Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v11_2/v11_201.txt

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Subject: SPACE Digest V11 #201

SPACE Digest                                     Volume 11 : Issue 201

Today's Topics:
     Re: Coilgun on a 747 - supplies to orbit at $20/lb?
      Re: Discovery's Spin in 2010 (Was Re: Artificial gravity)
                Phobos, Deimos
               Comparative Costs to LEO
           Payload Status for 03/29/90 (Forwarded)
          Re: Will we lose another orbiter?
      Re: Discovery's Spin in 2010 (Was Re: Artificial gravity)
      Re: B-52/Pegasus launch scheduled for April 4 (Forwarded)
----------------------------------------------------------------------

Date: Thu, 29 Mar 90 10:10:36 PST
From: [e-mail]
X-Vmsmail-To: UTADNX::UTSPAN::AMES::"[e-mail]"
Subject: Re: Coilgun on a 747 - supplies to orbit at $20/lb?


In SPACE digest V11 #194 mcsun!ukc!stc!root44!hrc63!mrcu![e-mail]
(Paul Johnson) writes:

>Here are some rough calculations.  Say we need 3 miles per second to
>get into orbit (I expect someone somewhere knows better, but stick
>with that for now).  Say 15600 feet per second.
>
>(some equations deleted)
>
>Say about 16000g.
>
>You guys don't want a coil gun, you want a conventional chemical gun.
>
>Paul.

    This is a prime example of what happens when you don't use SI units
and you don't know a few basic space facts.  Velocity for a 300 km orbit is
about 7.7 km/s.  If you must use those other units, their are 1.61 km in a
mile so 7.7 km = 4.8 mi.  A 747 is 75 m long, so the relation v^2=2ad gives
us about 40000 g for the acceleration to orbital velocity, consuming
about 3 MJ of energy per kg of projectile.
    But in the Scientific American article on the proposed Hawaiian
gun, their stated intent is to acheive a 6 km/s muzzle velocity just to get
the projectile above significant atmosphere and then use a rocket motor to
boost to orbital velocity.  The payload would be 100 kg and the motor +
fuel would be 300 kg.  Since their gun is 800 m long, the minimum
acceleration would be about 2300 g, requiring about 1.8 MJ/kg.
    They didn't say how much speed the projectile would lose on its way
through the atmosphere.  Suppose you only need 4 km/s if you launch from a
747 at.  In that case, the acceleration need only ;-) be about 11000 g, using
about 0.8 MJ/kg.  How much is a megajoule, anyway, in "real life" terms?

----
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 06:01:37 GMT
From: unmvax!nmtsun![e-mail]  (NRAO Array Operations Center)
Subject: Re: Discovery's Spin in 2010 (Was Re: Artificial gravity)

In article <[e-mail]> [e-mail] (Christopher Neufeld) writes:
>   Yes and no. You can't do what you said, but you don't have to do that
>to achieve the effect seen in the movie.
>   Let's assume that the angular momentum vector of the Discovery is
>aligned along the long axis of the ship during its normal operation. Say
>that the Discovery is pointed directly at, say, the moon. Now, let the
>bearings on the carousel seize up. The ship will start to spin about its
>long axis. There is a lower energy mode of this angular momentum value,
>though, which is a spinning around the pitch or yaw axes. The fact that
>the ship is not a perfectly rigid body, along with possible
>gravitational influences from nearby Jupiter and its moons, will cause
>the ship to settle into this lower energy mode, even without an external
>net torque. The difference is that the ship itself will have rotated
>through ninety degrees in shifting from the one mode to the other. Now,
>the ship is not pointing at the moon, but is rotating around an axis
>which points at the moon.
>   The angular momentum of this final system is the same, while the
>energy is lower.

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.)  I must admit, I've never been completely clear on what happens
to one of these systems when the object is rotating about axis with
maximal moment of inertia.  There's nothing to prevent it from
radiating still more energy, (or is there?)  How do we conserve
momentum?  There was a nice demo of this effect by one of the
astronauts on Skylab, too.  He used a half-filled Tang (?) container.
The bottle was cylindrical, and energy was dissipated in the sloshing
liquid.  It took about 30 seconds to go from rotation about the
minimal principal axis to rotation about a (degenerate) maximal axis.

