#11
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For Want Of A Bolt
On Tue, 23 Sep 2003 13:13:08 CST, in a place far, far away,
(Henry Spencer) made the phosphor on my monitor glow in such a way as to indicate that: I'm told that the component-qualification rules for undersea-cable repeaters make space-qualification procedures look amateurish. It would be interesting, then to know how they compare to, say, satellite transponders in terms of cost per pound. -- simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole) interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org "Extraordinary launch vehicles require extraordinary markets..." Swap the first . and @ and throw out the ".trash" to email me. Here's my email address for autospammers: |
#13
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For Want Of A Bolt
On Tue, 23 Sep 2003 16:58:20 CST, in a place far, far away,
(Lou Scheffer) made the phosphor on my monitor glow in such a way as to indicate that: (Rand Simberg) wrote in message . .. On Tue, 23 Sep 2003 13:13:08 CST, in a place far, far away, (Henry Spencer) made the phosphor on my monitor glow in such a way as to indicate that: I'm told that the component-qualification rules for undersea-cable repeaters make space-qualification procedures look amateurish. It would be interesting, then to know how they compare to, say, satellite transponders in terms of cost per pound. The undersea repeaters have a big advantage - they really only have one constraint, reliability. I'd guess they care very little about weight, very little about thermal control, and they don't need to endure the stresses of launch. All of which could be true of satellites as well, with improved transportation, which was the point of my column. -- simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole) interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org "Extraordinary launch vehicles require extraordinary markets..." Swap the first . and @ and throw out the ".trash" to email me. Here's my email address for autospammers: |
#14
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For Want Of A Bolt
Lou Scheffer wrote:
(Lou Scheffer) wrote in message om... (Derek Lyons) wrote in message ... h (Rand Simberg) wrote: "But that doesn't explain why similar systems designed for marine use [...] can be built for orders of magnitude less." Please provide a cite of a marine system of the equivalent complexity and mission of the weather sat with a design lifetime of years or decades. (Or any marine system with those kinds of lifetime requirements.) Transatlantic cables come close. Before fiber optics, these had repeaters every few km. Since they were in series, ALL of the repeaters must work. If I remember correctly, they were designed so the cable as a whole had a 20 year lifetime. Using good old conservative engineering, the even made this work with vacuum tubes(!). Needless to say this was one of the first applications of transistors. Oops - this was NOT one of the first uses of transistors. Another article states that they were still built with vacuum tubes in 1964, 10 years after transistors were used for other applications, since transistors were not yet proven to be more reliable. In retrospect this makes perfect sense - any reliability conscious field will not rush to adapt new technology, no matter how promising, if the old technology is working at least OK. Lou Scheffer When a shuttle crew did a satellite upgrade (not sure if it was Solar Max, or Hubble), it was noted that the replacement units were 386 processor based. Some people didn't understand why...you basically just answered them. (Espically when you add in uncertainty as to how well a new processor design will tolerate long term ionizing radiation exposure) |
#15
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For Want Of A Bolt
(Lou Scheffer) writes:
h (Rand Simberg) wrote in message . .. On Tue, 23 Sep 2003 13:13:08 CST, in a place far, far away, (Henry Spencer) made the phosphor on my monitor glow in such a way as to indicate that: I'm told that the component-qualification rules for undersea-cable repeaters make space-qualification procedures look amateurish. It would be interesting, then to know how they compare to, say, satellite transponders in terms of cost per pound. The undersea repeaters have a big advantage - they really only have one constraint, reliability. I'd guess they care very little about weight, very little about thermal control, and they don't need to endure the stresses of launch. My intuition says that the costs will go up as something like the square of the number of difficult constraints. For example, a simple and reliable way to make something stand up to vibration (or sea water immersion in this case) is to pot it in epoxy. If you are mass-sensitive, though, you can't do this and you'll need to do a lot more tricky design and qualification. So I'll wager (without evidence) that the submarine stuff is still cheaper, even if the component qualification is even more stringent and hence the parts more expensive. What about this for an evidence: the thousands of submarines and the million or more of people who traveled in them vs. the tens of space capsule and the hundred of astronauts. -- __Pascal_Bourguignon__ http://www.informatimago.com/ Do not adjust your mind, there is a fault in reality. |
#16
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For Want Of A Bolt
(Lou Scheffer) wrote:
