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Subject: SPACE Digest V10 #416

SPACE Digest                                     Volume 10 : Issue 416

Today's Topics:
       Re: NASA Headline News for 01/09/90 (Forwarded)
        Electromagnetic Braking (Theory & #s)
                  Gyroscopes
               On-Board Imaging Systems
            Re: Nuclear Reactors in Space
            Re: Nuclear Reactors in Space
               KSC tours (long)
----------------------------------------------------------------------

Date: 11 Jan 90 09:11:03 GMT
From: agate!shelby!portia!hanauma![e-mail]  (Joe Dellinger)
Subject: Re: NASA Headline News for 01/09/90 (Forwarded)

In article <[e-mail]> [e-mail] (benjamin.reytblat) writes:
>> In article <[e-mail]> NASA sez:
>> Here's what I don't get about this regular "NASA News" release.  Why in
>> hell do we need to pay NASA to tell us what the New York Times said that
>> morning?

What do you bet the NYT just copies NASA's official text...?
\    /\    /\    /\/\/\/\/\/\/\.-.-.-.-.......___________
 \  /  \  /  \  /Dept of Geophysics, Stanford University \/\/\.-.-....___
  \/    \/    \/Joe Dellinger [e-mail]  apple!hanauma!joe\/\.-._

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

Date: 10 Jan 90 21:08:09 GMT
From: ipac.caltech.edu![e-mail]  (Dave Van Buren)
Subject: Electromagnetic Braking (Theory & #s)


                          Electrodynamic braking

The basic physics is that a moving conductor in a magnetized plasma excites
plasma waves that dissipate energy.  The effect was first described by

Drell, S.D., Folley, H.M., and Ruderman, M.A., 1965, Journal of Geophysical
Research, Vol. 70, p. 3131.

who used it to explain the anomalous acceleration observed for the Echo I
satellite.  Echo I was just a large aluminized mylar baloon used to bounce
radio signals for ionospheric and other studies.  The effect is efficient
when the Alfven speed ("sound" speed for magnetic plasma waves) exceeds

          v_A > c^2 / ( 4 pi l kappa )

where v_A is the Alfven speed, c is the speed of light, pi is 3.14...,
l is the transverse length of the object and kappa is its conductivity.
The Alfven speed corresponds to when the plasma thermal pressure equals
magnetic pressure

          rho v_A^2 = B^2 / ( 8 pi )

rho is the plasma mass density and B is the magnetic field strength.
Note that this is much less than .01 or .1 c except near neutron stars,
so the mechanism won't work for interstellar travel.  The simple reason
is that at these speeds the coupling to the plasma is too weak.  But the
effect can be noticed/used in the solar system, where v_A is usually
comparable to orbital speeds.

The rate at which energy is lost via the DFR mechanism is

       dE/dt = 4 ( B^2 / 8 pi ) ( Area ) ( v^2 / c )

where Area is the cross sectional area of the object (plates are better
that tethers) and v is the object's velocity through the magnetic field.
The effect is pretty small unless B is big, Area is big (plates, not
tethers),or v is big.  Echo I, which was several tens of meters across,
decayed in its orbit over months, and most of that was due to atmospheric drag.

For a spherical object with mean density rho_obj,  the decay time for
a Keplerian orbit is

      t_decay = E / (dE/dt)   .is about.   rho_obj l c / B^2

So a spherical Jupiter probe with size 100m radius, mass of 100 tons would
have an orbital decay time of 5 years (assuming a 10 G field).  Making the
cross section larger for the same mass, ie a flat plate flying face on,
slows it down faster.  The reason its not very effective is that the energy
energy density of the ionosphere of Jupiter (or almost any planet/star) is
pretty low.  The atmospheres on the other hand are dense and aerobraking
is much more effective for that reason.  All you have to do to slow down
is run into an amount of "air" that is comparable to your own mass.

The DFR electromagnetic drag mechanism has been applied to the theory of
asteroids and comets being captured by magnetized neutron stars.
After the capture, the orbit decays, and the object eventually crashes
onto the star's surface, releasing of order .1mc^2 of energy.  Not quite
a supernova explosion, but enough to cause the *observed* gamma ray bursts.
Of course, its just a theory, but I think its the most fun one.


  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  Dave Van Buren * IPAC 100-22 * CalTech * Pasadena CA 91125 * 818 584 2927
  - - - - - - - - - - - - - [e-mail] - - - - - - - - - - - - -

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

Date: Thu, 11 Jan 90 19:21:09 EST
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Gyroscopes


>From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
>Subject: NASA Headline News for 12/28/89 (Forwarded)

>The New York Times says Japanese scientists are conducting
>experiments with small gyroscopes that apparently defy the law of
>gravity...under certain conditions.    The experiments indicate
>weight changes when mechanical gyroscopes are spun in certain
>directions.  Dr. Robert Park, a physicist at the University of
>Maryland, says, "it's an astounding claim...but it's almost
>certainly wrong".