About 2010, though.  If my none-too-perfect memory serves, wasn't the
carousel spinning about the yaw axis?  (I.e. about a vertical axis,
given the usual cinematic conventions.)  To first order, the Discovery
probably has equal moments about the pitch and yaw axes.  When the
bearings seize, the entire ship should rotate about the yaw axis to
conserve angular momentum.  (Surely that _must_ be the solution for an
idealized cylinder, no?)  Wasn't it shown rotating about the pitch
axis?  The explanation that you posit wasn't what they had in mind,
even allowing a higher MoI in pitch than in yaw, because when they
restarted the carousel, the ship stopped spinning.  Had energy
dissipation been part of the mechanism, it wouldn't have returned to
the original state.  I think that some cinematic liberties were indeed
taken with the laws of physics.

On a related note, the producers weren't above making the earth spin
backwards for the same reasons.  The sunrise over the VLA that you see
in the beginning of the movie is actually a sunset filmed in reverse.
(Or do I have that backwards?  Haven't seen the movie in a long time.)

-----
This is a shared guest account, please send replies to
[e-mail] (Internet)
Dan Briggs / NRAO / P.O. Box O / Socorro, NM / 87801  (U.S. Snail)

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

Date: Thu, 29 Mar 90 21:00:36 EST
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Phobos, Deimos


>Date: 28 Mar 90 15:08:46 GMT
>From: aramis.rutgers.edu!athos.rutgers.edu![e-mail]  (Steve Masticola)
>Subject: Re: Martian Stardard Time

>Just out of curiosity, how large and bright would Deimos and Phobos
>appear from the Martian surface? Would they have features observable
>to the naked eye? Cast shadows?

>- Steve ([e-mail])

The angular size of Phobos as seen from the surface should be about .153
degrees - ~1/3.3 of the size of our full moon, so you should be able to
see some detail. Deimos would be ~.023 degrees across, or ~1/44 of the
size of the moon. You should be able to see that it isn't a star.
                     John Roberts
                     [e-mail]

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

Date: 29 Mar 90 20:52:02 GMT
From: zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!zardoz.cpd.com!dhw68k!ofa123![e-mail]  (Wales Larrison)
Subject: Comparative Costs to LEO

To all interested, here is a set of comparative cost/lb into Earth
Orbit.  Please, let's argue from a realistic set of data - I've listed
sources and assumptions to show you this is the real world. EDITORIAL
COMMENT:  I'm tired of seeing people buy the propaganda that the Space
Shuttle "is by far the most expensive means of space transportation".
It isn't.

SUMMARY: Delta II:        $3603 - 3874  per pound into LEO
         Atlas Centaur:   $3740 - 4471  per pound into LEO
         Titan III:           $3333     per pound into LEO
         Titan IV:        $3125 - 4250  per pound into LEO
         Shuttle:         $3036 - 2764  per pound into LEO

COST ASSUMPTIONS: All cargo cost estimates are based upon a single
user with a payload delivered to 150 nautical miles and an orbital
inclination of 28.5 degrees (due East from KSC).  This user is assumed
to be a commercial customer, looking for a single, simple,
standardized launch.  No block buys of vehicles were assumed, nor any
new developments.  No upper stage costs are included.  Payload
integration and the minimum necessary launch services costs have been
included in each cost estimate.  Wherever possible, costs have been
based upon actual quotes from commercial offerings.  Costs for the
Shuttle were not based upon NASA numbers, and are based upon actual
shuttle costs, not the price charged to commercial users (which may be
lower).  While every attempt has been made to keep the assumptions and
comparison constant across the different launch vehicle, any of the
cost numbers can be varied +/- 10% due to slight differences in
accounting (ie, year of dollars, minor additional services, etc.)

DELTA II:  The Delta II costs are based upon various published sources
for the price of a commercial Delta 7925 (Delta II) launch.  Sources
used include: McDonnell/Douglas company literature, Aviation Week,
Defense Daily, DoD Budget requests, and Flight International).  The
single vehicle contract cost of between $40 and 43 million is a
commercial contract cost which includes system and launch integration
services, without an upper stage cost.  Although the launch is for a
single payload, it was assumed the launch vehicle order would follow
the current Delta pricing policy that piggybacks additional
production units onto the Air Force Delta II orders which allow for a
continuous production line.  The Delta II performance into LEO is 11.1
klb.  Based upon the vehicle contract price range, the cargo cost to
LEO is between $3603 and 3874 per pound.

