SpaceX is planning to reuse the first stage of the F1, and all of the F9 and (probably) F9 Heavy. This would make the F9 the first RLV. Dragon will be the first reusable capsule. How will reusability work out?
Quote from: tnphysics on 01/01/2009 07:15 pmSpaceX is planning to reuse the first stage of the F1, and all of the F9 and (probably) F9 Heavy. This would make the F9 the first RLV. Dragon will be the first reusable capsule. How will reusability work out?The Shuttle is an RLV. Gemini was designed with reusability in mind.
Quote from: ChefPat on 01/01/2009 08:16 pmQuote from: tnphysics on 01/01/2009 07:15 pmSpaceX is planning to reuse the first stage of the F1, and all of the F9 and (probably) F9 Heavy. This would make the F9 the first RLV. Dragon will be the first reusable capsule. How will reusability work out?The Shuttle is an RLV. Gemini was designed with reusability in mind.The Shuttle ET is not reusable. Titan II was not reusable, and in practice, only one Gemini capsule flew twice.
Generally speaking, if a goal of your manned program is nationalist propaganda, it makes more sense to use each spacecraft once and then mount them in museums and outside government buildings. Ergo, reusability is only a factor when money matters more.
Quote from: mlorrey on 01/02/2009 09:01 amGenerally speaking, if a goal of your manned program is nationalist propaganda, it makes more sense to use each spacecraft once and then mount them in museums and outside government buildings. Ergo, reusability is only a factor when money matters more.Do you honestly believe that having a souvenir to display is a significant factor in the non re-usability of past manned capsules ? Not something more prosaic, like say, maximizing usable payload fraction, or the high cost of refurbishing ?ISTR China used wood on some early recoverable capsules, but not on Shenzhou. The suggestion that this change was merely to appear more modern seems unreasonable: Consistency and mass seem far more likely.
Production rates implies a greater risk of any given vehicle having a manufacturing error significant enough to cause LOC, whereas building a 'perfect' vehicle that gets refurbed with care should give lower risk given sufficiently perfected design.
Quote from: mlorrey on 01/03/2009 04:00 pmProduction rates implies a greater risk of any given vehicle having a manufacturing error significant enough to cause LOC, whereas building a 'perfect' vehicle that gets refurbed with care should give lower risk given sufficiently perfected design.Where on earth do you get that from?Stable, industrial processes are typically orders of magnitude more reliable than one-off builds and refurbishing things means trying anew each time.I would love to see ONE example where your theory holds true, can give you dozens (cars, planes, computers,...) where it's the other way around.
Quote from: pippin on 01/04/2009 10:51 pmQuote from: mlorrey on 01/03/2009 04:00 pmProduction rates implies a greater risk of any given vehicle having a manufacturing error significant enough to cause LOC, whereas building a 'perfect' vehicle that gets refurbed with care should give lower risk given sufficiently perfected design.Where on earth do you get that from?Stable, industrial processes are typically orders of magnitude more reliable than one-off builds and refurbishing things means trying anew each time.I would love to see ONE example where your theory holds true, can give you dozens (cars, planes, computers,...) where it's the other way around.Industrial processes achieve reliability for MOST of a production run by using quality processes to toss out items that dont pass.
Statistically speaking, in any production run, there will ALWAYS be items on the end of the bell curve that will fail. Doing full quality inspections on every item produced is also prohibitively expensive.
So you've seen better reliability with the entire fleet of Ford Escorts vs a one-off Rolls Royce or other hand built custom?
NDI technologies can be equally applied to both mass produced and one-offs, doing it for mass produced items is obviously cost prohibitive.
Where on earth do you get that from?Stable, industrial processes are typically orders of magnitude more reliable than one-off builds and refurbishing things means trying anew each time.I would love to see ONE example where your theory holds true, can give you dozens (cars, planes, computers,...) where it's the other way around.
Industrial processes achieve reliability through application of a learning curve and elimination of errors. You cannot do that with just one unit.
Yes. And statistically speaking that can as well be your single unit. Full inspections are absolutely common for a lot of items, even in the automotive industry; each computer chip undergoes extensive testing and here we are talking units that sell at single to three digit dollar values.For expensive items, even doing full inspections after intermediate production steps is common place.Definitely. Look up reliability of Rolls Royce when they were still mainly hand built and you'll be shocked. No comparison to normal mass produced cars. "Hand made in England" is a common synonym for bad quality in the auto industry (Sorry, Chris).Rolls Royce compensated for this by applying excessive service but that's pretty much the "Space Shuttle" business model, and especially it does definitely NOT reduce cost. Believe me, TCO of a Rolls Royce will be much higher than for a Ford Focus, and your point was it's cheaper to use RLVs.[No, as I said above, it's commonplace.What kind of quality processes (for which products) have you worked on?
************************mlorrey Quote:Industrial processes establish "reliability" by minimizing the failure rate, but still, 1 million devices with a 0.001 failure rate still means you have a thousand failures in a given time span. If that device is a one man space capsule, that means you accept 1000 deaths as an acceptable mortality rate.You point at "oh, but we flew 999,000 people to space safely"...*************************So following this logic, if you build 2 one-off perfect vehicles, then they become less safe.
Compare, for instance, an SR-71 to a fictional intercontinental reconnaissance missile you used once. You could say "Ah but Corona was such". Every orbit of a spy sat is like a new flight sortie, the comparison between spysats and spyplanes is on of automation vs humans, not reusables vs single missions. Take an MX missile that would do a spy mission. You'd need thousands to fly the same lifetime that the SR-71 did, much more expensively.