Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v10_4/v10_427.txt

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Subject: SPACE Digest V10 #427

SPACE Digest                                     Volume 10 : Issue 427

Today's Topics:
     Re: Why did Solar Max fall but space junk stays up?
     Re: Why did Solar Max fall but space junk stays up?
            Re: Nuclear Reactors in Space
            Re: Nuclear Reactors in Space
        Navstar Global Positioning System News
             Re: KSC tours (long)
----------------------------------------------------------------------

Date: 12 Jan 90 22:02:59 GMT
From: mnetor!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Why did Solar Max fall but space junk stays up?

In article <[e-mail]> [e-mail] (BakerRC) writes:
>If these monster satellites can't stay up for even 1 solar cycle
>(and I believe they were fairly high) how the heck can all that tiny
>space junk stand a chance. It seems every 11 years it would get cleaned up.
>I'm obviously wrong, since space junk is a problem. So where am I wrong?

You're assuming that the big birds are high up.  Not always.  Remember,
Solar Max got a shuttle visit several years ago (the same mission that
deployed LDEF), and the shuttle just can't get very high.  Space debris
also lacks big air brakes, aka solar arrays, which most satellites have.
--
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry [e-mail]

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

Date: 14 Jan 90 04:30:06 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Why did Solar Max fall but space junk stays up?

In article <[e-mail]> [e-mail] (Tom Neff) writes:
>... Most booster
>separations are done pyrotechnically, which means multiple clouds of
>particles exploding outward in space...

Modern pyrotechnic joints do not emit debris; the explosion is confined to
the interior of a metal tube, which deforms enough to kick the pieces
apart but not enough to vent itself to space.  This is not just a matter
of minimizing debris, it's also a question of not contaminating costly
satellites with pyro debris.  I'm not sure how universal this technology
is, although I believe all current US hardware uses it.

>...the interstage covering of the expended stage is often shredded
>by rocket exhaust...

Staging normally occurs before orbit insertion, however.

>And every so often the Soviets render a dying
>military satellite worthless to scavengers by simply exploding it!

Normally this is done only for birds that are about to make an uncontrolled
reentry anyway.  The Soviet Asat tests were a different, and much more
troublesome, story, but they haven't run one of those for years.

>Two, many satellites have lots of reboost capability in their
>maneuvering rockets.  Their orbits are periodically adjusted to
>compensate for drag and tidal effects; you just don't hear about it.

That doesn't really answer the original question, though, since Solar
Max had no maneuvering system.  Actually, a lot of low-orbit satellites
don't, since it adds weight and complexity, roughly triples launcher
safety paperwork, and adds contamination problems, for minimal return.
Clarke-orbit comsats are unusual in that they need to maintain precise
orbits; most low-orbit birds don't.
--
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry [e-mail]

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

Date: 13 Jan 90 07:36:05 GMT
From: att!watmath!watserv1!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (John McKernan) writes:
>... Sweden is implementing reactors with active controls
>which sustain the reaction. In the absense of such controls the reaction
>passively stops. The US is studying such reactor designs.

Such reactors have been implemented and in operation for quite some time,
actually.  There's one about two kilometers from here (I'm at home), in
the middle of downtown Toronto:  the Slowpoke research reactor at U of T.
When the last grad student is done with it for the day, he switches it
off, turns out the lights, and goes home, leaving the reactor unattended.
You could wreck the control panel with a sledgehammer without endangering
anybody.

The main problem with Slowpoke, and similar designs, is that they make
lousy power reactors:  they are big and heavy for their output, and they
don't scale well.  The Swedes and others are studying more versatile
designs.  None of the ones that I've seen details on would be relevant
to space power, though, unless cost per kilo to orbit drops *vastly*.
--
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry [e-mail]

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

Date: 14 Jan 90 00:13:07 GMT
From: pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!usc!cs.utexas.edu!jarvis.csri.toronto.edu!helios.physics.utoronto.ca!ists!yunexus!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Tim Maroney) writes:
>... any non-military satellite should
>be able to get by perfectly well with solar power, so why take even
>this small risk?  (Military satellites, of course, need the lower
>profile afforded by nuclear power.)

