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Date: Tue,  1 Jan 1991 04:22:37 -0500 (EST)
Subject: SPACE Digest V12 #708

SPACE Digest                                     Volume 12 : Issue 708

Today's Topics:
			  Re: Photon engine
	       Payload Status for 12/17/90 (Forwarded)
			   Ulysses article
		      Ulysses Update - 12/17/90
		       Bussard ramjet question
	     NASA Headline News for 12/17/90 (Forwarded)

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Date: Mon, 17 Dec 90 23:35:16 EST
From: John Roberts <roberts@cmr.ncsl.nist.gov>
Organization: National Institute of Standards and Technology
	formerly National Bureau of Standards
Disclaimer: Opinions expressed are those of the sender
	and do not reflect NIST policy or agreement.
To: space@andrew.cmu.edu
Subject: Re: Photon engine


>From: sdd.hp.com!samsung!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo!henry@ucsd.edu  (Henry Spencer)
>Subject: Re: Photon engine

>In article <9012040003.AA21365@cmr.ncsl.nist.gov> roberts@CMR.NCSL.NIST.GOV (John Roberts) writes:
>>React the matter and antimatter inside a huge chunk of radiation-absorbing
>>refractory material, and I bet most of the intermediate particles would break
>>down inside. Of course the neutrinos would still get out, and there doesn't
>>seem to be any way of directing them for propulsion. Any idea of (a) the
>>percentage of energy wasted in this way, or (b) the impulse per Joule-
>>equivalent of neutrinos as compared with photons? ...

>The neutrinos would contribute essentially nothing to thrust, even if you
>could beam them somehow.

Given the whichness of the why and all, I strongly suspect that the momentum
of a neutrino is equal to (energy-equivalent / c), same as for photons and
matter moving very close to c. What I don't know is the energy-equivalent
of a neutrino (is there more than one level?), and the percentage of energy
"wasted" by neutrino radiation in a typical matter-antimatter reaction. If
for some reason the percentage is high, and the neutrinos are mostly produced
by the breakdown of intermediate particles as you described, that could
possibly tilt the balance in favor of reaction mass versus pure photon drive.

>However, I think you miss the point, John.  You don't *want* to absorb the
>particles, if your objective is a near-photon engine.  Beaming the particles
>is vastly easier than beaming high-energy gamma rays, and you don't lose
>anything by working with the particles -- they carry no less momentum than
>the photons they will decay into.

Well, maybe a *very* tiny bit less.

>The only time you want to absorb the particles is if you are using them to
>heat much larger amounts of reaction mass, for higher thrusts and lower
>antimatter consumption at the price of much lower exhaust velocity.  In
>that case, there is some possibility that reacting the antimatter with
>heavier nuclei might be a win, as more of the energy might be caught
>in charged fragments.

I was trying to describe a completely theoretical pure-photon drive powered
by a matter-antimatter reaction, not an actual working antimatter drive that
someone might seriously propose. The system I described would use the power
source to heat the mass, then drive from the *thermal* radiation of the mass,
somehow made as directional as possible. No matter would be exhausted. Of
course, nobody in their right mind would actually build such a system, but
as we know, "net.space means never having to say you're serious".

In the original discussion, I was pointing out that in every practical case,
from an energy-efficiency standpoint (engineering details more or less
ignored), a photon (much less laser) drive from an internal power source
makes much less sense than other approaches. As a concession to the photon
enthusiasts, I found *one* exception: if you have available large quantities
of a fuel which can be "burned" to produce "pure energy" (represented by
a 50-50 mix of matter and antimatter in this case), and if this "fuel" is
cheap enough that cost is not a consideration (certainly not the case with
antimatter), and if the engineering problems are all solved in an elegant
manner (highly unlikely), then you get a very slight marginal advantage in
filling up your tanks with "fuel" and exhausting the output as a directed
beam of pure photons, as compared to reserving some of your (fixed) tank
space for inert reaction mass. Since nobody's going to do that, I think
that pretty much kills the internally-powered photon drive concept completely.

>"The average pointer, statistically,    |Henry Spencer at U of Toronto Zoology
>points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu   utzoo!henry
      John Roberts
      roberts@cmr.ncsl.nist.gov

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

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Date: 17 Dec 90 19:38:30 GMT
From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov  (Peter E. Yee)
Organization: NASA Ames Research Center, Moffett Field, CA
Subject: Payload Status for 12/17/90 (Forwarded)
Sender: space-request@andrew.cmu.edu
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            Daily Status/KSC Payload Management and Operations 12-17-90
            
            
            -    STS-35 ASTRO-1/BBXRT (at DFRF)
            
            Support for DFRF operations continue.
            
