Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v11_1/v11_199.txt

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Subject: SPACE Digest V11 #199

SPACE Digest                                     Volume 11 : Issue 199

Today's Topics:
   Re: "Brilliant Pebbles" vs. "Smart Rocks" (was Re: Railgun ...)
      Re: Discovery's Spin in 2010 (Was Re: Artificial gravity)
                 Solar Cells
     Re: Coilgun on a 747 - supplies to orbit at $20/lb?
   Re: "Brilliant Pebbles" vs. "Smart Rocks" (was Re: Railgun ...)
                Ejection seats
        Re: For All Mankind - Great Movie!!!!!
          Need some Space Station figures...
         Re: Aurora = Strange Flash of Light?
           Comparative Costs to LEO (Cont)
      Re: Discovery's Spin in 2010 (Was Re: Artificial gravity)
       Re: Did SEASAT See More Than It Was Supposed To?
----------------------------------------------------------------------

Date: 29 Mar 90 18:03:51 GMT
From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: "Brilliant Pebbles" vs. "Smart Rocks" (was Re: Railgun ...)

In article <[e-mail]> [e-mail] (Mike Pelletier) writes:
>Whence this silly nomenclature "Brilliant Pebbles"?  Whatever happened
>to the succinct, professional sounding "Smart Rocks"?  ...

The idea was to push the basic concept much farther:  make the rocks much
smaller (hence easier to launch in large numbers) and much smarter (hence
much less dependent on an elaborate tracking and control network).  At
first glance, it sounded plausible.  Of course, as it has moved out of
the "wild idea" stage and into the "funded program" stage, the more radical
aspects of it have been mostly trimmed out, and now it's mildly smarter
and slightly smaller smart rocks.  (The original proposals were talking
about interceptors weighing a fraction of a kilogram and dependent on the
ground only for the "open fire" signal.)
--
Apollo @ 8yrs: one small step.|     Henry Spencer at U of Toronto Zoology
Space station @ 8yrs:        .| uunet!attcan!utzoo!henry [e-mail]

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

Date: 29 Mar 90 18:12:40 GMT
From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Discovery's Spin in 2010 (Was Re: Artificial gravity)

In article <[e-mail]> [e-mail] (Daniel Briggs) writes:
>You're quite right about this effect.  Didn't we see a good example of
>this with one or two of the early Explorer series satellites?  (Energy
>was dissipated by flexing of the four whip antennas.  It was initially
>rotating about its long axis, but eventually started tumbling end over
>end.)  ...

That's right; it was Explorer 1, in fact, and the folks on the ground were
quite surprised by it.
--
Apollo @ 8yrs: one small step.|     Henry Spencer at U of Toronto Zoology
Space station @ 8yrs:        .| uunet!attcan!utzoo!henry [e-mail]

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

Date: Mon, 26 Mar 90 14:29 CST
From: [e-mail]
Subject: Solar Cells

The following information is taken from a paper published in the
Nov 1989 issue of the journal of the IEEE Aerospace and ELectronic Systems.
The paper was written byJ. Avery, V. Sundaram, V. Dinh and T. Davenport

The upshot of the paper is that the team has constructed a solar cell with a
31% energy conversion factor.  The trick is twofold:
1.  Use a cover piece of optics that sits over the GaAs cell and redirects
    incoming light away from the wire grid of the cell i.e. no light is wasted
    bouncing off the cells wiring.
2.  Make the GaAs cell transparent to IR (which it doesn't use anyway) and
    put an IR sensitive GaSb "booster cell" behind in.

Currently satellites use 16% effecient Si based solar cells.
Questions to the floor:

 1. What kind of efficiencies are expected from solar thermal generators.
 2. How 'hardened' are GaAs cells to radiation.
 3. What is the solar energy 'flux' at Earth orbit.
 4. What kind of effeciencies do people use when doing solar power satellite
    studies.

George
[e-mail]

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

Date: Thu, 29 Mar 90 16:11:05 PST
From: [e-mail]
X-Vmsmail-To: UTADNX::UTSPAN::AMES::"[e-mail]"
Subject: Re: Coilgun on a 747 - supplies to orbit at $20/lb?


