XKCD What if: Everybody Out

[PakledHostage]

Interesting reading: XKCD: Is there enough energy to move the entire current human population off-planet?

[dt890]

"blow ourselves off the planet with nuclear weapons" cant find it possible at all, simply because such a huge explosion to get anyone in to orbit would produce so strong g-forces that even if the ship holds we wouldn't.

or am i missing something ?

[Ziff]

Well, it wouldn't be 1 big nuclear blast. It would be many smaller nuclear blasts, somewhere around 500-1000 small .03kt bombs or something like that.

[Johno]

The key is the design of the spacecraft.

With a spacecraft with that much thrust, a lot of the design is a little counter intuitive to us, because we're used to chemical rockets.

On a chemical rocket, weight is always a concern (because of the large quantity of heavy liquid fuel you need to carry, and its relatively modest thrust).

On a nuclear bomb-rocket, though, thrust is seldom a problem; in fact, the problem is (as you pointed out) that the massive thrust of a bomb will lead to an acceleration that would convert the average human to a sort of gristly, splotchy pancake.

The good news is that there is a simple solution - Newton's second law tells us that F=ma. So if we wish to decrease the acceleration on our crew with a given force, all we have to do is to increase the mass! For a manned spacecraft of this kind, therefore, the weird fact is that a big heavy spacecraft is better than a small light one.

[Ydoow]

I almost feel like that first part should be copied and pasted in the "How To" section, the part dealing with computations of Delta V. And then point out that the way he calculate the necessary amount of fuel was just the Tsiolkovsky Rocket equation rearranged for those unfamiliar with rearranging ln equations (took me a minute to realize it XD ).