Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Tue, 6 Feb 90 01:30:16 -0500 (EST) Message-ID: <4ZnavOO00VcJA9C04=@andrew.cmu.edu> Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 6 Feb 90 01:29:47 -0500 (EST) 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!baalke@decwrl.dec.com (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 | baalke@mars.jpl.nasa.gov Jet Propulsion Lab M/S 301-355 | baalke@jems.jpl.nasa.gov 4800 Oak Grove Dr. | Pasadena, CA 91109 | ------------------------------ Date: 5 Feb 90 20:44:05 GMT From: psuvm!mrw104@psuvax1.cs.psu.edu Subject: Re: Spacecraft drives and fuel efficiency In article <7007@mentor.cc.purdue.edu>, f3w@mentor.cc.purdue.edu (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 mrw104@psuvm.edu ------------------------------ Date: 2 Feb 90 18:31:47 GMT From: mcsun!ukc!tcdcs!swift.cs.tcd.ie!ccvax.ucd.ie!h235_022@uunet.uu.net Subject: Re: private spaceplane In article <19120@nuchat.UUCP>, moe@nuchat.UUCP (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 H235_022@CCVAX.UCD.IE | 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!cs3ga3ab@tut.cis.ohio-state.edu (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 cs3ga3ab@maccs.dcss.mcmaster.ca ------------------------------ Date: 6 Feb 90 02:01:16 GMT From: sun-barr!newstop!east!pyrite!sgolson@apple.com (Steve Golson) Subject: Re: ET paint (was: NASA Funding) In article <1990Jan21.125021.10579@mathrt0.math.chalmers.se> d9bertil@dtek.chalmers.se () writes: >In article <5A0110121F340076-MTABWIDENER*DXANDY@widener> DXANDY@WIDENER.BITNET 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 sgolson@East.sun.com golson@cup.portal.com 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!larry@decwrl.dec.com (Larry Smith) Subject: More Info On SSX I recently (2/5/90) got some interesting information on SSX from ewright@convex.com (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!tkelso@ucsd.edu (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 tkelso@blackbird.afit.af.mil Air Force Institute of Technology ------------------------------ Date: 5 Feb 90 17:50:06 GMT From: zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!jarthur!jokim@tut.cis.ohio-state.edu (John H. Kim) Subject: Re: Magellan Update - 01/17/90: really about metric vs. imperial units In article <4641@druhi.ATT.COM> neal@druhi.ATT.COM 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 jokim@jarthur.Claremont.EDU | think of something very clever uunet!muddcs!jarthur!jokim | to use as a disclaimer) ------------------------------ End of SPACE Digest V11 #11 *******************