henry@utzoo.uucp (Henry Spencer) (10/09/88)
In article <1344@thumper.bellcore.com> karn@thumper.bellcore.com (Phil R. Karn) writes: >By the way, this is an excellent illustration of how excessive reliance >on large manned missions has hindered technological development. The >latter inherently requires risk-taking that is acceptable only when >human lives and/or extremely large sums of money are not at stake. Oh, nonsense. Do you imagine that the Soviets would hesitate to fly a slightly risky mission if it seemed worthwhile? Phil, you do your cause a disservice when you persist in claiming that NASA's ridiculous attitudes are "inherently" a constraint on manned spaceflight. Dick Rutan and Jeana Yeager, for example, would give you a different opinion. -- The meek can have the Earth; | Henry Spencer at U of Toronto Zoology the rest of us have other plans.|uunet!attcan!utzoo!henry henry@zoo.toronto.edu
karn@thumper.bellcore.com (Phil R. Karn) (10/10/88)
Oh, come on Henry, I'm right and you know it. :-) Just see my previous postings regarding Microsat for evidence of what you can do for very little money when you don't have human lives riding on it. Even in the unmanned arena, AMSAT has made significant contributions to spacecraft technology, usually because we were forced to by the cost of the existing solutions. For example, the command system on Oscar-13, although it may be over a decade old in design, is much more sophisticated than the corresponding system in most existing geostationary communications satellites. (I understand they still use audio tones from the ground to fire their motors.) Also take a look at our Phase 4 (geostationary) design. A three-axis spacecraft that looks like a spinner (no despun bearing or steered solar arrays, too expensive). An attitude control system based on fluid momentum loops (constant use of thrusters is too expensive). An attitude sensor system likely based on radio interferometry (conventional optical sensors are too expensive). Extremely high efficiency linear RF amplifiers (extra solar arrays are too expensive). And so on. Necessity is often the mother of invention in AMSAT, and more often than not, the necessity comes from the lack of funds to do things the "standard" way. But if you combine relatively lavish funding with a "you cannot fail, human lives and lots of money are on the line" directive, then you get extremely conservative, and your rate of technological development slows to a crawl. The perception of the space shuttle as the ultimate symbol of American high technology is a master stroke of NASA public relations; a close look at subsystems like the onboard computers reveals just how out-of-date much of its technology (necessarily) is. Phil
henry@utzoo.uucp (Henry Spencer) (10/12/88)
In article <1348@thumper.bellcore.com> karn@thumper.bellcore.com (Phil R. Karn) writes: >Oh, come on Henry, I'm right and you know it. :-) Phil, I am perfectly willing to concede that you are 100% right, given the assumption that "manned spaceflight" means "manned spaceflight on the NASA space shuttle under NASA's rules". A silly assumption. Even ESA or JSA would tell you that, not to mention the Soviets and some of the less orthodox commercial-launch projects in the US. >Just see my previous postings regarding Microsat for evidence of what >you can do for very little money when you don't have human lives riding >on it. Remember Voyager (the Rutan one, not the JPL one) for evidence of what you can do for relatively little money when you *do* have human lives -- those of enthusiastic volunteers -- riding on it. >Even in the unmanned arena, AMSAT has made significant >contributions to spacecraft technology, usually because we were forced >to by the cost of the existing solutions... >Necessity is often the mother of invention in AMSAT, and more often than >not, the necessity comes from the lack of funds to do things the >"standard" way. AMSAT has done some very ingenious things, I will admit. However, I don't know about AMSAT, but some of the people I know who are in similar situations will admit that (a) stringent constraints do lead to some very creative solutions to problems, but (b) they kind of wish they could opt for a bit less creativity and a bit more productivity. The amateur-radio folks are in an anomalous position, in that advancement of technology is one of the reasons why they have spectrum space in the first place. Many other would-be space users are interested in results and would be happy to (in fact, would prefer to) use last year's technology if it gets the job done. AMSAT has had its share of high-tech failures, as I recall. >But if you combine relatively lavish funding with a "you >cannot fail, human lives and lots of money are on the line" directive, >then you get extremely conservative... No argument. The future of manned spaceflight lies with the USSR, and maybe with some of the crazies like Gary Hudson, not with NASA. >... The perception of the space shuttle as the >ultimate symbol of American high technology is a master stroke of NASA >public relations; a close look at subsystems like the onboard computers >reveals just how out-of-date much of its technology (necessarily) is. A close look at Soviet space (and aviation) hardware reveals just how limited the real need for up-to-date technology is, in many (not all) areas. The booster that launches Soyuz, more frequently and dependably than the US shuttle, is essentially the same one that launched Sputnik. Over 1000 launches later, it still works fine. Out of date? Who cares? Name one other launcher on which I can buy a trip to a space station just by plunking down enough cash. For that matter, name one other launcher that could get me there without costing twice as much. Ever read Arthur C. Clarke's short story "Superiority"? -- The meek can have the Earth; | Henry Spencer at U of Toronto Zoology the rest of us have other plans.|uunet!attcan!utzoo!henry henry@zoo.toronto.edu
paulf@Jessica.stanford.edu (Paul Flaherty) (10/17/88)
In article <1988Oct11.212620.2071@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >AMSAT has had its share of high-tech failures, as I recall. Please elaborate. I'm only personally familiar with the Phase III satellites (Phil can probably vouch for AMSAT *much* farther back than that), of which there have been three. The first was dumped in the drink by ArianeSpace. The second was impacted by the carrier bus just after separation; as a result, it never achieved the intended orbit, which had a number of degrading impacts on OSCAR 10 (including a far larger rad flux than was designed for). Despite this, it was a very useful spacecraft, and was used for a number of "high tech" community access experiments that were quite successful. Phase IIIc (now OSCAR 13) (no triscadecaphobia at AMSAT) was the first textbook launch we've gotten from ArianeSpace, and the satellite is performing flawlessly, at least from the last telemetry I saw (about a month ago). -=Paul Flaherty, N9FZX | "Engineer: A machine for converting beer ->paulf@shasta.Stanford.EDU | into blueprints."
