fields thousands of these each day.

3) Miscellanous queries.  Sorry, have to take them case by case.

Initially, this message will be automatically posted once per month
and hopefully, we can cut it back to quarterly.  In time questions and
good answers will be added (and maybe removed, nah).

1) What happen to Saturn V plans? What about reviving the Saturn V
as a heavy-lift launcher?

Possible but very expensive -- tools, subcontractors, plans, facilities
are gone or converted for the shuttle, and would need rebuilding,
re-testing, or even total redesign.

2) Where can I learn about space computers: shuttle, programming,
core memories?

%J Communications of the ACM
%V 27
%N 9
%D September 1984
%K Special issue on space [shuttle] computers

Other various AIAA and IEEE publications.

Computers in Spaceflight: The NASA Experience
James E.  Tomayko
1988?

3) SETI computation articles?

%A D. K. Cullers
%A Ivan R. Linscott
%A Bernard M. Oliver
%T Signal Processing in SETI
%J Communications of the ACM
%V 28
%N 11
%D November 1984
%P 1151-1163
%K CR Categories and Subject Descriptors: D.4.1 [Operating Systems]:
Process Management - concurrency; I.5.4 [Pattern Recognition]:
Applications - signal processing; J.2 [Phsyical Sciences and Engineering]:
astronomy
General Terms: Design
Additional Key Words and Phrases: digital Fourier transforms,
finite impulse-response filters, interstellar communications,
Search for Extra-terrestrial Intelligence, signal detection,
spectrum analysis

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

Date: 10 Feb 90 22:52:15 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu  (Henry Spencer)
Subject: Re: More Info On SSX

In article <1089@mindlink.UUCP> a752@mindlink.UUCP (Bruce Dunn) writes:
>     The relative importance of propellant density near the beginning of the
>flight and specific impulse near the end of the ascent is reflected in many
>launch vehicles such as the Saturn or Titan/Centaur which use dense but low Isp
>propellants in the lower stages, and LOX and LH2 in the upper stage(s).

There is a complicating factor here, however:  hydrogen technology was late
in developing, so available hydrogen engines were small.  The Saturns could
not have used hydrogen in the first stages -- their development schedules
were too tight for such a big jump in hydrogen-engine size.  It was hard
enough to get hydrogen engines big enough for the upper stages.  The
shuttle was the first (and to date, the only) US launcher developed on
a schedule which permitted first-stage hydrogen engines.  Atlas, Delta,
and Titan all go back too far for that.

An added complication in the case of Titan is that avoiding cryogenic
fuels was a specific design objective for it.  It was the first US ICBM
that could be kept ready for instant launch, instead of having to be
fueled first.

In fact, I'm not aware of any hydrogen-fueled launcher built from scratch
without constraints like this.  ESA had enough trouble getting Ariane's
third-stage hydrogen engines to work, they could never have handled an
all-hydrogen launcher then.  (Now they probably can, and Ariane 5's first
stage will use hydrogen.)  The Japanese have followed a similar path,
starting with small upper-stage engines and working up to the hydrogen
first stage planned for the H-2.
-- 
SVR4:  every feature you ever |     Henry Spencer at U of Toronto Zoology
wanted, and plenty you didn't.| uunet!attcan!utzoo!henry henry@zoo.toronto.edu

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

Date: 10 Feb 90 23:01:23 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu  (Henry Spencer)
Subject: Re: Space Station Costs

In article <11968@thorin.cs.unc.edu> leech@pooh.cs.unc.edu (Jonathan Leech) writes:
>>[station waste]  As witness Lawrence Livermore's belief that they
>>could do a space station *and* a lunar base *and* a Mars base for the
>>same amount of money, basically by using existing technology and putting
>>the effort into getting the job done.
>
>    They may be right, but I don't believe that just because somebody
>at LLNL says it, it's true.  What's their background that their
>estimates are more believable than NASA's? ...

