SpaceX Is Using These Simulations to Design the Rocket That'll Take Us to Mars

Making a brand new rocket isn't easy, but it's cheaper and faster with a simulator.

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Mar 20 2015, 5:30pm

​​To eventually get to Mars, SpaceX is designing a totally new type of rocket engine—one that runs on methane instead of kerosene, like SpaceX's existing rockets. It's no easy task, of course, so researchers at the company have designed one of the world's most advanced combustion simulations to digitally test new designs of what will be the most powerful rocket ever created.

​Methane rockets have been tested by NASA, but they haven't been used to actually go to space, let alone Mars. Designing a new rocket isn't easy, and it's really, really expensive. But it's cheaper and faster if you run through bad designs quickly using a computer simulation.

Adam Lichtl, research director at SpaceX, said it's very hard to actually look inside a combustion engine and see exactly what's happening as it's operating, so simulation is the best way to go about actually tinkering with one—it allows them to change different variables without blowing months or years of time and large sums of money by actually building the thing, which is being called "Raptor."

Lichtl and Stephen Jones  ​spent an hour earlier this week at the NVidia's GPU Technology Conference explaining how graphic simulations of the new engine are going to one day help humans get to Mars.

A temperature map of the rocket as it heats up after ignition. Gif: Jason Koebler via SpaceX

The talk was quite technical, and was pitched at engineers, computer scientists, and mathematicians who might be interested in working for SpaceX (the last slide was a call for applications), but there were definitely some great visuals and some real insight into how a rocket engine gets made. Here are links to the  ​four ​simulations ​they ​showed.

The simulation runs on a single graphics processor, which is like the ones that let you play computer games at high resolutions, but is presumably many times more powerful. SpaceX didn't give any specifications for the chip, but said the simulator itself was built by SpaceX from the ground up to be able to examine every aspect of combustion, including thermodynamics, chemistry, diffusion of energy, and advection (the transfer of heat through the atmosphere).

"If you're a little wrong in a traditional simulation, you're typically OK. You're close enough to the answer where you can make an engineering decision," Lichtl said. "In a combustion simulation, if you get it wrong, you have to deal with the vicious interplay and nonlinearity of all these different physical processes."

The supersonic flow of a rocket after ignition. Gif: Jason Koebler via SpaceX

Raptor is being designed to lift the astounding amount of weight that'll be needed to eventually set up a Martian colony. NASA estimates that we'd need to take roughly 300 tons of stuff to Mars in order to establish even a rudimentary settlement, and SpaceX is planning on actually coming back to Earth once it gets to Mars, meaning the fuel needs to be made on the planet.

"We need an incredible amount of infrastructure, and you need a way to way to come back," Lichtl said. "We need a propellant we can synthesize on the Martian surface. We can synthesize methane, and we can design an engine that works efficiently with such a compound."

Few of the simulations actually look like rockets taking off through the atmosphere or even igniting, but Lichtl said they're important all the same.

"In visual effects, you fake the physics any way you can and you make it look pretty, and everyone gets excited and they love it," he said. "In research, you try to get the physics right, but it ends up looking kind of blah. Your visuals aren't as stunning and people say, 'Wait, I saw a movie the other day with a simulation, why can't you do that?'"

​Dragon reentering the atmosphere. Gif by Jason Koebler via SpaceX

That said, the team has worked with experts to actually make some of the simulations, like the one of the Dragon capsule reentering the atmosphere, look like something that they can use to wow the public.


"We're able to connect better with people and engineers by having visualizations like this," he said. "And at the same time, we're retaining full fidelity of the data."