    Oops!  I made a "slight" error in a previous posting about the
energy required to get something to orbit using a coilgun.  Instead of
3 MJ to get 1 kg to 8 m/s it takes 32 MJ, to 6 km/s it takes 18 MJ
instead of 1.8, and to 4 km/s it takes 8 MJ instead of .8.
    Dan Briggs and Kevin Strietzel suggested converting MJ to kW hr
to get a "down to Earth" idea of the energy involved.  The factor is
.28  kW hr / MJ so for example, at 18 MJ/kg, the energy required to get
400 kg to 6 km/s is the same as the energy used by a 100 watt light bulb
left on continuously for 2 years and 4 months.  Somebody else previously
posted about a 10 ton diesel generator producing 1 MW while consuming
73 gal/hr.  Such a generator would take about 2 hr to produce the required
2 MW hr.   An 800 m gun would have to consume this much energy (plus waste)
in .8 seconds to produce the desired result.

----
Dale M. Greer, whose opinions are not to be confused with those of the
Center for Space Sciences, U.T. at Dallas, UTSPAN::UTADNX::UTDSSA::GREER
      While the Bill of Rights burns, Congress fiddles. -- anonymous

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

Date: 29 Mar 90 22:39:27 GMT
From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Kieran A. Carroll)
Subject: Re: "Brilliant Pebbles" vs. "Smart Rocks" (was Re: Railgun ...)

[e-mail] (Mike Pelletier) writes:

>>The proposed EML in Hawaii wouldn't launch into polar orbits, I
>>believe, but rather into somewhat less highly inclined orbits.  The
>>purpose would be to park large numbers of "Brilliant Pebbles" in
>>orbits that pass over the Soviet Union, where they could be used for
>>boost-phase intercept.
>
>Whence this silly nomenclature "Brilliant Pebbles"?  Whatever happened
>to the succinct, professional sounding "Smart Rocks"?  Sounds like
>some sci-fi writer took out a trade-mark on the latter, so the SDI
>boys had to come up with something new.  Any clues, anyone?

"Smart Rocks" are in the 10-100 kg mass range, while "Brilliant Pebbles"
are intended to be more in the 1-20 kg range. Also, Brilliant Pebbles are
intended to be much "smarter" than smart rocks -- i.e. have more
computational capability aboard. Essentially, this is a means for
killing the enemy by throwing computers at them :-)
--

     Kieran A. Carroll @ U of Toronto Aerospace Institute
     uunet!attcan!utzoo!kcarroll [e-mail]

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

Date: Thu, 29 Mar 90 18:59:21 EST
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Ejection seats


>From: [e-mail]
>Subject: Hermes crew escape system

> From: Lutz Massonne             [phone]     ESC1325  at ESOC
> To:   [e-mail]
> Subject: Shuttle escape

> For the European Hermes spaceplane it was decided (according to newspaper
> reports) to buy the russian ejection seats developed for Buran.
> The ejection seats will enable the crew to eject during the first 90 seconds
> of the flight, placing them 500 m away from Hermes in 2 seconds.
> Ejection will be possible up to 30 km altitude and a velocity of
> 3000 km/h.

That's a pretty abrupt trip! Are US ejection seats comparable? What's the peak
acceleration? (It would have to be 25g minimum, probably greater.)

I presume the crew are ejected head first, in a sitting position. Higher
accelerations have been employed in a rocket sled, but I don't think the
force was applied in this direction.
                         John Roberts
                         [e-mail]

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

Date: 28 Mar 90 17:26:22 GMT
From: jfcl.dec.com!imokay.dec.com![e-mail]  (Doug Borsom)
Subject: Re: For All Mankind - Great Movie!!!!!

A review in the current issue of the New Yorker concurs with the
glowing reports on this movie.  The reviewer had little but praise
for the movie's portrayal of the lunar program.  Sounds like a
must see.

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

Date: 29 Mar 90 19:53:53 GMT
From: zaphod.mps.ohio-state.edu!sunybcs!ubvms![e-mail]
Subject: Need some Space Station figures...

I have a few odd things I'd like to ask and I hope someone can
help me:

I need to know the orbital height and the interior (shirt-sleeve)
volume of each of the following space stations:

                Space Shuttle (cabin)
                Mir
                Freedom
                Salyut (Are any still habitable?)
                Industrial Space Facility

The interior volume of each module used in Mir and Freedom would be
greatly appreciated. Any guesses on the interior volume of our future
Moonbase and Mars base would also be greatly appreciated.

