Date: Fri, 15 Jan 93 05:03:48 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V16 #049 To: Space Digest Readers Precedence: bulk Space Digest Fri, 15 Jan 93 Volume 16 : Issue 049 Today's Topics: averting doom Elementary Ballistics Freedom's orbit Galileo's History (Was Re: Galileo Stuck Ribs / Remote Manipulator?) Galileo Stuck Ribs / Remote Manipulator? (3 msgs) Galileo Update - 01/14/93 Phone number to save Goldin Saving an overweight SSTO.... SNC meteorites Subjective Safety Measure(Re: man-rating) Supporting private space activities TPS Systems youth astronomy groups Welcome to the Space Digest!! Please send your messages to "space@isu.isunet.edu", and (un)subscription requests of the form "Subscribe Space " to one of these addresses: listserv@uga (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle (THENET), or space-REQUEST@isu.isunet.edu (Internet). ---------------------------------------------------------------------- Date: 14 Jan 93 19:10:32 GMT From: Mark Wilson Subject: averting doom Newsgroups: sci.astro,sci.space,sci.physics,sci.environment In article <1993Jan13.225015.24673@stsci.edu> vener@stsci.edu (Patricia C. Vener-Saavedra) writes: |Hi there. As I recall, in about a billion years the sun will have |about twice the luminosity it presently has. The average surface of |Earth will be about 100 degrees C. Some lakes and rivers will have |begun to boil. It will not be pleasant for homo sapiens.:-) Now this is what I call long range planning. -- Mob rule isn't any prettier merely because the mob calls itself a government It ain't charity if you are using someone else's money. Wilson's theory of relativity: If you go back far enough, we're all related. Mark.Wilson@AtlantaGA.NCR.com ------------------------------ Date: 14 Jan 93 15:59:40 GMT From: Steve Boylan Subject: Elementary Ballistics Newsgroups: sci.space,sci.physics,alt.pagan Gee, this sounds like it ought to be a simple question . . . What speed (using the term to refer to the magnitude of the velocity vector) must be imparted to a body at the surface of the Earth to achieve low Earth orbit? I've seen estimates bandied about that ranged from 2.2 km/sec. to 8 km/sec. Naturally, I can't recall enough of basic mechanics to figure it out for myself, and I can't find my mechanics text . . . At the root of this question is a raging discussion on what types of Earth-based launcher might be practical for different payloads - which ought to explain the bizarre cross-posting. Basically, if you're going to launch something using a railgun, coilgun, gas gun, or some other accelerator, how fast will you have to get it moving? That ought to be the basic design constraint - from that you can choose your combination of length versus acceleration. If I remember my ballistics correctly, in the absence of an atmosphere, something launched by acceleration on the surface can achieve an elliptical orbit . . . that is tangent to the surface, which is probably not good on a body like the Moon and decidedly a problem with an atmosphere around. What kind of change in velocity is needed to round out the orbit so it would stay outside the Earth's atmosphere? For that matter, how much extra work do you need to do to get a payload out of the Earth's atmosphere? Any takers? - - Steve -- Don't miss the 49th New England Folk Festival, April 23-25, 1993 in Natick, Massachusetts! ------------------------------ Date: Thu, 14 Jan 1993 17:21:33 GMT From: "Shadan M. Ardalan" Subject: Freedom's orbit Newsgroups: sci.space In article accfif@engin.umich.edu (Sean C Fifield) writes: > I'm interested in orbital information (altitude, eccentricity, >inclination, etc.) about the space station Freedom. Has NASA >released information about the orbit they are planning to put >Freedom into? If so where can I get a hold of it or who can I >contact? > Could someone E-mail me or post an article if they know? Thanks. > >Sean Fifield >University of Michigan > This isn't the gospel....but last I heard, Freedom is to be in roughly a 200 nmi circular orbit inclined 28.5 degrees (a standard inclination for launching due east from the Cape)....will someone please confirm or correct my numbers?......thanks Shadan M. Ardalan ------------------------------ Date: 14 Jan 93 19:44:50 GMT From: Ron Baalke Subject: Galileo's History (Was Re: Galileo Stuck Ribs / Remote Manipulator?) Newsgroups: sci.space,sci.astro,alt.sci.planetary In article <1993Jan14.161958.10711@gn.ecn.purdue.edu>, mechalas@gn.ecn.purdue.edu (John P. Mechalas) writes... >...you'd be amazed at what the designers of Galileo had to put up >with...it's amazing the program is still alive. That's an understatement. Here's a history of what the Galileo mission had to go through before it was finally launched. 