Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_1/V11_155.TXT

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Subject: SPACE Digest V11 #155

SPACE Digest                                     Volume 11 : Issue 155

Today's Topics:
    Re: What happened to the satellites retrieved by the Shuttle?
              Re: Sandia Railgun
    Re: What happened to the satellites retrieved by the Shuttle?
                  Re: Power
       Re: Shuttle escape systems, was Challenger's Last Words
       Coilgun on a 747 - supplies to orbit at $20/lb?
       Re: Shuttle escape systems, was Challenger's Last Words
           Re: Artificial Gravity rephrased
----------------------------------------------------------------------

Date: 16 Mar 90 01:33:46 GMT
From: elroy.jpl.nasa.gov!jato!mars![e-mail]  (Ron Baalke)
Subject: Re: What happened to the satellites retrieved by the Shuttle?

In article <[e-mail]> [e-mail] (Greg Shippen) writes:
>Whatever happened to the satellites that at least one pre-Challenger
>shuttle mission retrieved from orbit?  As I recall at least two were
>retrieved.  At the time, this was touted as an opportunity to reuse
>these satellites.  Did this really happen?  Were they returned in
>working order
>or did they end up being damaged during launch and/or retrieval?
>
They ended up in storage at Hughes Aircraft in El Segundo, California.
The satellites were written off as a total loss, the insurance company
paid off the policy and took over ownership of the satellites, and have
tried to sell them, but there were no buyers.
 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

Date: 16 Mar 90 05:25:09 GMT
From: snorkelwacker!usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Sandia Railgun

In article <[e-mail]> [e-mail] (Paul Dietz) writes:
>This is NOT a railgun!  Railgun is not a generic term for electromagnetic
>launcher.  This misconception is surprisingly common.
> ...
>The Sandia system is a coilgun, aka mass driver...

This is NOT a mass driver!  Mass driver is not a generic term for coilgun.
This misconception is surprisingly common.

:-), but I'm serious too.  A mass driver is a coilgun, or some variant
thereon, with *recirculating buckets*:  once the payload carrier (aka
bucket) is up to full velocity, it releases the payload and is then
decelerated to be re-used.  This reduces the hardware expended to
zero, which is just what you want for long-term bulk mass launching,
e.g. for building space colonies.

Coilguns have been around for a long time.  The mass driver was invented
by Gerard K. O'Neill in 1974; despite the "obvious" desirability of
recirculating the buckets, nobody seems to have thought of it earlier.
--
MSDOS, abbrev:  Maybe SomeDay |     Henry Spencer at U of Toronto Zoology
an Operating System.          | uunet!attcan!utzoo!henry [e-mail]

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

Date: 16 Mar 90 05:40:54 GMT
From: snorkelwacker!usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: What happened to the satellites retrieved by the Shuttle?

In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>>Whatever happened to the satellites that at least one pre-Challenger
>>shuttle mission retrieved from orbit? ...
>
>They ended up in storage at Hughes Aircraft in El Segundo, California.
>The satellites were written off as a total loss, the insurance company
>paid off the policy and took over ownership of the satellites, and have
>tried to sell them, but there were no buyers.

I think your info is out of date, Ron.  Both have been sold and are slated
to go up again (on expendables) in the next year or two.  One of them is
Asiasat 1 now, slated to go up on Long March, and I think the other is
Panamsat 1, whose scheduled launcher I forget.
--
MSDOS, abbrev:  Maybe SomeDay |     Henry Spencer at U of Toronto Zoology
an Operating System.          | uunet!attcan!utzoo!henry [e-mail]

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

Date: 16 Mar 90 05:38:30 GMT
From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Power

In article <[e-mail]> [e-mail] (Wayne Fellows) writes:
>Has anyone considered using a solar heated boiler system for powering a space s
>tation/vessel?  Would the cost be lower to design, build, and put into orbit th
>an a nuclear or SV system?  ...

The fancy name for this is "solar dynamic" power ("dynamic" because of the
turbogenerator system needed), and such systems were dropped from the
space station at least twice (!) because of higher development costs and
some degree of technical risk (nobody's ever done a major solar dynamic
system for spacecraft).  In many ways this is a very nice system:  mirrors
are lighter than solar arrays, they don't degrade with radiation, the
power conversion is more efficient, and one can store heat well enough
to eliminate the need for (heavy, limited-life) batteries to provide
power during eclipses.  That last is not a trivial issue; the station
will need a dedicated shuttle flight every five years or so just for
battery replacement.

NASA is now harvesting the fruits of its decision, about two decades ago,
to kill most of its space-technology development work to save money.
Almost everything has to be done with twenty-year-old concepts, because
there are no tested, off-the-shelf replacements that one can include in
a big, high-profile project without fear of failure or cost overrun.
--
MSDOS, abbrev:  Maybe SomeDay |     Henry Spencer at U of Toronto Zoology
an Operating System.          | uunet!attcan!utzoo!henry [e-mail]

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

Date: 16 Mar 90 05:31:14 GMT
From: snorkelwacker!usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Shuttle escape systems, was Challenger's Last Words

In article <[e-mail]> [e-mail] (S Schaper) writes:
>.... Might it not be, that with sufficient sensors to moniter this sort of
>accident, the shuttle could be programmed to sep from the stack, with escape
>rockets of some sort and do an RTLS? ...
> Or are the dynamic pressures on the shuttle during the SRB ascent phase too
>high for an RTLS to work?

