Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asking the reason alien civilizations might be rare is because most aliens are huge.

To hear it and every episode early and ad-free, plus hours of bonus content, check out

go.nebola.tv slash Isaac Arthur and use my code, Isaac Arthur.

The Medusa Starship Drive offers us the chance to sail between the stars, propelled by nuclear bombs.

The amount of energy released from a kilogram of an atomic bomb dwarfs what an equal amount

of chemical fuel would release by a factor of around a million, and fusion bombs even

more so.

Thus it's no surprise we've contemplated nuclear energy methods for running spaceships, but

sometimes it can't surprise folks that we've considered running those ships on

actual atom bombs, rather than, say, a nuclear reactor and an ion drive.

Nonetheless, the nature of high-powered proportion is that it tends to be decidedly explosive,

and you would be safe or standing near several hundred pounds of explosives going off at once

the next to your typical rocket flame.

The other problems that a nuclear reactor is a heavy thing compared to a bomb, and converts

its energy into boiling water to turn a turbine and produce electricity, and then run some

form of electric propulsion like an ion drive, and tends to lose a lot

of that compactness and low mass advantage that Sidi Alpha bomb has.

What's more, while we have fission bombs and fission reactors, we don't have fusion

reactors, just the bombs, and fusion is more compact than fission.

For this reason, we have spaceship designs that seek to run on nukes.

The best known is the Orion Drive, which use an immense pusher plate on a spring behind

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