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Agreed. When I learned that bit about the rocket equation and gravity - that just a little more gravity would make all known rocket tech unable leave Earth's at

by ianai 6y ago

Agreed. When I learned that bit about the rocket equation and gravity - that just a little more gravity would make all known rocket tech unable leave Earth's atmosphere/gravity - my thoughts of life zipping around the universe dimmed greatly. Maybe we should look at it as our duty to devise ways to 'rescue' other biomes from their gravitational jails? (if only we weren't space orcs.)

fiftyfifty 6y ago
I've always thought something like the Skyhook described in Seveneves by Neal Stephenson would be perfect for lifting things off of high gravity worlds where the rocket equation is a deal breaker, provided you were starting in orbit or outside of the gravity well: https://news.ycombinator.com/item?id=17900992 https://news.ycombinator.com/item?id=17900992 Maybe the materials science would still be a deal breaker, but in theory it would be easier to build than a space elevator.
- ianai 6y ago
  Huh, very interesting. Yes, I wonder where current materials engineering puts us for a maximum length cable. It might be usable to just fly a plane up to it at some point. This also brings to mind capturing an asteroid in LEO. (Surely super dangerous though.) I can't help but think SpaceX and the rest of us are missing out by targeting places like the moon or mars when there are so many asteroids out there. Maybe some of them could be used as a space station or slowly morphed into a spaceship with higher mass than we could ever launch? (like 1036 ganymed)
  - fiftyfifty 6y ago
    If we ever start really living and working in space it seems like we might reach a point where going down into deep gravity wells like Earth or even Mars will be too expensive to be worth it most of the time.
nwah1 6y ago
Just because traditional combustion engines can't do it doesn't mean much. More powerful nuclear thermal engines, direct fusion engines, etc are in development. There's other possibilities.
- simonh 6y ago
  That’s true to a point, but it’s undeniable that as the cost of space technology increases the odds of bothering with it fall, and that the relatively modest changes in the conditions have exponential impact on the costs. A small increase in gravity rules out chemical rockets. Yes nuclear rockets might still be viable at that point, but increase gravity a bit more, or atmospheric density, and those become unviable too. And so it goes. The point is the range of conditions in which space tech is viable is very narrow compared to the range of possible conditions a species might find itself in.

by ianai 6y ago

fiftyfifty 6y ago

I've always thought something like the Skyhook described in Seveneves by Neal Stephenson would be perfect for lifting things off of high gravity worlds where the rocket equation is a deal breaker, provided you were starting in orbit or outside of the gravity well: https://news.ycombinator.com/item?id=17900992 https://news.ycombinator.com/item?id=17900992 Maybe the materials science would still be a deal breaker, but in theory it would be easier to build than a space elevator.

ianai 6y ago
Huh, very interesting. Yes, I wonder where current materials engineering puts us for a maximum length cable. It might be usable to just fly a plane up to it at some point. This also brings to mind capturing an asteroid in LEO. (Surely super dangerous though.) I can't help but think SpaceX and the rest of us are missing out by targeting places like the moon or mars when there are so many asteroids out there. Maybe some of them could be used as a space station or slowly morphed into a spaceship with higher mass than we could ever launch? (like 1036 ganymed)
- fiftyfifty 6y ago
  If we ever start really living and working in space it seems like we might reach a point where going down into deep gravity wells like Earth or even Mars will be too expensive to be worth it most of the time.

nwah1 6y ago

Just because traditional combustion engines can't do it doesn't mean much. More powerful nuclear thermal engines, direct fusion engines, etc are in development. There's other possibilities.

simonh 6y ago
That’s true to a point, but it’s undeniable that as the cost of space technology increases the odds of bothering with it fall, and that the relatively modest changes in the conditions have exponential impact on the costs. A small increase in gravity rules out chemical rockets. Yes nuclear rockets might still be viable at that point, but increase gravity a bit more, or atmospheric density, and those become unviable too. And so it goes. The point is the range of conditions in which space tech is viable is very narrow compared to the range of possible conditions a species might find itself in.