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Aviation industry tries to go green

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Re: Aviation industry tries to go green

#61

Post by yason »

WalterBright wrote: post #37
imsofuture wrote: post #29

Earlier quoted context omitted.

I know that for piston engine aircraft, it is critical that the engine be properly warmed up before takeoff. Otherwise, the engine would likely stall shortly after liftoff, leading inevitably to a crash. This is a common cause of accidents. This is not true. Engine start to takeoff is usually at least a few minutes, but there is no critical temperature factor for the engine (barring extreme heat or cold). It's a lot…

My source is my father, who flew 23 different types of aircraft, single engine, multi engine, piston and jet. He spent some years as a flight instructor, and a crash investigator for the Air Force. He said not properly warming up the piston engine meant that there was cold oil still in the reservoir, and sucking that into the engine would cause it to stall, usually right after takeoff, causing many accidents. I've re…

I can see this in my car. If the engine isn't warmed up, pulling into traffic often meant it would stall right in the middle of the lane I'm trying to cross, leaving me vulnerable to being rammed.

Sounds like your car is broken if that really happens.

A functioning car engine won't stall when pulling into traffic because of cold oil. Surely it will just wear out horribly and its lifespan will shorten to a fraction if you do that regularly but today's oils still work pretty good when cold and there will be some circulation to prevent pistons from grinding themselves stuck or bearings from mushing themselves into powder.

I could imagine you could get your engine stuck for real in very cold weather if you cold-start the car and floor it right away before there really is any practical oil circulation at all. Even if you really try this it's still more likely you'll wear out bearings first and get served a knocking engine rather than a stall or stuck pistons.

But your wording by "often meant" suggests that this stall would happen regularly if you did it with a cold engine so unless you live right next to a highway on-ramp your car probably had something else broken, causing it to stall.

Re: Aviation industry tries to go green

#62

Post by anovikov »

benhurmarcel wrote: post #54
cgrealy wrote: post #18

Earlier quoted context omitted.

Did you watch the video I posted? It specifically talks about converting a small aircraft and says you could get "about 20 minutes". Building an actually useful commercial plane (i.e. something along the lines of 737 or A320) is an order of magnitude more difficult, in fact, basically impossible with current battery technology.

For electric airliners, most promising research centers on hydrogen fuel cells, not batteries. It brings a lot of issues (mainly volume and cooling), but still it's being seriously considered.

Why not just liquid hydrogen, burned in a jet engine? Yes it has density about 12x lower then kerosene, but specific energy is about 3x higher so for the same fuel volume, we get 4x less range. In fact better than that, because of much lower weight and about 2/3 power ratio of fuel burn to aircraft weight and about 40% of weight of a typical plane being fuel, it being gradually burned during flight... it adds about 11% of range, so like 28% of the kerosene-powered range for the same fuel tank volume. So about 4500-5000km, with added benefit of fantastic takeoff performance (low weight). Enough for cross-USA travel, and non-Arctic cross-Atlantic flights (anywhere in CONUS->Bangor, Maine->Shannon, Ireland->Anywhere in EU)... solves the problem as i see it?

Re: Aviation industry tries to go green

#63

Post by snovv_crash »

zabzonk wrote: post #11
newnewpdro wrote: post #7

Earlier quoted context omitted.

> In WW2 the Germans fitted aircraft engines to their tanks, which worked great when the engines ran, but too often they didn't due to battlefield conditions. (Germany was also terribly short of avgas, which crippled those tanks.) This sounded interesting so I skimmed the tanks mentioned in [0] and only found mention of prototypes exploring use of a turboshaft engine [1] from [2]. [1] explicitly states "none of these…

Don't know about the Germans, but the British used modified aero engines quite extensively in tanks - https://www.wikiwand.com/en/Rolls-Royce_Meteor

Indeed, my grandfather was in one in Italy late in the war. From the stories he told, the crew one time got it up to 40MPH, then the crankshaft snapped.

Re: Aviation industry tries to go green

#64

Post by usrusr »

riversflow wrote: post #41
ses1984 wrote: post #38

Earlier quoted context omitted.

I was under the impression that metrics like this are too simple to tell the full story. Burning a gallon of ICE fuel at sea level has a different environmental impact than burning a gallon of jet fuel thousands of meters in the air. I think it might be better to compare in terms of "passenger mile per unit of greenhouse effect" but then how do you even get to agreement on how to measure the greenhouse effect...

Additionally, I don’t think jet engines have to pass clean air standards like cars do. I don’t know for certain that this makes a huge difference for global warming, but there are many vectors for environmental damage besides CO2 emissions. Modern gasoline powered ICE vehicles produce fairly clean exhaust thanks to smog regulations.

Non-CO2 emissions are bad for us now, but their long-term impact on the future is insignificant. They are more bad now precisely because they don't just stick around forever, unlike CO2 they still contain bound energy and will happily participate in all kinds of undesirable reactions.

Re: Aviation industry tries to go green

#65

Post by leetcrew »

anovikov wrote: post #62
benhurmarcel wrote: post #54

Earlier quoted context omitted.

For electric airliners, most promising research centers on hydrogen fuel cells, not batteries. It brings a lot of issues (mainly volume and cooling), but still it's being seriously considered.

