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With all these “green” airplane startups I’m so completely unconvinced by the “electric” battery powered and hydrogen powered ones. The energy density for the b

With all these “green” airplane startups I’m so completely unconvinced by the “electric” battery powered and hydrogen powered ones. The energy density for the battery’s and safety for hydrogen just isn’t feasible. I believe the only carbon neutral route forward for air travel is a carbon natural synthetic hydrocarbon fuel that is as close to current fuels as possible. It gets us the energy density needed and builds upon the 100 years of development the engines have had. Siemens Energy and Shell are both putting significant energy (pun intended) into R&D around these.

AYBABTME 5y ago
What's the main safety concern for hydrogen?
- paranoidrobot 5y ago
  As others have mentioned here, it is difficult to keep contained, and because it's not very dense at room temperature/low pressures. So the example FTA given is cryogenic cooling. Because of the extreme cold, this can lead to new failure modes for materials. The other issue is that hydrogen when it burns has a very pale blue flame that can be difficult to impossible to see during daylight. It also apparently has a low radiant heat, which makes it difficult to feel from a distance. This makes firefighting and safety a major concern. The first you might know of a hydrogen fire, is that you're suddenly on fire yourself.
- ncmncm 5y ago
  In confined spaces, mixed with air within a range of concentrations, it is explosive. So, hydrogen systems will need continuous positive airflow around them so that the partial pressure of any leaked hydrogen is kept at all times well below the point of ignitability. You start with the assumption that hydrogen will be leaking everywhere (because it does) and design so that it doesn't matter.
dr_dshiv 5y ago
And offsets. Everything needs offsets. Even green supply chains.
feistypharit 5y ago
I’m working on my private pilot license. Recently learned the most common AV fuel in the US is 100LL. 100 octane Low lead. That’s right, it has lead! Commercial jet fuel doesn’t, but all those small planes you see running around (and that I’m training in) are running leaded gas. It was supposed to be phased out by 2018, but reasons…

AYBABTME 5y ago

What's the main safety concern for hydrogen?

paranoidrobot 5y ago
As others have mentioned here, it is difficult to keep contained, and because it's not very dense at room temperature/low pressures. So the example FTA given is cryogenic cooling. Because of the extreme cold, this can lead to new failure modes for materials. The other issue is that hydrogen when it burns has a very pale blue flame that can be difficult to impossible to see during daylight. It also apparently has a low radiant heat, which makes it difficult to feel from a distance. This makes firefighting and safety a major concern. The first you might know of a hydrogen fire, is that you're suddenly on fire yourself.
ncmncm 5y ago
In confined spaces, mixed with air within a range of concentrations, it is explosive. So, hydrogen systems will need continuous positive airflow around them so that the partial pressure of any leaked hydrogen is kept at all times well below the point of ignitability. You start with the assumption that hydrogen will be leaking everywhere (because it does) and design so that it doesn't matter.

dr_dshiv 5y ago

And offsets. Everything needs offsets. Even green supply chains.

feistypharit 5y ago

I’m working on my private pilot license. Recently learned the most common AV fuel in the US is 100LL. 100 octane Low lead. That’s right, it has lead! Commercial jet fuel doesn’t, but all those small planes you see running around (and that I’m training in) are running leaded gas. It was supposed to be phased out by 2018, but reasons…