(Derek Lyons) wrote in message ... h (Rand Simberg) wrote: "But that doesn't explain why similar systems designed for marine use (the ocean has extremely high positive pressures, and seawater is an extremely corrosive environment) can be built for orders of magnitude less." Please provide a cite of a marine system of the equivalent complexity and mission of the weather sat with a design lifetime of years or decades. (Or any marine system with those kinds of lifetime requirements.) Transatlantic cables come close. Before fiber optics, these had repeaters every few km. Since they were in series, ALL of the repeaters must work. If I remember correctly, they were designed so the cable as a whole had a 20 year lifetime. Using good old conservative engineering, the even made this work with vacuum tubes(!). Needless to say this was one of the first applications of transistors. Indeed. And they were *extremely* expensive. Somewhere I have a telco manual from the early 70's that cites the costs of a repeater as being in excess of a million dollars a pop. It goes to great lengths to explain and stress the engineering, qualification, and component testing required. Transoceanic cable repeaters and SOSUS arrays are about the only things marine I can think of that are designed for decades of unmaintained service, and both are extremely expensive. Most other things marine seem to be designed for shorter lifetimes and hence don't meet the similarity requirements Rand specifies, or are far less complex than a weather sat, and equally fail to meet the similarity requirement. FWIW, when pressed Rand declined to supply marine example at all. D. -- The STS-107 Columbia Loss FAQ can be found at the following URLs: Text-Only Version: http://www.io.com/~o_m/columbia_loss_faq.html Enhanced HTML Version: http://www.io.com/~o_m/columbia_loss_faq_x.html Corrections, comments, and additions should be e-mailed to , as well as posted to sci.space.history and sci.space.shuttle for discussion. |
#17
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For Want Of A Bolt
In sci.space.policy Joann Evans wrote:
When a shuttle crew did a satellite upgrade (not sure if it was Solar Max, or Hubble), it was noted that the replacement units were 386 processor based. Some people didn't understand why...you basically just answered them. (Espically when you add in uncertainty as to how well a new processor design will tolerate long term ionizing radiation exposure) Various x86 with a low number for x are very popular in embedded systems. No point in paying for more speed than you need (yes, of course you can cheaper 386 than 486) -- Sander +++ Out of cheese error +++ |
#18
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For Want Of A Bolt
h (Rand Simberg) wrote in message . ..
On Tue, 23 Sep 2003 13:13:08 CST, in a place far, far away, (Henry Spencer) made the phosphor on my monitor glow in such a way as to indicate that: I'm told that the component-qualification rules for undersea-cable repeaters make space-qualification procedures look amateurish. It would be interesting, then to know how they compare to, say, satellite transponders in terms of cost per pound. From: http://davidw.home.cern.ch/davidw/public/SubCables.html "Repeaters are devices which are 100-200 cm long, 30-50 cm in diameter, weigh about 300-500 kg and cost 500-1000 K$ each. They are assembled in clean-rooms and typically designed for a lifetime of 25 years at up to 7000 meters depth without maintenance. " So they are about $2000/kg. Of course, since weight is not a big concern to them, perhaps the right metric is cost per equivalent functionality. This would be best obtained from the first generation of optical repeaters, which did optical-electrical-optical, which is much more analogous to a satellite transponder. Lou Scheffer |
#19
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For Want Of A Bolt
"Henry Spencer" wrote in message
... In article , Lou Scheffer wrote: Transatlantic cables... Oops - this was NOT one of the first uses of transistors. Another article states that they were still built with vacuum tubes in 1964, 10 years after transistors were used for other applications, since transistors were not yet proven to be more reliable. In retrospect this makes perfect sense - any reliability conscious field will not rush to adapt new technology, no matter how promising, if the old technology is working at least OK. I'm told that the component-qualification rules for undersea-cable repeaters make space-qualification procedures look amateurish. Correct. Worked with son of the Bell engineer that qualified the capacitors for the repeaters on the Transatlantic cable. Quality was unmatched (even by NASA) ..... of course the price for a one minute Transatlantic call (at that time) was not cheap either ! GB |
#20
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For Want Of A Bolt
"Joann Evans" wrote in message
... Lou Scheffer wrote: (Lou Scheffer) wrote in message om... (Derek Lyons) wrote in message ... h (Rand Simberg) wrote: Oops - this was NOT one of the first uses of transistors. Another article states that they were still built with vacuum tubes in 1964, 10 years after transistors were used for other applications, since transistors were not yet proven to be more reliable. In retrospect this makes perfect sense - any reliability conscious field will not rush to adapt new technology, no matter how promising, if the old technology is working at least OK. Lou Scheffer When a shuttle crew did a satellite upgrade (not sure if it was Solar Max, or Hubble), it was noted that the replacement units were 386 processor based. Some people didn't understand why...you basically just answered them. (Espically when you add in uncertainty as to how well a new processor design will tolerate long term ionizing radiation exposure) It was the Hubble space telescope. I liked the power supply swap in last service mission. Higher risk - but high rewards. gb |
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