revtothelimit - motorbike forum

MyLittleStudPony wrote: Fri Jan 06, 2023 10:10 pm

Le_Fromage_Grande wrote: Thu Jan 05, 2023 8:26 pm Where's the hydrogen going to come from?
And you're still dumping tons of water vapour into the upper atmosphere, I assume it's being looked at for environmental reasons, it'd save the environment a lot more of people stopped flying on holiday and pointless business trips.

It's simple enough to create hydrogen using renewable energy. But fucking expensive. It's really necessary to massively increase the cost of air travel. The polluters will pay!

Or they could be encouraged not to fly, saving the environment more because then the aircraft wouldn't have to be built.

Horse wrote: Fri Jan 06, 2023 12:29 pm

No seats either. Hanging straps, like on the tube.

Ryanair actually proposed this to the CAA if I mind right.

Bigjawa wrote: Sat Jan 07, 2023 9:01 pm
Ryanair actually proposed this to the CAA if I mind right.

They did

Don't see the issue. Even if you cut the planes in the air by 75% why not have the ones that are up there running on hydrogen? Also, not all planes up there are carrying passengers/tourists. A quick shufti at Flightradar on many routes more are freight than people carriers.

Need to do the same with shipping.

Ryanair propose a lot of daft stuff...they don't intend to actually do any of it AIUI, it's just to generate headlines.

Totally agree that "fly less" should be a big part of the solution here though! IMO e-mail and Zoom have done more on that front than any government ever could.

Covid killed off a lot of business travel and the demand for reliable video calling has been successful enough to change the way a lot of businesses operates. It's a major concern for airlines that business travel wont return to where it was pre covid. That's a good thing as in an age of communication and concerns over global warming etc, it really makes no sense for junkets all over the place.

Bigjawa wrote: Sat Jan 07, 2023 9:01 pm

Horse wrote: Fri Jan 06, 2023 12:29 pm
No seats either. Hanging straps, like on the tube.

Ryanair actually proposed this to the CAA if I mind right.

I doubt it, because there is a requirement for passengers to sit in 9g rated seats, same as there is to have unrestricted access to toilets when RYR were supposedly going to start charging. MOL stirring the old publicity barrel again.

Re hydrogen fuel, I'm not going to hold my breath. Nothing approaches the usability of kerosene, the relatively safe handling, the cost, the ease of storage and the energy density. Yes, it's fairly straightforward to make an engine run on H2, RR has already run a demo engine doing just that. But when you start putting it in aeroplanes as the sole fuel a whole new set of challenges arise. You can no longer use wings and vertical stabilisers for storage so you end up with separate tanks which use revenue space. Not sure of you can liquefy this stuff but if you do you'll suffer massive trim issues as body tanks empty, and if you don't you'll be massively limited in how much fuel you can carry which means range suffers. Then you have the biggest problem - H2 is a very reactive element which forms very stable compounds. Breaking it off from water requires massive amounts of electricity, which is expensive. Even cracking it from methane isn't cheap. This is an interesting diversion, like electric flight, but neither provides a viable option to replace kerosene IMO. The best bet to go carbon neutral is biofuel, and we're almost there now. Engines can use it with very few modifications, really it just needs to be productionised.

Bring back the old diesels where we would be running on old chip oil. Nope, no way to control the usage to tax that

Hydrogen is about three times as energy dense as oil based fuels, weight for weight. That's why its such a compelling choice for rockets and very attractive for aircraft too.

It's just pretty low energy density by volume so you need a big tank, albeit one carrying not much weight.

Tomcat wrote: Wed Jan 11, 2023 3:44 pm

Bigjawa wrote: Sat Jan 07, 2023 9:01 pm

Horse wrote: Fri Jan 06, 2023 12:29 pm No seats either. Hanging straps, like on the tube.

Ryanair actually proposed this to the CAA

I doubt it, because there is a requirement for passengers to sit in 9g rated seats

I saw it on a BBC show - and it wasn't a documentary

an interesting test bed setup. that is a 1.8MW motor but that prop will be fixed pitch at quite a low power setting.



https://www.linkedin.com/pulse/zeroavia ... g-largest/

Interesting thing about that ^^^ is that it's hydrogen electric. I had to go reading a bit deeper cause the article says "turboprop", but ZeroAvia themselves say it's hydrogen electric. I.e. an electric motor powered by a hydrogen fuel cell and not a turboprop.

