Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V12_6/V12_705.TXT

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Subject: SPACE Digest V12 #705

SPACE Digest                                     Volume 12 : Issue 705

Today's Topics:
              Re: Tenth planet?
           Re: space news from Nov 5 AW&ST
              Galileo Observed!
           Re: space news from Nov 5 AW&ST
        Re: MAJOR SOLAR FLARE ALERT & UPDATED WARNINGS
Re: Who killed Nuclear Rockets? (was Re: The Next Ten Years In Space)
            Re: pressure-altitude relation
             Pioneer 6 Update - 12/17/90
             STS Flight Manifest
          Re: Recent DoD Space System Cost Data ...

Administrivia:

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Date: 17 Dec 90 03:13:10 GMT
From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Organization: U of Toronto Zoology
Subject: Re: Tenth planet?
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In article <[e-mail]> [e-mail] (Richard Schroeppel) writes:
>hs>...(A very careful reassessment of observations
>hs>of the orbit of Neptune by some folks at JPL concluded that there are no
>hs>unexplained perturbations.) ...
>From the 1988 Astronomical Almanac...

The JPL work I refer to was quite recent, as I recall, enough so that it
might not be reflected in a three-year-old book.

>(1) Can we determine the spacecraft position, relative to the transmitting
>    antenna, to within a wavelength of radio?  How accurately can the
>    velocity and acceleration be measured?

The biggest uncertainty in the positions of the Voyagers is that
arising from the uncertainty in the Earth positions of the tracking
stations.  We are talking about *very* precise measurement work here,
vastly more precise than anything that can be done without a cooperative
target on the other end.  One reason why JPL is into things like ephemerides
is that the spacecraft positions are often known far more precisely than the
positions of the target planets.

>(2) The spacecraft maneuvers occasionally.  The delta-V caused by the
>    maneuver must be taken into account, and cannot be measured
>    independently.

The models of the thruster performance have been calibrated to great
precision after over a decade in flight, and such short-term changes
*can* be measured largely independently of the very slow and gradual
changes that would occur as the result of planetary gravitation.

>(3) Are there non-gravitational forces on the spacecraft?  Light pressure,
>    outgassing, thruster leaks, and occasional ring particle impacts.

Certainly there are non-gravitational forces on the spacecraft, all of
which are known with very high precision by now.  Precise trajectory
modelling considers all these issues and many more.
--
"The average pointer, statistically,    |Henry Spencer at U of Toronto Zoology
points somewhere in X." -Hugh Redelmeier| [e-mail]   utzoo!henry

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Date: 17 Dec 90 02:27:48 GMT
From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Organization: U of Toronto Zoology
Subject: Re: space news from Nov 5 AW&ST
References: <FGF^?1|@rpi.edu>, <[e-mail]>, <[e-mail]>
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In article <[e-mail]> [e-mail] (Fraering Philip) writes:
>>They did it for 1/50th (2%) of what it cost to develop the first Shuttle.
>>Unlike the major Shuttle contractors, they have carried a loss on the
>>project (in other words risked their own money) ...
>
>Didn't they start out with a guaranteed sale from DAPRA before the
>thing was actually built?

They had DARPA as a "launch customer", yes.  That was not a subsidy
any more than Pan Am as a launch customer for the 747 was a subsidy
for Boeing.  DARPA paid for results -- a launch -- not for promises.
(Actually, DARPA bought several launches, but even so, it's not going to
pay back the development costs, any more than the Pan Am order alone
paid the costs for the 747.)  OSC and Hercules spent their own money
on Pegasus; had it failed, they would have been paid nothing.

>And they also had use of the B-52 from DAPRA, didn't they?

At the moment, since OSC+H don't own a launch aircraft, the customer
has to supply one.  I believe the price was discounted appropriately.

I should qualify this by saying that Pegasus *did* have help, from NASA
in particular, in various modest ways.  But if the first launch had
failed, it would have been the stockholders, not the government, out
of pocket on the project.  That's the ultimate test of who's paying.
--
"The average pointer, statistically,    |Henry Spencer at U of Toronto Zoology
points somewhere in X." -Hugh Redelmeier| [e-mail]   utzoo!henry

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Date: 16 Dec 90 19:04:36 GMT
From: cs.utexas.edu!execu!sequoia![e-mail]  (Mike McCants)
Organization: Execucom Systems Corp
Subject: Galileo Observed!
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Using a 32 inch telescope with a CCD camera attached, Paul Maley
obtained images of the Galileo spacecraft as it approached the
Earth the evening before Earth encounter on December 8, 1990.

Galileo was first observed at 2:15UT, December 8, at a range of
376,000 miles.  Galileo was observed for 1 and 1/2 hours.  Paul
estimates that the magnitude of Galileo was about 16.5 to 17.