1975 - NASA decides that the proposed Jupiter Orbiter Mission (JOM) will be the first planetary spacecraft launched on the Space Shuttle. The mission was later renamed to Galileo. 1977 - Congress nearly cancels the Galileo program, but it survives and is approved for launch in 1982 and arrival in 1985. A new IUS (Interim Upper Stage) is to be built that will propel Galileo directly to Jupiter. 1980 - The Space Shuttle program falls far behind schedule and Galileo's launch is slipped to 1984 with arrival delayed until 1986. Since the 1984 trajectory is unfavorable NASA decides on a major engineering change. The spacecraft is split in two, an orbiter section and an atmospheric probe section, and are to be launched separately. The spacecraft and the mission are completely redesigned. 1981 - The IUS (now cleverly renamed to Inertial Upper Stage) cannot meet its design specs and cannot propel Galileo directly to Jupiter. NASA opts for the more powerful liquid fueled Centaur stage. The probe and orbiter are recombined for a single launch, and the spacecraft and mission are redesigned once again. The launch date is slipped to 1985. 1982 - David Stockman cancels the Galileo program. The program is restored by Congress. 1984 - Problems with the Space Shuttle and Centaur delay the launch again to 1986 with arrival in 1988. 1986 - Challenger explodes just four months before Galileo was to have been launched. The Centaur program is cancelled for safety reasons. Without a launch vehicle to get the spacecraft to Jupiter, the mission is once again on the verge of cancellation. 1987 - The VEEGA trajectory is developed and can get Galileo to Jupiter using the IUS. Galileo is scheduled again for launch in 1989. Cruise time to Jupiter with the VEEGA trajectory is six years. Arrival time is late 1995, ten years after the original arrival date. 1989 - Galileo is finally launched from the Space Shuttle with the IUS. ___ ______ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Choose a job you love, and /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | you'll never have to work |_____|/ |_|/ |_____|/ | a day in your life. ------------------------------ Date: Thu, 14 Jan 93 16:19:58 GMT From: "John P. Mechalas" Subject: Galileo Stuck Ribs / Remote Manipulator? Newsgroups: sci.space,sci.astro,alt.sci.planetary In article <20999@ksr.com> jfw@ksr.com (John F. Woods) writes: >justin@nx30.mik.uky.edu (justin sullivan) writes: > >It is an unusual problem in that most failures of spacecraft are subtle things >ailing in the innards of the boxes. This is an assertion about STATISTICS, >not some kind of value judgement -- of the total failures of spacecraft >components, big mechanical things outside where they can be reached are a >small fraction of the list. Now, as to what went wrong with Galileo's antenna, >it wasn't an oversight of even one engineer, really -- it was the mechanical >damage caused by trucking Galileo across country several times due to missed >launch opportunities and the shutdown of the space program after Challenger. >The engineers didn't design the joints to withstand that much of that kind of >vibration because Galileo shouldn't have been subjected to it -- I'll bet they >didn't design the antenna to survive having someone whack it several times >with a 15 pound sledgehammer, either. This is very true...The joints weren't designed for such loads because those loads were not supposed to be there. Not only that, the joints were originally not even supposed to be there at all! The shuttle program forced Galileo to be launched from a shuttle instead from an unmanned rocket like it should have been. In fact, the original design called for a launch from a Titan-Centaur, but John Fletcher had imposed a "Shuttle-only" rule that said everything had to be launched from the space shuttle. With the destruction of the Challenger, so went the possibilities of putting a liquid-fuel booster on the Galileo (no one wanted it in the shuttle bays after Challenger), and the VEEGA trajectory eventually had to be designed. This forced the Galileo to fly near the sun, which in turn forced the engineers to develop a folding antenna to protect it