They are perhaps not high enough to make it impossible, but they *are*
high enough to make it very difficult.  Separating two spacecraft at
high speed within the atmosphere is a very tricky problem.  Military
aircraft engineers get gray hairs solving such problems for missiles
fired from aircraft... at much lower speeds, with no malfunctions
involved, and with aircraft and missiles that are fairly durable and
can be kicked apart fairly hard.  Add in the problem of keeping the
fragile orbiter clear of the hot, violent, abrasive SRB exhausts
afterward, and the difficulty of designing attachments that can
separate cleanly when one part is accelerating much harder than the
other (the orbiter is hanging on the struts throughout SRB burn,
not even supporting its own weight), and it looks pretty daunting.

The right fix is to switch to liquid boosters and eliminate the problem.
--
MSDOS, abbrev:  Maybe SomeDay |     Henry Spencer at U of Toronto Zoology
an Operating System.          | uunet!attcan!utzoo!henry [e-mail]

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

Date: 16 Mar 90 06:42:43 GMT
From: sam.cs.cmu.edu![e-mail]  (Vincent Cate)
Subject: Coilgun on a 747 - supplies to orbit at $20/lb?

Donald Lindsay
>Current prototypes hurl 10 pound projectiles half a mile at the speed
>of an artillery shell. Sandia has applied for funding for a 10-stage
>launcher to accelerate an 850 pound projectile beyond the atmosphere,
>at which point a rocket engine would fire to push it into orbit.
>...
> For a full-size launcher
>a heat shield will be needed because of the intense heat generated
>when the vehicle is accelerated to a speed of 2.8 miles per second.

Paul Dietz:
>The proposed Sandia gun's low muzzle
>velocity (about 1/2 orbital velocity) helps here, although I think
>going to > orbital velocity should be possible if the aluminum is
>precooled with LN2, is cooled by transpiration, and/or is replaced
>with beryllium.

Sounds like a coilgun on a high flying 747 should be a cheap way to
get lots of supplies into orbit!!!!  Food, rocket fuel, and probably
kevlar inflatable living quarters could be sent to near orbit
this way.  At high altitudes it will be possible to give projectiles
some of the orbital velocity, along with the altitude, for orbit.

Air resistance working the way it does, it seems that to fire a projectile
to near orbit (sideways around Earth) we would need so start above most
of the atmosphere.



Back of the envelope type guess for price/lb to orbit:

Current cost to orbit      $750/lb          (all number approximate)
Cost of airplane flight      $1/lb
Cargo capacity of 747   100,000 lbs

How much would coilgun, capacitors, powersupply, generator and gas
weigh?  What would the cost of the fuel/rocket-engines/control for each
projectile run?  What fraction of the weight would it take?  How small
would the projectiles have to be so that the force did not hurt the 747?
Is a 747 long enough for such a coilgun? (I seem to recall that some
designs for moon based massdrivers that were more than a km long).

I don't know, :-), but to continue on let me make some guesses.
Assume that coilgun and support takes up 50,000 lbs and that 2/5ths of
the weight of a projectile ends up being overhead.  Starting with
100,000 lbs on the plane, we would still end up sending 30,000 lbs
to orbit.  The amount of rocket fuel might be less than 1/100th that of
the space shuttle per pound of real payload.  We could fly this thing
every day if we could make projectiles fast enough.

It seems like this would be really cheap, maybe $10 to $30/lb in quantity?


What are the hard parts of this type of approach?

Anyone willing to venture more accurate estimates of cost etc?

   -- Vince

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

Date: 16 Mar 90 05:02:48 GMT
From: psuvm![e-mail]
Subject: Re: Shuttle escape systems, was Challenger's Last Words

In article <[e-mail]>, [e-mail] (S Schaper) says:
Stuff about a shuttle escape system erased
> Or are the dynamic pressures on the shuttle during the SRB ascent phase too
>high for an RTLS to work?
>
I think that the aerodynamic forces acting on the vehicle during launch
would tear it apart if it tried to break away from the tank and SRBs.
I don't rmemebr where I heard this, but apparently the shuttle is very
sensitive to angle of attack.

Mike Williams
[e-mail]

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

Date: 16 Mar 90 05:11:21 GMT
From: psuvm![e-mail]
Subject: Re: Artificial Gravity rephrased






In article <[e-mail]>, [e-mail] (Robert Casey)
says:
>
>If I was in that spaceship that was in _2001_, in the spinning section, seems
>that I could throw a baseball in such a way as to cancel the spin speed.  Then
>the baseball would seem to take a circular path thru the spinning section at
>the height from the floor where I threw it.  Then I better duck at one
>rotation! :-)  Seen from outside the spinning section of the ship, the
>baseball would be staying put in one spot.  So, the artifical gravity wouldn't
>grab the ball.  Make sense?
Yep, but if this were to occur, I think that friction with the air would
take care of the ball in a few 'orbits' of the vehicle.

Mike Williams
[e-mail]

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

End of SPACE Digest V11 #155
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