Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v11_0/v11_097.txt

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Subject: SPACE Digest V11 #97

SPACE Digest                                      Volume 11 : Issue 97

Today's Topics:
               Experimentation
          Re: Spacecraft drives and fuel efficiency
             Re: long-term Venus landers
               Re: SPACE Digest V11 #80
              Pegasus Update - 03/01/90
         Re: Geosync DSN (was Re: Cheap DSN?)
               Re: HST damage in orbit
               Giotto Update - 02/26/90
              Re: Challenger Last Words
         Re: Geosync DSN (was Re: Cheap DSN?)
               Re: Cheap DSN?  (errata)
              Re: Challenger Last Words
----------------------------------------------------------------------

Date: 26 Feb 90 21:38:01 GMT
From: zaphod.mps.ohio-state.edu!math.lsa.umich.edu!sharkey!cfctech![e-mail]  (Joel Lessenberry)
Subject: Experimentation


        I understand that these days the world would rather simulate
        than experiment, but... has anyone even worked in planning
        simple missions to actually demonstrate new propulsion
        technologies?  Surely this type of experimentation could be
        done by *someone* without the 20 year, multi billion dollar
        design cycles which are so prevalent.

        Along the same lines, has anyone considered the highest velocity
        obtainable using current technology.  Again, the sole effort of
        the project would be speed...so to speak.

        It seems to me that a long time ago we used to conduct experiments
        along these lines, on a timely basis, and efficiently.

                                Joel


 Joel Lessenberry, Distributed Systems | [phone]
 [e-mail]                     | Chrysler Financial Corp.
 [e-mail] | MIS, Technical Services
 {sharkey|mailrus}!cfctech!joel        | 2777 Franklin, Sfld, MI

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

Date: 28 Feb 90 17:49:18 GMT
From: usc!zaphod.mps.ohio-state.edu!uwm.edu!cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!watserv1!watdragon!watyew![e-mail]  (Brian or James)
Subject: Re: Spacecraft drives and fuel efficiency


 The nice thing about Antimatter as a fuel is that while disposal could
involve environmental difficulties if done on Earth, the problem would
be of extremely short duration :)

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

Date: Thu, 1 Mar 90 09:43:24 PST
From: [e-mail] (Peter Scott)
Subject: Re: long-term Venus landers

John Roberts <[e-mail]> writes:

> Some of the electronics might be
>able to operate at local temperature (for instance, vacuum tube technology,
>if it can be made dense enough).

Check out the current _Discover_ (no flames, please, I haven't seen this
work written up elsewhere yet) for an article on micro-vacuum tube
technology, component size on the order of 1 micrometer.  It's not
there yet, but it looks promising.  Should be able to handle the local
temperature.

Peter Scott ([e-mail])

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

Date: 1 Mar 90 06:16:04 GMT
From: unmvax!nmtsun![e-mail]  (Daniel Briggs)
Subject: Re: SPACE Digest V11 #80

In article <[e-mail]> [e-mail] (Platypi go 'Quack!') writes:
>Does anyone know the coordenats for the center of the Galaxy?  Including right acclination.

17h42m24s  -28d55'  epoch 1950.0  (Blaauw et.al.  MNRAS, 121, 123, 1960)

You might be a little careful about posting questions whose answer is as
close as the nearest library.  (People might look at you funny.)  BTW,
that's Right Ascension.

-----
This is a shared guest account, please send replies to
[e-mail] (Internet)
Dan Briggs / NRAO / P.O. Box O / Socorro, NM / 87801  (U.S. Snail)

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

Date: 2 Mar 90 01:52:37 GMT
From: zaphod.mps.ohio-state.edu!mips!bridge2!jarthur!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Pegasus Update - 03/01/90



                              Pegasus Update
                              March 1, 1990

     Launch of the Pegasus satellite (Pegsat) has been
rescheduled for April 4, according to Project Manager Bob Pincus.
Launch had been planned for March 13.  The new date was set this
week to allow for corrections of minor technical difficulties.
Pegsat will be launched from a NASA B-52 over the Pacific Ocean
about 50 miles west of Vandenberg Air Force Base, CA.  Launch
altitude will be 42,600 feet (13,000 meters).  The spacecraft will
be placed in a polar orbit.  Pegsat will deploy a small Navy
experimental communications satellite, measure environmental
factors during the runway and launch phases of the mission and
deploy two chemical discharges to make studies of the atmosphere.