from the sun's heat. Hence the joints, and hence the stuck ribs. Don't blame the engineers. If you read _Exploring Space_ by WIlliam E. Burrows, you'd be amazed at what the designers of Galileo had to put up with...it's amazing the program is still alive. -- John Mechalas "I'm not an actor, but mechalas@gn.ecn.purdue.edu I play one on TV." Aero Engineering, Purdue University #include disclaimer.h ------------------------------ Date: 14 Jan 93 17:30:50 GMT From: Gary Coffman Subject: Galileo Stuck Ribs / Remote Manipulator? Newsgroups: sci.space,sci.astro,alt.sci.planetary In article <1993Jan13.064524.13581@mr.med.ge.com> hinz@picard.med.ge.com (David Hinz (hinz@picard.med.ge.com)) writes: > >A co-worker of mine brought up an interesting question about the >service problems such as we are seeing with Galileo. How feasable >would it be to incorporate a robotic arm manipulator into these designs, >articulated so that it could reach everything on the probe/satellite? > >This could be done with, perhaps, a variety of tooling, an articulated arm, >and a track around the device so it could reach wherever it needs to go, >such as, for instance, a stuck antenna rib. > >Obviously, this would have a bit of weight to it, but I would think the cost >would be fairly reasonable compared to lost productivity & usability. If >you could just work the remote manipulator and fix the problem, that would >beat weeks/months of hammering or whatever. > >What besides weight & cost would prohibit this? How much use would something >like this get, and would it be worth it? Cost and primarily mass are the big stoppers, but secondarily the mechanical arm would be subject to the same kinds of failure mechanisms that plague the antenna. So adding an arm just multiplies the mechanical moving parts subject to failure. There's also the concern that the arm could break loose and damage something else on the satellite. Scientists would rather use the extra mass and money to add more scientific instruments and try to use zero defects construction and testing to *avoid* mechanical problems in the first place. Most of our probes have been successful in this regard. It's just unfortunate that zero defects inspections prior to launch didn't catch the loss of lubricant in this case. A squirt of Dri-slide at the Cape would have avoided this problem entirely. Gary -- Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary Destructive Testing Systems | we break it. | uunet!rsiatl!ke4zv!gary 534 Shannon Way | Guaranteed! | emory!kd4nc!ke4zv!gary Lawrenceville, GA 30244 | | emory!ke4zv!gary@gatech.edu ------------------------------ Date: Thu, 14 Jan 1993 19:01:06 GMT From: Henry Spencer Subject: Galileo Stuck Ribs / Remote Manipulator? Newsgroups: sci.space,sci.astro,alt.sci.planetary In article justin@nx30.mik.uky.edu (justin sullivan) writes: >One could always argue that it wasn't an unusual problem that caused >Galileo to have a crippled antenna, but an oversight of hoardes of fine >engineers. Nobody's perfect, but when you get so many superbrains together >and give them piles of money, they're expected to deliver a perfectly >functioning piece of hardware... The first time, with no realistic testing? Come now. That's exactly what is wrong with the current space program: costs naturally skyrocket when you have to be *sure* that everything works the first time. The world simply does not work that way. The question at hand is, is it worth the weight, complexity etc. of a robot arm just on the off-chance that it might be useful? The answer appears to be "no". -- "God willing... we shall return." | Henry Spencer @ U of Toronto Zoology -Gene Cernan, the Moon, Dec 1972 | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 14 Jan 93 22:20:36 GMT From: Ron Baalke Subject: Galileo Update - 01/14/93 Newsgroups: sci.space,sci.astro,alt.sci.planetary Forwarded from Neal Ausman, Galileo Mission Director GALILEO MISSION DIRECTOR STATUS REPORT POST-LAUNCH January 8 - 14, 1993 SPACECRAFT 1. On January 8, one 180 hammer pulse sequence was sent while the HGA (High Gain Antenna) motor temperature was at 45.0 degrees C. This hammer sequence utilized a pulse duration of 0.267 seconds with a 33.3 percent duty cycle (1.25 hertz). 2. On January 8, real-time commands were sent to reacquire celestial reference at the completion of the star scanner checkout. 