From ota Sun May 29 03:37:50 1988 Received: by angband.s1.gov id AA00252; Sun, 29 May 88 03:37:11 PDT id AA00252; Sun, 29 May 88 03:37:11 PDT Date: Sun, 29 May 88 03:37:11 PDT From: Ted Anderson Message-Id: <8805291037.AA00252@angband.s1.gov> To: Space@angband.s1.gov Reply-To: Space@angband.s1.gov Subject: SPACE Digest V8 #237 SPACE Digest Volume 8 : Issue 237 Today's Topics: Yet again the advantages of Mir over Skylab Re: Yet again the advantages of Mir over Skylab Re: Yet again the advantages of Mir over Skylab Re: Yet again the advantages of Mir over Skylab Re: Yet again the advantages of Mir over Skylab Mir predictions ---------------------------------------------------------------------- Date: Mon, 16 May 88 18:41:23 EDT From: Glenn Chapman Subject: Yet again the advantages of Mir over Skylab In Space v8, 222 Karl Wagenfehr repeats on of the often quoted myths of our space age, as have many others in recent days on the net: > ...... Skylab was sent up, and manned. It was no big deal, really. > Yeah, a manned space station; big deal. I would like to remind you > that Skylab was a lot bigger than Mir (how much I don't recall off > hand). This slow turtle approach being better is just a load of bunk. > We *had* a space station. A much better space station than that which > we envy the soviets today. Permanent man presense in space is not > such a big deal. It just requires persistence and money. I will > concede on that point: the soviets are superior in that they stuck to > their space program. Had the united states shown just half the > persistance of the soviets, I don't think we'd be envying them > anything right now. We were where they are now *15 years ago*! Just > we got bored, and stopped supporting Space. This persistant belief in the Skylab myth has gotten to be rather disturbing. I have started to have sympathy for Jerry Pournelle's comment that he wished Skylab had never flown, then we would not be trying to convince ourselves that we had done it all decades before. For those that want a true comparison I have substantial revised a breakdown of advantages and disadvantages of both I posted more than a year ago (adding several more points, all to Mir's benifit). In the past year the advantages of Mir have increased by its operation and the strong points for Skylab decreased. Read it and weep. Let us compare the advantages of the two stations. As a reminder Soviet stations have come in 3 generations: Their 1st containing Salyut 1 (Apr - Oct '71), Salyut 2/Cosmos 557 (1973 - failures that were never manned), Salyut 3 (Jun '74 - Jan '75), Salyut 4 ( Dec '74 - Feb '77), and Salyut 5 (Jun '76 - Aug '77); Second generation with Salyut 6 (Sept '77 - Jul '82) and Salyut 7 (Apr '82 - present); Third generation Mir (Feb '86 - present). Skylab was launched in May '73, the last crew left in Feb '74, and decayed in July '79. Where Skylab is currently ahead (1) Skylab had a final mass of 77 Tonnes (with 2200 lbs per metric Tonne), and the combined cluster Skylab + the Apollo Command Service Module is listed as 90 Tonnes. The current Soviet Mir/Kvant station has a 33 Tonne mass as launched, while the combined Mir + Soyuz + Progress cluster is 47 Tonnes. However there are some caveats here. The mass for Skylab includes some 8 Tonnes of food, water, air, and fuel for that were required for the entire mission. By comparison the Progress freighters bring that up to Mir. There have been 12 Progresses to Mir, each bring some 2.5 Tonnes of cargo/fuel/water for a total of 30 Tonnes added to Mir, plus about 1.3 Tonne more brought up by the Soyuz's with the Cosmonauts. Of course some of that has been discarded as waste. However the combined station mass is probably 60 Tonnes now (15 Tonnes in the Progess + Soyuz carriers). In Skylab all the garbage was kept in a tank at the "bottom" of the station, so it maintained that mass (plus the astronauts took up about 200 Kg per trip). Also there is one other problem with Skylab's mass - all the books I have found give the value as launched, with both solar wings, but one