Thanks in advance -

                 Craig Cole
                 University at Buffalo

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

Date: 29 Mar 90 18:24:15 GMT
From: zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Aurora = Strange Flash of Light?

In article <[e-mail]> [e-mail] (John Webb) writes:
>> I've never seen any reference to an aurora producing something equivalent
>> to a "whole-sky flashbulb effect" ...
>(quote)
>ALL-SKY LIGHT FLASHES
>    ... many well-verified observations of sudden flashes of light
>covering the entire sky exist. ...

One should remember that the Earth's magnetosphere is not the stable, rigid
affair often seen in early or excessively-elementary books.  It's in
constant motion, with large currents and flows of plasma all over the place,
and can do some very surprising things.  It's not inconceivable that once
in a while some event in the magnetosphere quite suddenly dumps particles
or current into the upper atmosphere over a wide area.  We are near a solar
maximum, with the solar wind strong and bursty, and the magnetosphere will
be boiling with activity.  I haven't heard of such an auroral phenomenon
being known, but if it is a relatively rare event that happens quite
suddenly, it could well have been missed.
--
Apollo @ 8yrs: one small step.|     Henry Spencer at U of Toronto Zoology
Space station @ 8yrs:        .| uunet!attcan!utzoo!henry [e-mail]

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

Date: 29 Mar 90 20:53:33 GMT
From: elroy.jpl.nasa.gov!zardoz.cpd.com!dhw68k!ofa123![e-mail]  (Wales Larrison)
Subject: Comparative Costs to LEO (Cont)

TITAN-III:  The single vehicle cost of $110 million is based upon a
recent contract for 2 vehicles at $220 million to launch Intelsat
satellites.  The cost includes payload integration and launch
services, but no upper stages.  The Titan III performance to LEO of 33
Klb puts the cargo cost at $3333 per pound. Again, this program
assumes the existence of an open, operating production line, but also
assumes that the fixed cost for maintaining that production line is
not covered by this one unit.

TITAN IV:  The published cost data for a Titan IV launch varies from
$120 million per vehicle at a production rate of 6 per year to $160
million per vehicle at 2 per year.  An extra $5 to $10 million is
required per launch for payload integration and launch services.  No
upper stage costs are included.  Adding the services costs to the
vehicle cost, the cost range becomes $125 million to $170 million per
launch to launch a payload into LEO.  The Titan IV cost data source
includes published information (Air Force budget requests, Aviation
Week, Space Business News, and Aerospace Daily), and also Air Force
provided cost data.  The Titan-IV performance to LEO of 40 Klb puts
the cargo cost at $3125 to $4250 per pound.

SPACE SHUTTLE:  The Shuttle cost numbers used to calculate comparative
cost per pound data were derived by the Congressional Office of
Technology Assessment (Documented in "Launch Options for the Future: A
Buyer's Guide", U.S. Congress, July 1988), and includes the full fixed
and variable costs for Shuttle operations (includes all manned flight
operations, payload integration, launch services, recovery,
refurbishment, turnaround, SRBs, ETs, SSMEs, training, fuel, etc.)
  10 flights per year = $190 million per flight
  12 flights per year = $167 million per flight
  14 flights per year = $152 million per flight
The Shuttle performance is estimated between 55 Klb and 60 Klb to LEO
for vehicles OV-103 and OV-104 (Discovery and Atlantis).  Vehicle OV-
102 (Columbia) is limited to approximately 40 - 45 Klb into LEO.  OV-
105 (Endeavour) will be capable of 63-65 Klb into LEO.  This gives a
fleet average of approximately 55 Klb capability.  Assuming 55 Klb and
the current planned flight rate of 12-14 flights per year with 4
orbiters, the cargo cost to LEO ranges from $3036 to $2764 per pound.
   Note: The 'real' shuttle cost can be accounted for in several
different ways: long-term average cost, short-term average cost,
government transfer price, long-term marginal cost, short-term
marginal cost, annual average cost, annual marginal cost, resource
cost, out-of-pocket cost, etc.  I agree with the Congressional Office
of Technology Assessment to use the "long-term average cost",
calculating the long-term cost of procuring and faciliting the Space
shuttle, including depreciation, amortization, and government capital
costs, using the current projection of 12-14 shuttle flights per year.
For further references, I would recommend "Pricing Options for the Space
Shuttle", Congressional Budget Office, March 1985 (which must be
updated for current baseline budgetary costs, but a good overall
discussion); "Pricing Policies to Compensate for Cost Growth in the
Space Transportion System", General Accounting Office, 1982 (also must
be updated with current budgetary costs); "Understanding the Cost
Basis for Space Shuttle Pricing Policies", by B.A. Stone in Journal of
Parametrics, Vol 3., No.1 (general methodologies); "Launch Options for
the Future: A Buyer's Guide", U.S. Congress Office of Technology
Assessment, July 1988; and "Reducing Launch Operations Costs", U.S.
Congress Office of Technology Assessment, September 1988.




