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Post by PhantomWolf on Oct 6, 2008 1:56:36 GMT -4
Just being me, I'd have thought that the least moving parts would be the way to go since that horrid moon dust stuff has a habit of getting everywhere and gumming up the works.
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sniffy
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Post by sniffy on Oct 6, 2008 9:14:39 GMT -4
If nitwits make engineering decsions, or ignore them things can, go wrong. I recall something about O-rings, a while back.
The bottom line depends on the weight. Here's some newfangled stuff here. forums.ifdg.net/index.php?showtopic=3554In an exclusive interview with Dan Rather, Vince Weldon, a 46-year veteran of Boeing (Nachrichten/Aktienkurs) and a pioneer in aerospace design, talks about the major safety problems effecting the brand new Boeing 787 Dreamliner. Speaking only to DAN RATHER REPORTS, Weldon says that Boeing's new 787 Dreamliner has major safety problems stemming from its design and use of reinforced plastics -- called composites -- that will make the plane unfit to withstand survivable crash landings. Weldon describes how the composite fuselage will "shatter, not crumple" in a crash landing. He also says that the type of composites used for the exterior of the 787 makes passengers more vulnerable to toxic fumes in the event of fire. Weldon believes it will be very difficult for Boeing to make the 787 as safe as an aluminum plane and he adds that Boeing management repeatedly ignored his concerns and those of his colleagues about the plane's design
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Post by JayUtah on Oct 6, 2008 11:06:24 GMT -4
I recall something about O-rings, a while back.
Is that relevant, or are you just taking pot shots?
The bottom line depends on the weight.
No, weight is one of many variables that is considered.
In an exclusive interview with Dan Rather, Vince Weldon, a 46-year veteran of Boeing...
...from a division having nothing to do with airliner design, not an expert in materials, and currently embroiled a messy firing from Boeing for threatening his superiors. One biased guy against an army of fully-qualified engineers and decades of flight experience with composites across the industry. Composites are not new in the aerospace industry or to airliners. We've been using them since shortly after Apollo. The 787 simply has more of it than most other airframes.
I worked on the 787 project. How many actual aerospace designs have you worked on?
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Post by Apollo Gnomon on Oct 6, 2008 13:11:22 GMT -4
Before this devolves into a urination contest I'd like to get this back to the original topic -- non-combustion sources of expanding gas for power generation. As a thought experiment, ideas like this can be very valuable even if just as seeds for other ideas. I don't think the argon-otto engine would work in a lunar vehicle, (for all the reasons mentioned by others above) but perhaps as a stationary electrical generator it might. Sterling engines are good for small amounts of high-torque expansion, but are complicated and fussy to operate. {edit - this line returned to post} One problem with Otto engines, they throw away most of the expansion energy. The pistons cannot be allowed to decelerate, or they will drag the engine. When energy sources are "cheap" or the work requires it you can afford to throw away some of the expansion. It's a cost-benefit problem. Think about drag racing Funny Cars. They are so inefficient that the fuel is still burning as it exits the exhaust pipes, because they want only the very hottest, very fastest part of the expansion cycle. Everything else slows the engine down, and create inefficiency in a different way. Our street cars throw away about 80% of the expansion, even today. Triple-expansion steam engines actually had condensing water exiting the final cylinder, for an example of the opposite end. Personally, I like turbines. They could be designed to suck most if not ALL the expansion out of a gas, using different stages of blades/chambers to allow the remaining expansion to still do work. OTECs use extremely low pressure ratios, but could theoretically do massive work on very small temperature differentials just by being huge. How much efficiency do you want to buy? Using a laser to heat the expansion gas is inefficient, why not use solar heat collection? Focusing light with mirrors or lenses has been used to flash-heat water to steam, perhaps something similar using argon or whatever is readily plentiful on the moon. Then send the super-heated high pressure gas through a turbine, generate electricity and use it for whatever, maybe even charging storage batteries on rovers. --edit to complete --edit again since Jay quoted something I deleted
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Post by JayUtah on Oct 6, 2008 14:36:47 GMT -4
Before this devolves into a urination contest :rolleyes:...
Point well taken.
sniffy, I apologize for my confrontational attitude. You touched a nerve. I worked on the 787. My team supplied to Boeing much of the analysis technology they used for structural dynamics and aerodynamics and worked with them to develop and validate their software tools. Boeing is no stranger to design with non-metallic materials, nor is design with and the analysis of CFRP structures new fields. Boeing has done an enormous amount of due diligence, at its own expense, on the airframe design.
A substantially composite airframe is being built in this case because we finally have the many decades of experience with those materials in critical aerospace applications to reason defensibly about the safey of such materials in a solution aimed toward realizing the needed benefit of fuel economy. Calling it new, untried technology is simply wrong. It is mature technology coming into its own.
