Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_2/V13_241.TXT

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Subject: SPACE Digest V13 #241

SPACE Digest                                     Volume 13 : Issue 241

Today's Topics:
              Re: Space Profits
         NASA Headline News for 03/06/91 (Forwarded)
                  Re: Thrust
      Re: Why bother? (was Re: Terraforming, sun shield)
              Re: SPACE Digest V13 #219
              Re: Fire in Space
                Re: Dyna-Soar

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription requests,
  should be sent to [e-mail], or, if urgent, to
             [e-mail]

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

Date: 6 Mar 91 20:32:30 GMT
From: dog.ee.lbl.gov!hellgate.utah.edu!cs.utexas.edu!sun-barr!newstop!exodus!concertina.Eng.Sun.COM![e-mail]  (Steve Hix)
Subject: Re: Space Profits

In article <[e-mail]> [e-mail] (Doug Mohney) writes:
>In article <[e-mail]>, [e-mail] ("Allen W. Sherzer") writes:
>>
>>Yes but I doubt it would be that hard when it is done in a standard
>>way and everybody does it. This would also have the advantage of allowing
>>satellites to be refueled thus making their operational lives much longer
>>and reducing costs. Remember, a replacement for a satellite which is in good
>>working order but just ran out of fuel will set you back hundreds of
>>millions. It would be worth a lot of money to be able to refuel it.
>
>Assuming that your satellite will last as long as the capability to refuel it.
>It's probably cheaper to send up a new-improved (com) sat, with better
>capabilities than to refuel an (older, less capable) one, even over time.

For now, yes.

There will come a time when the rate of improvement of optics and electronics
will slow enough that refueling existing satellites would make economic
sense.

Launch costs still need to come down enough that off-earth operations
reduced delta-vee benefits aren't eaten up by immense costs of starting
them up in the first place.

--
------------
  The only drawback with morning is that it comes
    at such an inconvenient time of day.
------------

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

Date: 6 Mar 91 23:37:11 GMT
From: [e-mail]  (Peter E. Yee)
Subject: NASA Headline News for 03/06/91 (Forwarded)


             Headline News
Internal Communications Branch (P-2) NASA Headquarters

  Wednesday, March 6, 1991    Audio Service: 202 / 755-1788

This is NASA Headline News for Wednesday, March 6, 1991

Technicians continue working on all three orbiters at Kennedy Space
Center.  On Discovery, hypergolic propellants have been off-loaded
from the orbital maneuvering system and reaction control system
tanks.  Rollback to the Vehicle Assembly Building is set for 2:00
am tomorrow, with arrival at the VAB expected by daybreak.

In the Orbiter Processing Facility, work to prepare Atlantis for
rollover to the VAB is progressing well.  Midbody and aft compartment
closeout activity continues.  Technicians are in the process of
troubleshooting one of the main power busses to determine the
source of intermittent electrical spikes.  Rollover to the VAB is
expected to occur no earlier than Friday morning.  During a
teleconference this afternoon, space flight management will consider
the impact of several hairline cracks found on Atlantis' external
tank umbilical door closing mechanism hinges.  The cracks were found
after several dye penetrant tests and borescope inspections.  Space
flight management expects to resolve this issue prior to the
rollover of Atlantis.

Meanwhile, the transfer of Atlantis' STS-37 Gamma Ray Observatory
payload, from the Vertical Processing Facility, has been rescheduled
from Friday to early morning Sunday.  On Friday, Kennedy Space
Center and Gamma Ray Observatory project management will
hold a press briefing and tour of the spacecraft in the VPF at
1:30 pm.

Work on Columbia is also progressing on schedule with various
systems inspections and tests being conducted in the OPF.
Columbia's Spacelab habitable module is expected to be
transported from the Operations and Checkout Building to the
OPF around March 23.

                   * * * * * * * * * * * * * * * *

The House Subcommittee on Space has called William Lenoir to
testify on the Office of Space Flight's budget request.  That
hearing is set for 1:30 pm today in room 2318, Rayburn House Office
Building.  It will be televised live on NASA Select TV.  Also today, the
House Subcommittee on Energy has called Arnold Aldrich,
Aeronautics and Space Technology chief, to testify about the SP-
100 program.





