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Subject: SPACE Digest V10 #274

SPACE Digest                                     Volume 10 : Issue 274

Today's Topics:
             Re: Lunar stationary skyhook
             Re: Galileo boost from Venus
           Payload Status for 11/22/89 (Forwarded)
            Antimatter Drives and Area 51
               shuttle question
         Re: Planetary Society - net address
        Re: Asteroid strikes and warning times
----------------------------------------------------------------------

Date: 22 Nov 89 16:19:40 GMT
From: gem.mps.ohio-state.edu!usc!cs.utexas.edu!mailrus!jarvis.csri.toronto.edu!me!helios.physics.utoronto.ca!physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: Re: Lunar stationary skyhook

In article <[e-mail]> [e-mail] writes:
>>>From: mcsun!ukc!edcastle![e-mail]  (Bob Gray) (17 nov 89)
>>>A small asteriod "hung" from the Moon by cables would be
>>>more stable yet, and make a good base to build a shipping
>>>station on.
>>   Yes, this would shorten the required length of cable. The ballast
>>would have to lie somewhere between L1 and earth. (18 nov 89)
>> Christopher Neufeld....Just a graduate student  | "Out of my way,
>> [e-mail]                    | I'm a scientist!"
>
   For reference, here is Mr. Michelet's drawing. He also sets the
scenario:
>  *----=====*0*====----( . )
>  ^          ^         ^ ^
>  !          !         ! +- Cross-section of Earth/Moon (center)
>  !          !         +--- Equator - anchor point of the cable
>  !          +---- stationary orbit - largest section/Midway station
>  +----- End of cable: counterweight.
>
>The good place to place a station is of course at the stationary
>orbit:  since any mass is weightless at this place, it can be as
>bulky as needed. Now once the cable construction is over, its end
>will reach the ground without any pull: the station is still at an
>equilibrium.  The bottom end is then anchored, and then a
>counterweight is added at the opposite side. Since centrifuge force
>exceeds gravitation in that area, the effect is to pull on the
>cable, resulting in a tension that is balanced by the anchor point.
>
>would you call it?) and the traction is gradually transferred from
>the ascending payload to the ground anchor. Coriolis forces tend to
>slow the cable's rotation while the payload is climbing, so that the
>cable bends backwards: cinetic momentum is thus transferred from the
>planet to the ascending object.
>
   Yes, quite true. So, now the stationary station at L1 is pulled out of
its equilibrium position, having been displaced in the plane perpendicular
to the line connecting the earth and moon. The L1 point displays positive
stability in this direction. The earth-moon system tends to pull the
stationary satellite back to the L1 point. This is a transfer of angular
momentum from the earth-moon system which returns the station to its
unperturbed position. The station doesn't have a memory of total mass
passing up or down the cable. The ballast and anchor keep the station from
moving in the unstable direction, toward or away from the moon.

>The first remark here is that no mass can be permanently added
>between the ground and the stationary orbit: this would result in a
>useless increase of the cable's tension.
>
   No. There might be a transient increase in tension, but the cable would
return to its optimal configuration. Of course the cable doesn't have to
exert a force to hold the cargoes at stationary orbit once they're there,
from the definition of a stationary orbit.

>The second one is that a
>payload should not go beyond the stationary point unless the
>counterweight is accordingly lowered: otherwise the cable's tension
>would exceed its working point.
>
   Not quite. Let's assume I've built a free-standing cable 300000 km long,
passing through L1. It has no anchor, and no ballast, and is not stable
with respect to motion in the radial direction. Lets assume this cable can
support another T newtons of tension before breaking. I now anchor the
planet end of the tether, and put a ballast on the far end of sufficient
mass to exert a force of T/3 newtons away from the planet. I can now lift
payloads from the planet to stationary orbit which weigh up to T/3 newtons
on the planet's surface. If I now "lower" this payload toward the ballast
(yet further away from the planet), the ballast arm of the tether has a
tension of 2T/3 above that of the free-standing cable. Assuming the anchor
is strong enough (and that's not a weak link in the system), this structure
will not be damaged by moving this payload out to the ballast. I've built
in a T/3 safety margin so no nit-pickers will argue that the cable might
snap.

>Now, a small asteroid hung on the cable can make a good
>conterweight, but it has to be realy small so as not to split the
>cable under its weight. And it can not be used as a building station
>on the stationary point, since that would mean bringing it in an
>unstable Lagrange orbit.
>
   Please note this: "unstable Lagrange orbit". I'll refer to this later.