 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

Date: 28 Feb 90 00:34:14 GMT
From: cs.utexas.edu!samsung!brutus.cs.uiuc.edu!jarthur!elroy.jpl.nasa.gov!jpl-devvax![e-mail]  (Larry Wall)
Subject: Re: Geosync DSN (was Re: Cheap DSN?)

In article <[e-mail]> [e-mail] (Ron Baalke) writes:
: In article <[e-mail]> [e-mail] (Tom Neff) writes:
: >It seems to me this is a case where GEO would help.  Deploying a few
: >really BIG guidable antenna arrays in geosynchronous orbit, parked over
: >dedicated ground stations, would allow tracking and commanding probes
: >all over the solar system without usurping valuable observatory time.
:
: BIG guidable antenna arrays are not feasible for earth orbit. A 70 meter
: antenna on the earth weighs 8 million pounds. The cost of placing such
: an antenna into orbit would be astronomcal. And this is before the antenna
: is outfitted for the space environment. Also, how would such large antennas
: be powered in space? What about maintenance when the antenna breaks down?

Who says an orbiting antenna has to be built to take 1g, magnitude 8
earthquakes and 160kph crosswinds?

Shoot, if you aren't interested in microwaves (because you're above the
atmosphere), just launch a big inflatable ball of almost sherical shape
(parabolically distorted), with tin foil on one side.  Maybe the power comes
from the ball next to it that happens to be focused on the sun.  When
it busts you throw another one out there and inflate it.  Of course, this
wouldn't last long in LEO, but we're talkin' a little higher...

The only hard problem is how to suspend something at the focus without
distorting the dish.  Microgravity may help here.  You could have the
horn flying free inside the ball with its own propulsion system.  You
could probably suspend it by playing electrostatic tricks with the dish.
Or save the electrostatic tricks for distorting the dish into mm wave
capability.

Fabrication?  Just take up a BIG jar of high tech bubble fluid...   :-)

Larry Wall
[e-mail]

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

Date: 28 Feb 90 18:26:32 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: HST damage in orbit

In article <[e-mail]> [e-mail] (Steve Willner, OIR) writes:
>> ...I believe observation planning now includes a constraint reading
>> roughly "do not point forward along the orbital velocity vector for any
>> length of time" to protect the optics [against atomic oxygen]
>
>If so, that is quite a serious constraint for any object that lies
>nearly in the direction of the orbit plane...

Actually, either my recollection was wrong or my source was wrong, because
the formal rules don't explicitly include such a constraint.  However, the
HST people are aware of the problem, and I don't think it will spend too
much time pointed that way.

>... No doubt the orbit plane precesses, so any
>object will eventually come to lie in a "good" direction.  Anybody know
>what the precession period is?

If somebody knows the current official word on orbital inclination and
altitude -- I don't, offhand -- it's easy enough to figure out.
--
"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: 26 Feb 90 22:39:44 GMT
From: zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!jarthur!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Giotto Update - 02/26/90


                              Giotto Update
                            February 26, 1990

     Reactivation attempts on Giotto continues. On February 23 the
European Space Operations Center (ESOC) attempted to perform a
spacecraft attitude maneuver as well as test the despin motor of the
High Gain Antenna (HGA). The downlink of the Low Gain Antenna (LGA) was
left on during these attempts. The doppler signature confirmed the manuever
did take place successfully. The doppler signature also indicated
that ESOC was able to control the HGA despin motor. ESOC's first command
sequence (to turn off the spacecraft downlink) did not work. ESOC
had to retransmit the sequence to turn the spacecraft off. There was
no indication of a cause for the first command sequence not being
accepted.

     On February 24 the HGA acquired earth point. The tests started with
a series of telemetry on/off commands to check the command system
responses. Following this, a maneuver was performed to sweep the HGA
past the earth. This manuever was successful. The maneuver was stopped
and a series of small reverse maneuvers was performed to bring the HGA
back to earth point, and was achieved with telemetry in-lock.

 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

Date: 1 Mar 90 21:13:22 GMT
From: elroy.jpl.nasa.gov!jarthur![e-mail]  (John H. Kim)
Subject: Re: Challenger Last Words

In article <[e-mail]> [e-mail] (Mary Shafer (OFV)) writes:
>A while ago (perhaps as early as the early 70s) the US Navy did
>a study of pilot's last words, before crashing or ejecting.  The
>most common remark was "Oh, shit."  The US Air Force confirmed
>this in a later study.

Just so everyone doesn't think people are so bad, the second most
common remark were things like "G'bye mom." and "I love you xxx."
--
John H. Kim                 | (This space to be filled when I
[e-mail] | think of something very clever
uunet!muddcs!jarthur!jokim  | to use as a disclaimer)

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

Date: 28 Feb 90 04:13:41 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Geosync DSN (was Re: Cheap DSN?)

