Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v11_0/v11_011.txt

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Subject: SPACE Digest V11 #11

SPACE Digest                                      Volume 11 : Issue 11

Today's Topics:
              Galileo Update - 02/02/90
          Re: Spacecraft drives and fuel efficiency
            Re: private spaceplane
               Re : Nasa Headline News
           Re: ET paint (was: NASA Funding)
               More Info On SSX
           NASA Prediction Bulletin Format
Re: Magellan Update - 01/17/90: really about metric vs. imperial units
----------------------------------------------------------------------

Date: 5 Feb 90 22:28:35 GMT
From: elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 02/02/90


                               GALILEO
                         MISSION STATUS REPORT
                           FEBRUARY 2, 1990

     As of Friday, February 2, 1990, the Galileo Spacecraft is 26,043,650
miles from the Earth, 2,563,520 miles from Venus and is travelling at a
Heliocentric velocity of 81,222 miles per hour. Round trip light time is
4 minutes, 36 seconds.

     The recovery activity to reconfigure the spacecraft to a state for the
Venus flyby is proceeding well.  A total of 74 state changes are required to
get into the EV-6 initial state.  More than 50 percent of the state changes
have been accomplished to date; the remainder will be completed by February 6.

     The spacecraft remains in the all-spin mode and has completed nearly 40
automatic sun acquisitions (every 12 hours) since execution of the spacecraft
safing algorithms on January 15.

     The seventh RPM thruster "flushing" activity was successfully completed
on January 29.  The activity normally scheduled as a part of EV-5 was cancelled
when the spacecraft executed the safing algorithms.  The activity was performed
using real-time commands and only the Z, L and S thrusters were "flushed".
Since the P-thrusters are used for the routine sun acquisitions they were not
"flushed" during this activity.  The temperature profiles for the Z, L and S
thrusters were as expected and ranged from a peak temperature of about 69
degree C to 100 degree C, well within the predicted limits.

     A star scanner "A" calibration was successfully completed on February 1.
This calibration was performed to collect star data to aid with the
investigation into the inertial to cruise transition anomaly which occurred
in mid-January.

     The AC/DC bus imbalance measurements have remained relatively stable for
the last 2 to 3 weeks.  The DC measurement has fluctuated about 1 volt between
about 19.6 volts and 20.7 volts and the AC measurement has fluctuated about 5
volts between 43.8 and 48.7 volts. Review of imbalance measurement data prior
to and after entry into the spacecraft safing did not reveal any significant
measurement differences between dual-spin/all-spin operation.

     The first celestial reference acquisition activity since spacecraft safing
execution was successfully completed on February 2 after the automatic sun
acquisition via the sun point algorithm.  For this activity, the spacecraft was
in a sun-pointed attitude, in all-spin mode and sun-pointed stars were acquired
with SEQID converging as expected.  The successful completion of this SEQID was
an important event in the spacecraft recovery process for the Venus flyby.
Other crucial near-term attitude control events include a gyro parameter update
planned for February 3 (based on data collected during the minical).  This
update is expected to reduce scan platform pointing errors from about 5 mrad
to 1 mrad.

 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

Date: 5 Feb 90 20:44:05 GMT
From: psuvm![e-mail]
Subject: Re: Spacecraft drives and fuel efficiency

In article <[e-mail]>, [e-mail] (Mark Gellis)
says:
>
>Hi, I have a question I figured you people might be able to answer.
>I write sf as a hobby (hopefully for money someday), and I have a foolish
>desire to get as much of the science right as I can.
>
>                          I know that, in theory, you cannot get an Isp
>better than 30,000,000 (because it means you have an exhaust velocity of
>the speed of light), and I am curious as to how much you could get,
>assuming a technology that has to use our rules regarding physical
>principles, but has solved all or most of the technical problems.