>Furthermore, if too massive it cannot be placed
>on Moon's stationary orbit at all, since the lagrange point is
>unstable: if the intermediary L2 station is too massive, the
>stabilisation effect of the ballast will not be enough and the whole
>construction will go adrift.
>
   Yes, it will be a problem if it is "too massive". Just don't build it
the size of Texas. The actual limitation here is the eccentricity of the
moon's orbit. The L1 point moves back and forth past the stationary
satellite, unless the anchor point is put on a huge winch (I think this
would be impractical). The L1 point moves from 67200 km (from the moon's
centre) at aphelion to 51100 km at perihelion. If the cable is set so that
the so-called stationary point is at the mean L1 position, then that
station would find itself under an effective gravity of 6.4e-4 m/s^2 at
aphelion and at perihelion. Part of my T/3 safety margin would go to
absorbing these extra strains. Caveat: for the positions of L1 at
perihelion aphelion I used only a first order perturbation, I didn't take
into account the change in angular velocity at these points.

>given cable tension. But all the lengths given are those between
>ground (or planet center) and stationary orbit, which is the only
>useful part: the extra length needed to hold the ballast is never
>included in these figures.
>
   In my postings I assumed an initially balanced cable. The 300000 km is
the total length, not the distance to the stationary point. As quoted
above, the stationary point is, on average, 58200 km from the centre of the
moon.

>Finally, -flame time: beware!- I would like to comment some figures
>Christopher Neufeld quoted without his teacher's permission:
>
   Actually, I got rid of that annoying disclaimer a couple of months ago
when I got my own account.

>>...through L1 would be...300_000km...An L2 skyhook is 550_000km long...
>
>Don't forget the Moon-Earth distance is about 380_000 km: the first
>point cited here is one of the two placed on an equilateral triangle
>with respect to Earth and Moon,
>
   Oops, you've missed the point. Those are the L4 and L5 points. I'm not
talking about those. Those points are fully stable (remember earlier, you
were talking about unstable Lagrange points).
   Here are the Lagrange points I am using: L1 is the 2/3 stable Lagrange
point which lies between the massive primary and the lighter satellite. The
L1 point is close to the lighter satellite. L2 is the 2/3 stable Lagrange
point which lies on the line connecting the massive primary and the lighter
satellite, but is beyond the satellite. Seen from the earth, L1 is
somewhere in the middle of the face of the moon. L2 is behind the moon.
L1 lies on average 58200 km from the centre of the moon. L2 lies on average
a distance of 64200 km from the centre of the moon, and on the far side.

>position. Both of these points are of course completely useless.
>This is the second time you quote _The Endless Frontier_.  Seeing
>something printed dosen't make it true.
>
   I've done the calculations myself. Here is some additional information:
For an L1 tether, the total length is about 292000 km for a balanced cable.
The taper is exp(2.7e6 * p/Y) where p is the density in kg/m^3 and Y is the
tensile strength in N/m^2. For nylon fiber, this is a taper of 20.
   I'm not trying to start a flame war. Just remember:
> (keep smiling- we all make mistakes).
>
>                             Bertrand MICHELET
>                             UDOC140 at FRORS31 (BitNET)


--
 Christopher Neufeld....Just a graduate student  | "Space probe may be
 [e-mail]                    | Doomsday machine!"
 [e-mail]              |   -Toronto Star article
 "Don't edit reality for the sake of simplicity" | on Galileo 19/11/89

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

Date: 22 Nov 89 17:25:13 GMT
From: idacrd![e-mail]  (Robert McGwier)
Subject: Re: Galileo boost from Venus

From article <[e-mail]>, by [e-mail] (Rick Ellis):
> In article <[e-mail]> [e-mail] (Brian Holtz) writes:
>>Let me ask this again:
>>
>>If the attraction between Galileo and, say, Venus is the same
>>when Galileo is coming and going, how does the encounter speed
>>up the craft?  Does it have something to do with the fact that it's
>>passing Venus as they both orbit the the sun?
>
>
> Look at it as changing the direction of the orbit.  Speed doen't change but the vector does.
>aa




For an observer sitting at the center of Venus, for the most part the speed
doesn't change but the direction does.   THAT IS NOT TRUE for observers
elsewhere in the solar system and using different reference frames and thus
the assist.

Bob

--
____________________________________________________________________________
    My opinions are my own no matter    |    Robert W. McGwier, N4HY
    who I work for! ;-)            |    CCR, AMSAT, etc.
----------------------------------------------------------------------------

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

Date: 22 Nov 89 19:09:53 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: Payload Status for 11/22/89 (Forwarded)

Daily Status/KSC Payload Management and Operations 11-22-89


- STS-31R HST (at VPF) -

Functional testing is on hold for now.  LMSC is awaiting word from
Sunnyvale before continuing with testing.  Facility monitoring
and environmental monitoring support is on going.

- STS-32R SYNCOM (at VPF) -

SYNCOM was successfully transferred to the PCR PGHM yesterday.
Hughes battery charged SYNCOM late last night.  The PCR was
secured early this morning and will remain that way until after
launch tonight.  The canister and transporter will remain at
Pad-A until after launch.

