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Subject: SPACE Digest V13 #358

SPACE Digest                                     Volume 13 : Issue 358

Today's Topics:
           space debris and chaotic orbits
         Re: Commercial Space news (5 of 12)
              Re: How 'bout them Titans?
       Re: Why does every SAR have another resolution?
              Assorted responses
                Re: Mt. Venus

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Date: 1 Apr 91 22:46:45 GMT
From: agate!bionet!uwm.edu!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!pitt!nss![e-mail]  (Paul Blase)
Subject: space debris and chaotic orbits

The following is part of a running conversation I've been having on the
usenet sci.science echo re the probability of orbital debris striking a
satellite.  I repost it here for general interest.


 PB>>>... [edited: conversation re probability of a satellite or shuttle
 PB>>> running into space debris in orbit]
 PB>>> It's not the large stuff that you have to worry about, that
 PB>>> can be and is tracked by NORAD.  It's the paint flecks, loose bolts, and
 PB>>> misc stuff that falls off everytime somebody jettisons a booster.  I
 PB>>> believe the current estimate is that the Hubble can expect to run into
 PB>>> something just big enough to wreck it (about the size of a marble)
 PB>>> within the next 15 years.

(Leslie Rohrer)
 LR>>         I'm skeptical, but in any case, it won't be anything
 LR>>        orbital that does it. It will have to be something NOT
 LR>>  in orbit.


 PB> Found it:
 PB> "What Goes Around, Comes Around: What to do About Space Debris",
 PB> by Dr. Gay E. Canough & Dr. Lawrence P. Lehman; Analog Science
 PB> Fiction/ Science Fact, March 1991, pp54-67.

 PB> Includes bibliography of 28 recent articles on the problem of
 PB> space debris and its consequences.

 PB> Synopsis:
 PB> 1) "Each time a satellite or other spacecraft is launched,
 PB> there are items discarded from it that remain in orbit.  These
 PB> include payload fairings, used upper rocket stages and bolts
 PB> that are blown off as part of pyrotechnic deployment of booms,
 PB> antennae, or solar panels....In addition, solid rocket motors
 PB> have aluminum oxides in their exhaust and these particles may
 PB> be a source of corrosion (by collisional pitting) to other
 PB> spacecraft. Many spacecraft are painted and after they are in
 PB> orbit for a time, the constant cycling in and out of hte sun
 PB> and exposure to atomic oxygen causes the paint to flake off.
 PB> These point flakes, traveling at 7 km/sec ... can cause
 PB> significant damage.  The most famous example of this was a
 PB> space shuttle window (Challenger, 1983) which had to be
 PB> replaced when a 4 mm pit was formed in it by collision with a
 PB> 0.2 mm paint flake.

 PB> 2) "There are over 7,000 trackable objects in orbit", trackable
 PB> by NORAD using radar, over 10 cm in diameter.  "MIT scientists
 PB> set out to get some idea of the population of smaller objects
 PB> in orbit.  Using telescopes, they could see about 8 times the
 PB> number of objects tracked by radar, implying over 50,000
 PB> objects larget than 1 cm." [This does not come close to
 PB> counting all of the paint flecks and bolts up there].

 PB> 3) "In space, debris does not stay put.[!] In fact the orbital
 PB> location of a debris object cannot be predicted for longer than
 PB> a couple of weeks.  After a few months, the object may be found
 PB> with equal probability anywhere within a volume bounded by its
 PB> apogee, its perigee, and the north and south latitude lines
 PB> equal to its inclination".  Chaotic orbital dynamics again.
 PB> What is worse, these things thusly tend to stay in the "space
 PB> lanes" commonly traversed by LEO satellites and the shuttle.
 PB> Oh yes, the stuff inhabits geosync orbit too, although to a
 PB> somewhat lesser degree.