ATLAS-CENTAUR:  Based upon published Atlas G + Centaur Data, the
single vehicle commercial contract cost, including launch and
integration sercies, but no upper stage, ranges from $46 to 55 million
per launch.  Sources of data used here include: General Dynamics
company literature, Aviation Week, Aerospace Daily, Space
International, and Space Business News.  As with the Delta II, the
launch vehicle is assumed to be a single, additional order that is
part of an existing production run.  (Current contract data indicates
that if the vehicle were a part of a government block buy, the cost
could be reduced to $450 million for an 11 vehicle production run with
no contractual oversight and no performance penalties.)  Using the LEO
performance of 12.3 Klb, the price range yields a cost to LEO of $3740
to  4471 per pound into LEO.
                                 (continued )



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

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

Date: 29 Mar 90 17:48:41 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: Payload Status for 03/29/90 (Forwarded)


    Daily Status/KSC Payload Management and Operations 03-29-90.


    - STS-31R HST (at Pad-B) -

    Preps for HST transfer into the payload bay were completed
    yesterday.  The actual transfer will occur today.


    - STS-35 ASTRO-1 (at OPF) -

    End to end testing was completed second shift yesterday.
    RAAB removal and replacement was completed on third shift
    today.  RAAB retest is active and will continue through
    first shift today followed by igloo cover installation on
    second shift.


    STS-40 SLS-1 (at O&C) -

    Preps for rack and floor installation into the module were
    worked yesterday and will continue today.


    - STS-42 IML-1 (at O&C) -

    Racks 3, 4 and 7 staging operations were worked yesterday.
    Racks 3, 4 and 11 staging activities along with module clamp
    inspections are scheduled for today.


    - STS-45 (Atlas-1)-

    Pallet joint kit installation on frame 4 will be worked
    today.

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

Date: 29 Mar 90 16:10:00 GMT
From: network.ucsd.edu!hp-sdd!apollo![e-mail]  (Steve Rehrauer)
Subject: Re: Will we lose another orbiter?

[ I read sci.space infrequently, so forgive me if this is old hat. ]

We've lost one shuttle, and I'm sure it's likely that we'll eventually
lose another.  My question is, after N years of operating these beasts,
have we (meaning NASA, I guess) learned how to build a better shuttle?
Has Challenger's replacement "evolved" in any way?  More importantly,
how much has the shuttle program taught us about building the true next
generation of orbiter, be it NASP or whatever?  (I.e.: a manned system
that delivers some combination of lower payload-delivery cost, greater
reliability, less-stringent maintenance, etc than do the shuttles.)
--
>>"Aaiiyeeee!  Death from above!"<< | Steve Rehrauer, [e-mail]
   "Flee, lest we be trod upon!"    | The Apollo System Division of H.P.

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

Date: 30 Mar 90 00:49:11 GMT
From: unmvax!nmtsun![e-mail]  (Daniel Briggs)
Subject: Re: Discovery's Spin in 2010 (Was Re: Artificial gravity)

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Daniel Briggs) writes:
                                  ^^^^^^^^^^^^^^^^
                     Hey, you got the attribution right!  Most people don't.

>>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.

Actually, I thought that Explorer 1 was merely the one that was hit the worst
by this problem.  As I remember reading, later Explorers had rigid antennae.
This helped a whole lot, but eventually a number of them tumbled for exactly
the same reason.  The antennae weren't *completely* rigid.  No one was too
concerned about the later ones, since I believe that this was after the
operational lifetimes of the satellites in question.

-----
This is a shared guest account, please send replies to
[e-mail] (Internet)
Dan Briggs / NRAO / P.O. Box O / Socorro, NM / 87801  (U.S. Snail)

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

Date: 29 Mar 90 20:12:03 GMT
From: argosy![e-mail]  (Kevin S. Van Horn)
Subject: Re: B-52/Pegasus launch scheduled for April 4 (Forwarded)

In article <[e-mail]> [e-mail] (Peter E. Yee)
writes:
>
>     The Pegasus program is sponsored by the Department of
>Defense Advanced Research Projects Agency.  Pegasus was developed
>by Orbital Sciences Corp., Fairfax, Va., and Hercules Aerospace
>Co., Wilmington, Del.

Sponsored in what way?  It was my understanding that OSC and Hercules paid
for the entire development out of their own funds.  Or do you consider
purchasing launches to be a form of sponsorship?

------------------------------------------------------------------------------
Kevin S. Van Horn            | The means determine the ends.
[e-mail]      |

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

End of SPACE Digest V11 #201
*******************