In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>BIG guidable antenna arrays are not feasible for earth orbit. A 70 meter
>antenna on the earth weighs 8 million pounds. The cost of placing such
>an antenna into orbit would be astronomcal.

Radio astronomical? :-) Seriously -- surely most of that weight is devoted
to fighting Earth's pull, not to active elements.  In space you could
string looooong wires with the flimsiest web of composite struts holding
the shape together.

I am not picturing Jodrell Bank in orbit here, more like a gigantic
spindly Y shape with "bent-up" struts supporting three looong antenna
segments, and the collector boomed way out from the center.

>Also, how would such large antennas
>be powered in space?

The power requirements would if anything be less.  Besides electronics for
decoding the signal, which isn't actually part of the antenna, the biggest
non-guidance drain on an Earth antenna is cooling for the horn.  In space
all you need is a sunshield.

Ideally the decoding hardware could be physically decoupled from the
antenna, perhaps with a laser link.  The separate electronics package
could be powered any way you like.

For turning the antenna, fine gyroscopes might do the trick.  I'd love
to hear some ideas from the experts out there.

>What about maintenance when the antenna breaks down?

No moving parts. :-)

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

Date: 1 Mar 90 07:27:45 GMT
From: unmvax!nmtsun![e-mail]  (Daniel Briggs)
Subject: Re: Cheap DSN?  (errata)

In article <[e-mail]> [e-mail] (Daniel Briggs) writes:
>...Stuff about making a DSN out of satellite dishes...

Oops!  I'm not thinking clearly tonight.  In order to make up the factor of
28.5 that you loose from system temperature, you need to increase the
geometrical area by 28.5^2, not 28.5.  In that light, we need about
(25/2)^2 * (1000/35)^2 = 127500 small dishes!!!
This is to make a single, comparatively modest VLA antenna.  (God that number
seems large.  Am I doing something even more stupid than usual?)

Assuming that I'm right this time, my previous comments hold in spades.

-----
This is a shared guest account, please send replies to
[e-mail] (Internet)
Dan Briggs / NRAO / P.O. Box O / Socorro, NM / 87801  (U.S. Snail)

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

Date: 28 Feb 90 13:37:07 GMT
From: ksr![e-mail]  (Chris Jones)
Subject: Re: Challenger Last Words

In article <[e-mail]>, robiner@iris (Steve Robiner) writes:
>Does anyone out there know if the last minutes of the Challenger
>flight recorder were ever released.  If so, where can I get a copy
>or transcript.
>
>About a month or so after the crash, I heard that the NYT was suing
>NASA for the tape, but that's the last I heard of it.
>
>I now see accounts of the crash where NASA officials publicly indicate the
>crew died at impact (with the ocean) and not during the explosion as originally
>speculated.
>
>=Steve=

The transcripts of the in-cabin voice recorders were released.  These pick up
conversation in the flight deck (but not the mid-deck) including stuff not
transmitted over the radio.  I remember reading them in AW&ST.  The tape was a
continuous loop, I believe, and starts from several minutes before the launch
and ends with the explosion, at which time power was lost to the crew cabin.
The things I recall were some bantering among the crew concerning the nose cap
prematurely retracting (it wasn't), Judy Resnick saying "[shit] hot" at
ignition (expletive inferred; NASA censored), and, the last words on the tape,
Michael Smith saying "Uh, oh."  In one of a string of events in which NASA
tarnished its image, they stated two days or so before the transcripts were
released that there was no evidence that the crew had any knowledge that things
were going wrong, then said that further sound analysis of the tape had
revealed Smith's words.

NASA's behavior in the aftermath of the accident often seemed to me to be an
obvious exercise in damage control to the detriment of finding out what went
wrong.

As to the morbid details of what happened in the crew cabin after the
accident, there is no way of knowing.  Certainly the crew's fate was sealed
after the breakup, and the only way they would have had to communicate was via
handwritten notes (a la the passengers on the JAL 747 which crashed several
years ago).  In every respect, what happened to the Challenger was
non-survivable, and the time spent wondering about the crew's fate is better
spent on preventing such accidents.  It seems to me that the details of what
*caused* the accident are sufficiently well known, and I don't feel a need to
know all the lurid details of the tragedy.
--
Chris Jones    [e-mail]    uunet!ksr!clj    harvard!ksr!clj

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

End of SPACE Digest V11 #97
*******************