            
            -    STS-39 AFP-675/IBSS/STP-01
            
            At the VPF, SPAS will be rotated to vertical and it's keel
            will be installed.  Also, SPAS CYRO servicing wil be
            performed today.  At the OPF, CRO battery charging will be
            active today.
            
            
            -    STS-40 SLS-1 (at O&C)
            
            Power up testing will continue today.
            
            
            -    STS-37 GRO (at PHSF)
            
            No work is scheduled for today.
            
            
            -    STS-42 IML-1 (at O&C)
            
            Preps for rack and floor installation and paper closure
            continues.
            
            
            -    STS-45 Atlas-1 (at O&C)
            
            Experiment and pallet staging continue.
            
            
            -    STS-46 TSS-1 (at O&C)
            
            Partial pallet destaging continues.  Also the MPESS will be
            moved to the north rails today.
            
            
            -    STS-47 Spacelab-J (at O&C)
            
            No work is scheduled for today.
            
            
            -    STS-67 LITE (at O&C)
            
            Hard point installations continue.

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

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Date: 17 Dec 90 23:15:30 GMT
From: swrinde!elroy.jpl.nasa.gov!mahendo!jato!mars.jpl.nasa.gov!baalke@ucsd.edu  (Ron Baalke)
Organization: Jet Propulsion Laboratory, Pasadena, CA.
Subject: Ulysses article
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Associate Press -- 12/14/90
By Lee Siegal

"The Ulysses spacecraft is wobbling like an off-balance
washing machine, threatening to cripple the $750 million
U.S. - European mission to study the sun's poles."

Officials hope they can work around the malfunction so it
doesn't disrupt the five-year mission by preventing the
dish-shaped main antenna from pointing at the Earth
according to Siegal.

Said the European Space Agency's Edgar Page, "If we can't do
anything about it, it's very serious."  The loss of data could
range from 20 percent to 90 percent.

JPL Ulysses project manager Willis Meeks is quoted in the
wire service story, "Gloom is something I don't feel -- I'm
sure that somehow during the next four years we'll find a
way to learn to live with this problem."  Repeated firing of
the craft's thrusters was one possibility offered.

Ulysses problem is yet another in a series for NASA.
(Hubble, fuel leaks, Astro-1, recounted)  The slow wobble
began Nov. 4, upon extension of a 24 1/2 foot-long antenna
boom.  The wobble is expected to diminish then increase as
the probe nears the sun polar latitudes, says AP.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | baalke@mars.jpl.nasa.gov
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | baalke@jems.jpl.nasa.gov
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

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Date: 18 Dec 90 00:49:17 GMT
From: sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucsd.edu  (Ron Baalke)
Organization: Jet Propulsion Laboratory, Pasadena, CA.
Subject: Ulysses Update - 12/17/90
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                            ULYSSES STATUS REPORT
                              December 17, 1990

     On December 11, the 3rd meeting of the Nutation Investigation Team took
place to review the current situation and to discuss future strategy.  The
major output of this meeting was to commence Conscan operations and to observe
its effect on the nutation-like behavior.  The Conscan system on board the
spacecraft is designed to keep the High Gain Antenna pointed at the Earth.
It is an optional system which can be switched in and out of use as desired
operationally.  The successful use of Conscan for reducing nutation-like
motion was therefore a very important element in planning future operational
strategies.

     Following the meeting, a slew manuever was carried out which placed the
antenna pointing such that on December 12 center-of-Earth pointing would be
achieved.  On December 12 Conscan was switched on for 20 minutes and reduced
the nutation-like motion to within the deadband which had been set on board
prior to the operation (0.23 degrees).  Since Conscan had been so successful
in reducing the nutation, it was decided to further reduce the deadband by one
half and to leave Conscan for an extended period.

     This operation was done and the nutation-like motion was reduced to
within the deadband set (0.125 degrees).  After 2 hours Conscan was switched
off.  The nutation then built up until after 8 hours, it had reached a value of
1 Degree half-cone.