The observations were made under clear, moonless skies from a site
about 80 miles southwest of Houston.  Galileo was about 40 degrees
up in the southeast.

The Granat rocket canister, NORAD number 20354, was also observed
at apogee at a range of 119,000 miles.

Mike McCants
[e-mail]

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Date: 16 Dec 90 04:10:42 GMT
From: sumax!ole!thebes!polari![e-mail]  (Charles Radley)
Organization: Seattle Online Public Unix [phone]
Subject: Re: space news from Nov 5 AW&ST
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+but now it is out in the open.  The long truss is probably not long
+for this world, in particular:  a Goddard project to attach science
+payloads to it has been cancelled, and the request for bids for the
+assembly training facility in Houston has been withdrawn.  The
+leading idea right now is simply to retain the central cluster of
+modules, but kill the truss.  Among other advantages, the resulting
+station should have gravity-gradient stability, eliminating
+attitude-control thruster firings that eat fuel and bother the
+microgravity people.
-
This is nonsense. The current Freedom is already gravity gradient
stabilized, and The Truss is the very feature which makes gravity
gradient stabilization possible, since it gives the solar arrays
sufficient degrees of freedom to continuously track the Sun
independent of the attitude of the main part of the station, which is
pointing at the earth.
  Deleting the truss means the station will no longer be gravity
gradient stabilized because the solar arrays will have only one
degree of freedom.   This means that the entire station will have to
be kept more or less sun pointing, and gravity gradient pointing will
no longer be possible.
  Instead of reducing thruster firings and fuel consumption, deleting
the truss will substantially increase both.

:wq

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Date: 14 Dec 90 03:17:14 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: MAJOR SOLAR FLARE ALERT & UPDATED WARNINGS

In article <[e-mail]> [e-mail] (Cary Oler) writes:
>MAJOR ENERGETIC EVENT SUMMARY
>
>     An explosive surge of solar activity occurred today.  There were a total
>of eight M-class flares today.  Two of these were major energetic events.  The
>largest event was the class M8.9/SF flare which occurred at 14:10 UT on 12
>December ...

It occurs to me that it must be awfully fun to watch the Sun's weather
all day as one's job, and to issue NWS-style weather reports on it.
After a while you must feel like you *live* on the Sun!  I think I
picked the wrong career.  Wonder how it feels to grok M-class fares for
hours on end, then go rolling your shopping cart down the aisles at the
Pic 'N Pay while you pick up some calf's liver for dinner.

>     The auroral storm which was anticipated for high latitudes never reached
>the intensities anticipated.  Significant periods of auroral activity has
>occurred over the high latitudes, but the activity has been relatively
>localized.  The auroral storm warning has been cancelled for all regions.
>Localized periods of high auroral activity may still be possible, but such
>activity will be isolated.

So, no school cancellations then, right?  :-)


--
"I'm not sure I've even got the brains to   #:#   Tom Neff
 be President." -- Barry Goldwater, 1964    #:#   [e-mail]

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Date: 17 Dec 90 06:44:27 GMT
From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Who killed Nuclear Rockets? (was Re: The Next Ten Years In Space)

In article <[e-mail]> [e-mail] (Fraering Philip) writes:
>>Dumbo.  See Kingsbury's "Notes on Nuclear Rockets"...
>
>Where can I find this? Is it an article? A book?

An unpublished manuscript, I'm afraid, as of the copy I have.  It was
available from Kingsbury for a nominal cost, and possibly still is, but
I have no idea of his current address.  The full title is "Technical
Notes on Nuclear Rockets", by Bruce W. Knight and Donald Kingsbury,
and his address *then* was Donald Kingsbury, Math Dept., McGill University,
PO Box 6070, Station A, Montreal, Quebec M3C 3G1  Canada.
--
"The average pointer, statistically,    |Henry Spencer at U of Toronto Zoology
points somewhere in X." -Hugh Redelmeier| [e-mail]   utzoo!henry

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Date: 17 Dec 90 17:54:44 GMT
From: sdd.hp.com!news.cs.indiana.edu!news.nd.edu!mentor.cc.purdue.edu!mace.cc.purdue.edu![e-mail]  (Perry G Ramsey)
Subject: Re: pressure-altitude relation

In article <[e-mail]>, [e-mail] (David Kinkley) writes:
> / hpindwa:sci.space / [e-mail] (David Kinkley) /  3:10 pm  Dec 16, 1990 /
> / hpindwa:sci.space / [e-mail] (Matthew T Velazquez) / 10:10 pm  Dec 15, 1990 /
>
>
> >>>>>Depends on the atmospheric model you use. For the troposphere (valid
> >>>>>up to circa 20 km):
>
> >>>>>P(sea level)/P(z) = [1-L/T(sea level)]^^gamma/(1-gamma)

I disagree on the exponent.  If you are assuming a dry adiabatic lapse
rate, gamma/(1-gamma) = -3.5 is right.  If you are assuming something else,
like the given equation does, then you should use

-g/(R L)

Where g is the acceleration due to gravity   (9.8 m/s^2)
      R is the gas constant for air          (287 J/kg K)
      L is the assumed lapse rate            (6.5 K/km = .0065 K/m is good).

