Hello, SFIA audio listeners, in this month's Nebula exclusive, Big Alien Theory,

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

To hear it and every episode early and add free, plus hours of bonus content,

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

This episode is brought to you by Brilliant.

Interstellar space is beyond enormous.

In order to travel between the stars, we will need the power of the stars.

So today we'll be taking a look at spaceship propulsion focusing on fusion-based drives and we'll be looking at both the various possible fusion drive systems and what

they would really mean in practical terms.

In that regard we will discuss the possible speed such ships might obtain and what sort

of cost we might see for passengers or cargo, both for interplanetary travel and interstellar

travel, though for the latter especially we will have to be rather speculative.

This is not our first time discussing fusion as a power source, so we will skim over some

of the basic function and economic impacts that we explore in our fusion power and impact of nuclear fusion episodes,

but we have several different fusion drive scenarios and each will look very different.

The key ones we will consider for today will be fusion torch drives versus fusion-powered

ion drives, the Bucarred Ramjet, Deuterium-based fusion, helium-3

fusion, plane hydrogen fusion, and pulsed fusion, which is essentially shooting hydrogen bombs

out behind a ship.

The last one, Pulse Fusion, is the only one we currently have the technology for and folks

are not overly anxious to construct a ship to Mars

or Alpha Centauri that would leave Earth's orbit with a cargo bay full of nuclear bombs,

...