     On December 14 Conscan was switched on again but with an Earth-pointing
offset of 0.8 degrees which had occurred by natural drift since the last
manuever.  Once again the system was able to correct for the offset and
reduce the nutation to within the deadband.  After Conscan was switched off
the nutation increased over a period of 12 hours to a new stable value of 0.75
degrees half-cone.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | baalke@mars.jpl.nasa.gov
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | baalke@jems.jpl.nasa.gov
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

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Date: 18 Dec 90 01:24:25 GMT
From: celit!dave@ucsd.edu  (Dave Smith)
Organization: FPS Computing Inc., San Diego CA
Subject: Bussard ramjet question
References: <1990Dec17.235935.10244@news.arc.nasa.gov>
Sender: space-request@andrew.cmu.edu
To: space@andrew.cmu.edu

OK, I was thinking about Bussard ramjets the other day (after reading 
entirely too much science fiction) and got to wondering:  How do
you decelerate with a Bussard ramjet?  Your fuel (and reaction mass) is
coming at you, you would have to catch it and then accelerate it back 
the other way.  Do you have a fuel tank you fill up on the way for 
deceleration?  Is there enough friction against the ramscoop fields
to slow you down in a reasonable amount of time?  Has my brain been turned 
into mush?

--
David L. Smith
FPS Computing, San Diego        ucsd!celit!dave or dave@fps.com
"You can"t build a national and international network using TCP/IP"
--Laurie Bride, Boeing Computer Services

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

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Date: 17 Dec 90 19:37:51 GMT
From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov  (Peter E. Yee)
Organization: NASA Ames Research Center, Moffett Field, CA
Subject: NASA Headline News for 12/17/90 (Forwarded)
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             Headline News
Internal Communications Branch (P-2) NASA 
Headquarters

  Monday, December 17, 1990	Audio Service: 202 / 755-1788

This is NASA Headline News for Monday, December 17, 1990

Administrator Richard H. Truly will offer a live holiday 
address to NASA employees tomorrow at 12:00 noon 
Eastern time on NASA  Select television. In addition to his 
personal message to employees, he is expected to comment on 
the Augustine panel report and the subsequent senior 
management meeting.  


  * * * * * * * * * * * * * * * * * * * * * * * * * *  


Weather fronts across the U.S. delayed the departure of 
the Space Shuttle Columbia and its 747 carrier aircraft 
for Florida, yesterday.  Originally scheduled to depart from 
NASA's Dryden Flight Research Facility, Edwards, Calif., 
Sunday, the mated-combo is now expected to begin its cross-
country ferry flight at 4:00 pm Eastern time today.  First stop on 
the initial leg of the flight will be Biggs AFB, El Paso, Texas, 
where the two craft will remain overnight. Tuesday, the 
Columbia ferry will continue to Barksdale AFB, Lousiana and 
then proceed on to Kennedy Space Center, Florida.

At Kennedy Space Center, an emergency powerdown was 
performed on the Space Shuttle Discovery Friday night 
when a relay transformer in the uninterruptable power 
source in the Launch Control Center failed.  The 
transformer was replaced and power was restored about 16 
hours following the shutdown.  No damage resulted from the 
outage.  Work is continuing on Discovery, preparing it for 
powerdown Friday in preparation for the holidays.  The right 
hand OMS pod will be installed tonight, and the Forward 
Reaction Control system is scheduled to be installed Thursday.  
Atlantis is currently unpowered and was unaffected by the 
outage. 


* * * * * * * * * * * * * * * * * * * * * * * * * * 


Controllers at the Jet Propulsion Laboratory are 
watching over Ulysses as its "wobble" continues to 
decrease.  Media reports over the weekend included a 
"worst case scenario" that indicated a major loss of data, 
as the spacecraft passed over the sun's poles.  Project 
Manager Willis Meeks is confident that a thruster routine can 
be worked to dampen out the wobble, and insure 
communications with the craft as it performs its solar-polar 
science gathering.


	
Here's the broadcast schedule for Public Affairs events on NASA 
Select TV.  All times are Eastern.  **indicates a live program.

Monday 12/17/90

	    1:00 pm     NASA Radio Programs (audio)

Tuesday 12/18/90

	  12:00 noon    Holiday Message from 
		        NASA Administrator Richard H. Truly

Wednesday 12/19/90

	    1:00 pm     Galileo Press Conference from JPL

Thursday 12/12/90           

	   2:00 pm      STS-35 Crew Post Flight Press 
			Conference from JSC





All events and times may change without notice.  This report is 
filed daily, Monday through Friday, at 12:00 pm, EST.  It is a 
service of Internal Communications Branch at NASA 
Headquarters.  Contact:  CREDMOND on NASAmail or at 
202/453-8425.


NASA Select TV:  Satcom F2R, Transponder 13, C-Band, 72 
degrees West Longitude, Audio 6.8, Frequency 3960 MHz.

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

End of SPACE Digest V12 #708
*******************