Mr. Dazzle wrote: Sat May 27, 2023 7:14 pm Interesting thing about that ^^^ is that it's hydrogen electric. I had to go reading a bit deeper cause the article says "turboprop", but ZeroAvia themselves say it's hydrogen electric. I.e. an electric motor powered by a hydrogen fuel cell and not a turboprop.

yeah, I've just edited the post because I thought it had a gas turbine and the eleccy motor, but I think it's just the 1.8 MW motor.

ZeroAvia are not the only one trying to get this to work, there's a bit of an arms race going on at the moment which is very good news if your in the business of making propellers


https://www.flightglobal.com/safety/ala ... 80.article

demographic wrote: Thu Jan 05, 2023 7:22 pm

MingtheMerciless wrote: Thu Jan 05, 2023 6:58 pm Hmm hydrogen and flying vehicles was tried a few years ago, it didn't end well.

Random fact for the day but my (now dead) uncle Geoff sas the Hindenburg over Keithley when he was a young lad.
That was in the 1930s.

Equally random fact, my granny lived in Canada when she was a kid and saw the R100 (airship, not BMW) when it was over impressing the colonial types.

Taff wrote: Sat May 27, 2023 7:06 pm an interesting test bed setup. that can produce 4500ish SHP but that prop will be fixed pitch at quite a low power setting.



https://www.linkedin.com/pulse/zeroavia ... g-largest/

If that's the hydrogen-electric version, it's supposed to produce 2,700hp...which is quite a bit of oomph.

(Should get that truck moving quite quickly )

Taff wrote: Sat May 27, 2023 7:17 pm which is very good news if your in the business of making propellers

Or very high performance electric motors

Our aero division span off into a separate new firm a while ago, but I still work with em quite a lot. We share R&D, which is my section.

Count Steer wrote: Sat May 27, 2023 7:19 pm

Taff wrote: Sat May 27, 2023 7:06 pm an interesting test bed setup. that can produce 4500ish SHP but that prop will be fixed pitch at quite a low power setting.



https://www.linkedin.com/pulse/zeroavia ... g-largest/

If that's the hydrogen-electric version, it produces 2,700hp...which is quite a bit of oomph.

(Should get that truck moving quite quickly )

I pretty sure it is the hydro-electric, it could move the truck at take off power, but the propeller is fixed at a pitch which I think is at an angle to give just enough resistance for the motor to do a bit of work and isn't freewheeling. Ordinarily the propeller uses engine oil as hydraulic fluid to control pitch, but as the leccy motor doesn't have oil variable control is a bit of a problem.

Bit odd they didn't just fit electric pitch control....

Honestly though, I'm not sure if you need variable pitch on an electric engine. You don't need to run at constant speed anything like as much and motors are generally far more tolerant to a wide range of speeds/powers. Similar to why electric cars usually only have one gear.

Maybe you can just ditch the weight and cost of a variable pitch prop?

Mr. Dazzle wrote: Sat May 27, 2023 7:34 pm Bit odd they didn't just fit electric pitch control....

Honestly though, I'm not sure if you need variable pitch on an electric engine. You don't need to run at constant speed anything like as much and motors are generally far more tolerant to a wide range of speeds/powers. Similar to why electric cars usually only have one gear.

Maybe you can just ditch the weight and cost of a variable pitch prop?

for smaller props fixed pitch variable speed is common place but the bigger stuff is all fixed speed variable pitc. One of the snags is that there is a regulation that the propeller is not allowed to cause significant drag if you lose the engine so you need to be able to turn the prop so that its pitch is inline with the airflow. Also, High drag means that the propeller turns into a windmill and will very quickly overspeed risking throwing a blade.
The forces involved with changing pitch at 1k RPM is significant and hydraulic is the best way to do it, the weight of the pitch change mechanisms is not really a lot in the grand scheme of things

Count Steer wrote: Sat May 27, 2023 7:19 pm

Taff wrote: Sat May 27, 2023 7:06 pm an interesting test bed setup. that can produce 4500ish SHP but that prop will be fixed pitch at quite a low power setting.



https://www.linkedin.com/pulse/zeroavia ... g-largest/

If that's the hydrogen-electric version, it's supposed to produce 2,700hp...which is quite a bit of oomph.

(Should get that truck moving quite quickly )

Aren't those big Tu-95 bears something like 15000shp per engine?