Here's the broadcast schedule for Public Affairs events on NASA Select
TV.  All times are Eastern.  NASA Select TV is carried on GE Satcom
F2R, transponder 13, C-Band, 72 degrees W Long., Audio 6.8,
Frequency 3960 MHz.

Wednesday, 3/6/91
     1:15 pm    Magellan-at-Venus status report live from the Jet
            Propulsion Laboratory.

     1:30 pm    House Subcommittee on Space hearing, William Lenoir,
            Associate Administrator for Space Flight, to testify
            on the space transportation budget request, live from
            the Rayburn House Office Building, room 2318.

Thursday, 3/7/91
    12:00 pm    Starfinder program  "Gravity and Weight."

    12:15 pm    NASA Life Sciences Program.

    12:30 pm    Assignment "Shoot the Moon."

     1:00 pm    Science Education Lecture.


All events and times may change without notice.  This report is filed
daily, Monday through Friday, by 12:00 pm, Eastern.  It is a service of
NASA Headquarters Office of Public Affairs.  Contact:  CREDMOND
on NASAmail or at 202/453-8425.

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

Date: 6 Mar 91 19:36:54 GMT
From: usc!wuarchive!emory!wa4mei!ke4zv![e-mail]  (Gary Coffman)
Subject: Re: Thrust

In article <[e-mail]> [e-mail] (John Roberts) writes:
>
>High-Isp engines are very efficient in their use of reaction mass. They are
>by definition very *inefficient* in their use of energy (in many cases only
>a tiny fraction of the efficiency of a typical chemical rocket), so if
>you're going to run one, you'd better have plenty of energy available. In
>practical terms, that means an exotic power source such as sunlight, a
>nuclear reactor (I expect RTGs would not really be practical, due to lower
>power density), fusion, or antimatter.
>
>Please don't take any of this to imply that I don't favor the development
>of high-Isp drives - they're great, as long as you recognize their limitations
>and use them for what they do well. I'm particularly intrigued by the use
>of solar power to run an ion drive - has this been studied?

Not a high Isp drive, but an interesting concept is the solar-electric
steam rocket. AMSAT did a design study on this for launches from the
shuttle. Basically, solar panels charge a battery that drives a heating
element in a water tank that generates steam which is released out a
nozzle. The design was sufficient to get from LEO to GEO and met the
safety requirements for the shuttle. The design offers unlimited fuel,
sunlight, an easily stored and intrinsically safe reaction mass, water,
and easy restartability. I don't remember what the Isp was, it should
be in one of the Proceedings of the AMSAT Space Symposiums.

Gary

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

Date: 6 Mar 91 17:06:17 GMT
From: sdd.hp.com!news.cs.indiana.edu!maytag!watmath!watdragon!watyew![e-mail]  (James Davis Nicoll)
Subject: Re: Why bother? (was Re: Terraforming, sun shield)


    I can think of some valid reasons to terraform a currently
lifeless planet like Mars or Venus. They pretty much presuppose
a wealthy society with resources and time to burn.

    'Theological':
        There are a lot of folks who feel life has intrinsic
        value. If Venus or Mars (Or whatever world you care to
        insert) have no life, then perhaps they would feel an
        obligation to introduce lifeforms that could survive there.
        Societies have invested large amounts of labour into
        projects which to outsiders seem non-productive; Egyptian
        pyramids and European cathedrals, for example. I don't
        think it is out of the question that someone in a few
        centuries might decide to devote several trillion dollars
        worth of effort to spreading life throughout the accessable
        universe, particularly if life seems to be very rare at that
        time. Judging by the fuss environmentalists make over changing
        esisting ecosystems, I would guess that one successful attempt
        to introduce life would poison the well for later ones.

    'Condos':
        Hey, habitats wear out in a few centuries. Earth has
        persisted for *5 billion years*. Talk about consistant
        resale value. No, this doesn't make a lot of sense,
        but neither do condos, and they sell well. Wealthy
        societies can afford silly luxuries.

    'Art':
        Think of terraforming as a very large example of
        performance art.

                            James Nicoll

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

Date: Wed, 06 Mar 91 10:08:38 EST
From: tom <[e-mail]>
Subject: Re: SPACE Digest V13 #219

Re: Advanced Propulsion Systems

Mark Gellis asked what might be a good future-style propulsion system.