3. On January 8, the Dual Drive Actuator (DDA-5) Turn C sequence memory load was uplinked to the spacecraft without incident. This sequence covers spacecraft activities from January 11, 1993 through January 13, 1993 and includes DDA hammer window opportunities throughout the period. 4. On January 9, Delayed Action Commands (DACs) were sent to turn the gyro heaters on January 11 for approximately one hour to ensure the gyro temperatures are above 5 degrees C (minimum 3-210 gyro operating limit) for the scheduled warming turn later in the day. 5. On January 11, prior to the execution of the warming turn, real-time commands were sent to update the system fault protection AACS-INIT-SLOT to the sun. This change will cause the spacecraft to point towards the sun in the event of an AACS (Attitude and Articulation Control Subsystem) Power On Reset (POR). 6. On January 11, as part of the DDA-5 Turn C sequence activities, the warming turn to a 45-degree off-sun attitude started at approximately 1941 UTC and completed at 1952 UTC. After turn completion, real-time commands were sent to modify the Retro-Propulsion Module (RPM) thermal safing response in the event of sequence termination. After approximately one hour at the warming attitude, hammering of the HGA motors commenced. Five 180 hammer pulse sequences were sent beginning at 2100 UTC and ending at 0111 UTC. The motor hammering sequences were executed with the HGA motor temperature at 42.8 degrees C. These hammer sequences utilized a pulse duration of 0.267 seconds with a 33.3 percent duty cycle (1.25 hertz). 7. On January 12, three 180 pulse hammer sequences were sent prior to the sun acquisition when the HGA motor temperature was at 45.0 degrees C. These hammer sequences utilized a pulse duration of 0.267 seconds with a 50 percent duty cycle (1.875 hertz). The sun acquisition to a 5-degree off-sun attitude began at approximately 2013 UTC and completed at 2043 UTC. Approximately one hour later, a series of seven 360 pulse hammer sequences were sent beginning at 2130 UTC and ending at 0439 UTC. These hammer sequences utilized two different hammer frequencies; one with a pulse duration of 0.267 seconds with a 33.3 percent duty cycle (1.25 hertz), and the other with a pulse duration of 0.267 seconds with a 50 percent duty cycle (1.875 hertz). These motor hammering sequences were executed with the HGA motor temperature at 38.4 degrees C, 34.0 degrees C, 27.6 degrees C, 25.5 degree C, 21.4 degrees C, 19.3 degrees C, and 15.2 degrees C. 8. On January 13, one 360 pulse hammer sequence was executed with the HGA motor temperature at 5.2 degrees C. Then real-time commands were sent to reacquire celestial reference and select Scan Type 6 for the collection of precise wobble data. The analysis of the wobble data is currently in progress. Real-time commands were then sent to update the System Fault Protection (SFP) AACS-INIT-SLOT to Earth in preparation for the DDA-5 Turn D sequence activities. 9. On January 13, the Dual Drive Actuator (DDA-5) Turn D sequence memory load was uplinked to the spacecraft without incident. This sequence covers spacecraft activities from January 14, 1993 to January 17, 1993 and includes DDA hammer window opportunities throughout the period. 10. On January 14, as part of the DDA-5 Turn D sequence activities, the warming turn to a 26-degree off-sun attitude started at approximately 2002 UTC and completed at 2017 UTC. After the turn completion, real-time commands were sent to modify the Retro-Propulsion (RPM) thermal safing response in the event of sequence termination. After approximately two hours at the warming attitude, hammering of the HGA motors commenced using the two different frequencies (1.25 hertz and 1.875 hertz). Seven 360 pulse hammer sequences are being sent beginning at 2200 UTC and are in progress at the time of this writing. Motor current profiles throughout this reporting period indicate minuscule ballscrew rotation on occasional, random pulses. There has been no substantial rotation since the major hammering on December 29, 1992. 