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Pharisaeus t1_iwmh05m wrote

Reply to comment by oh-propagandhi in Ask Anything Wednesday - Engineering, Mathematics, Computer Science by AutoModerator

> we don't have nearly enough rocket fuel

This is completely wrong. Consider that many rockets fly using hydrolox engines -> they burn hydrogen and oxygen (in fact this is the most energetic bi-propellant mixture!). And you can get those by... splitting water :) So no, we're definitely not missing rocket fuel.

The issue is more about how inefficient this is, because fuel is heavy. It's sometimes called "tyranny of rocket equation". Adding more and more fuel to your rocket very quickly no longer provides any gains, because most of the fuel is wasted on lifting the fuel itself. Some sci-fi idea (but founded in science!) how this could be fixed would be to use matter-antimatter as fuel, because the amount of energy you can get from tiny amount of mass is huge.

> Have there been any new discoveries that are leading us to getting off the planet with fewer or different resources needed?

There are some crazy ideas like SpinLaunch, and some new rockets are working with methane instead of kerosene or hydrogen, but this is not really any special "revolution".

There is some new interest in nuclear-thermal rockets, but those are more interesting for travelling around the solar system and not lifting from the ground.

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oh-propagandhi t1_iwminsg wrote

I was slightly mistaken, it was "Enough to get everyone off the earth comfortably" like a Wall-e type scenario.

Thanks for the insight!

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noiamholmstar t1_iwq9yje wrote

In addition to the other poster, you have to think about how much other stuff you need to lift into space per person. If each person needs about a metric ton of stuff in order to survive once they're in space, then we would need to launch 8 billion tons of stuff into space. And that's not counting the mass of the vehicle to get them into space. Even if we figured out how produce enough antimatter and how to reliably contain it and use it as a fuel, thats still an epically large amount of mass to lift into orbit. Just building the ships and infrastructure to fuel and launch them would be a monumental task. It's as much an economic/labor/political challenge as an engineering one.

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oh-propagandhi t1_iwqcsxg wrote

Thanks for the insight. That's more what I was talking about. It's the thing that made me realize that space exploration is neat and important, but it's currently statistically meaningless to my life and the life of even my kids as far as a sci-fi type scenario where we all just kick around in space with our space dogs or whatever.

That's before you get into all the "not supporting life" problems of every other body in our solar system, and the "can't get out of the solar system with current tech" problem.

It's a hard splash of reality and I'm mostly curious about any new news on breaking that barrier where jet setting around space becomes a reality.

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