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 ; Sun, 14 Jan 90 01:36:56 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sun, 14 Jan 90 01:36:35 -0500 (EST) Subject: SPACE Digest V10 #425 SPACE Digest Volume 10 : Issue 425 Today's Topics: Re: Nuclear Reactors in Space Re: Airlocks & Life support Galileo Update - 01/12/90 Any NASA COBE Personnel Out There? Re: Nuclear Reactors in Space ---------------------------------------------------------------------- Date: 13 Jan 90 23:01:25 GMT From: microsoft!davidle@uunet.uu.net (David LEVINE) Subject: Re: Nuclear Reactors in Space In article <1990Jan8.151837.6831@utzoo.uucp> kcarroll@utzoo.uucp # (Kieran A. Carroll) writes: #Ha! You've gotta be kidding. RTG's are NOOOKLIER, #made of ATOMS just like ATOMIC BOMBS. Isn't that NOOOKULER? ^ # #It's an unfortunate fact of life that there are a number of people out #there who react to any mention of the "N-word" with mindless, #unreasoning, superstitious dread, and no arguments, no matter how well #reasoned and firmly based in fact, will sway them in the slightest. # #(I have heard some reasoned, though, in my opinion, quite mistaken #arguments against nuclear power. Tim's wild-eyed paraoid rantings #against anything containing the "N-word" are not among them.) Its been this way for a long time and there are good reasons for the paranoia. Back in 1950 when the US was sitting on top of the world, atomic power was going to save mankind. A pamphlet entitled "Operation Atomic Vision" promised that atomic power would solve all of our problems -- there would be no hunger and no disease and everybody would be happy. This was the official word from the Atomic Energy Commision. Well, it didn't happen. In fact, the whole thing has been one big mess. We jumped in too far too fast without really understanding the dangers. In all sorts of small ways, the fledgling commercial nuclear industry was subsidized by the government and was not competitive on its own. The construction and operation of the plants has often been done with abysmal standards. An "N" plant is reasonably safe if built and operated to spec and a potential disaster if not. It has not been treated with the seriousness it deserves. Of course, the study of nuclear physics has provided many other practical improvements to the quality of our life besides nuclear energy. The defense agencies were worse. They did not protect the public or their own personel from the hazards of above ground testing. The mistakes and cost cutting measures in the nuclear facilites has resulted in the horrible mess we see today trying to clean up old sites and get rid of waste products. For YEARS (and perhaps still today), when ordinary citizans questioned what was going on, they were rebuffed, lied to, or ignored. Sometimes, they were harrassed by public and private entities whose toes they stepped on. It was not possible to put a leash on the companies that built and operated the plants and especially not on the military. Slowly, the public became aware of the dangers and started providing support for the few individuals who had earlier been fighting alone. Three Mile Island greatly increased the momentum. The huge backlash has contributed to the construction of new plants grinding to a halt. This new grass roots army of anti-nuclear activists usually fits the bill of reacting to the "N-word" with "mindless, unreasoning, superstitious dread." These people are not scientists (not even computer scientists #:->). However, they know they have been lied to. I used to love looking at anti-nuclear literature and poking huge holes in it, both techinical and historical. The biggest anti-nuclear organizer on campus admitted that much of the literature he passed around (he got it from an umbrella organization) was bogus, but people believed it and supported the cause and that was the important thing. You don't get a mass movement by painting the problem in shades of grey, that is partly why (IMHO) you see so many anti-nuclear fanatics. This has basically killed the future of the nuclear industry and has led to things like the recent RTG incident. "But the *scientist* say that the RTGs are safe to launch" you say. Those same scientists also said that above ground nuclear tests were OK. There is a big credibility gap here. By the way, I worked on Galileo for six year while at JPL. I am quite glad it went up, thank you. I'm just trying to justify the seeming insanity of the Christics and others. Someone suggested that their motivation was simply to disrupt large organizations. This is a bit hard to swallow. John Q. Public is not an expert in risk analysis or statistics. The Galileo launch *was* a quantifiable risk to the residents of southern Florida. Many people just don't understand the comparison to other routine risks (like slipping in the shower or driving over a bridge which might collapse). DISCLAIMER: I think nuclear technology is great stuff. The commercial and military nuclear industries are another story entirely however. I would not want an N plant near my house, nor would I want a chemical plant or an IC fabrication facility. Yet my modern life is based on energy, chemicals and computers. Yes it is hypocritical. We must anticipate and pay for the *future* costs of our technology in order to safeguard everybody. It certainly will cost more now but will save magnificently over the long haul. Sorry, this does not really belong in sci.space, but space scientists must also understand the social implications of their work. We will see more RTG-like incidents in the future. We must treat those who question the safety of our pursuits seriously, sometimes they are right! I don't mean we should cater to them, but if you brush off one activist like a fly they will return in hoards. David Levine ===================================================== === The opinions expressed above are entirely mine == === The facts expressed above are probably wrong == ===================================================== ------------------------------ Date: 13 Jan 90 07:51:39 GMT From: att!watmath!watserv1!utgpu!utzoo!henry@ucbvax.Berkeley.EDU (Henry Spencer) Subject: Re: Airlocks & Life support In article <11704@csli.Stanford.EDU> jkl@csli.stanford.edu (John Kallen) writes: >I've often wondered what happens tro the air in the airlocks when >cosmonauts perform EVAs... On all US spacecraft, and I'm pretty sure on all Soviet ones, it's simply dumped. So far, the mass costs of doing something about it are too high to be worth it, given that EVAs are infrequent and air compressors are heavy. >... Is air sucked out of the airlock prior to the >opening of the outer hatch before EVA exit, or is it dumped in space when >the hatch opens? It's vented through a valve before opening the hatch. A reasonable fraction of one atmosphere exerts a good many thousands of pounds of pressure on a normal-sized hatch; one does not want to just unlatch something holding back that much force. Some of the hatches are designed to exploit that pressure, in fact, to give a better seal: if the hatch opens inward, air inside holds the hatch very firmly against the gaskets. (This is also a minor safety feature, in that the hatch cannot be opened by accident with air inside.) As I recall, both hatches on the shuttle airlock open inward. >... Is the >evacuation of the airlock the activity that makes EVAs so lengthy timewise? No. The EVAs themselves are lengthy because work in free fall while wearing a clumsy suit is difficult. Preparation for them is lengthy because keeping the suits' clumsiness to a minimum requires running with an absolute minimum of pressure in them. To do that, one has to run the suits on something approaching pure oxygen. For various reasons, current preference is to run spacecraft cabins at near one atmosphere and use a near-normal mix of oxygen and nitrogen. The transition from a high-pressure atmosphere rich in nitrogen to a low-pressure one requires lengthy pre-breathing of pure oxygen to get the nitrogen out of the astronauts' bodies. (The alternative is a strong possibility of decompression sickness, "the bends", potentially crippling or fatal, as that nitrogen comes out of solution as bubbles.) There has been a lot of talk about high-pressure suits, but getting adequate joint flexibility is difficult. >... how often does MIR need to be "refueled" >with air when it is manned? How long can they survive only by recycling with >LiOH(I think?) before they absolutely need more oxygen... LiOH takes CO2 out of the air, but it does not restore oxygen. A constant trickle of oxygen is required. Without it, survival time is determined by how much oxygen there is in the air filling Mir... which is not a lot, sizable though Mir is. -- 1972: Saturn V #15 flight-ready| Henry Spencer at U of Toronto Zoology 1990: birds nesting in engines | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 13 Jan 90 18:27:55 GMT From: zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@tut.cis.ohio-state.edu (Ron Baalke) Subject: Galileo Update - 01/12/90 Galileo Mission Status Report January 12, 1990 As of Friday, January 12, 1990, the Galileo Spacecraft is 16,229,650 miles from the Earth, 11,067,810 miles from Venus and was travelling at a Heliocentric velocity of 73,900 miles per hour. Round trip light time is 2 minute, 52 seconds. Two SITURNS to the Sun were successfully performed without incident on January 9 and January 12. A total of 1151 real-time commands have been transmitted to Galileo. Of these, 845 have been pre-planned in the sequence design and 306 were not. In the past week a total of 61 real-time commands were transmitted; 1 was pre-planned and 60 were not. To date a total of 120 contingency commands have been generated and 4 contingency commands have been transmitted; none were transmitted this week. This weeks totals contain 10 commands from EV-05. The EV-5 sequence memory load was successfully loaded into the CDS on January 6. As part of the load process, elements 212 and 213 of the load were not received initially and had to be retransmitted. Preliminary analysis discovered the CDS had experience eight lock change indications as detected by the HCD. Investigation into the cause of these lock changes is in process by systems, CDS and telecom personnel. The EV-5 sequence went into operation, as planned, on January 8. The events in EV-5 will cover spacecraft activities through February 5. As part of the investigation into the EUV microprocessor "stop" anomaly, which occurred during the science checkout activity, the EUV memory was loaded and readout twice on January 6. Subsequent to memory verification, the EUV microprocessor was started on January 8. Memory readouts were performed prior to and after the microprocessor start and operation of the EUV was nominal. The exact cause of the anomaly which stopped the microprocessor has not been determined. However, it is unlikely based on this data that a "hard" failure has occurred in a 6504 memory chip. The sixth RPM thruster "flushing" activity was successfully completed on January 8. Only the Z, L and S thrusters were "flushed". Since the P thrusters are used for periodic SITURNS 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 50 degree C to 100 degree C, well within the predicted limits. A command was sent on January 9 to turn off the NIMS shield heater (26W) for about 3 hours to permit the NIMS to collect Focal Plane Assembly Temperature data in an attempt to ascertain whether the NIMS radiator cover was deployed or not. After 3 hours, the heater was turned on again consistent with RPM thermal/pressure constraints. Data collected by the NIMS during the time the heater was off indicated the cover was either already deployed or that it deployed as a result of the cool down possibly relaxing any mechanical binding which may have existed. The delta DOR function in the RFS was activated for the first time on January 9. Delta DOR represents a navigation new data source in addition to