was lost before orbit. That probably reduces the mass by 2-3 tonnes. Note that the command/service modules added 13 tonnes to Skylab, but little in useful capacity. By comparison the Soyuz solar panels feed the station about 1 KW of power while the Progress's rocket engines are used to adjust the station's orbit. (2) Working volume for the Skylab complex was 357 cubic meters. The current Mir/Kvant combination is about 160 cubic meters. From a psychological point of view that was definitely better for Skylab crews (each crewman had about 48% more volume). However much of that volume had little useful value, and pictures of Skylab show that its walls are not completely covered with equipment, the way the Mir's is. Also it should be noted that the new NASA station has a volume per crew that is about the same as Mir's, or perhaps a bit smaller. Where Mir & other Soviet stations are ahead (1) All Russian stations, right from Salyut 1 in 1971, have had orbital manoeuvring rockets that use Hydrazine (UMHD) fuel and Nitrogen Tetroxide oxidzer. This allows the Soviets to do extensive orbital changes with their systems. For example this lets them lower the orbit to meet supply ships and Soyuz's (usually by letting the orbit decay a bit so this does not cost them fuel), thus allowing those systems to bring up more material. Then they raise the orbit to keep the space station up there. Thus with this the orbital working lifetime of the second generation Soviet Stations was about 5 years, and none of their working stations have decayed from orbit (Salyut 2 and Comos 557 were two early stations that were damaged on orbit, never manned, and allowed to decay - the others were brought down by command from the ground). Skylab had only a small Nitrogen gas system with 0.8 Tonnes of gas. As a result only small changes could be made to Skylab's orbit. As we all know it reentered in 1979 due to this. (2) All second generation Russian space stations had 2 docking ports, while Mir has 6. Skylab had two, one axial and one on the side (the side one was never used and was mostly ment for a rescue if needed). The Soviet stations have 2 axial ports (Mir has 4 additional side ports). Axial ports are easier to dock to. Having several ports has many implications. First one crew could be docked to the station while a second crew came up for a visit or to replace the first crew. Without multiple ports crew exchanges, where all or part of cosmonauts releaved those currently manning the station, would be extremely difficult. Secondly this allows cargo to be brought to the station while a crew is on board (see point 3 also). Thirdly the extra ports can be used to expand the current station. Salyut 6 & 7 had one extra module added to them at a time (Salyut 7 had this done twice to it). Mir currently has one expansion module added (Kvant) but is designed to take at least 5 modules, plus a Soyuz and one other vehicle. Skylab was a one shot deal - no plans for expansion. Indeed the TRS rocket system that was being designed to attached Skylab from the shuttle had two plans for it - one to boost it to a higher orbit, the other to send it to reentry in the ocean areas. (3) The Russians developed an automatic docking system back on Salyut 6 (1977) which allows unmanned cargo craft like Progress, or large "star" modules (20 Tonne expansion units) to attach to the system. Since the cargo craft are unmanned they do not need heat shields and can carry more material. This naturely cuts the effort and cost in supplying the station and makes their long duration missions possible. Indeed Skylab was launched with 140 days worth of supplies on board. The Apollo capsule could only bring a few weeks worth up with them. The plans for a fourth mission to Skylab called for only a 30 day stay, due to supply problems. Again the Soviet autodocking system means the expansion modules need no crew, making their design and testing simpler. Skylab had nothing like that developed for it. Sure we could supply a station from the shuttle and expand it that way, but not