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In article ,
Richard Riley wrote: There's more energy available in a pound of liquid hydrogen than in a pound of any conventional hydrocarbon like jet fuel. The LE (Long Endurance) part of HALE is the basic design goal. A pound of LH2 has about 2.6 times as much energy as a pound of gasoline. The temperature at 65k isn't significantly different from 50k - jet fuel would work fine. But when you weigh in with the tanking required to keep the stuff, the net system energy (fuel + tank) gets out of hand. Hydrocarbons are orders of magnitude more dense than LH2 and do not require special containers or special purging of fuel lines to get rid of air, nitrogen and water. LH2 will freeze all of the above and reacts violently with FROX (frozen oxygen). Hydrogen leaks burn clear and hot, too! To purge LH2 lines, you first flush with dry nitrogen, followed by a helium flush, to get rid of the nitrogen, then gaseous H2. It not an inexpensive process, and widespread use would severely impact the world supply of helium. |
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On Fri, 26 Oct 2007 11:49:47 -0400, Orval Fairbairn
wrote in : In article , Richard Riley wrote: There's more energy available in a pound of liquid hydrogen than in a pound of any conventional hydrocarbon like jet fuel. The LE (Long Endurance) part of HALE is the basic design goal. A pound of LH2 has about 2.6 times as much energy as a pound of gasoline. The temperature at 65k isn't significantly different from 50k - jet fuel would work fine. But when you weigh in with the tanking required to keep the stuff, the net system energy (fuel + tank) gets out of hand. Hydrocarbons are orders of magnitude more dense than LH2 and do not require special containers or special purging of fuel lines to get rid of air, nitrogen and water. LH2 will freeze all of the above and reacts violently with FROX (frozen oxygen). Hydrogen leaks burn clear and hot, too! To purge LH2 lines, you first flush with dry nitrogen, followed by a helium flush, to get rid of the nitrogen, then gaseous H2. It not an inexpensive process, and widespread use would severely impact the world supply of helium. If that's the case, what would be your guess as to why Boeing is considering a hydrogen fueled HALE? |
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Larry Dighera wrote:
On Fri, 26 Oct 2007 11:49:47 -0400, Orval Fairbairn wrote in : In article , Richard Riley wrote: There's more energy available in a pound of liquid hydrogen than in a pound of any conventional hydrocarbon like jet fuel. The LE (Long Endurance) part of HALE is the basic design goal. A pound of LH2 has about 2.6 times as much energy as a pound of gasoline. The temperature at 65k isn't significantly different from 50k - jet fuel would work fine. But when you weigh in with the tanking required to keep the stuff, the net system energy (fuel + tank) gets out of hand. Hydrocarbons are orders of magnitude more dense than LH2 and do not require special containers or special purging of fuel lines to get rid of air, nitrogen and water. LH2 will freeze all of the above and reacts violently with FROX (frozen oxygen). Hydrogen leaks burn clear and hot, too! To purge LH2 lines, you first flush with dry nitrogen, followed by a helium flush, to get rid of the nitrogen, then gaseous H2. It not an inexpensive process, and widespread use would severely impact the world supply of helium. If that's the case, what would be your guess as to why Boeing is considering a hydrogen fueled HALE? A niche device with limited production where such things are of minimal concern maybe? -- Jim Pennino Remove .spam.sux to reply. |
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Larry Dighera wrote:
On Sat, 27 Oct 2007 01:15:17 GMT, wrote in : Larry Dighera wrote: On Fri, 26 Oct 2007 11:49:47 -0400, Orval Fairbairn wrote in : In article , Richard Riley wrote: There's more energy available in a pound of liquid hydrogen than in a pound of any conventional hydrocarbon like jet fuel. The LE (Long Endurance) part of HALE is the basic design goal. A pound of LH2 has about 2.6 times as much energy as a pound of gasoline. The temperature at 65k isn't significantly different from 50k - jet fuel would work fine. But when you weigh in with the tanking required to keep the stuff, the net system energy (fuel + tank) gets out of hand. Hydrocarbons are orders of magnitude more dense than LH2 and do not require special containers or special purging of fuel lines to get rid of air, nitrogen and water. LH2 will freeze all of the above and reacts violently with FROX (frozen oxygen). Hydrogen leaks burn clear and hot, too! To purge LH2 lines, you first flush with dry nitrogen, followed by a helium flush, to get rid of the nitrogen, then gaseous H2. It not an inexpensive process, and widespread use would severely impact the world supply of helium. If that's the case, what would be your guess as to why Boeing is considering a hydrogen fueled HALE? A niche device with limited production where such things are of minimal concern maybe? With all due respect, are you saying that Boeing choose a hydrogen fueled engine for their HALE, because they are unconcerned with its complexity due to its possible limited production? Of course. How many unmanned aircraft that stay aloft for seven days and fly in the stratosphere do you think there is a market for? They are building something to meet a unique specification, much like a nuclear submarine or a space shuttle, and using technology that will likely never see mass production. Ever seen a nuclear bass boat or a hydrazine powered 172? -- Jim Pennino Remove .spam.sux to reply. |
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In article ,
Richard Riley wrote: On Fri, 26 Oct 2007 11:49:47 -0400, Orval Fairbairn wrote: In article , Richard Riley wrote: There's more energy available in a pound of liquid hydrogen than in a pound of any conventional hydrocarbon like jet fuel. The LE (Long Endurance) part of HALE is the basic design goal. A pound of LH2 has about 2.6 times as much energy as a pound of gasoline. The temperature at 65k isn't significantly different from 50k - jet fuel would work fine. But when you weigh in with the tanking required to keep the stuff, the net system energy (fuel + tank) gets out of hand. Then one would expect the Boeing HALE to incorporate an extraordinary lightweight tankage system, wouldn't one? No. |
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