It's possible that not all magnetic and electrical influences were
properly ruled out. In particular, I would suspect induced electric
currents, and the buildup of electrostatic charges.

In a similar context, how's the cold fusion business these days? Last year,
there was considerable speculation on the uses of cold fusion in space travel.
My father thinks he heard a report of a recent experiment which tended to
support some of the claims of Pons and Fleischmann. Is this correct?
                        John Roberts
                        [e-mail]

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

Date: 11 Jan 90 18:05:46 GMT
From: shelby!portia![e-mail]  (Raul Izahi Lopez Hernandez)
Subject: On-Board Imaging Systems

Does anybody know what type of Imaging system does Magellan or Galileo
use to get pictures of the planets they are going to visit?

Also, what type of image aquisition systems are planned to be installed
in the space station Freedom for EOS (earth observation) work?

I'm currently working in a Image Processing system and this info would
be most welcome.

            RAUL IZAHI LOPEZ HERNANDEZ
            Electrical Engineering Department
            Stanford University.

        e-mail:    [e-mail]
            [e-mail]

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

Date: 12 Jan 90 00:24:45 GMT
From: swrinde!cs.utexas.edu!jarvis.csri.toronto.edu!helios.physics.utoronto.ca!physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Greg S. Hennessy) writes:
>In article <[e-mail]> [e-mail] (Neal Woodall) writes:
>#which you you rather be hit by, a bunch of fast neutrons or a bunch of beta
>#particles?
>
>As if there was a difference.
>
   Of course there's a difference. A neutron is a hadron and an electron is
a lepton. As for getting hit by one or the other, I'd rather it be betas
than fast neutrons, since the betas wouldn't penetrate to living cells.
Neutron flux can be fatal, but a multi-keV electron stream is harmless.
   By the way, I was recently corrected (thanks Henry) about the plutonium
in RTGs (from which I assume this question springs). The Pu238 is an alpha
emitter, and alphas have even less penetrating power than betas.

>-Greg Hennessy, University of Virginia
> USPS Mail:     Astronomy Department, Charlottesville, VA 22903-2475 USA
> Internet:      [e-mail]
> UUCP:        ...!uunet!virginia!gsh7w


--
 Christopher Neufeld....Just a graduate student  |
 [e-mail]              | The meek can have the
 [e-mail]                    | earth, I want the stars.
 "Don't edit reality for the sake of simplicity" |

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

Date: 11 Jan 90 23:48:42 GMT
From: vsi1!v7fs1![e-mail]  (Mike Van Pelt)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Greg S. Hennessy) writes:
>In article <[e-mail]> [e-mail] (Neal Woodall) writes:
>#which you you rather be hit by, a bunch of fast neutrons or a bunch of beta
>#particles?
>
>As if there was a difference.

Beta particles have an RBE (Relative Biological Effectiveness) of 1,
and only penetrate a millimeter or so.  Fast neutrons have an RBE of 5,
I think (was it fast=5 & thermal=10, or vice versa?) and penetrate all
the way through your body.

There is a difference.
--
Mike Van Pelt      Headland Technology/Video 7     ...ames!vsi1!v7fs1!mvp
"... Local prohibitions cannot  block advances in military and commercial
technology.... Democratic movements for local restraint can only restrain
the world's democracies, not the world as a whole." -- K. Eric Drexler

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

Date: Thu, 11 Jan 90 22:43:15 EST
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: KSC tours (long)


>From: zaphod.mps.ohio-state.edu!samsung!munnari.oz.au!sirius.ucs.adelaide.edu.au!chook.ua.oz![e-mail]  (Francis Vaughan)
>Subject: Visits to KSC and launches

>Since a few people have been asking, I thought it was about time to share
>my experiences in trying to witness a shuttle launch.

I tried to send you a message before your trip, which probably didn't get
there until you had left Australia. I went to KSC in August, and had a
more pleasant experience.

>I attempted to see the STS-34 launch scheduled for October the 12th. As it
>was, the launch was delayed enough that I missed it, but my experiences
>may be of some value.

>Despite all of Davids and the NSSs efforts NASA seems not to give [expletive]
>about mere mortals who may have tracked half way around the world to see
>and learn. The Cape is as I indicated a short distance from Disney and all
>the other tourist traps. KSC is nothing but a big tourist machine catering
>for people who take a break from wasting money at Disney and thought they
>might like to take the kids to see a few rockets.