--
Wales Larrison
...!{dhw68k,zardoz,lawnet,conexch}!ofa123!Wales.Larrison                             [e-mail]
714 544-0934 2400/1200/300

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

Date: 29 Mar 90 22:34:17 GMT
From: zaphod.mps.ohio-state.edu!usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Kieran A. Carroll)
Subject: Re: Discovery's Spin in 2010 (Was Re: Artificial gravity)

[e-mail] (Nick Watkins) writes:

>>In contrast to the clever special effects of "2001", in "2010" ...
>>I suppose it must have been pushed through by some scriptwriter who claimed
>>"It's a great special effect, and nobody will notice the inconsistency."
>Worse is the fact that "Discovery" is found tumbling end over end,
>purportedly due to the gyros seizing. The carousel could not have been
>spinning in that plane however, so the angular momentum has somehow been
>transfered through 90 degrees with no external torque. This strikes me
>as a nice trick if you can do it, but I don't think you can, am I wrong?

Sorry, Nick, but Arthur Clarke got this one right :-)

An aspect of the rotational dynamics of satellites that's well-known
to spacecraft dynamicists (and has been since after Discoverer I went
tumbling) is that rotation of a long, thin body (like the Discovery)
about it's long axis is unstable (Newtonian mechanics predicts
it to be neutrally stable; however, internal energy dissipation --
damping -- causes it to be unstable), while rotation about either
of the two short axes (``tumbling'') is stable. Thus, while Discovery
would have >initially< started spinning about its long axis when
the carousel ceased spinning relative to the main spacecraft (gyros
seizing? Perhaps you meant bearings?), this spin would would fairly
quickly have evolved into the end-over-end tumble used in the story.

A good reference for a detailed explanation of all this (which is
surprisingly not too difficult to understand) is:

Hughes, Peter C.
Spacecraft Attitude Dynamics
John Wiley and Sons
Toronto (New York, Chichester, Brisbane, Singapore), 1986

(Prof. Hughes is my PhD thesis supervisor, BTW)
--

     Kieran A. Carroll @ U of Toronto Aerospace Institute
     uunet!attcan!utzoo!kcarroll [e-mail]

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

Date: 29 Mar 90 17:58:29 GMT
From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Did SEASAT See More Than It Was Supposed To?

In article <[e-mail]> [e-mail] (Paul Tomblin) writes:
>#... I don't think DoD has any "prerogative" over civilian research
>#satellites.
>
>I seem to recall that a recent test of an SDI or ASAT weapon (sorry I forget
>deatils, just the uproar) was carried out on a perfectly good 'civilian'
>research satellite because DOD's target didn't reach orbit...

This is a vulgar myth.  The target was a ***DoD*** research satellite with
some instruments that were being used by civilian scientists.  It was DoD
property, theirs to destroy if they felt like it.  Some scientists were
upset about the loss of a satellite that was still returning good data, but
their case was considerably weakened by the fact that nobody had done much
work on analyzing that data for several years -- it was piling up unread.
--
Apollo @ 8yrs: one small step.|     Henry Spencer at U of Toronto Zoology
Space station @ 8yrs:        .| uunet!attcan!utzoo!henry [e-mail]

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

End of SPACE Digest V11 #199
*******************