Gromit and I started a conversation on Twitter last night, but 140 character messages aren't enough to do the subject justice, so I've moved it here.

"To Mars by A-Bomb" was on BBC Four last night. It's a film based on George Dyson's book about his father's involvement with Project Orion. His father is Freeman Dyson (yes, as in "Dyson Sphere") and Project Orion was about building a spaceship the size of an ocean liner, which would have had a propusion system based on dropping an atom bomb out of the back every ten seconds or so, and setting it off. It was an idea that could only have come from the late 1950s.

The documentary featured film of what Dyson refers to in the accompanying book as "the Hot Rod" - a scale model a couple of feet high powered by half-pound lumps of plastic explosive. The damn thing worked.

Imagine something the size of a battleship rising into the air: bang! bang! bang! As altitude increased, they were going to up the yield of the bombs. But once the effects of fallout became known, Dyson calculated that each launch would result in between 10 and 100 fatalities, which was of course unacceptable. The project was killed.

Even today, Dyson Sr can't tell his son all about the project. The mechanics of delivering reliable, small nuclear devices is understandably still highly classified...

Basic Background on the project

Clip from the show

George Dyson at TED

Gromit asked me why they couldn't launch from orbit; the main reason was the sheer mass of the ship. If you're using a nuke for propulsion, the specific impulse is *huge* - the heavier you can make the ship, the better. In the book they talk about fitting out the ship with cast-iron dentists chairs, because they were the heaviest seating they could find. If you can't use nukes in the atmosphere, you've got to carry all that mass up out of the gravity well.

Of course, you wouldn't kill people if you built the thing on the Moon instead; launch would be much easier, and you'd have plenty of empty real estate underneath to irradiate without killing anyone.

Who knows? Maybe in a hundred years, that's how we'll get to the outer planets...

best,
Chris H

quote:

Originally posted by Chris H:
"To Mars by A-Bomb" was on BBC Four last night.

Ha, so I wasn't the only one who saw that!

It was like people read a 50's sci-fi novel and tried to turn it into reality. Brilliant.

I loved the maths behind it.

So, an atomic bomb produces that much power X, if we want to accelerate by not more than v0 of 30mph how heavy does the thing have to be?
Ohh, as heavy as an ocean liner ... okay. Now how many nuclear bombs do we need to get something that heavy from earth. 2 a second, 1000 in total.

Hmm... so we need to mass produce a-bombs than. Lets talk to CokaCola, they are good in mass producing stuff!

quote:

Hmm... so we need to mass produce a-bombs than. Lets talk to CokaCola, they are good in mass producing stuff!

LOL!!