Bimodal Nuclear Engine Could Speed Mars Trip

One day in 1982, Joseph “Rod” Canion and two colleagues from Texas Instruments sat down at the House of Pies in Houston and used a napkin to sketch out what would become Compaq’s portable PC. In 1996, Felix Zandman, founder of Vishay Intertechnology, dined at Husker Steak House in Columbus, Neb., grabbed a napkin and drafted a design for a power metal strip resistor, which became crucial to power-management components in industrial, automotive, and consumer applications. Now that wispy piece of paper resides at the Smithsonian’s National Museum of American History. Perhaps most famously, Robert Metcalfe, working at Xerox PARC in 1973, roughed out some early designs for what would become the [?] Ethernet, though contrary to popular belief, no napkin was involved.

Yet another napkin was pressed into service last year, when Kurt Polzin, chief engineer of the space nuclear propulsion project at NASA’s Marshall Space Flight Center, met Robert Schleicher of General Atomics Electromagnetic Systems at a conference and started talking about nuclear rocket design.

“They did the classic let’s-sketch-out-an-idea-on-a-napkin,” says IEEE Spectrum’s Special Projects Editor and our in-house spaceflight expert Stephen Cass. “This rocket engine is still at the paper-planning stage, which, to be fair, is where most of NASA’s humans-to-Mars planning has been for the last 60 years.”

Meanwhile, the world’s richest person is pushing for humans to colonize Mars in time for him to escape our hospitable blue marble for a completely barren red planet. One big problem with this idea: It takes a long time in hostile space to get there.

“Here’s our napkin. Noodle on this with us and tell us what you think.” —Stephen Cass

There’s an old saw, mostly used in the context of road safety, that speed kills. But when it comes to sending humans on interplanetary missions, the faster the better. As Cass pointed out, “Once you get outside the Van Allen belts, there’s so much natural radioactivity—that’s the real killer.” Nuclear electric propulsion could both minimize launch costs and the time fragile human bodies are subjected to microgravity and radiation. And that makes a synchronal bimodal nuclear engine that could both power and propel a spaceship an attractive alternative to a conventional rocket.

Polzin and Schleicher think their nuclear engines could halve the time it takes to get to Mars. There may be ways to tweak the design to go even faster and further. But for now, the idea sits on the drawing board, awaiting feedback and refinement.

“They’re pulling together a lot of fairly mature technology,” says Cass, who edited Polzin and Schleicher’s article, “A Reimagined Nuclear Rocket.” “Electric propulsion is mature. Nuclear thermal propulsion is not, but thanks to [previous efforts], we have a good idea how to do it. The new part is merging them together, and that of course throws up its own challenges.”

Thanks to Cass and illustrator John MacNeill, Polzin and Schleicher’s idea has moved from a napkin to the pages of this month’s issue. Says Cass, “The whole point of the article is to say, ‘Here’s our napkin. Noodle on this with us and tell us what you think.’” We invite you to do so in the comments beneath the web version of this article. Or do it the old-fashioned way and mail the authors your own napkin.