There are a lot of hurdles to jump before we send the first human crew to Mars. Fuel for such a long mission adds a lot of weight and expense, and the time it takes to get there leaves astronauts exposed to hazardous doses of radiation. The ultimate dream would be a propulsion system that uses minimal fuel and gets us there as fast as possible. The VASIMR engine could be that dream — but it has some high-profile doubters.
Human Mission to Mars with 10 MW NEP-VASIMR
Franklin Chang Diaz - VASIMR inventor
A Miasma of Incandescent Plasma
Until now, the vast majority of rockets we've sent into space have used chemical engines: ones that combine fuel with an oxidizer to create combustion, kind of like your car's engine does. Chemical engines are powerful, but they require a lot of fuel and add a lot of weight. The fuel tank on the Space Shuttle, for instance, weighed 1.7 million pounds (700,000 kilograms). Chemical rockets are currently our best bet for a trip to Mars, which is why most estimate that our first trip will take eight to nine months.
What if you could cut that down to 40 days? Franklin Chang-Díaz, a Ph.D. plasma physicist and astronaut who's tied for having the most space flights ever, is saying that's possible. Instead of using chemical combustion, his VASIMR engine uses a relatively small amount of argon gas that it superheats into plasma. The plasma blasts out the back of the rocket to produce thrust. Best of all, the plasma production and the booster both work on electricity, which could be powered by solar panels.
This solves more than just the weight issue. "A rocket engine is a canister holding high-pressure gas," Chang-Díaz told Forbes. "When you open a hole at one end, the gas squirts out and the rocket goes the other way. The hotter the stuff in the canister, the higher the speed it escapes and the faster the rocket goes. But if it's too hot, it melts the canister."
Not so with VASIMR. It uses superconducting magnets to keep the plasma in place, so it won't melt anything. "The magnetic field becomes the canister, and there is no limit to how hot you can make the plasma," Chang-Díaz says. The hotter the plasma, the faster the engine can go. Unfortunately, for the speeds his team is hoping for, solar panels won't cut it. You're going to need a nuclear power source.
Et Tu, Elon?
The nuclear power issue is where the critiques of this technology begin. The goal is to use this engine on a crewed mission, after all. Even Elon Musk, one of the biggest proponents for a mission to Mars, is skeptical. " ... it's a very interesting ion engine he's got there, but it requires a big nuclear reactor," he told Forbes. Likewise, while his technology looks great on paper, critics doubt it can achieve the kind of thrust it needs in the real world.
One group that isn't skeptical? NASA. In 2015, they awarded Chang-Díaz's company, Ad Astra, a $9 million contract through its NextSTEP program. To fulfill their side of the deal, Ad Astra needs to make their VASIMR engine fire at 100kW for 100 hours continuously. The plan is coming right along: they've successfully fulfilled every milestone required so far in the three-year contract, and hope to achieve the final goal by summer of 2018.