without developing equipment which we do not have. The Russians have had automatic systems doing this for 11 YEARS! (4) All Soviet stations since Salyut 6 (1977) have been refuelable via Progress tanker craft. To date (May 16, 1988) 36 Progress tankers have flown, 12 to each of the three last stations, all successfully as far can be told. In addition their to the fuel the station's water and air was resupplied from the same vehicles via similar lines and transfer systems from the Progress to the station. Fuel supplied to Salyut 6 or 7 was about 5.3 Tonnes each, to Mir I estimate the same so far. Since UMHD/Nitrogen Tetroxide has a much higher specific impulse than Nitrogen gas that gives them much more boost capability. Water and air totaled about 11 Tonnes each for the Salyuts. Mir, even this early in its cycle has been supplied with the same amount. The first generation Russian stations where like Skylab - throw away cans. You used them until they ran out of supplies and then tossed them. Second generation and the new Mir can be used as long as you need or want them. (5) Since Salyut 6 (1977) Russian stations have had a working partial water recovery system. The older versions recovered about 50% of the water (Mir may be better from some comments). Since water a human uses about 4.5 Kg of water a day, but only 0.8 Kg of oxygen and 0.7 Kg of food (dry) this is the most important thing to recover first. Sure better systems have been built on earth, but nothing else has flown in zero g. This is vital for a real station or long voyages to the planets. Nothing like this on Skylab. There also appears to be tests of newer Carbon Dioxide removal and oxygen recovery systems on Mir, though it is not certain they have replace the old absorption filter system as of yet. (6) Mir has a data/communications relay system through their TDRS system (the Eastern Data Relay Network). While the shuttle has this Skylab did not. They have had some some problems with this at the satellite end, but the station capability is still there. (7) Mir's solar power system puts out twice the power, 12-14 KW, of Skylab's. People think Skylab was better because some books talk about the total possible power there as 23 KW. However Skylab's max deliverable power was only 8.5 KW before they lost the solar wing, and about 6-7 after the repairs. The difference comes from looking at the area of the solar cells and their efficiency, while ignoring shadowing effects, losses in the power cables, and other power system losses which reduce the output to 33% of the max value. Mir's values are for the actual system output power. 2.5 KW of Mir's comes from solar panels added to the station in a space walk last year. (8) The Russians have put a lot of work into making the crew psychologically comfortable on their stations, from the experience they have gotten from their long voyages. They send up gifts from home and fresh fruits on the Progress tankers, have a TV studio set up to set up weekly video conversations with friends and families. Color schemes on the station are for maximum comfort etc. Again we can do this, but they have 11 years of experience of what people miss most in orbit (they get great pleasure in tending the small gardens in the space station for example). (9) Mir has currently 547 days of occupation (1136 man-days) in its 815 current existance and has been permanently manned since Feb. 9, 1987. Skylab had only 171 days occupation (513 man-days) of 235 operational days. Furthermore Mir is still behind Salyut 6 which had 669 days of occupancy, and Salyut 7 which had 712 days. Skylab was not in good shape at the end - one gyro had failed another of the 3 was showing signs of failing, which was part of the decision to bring the last crew home when they did. Salyut 7 by comparison is still in orbit after 6 years, still under control and held a crew for 50 days just last year. (10) Almost certainly the computers on Mir are far in advance of those on Skylab. Skylab's were of 1972 vintage, and the Soviets are probably 5 years behind us