There are at least two other reasons for using reactors in Earth orbit,
either of which might apply to non-military birds:  continuous output,
and low air drag.  Solar arrays yield zero power about 40% of the time
in low orbit, which is a real problem with energy-storage technology as
poor as it is today.  (The space station is going to need an entire
shuttle mission every few years for battery replacement.)  And big solar
arrays have lots of drag, which is a major problem to anything that wants
to operate in the lowest possible orbit -- this is probably a large part
of why the Soviet radarsats are nuclear.

*Current* civilian satellites can get by perfectly well with solar power.
That is not necessarily true for future ones.  Unfortunately so, because
low orbit is definitely not a good place for reactors until we get a
healthy space program.  (Multi-million-dollar assets containing hazardous
materials do not fall out of orbit in a healthy, well-planned program.)
--
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry [e-mail]

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

Date:        Sat, 13 Jan 90 11:50:20 AST
To: [e-mail],
        "Space Digest" <[e-mail]>,
        "Info-Hams Digest" <[e-mail]>
From: [e-mail]
Subject:     Navstar Global Positioning System News

GPS News from CANSPACE

Air Force Space Command to Operate GPS Mission Control
------------------------------------------------------

The U.S. Air Force's Space Systems Division has turned over Mission
Control Center 1A at Falcon Air Force Base, Colorado, to Air Force
Space Command.  The move includes satellite control functions of the
growing Navstar Global Positioning System (GPS) constellation of
spacecraft.  Development of full GPS control capability is scheduled
for completion later this year.

(Source:  Aviation Week & Space Technology, issue of 1 January 1990)


New GPS Navigation Receiver
---------------------------

Flight testing has begun with a C/A-code GPS receiver developed by the
French avionics consortium Sextant Avionique.  The NSS100S receiver
was installed on a Caravelle transport operated by the French CEV
flight test centre.  Follow-on tests will include evaluations on the
receiver coupled with Sextant Avionique's Nadir navigation and mission
management system.

(Source:  Aviation Week & Space Technology, issue of 1 January 1990)


GPS Makes it to Primetime!
--------------------------

A reference to the Navstar Global Positioning System was made in a
recent episode of the popular night-time TV soap "Dallas."  One of the
recommendations made by a committee, headed by Cliff Barnes,
investigating a collision between two tankers in the Gulf of Mexico
was that "GPS radar" should be included in every ship's navigation
arsenal.  I don't know what "GPS radar" would be but it's interesting
to note that the general public, or at least soap writers, are
becoming aware of GPS.

(Source:  Personal viewing of RBL - yes, I do watch the box from time
to time)


Launch of 6th Navstar Block II Satellite Delayed
------------------------------------------------

The launch of a Delta rocket carrying the 6th Navstar GPS Block II
satellite from Cape Canaveral originally planned for 11 January has
been delayed until next week.
NASA Select TV will carry the launch.

(Source:  NASA Headline News of 8 and 9 January 1990)

========================================================================
Richard B. Langley                BITnet:  [e-mail] or [e-mail]
Geodetic Research Laboratory      Phone:   [phone]
Dept. of Surveying Engineering    Telex:   014-46202
University of New Brunswick       FAX:     [phone]
Fredericton, N.B., Canada
E3B 5A3
========================================================================

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

Date: 13 Jan 90 22:04:55 GMT
From: umigw!mthvax.cs.miami.edu![e-mail]  (David Lesher)
Subject: Re: KSC tours (long)

In article <[e-mail]> [e-mail] (John Roberts) writes:

>There's a proposal to open an annex
>at Washington Dulles (not National) Airport in Virginia, for the display
>of numerous airplanes. Supposedly the prototype space shuttle Enterprise is
>already sitting in some obscure spot at the airport for eventual inclusion
>in the display.

It was there when I was on the back 40 of Dulles for, of all things,
fire-fighting school. (There is a area the a/p fire department uses
for training. We 'borrowed' it for an afternoon and left with a renewed
respect for mother nature)  We got a chance to stop and look the
beast over. You could see some damaged tiles. Sure has big
tires. As a matter of fact, the whole thing is HUGE. You cannot
appreciate it until you are standing underneath.

I assume it's still there. I seem to recall the cost to move it to BWI
(when there was a plan to put the annex there) was in the millions.
--
A host is a host & from coast to [e-mail]
no one will talk to a host that's close..............(305) 255-RTFM
Unless the host (that isn't close)......................pob 570-335
is busy, hung or dead....................................33257-0335

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

End of SPACE Digest V10 #427
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