Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_4/V11_419.TXT

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Date: Fri, 18 May 90 02:16:48 -0400 (EDT)
Subject: SPACE Digest V11 #419

SPACE Digest                                     Volume 11 : Issue 419

Today's Topics:
        Re: space news from Dec 11 1989 AW&ST
                 Re: Magellan
              Re: The Vatican Connection
               Re: Oxygen prebreathing
        Re: space news from Dec 11 1989 AW&ST
             spacesuits and prebreathing
              Re: SPACE Digest V11 #415
         Galileo lateral thruster performance
    Re: Terraforming Venus (was: Manned mission to Venus)
            Re: Terraforming Venus
               GPS/NAVSTAR news
            HST Update - 05/17/90
----------------------------------------------------------------------

Date: 17 May 90 14:04:38 GMT
From: mcsun!ukc!edcastle![e-mail]  (A J Cunningham)
Subject: Re: space news from Dec 11 1989 AW&ST

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>Solar Max reenters and burns up Dec 2, over the Indian Ocean.

    Is this the satellite that was repaired on one of the shuttle
missions? What went wrong this time?
        Tony
--
Tony Cunningham, Edinburgh University Computing Service. [e-mail]

    Yuppies think I'm a wino 'cos I seem to have no class,
    Girls think I'm perverted 'cos I watch them as they pass.

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

Date: 17 May 90 17:40:58 GMT
From: agate!shelby!neon![e-mail]  (John Kallen)
Subject: Re: Magellan

In article <[e-mail]> [e-mail] (Raymond Lister) writes:
>  >  Article xxxx of sci.space.shuttle:
>  >  From: [e-mail] (Henry Spencer)
>  >  Letter from James Duval in Pasadena...  "If Columbus or Magellan had
>  >  been victims of the same 'analysis paralysis' that seems to grip NASA
>  >  management, they'd still be pacing the decks pondering the weather,
>  >  food preservation, scurvy and the possible long-term effects of
>  >  constant seasickness and salt air exposure.  Fortunately, they were
>  >  explorers, not bureaucrats...
>Somebody should tell Mr Duval that Magellan died during his fleet's
>circumnavigaton of the globe.

..but he didn't die of scurvy or any nutritional or environmental
problem. He died of a severe case of spear through body. I gather the
Phillipine natives weren't too thrilled with his presence.

Should the astronauts going to Mars bring .45 automatics? Or maybe
they should "nuke it from orbit. It's the only way to be sure..."

>Raymond Lister
>Internet: [e-mail]
_______________________________________________________________________________
 | |   |   |    |\ | |   /|\ | John Kallen        Computer: kom-pyu'-ter (n) a
 | |\ \|/ \|  * |/ | |/|  |  | PoBox 11215         device for generating errors
 | |\ /|\  |\ * |\ |   |  |  | Stanford CA 94309   speedily and unpredictably.
_|_|___|___|____|_\|___|__|__|[e-mail]___________________________

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

Date: 17 May 90 09:49:14 GMT
From: mcsun!ukc!icdoc!syma![e-mail]  (Nick Watkins)
Subject: Re: The Vatican Connection

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>Some have argued that Galileo would probably have gotten along fine with
>the Church if he'd just been a bit more diplomatic.  As it was, he basically
>got a slap on the wrist -- the things he was charged with normally carried
>the death penalty.
Very good Scientific American article a few years ago spelling all this out
btw. You may have been thinking of it also.

Nick


--
Dr. Nick Watkins, Space & Plasma Physics Group, School of Mathematical
& Physical Sciences, Univ. of Sussex, Brighton, E.Sussex, BN1 9QH, ENGLAND
JANET: [e-mail]   BITNET: [e-mail]

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

Date: 17 May 90 23:47:18 GMT
From: b-tech!kitenet![e-mail]  (Russ Cage)
Subject: Re: Oxygen prebreathing

In article <[e-mail]> [e-mail] (John Roberts) writes:
>Oxygen bubbling
>never seems to be mentioned. Is that because the oxygen is chemically bound
>to the hemoglobin in the blood?