It's probably more accurate to say that KSC is a working launch complex,
which tolerates tourists for PR purposes, and accomodates them in keeping
with its own safety standards. NASA doesn't even run the bus tours - they're
handled by a private company. Obviously, the tourist center was designed
by PR types.

>There is three decades of history sitting out there and nobody cares.

The rockets outside the visitor center have plaques next to them, so you can
read about them if you want to. I understand that the vast majority of
the tourists come for two main attractions: the Space Shuttle, and the
Apollo artifacts.

>You can't even buy NASA publications from the bookshop at KSC.

The bookshop seems to carry mostly photographs and souvenirs. I don't know
of any "popular" publications put out by NASA. For the serious stuff, you
probably need to deal with the technical part of NASA, or the US Government
Printing Office. Even using this approach, I think most of what you will
find are reports with names like "Analysis of Stresses and Erosion of
Carbon-fiber Composites in the Upper Atmosphere at Hypersonic Velocities".
For overview material, it may be necessary to rely on outside publications.

>The bus tours are appalling. Really appalling. It is hard to express my
>anger and frustration at the way these are conducted.

>There are two tours, the red and the blue. One takes you down the cape
>and shows you such unforgettable things as the launch control bunker for
>the Explorer shots. Outside this is a lawned area covered is old missiles
>and small rockets and interesting junk. They let you have ten minutes to
>see it. TEN MINUTES!! you can't even do justice to one exhibit in that
>time. As the bus left I saw a V-1 and V-2 for the first time out of the
>window. I had not enough time to walk completly around the lawn to even
>glance at the exhibits.

The bus tours change over time, depending on what is going on. When I went,
there was only one tour, which went through the Apollo display, stopped
at the VAB (did you notice the large birds sitting on top of the building?
they look tiny because the building is so large), to the launch area, then
back to look at the Saturn V. I think the reason they rushed you through
so fast was because there must have been a tremendous number of tourists
around launch time, who would have been even more angry if they didn't get to
go on the bus tour at all. Even when I went, I had to get there fairly early
in the morning to get a ticket for a 3:00 tour. On the other hand, we got
to spend a fairly long time at each stop, including at least 10 minutes
near the launch pads and 10 minutes near the Saturn V.

>The second tour takes you around the KSC facilities. Again amazing things
>to see, no time to see them. We saw the building where the Apollo
>astronauts trained on a simulated moonscape, complete with one of the
>remaining landers. Plus in the same room one of the remaining
>command/service modules. Probably less than five minutes viewing time.
>Then a ride out to the VAB, a quick look at one of the crawlers (BIG) a
>drive around the perimiter of the VAB (one door partially open and a stack
>inside). This is the closest you will get to a shuttle. Around the other
>side is the Saturn V we keep hearing mentioned rusting on the lawn. You
>are not given enough time to walk the length of the rocket. Literally, I
>ran with my camera taking pictures and did not make it further up than the
>bottom of the third stage before the bus driver was yelling at everyone to
>get back on the bus.

The path our bus took went from the VAB, right next to the road the crawlers
use to take the shuttles to the pads (interesting in itself - built several
feet deep for stability, and overlaid with flat pebbles from river beds -
you can see the crawler tracks (obviously the bus would not come this way
with a shuttle in transit)), past launch pad 39A (fairly close), and to a
point about a mile from the shuttle on pad 39B, which seems about as close
as they want anyone to come to an exposed shuttle. Even at that distance,
the shuttle is so big that you can use an ordinary telephoto lens on your
camera (I used 100-300mm) and pretty much fill your picture with the
shuttle. I got some nice stereo photos of the shuttle (!) which clearly
show the relative positions of the launch tower and the various parts
of the shuttle.

>The problem is that that the stuff you see on the tours is high on the must
>see list, and there is no other way of seeing it.

As Arthur C. Clarke wrote in "Against the Fall of Night", there is another
way. If you are in the US again, I hope you will have an opportunity to
visit the Air and Space Museum. (See comments)

>I came half way around the world, spent a lot of money and time and basicly
>got to spend less than an hour total time seeing what I came to see.

Yes, it is hard, especially with all the travel money you had to spend. On
the other hand, if you were already in the area, and didn't go with the
NSS package, you would have spent only a few dollars at the tourist center.

>The tour bus also takes you past launch pad A. Normally they let you off for
>a few minutes, but because of the RTGs fiasco nobody was let off the bus
>within sight of the launch pads (even though pad A was some miles off)
>in case they were a member of the Christics and wanted to picket the launch.

I was afraid that might happen. I'm glad I got there before those jerks
(Christics) ruined it for everybody. Maybe they'll be able to reduce security
again for future flights. Incidentally, the pads are surrounded by high
fences topped with really nasty "barbed wire", and I believe the area is under
constant surveillance.

