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What if one engine could shrink

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the solar system?

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In The Expanse,

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a single invention does exactly that.

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It's called the Epstein Drive.

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Let's explore it as a thought experiment,

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grounded in real science.

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Optimistic, but possible.

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In the story,

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Solomon Epstein is an engineer on Mars.

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In his spare time,

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he upgrades a fusion engine

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and bolts it

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onto his own small yacht.

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It works far better than anyone expected.

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He doesn't survive the ride,

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but his design does,

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and soon ships everywhere are flying with it.

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So how does it work?

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At its heart is a fusion reactor.

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Tiny bits of fuel are squeezed until

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their atoms fuse,

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releasing a blast of superhot plasma.

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No metal nozzle could touch that,

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so magnetic fields shape it

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into a jet,

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shooting out the back at thousands

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of kilometers per second.

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Real teams are building early cousins:

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the Direct Fusion Drive at Princeton,

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Pulsar Fusion's Sunbird,

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and the magnetic nozzle

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of the VASIMR engine.

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The hardest part isn't thrust.

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It's heat.

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Pushing a big ship

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at 1 g takes trillions of watts,

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and even a tiny leak could melt it.

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The smart trick is to let

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the exhaust carry the heat away.

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Fuels like helium-3 release most

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of their energy as charged particles,

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which magnets steer straight out the back.

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What's left goes to glowing radiators,

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or even sprays of liquid metal droplets

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that cool off in space

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and get caught again.

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Now the fun part:

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flip and burn.

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Speed up for the first half

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of the trip,

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flip around, and brake

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for the second half.

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Travel time is two times

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the square root of distance over acceleration.

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Today, Mars takes about seven months.

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At 1 g, it takes two

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to five days.

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At 1.5 g, about

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the most people can handle for days,

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it's under four.

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Even Saturn is about a week away,

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and the whole time,

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thrust feels like gravity.

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In the books and the show,

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people settle the Moon and Mars first, slowly.

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Then the drive arrives,

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more than a century before

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the main story,

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and humanity rushes outward:

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to Ceres and the asteroid Belt,

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then the moons of Jupiter and Saturn.

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Faster travel reshapes politics.

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Earth, Mars, and the Belters become three

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powers, trading, competing,

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and arguing over who's in charge.

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Now our twist.

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What if Mars invents the drive first, around 2090?

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Martians want fast travel more than anyone.

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But Mars can't build

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a migration fleet alone.

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So it licenses the design

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to Earth's shipyards,

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and trades it for early self-rule.

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Earth builds ships,

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Mars gets its independence,

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and the Belt opens about

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a century early.

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To compare, we built

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a simple population model.

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It's a model,

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not a forecast:

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birth rates, room to live,

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and how many people ships can carry.

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Without the drive,

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only a few million people live off

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Earth by 2200.

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With a Martian drive in 2090,

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it's over a hundred million,

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and the Belt passes one million people

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by about 2145.

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With AI speeding up research,

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this timeline might even be conservative.

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Designs, simulations, and new materials could all arrive faster.

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But some things AI can't rush:

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building fleets, growing food,

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and raising generations of kids

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in low gravity.

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Those take real time and real people.

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So, optimistic?

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Definitely.

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Possible?

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Let's go find out.