11. The AC/DC bus imbalance measurements have not exhibited significant change (greater than 25 DN) throughout this period. The AC measurement reads 18DN (4.1 volts). The DC measurement reads 151DN (17.8 volts). These measurements are consistent with the model developed by the AC/DC special anomaly team. 12. The Spacecraft status as of January 14, 1993, is as follows: a) System Power Margin - 23 watts b) Spin Configuration - All-Spin c) Spin Rate/Sensor - 2.9rpm/Acquisition Sensor d) Spacecraft Attitude is approximately 26 degrees off-sun (leading) and 40 degrees off-earth (leading) e) Downlink telemetry rate/antenna- 1200bps(coded)/LGA-1 f) General Thermal Control - all temperatures within acceptable range g) RPM Tank Pressures - all within acceptable range h) Orbiter Science- Instruments powered on are the EUV, EPD, MAG, HIC, and DDS i) Probe/RRH - powered off, temperatures within acceptable range j) CMD Loss Timer Setting - 120 hours Time To Initiation - 120 hours UPLINK GENERATION/COMMAND REVIEW AND APPROVAL: 1. The Dual Drive Actuator (DDA-5) Part D sequence memory load was approved for transmission by the Project on January 12, 1993. This sequence covers High Gain Antenna (HGA) motor hammering activities from January 14, 1993 to January 17, 1993. As with previous hammering activities, individual sets of hammering commands will be approved as required prior to being uplinked to the spacecraft. 2. The EE-12 (Earth-Earth #12) Final Sequence and Command Generation products were approved by the Project on January 12, 1993. This sequence covers spacecraft activities from January 20, 1993 to January 23, 1993 and from February 8, 1993 to April 12, 1993. TRAJECTORY As of noon Thursday, January 14, 1993, the Galileo Spacecraft trajectory status was as follows: Distance from Earth 26,870,100 km (0.18 AU) Distance from Sun 162,207,200 km (1.09 AU) Heliocentric Speed 132,400 km per hour Distance from Jupiter 751,299,000 km Round Trip Light Time 3 minutes, 0 seconds SPECIAL TOPIC 1. As of January 14, 1993, a total of 45639 real-time commands have been transmitted to Galileo since Launch. Of these, 40586 were initiated in the sequence design process and 5053 initiated in the real-time command process. In the past week, 19773 real time commands were transmitted: 19769 were initiated in the sequence design process and 4 initiated in the real time command process. Major command activities included commands to hammer the HGA motors, reacquire celestial reference, uplink DDA-5C sequence memory load, turn the gyro heaters on, update system fault protection, modify RPM thermal safing response, select Scan Type 6, and uplink DDA-5D sequence memory load. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Choose a job you love, and /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | you'll never have to work |_____|/ |_|/ |_____|/ | a day in your life. ------------------------------ Date: 14 Jan 93 19:04:53 GMT From: "Allen W. Sherzer" Subject: Phone number to save Goldin Newsgroups: sci.space,talk.politics.space If you want to keep the process of reform at NASA going, please call Clinton's transition office and ask them to keep Goldin on as NASA administrator. The phone number is: (202) 973-2600. You can also write at: President Bill Clinton PO Box 615 Little Rock, AR 72203 Some have asked if the address is still good, it is. I also would recommend that you NOT send email since will be the lease effective. Allen -- +---------------------------------------------------------------------------+ | Allen W. Sherzer | "A great man is one who does nothing but leaves | | aws@iti.org | nothing undone" | +----------------------100 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: 12 Jan 93 20:59:35 GMT From: Dani Eder Subject: Saving an overweight SSTO.... Newsgroups: sci.space gnb@baby.bby.com.au (Gregory N. Bond) writes: >Suppose DC-X works more-or-less as planned, and they go ahead and >attempt to build a DC-Y/DC-1. And suppose the pollyannas are right >and it bloats and the dry mass goes up. If you are trying to deliver cargo (not necessarily people) at the lowest cost per kg, then the solution is to fly the DC-1 sub-orbital (to about 0.7 of orbital velocity) and kick out the payload with a solid kick motor attached. The numbers go like this: Working DC-1: Delta V to orbit including drag and g-losses: 9144 m/s Specific impulse = 440 s Dry weight of cryo stage = 10% of liftoff mass. Mass remaining after engine burn = 12% of liftoff mass Net payload = 2% of liftoff mass Overweight DC-1: If we increase the dry weight to 12% of liftoff mass, then the payload goes to zero. DC-1 Used as Single-Stage-to-70% of orbit. 