this post was submitted on 08 Sep 2023
444 points (96.4% liked)

Confidently Incorrect

3986 readers
1 users here now

When people are way too smug about their wrong answer.

Posting guidelines.

All posts in this community have come from elsewhere, it is not original content, the poster in this community is not OP. The person who posts in this community isn’t necessarily endorsing whatever the post is talking about and they are not looking to argue with you about the content in the post.

You are welcome to discuss and debate any topic but arguments are not welcome here. I consider debate/discussions to be civil; people with different opinions participating in respectful conversations. It becomes an argument as soon as someone becomes aggressive, nasty, insulting or just plain unpleasant. Report argumentative comments, then ignore them.

There is currently no rule about how recent a post needs to be because the community is about the comeback part, not the topic.

Rules:

• Be civil and remember the human.

• No trolling, insults or name calling. Swearing in general is fine, but not to insult someone.

• No bigotry of any kind, including homophobia, transphobia, sexism and racism.

• You are welcome to discuss and debate any topic but arguments are not welcome here. I consider debate/discussions to be civil; people with different opinions participating in respectful conversations. It becomes an argument as soon as someone becomes aggressive, nasty, insulting or just plain unpleasant. Report argumentative comments, then ignore them.

• Try not to get too political. A lot of these posts will involve politics, but this isn’t the place for political arguments.

• Participate in good faith - don’t be aggressive and don’t argue for arguements sake.

• Mark NSFW posts if they contain nudity.

• Satire is allowed but please start the post title with [satire] so other users can filter it out if they’d like.

Please report comments that break site or community rules to the mods. If you break the rules you’ll receive one warning before being banned from this community.

This community follows the rules of the lemmy.world instance and the lemmy.org code of conduct. I’ve summarised them here:

  1. Be civil, remember the human.
  2. No insulting or harassing other members. That includes name calling.
  3. Respect differences of opinion. Civil discussion/debate is fine, arguing is not. Criticise ideas, not people.
  4. Keep unrequested/unstructured critique to a minimum.
  5. Remember we have all chosen to be here voluntarily. Respect the spent time and effort people have spent creating posts in order to share something they find amusing with you.
  6. Swearing in general is fine, swearing to insult another commenter isn’t.
  7. No racism, sexism, homophobia, transphobia, xenophobia or any other type of bigotry.
  8. No incitement of violence or promotion of violent ideologies.

founded 1 year ago
MODERATORS
 
you are viewing a single comment's thread
view the rest of the comments
[–] marcos@lemmy.world 1 points 1 year ago (1 children)

but you’ll notice they tend to leak like crazy

OGM. No, the thing you can see is condensation from the atmosphere. You can't see an hydrogen leak in any reasonable environment.

Guess what? Leaking is a long term problem, and not very relevant if you refuel just before your trip. Its balance for airplanes is all dictated by the needs of a high-pressure storage against the unbeatable energy density. Up to now, hydrogen has always lost, and will probably keep losing for most airplanes, but commercial aviation is constantly pushing over factors that change the equilibrium towards it.

[–] jarfil@lemmy.world 2 points 1 year ago* (last edited 1 year ago)

Condensation is one thing, hydrogen leaking straight through the metal is another.

https://en.m.wikipedia.org/wiki/Hydrogen_embrittlement

It isn't a problem if you fill up a container with liquid hydrogen right before your trip, the trip lasts less than an hour, then you discard the container and let it burn up on reentry.

It is a problem though, if you intend to fill up the same container multiple times, keep hydrogen in it for hundreds of hours, and subject it to vibrations.

Another problem is that even in its liquid state, while the energy density to weight ratio is great, its energy density per volume is pitiful:

Meaning, a plane could carry the same energy in 3 times less weight of fuel, which is great, but still need 8 times larger deposits to do it, which would mess up the aerodynamics... and would still have a high chance of springing a leak.

It's no coincidence that SpaceX is using liquid methane for its reusable rockets.