More to the point, the body consumes oxygen quite rapidly compared
to the amount which is soluble in body fluids.  Any oxygen coming
out of solution would be metabolized quite rapidly.  Further, the
pO2 in the body tissues is smaller than in the air so it would
take a much greater pressure drop to create oxygen embolisms.
Nitrogen is not metabolized and is in solution in equilibrium.

Lastly, one of the biggest problems from nitrogen embolism is
that it blocks blood flow to tissue, causing its death from
anoxia.  An oxygen bubble will feed the tissue around it
quite well, and will not exist for long in any case.
--
              Oversimplification doesn't solve problems, it just
[phone]          changes them into less tractable problems.
Russ Cage, Robust Software Inc.            [e-mail]

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

Date: 18 May 90 03:41:47 GMT
From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: space news from Dec 11 1989 AW&ST

In article <[e-mail]> [e-mail] (A J Cunningham) writes:
>>Solar Max reenters and burns up Dec 2, over the Indian Ocean.
>
>    Is this the satellite that was repaired on one of the shuttle
>missions? What went wrong this time?

Yes.  Nothing really went wrong, except that its orbital life was not
quite as long as hoped and there was a severe shortage of shuttle
missions when it became clear that Solar Max needed a reboost.  Given
the backlog of ultra-high priority missions (e.g. LDEF retrieval, HST,
Galileo, USAF missions [the USAF has override priority by Presidential
decree]), NASA just couldn't fit a reboost mission in.
--
Life is too short to spend    |     Henry Spencer at U of Toronto Zoology
debugging Intel parts. -Van J.| uunet!attcan!utzoo!henry [e-mail]

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

Date: 17 May 90 03:40:00 GMT
From: clyde.concordia.ca!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: spacesuits and prebreathing

In article <[e-mail]> [e-mail] (Tim Porter) writes:
>Does this mean that any time it becomes necessary to don a spacesuit and
>step out of the shuttle, an astronaut must first spend "quite a while"
>pre-breathing?

Yes.

>Sort of makes the idea of an emergency space-walk fairly
>difficult, doesn't it?

Yup.  This is why the Atlantis astronauts started preparations for a
Hubble-repair EVA long before anyone had any indication it would be
needed.  (And in the end, it wasn't.)

>Or are there other reasons why an emergency space-
>walk would be unfeasable?

It's kind of a hairy thing to contemplate, given the usual pattern of
trying to rehearse everything far in advance, but the prebreathing
requirement is the only absolute obstacle that I know of.
--
Life is too short to spend    |     Henry Spencer at U of Toronto Zoology
debugging Intel parts. -Van J.| uunet!attcan!utzoo!henry [e-mail]

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

Date: Thu, 17 May 90 11:22 EST
From: [e-mail]
Subject: Re: SPACE Digest V11 #415
X-Envelope-To: [e-mail]

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

Date: Thu, 17 May 90 19:57:52 EDT
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Galileo lateral thruster performance


>From: swrinde!zaphod.mps.ohio-state.edu!sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)

>                     GALILEO MISSION STATUS
>                          May 16, 1990

>...Two maneuver portions totalling 2920 pulses from the lateral thrusters...
>...The result was a velocity change of about 11 meters per second (25 mph)...

I've been meaning to calculate the performance of the lateral thrusters.

Additional information from previous postings:

 - Spacecraft mass: orbiter - 2400kg, including 1090kg fuel
                    probe   -  340kg
                    total   - 2740kg  (Since this is early on the trip, we
    can presume that not much fuel has been consumed, so this total is used.)
 - Thrusters fire in pulses of about a second.
 - A previous maneuver took 6372 pulses and used 23.2kg of fuel.