In my opinion, Vince Weldon is not a credible source, and Dan Rather is not a critical journalist. Weldon has never done composites design or analysis and did not work on the 787 project. Dan Rather doesn't fact-check. Weldon brings no relevant data to the table, only doomsaying and rhetoric against Boeing executives. Makes for great tabloid news, but that's not engineering.
Yes, there remains some uncertainty among individuals at Boeing. Engineering thrives on such dissent, so long as it remains well-founded. Legitimate concerns about the safety of any product are what drive the quality programs in commercial engineering. However, not all criticism can be considered well-founded or held up by evidence. Simply stating a fear or uncertainty about a new design, without providing a toehold for empiricism, does not constitute a legitimate case.
As a thought experiment, ideas like this can be very valuable even if just as seeds for other ideas.
I have no problem with that. The best ideas in the world start from people thinking outside the box -- often well outside it. I'm just interested in maintaining the distinction between blue-sky conceptualization and actual nuts-and-bolts engineering where people actually trust their lives to your decisions.
Sterling engines are good for small amounts of high-torque expansion, but are complicated and fussy to operate.
This is why you don't want one in a critical function of human-rated technology. The most efficient engine on the planet (whichever planet you happen to be on) is not efficient at all if it's broken and your crew is gasping out their last. Designing an engine that doesn't break -- ever -- is a tall enough challenge for most engineers. Electromagnetically-actuated drive lines are quite reliable in space, and are efficient enough.
Personally I dislike having to rely on any thermodynamic cycle for mechanical power in space. A motor that requires finicky thermal conditions to start and remain working imposes thermal control constraints on the system that incorporates it. Survivability in space is often about enduring out-of-spec temperature excursions gracefully.
I'm not opposed to closed-cycle thermodynamic engines in space. But not for critical applications.
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sniffy
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Post by sniffy on Oct 6, 2008 18:07:08 GMT -4
I am not very sensitive to, "How many planes did you build". It is perfectly legitimate to ask the question; and also, to defend great persons who get very little credit for a lifetime of dedication. There is a little problem that the heavy action scares people away, another person might come up with a though experiment that is actually useful.
The otto and diesil cycle require moving parts. (Injection and spark plugs). Microwave ignition might eliminate some moving parts. Also room temperature ignition seems atractive (to me). For example Hydrogen Bromide has a boiling point of -60 C and of course it is dipolar and will react to microwave ignition. The cold temperature boiling point might be useful on the moon. If you think I am nuts for suggesting Hydrogen Bromide, feel free to say so. Thanks for considering other visitors, I hear Utah is a great state.
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Post by Apollo Gnomon on Oct 6, 2008 21:12:00 GMT -4
Gosh, Jay, you quoted me between posting an incomplete thought and my editing it for completeness!
I guess I should put the phrase about Sterling back in, so that the thread makes sense. I cut during the editing.
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Post by JayUtah on Oct 6, 2008 21:28:30 GMT -4
Gosh, Jay, you quoted me between posting an incomplete thought and my editing it for completeness! I guess I should put the phrase about Sterling back in...
If you'd like -- it was a great thought. Personally I love Stirling engines. I have one ... somewhere.
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Post by JayUtah on Oct 6, 2008 21:36:41 GMT -4
There is a little problem that the heavy action scares people away, another person might come up with a though experiment that is actually useful.
We want that sort of creativity. Just not when Grandma is flying on it.
Thanks for considering other visitors, I hear Utah is a great state.
Yep. One of the places you can set off a nuclear bomb and no one notices.
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Post by Apollo Gnomon on Oct 6, 2008 21:39:59 GMT -4
Now, about the thermodynamic cycle machines in space -- people in a minimal-survival situation don't usually get all experimental with things - you fall back on your 4 survival basics of food, water, clothing and shelter. In space, heat and atmosphere are gonna rank way up there on the list.
The last moon visitors, and the next ones as well, will be operating in the minimal survival mode. Eventually we'll have colonies of researchers, miners, or perhaps persecuted minorities from Earth living on the moon for extended periods, and they'll have more time and latitude for experiments. I'm actually quite fascinated with this idea of using non-steam, non-combustion expansion of superheated gasses to generate mechanical motion.
Spiffy - do you know what the conversion efficiency is for microwave generators? I don't. I know my microwave boils water about as fast as a "poly hot pot" of the same wattage, so I've thought over the years that it's pretty good. For some applications using microwaves to excite (not ignite) the expansion fluid might be the easiest way.
