These New Technologies Could Make Interstellar Travel Real

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These New Technologies Could Make Interstellar Travel Real

Ion the Prize

While Brophy was pondering this impasse between efficient engines and insufficient solar power, the Breakthrough Starshot concept came out, and it got the gears turning in his head. He wondered: What if you replaced sunshine with a high-intensity laser beam pointed at your spacecraft? Powered by the more efficient laser, your ion engine could run much harder while still saving weight by not having to carry your power source on board.

Two years after his epiphany, Brophy is giving me a tour of an SUV-size test chamber at JPL, where he puts a high-performance ion engine through its paces. His prototype uses lithium ions, which are much lighter than the xenon ions Dawn used, and therefore need less energy to attain higher velocities. It also runs at 6,000 volts compared with Dawn’s 1,000 volts. “The performance of this thing would be very startling if you had the laser to power it up,” he says.

There’s just one minor issue: That laser does not exist. Although he drastically downsized the Starshot concept, Brophy still envisions a 100-megawatt space-based laser system, generating 1,000 times more power than the International Space Station, aimed precisely at a fast-receding spacecraft. “We’re not sure how to do that,” he concedes. It would be by far the biggest off-world engineering project ever undertaken. Once built, though, the array could be used over and over, with different missions, as an all-purpose rocket booster.

As an example, Brophy describes a lithium-ion-powered spacecraft with 300-foot wings of photovoltaic panels powering a full-size version of the engine he is developing at JPL. The laser would bathe the panels in light a hundred times as bright as sunshine, keeping the ion engine running from here to Pluto, about 4 billion miles away. The spacecraft could then coast along on its considerable velocity, racking up another 4 billion miles every year or two.

At that pace, a spacecraft could rapidly explore the dim areas where comets come from, or set off for the as-yet-undiscovered Planet 9, or go . . . almost anywhere in the general vicinity of the solar system.

“It’s like we have this shiny new hammer, so I go around looking for new nails to pound in,” Brophy says dreamily. “We have a whole long list of missions that you could do if you could go fast.”

Interstellar Medium Well

After Brophy’s genial giddiness, it is a shock to talk to Alkalai, in charge of formulating new missions at JPL’s Engineering and Science Directorate. Sitting in his large, glassy office, he seems every bit the no-nonsense administrator, but he, too, is a man with an exploratory vision.

Like Brophy, Alkalai thinks the Breakthrough Starshot people have the right vision, but not enough patience. “We’re nowhere near where we need to be technologically to design a mission to another star,” he says. “So we need to start by taking baby steps.”

Alkalai has a specific step in mind. Although we can’t yet visit another star, we can send a probe to sample the interstellar medium, the sparse gas and dust that flows between the stars.

“I’m very interested in understanding the material outside the solar system. Ultimately, we got created from that. Life originated from those primordial dust clouds,” Alkalai says. “We know that there’s organic materials in it, but what kind? What abundances? Are there water molecules in it? That would be huge to understand.”

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