I'm not sure about the details of exhaust velocity, ISP, etc for most of the
propulsion systems you asked about, but if we're talking about tooling around
the solar system, (or even interstellar space) low thrust isn't a problem,
simce your goal is not escaping a gravity well (which reqiures a particular
acceleration) but just moving around.  The Delta-Vee is the important
thing, rather than how fast you do it, assuming there isn't some impending
emergency.

You might also investigate the ion engine.  It doesn't pollute quite the way
fusion/fission would, nor is it as dangerous as anti-matter engines.  I don't
know which places (besides my own school, Mich. St. U) are doing research, but
a quick visit to the library can fill you in on details.  Ion engines are
particularly neat, because they are already being designed and tested.  I.E.
it's not fantasy, although the chance to use them might be :-(.

Ion engines have the same problem with low thrust, but since they have an
exhaust velocity so much higher than chemical rockets, they are actually more
efficient with what exhaust mass you use.  As an example, huge chemical
rockets burn for around 60 min., and that's all there is.  Ion rockets could
(theoretically) burn for years with the same exhaust mass, and could, so I've
heard speculated, approach relativistic speeds.  Something to look into.
Acknowledge-To: <18084TM@MSU>

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

Date: 7 Mar 91 00:40:53 GMT
From: eagle!earth.lerc.nasa.gov![e-mail]  (Karen J. Rensberger (SVER))
Subject: Re: Fire in Space

In article <[e-mail]>, [e-mail] (Dan Gookin) writes...
>
>I have this perverse curiosity about what fire--specifically a
>flame--would look like in space.
>
>If figure if you lit a match, it probably would lack the familiar
>conical shape the flame has here on earth. In fact, I think it would
>look like a point of light or perhaps a spherical flame.  (And
>then my mind thought "Ooops, pure oxygen atmosphere--Whoosh!)
>
>But what would fire look like in space? or actually, zero-g? Would
>there be flames? Would it be spotty and amorphous? There is no
>scientific reason behind this; just curiosity (a mind-exercise,
>if you will).
>
>dang

The study of flame shapes and properties in microgravity is
an active research area here at NASA Lewis in the Space
Experiments Division.  There has been one shuttle flight
so far, last October aboard STS-41, in which a paper sample
was burned in a controlled environment.  The flame is very
dim, a blue shape, and produced very little soot.  The
lack of buoyancy due to the reduced gravity means that the
heat and mass transfer of the flame is dramatically different
from here on earth.
A large amount of ground-based low-gravity research has been
conducted here at Lewis in the drop tower and aircraft facilities.
A candle flame in low gravity is very dim, blue, and spherical
except for near the wick.  The combustion products diffuse away
from the flame, and oxygen diffuses inward.  There is no need
for air currents to keep the flame alive during the limited
duration testing done to date.  The long term stability of the
flame is not known, and will be the subject of an experiment
in the ESA glovebox, which will be flown aboard USML-1.
The environment aboard the Shuttle is not pure oxygen; we have
learned a few things since the start of the manned space
program!

Karen Weiland
Microgravity Combustion Branch
NASA Lewis, Cleveland, Ohio

(Usual disclaimers.)

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

Date: 5 Mar 91 22:26:14 GMT
From: littlei!intelhf!ichips!omews10.intel.com![e-mail]  (Larry Smith)
Subject: Re: Dyna-Soar


Greg Goebel writes:
>The Boeing X-20 Dyna-Soar
>
>   IEEE SPECTRUM  / AUG 89 / P 18
>
> ...
> ...                                       In 1957, three of those
>programs -- RoBo (for "rocket-bomber" [ED: which was Sanger's original
>proposal]),
> ...

RoBo (I like ROBO), was NOT the ORIGINAL Saenger/Bredt proposal. ROBO was
a USAF funded Bell study for a ROcket BOmber that grew out of an
earlier USAF/Bell boost-glide rocket/recon. bomber study
called BOMI (BOmber MIssile). The BOMI study underwent several reviews
by USAF and NACA, and it eventually evolved into the later USAF funded
Bell studies, called System 118P, Brass Bell, and ROBO. These very
critical Bell studies became the basis, and one of the main motivating
forces (from the USAF's standpoint), behind Dyna-Soar. There were
similarities though, between the original Bell military rocket planes
and the Saenger/Bredt concept. The Bell studies however were the first
to look at the realities of implementation of such a system. They also
helped drive further studies to promote the development of technology
for this type of system (HYWARDS, Dyna-Soar).