I see the base concept here as more useful for generating electricity than for spending electricity to create mechanical motion for transport or manufacturing. Perhaps it would work for things like pile drivers or mining drills, things that would be done on Earth with diesel or pneumatic equipment; stuff that would not lend itself to electrical power very well for various reasons.
Technically, Otto engines are 4-cycle. This idea would be more like a steam engine, which was "2-stroke."
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sniffy
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Post by sniffy on Oct 6, 2008 23:34:41 GMT -4
It's Sniffy not spiffy, anyway I gave a reference a while back: as the microwave bandwidth goes down, the efficiency goes in the direction of 100%. The bandwidth would have to change as the cylinder/piston volume changes.
Question, regarding turbo power generator--thousands of watts should be possible.
Can heat be collected by microwave dishes? Perhaps is is easier to focus, less susceptable to pitting from micro meteorites, and easier to maintain.
45.2% of the suns energy is infrared, about 500 watts per meter.
Band nm % UV 0-380 10.0 visible 380-760 44.8 infrared 760-inf 45.2
Page 22, online pdf document, 1.5 megabytes. Falsification Of The Atmospheric CO2 Greenhouse Efects Within The Frame Of Physics
Gerhard Gerlich Ralf D. Tscheuschner
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sniffy
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Post by sniffy on Oct 7, 2008 8:05:15 GMT -4
Whoops, microwave heating depends on the size of the molecule. Turns out this technology has been worked out for cellphones, near 100% efficiency. It may not work as well for large signal applications.
For large signals, say 50,000 watts, RF or radio frequency also goes at near 100%. It may depend on the size of the cavity or cylinder. This is junkyard, handmade stuff, ham operators should have it around. There are RF heaters that melt solder on 1/8 steel plate in the few seconds. Tuned circuits are in any book on electronics.
Maybe you can use this for your B-movie sci-fi.
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Post by Apollo Gnomon on Oct 7, 2008 12:57:55 GMT -4
Oh, man, I'm sorry. See what happens when you type without recharging the brain first? More coffee!
Naw, my B-movie science fiction has massive chemical factory ships collecting from Venus, cooking with solar heat and electricity on the long journey, and dumping usable terraforming chemicals on Mars, then going back for more.
As for the microwaves, I'm thinking about the duty cycle of equipment. Traditional steam power used combustion to heat massive tanks of water to above boiling point, which has long warm-up time. Flash heating the expansion fluid with microwaves would allow the equipment to be repositioned between uses, then fired up, used and shut down again. Better efficiency for intermittent duty equipment (say, rivet guns or blasting drills) than trying to maintain a heat/pressure system at usable levels. Microwaves would do the flash-heating job faster than resistance-wire heating.
I don't think the bandwidth would have to chase the cylinder volume, if used like a "boiler" rather than like a "spark plug."
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Post by sts60 on Oct 8, 2008 0:04:45 GMT -4
Sterling engines are good for small amounts of high-torque expansion, but are complicated and fussy to operate.
This is why you don't want one in a critical function of human-rated technology. The most efficient engine on the planet (whichever planet you happen to be on) is not efficient at all if it's broken and your crew is gasping out their last. Designing an engine that doesn't break -- ever -- is a tall enough challenge for most engineers. Electromagnetically-actuated drive lines are quite reliable in space, and are efficient enough.
Personally I dislike having to rely on any thermodynamic cycle for mechanical power in space. A motor that requires finicky thermal conditions to start and remain working imposes thermal control constraints on the system that incorporates it. Survivability in space is often about enduring out-of-spec temperature excursions gracefully.
I'm not opposed to closed-cycle thermodynamic engines in space. But not for critical applications.
Well, NASA and DOE are trying to make Stirling engines happen in space to replace RTGs. Specifically, free-piston Stirlings for electrical power generation. There are a number of materials, reliability, and control challenges. (I'm a bit player in the effort.) The advantages would be significantly less Pu-238 required, and a significantly lighter engine, for a given electrical power. There are challenges with materials, control, and reliability - it's hard to match up to nearly five decades of absolute reliability of space RTGs - but the first uses would be in mission critical, albeit unmanned, systems.
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sniffy
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Post by sniffy on Oct 9, 2008 12:52:50 GMT -4
I think microwave heating would arc, in the small cyclinder space. Infrared heating is probably better; indeed, NASA makes much more optismistic assertions than I do. www.tech-faq.com/long-distance-wireless-power-transmission.shtmlAnother option for wireless power transmission is NASA's infrared power transmission system that is capable of powering an airplane using an infrared laser that powers the photovoltaic cells located on the airplane's skin. These photovoltaic cells convert infrared energy to electricity. This also requires that the device being powered be always within sight of the transmitter.
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