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   Non-TechAirline Discussion Board


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From: Moonray10/19/2021 4:26:04 PM
1 Recommendation   of 1700
 
Delta (DAL) Raises Fuel Cost Alarm: Other Airlines to Follow?

__Symbol__Last__Change__Chg %
UAL

46.22-0.95-2.01%
SKYW

47.90-0.84-1.72%
SAVE

23.37-0.15-0.64%
LUV

49.38-0.39-0.78%
JBLU

14.90-0.06-0.40%
HA

20.42-0.32-1.54%
DAL

40.45-0.56-1.37%
ALK

56.94-0.48-0.84%
AAL

19.53-0.31-1.56%
JETS

23.09-0.25-1.07%

o~~~ O

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To: Sam who wrote (1648)10/25/2021 3:48:53 PM
From: Moonray
1 Recommendation   of 1700
 
Unvaccinated Americans to face tighter COVID-19
testing requirements in new US travel system

o~~~ O

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From: Moonray10/25/2021 10:48:59 PM
1 Recommendation   of 1700
 
CDC moves large European country to
its highest level of Covid-19 travel risk

o~~~ O



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From: Moonray10/26/2021 9:31:06 PM
   of 1700
 
Federal judge rejects Southwest Airlines
pilots’ request to block vaccine mandate

o~~~ O

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To: OldAIMGuy who wrote (1636)10/27/2021 1:20:17 PM
From: Moonray
2 Recommendations   of 1700
 
Commercial flights that fly ‘entirely on hydrogen’ planned for 2024

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To: Moonray who wrote (1657)10/27/2021 2:57:32 PM
From: TimF
2 Recommendations   of 1700
 
With the short time frame (a bit over two years to three years) and the small capacity it seems like a demonstration more than anything meaningful.

Hydrogen does have some serious advantages (in addition to what is probably the motivation, the fact that perfect burning of Hydrogen doesn't emit CO2). Its abundant in the universe, and in compounds (for example water) its abundant on Earth. It also has a lot of energy per weight.

But its difficult to handle and transport. Its density is very low. Store it as a gas and you need huge tanks. Store it as a liquid and it still needs tanks over three times as large as jet fuel or gasoline or diesel, and you also have to store it at more than 423 degrees below zero (or slightly higher with some pressure but still a cryogenic temperatures). Its escapes easily from containment so you lose some of it why you store it (even stored for use in the tank of a vehicle that's burning it) or transporting it. And when it escapes it can (depending on how its stored) cause en.wikipedia.org, or under some conditions en.wikipedia.org

Its low molecular and atomic weight and high energy to weight ratios do make it a good fuel for spacecraft (or it can be reaction mass for spacecraft that don't rely on burning it), and it has some other niche applications, but I don't think it will have any wide spread transportation use any time soon (spacecraft being a small enough proportion of transportation to not count as "wide spread").

Its use doesn't even necessarily reduce CO2 emissions because currently most hydrogen is generated from fossil fuels.

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To: TimF who wrote (1658)10/27/2021 3:25:25 PM
From: Moonray
   of 1700
 
You forgot to add that hydrogen has been tried on flights before,
some 85 years ago. You wouldn't have to show this video to a person
getting on a commercial flight more than once to allow many to change
their minds, rightly or wrongly.



o~~~ O

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To: Moonray who wrote (1659)10/27/2021 4:21:04 PM
From: TimF
1 Recommendation   of 1700
 
Hydrogen isn't necessarily more dangerous than other fuels. The issue with that accident was that the majority of the volume of the vehicle was fuel. Which isn't normally the case (except maybe with rockets, or with tankers transporting fuel).

And it wasn't even fuel they would burn to propel the airship forward. The Hindenburg had 4 diesel engines, which may have even been the cause of the fire (directly, or through their fuel being the source). There are other theories, such as static buildup, a lightning strike, or even sabotage.

I guess even if its just fuel (and not a lifting gas) the large storage space needed for hydrogen gas might reduce safety, it might be harder to properly isolate a very large tank from static or other threats. If your using liquid hydrogen then you have the possibility of failure of the cooling method for your cryogenic storage (although the tank would still be highly insulated, you wouldn't get a sudden shift to all gas, you would just have to vent some of the gas as it develops to avoid over-pressure)

OTOH hydrogen also has some safety advantages. Its lightness means it flows away in to the sky as it burns which usually causes less damage to things around it. It also normally produces a lot less harmful gases and smoke around the fire then conventional fuels (a perfect hydrogen/oxygen fire would just produce steam, so it would "no harmful gasses and smoke" but in the real world you have other objects and gasses around to burn).

Here is a video with some tests

Experimental Investigation of Liquid Hydrogen Hazards, 1960, Film Number 1

youtube.com

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To: Moonray who wrote (1659)10/27/2021 4:23:02 PM
From: Art Bechhoefer
   of 1700
 
The distance between Rotterdam and London, the two cities involved in the project, is about 100 miles. Even if hydrogen requires comparatively large storage tanks, the short distance makes hydrogen powered fuel cells practical, though probably at greater cost than, for example, a jet prop aircraft with some 19 passengers.

Art

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To: Moonray who wrote (1657)10/28/2021 9:05:40 AM
From: OldAIMGuy
1 Recommendation   of 1700
 
Hi M, Re: Hydrogen fueled aircraft....................

The problem isn't with the technology to use hydrogen to create motive power. The problem comes from creating a source of hydrogen that isn't impacting the environment to a worse degree than a carbon based fuel itself.

Sources of hydrogen are either hydrocarbon based or electrolysis based. Hydrocarbon based systems for generation hydrogen are endothermic (they use more energy than they create) and therefore not practical and also liberate CO². Electrolysis is just plain energy intensive no matter what the source.

It's tough to bypass the laws of thermodynamics!

Best wishes,
OAG Tom

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