Many people, although knowing about Bell's X-1 and X-2 rocket planes,
have never heard of these military rocket planes studied in the 50's by
Bell.

Also, it seems to me that Bell got screwed in the Dyna-Soar bid.
They were one of the 4 finalists (out of 9 I think). They were then teamed
with Martin for the final bid. Boeing was teamed with Vought. They lost
the final bid. Martin got the nod anyway for the Titan. Vought and Boeing
got the airframe. Bell, who was responsible for a lot of the preliminary
work that begot Dyna-Soar, got almost nothing. Also, I understand that the
final Boeing/Vought design, more resembled the original Bell design, than
their original winning design.

Just so people understand what kind of performance we are talking about,
a representative sub-orbital performance for Brass Bell (recon. mission)
was roughly 170,000 ft and Mach 16! ROBO (bomber/recon. mission) was
orbital.

Originally, these vehicles were all 2-3 stage vehicles. However, unlike
Dyna-Soar, they employed completely reuseable, manned, winged, fly-back
boosters (at least the 2-stagers did - not sure about the intermediate
stage on the 3-stagers). The stages were mounted piggy-back, and had their
own engines. I think the later Brass Bell used a Titan booster.

Also, interestingly, on Dyna-Soar, the pilot was to have some control,
during boost phase, over the Titan as well! They were going to develop
ground based simulators and centrifuges to test the pilots capabilities
during this phase of flight, with emergencies, to see if it was
feasable.

In 1952, Kraft Ehricke, one of Von Braun's group (at ABMA), left Von Braun
for Bell to join Walter Dornberger (Von Braun's boss on the V-2 program) on
the BOMI program. At Bell, Ehricke worked on the Bell military rocket planes
for several years, before going to Convair to work on what became Centaur.

Dornberger also tried to recruit Saenger and Bredt (Saenger's wife)
for the Bell military rocket plane projects as well. Saenger refused the
offer.

> Steven King writes:
>   I'm afraid I'm going to disagree with Henry on this. DynaSoar had a
> mission; its the same mission that the Air Force currently uses aircraft
> for in the atmosphere...

Henry Spencer responds:
>And which the aircraft were, by and large, perfectly capable of doing. :-)

Mach 16 at 170,000 ft. was an EXISTING aircraft? Brass Bell was Dyna Soar
Phase II and sub-orbital. ROBO was Dyna-Soar Phase III and orbital.

Dyna-Soar was killed by the bean-counters, and the budget. The experts now
know it was a mistake to kill it. Some experts say it set re-entry
physics back about 10 years.

Steven King writes:
>   Its interesting that in some of the SDI literature, one sees a line
> drawing of a DynaSoar like vehicle atop a Titan like rocket...

Yes, the bean counters decided to replace Dyna-Soar first with the ASSET
vehicle, and then the PRIME (X-23) vehicle. Both unmanned hypersonic
lifting-body re-entry vehicles. Also the current NASA Personnel Launch
System (PLS) atop a Titan 4 looks similar to Dyna-Soar poised for launch.

Don't believe the comments about "we don't know what we would use a
hypersonic orbital/sub-orbital system for". There were several high
ranking USAF generals at the time (Gen. Powers was one) who were quite
interested in these military rocket planes and wanted to see their peers
show a little daring in promoting the investigation and possible development
of these unconventional systems.

Also remember this was the time period of other interesting bids. For example,
the CIA/USAF funded high speed airbreathing recon. platform that eventually
gave birth to the Lockheed Mach 3+ A-12 Blackbird and the General Dynamics
Mach 6 Fish/Kingfish concept. These bids were being evaluated, we now know, in
1958-1959, by USAF-ARDC and CIA. USAF-ARDC also supervised the Bell military
rocket plane programs. USAF-ARDC is now the USAF Systems Command I believe.

Steve King writes:
>   Much of the vehicle was quite simple, even primitive by todays standards.
> There was a statement in one document to the effect that the cockpit
> enviromental control system would work better if the pilot kept his
> helmet visor closed.
>   It was because of this simplicity that I was interested in the design. It

For simple ... how about the Sandia-SWERVE-like, civilian Space Cruiser concept
(Cislunar Space Corp.)?

Larry

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

End of SPACE Digest V13 #241
*******************