 PB> 4) "A hypervelocity collision of a working spacecraft with a
 PB> 10cm (1.4 kg for aluminum) piece of space debris will
 PB> completely demolish the craft.... An 80 gram piece (3.8 cm,
 PB> aluminum) of debris striking a satellite at 10 km/s has the
 PB> same energy as 1 kg of TNT."

 PB> 5) "....The larget the structure, the higher the probability of
 PB> a hit. Estimates range from 1% to 10% probability that Freedom
 PB> will suffer major damage sometime during its 10-year life due
 PB> to collision....For the Hubble space telescope, there is about
 PB> a 1% chance (over its 17-year life) that it will be severely
 PB> damaged by a collision with debris."

 PB> The article goes on to give further information on the dangers
 PB> of and probabilities of collisions with space debris, and then
 PB> to give suggestions as to what to do about it.

--- via Silver Xpress V2.26 [NR]
--
Paul Blase - via FidoNet node 1:129/104
UUCP: ...!pitt!nss!Paul.Blase
INTERNET: [e-mail]

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

Date: 3 Apr 91 11:35:40 GMT
From: eru!hagbard!sunic!mcsun!ukc!acorn!ixi![e-mail]  (Mike Moore)
Subject: Re: Commercial Space news (5 of 12)

In article <[e-mail]> [e-mail] (Robert McGwier) writes:
>
>And if you will pardon me, WHAT THE HELL does Europe think ESA/Arianespace
>Matra, Daimler-Benz (which now owns MBB), and all the other semi-private
>`corporations' in Europe are but government subsidized and/or out right
>ownership

Can't speak of things I don't know about, but I do seem to recall something
about Chrysler, Ford recieving 'hand-outs' of several million dollars.  Not
to mention equivalent funding for agriculture and, oh yes, the largest industry
in the USA, the military.

>of companies in competition of ours.  The government and treaty granted
>monopolies to INMARSAT, COMSAT,

OK.  They have a right to do so, so do the Japanese, so do the Europeans.

>others in many areas makes me want to puke
>and I can only say IT IS ABOUT TIME THE GD US Government did SOMETHING
>to aid OUR companies who are trying to compete with other companies in an
>international market where these companies are either owned by the government
>or controlled or heavily subsidized by them.

Sorry to say it but you're beginning to blither (a quaint English word meaning
various politely impolite things including, but not limited to, repetition,
confusion, red-faced, spittle scattering hand-waving)

>
>The US is becoming a third world country,

Was it ever anything else?  Millions of people on the poverty line, millions
of people homeless.  A child illiteracy population which is larger than the
total number of children IN THE WHOLE OF THE UK!  Millions of people routinely
denied medical attention (My God!  Your hospitals actually implement triage!)
Political prisoners (Noriega, et al), a foreign policy lacking in maturity
(Vietnam, Korea, Panama, Grenada, Cuba), and a dictatorial head of state - this
guy really could commit troops to a war without needing any democratic vote.

>exporting more scrap

True, but perhaps trash would be more appropriate (?)  IN BOTH SENSES.

  [ for the truly feeble minded:
      (1) trash - garbage, household waste, commercial waste, toxic chemicals
      (2) trash - shoddy workmanship, lacking originality ]

>and raw
>materials

You export raw materials?  Really?  *That* must be where all those computers
come from (for fuller explanation see below)

>and less high tech (high value, high value added manufactured
>goods) each and every day.

Do I detect Japanophobia?  Do I detect resentment that the Japanese are just
plain willing to work harder?  Has the 'land of opportunity' finally begun to
realise that gold does NOT line the streets of every city and that money does
NOT grow on trees?  Has the 'land of the free' finally realised that freedom
has a monetary value?

>I can't understand how or why the US government
>will not make SOME move to encourage there industries.