Ah-hah! I'm sorry to jump down your throat, but my senior thesis is in
solar sail orbital mechanics. Solar sails, and some species of mircowave and
laser propelled craft, can have an infinite specific impulse. The specific
impulse of a propulsion system can be defined as
                     Thrust          1
              Isp = ----------- -----------
                    (mass flow) g(sea level)

Any vehicle that does not throw mass away while producing thrust will have an
Isp of infinity (whatever that means).

***************************************************************************
Mike Williams
[e-mail]

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

Date: 2 Feb 90 18:31:47 GMT
From: mcsun!ukc!tcdcs!swift.cs.tcd.ie!ccvax.ucd.ie![e-mail]
Subject: Re: private spaceplane

In article <[e-mail]>, [e-mail] (Norman C. Kluksdahl) writes:
>
> Some of you may recall a discussion starting about a year ago
> regarding private efforts to develop a small-scale shuttle/
> spaceplane.  After some initial confusion, I ended up being the
> designated coordinator of ideas, and began to have fun with the
> idea of a garage-scale EAA-type spaceplane project.  At first, it
> began as a 'Gedanken Experiment', merely a mental excercise to see
> if such a project was within the realm of possibility.

Sounds very interesting  -  as I'm not one of the ones who might remember this
discussion from before, (surely I'm not the only one) maybe you could bring us
up to date with your current state of thinking on this...

--------------------------------------------------------------------------------
Neil Conway                 | Disclaimer ? I'll be so surprised if this
[e-mail]            | even makes it onto the network...  (-:
--------------------------------------------------------------------------------

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

Date: 5 Feb 90 06:00:34 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo!censor!geac!maccs![e-mail]  (Stripper)
Subject: Re : Nasa Headline News

In a recent NASA headline news, it was reported that :
>Galileo is scheduled to arrive at Venus at 1:00am, Saturday,
>February 10.  According to Jet Propulsion Laboratory engineers,
>the actual computer sequence to control Galileo through the
>eleven-day fly-by has been developed.  It is now in final review
>and will be sent to the spacecraft on February 6.  The spacecraft

Are they really saying that they have just now developed the program
to control the probe during the fly-by???  Talk about flying by the seat
of the pants!  I can just see it now : "due to a slow programmer, Galileo
didn't know what to do on reaching Venus, and has plunged into the planet...
details at six"   :-)

John Clarke
[e-mail]

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

Date: 6 Feb 90 02:01:16 GMT
From: sun-barr!newstop!east!pyrite![e-mail]  (Steve Golson)
Subject: Re: ET paint (was: NASA Funding)

In article <[e-mail]> [e-mail] () writes:
>In article <5A0110121F340076-MTABWIDENER*DXANDY@widener> [e-mail] writes:
>> If NASA were to enter the
>>world of advertising, if only in a small way, surely it would be able to
>>bring in several millions of dollars.  For example, if the ET were to act as
>>huge billboard, I am sure that a company such as Coca Cola would pay massive
>>amounts to have it painted like a giant Coke can.
>
>The paint would also *weigh* massive amounts and that will decrease the
>payload. This is the reason that they quit painting the ET white. Like
>they did for the first missions.

As I recall from KSC press briefings for STS-3 (the first unpainted ET), the
paint weighs about 600 pounds. (The entire ET weighs 73000 or so.) I believe
the initial ones were painted white to help reduce the heat absorbed due to
sunlight etc., and it was determined to be unnecessary, resulting in some cost
savings.

Some press person asked if the launch trajectory would be noticeably different
due to the lighter weight...

Steve Golson         [e-mail]          [e-mail]
Trilobyte Systems -- 33 Sunset Road -- Carlisle MA 01741 -- 508/369-9669
       (consultant for, but not employed by, Sun Microsystems)
"As the people here grow colder, I turn to my computer..." -- Kate Bush

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

Date: 6 Feb 90 00:14:48 GMT
From: orc!mipos3!omepd!omews10.intel.com![e-mail]  (Larry Smith)
Subject: More Info On SSX


I recently (2/5/90) got some interesting information on
SSX from [e-mail] (Edward V. Wright). He told me
that I could post this information for him, because
there are some problems at his site with net posting.
I had no trouble getting to him or getting replys from
him at the above address.