Calculations:
 The total impulse of the recent maneuver was 2740 x 11 = 30140 N-s (kg x m/s).
Therefore each pulse provided an impulse of ~10.3 N-s, and with one second
duration, the thrusters fire with a force of 10.3 Newtons. The fuel consumption
per pulse is .00364kg, so the average exhaust velocity is 10.32 / .00364
 = 2840 m/s. This gives an average specific impulse of ~290 - not bad for
a small thruster firing in short bursts.

Does this look reasonable?
                  John Roberts
                  [e-mail]

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

Date: 17 May 90 09:54:57 GMT
From: zaphod.mps.ohio-state.edu!samsung!munnari.oz.au!sendai![e-mail]  (Matthew Yow Ming KWAN)
Subject: Re: Terraforming Venus (was: Manned mission to Venus)


OK, here's a really over-the-top suggestion for terraforming Venus.

Remember in Niven's "A World Out of Time" they "floated" a huge rocket
in Neptune's atmosphere and used the atmosphere as reaction mass, so
that Neptune could be moved around for planetary engineering purposes.

How about putting a "rocket" like this on Venus. There are several
advantages :
1) Obviously you get less atmosphere. Keep it going until your happy with
    the pressure.
2) Since it sucks the atmosphere out from the bottom you get rid of
    the nasty heavy gases (H2SO4 etc)
3) Tilt the rocket and you induce rotation.
4) You can probably move to a higher orbit (assuming the power is
    variable, or that you don't want rotation)
5) If your aim is good enough you could warm up Mars, and MAYBE give it
    some more atmosphere.
6) It would attract the attention of any nearby ET's.

Supporting figures.
Let's assume Venus' atmosphere makes up 1/10,000th of its total mass.
If you can accelerate it to (say) 10% lightspeed you'll give Venus
a delta V of ~3,000 m/s. Maybe that's unreasonable, but you could
surely at least induce rotation.

Now for the tricky bit - designing the rocket. I don't think it's
feasible to build a rocket that stretches all the way from ground level
into space (at least not supporting the kind of forces we're talking
about). So you'd have to blow it out (effectively) from the surface.
I really don't know how effectively you could blow the propellant
through the atmosphere - set up some kind of whirlwind around the stream
perhaps? Or maybe the sheer strength of the stream would simply take
the gases above it along with it.
Powering the rocket. The only way I can think of is some kind of fusion
ramjet, perhaps combined with a particle accelerator powered by the
fusion process itself. Sure, making carbon, oxygen, and sulphur undergo
fusion is tough, but I'd say it's one of the least of our worries.

Anyway it's no more ridiculous than many of the other ideas.
Personally I'd use Venus as a toxic waste dump or an environmental
testbed (just what is the effect of a gigaton bomb on a planet? would
a nuclear winter really occur? etc). Too much effort to terraform.

-------------------------------------------------------------------------
Matthew Kwan
    - "The man with no .signature"

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

Date: 17 May 90 10:13:01 GMT
From: mcsun!ukc!stc!root44![e-mail]  (Jeremy G Harris)
Subject: Re: Terraforming Venus

Someone mentioned Venusian blinds, and it set me thinking - always a
dangerous thing to happen given my lack of real knowlege... but doesn't
the greenhouse effect involve positive feedback?

Would it help at all to freeze out (some of) the atmosphere?

Place (one or more) mirrors in orbit to shade the planet, wait,
remove, then apply suitable combinations of asteroidal bombardment
and algae seeding.  Wait and watch.

How much total mirror area would be needed?   In how many units?
How long would it take?
Assuming aluminised mylar, spun, how much mass?  Any better materials?
Would they have to be in a sun-synchronous orbit, or will any
vaguely-equatorial one do?
Am I right in guessing that low orbits would be preferable?
How could they be cleared away after the job was done?
--
Jeremy Harris            [e-mail]            [phone]

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

Date: Thu, 17 May 90 18:07:06 -0400 (EDT)
From: James Price Salsman <[e-mail]>
Subject: GPS/NAVSTAR news


From _Data_Communications_ (ISSN 0363-6399) vol. 19, no. 6, May 1990, page 56
(c) 1990 McGraw-Hill Inc, reproduced without permission.