They could start by lifting trade barriers!  Did you know that the US Govt does
not allow US high tech. companies to export their goods to foreign markets
because of 'national security' (whatever that is).  Even countries like the UK
with it's 'special' relationship is not allowed to buy certain hardware or
software.  For pete's sake, you should have seen the hassle we had just trying
to buy one, *ONE* Cray, when we wanted three the US Govt insisted on having
access to all information that went through it.  Well, the MOD wasn't very
pleased so they built there own - UK 3 USA 0.  (This story is apocryphal)

>
>Bob
>
>--
>____________________________________________________________________________
>    My opinions are my own no matter    |    Robert W. McGwier, N4HY
>    who I work for! ;-)            |    CCR, AMSAT, etc.
>----------------------------------------------------------------------------


Now, will you shut up and let's get back to some space talk OK?

Mike
--
---
Mike Moore
[e-mail] or [e-mail]
Usual and obvious disclaimers... etc

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

Date: 4 Apr 91 18:19:58 GMT
From: usc!samsung!think.com!linus!linus!cyclone![e-mail]  (S. J. Okay)
Subject: Re: How 'bout them Titans?

In article <[e-mail]> [e-mail] (Graham Murphy) writes:
>Shortly after the Titan was destroyed,
>one hears a voice in the background say,
>"Is it supposed to do that?"
>followed by another voice giving a very emphatic "No!"

Hmmm...interesting...kind of like when people cheered when the Challenger
exploded....Any idea if it was the media that made that query?.

---Steve

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

Date: 4 Apr 91 20:21:15 GMT
From: agate!stew.ssl.berkeley.edu![e-mail]  (Eric J. Korpela)
Subject: Re: Why does every SAR have another resolution?

In article <[e-mail]> [e-mail] (Daniel Fischer) writes:
>Now we all know that the Magellan in its orbit around Venus produces swaths
>some 25km wide, with a resolution of approx. 120 meters. Why can the resolution
>of RADARSAT's SAR be so much better, about a factor of 10? This can't be due
>to a lower orbit alone, I presume. Also, why can RADARSAT have many more
>pixels across the swath's width (according to this article 5000) compared to
>Magellan (200)? Does that depend on their antennas or on the data processing?
>
>Furthermore, there are rumors that the Lacrosse satellite's SAR can resolve
>features down to 1 meter in size (how official is that?).

SAR works by illuminating the ground with a short radar pulse.  The return
echos do not form an image the way a camera does.  The imaging is a bit more
complicated than that.  From the return echo you can only get doppler shift
(relative motion of the illuminated feature and the spacecraft) and the
delay time (distance from the spacecraft to the feature).  Lines of
constant delay time and lines of constant doppler shift form a roughly
orthogonal (mathematically, not geometrically) coordinate system on
the planets surface.

The resolution of SAR is therefore proportional to the time resolution obtained
by the reciever and the frequency resolution of the reciever.  You can increase
resolution by increasing either or both of these.

    /\                      [e-mail]              Internet
   /__\  rioch              BKYAST::KORPELA    42215::KORPELA     DecNet
  /    \   of Chaos         korpela%bkyast@ucbjade                Bitnet
 (_____________________     <aka Eric Korpela>

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

Date: Thu, 4 Apr 91 22:39 GMT
From: AMON <[e-mail]>
Subject: Assorted responses


BETAMAX:
There is a lot of this going around today as well. Software companies are trying
to lock up their interfaces which will have a similar effect. He who publishes his
interface instead of keeping it proprietary will be build the market base
and dominate the market.

HUGHES SUIT:
It is about TIME someone sued the pants of NASA for breech of contract. They
deserve to learn, just like anyone else, that when you sign a contract, you
deliver. One of the reasons I would not deal with the US government (or any other)
is the unreliability. When dealing with REAL business entities, the contract
has "liquidated damages" clauses, "nonperformance penalty" clauses. And
naturally, since there are some circumstances that warrant it, clauses that
allow for contract termination under certain circumstances.

When contracts are grossly out of line with reality and would put a company
out of business, as might have happened with Westinghouse over it's nuclear
fuel fiasco, the results can sometimes be arbitrated. But the customer still
gets some satisfaction.