Jerry Pournelle, who heads the Lunar Society and chairs
the Citizen's Advisory Council on Space, held a conference
on SSX on GENIE (the General Electric Network Info.
Exchange -- whew, too many acronyms!) last week.  I was
invited, couldn't attend, but had a friend sit in on it
for me.

We have some problems which generally prevent posting to
the net from this site, BTW.  If you would like to post
this information, be my guest.

SSX was originally designed for the Citizen's Advisory Council
on Space by Max Hunter of Lockheed and Gary Hudson of Pacific
American Launch Systems.  The basic design is closely based on
Pac Am's proposed "Phoenix" launch vehicle.

The National Space Advisory Council has decided to support both
NASP and SSX.  The Strategic Defense Initiative Organization
(SDIO) has been named lead agency for SSX.  SDIO will release a
request for proposals to build SSX sometime next month.  The
RFP calls for first flight in less than 5 years and a development
cost of between $1 and $4 billion.  At least three aerospace
companies are planning to bid on the contract.

The original design payload for SSX was 3000 lb to a 120-mile
orbit.  The technical committees appointed by the NSAC to review
the proposed subsituted some new materials developed for the
NASP into the basic design and now predict a useful payload of
9000 to 20,000 lb.   Test flights and later operational launches
will be conducted from somewhere in the Western desert (both
Edwards AFB and China Lake have been suggested as possible sites).

SSX, or Space Ship eXperimental, is an X-class research vehicle,
but with a useful payload.  It is anticipated that both the Air
Force and the Army will want several SSXs for various missions.
In addition, the Lunar Society plans to buy three to support its
lunar colony project.  (SSX can be refueled in orbit and travel
anywhere in the solar system.  Nine SSX tanker flights would be
required to refuel one SSX in orbit for a round-trip lunar flight.)

The first SSX will probably use RL-10 rocket engines, which
have been around a long time and are very reliable (they are
used on the Centaur upper stage).  The anticipated cost of
each vehicle is around $30 million, yielding launch costs
of about $50 per pound of payload in Low Earth Orbit.  Later,
as the design evolves, this could go even lower.  There are
also two private consortia interested in developing commercial
derivatives of SSX, in much the same way that Boeing developed
the model 707 from the Air Force KC-135 tanker.

Larry Smith for Edward V. Wright

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

Date: 5 Feb 90 06:13:24 GMT
From: helios.ee.lbl.gov!ncis.tis.llnl.gov!blackbird![e-mail]  (TS Kelso)
Subject: NASA Prediction Bulletin Format


As a service to the satellite user community, the following description
of the NASA Prediction Bulletin's two-line orbital element set format is
uploaded to sci.space on a monthly basis.  The most current orbital elements
from the NASA Prediction Bulletins are carried on the Celestial RCP/M, (513)
427-0674, and are updated several times weekly.  Documentation and tracking
software are also available on this system.  The Celestial RCP/M may be
accessed 24 hours/day at 300, 1200, or 2400 baud using 8 data bits, 1 stop
bit, no parity.

==============================================================================

Data for each satellite consists of three lines in the following format:

AAAAAAAAAAA
1 NNNNNU NNNNNAAA NNNNN.NNNNNNNN +.NNNNNNNN +NNNNN-N +NNNNN-N N NNNNN
2 NNNNN NNN.NNNN NNN.NNNN NNNNNNN NNN.NNNN NNN.NNNN NN.NNNNNNNNNNNNNN

Line 1 is a eleven-character name.