DOD DITHERS DIGITAL DATA

Telephone network synchronization is an unlikely topic for heated
controversey, but that is what the U.S. Department of Defense has
provoked by tampering with the Navstar Global Positioning Satellite
(GPS) system that AT&T plans to use as a network clock.

GPS is a group of 13 satellites now in operation and 27 more to be
launched by 1994 [I believe this is in error, as there are to be
27 total satellites in the constellation --jps], each of which
produces and encrypted P code that the military uses to guide missles,
and another signal, called the Clear/Acquisition signal, that has
been available for commercial uses like surveying and timing
communications networks.

But the DoD has decided that even the C/A signal is too accurate
to be generally available, so it has begun a practice it calls
"selective availability."  That delicious piece of bureaucratese
means that the DoD will introduce random noise on the C/A signal,
known in some circles as "dithering," to make it dificult or even
impossible to use.

Meanwhile, some commercial equiptment manufacturers and users, such
as land surveyors, are already relying on the signal and now are
angry that the DoD is changing the rules.  "There is a big
controversey about why the government is doing this," says Jim
Jespersen, a staff member of the time and frequency division of
the National Institute of Standards and Technology (Boulder, Colo.),
"especially since the threat from the Russians is not so severe."
[The "Russians" have a very accurate GPS system of their own,
called GLONASS, so someone is confused here... --jps]

GPS is run by the U.S. Air Force Systems Command's Space Division
in Los Angeles.  The officer in charge of the project, Col. Marty
Runkle of the Joint Program Office, could not be reached for comment.

As for AT&T, George Zampetti, a Bell Laboratories scientist who
is in charge of developing AT&T's synchronization scheme, says
that the company plans to use the C/A signal even if it is
ditthered.

Zampetti and John Abate, another Bell Labs scientist, say AT&T
will use 3B2 computers to filter out the noise to get close to
the true signal.  Filtering will slow down but not eliminate the
use of GPS, Abate says.

"We could go a month and still maintain" on error in 100 billion
events, Zampetti says.

The key to the system is Rubidium clocks that actually pass timing
to AT&T's switches and transmission network.  Those Rubidium clocks
can maintain network timing to meet requirements of ANSI and CCITT
standards, Zampetti says.  AT&T would use GPS to calibrate and monitor
the rubidium clocks.                          -John T. Mulqueen

[The main article (of which that was a sidebar) talks about MCI
and Sprint's use of Loran, atomic clocks, and describes GPS.
The ANSI standard in question is T1.101, by committee T1X1.3,
which describes syncronization for high-bandwidth long-haul
digital transmission. --jps]

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

Date: 17 May 90 21:38:06 GMT
From: usc!zaphod.mps.ohio-state.edu!sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: HST Update - 05/17/90


                  Hubble Space Telescope Update
                          MAY 17, 1990

The Hubble Space Telescope successfully completed the
pattern match portion of a 38-hour command load last night.  The
telescope's fine guidance sensors observed stars during each
pattern test, and confirmed acquisitions of guide stars in six of
the seven tests.  The pattern match sequence is a test between
predicted star patterns and points of light actually observed by
the telescope's fine guidance sensors.   "First light," the first
image taken by a science instrument, will occur sometime during the
second part of Bootstrap Phase A -- probably not earlier than
Sunday afternoon, according to Dr. Edward Weiler, Hubble Space
Telescope mission scientist.  Operators believe the quality of the
image should be comparable to images received by ground-based
telescopes on a dark night.  When the telescope is fully
operational, engineers expect to see more than 10 times better than
ground-based observations.
       _   _____    _
      | | |  __ \  | |       Ron Baalke           |  [e-mail]
      | | | |__) | | |       Jet Propulsion Lab   |  [e-mail]
   ___| | |  ___/  | |___    M/S 301-355          |
  |_____| |_|      |_____|   Pasadena, CA 91109   |

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

End of SPACE Digest V11 #419
*******************