in computers, 10 years at the outside (there are several DOD reports on this). Hence that puts Mir's computers of the equivalent of 1976 to 1980 vintage here. Where Mir will probably exceed Skylab in the near future: (1) The Mir complex will exceed the combined Skylab complex mass when two more 20 Tonne "star" modules are added, probably by the end of this year. (2) The Skylab's working volume record will fall if the Soviets add the announced 4 "star" expansion modules that Mir was designed to take. This will take several years to occur. All of this was only hardware. It ignores the experience the Soviets have gained: 11 years of materials science experiments, zero g life science work, the knowledge of how space station system work in orbit, how joined structures behave in orbit over years of time. If you think that the Russians having more than twice the number of man hours of space experience means nothing then you must argue that space is different in that reguard than any activity on here earth - experience counts when things must be done well or quickly. Right now the US is not even on the top 10 list of space flight durations. Look it, Skylab was a wonderful house in space, but we have done nothing real in space stations since. Saying that Skylab is better than Mir is like arguing that the Titanic ocean liner is better than a flying 747 aircraft. Sure the ocean liner was more comfortable and larger, but it was older technology, goes less places, is generally less flexible than the 747, and no longer exists. We have no working space shuttle, and a space station which will not be operating for another decade. To say that there is no problem because we are still ahead of the Russians on the basis of Skylab is to deny the reality of the world. It makes people feel good in this country but it does not help solve our problems. As the saying goes "it is not the things that you do not know that hurt you, but rather those that you do "know" that are not true". Glenn Chapman MIT Lincoln Lab ------------------------------ Date: 18 May 88 15:56:49 GMT From: attcan!utzoo!henry@uunet.uu.net (Henry Spencer) Subject: Re: Yet again the advantages of Mir over Skylab > Skylab was a one shot deal - no plans for expansion. Well, not quite true -- there were *plans* for expansion, back when Skylab had five docking ports. It's just that nothing was ever done about them. (And as a result, it didn't need five docking ports any more...) -- NASA is to spaceflight as | Henry Spencer @ U of Toronto Zoology the Post Office is to mail. | {ihnp4,decvax,uunet!mnetor}!utzoo!henry ------------------------------ Date: 18 May 88 16:43:46 GMT From: thumper!karn@faline.bellcore.com (Phil R. Karn) Subject: Re: Yet again the advantages of Mir over Skylab Glenn Chapman's detailed comparison of Skylab and Mir is interesting, but especially so because it omitted any mention of what each accomplished in the way of practical applications (including meaningful, PUBLISHED scientific research). Just to keep things fair, we ought to compare each to the contributions of unmanned spacecraft while we're at it. I suppose as an engineer I really ought to care about "whose is bigger" and who is currently ahead in our hi-tech flagpole-sitting contest, but as a taxpayer I want to know how effectively my money is being spent on accomplishing the goals originally used to justify these expenditures in the first place. Don't forget that these programs are means to an end, not ends in themselves. Phil ------------------------------ Date: 19 May 88 17:09:11 GMT From: ulysses!terminus!rolls!mtuxo!mtgzy!ecl@ucbvax.berkeley.edu (Evelyn C. Leeper) Subject: Re: Yet again the advantages of Mir over Skylab You missed the most basic and important one: Skylab is debris scattered over the Australian desert; Mir is still up there. Evelyn C. Leeper 201-957-2070 UUCP: mtune!mtgzy!ecl or ecl@mtgzy.att.com ARPA: ecl%mtgzy@att.arpa ------------------------------ Date: 19 May 88 21:47:25 GMT From: ulysses!terminus!rolls!mtuxo!mtgzz!dls@ucbvax.berkeley.edu (XMRP50000[jto]-d.l.skran) Subject: Re: Yet again the advantages of Mir over Skylab Detailed comparisons of research output from MIR/Salyut and Skylab are probably impossible -- I strongly doubt the Soviets make public any significant number of their real breakthroughs. Dale ------------------------------ Date: 20 May 88 19:23:40 GMT From: snowdog@athena.mit.edu (Richard the Nerd) Subject: Mir predictions Hi there! Another evening visibility window for Mir is coming up, so I thought I'd post some predictions for SF as usual. Now, I am going home to Toronto tomorrow, and won't be back for a week. With all the manouevres that folks think are likely occur, the predictions might be WAY out by the 28th, but, alas, I can't help it now. Good luck anyways! BTW, ignore the magnitude predictions. I have the wrong size data stored for Mir and I did not bother to change them yet. Actually, if you want reasonable predictions just subtract about 4.5 from each predicted value. This is a message largely for folks on the mailing list. (People on this list get predictions for a few requested satellites, calculated for their own locations. If you'd like to be on this, drop off a note including your latitude, longitude, sea level elevation, time zone, name of town, and the satellites you would like to see, and I can put you on it.) Anyways, for those that asked to be on the list but did not receive anything, please drop off a note - I have no clue whether the predictions are reaching you, but I am making every effort to send them successfully. So, here are the predictions for SF: Prediction for: San Francisco CA Lat: 37.800000 Lonw: 122.400000 Ht: 0. Zone: 8.00000 DST: 1.0 Satellite: Mir 16609 Age: 17.5 days Unc: 171 sec Local Date: 1988 5 28 TIME MAG ILL AZ EL R.A. DEC RANGE VANG -------- ----- --- --- -- ----- ----- ----- ---- 22:27:40 5.3 37 260 29 09:44 10.7 626 0.47 22:28:00 5.0 36 269 37 09:52 21.6 526 0.65 22:28:10 4.8 35 277 41 09:57 28.5 485 0.76 22:28:20 4.7 34 286 45 10:03 36.5 452 0.87 22:28:30 4.6 34 299 49 10:12 45.5 428 0.96 22:28:40 4.5 34 314 51 10:25 55.3 416 1.02 22:28:50 4.5 34 331 51 10:46 65.2 416 1.02 22:29:00 4.5 35 346 49 11:29 74.4 428 0.96 22:29:10 4.6 36 358 45 13:26 81.6 452 0.87 22:29:20 4.7 37 8 41 17:28 82.4 485 0.76 22:29:30 4.9 38 15 37 19:34 77.7 526 0.65 22:29:40 5.1 39 20 33 20:19 72.5 574 0.55 22:29:50 5.2 40 25 29 20:41 67.8 626 0.47 Prediction for: San Francisco CA Lat: 37.800000 Lonw: 122.400000 Ht: 0. Zone: 8.00000 DST: 1.0 Satellite: Mir 16609 Age: 18.4 days Unc: 190 sec Local Date: 1988 5 29 TIME MAG ILL AZ EL R.A. DEC RANGE VANG -------- ----- --- --- -- ----- ----- ----- ---- 21:15:50 4.5 84 172 27 13:07 -24.3 657 0.56 21:16:00 4.4 86 166 29 13:29 -21.4 622 0.62 21:16:10 4.2 89 159 31 13:52 -18.0 594 0.68 21:16:20 4.1 92 151 33 14:17 -14.3 573 0.73 21:16:30 4.1 93 142 34 14:42 -10.2 561 0.76 21:16:40 4.0 95 133 34 15:08 -5.9 558 0.76 21:16:50 4.1 95 124 33 15:33 -1.6 565 0.75 21:17:00 4.1 95 115 32 15:57 2.4 580 0.71 21:17:10 4.2 94 107 31 16:20 6.1 604 0.66 21:17:20 4.4 92 100 29 16:42 9.4 636 0.59 21:17:30 4.5 90 95 26 17:02 12.3 673 0.53 Prediction for: San Francisco CA Lat: 37.800000 Lonw: 122.400000 Ht: 0. Zone: 8.00000 DST: 1.0 Satellite: Mir 16609 Age: 19.4 days Unc: 212 sec Local Date: 1988 5 30 TIME MAG ILL AZ EL R.A. DEC RANGE VANG -------- ----- --- --- -- ----- ----- ----- ---- 21:38:20 5.5 29 258 29 09:06 9.8 620 0.46 21:38:40 5.2 28 268 37 09:15 20.6 520 0.65 21:38:50 5.0 28 275 42 09:21 27.6 478 0.76 21:39:00 4.9 28 284 46 09:28 35.6 444 0.88 21:39:10 4.7 28 297 50 09:38 44.8 419 0.98 21:39:20 4.6 29 313 53 09:53 54.6 407 1.04 21:39:30 4.6 31 331 53 10:18 64.6 407 1.04 21:39:40 4.5 33 347 51 11:07 73.8 419 0.98 21:39:50 4.6 36 0 46 13:10 80.6 443 0.88 21:40:00 4.7 38 9 42 16:43 81.1 477 0.76 21:40:10 4.8 40 16 37 18:41 76.6 519 0.65 21:40:20 4.9 42 22 33 19:28 71.6 567 0.55 21:40:30 5.1 44 26 29 19:53 67.0 619 0.47 Good luck once again! Rich Brezina Snowdog@athena.mit.edu (most nets, thank whomever) ------------------------------ End of SPACE Digest V8 #237 *******************