Lines 2 and 3 are the standard Two-Line Orbital Element Set Format identical
to that used by NASA and NORAD.  The format description is:

Line 2
Column     Description
 01-01     Line Number of Element Data
 03-07     Satellite Number
 10-11     International Designator (Last two digits of launch year)
 12-14     International Designator (Launch number of the year)
 15-17     International Designator (Piece of launch)
 19-20     Epoch Year (Last two digits of year)
 21-32     Epoch (Julian Day and fractional portion of the day)
 34-43     First Time Derivative of the Mean Motion
        or Ballistic Coefficient (Depending on ephemeris type)
 45-52     Second Time Derivative of Mean Motion (decimal point assumed;
           blank if N/A)
 54-61     BSTAR drag term if GP4 general perturbation theory was used.
           Otherwise, radiation pressure coefficient.  (Decimal point assumed)
 63-63     Ephemeris type
 65-68     Element number
 69-69     Check Sum (Modulo 10)
           (Letters, blanks, periods = 0; minus sign = 1; plus sign = 2)

Line 3
Column     Description
 01-01     Line Number of Element Data
 03-07     Satellite Number
 09-16     Inclination [Degrees]
 18-25     Right Ascension of the Ascending Node [Degrees]
 27-33     Eccentricity (decimal point assumed)
 35-42     Argument of Perigee [Degrees]
 44-51     Mean Anomaly [Degrees]
 53-63     Mean Motion [Revs per day]
 64-68     Revolution number at epoch [Revs]
 69-69     Check Sum (Modulo 10)

All other columns are blank or fixed.

Example:

NOAA 6
1 11416U          86 50.28438588 0.00000140           67960-4 0  5293
2 11416  98.5105  69.3305 0012788  63.2828 296.9658 14.24899292346978

Note that the International Designator fields are usually blank, as issued in
the NASA Prediction Bulletins.

--
Dr TS Kelso                           Asst Professor of Space Operations
[e-mail]          Air Force Institute of Technology

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

Date: 5 Feb 90 17:50:06 GMT
From: zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!jarthur![e-mail]  (John H. Kim)
Subject: Re: Magellan Update - 01/17/90: really about metric vs. imperial units

In article <[e-mail]> [e-mail] writes:
>In discussing why he thinks nautical miles are an advantageous unit
>for navigation, John writes this:
>
>>[My stuff deleted]
>
>After using several trig functions to get the arc distance, why is it a
>hassle to multiply the number of degrees by 111.1 to get kilometers
>rather than multiplying by 60 to get nautical miles?

Why is it a hassle for you to go through the articles you read and
convert NASA's English units to metric?  Seriously, 60 is easier to
remember (number of minutes in a degree). 111.1 could be misrecalled
as 111 or even 100, which could lead to nasty consequences.  Don't
take this as a flame, see below.

>remember that the meter
>was defined as one ten millionth of the distance from the north pole to
>the equator, so it is easy to remember that the earth is about 40,000
>km around.

Well, that brings up why there are 360 degrees in a circle, not 100.
(so you can easily find halves, thirds, fourths, fifths, sixths, eights,
tenths, twelfths, etc.).  But that's another argument...

>I think it is long past time for NASA and other government agencies to
>start using metric units, and I see practically no benefit from a
>computational standpoint to the use nautical miles.

First, let me say that I almost completely agree with you.  Your argument
has gotten me to shift my opinion from "NASA can use nautical miles if it
wants to" to "NASA should use nautical miles only to facillitate the
recovery of SRB's at sea."

But there's a point you're missing.  I'm sure a NASA Ph.D. rocket
scientist could easily go back and forth between nautical miles (nmi)
and km.  But nmi's are used mainly by sea and air traffic.  Trying to
convert them from nmi to km is pretty much a lost cause.  Most of
these navigators only understand that plugging this and that number
into this formula will spit out nmi.  Trying to force km onto them
is going to cause a lot of confusion.  There's a really big difference
between messing up a unit conversion on land and on sea.  On land, you
say oops, find the next road sign, fill up at a gas station, and drive
an extra hour or so.  On sea, you look around, see no land anywhere,
take some navigational readings, wonder if you won't make the same
mistake, wonder if you'll have enough fuel, panic, and if you're
unlucky, die after drifting for a few weeks.
--
John H. Kim                 | (This space to be filled when I
[e-mail] | think of something very clever
uunet!muddcs!jarthur!jokim  | to use as a disclaimer)

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

End of SPACE Digest V11 #11
*******************