>In summary, I would go with the NSS for a tour, take a camera, lots of film
>and burn film, because this is the only way you will get to see what is
>there; on your photos, you will not have time to register what is happening
>whilst you are there. If you want it all laid on and a bit of a holiday,
>take the four day package, if you only want the actual launch and can
>organise everything else (car, accomodation) get the one day launch special.

Yes, definitely bring a camera. I used up about 3-4 rolls of film.

>Dept of Computer Science                        Francis Vaughan
>University of Adelaide                          [e-mail]
>South Australia.

Comments:

 - The visitor center has a nice museum and several theaters. As soon as
you get there, dash over and get in line to buy your bus tour tickets.
These will probably be for a tour several hours later, so you will have
plenty of time to look at the displays. If you get there too late, the
bus tours may be sold out, so an early arrival is highly desirable.

 - The shuttle can be seen (at least if it's on pad B) from the grounds
of the VAB. When we stopped there, I got some nice long-distance telephoto
shots (300-600mm), because I did not know whether we would be allowed any
closer.

 - The main difficulties in long-distance photography are heat-shimmer
and haze. I suspect that these problems are reduced early in the day,
so it might be preferable to try for a morning bus tour. Definitely
use a haze filter.

 - I don't know how much of an advantage the NSS viewing sight might be.
The big shots (Vice President, astronauts' spouses, etc.) watch from about
3.5 miles away, which is the closest *anybody* is allowed during the
launch. (The beautiful pictures you see on TV and in magazines are taken
using close-up remote-controlled cameras, set up before the launch.)
I think the public viewing area is ~2 miles further away. I suspect the
most memorable impression of the launch is the *sound*, which can be heard
over a tremendous distance.

 - If your main concern is to get a good look at the shuttle, I suspect
your best bet is to go a week or more before launch (that's what I did).
Around launch time, it is guaranteed that there will be tremendous crowds,
with consequent degradation in the quality of the bus tours, and tourists
may not be allowed to see as much.

 - If your main interest is watching the launch, you should plan your
trip so the scheduled launch is early in your vacation, so you can wait
a few days if the launch is delayed by weather or other problems. In the
meantime, there are other tourist attractions in the area. I went to Epcot,
and found it fairly interesting. (It has some "real stuff" in addition to
the usual displays and rides, and there are displays showing the cultures
of various countries, in many cases run by people imported from those
countries. In keeping with the Disney tradition, it's clean by theme park
standards, most of the food is interesting and inexpensive (check out
the smoked mackerel in the Norwegian section), and the staff mostly seem to
be well-trained and helpful. Many of them speak several languages, which is
unusual in a US theme park.)

 - The crowding and quality of tours is likely to depend largely on the
time of year you go. Obviously the peak seasons for Disney World would
not be the best choice. If you go in the winter, don't be surprised if
it occasionally gets cold.

 - There's a cafeteria at the visitor center, which seems to usually
be very crowded.

 - There's probably a number to call to get all of this information officially.
I just wandered in, and things worked out OK.

 - For a really good look at US space hardware and information on the history
of the space program, it's hard to beat the Air and Space Museum (part of the
Smithsonian Institution) in Washington, DC. Unlike KSC, it's set up specifically
for tourists. There's an amazing amount of hardware there, not just rockets
and space probes, but also airplanes (Wright Brothers' Flyer, Spirit of St.
Louis, Voyager, X-15, Bell X-1, many war planes), helicopters, balloons,
space suits, etc. There's also an IMAX theater showing several movies each
day (inclucing footage shot from the Space Shuttle), and a planetarium.
Admission is free (there is a charge for the theaters). There's a very good
book and souvenir shop (with both "tourist" books and technical books on
aviation, space flight, and space science), plus several smaller shops and a
cafeteria. Packages are searched at the door for security reasons. The guards
start kicking everyone out about 20 minutes befor closing, so it's best to
arrive early. The museum stays open several hours later than usual in the
summer. I think it's the most popular tourist attraction in DC by number of
visitors, but I've never seen it too crowded to get in and look around
(it's a big building).

There's also an annex in Maryland where you can see workers actually restoring
the old planes for display (and sometimes flight). I've never been there,
but it sounds like an interesting place. There's a proposal to open an annex
at Washington Dulles (not National) Airport in Virginia, for the display
of numerous airplanes. Supposedly the prototype space shuttle Enterprise is
already sitting in some obscure spot at the airport for eventual inclusion
in the display.

(Disclaimer: these are just my impressions as a tourist. I don't know the
official policies of the organizations.)
                    John Roberts
                    [e-mail]

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

End of SPACE Digest V10 #416
*******************