henry@utzoo.uucp (Henry Spencer) (10/21/88)
In article <3946@Portia.Stanford.EDU> paulf@Jessica.stanford.edu (Paul Flaherty) writes: >>AMSAT has had its share of high-tech failures, as I recall. > >Please elaborate. I'm not thinking of total satellite failures, but of subsystem failures. The specific one that comes to mind is those DRAMs aboard Oscar 10 (I think it was), which sounded good early on -- Phil posted a description and commentary which added up to "it's working great so far" -- but proceeded to fail, badly enough that I gather Amsat has given up on that approach. -- The meek can have the Earth; | Henry Spencer at U of Toronto Zoology the rest of us have other plans.|uunet!attcan!utzoo!henry henry@zoo.toronto.edu
karn@thumper.bellcore.com (Phil R. Karn) (10/22/88)
> I'm not thinking of total satellite failures, but of subsystem failures. > The specific one that comes to mind is those DRAMs aboard Oscar 10 (I > think it was), which sounded good early on -- Phil posted a description > and commentary which added up to "it's working great so far" -- but > proceeded to fail, badly enough that I gather Amsat has given up on > that approach. Given up on what approach? We replaced the DRAMS with radiation-hardened SRAMS in Oscar 13. We do not expect radiation damage to be the limiting factor in this spacecraft's lifetime. As for Oscar-10 -- I and others who researched the subject *did* expect memory problems. The decision to fly them was made only when there appeared to be no alternative to get the spacecraft to the launch pad in time. Other than this change, many of the bus subsystems on Oscar-13 are identical to those on Oscar-10; indeed, many of the modules were originally constructed as flight-ready spares for the earlier spacecraft. The differences are mainly in the communications transponders (several more were added, but the same principles were used) and in the kick motor control system (another mechanical gas pressure regulator wasn't available for a reasonable price, so we designed an active electronic replacement that actually worked better). Phil
henry@utzoo.uucp (Henry Spencer) (10/25/88)
In article <1356@thumper.bellcore.com> karn@thumper.bellcore.com (Phil R. Karn) writes: >Given up on what approach? DRAMs in space. >We replaced the DRAMS with radiation-hardened >SRAMS in Oscar 13. We do not expect radiation damage to be the limiting >factor in this spacecraft's lifetime. As for Oscar-10 -- I and others >who researched the subject *did* expect memory problems. The decision to >fly them was made only when there appeared to be no alternative to get >the spacecraft to the launch pad in time. The impression I got was that at least some of the people involved felt that this was not merely an emergency expedient, but also an experiment to find out whether the technology would work well enough to be used for other things. It didn't. Understand, I'm not saying that this is a bad thing. Flying something to find out if it works is a whole lot better than having to prove it will work before you're allowed to fly it. My point was just that some of the Oscars have had failures; not all of the neat ideas have worked. -- The dream *IS* alive... | Henry Spencer at U of Toronto Zoology but not at NASA. |uunet!attcan!utzoo!henry henry@zoo.toronto.edu
karn@ka9q.bellcore.com (Phil Karn) (10/26/88)
Ah, now I understand the context of your comment. Actually, we're still flying DRAMs in other spacecraft operating in more benign environments. Both UoSAT-Oscar-9 and UoSAT-Oscar-11 have 4116 DRAM in their primary onboard computers. These are the same types flown in Oscar-10. Unlike Oscar-10, however, the UoSATs are in low earth orbits where the radiation flux is much less. They are both working fine. As for risky technology sometimes failing, that's precisely my point! When you take the low-cost, unmanned approach to spacecraft design, you can afford to lose on a few risks. If you can't accept the consequences of a failure, you'd never try anything new. Phil
henry@utzoo.uucp (Henry Spencer) (10/30/88)
In article <1366@thumper.bellcore.com> karn@ka9q.bellcore.com.UUCP (Phil Karn) writes: >As for risky technology sometimes failing, that's precisely my point! >When you take the low-cost, unmanned approach to spacecraft design, >you can afford to lose on a few risks. Phil, can you explain to me why this is unique to unmanned spacecraft? In fact, it's not -- low-cost slightly-risky approaches have been tried on manned spacecraft as well, in non-critical roles. (You wouldn't try such a thing in Ariane's guidance system, would you?) The crucial issue is not "unmanned" but "low-cost". You can afford to take risks, and hence learn something, only if the cost of a failure is manageable. What we need is transportation systems that give us more opportunities of that sort. In particular, we could use some *cheap* launchers for really small payloads, maybe 50 kg or so. Shared missions generally involve a higher failure cost, since more than one payload is at risk; we need launchers which we can afford to dedicate to one small experiment. >If you can't accept >the consequences of a failure, you'd never try anything new. Moreover, simply trying something is often a much better way to proceed than trying to guess in advance whether it's going to work. Obviously one wants to try only things that look at least somewhat promising, but studying the idea for ten years before trying it doesn't seem to do that much to improve the chances of success. -- The dream *IS* alive... | Henry Spencer at U of Toronto Zoology but not at NASA. |uunet!attcan!utzoo!henry henry@zoo.toronto.edu