70% of orbital delta V = 6400 m/s Mass remaining after engine burn = 22.7% of liftoff mass Cryo stage = 12% of liftoff mass Net remaining for solid kick motor + payload = 10.7% 30% of delta-V = 2744 m/s Solid motor specific impulse = 270 sec. Mass remaining after solid motor burn = 3.8% of liftoff mass Solid motor inert weight = 17.5% of solid propellant weight = 1.2% Net payload = 2.6% So, by adding the solid kick motor, we can more than recover the lost payload due to an overweight SSTO. Is it cost effective? Well, solid motors range from $75/kg for strap-ons to $500/kg for apogee motors used with communications satellites. Since we need about 3 kg of solid motor for each kg of payload, we are adding $225 to $1500 per kg to the cost to orbit. If the DC-1 stage were providing $500/kg boost at a 2% payload fraction, then we have $385/kg at a 2.6% payload fraction. So the combined launch cost would be in the range of $610/kg to $1885/kg. If the DC-1 stage experienced a 100% operating cost overrun, then we are at $995 - $2270 per kg. All these numbers can be compared to the current costs of $10,000/kg for satellite launch. So, even if the DC-1 development is 20% overweight and 100% over cost, it still is a factor of 5-10 cheaper than today's systems. It can do this by making the lower stage efficient and re-useable. It lowers the expended hardware per kg payload delivered to orbit from 4kg/kg (today's expendables) to 0.46 (the solid motor inert weight/payload weight) Dani Eder -- Dani Eder/Meridian Investment Company/(205)464-2697(w)/232-7467(h)/ Rt.1, Box 188-2, Athens AL 35611/Location: 34deg 37' N 86deg 43' W +100m alt. ------------------------------ Date: Thu, 14 Jan 1993 16:41:45 MST From: "Richard Schroeppel" Subject: SNC meteorites "James N. Head" has presented a summary of the evidence for believing that SNC meteorites are from Mars. This has some interesting implications for the existence of life on nearby planets: The Earth has probably exchanged surface matter with many bodies in the solar system. We are more likely to have received contributions from Mars, Io, Europa, Titan, Triton, etc.; but we might someday find meteorites on Mars that were blasted from the Earth. These might contain Earth fossils or micro-organisms or bio-chemicals. Or perhaps life on Earth was seeded from a thriving culture of protozoans on Ganymede :-). Rich Schroeppel rcs@cs.arizona.edu ------------------------------ Date: 13 Jan 93 19:41:39 GMT From: Bruce Watson Subject: Subjective Safety Measure(Re: man-rating) Newsgroups: sci.space,sci.aeronautics In article <1inau4INN524@mirror.digex.com| prb@access.digex.com (Pat) writes: |In article <1993Jan8.145918.3604@newsgate.sps.mot.com| turner@ssdt-tempe.sps.mot.com (Robert Turner) writes: || ||Isn't the elevator considered the safest mode of transportation meeting both the ||"if I get in, I get out" and "deaths per passenger mile". || | |a |Ah, this guy has never heard of elevator accidents? |While kinda uncommon they do occur. mostly due to improper door opening. Contrary to all the movies we've seen, there has never been an elevator fatality since Otis designed the safety features of the modern elevator in the late 19th century. -- Bruce Watson (wats@scicom) Bulletin 629-49 Item 6700 Extract 75,131 ------------------------------ Date: Thu, 14 Jan 1993 19:00:01 GMT From: Herman Rubin Subject: Supporting private space activities Newsgroups: sci.space In article henry@zoo.toronto.edu (Henry Spencer) writes: >In article <1993Jan10.151446.20003@r-node.pci.on.ca> marc@r-node.pci.on.ca (Marc G Fournier) writes: >>I'm confused. Is the US the only country that has the 'environment' to >>set up a launch site? My understanding about why it is all done from Florida >>is that it has to do with weather and easy of escaping Earth's atmosphere (lower >>gravity?) >You want to be as close to the equator as possible to take maximum advantage >of Earth's spin. If you're launching rockets that fall apart (e.g. they >have multiple stages), you want to have lots of water downrange. Those were >the only really technical reasons for Florida (the weather is lousy). The effect of launching east from the equator is to reduce the velocity needed by about 6%. This does not look like much, but the reduction in energy, ignoring the mass effects of rockets, is double this, and the mass of fuel and oxidized needed would be reduced somewhat more. This makes the Israeli launching to the west even more impressive; the effects are in the opposite direction. Now the effect at Cape Canaveral is about 90% of the equatorial effect, and that at the Russian launching site only about 70%. The differences are more important when it is desired to launch a satellite in an equatorial orbit, as the energy needed to correct the