Why nuclear makes sense for the Red Planet. Google’s new memory math for AI. Why video games help you sleep. All that and more in this week’s edition of The Prototype. To get it in your inbox, sign up here.

NASA has added an ambitious mission to Mars to its agenda. By the end of 2028, it plans to launch SR-1 Freedom, a spacecraft equipped with nuclear electric propulsion (NEP), to the Red Planet. Once there, it will release a swarm of autonomous helicopters (like the Ingenuity copter that flew with Perseverance) tasked with scouting for water and safe landing zones for future crewed missions.

The spacecraft will be powered by a 20-kilowatt nuclear reactor, using uranium to generate intense amounts of heat that are moved through a turbine to be turned into electricity. A conventional rocket creates an intense burst of acceleration for a spaceship, which then coasts on inertia the rest of the way. By contrast, this spacecraft will generate less intense, but continuous, acceleration–building up speed over the course of the journey.

The bottom line for NEP is that it's theoretically much more efficient. One of the biggest constraints in launching spaceships is the fuel: it’s heavy, and the more you have, the harder it is to escape Earth’s gravity. The weight of the propellant needed with NEP is a fraction of that needed in a conventional spacecraft, explained Nikolaos Gatsonsis, a professor of aerospace engineering at Worcester Polytechnic Institute.

One challenge in getting that efficiency is whether the reactor can be built small enough to actually save on weight, Ray Sedwick, an aerospace engineer at the University of Maryland, explained to me. “Reactors designed to operate in space have many additional technical challenges, not the least of which is keeping the mass down. Saving on propellant mass only helps if your power plant mass doesn’t end up being more massive than what you save.” One source of mass, he said, would be the radiators necessary to dissipate any heat that isn’t used to generate power.

Another challenge for NASA’s ambitious timeline, Gatsonis said, is that a nuclear reactor has never been integrated into an electrically propelled spacecraft before. That said, he notes that 20-kilowatt non-nuclear systems have been demonstrated before, and Sedwick added that this spacecraft is “leveraging a lot of heritage technology.” So that 2028 timeline might be doable “if the development momentum can be maintained.”

Discovery of the Week: Google’s New Memory Shortu

Last week, we talked about how a halt in shipping in the Strait of Hormuz could make AI more expensive. (To recap: AI needs memory chips. Memory chip manufacturers need helium. They mostly get that helium from Qatar. Thanks to the Iran war, they can’t get it.) But researchers at Google may have just developed a way to ease that bottleneck: On Tuesday, the company unveiled TurboQuant, a set of algorithms that enable significant memory compression for the key-value cache of search engines and large language models.

AI systems utilize high-dimensional vectors in order to function. These are complex mathematical........

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