doppler and ranging data already available. Demonstration of the S-Band delta DOR is being performed now while the RF link performance is still "strong" and to allow sufficient time to understand and evaluate the DOR data and its actual advantages to navigation. The S-Band delta DOR consists on modulating the downlink carrier with a 3.82 MHZ sine wave. It is pointed out that during the short periods that delta DOR is active, the telemetry data stream from the Telemetry Modulation Unit is interrupted and no spacecraft data is transmitted. Estimates indicate that a 2-3 kg fuel savings post-Earth flyby is possible based on delta DOR data. The delta DOR data analysis is in process and is expected to be available around January 22. The AC and DC bus imbalance measurements continued to fluctuate. On January 9, the AC imbalance reached 48.4 volts indicative of a near "hard" short to spacecraft chassis. The measurement remained stable for several hours and subsequently dropped to about 40 volts. During this time while the AC measurement fluctuated upward, the DC imbalance measurement very slowly crept upward to 20.8 volts and remained stable (see Special Topic). UPLINK GENERATION/COMMAND REVIEW AND APPROVAL The Project reviewed and approved the EV-6 Profile Design on January 12. EV-6 contains the Venus Encounter Sequence which starts one day before the Venus closest approach and eight days later. Venus science data will be recorded on the Data Management Subsystem (DMS). The equivalent of four images will be returned using a technique incremental playback involving transfer of small portions of recorded science data to the CDS then reading out CDS memory. This process will be done while the telecommunications leak is capable of supporting the 1200bps downlink. Sequence and command generation starts on January 15. The Project approved the VE-1 and VE-2 Cruise Plans on January 11. These sequences will cover spacecraft activities from February 19 to March 26 and from March 26 to April 23, respectively. SPECIAL TOPIC The fourth Tiger Team status report to the Project was held on January 10. Three major topics were covered. PPS reported that after careful review of the inverter physical layout by LORAL engineers, it was concluded that the physical spacings between AC and DC functions is large (approximately 30-100 mils) and that the "touching" of AC and DC power lines is very unlikely. PPS will continue its effort to find any spacecraft event correlations with the observed imbalance measurements. Review of the Spin Bearing Assembly slip ring physical layout revealed that there are several locations within the four modules where AC or DC or grounds are adjacent. To determine the feasibility of a slip ring leakage path, an intensive effort was initiated two weeks ago to develop a model. The preliminary work to date indicates that it may be possible for small particles of silver (less than 30 microns) to move under the influence of electrostatic forces (causes by electric field gradients between adjacent slip rings) and deposit across the barrier thereby creating a leakage path. Work will continue on this model to refine the electrodynamic forces and to generate two dimensional AC and DC electrostatic field diagrams. Work has continued to determine the feasibility whether electrical noise may be corrupting PPS sensor readings. Noise coupling models have been developed and some stray current paths identified. Since stray currents may produce erroneous readings in the PPS sensors, a careful review of all spacecraft electrical loads is in process. Noise currents on the orbiter of a few milliamperes may be sufficient to create anomalous readings. The Project conducted a detailed review of its readiness and risk for Venus Science. Assessments were provided by the OET, Sequence and Navigation Teams of the Engineering Office; the Science Requirement and Ops Planning Team representing the Science and Mission Design Office, the Flight Control and Support Office and the Ground Systems Office. It was concluded that the Venus Science encounter can be executed, in general, without adverse risk to the spacecraft; the Flight Team is staffed and trained though there is no margin in the development of the sequence. We are "GO" for Venus Science. 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: 12 Jan 90 15:32:47 GMT From: hpfcso!hplisa!hpislx!gvg@hplabs.hpl.hp.com (Greg Goebel) Subject: Any NASA COBE Personnel Out There? I was making notes from the recent SCIENTIFIC AMERICAN article on COBE when I looked through the "Instrument Parameters" table, under the entry "Spectral Resolution" for FIRAS: 0.2 cm^-1 I must've stared at that for five or ten minutes. Either that's a typo or I'm missing something. Any illumination out there? -- +----------------------------------------------------------------------------+ | Greg Goebel NET: gvg@hpislx | | Hewlett-Packard HP DESK: GREG GOEBEL / HP0900 / EM | | MSO Marketing PHONE: Telnet/303 679-3424 | | POB 301 / MS-CU312 / Loveland CO 80539 FAX: Telnet/303 679-5957 | +----------------------------------------------------------------------------+ ------------------------------ Date: 13 Jan 90 23:09:27 GMT From: microsoft!davidle@uunet.uu.net (David LEVINE) Subject: Re: Nuclear Reactors in Space >something useful well past this point. And just how do you power the >proposed TAU (Thousand Astronomical Unit) project? One configuration I (briefly) worked on used an SP-100 (that space qualified reactor we've been talking about). >The engineers at NASA might be a bit slothful, but they aren't entirely dim, Thanks for the qualifier. >unlike the Sun at the majority of planets. Which planets? Which sun? 8-#:-) David Levine ===================================================== === The opinions expressed above are entirely mine == === The facts expressed above are probably wrong == ===================================================== ------------------------------ End of SPACE Digest V10 #425 *******************