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Comment by koverda | Hacker News Reader

Nice that we live on a planet with low enough gravity to get off of it. The article states that if the Earth was about 50% bigger, chemical rockets wouldn't be able to achieve escape velocity. Any species on a planet like that has a much much harder time getting into space.

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We almost had a nuclear space program. It got cancelled for non-technical reasons. On a planet with harder take-off, that program would get all the funds it could possibly need.

> We almost had a nuclear space program.

built on the success of a rocket-based program! no way would a country fund a vehicle that spews out a constant stream of nuclear bombs as their species' first foray into orbit!

What if they're immune to radiation?

> a vehicle that spews out a constant stream of nuclear bombs

That's not how the NERVA was supposed to work.

https://en.wikipedia.org/wiki/NERVA

‘Project Orion’ is the spew out a stream of nuclear bombs propulsion technique.

I believe the GP is referring to Project Orion[0], which did propose using repeated nuclear detonations behind a spacecraft to propel it forward.

[0] https://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propu...

I once mentioned this to an old NASA engineer who worked on the moon landings. He corrected me and pointed out that it's still possible to launch - you would just need more staging. Obviously at very high levels of gravity, the staging requirements would be extreme. I'm not sure what it would be if Earth was 50% bigger. Maybe someone can do the math or share a link to a page that's done it already.

On the other hand those green men on Mars can get off their planet pretty easily with just a single stage.

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