As far as I'm concerned, NASA signed contracts and was bound to perform or
pay. I agree that NASA should not have been in the business to start with, and
that they should certainly have taken no new contracts after Challenger. But
a professional would have realized that terminating existing contracts means
you give the customer satisfaction for losses you cause him by reneging.

I think it is just fine for them to be taught a good solid whacking EXPENSIVE
lesson about business law.

NUCLEAR ROCKETS:

It's about %#@%%$# time! The only thing I can say is that this is one case
when I wish it had stayed very deep black for a few more years, at least until
they had the thing tested and the production line churning them out.

Letting the anti-nuclear FAScists get started on this before testing is big
trouble. Now we'll be hearing from the Cristic Institute and god knows who
else.

I also fear what will happen if NASA gets its hands on the project. It will be
competing with higher-pressure pumps and advanced solid rocket engines and
other miniscule improvements to the status quo. I really don't think it will
be welcome. Unless there is a strong pressure behind the scenes, NASA will
quitely bury it rather than take the enviro-nut heat; rather than change
streams from their current LO2/LH2 development path; and rather than fight
for another project when they can't even deliver on what they've got.

If anyone has a long enough memory, I was flaming back in the early 80's
that we'd be lucky to see a space station by the year 2000 because of the way
NASA/contractors/congress work. We now have a promise of a 4 man station that
will be fully time manned about 1999, CLOSE TO 20 YEARS AFTER INCEPTION!!!

What a joke.

Give NASA the nuclear rocket and kiss it goodbye, ladies and gentleman.

                        Dale Amon
                        Back on the Network Again...

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

Date: 5 Apr 91 03:41:41 GMT
From: usc!rpi!news-server.csri.toronto.edu!helios.physics.utoronto.ca!aurora.physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: Re: Mt. Venus

In article <[e-mail]> [e-mail] writes:
>
>The show mentioned that Venus had a
>mountain that was 30,000ft tall (1.5 times as tall as Mt. Everest).  Now at
>this hight, both the temperature and pressure would be drastically reduced.  I
>was wondering by how much.  Here are some simple calculations.
>
>Now I know that Denver is roughly at 6,000ft and has 18% less O2 than sea
>level.  Rounding this up to 20% to make the math easier.  Since Venus has
>roughly the same gravitational force as Earth, I'll assume that it loses 20% of
>its atmospheric pressure for every 6,000ft.  Here is a table of height and
>atmosphere pressure.
>
>Height in ft    Pressure
>0        90
>6,000        72
>12,000      58
>18,000      46
>24,000      37
>30,000      30
>
>Since I have no idea how to make the temperature calculations I will assume that
>since the pressure went down to 1/3 it original value, the temperature will do
>the same.  One third of 900F is 300F.
>
   Aaaargh. You can't take "1/3" of any temperature unless it's on an
absolute scale. Consider zero degrees celcius. Twice zero is still zero,
but twice 32 degrees Farenheit is 64 degrees.

   So, putting my hand to these equations, using the adiabatic model for
atmosphes, as recommended in an undergraduate course I once took, I get,
using P0 = 9E+6 Pa, T0 = 800K, g = 8.87 m/s^2, molecular weight = 44,
gamma = 7/5:
P(h=914m) = 85 atm
T(h=914m) = 787K

   Something looks funny about this, but the equation does say that the
atmosphere ought essentially to disappear at 50km altitude, and that
doesn't seem completely unreasonable. Maybe somebody could check my
numbers, just to be on the safe side.


--
 Christopher Neufeld....Just a graduate student  | Flash: morning star seen
 [e-mail]    Ad astra! | in evening! Baffled
 cneufeld@{pnet91,pro-cco}.cts.com               | astronomers: "could mean
 "Don't edit reality for the sake of simplicity" | second coming of Elvis!"

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

End of SPACE Digest V13 #358
*******************