orientation of the orbit is rather large. Increasing the inclination of the orbit is more flexible than decreasing it. Here the European site in Guyana wins out. So in general, the launch site should be near the equator, with a clear shot in an eastward direction. The Russian launching goes over a vast tract of uninhabited land instead of water. The location of the US polar launching site at Vandenburg is so that a launching to the south avoids land for thousands of miles. >There's no fundamental problem with putting a launch site elsewhere -- >the Aussies are trying to do one at Cape York -- but the US is the single >biggest customer and is a prime supplier of bits and pieces even for >other people's hardware. The US is also just about the only country >that has a large space industry which is not completely a creature of >the government. Cape York is quite close to the equator. Also, the Australian site for the launching of short-range rockets, Woomera, uses the uninhabited land approach. -- Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399 Phone: (317)494-6054 hrubin@snap.stat.purdue.edu (Internet, bitnet) {purdue,pur-ee}!snap.stat!hrubin(UUCP) ------------------------------ Date: Thu, 14 Jan 1993 15:43:42 GMT From: Brad Whitehurst Subject: TPS Systems Newsgroups: sci.space In article <61310bf1@ofa123.fidonet.org> Wales.Larrison@ofa123.fidonet.org writes: > I put this data together a while ago, and thought it might be >useful to share with the net on this related subject. > There are 7 basic types of thermal protection materials - here is >a summary of them >TYPE EXAMPLES MAXTEMP(F) ADVANTAGES DISADVANTAGES >Metallic Columbium 2500 Durable Very Costly >Refractories Tungsten Reusable Very Heavy > Hard to manuf Also, they go away in oxidizing environments, quite violently at times, unless they have protective platings such as platinum. >Superalloys Inconel 617 2000 Durable Limited Temp > Haynes 188 1850 Reusable capability > Rene 41 1600 Expensive Depending on how much load they have to carry, some of the older superalloys can be used, and are almost cheap. Good oxidation resistance, but hot strength not as good as the newer ones. >Non-metal Carbon/Carbon 3000 Reusable Very Costly >Refractories Silcon Carbide 2700 Heavy > Brittle Solid, alpha-SiC is a strong, structural ceramic, though we have had some which exuded glass bubbles at high temp. May have been a bad batch. Also, SiC foams are now commercially available, very light, good to 2700 F in air, suitable for structural sandwiching. Other interesting ceramics: SiC whisker reinforced alumina, zirconia, silicon nitride, and all kinds of aluminas. >Ceramic Tiles FRCI 2400 Light Wt Durability > Reusable > Easy to Make > Fibrous zirconia ceramics can be used in air above 4000 F, but the insulating varieties (commercial) are quite fragile. I'd expect you'll see some sort of compound hull, with a tough skin, backed with insulation (cooled, maybe?) and a strong inner hull. Just at a guess, clever designer could come up with a hull using available commercial materials, although it might be heavier than the latest "unobtainium". Just my $.02 -- Brad Whitehurst | Aerospace Research Lab rbw3q@Virginia.EDU | We like it hot...and fast. ------------------------------ Date: 13 Jan 93 21:54:00 GMT From: Mike Ditto Subject: youth astronomy groups Newsgroups: sci.space * Original: FROM: Mike Ditto * Original: TO: All * Original: AREA: ** Astronomy ** * Forwarded by Mike Ditto * Forwarded Using QuickBBS 2.76 * Forwarded at 14:59 on 13-Jan-93 Hello, I am an assistant mentor for the International Association for astronomical Studies. We are located in Denver, CO and we are interested in forming international chapters at other research facilities around the US and abroad. If anyone is interested, please send email to mike.ditto@f104.n240.z1.fidonet.org or on Fido-Net 1:104/240. We are a star chapter of the Explorers program of the Boy Scouts of America, and we have done such projects as putting research packages on the space shuttle, proposing time on Hubble Space Telescope, and doing internationally renowned star programs as the Boulder Valley Planetarium and the Gates Planetarium. Pleas respond by email, or on this echo. Thanks!!! Mike Ditto -- Mike Ditto - via ParaNet node 1:104/422 UUCP: !scicom!paranet!User_Name INTERNET: Mike.Ditto@p0.f240.n104.z1.FIDONET.ORG ------------------------------ End of Space Digest Volume 16 : Issue 049 ------------------------------