This gives an exponent of -5.25 instead of -3.5.
Also, if you just drop the negative signs on the exponents, the
the left hand side of the equation becomes p(z)/psl which is easier all around.

> Plugging in numbers into the troposphere model I get a 0.48 bar pressure for
> Mt Everest (29000 feet) assuming 300K at sea level.  Is this right I thought
> it might be a bit less???

Assuming T sea level = 30 C = 303 K, then for the original formula

p(z)/psl = (1- 8839*.0065/303)^3.5 = 0.48

which is what you got, I suppose.

Using the revised formula

p(z)/psl = (1- 8839*.0065/303)^5.25 = 0.33

An important difference.

According to my handy standard atmosphere chart, at 8800 m, p=3.17 e4 N/m^2,
or about .312 times sea level standard pressure.

It's important to remember that these are just estimates.  Your mileage
may vary.  There are a lot of assumptions that go into a standard atmosphere;
not all of them are so good.

Not that this has anything at all to do with space.

--
Perry G. Ramsey           Department of Earth and Atmospheric Sciences
[e-mail]   Purdue University, W. Lafayette, IN USA
[e-mail]
 Why waste time learning when ignorance is instantaneous?  -- Hobbes

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Date: 17 Dec 90 16:59:09 GMT
From: swrinde!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Organization: Jet Propulsion Laboratory, Pasadena, CA.
Subject: Pioneer 6 Update - 12/17/90
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                            PIONEER 6 STATUS REPORT
                              December 17, 1990

     Yesterday, December 16, 1990, marked the 25th anniversary of the
launch of the Pioneer 6 spacecraft.  A tracking pass was performed by the
70 meter antenna at Goldstone, California, the first of two scheduled
supports.  The Goldstone antenna provided telemetry and tracking data, and
radiated 4 commands.  The average AGC (Automatic Gain Control) is at -170.0,
the SNR is 3.0 and the telemetry data rate is at 16 bits/second.  There
were no problems encountered during the tracking pass.  Pioneer 6 was last
supported on July 4, 1990, by the 70 meter antenna in Spain.  Goldstone will
provide another tracking pass today starting at 9 AM (PST).
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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Date:        Mon, 17 Dec 90 08:42:03 CST
From: Andy Edeburn <[e-mail]>
To: <[e-mail]>
Subject: STS Flight Manifest


 I am in dire need of a flight manifest listing for the next three
years of shuttle launches. Something along the lines of flight
identification designation, payload, proposed length, dates, etc.

 If anyone has anything along this line, I would greatly appreciate
it if you could e-mail direct to me. Thanks!

+--------------------------------------------------------------------+
| Andy Edeburn  {CC62@SDSUMUS}       | "It is always better to trust |
| Computing Center & Data Processing |   your dog, rather than your  |
| South Dakota State University      |     neighbors." - Walton      |
+--------------------------------------------------------------------+

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Date: Mon, 17 Dec 90 11:58:06 -0500
From: "Allen W. Sherzer" <[e-mail]>
To: [e-mail]
Subject: Re: Recent DoD Space System Cost Data ...
Newsgroups: sci.space
In-Reply-To: <[e-mail]>
Organization: Evil Geniuses for a Better Tomorrow
Cc:

In article <[e-mail]>:

>   Note: the revised current average cost per unit of the Titan IV
>is about $208.6 Million with 75 vehicles to be produced, and at
>about 40,000 lbs into 100 nmi 28.5 deg orbits, this is still about
>$5215/lb.

For completeness, the Commercial Titan (Titan III) will place 32,000 lbs
into a 100nmi 28.5 deg orbit (40,000 with new solids). The unit cost of
a commercial Titan is $125 million [1] which gives a cost of $3906/lb
according to the 8 January issue of Avation Week (page 42). Moral: if
you want a quick 25% reduction in launch costs then buy commercial.

[1] This $125M is the 'sticker price'. Actual costs will be lower.

  Allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | If guns are outlawed, how will we shoot the liberals?  |
|   [e-mail]    |                                                        |
+---------------------------------------------------------------------------+

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End of SPACE Digest V12 #705
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