21 Oct 2025, 10:36 [ UTC - 5; DST ]
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Post subject: Re: Joby Aviation more impressive than I thought  Posted: 05 Aug 2025, 15:07 |
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Joined: 03/07/18
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Location: Woburn, MA
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Username Protected wrote: Switching to H2 would require an entirely new aircraft design which is $$$$$, but the lower weight (almost 3X lower than for the same energy in Kerosene) is a big win. I expect you'd end up with a higher optimal cruise altitude. That weight savings for the energy density is real, but the balance of plant (BoP) required to operate that weight can be very heavy. It's not quite cut and dry to just compare energy per unit mass.
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Post subject: Re: Joby Aviation more impressive than I thought Posted: 05 Aug 2025, 21:52 |
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Joined: 01/22/19
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Username Protected wrote: Where are you going to put that much hydrogen on a 747? Certainly not in the wings.
Except that kerosene can be contained within wet wing structure at low cost.
Hydrogen must be stored either in heavy, high pressure cylinders , or in even heavier cryogenic cylinders.
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Post subject: Re: Joby Aviation more impressive than I thought Posted: 06 Aug 2025, 00:24 |
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Joined: 01/06/08
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Large H2 liquid tanks are not that big if they only need a limited storage time - they've been used on spacecraft since the 60s and are enough lighter than kerosine pre energy to be worth it for upper stages. (rockets aren't quite like aircraft but somewhat similar) Username Protected wrote: Switching to H2 would require an entirely new aircraft design which is $$$$$, but the lower weight (almost 3X lower than for the same energy in Kerosene) is a big win. I expect you'd end up with a higher optimal cruise altitude.
Except that kerosene can be contained within wet wing structure at low cost.
Hydrogen must be stored either in heavy, high pressure cylinders , or in even heavier cryogenic cylinders.
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Post subject: Re: Joby Aviation more impressive than I thought Posted: 06 Aug 2025, 03:07 |
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Joined: 01/30/09
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Username Protected wrote:
Hydrogen must be stored either in heavy, high pressure cylinders , or in even heavier cryogenic cylinders.
There are other ways to store hydrogen other than hydrogen gas or liquid. There are thousands of papers on hydrogen storage.
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Post subject: Re: Joby Aviation more impressive than I thought Posted: 06 Aug 2025, 07:06 |
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Username Protected wrote:
Hydrogen must be stored either in heavy, high pressure cylinders , or in even heavier cryogenic cylinders.
There are other ways to store hydrogen other than hydrogen gas or liquid. There are thousands of papers on hydrogen storage.
Yes. There is a novel method of storing hydrogen by attaching carbons to it. Permits the storage of large amounts at 14psi and essentially room temperature. Permits even novice handling. Truly revolutionary technology.
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Post subject: Re: Joby Aviation more impressive than I thought Posted: 06 Aug 2025, 13:57 |
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Joined: 01/30/09
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Username Protected wrote: Yes. There is a novel method of storing hydrogen by attaching carbons to it. Permits the storage of large amounts at 14psi and essentially room temperature. Permits even novice handling. Truly revolutionary technology. Methanol is another method and methanol carries more hydrogen than compressed or cryogenic hydrogen. Methanol is readily re-formed into hydrogen for fuel cells. Metal hydrides, liquid organics, and many other methods of storing hydrogen are known.
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Post subject: Re: Joby Aviation more impressive than I thought Posted: 06 Aug 2025, 17:47 |
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Joined: 01/22/19
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Username Protected wrote: Yes. There is a novel method of storing hydrogen by attaching carbons to it. Permits the storage of large amounts at 14psi and essentially room temperature. Permits even novice handling. Truly revolutionary technology. Methanol is another method and methanol carries more hydrogen than compressed or cryogenic hydrogen. Methanol is readily re-formed into hydrogen for fuel cells. Metal hydrides, liquid organics, and many other methods of storing hydrogen are known.
None of which is remotely cost-effective, or practical. And even if it were, the costs of changing out fueling infrastructure system-wide would kill the deal.
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