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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

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.

Symmetry 8y ago
On the other hand those green men on Mars can get off their planet pretty easily with just a single stage.
Florin_Andrei 8y ago
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.
- knodi123 8y ago
  > 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!
  - glandium 8y ago
    What if they're immune to radiation?
  - Florin_Andrei 8y ago
    > 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 https://en.wikipedia.org/wiki/NERVA
    - extrapickles 8y ago
      ‘Project Orion’ is the spew out a stream of nuclear bombs propulsion technique.
    - exrook 8y ago
      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_propulsion%29 https://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propu...
tedsanders 8y ago
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.
- inteleng 8y ago
  There is a point where surface gravity is sufficiently high that in order to put a few kilograms in orbit the "rocket" would have to weigh as much as the entire planet, even if you use the most efficient chemical fuel we've invented. Physics doesn't lie.

Symmetry 8y ago

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

Florin_Andrei 8y ago

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.

knodi123 8y ago
> 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!
- glandium 8y ago
  What if they're immune to radiation?
- Florin_Andrei 8y ago
  > 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 https://en.wikipedia.org/wiki/NERVA
  - extrapickles 8y ago
    ‘Project Orion’ is the spew out a stream of nuclear bombs propulsion technique.
  - exrook 8y ago
    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_propulsion%29 https://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propu...

tedsanders 8y ago

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.

inteleng 8y ago
There is a point where surface gravity is sufficiently high that in order to put a few kilograms in orbit the "rocket" would have to weigh as much as the entire planet, even if you use the most efficient chemical fuel we've invented. Physics doesn't lie.