Why not just liquid hydrogen, burned in a jet engine? Yes it has density about 12x lower then kerosene, but specific energy is about 3x higher so for the same fuel volume, we get 4x less range. In fact better than that, because of much lower weight and about 2/3 power ratio of fuel burn to aircraft weight and about 40% of weight of a typical plane being fuel, it being gradually burned during flight... it adds about 1…

it solves the greenhouse gas issue, but burning hydrogen still produces NOx.

Re: Aviation industry tries to go green

#66

Post by kypro »

jeromegv wrote: post #58
tonyedgecombe wrote: post #48

Aviation looks like the industry least likely to go green to me. I doubt electric planes are ever going to be viable for anything other than a short hop which would be better done by train. Synthetic fuels sounds interesting until you look at how much fuel they consume. The trend is quite obviously in the wrong direction: https://www.statista.com/statistics/655057/fuel-consumption-... It's often quoted as 2% of globa…

Only solution is to have some type of carbon tax on local travels and use it to reinvest in a train network. A lot of the air flights in North America would be better served by high speed trains. We won’t have an alternative to long distance flights, but there is one for shorter flights.

In Europe train is already quite a nice way to get around.

I live in the UK and caught a train to London then a Eurotunnel train to Paris and it was probably quicker and easier when you account for time spent in departures and going through airport security.

Re: Aviation industry tries to go green

#67

Post by belorn »

jamil7 wrote: post #56

Is a large part of this also a political issue? with subsidies and tax breaks on fuel the aviation industry is not really incentivised to innovate and cosumers are not incentivised to seek other modes of transport since flying is often the cheapest and fastest.

Every single mode of transport is subsidized so its hard to say if air transportation is getting more or less incentives. Using Swedish numbers and some estimates.

Tax on car owners only pay around 1/3 of the road network.

The ticket price on train, according to a person working in that space, said that the ticket paid about 2/3 of the costs that the train company paid for any given trip. The train network also get infusions from time to time by the government, and stations are supported/built using local taxes and fees.

Boats get tax breaks on fuel, and ports are usually subsidized when built. There might also be subsidizes involved in ice breaking, cleaning and management of the waters and channels around ports.

Planes get tax breaks on fuel, and airports are subsidized when built.

Out of those, I would guess that the train system is the least subsidized model but I have nothing to actually support that claim beyond a gut feeling. I would like to see a good summarize of what each sector get and where the money comes from.

Re: Aviation industry tries to go green

#68

Post by dredmorbius »

cgrealy wrote: post #43
JumpCrisscross wrote: post #35

Earlier quoted context omitted.

> big win would obviously be electric aircraft Why batteries over synthetic jet fuel? Hydrocarbons are great for this purpose. The problem is where the carbon is coming from. Burn jet fuel made from atmospheric carbon and you solve the problem overnight.

Simple answer: I wasn't aware of synthetic jet fuel! If it can solve the problem, I'm keen to learn more.

I'd learnt of this a few years ago when the US Naval Research Lab released some papers with a bit of a splash.

The announcements (and references) made this sound like entirely novel technology. In truth it dates in part to WWII and German production of fuel from coal (also practiced by South Africa), and was suggested as an alternative to fossil fuel consumption in the 1960s by M. King Hubbert (of Peak Oil fame) and the Brookhaven National Laboratory.

There's been substantial additional work at Brookhaven, M.I.T., USNRL, and a (failed) Google X-Project attempt.

The fundamental chemistry is sound, scaling and costs are the principle concerns. Costs are strongly influenced by the grotesque underpricing of fossil fuels, by a factor of millions, based on the geological processes of formation. Account properly for those, and the economics straighten out.

(Though much of the present world turns out to be much more expensive than we'd accounted for.)

Numerous posts and references at my subreddit:

https://old.reddit.com/r/dredmorbius/search?q=fischer-tropsc...

Specifically, history of research to the 1960s:

https://old.reddit.com/r/dredmorbius/comments/28nqoz/electri...

Compilation of papers from Heather Willauer et al:

https://old.reddit.com/r/dredmorbius/comments/22k71x/us_navy...

Re: Aviation industry tries to go green

#69

Post by ed_balls »

leetcrew wrote: post #65
anovikov wrote: post #62

Earlier quoted context omitted.

Why not just liquid hydrogen, burned in a jet engine? Yes it has density about 12x lower then kerosene, but specific energy is about 3x higher so for the same fuel volume, we get 4x less range. In fact better than that, because of much lower weight and about 2/3 power ratio of fuel burn to aircraft weight and about 40% of weight of a typical plane being fuel, it being gradually burned during flight... it adds about 1…

it solves the greenhouse gas issue, but burning hydrogen still produces NOx.

Is NOx an issue if it's far away from humans?

Re: Aviation industry tries to go green

#70

Post by lkramer »

kypro wrote: post #66
jeromegv wrote: post #58

Earlier quoted context omitted.

Only solution is to have some type of carbon tax on local travels and use it to reinvest in a train network. A lot of the air flights in North America would be better served by high speed trains. We won’t have an alternative to long distance flights, but there is one for shorter flights.

In Europe train is already quite a nice way to get around. I live in the UK and caught a train to London then a Eurotunnel train to Paris and it was probably quicker and easier when you account for time spent in departures and going through airport security.

but sadly also 2-3 times more expensive.
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