- STS-35 ASTRO-1/BBXRT (at O&C) -

IPR troubleshooting of the RAU-Z and experiment inverter was
performed yesterday.  Both are suspected to be bad.  Began with
RAU and inverter change out yesterday and it will continue this
morning.  After completion of change out, the system will be
powered up for checkout.

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

Rack 7 and 9 modifications were performed yesterday.  Eddy
current inspection of rack 7 was done and no defects were found.
Water servicing GSE and pyrell foam replacement continues.

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

No activity to report.

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

Date: 22 Nov 89 18:03:07 GMT
From: amdahl!drivax![e-mail]  (MacLeod)
Subject: Antimatter Drives and Area 51

In article <[e-mail]> paj@mrcu (Paul Johnson) writes:

:A couple of months ago I read Robert Forward's book "Mirror Matter" in
:which he suggests that the practical use of antimatter is now
:possible.  Are his ideas impractical?  If not, what is being done
:about them?

Glad you asked about antimatter.

According to a series of reports on two Las Vegas television stations
(there is a two-hour special coming on 11-25 for those in the LV area)
one Robert Lazar, formerly employed by the government at the mysterious
Area 51, says that the US government has 500 pounds of element 115,
which somehow produces antimatter when irradiated.

This fuel is used to drive waveguide-type gravity amplifiers which
are the FTL drive components of nine alien spacecraft stored in hangars
out at Area 51 (the supersecret testing grounds also known as "Dreamland"
in the middle of the Nellis AFB bombing range about 65 miles northeast of
Las Vegas).  From his brief description of how the drives operate, they
seem to create local black-hole strength gravity gradients which slow down
time and cause a space-fold quickly traversible by the spacecraft.

Lazar says he was hired to continue covert research into these spacecraft
and their engineering infrastructure after a former team of scientists
had screwed the pooch with a batch of element 115, forcing the AEC to
hurridly announce an "unscheduled" atomic test at Dreamland.

Don't flame me, call KLAS-TV in Vegas if you're curious.  They will be
selling copies of the 2-hour special, due to the outpouring of interest
in it - stimulated by word of mouth and news propagated by ParaNet.
For some odd reason the national media have not paid any attention...

You can also get on the ParaNet mailing list by sending a note to:

    scicom!infopara


Michael Sloan MacLeod   (amdahl!drivax!macleod)

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

Date: 23 Nov 89 05:10:00 GMT
From: ux1.cso.uiuc.edu!ux1.cso.uiuc.edu!uxa.cso.uiuc.edu![e-mail]
Subject: shuttle question


What's all that sparks that fly around under the shuttle before it launches?
They seem to get all excited just before the real launch and fizzle around
the next. isn't it dangerous to have open flames near the gas nozzles? what
if rocket fuel leaks out? anyway I'm sure there must be a good reason
for them.
I wonder if some ineexpensive addative could be made that wouldn't
reduce fuel effectiveness but make the sparks or better yet the
flame blue.

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

Date: 23 Nov 89 21:24:42 GMT
From: philmtl!atha![e-mail]  (Ralph Hand)
Subject: Re: Planetary Society - net address


I gave up on the Planetary Society a couple of years ago, mainly because
I did not seem to be getting anything for my money, plus the fact that
they did not seem interested in anything outside those space ventures that
invovled citizens of the US directly.  Also, in the couple of years that
I was a member the number of newsletters that I received could not have
numbered more than four and they were not willing to fix the situation.

Ralph


* These are the opinions of my opinions not my employers and I cannot help
it if my opionions are opinionated ( as opinions tend to be). *

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

Date: 24 Nov 89 17:14:43 GMT
From: mcsun!ukc!icdoc!syma![e-mail]  (Andy Clews)
Subject: Re: Asteroid strikes and warning times

>>If they could give a warning would it be early enough to
>>do anything?  ...  I'm wondering if there would be enough time
>>to get out the word that this is a natural disaster and not a first strike.

Warning: slightly dark humour follows. Sprinkle :-)'s liberally as
required:

If the asteroid was big enough to start a "nuclear winter" as a result
of its impact, which would probably spell the end for most of us, maybe
if it *was* confused with a nuclear first strike and set off a
nuclear exchange, it would perhaps help speed up the inevitable; after all,
I think I'd rather be zapped than slowly freeze to death. :-) :-)

Me, I'd probably go sit in Trafalgar Square, feed the pigeons and wait.

:-) :-) :-) :-) :-| :-(


--
Andy Clews, Computing Service, Univ. of Sussex, Brighton BN1 9QN, ENGLAND
JANET: [e-mail]   BITNET: [e-mail]
Voice: [phone] ext.2129

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

End of SPACE Digest V10 #274
*******************