I didn't say their estimates are more believable, just that they aren't
utterly preposterous.  Like all early estimates, they are probably overly
optimistic.  (But then, the same applies to NASA's...)  But the LLNL
proposal does stress use of existing technology, whereas NASA sometimes
seems to go out of its way to avoid re-using anything.  For example,
the NASA lunar base looks to have been designed from scratch, while LLNL
proposes using the same inflatable modules for space station and both
planetary bases.  Even if LLNL is underestimating costs by a factor of
three, the results are still way ahead of NASA's.  It takes a lot of
faith in NASA and a lot of disbelief in LLNL to reduce them to anything
resembling equality.
-- 
SVR4:  every feature you ever |     Henry Spencer at U of Toronto Zoology
wanted, and plenty you didn't.| uunet!attcan!utzoo!henry henry@zoo.toronto.edu

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

Date: 9 Feb 90 03:19:43 GMT
From: van-bc!rsoft!mindlink!a752@ucbvax.Berkeley.EDU  (Bruce Dunn)
Subject: Re: More Info On SSX


     Propane can be subcooled to LOX temperatures for use as a fuel.  The
density of propane at room temperature is approximately 0.5.  Cooling propane
increases its density, so that at -100 degrees C its density is 0.65.  I do not
have a literature reference for the density of propane at LOX temperatures, but
by extrapolation of data on density from 20 C to -110 C the density at - 183 C
would appear to be about 0.75.  For comparison purposes, the density of
kerosene-like materials varies from about 0.76 to 0.81 depending on the nature
of the hydrocarbon mix.
     One complication about talking about the density of propellants is that it
is not just the density of the fuel that matters, but the overall density of
the propellant mix, including oxidizer.  For hydrocarbon fuels, the maximum
specific impulse is always for a fuel-rich mixture, not for a stochiometric
mixture.  One reference I have has a chart which indicates that the maximum
specific impulse for LOX and RP-1 occurrs at a bulk density of about 1.04.  The
corresponding figure for LOX and CH4 is about 0.84, with the specific impulse
for the LOX and CH4 being about 3% higher than for LOX and RP-1.
     It is simplistic to try to derive a single figure of merit for Isp and
propellant density as the relative importance of density and Isp vary at
different stages of a rocket ascent.  It turns out that near the beginning of
the flight density has much more importance, while for upper stages Isp is more
important.  High Isp overrides density for upper stages because upper stages
are accelerated to high velocities and their mass is dominated by their fuel.
If a lower stage can only lift 10 tons of upper stage, it pays to have an upper
stage filled with LOX and LH2 rather than LOX and RP-1.
     The relative importance of propellant density near the beginning of the
flight and specific impulse near the end of the ascent is reflected in many
launch vehicles such as the Saturn or Titan/Centaur which use dense but low Isp
propellants in the lower stages, and LOX and LH2 in the upper stage(s).
Researchers modeling single stage to orbit vehicles have found it advantageous
to have both hydrocarbon engines and hydrogen engines on board - the former for
the beginning of the ascent and the latter for the end of the ascent.
Dual-fuel engines which switch from hydrocarbons to hydrogen at the appropriate
point in the ascent have also been proposed.
     - Bruce

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

Date: 10 Feb 90 21:14:58 GMT
From: galaxy.rutgers.edu!argus!ken@rutgers.edu  (Kenneth Ng)
Subject: Re: Kepler fudged the Numbers?

In article <7943@hubcap.clemson.edu>, panoff@hubcap.clemson.edu (Robert M. Panoff) writes:
: I have heard (or read) recently that Kepler fudged his numbers.  
: He claimed to have an independent check on his theory, but the charge 
: is used the theory to calculate the numbers he said verified his theory.
: Could someone point me to a specific published article that gives 
: the particulars of this subterfuge?

New York Times Science Times, page C1, 23 January 1990.  That should at least
be a good starting point.

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

End of SPACE Digest V11 #32
*******************