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Relativity Space has not launched a single rocket, and Impulse Space has never tested one of its thrusters in space. Nevertheless, on Tuesday, the two California-based companies declared their intention to launch an ambitious mission that will land on the surface of Mars in fewer than three years.
This would be the first commercial mission to Mars, and normally such a claim could be safely dismissed as absurd. But this announcement—audacious though it may be—is probably worth taking seriously because of the companies and players involved.
Founded in 2015, Relativity has raised more than $1 billion and should launch its small Terran 1 rocket later this year. The company, which seeks to 3D print the majority of its vehicles, is already deep into the development of the fully reusable Terran R rocket. This booster is intended to be somewhat more powerful than SpaceX's Falcon 9 and would carry the commercial mission to Mars. Relativity plans to have the Terran R rocket ready to launch in 2024, with the Mars payload flying on its debut mission in the late 2024 window to Mars.
Impulse Space is newer, at less than a year old, but not without experienced engineers. The company was founded by Tom Mueller, the first employee hired at SpaceX and leader of its propulsion department for more than a decade. His engines power the Falcon 9, Falcon Heavy, and Dragon vehicles. Mueller considers launch a "solved problem" and is developing a line of non-toxic, low-cost thrusters to serve the in-space propulsion market.
"This is a whole new era of spaceflight, and we want to be positioned to provide reliable, low-cost, in-space propulsion," Mueller said in an interview with Ars. "We want to do it all—orbital, lunar, interplanetary."
The mission’s conception
The Mars mission was conceived last year when Relativity's vice president of engineering and manufacturing, Zach Dunn, reached out to Mueller. The two were old colleagues. Mueller had hired Dunn at SpaceX back in 2006, where the intern was soon put in charge of engine testing and then the overall propulsion system for the company's early Falcon rockets. Relativity wanted to make a splash with its first Terran R mission, and Mueller embraced the challenge.
The companies devised a mission in which the Terran-R vehicle would boost a Mars Cruise Vehicle developed by Impulse Space into a trajectory toward Mars. Upon reaching the red planet, the lander would separate from the cruise stage. This lander would leverage aeroshell technology developed by NASA for its Mars Phoenix lander and other vehicles and use the same entry velocity and angle as the NASA missions. The Impulse Space lander would then land propulsively under the power of four thrusters, similar in action to a quadcopter. With this mission design, Impulse plans to deliver tens of kilograms of scientific payload to the Martian surface.
Mars animation.
Only NASA and China have ever sent missions to Mars that have landed successfully on Mars and survived to conduct science.
"If it wasn't challenging, I wouldn't be doing it," Mueller said. "I always feel like if people aren't a little bit skeptical about what we're doing, we're not doing it right."
Relativity's chief executive and co-founder, Tim Ellis, echoed those words. He said he wanted to make a statement by putting a Mars-bound payload on the first launch of the Terran-R rocket. Ellis founded Relativity Space partly because he was inspired by what SpaceX and Elon Musk were trying to do to make humanity a multiplanetary species. This commercial mission, he said, would move the needle forward.
"We're big fans of SpaceX and Starship," Ellis said. "But there's got to be more than one company working at this. I want to be the second company that steps forward and says this is important. Hopefully there are many more."
Commercial Mars?
Relativity has signed an exclusivity deal with Impulse to work on this, and potentially other Mars missions, through 2029. While the first mission will be self-funded by the two companies, both Mueller and Ellis believe that NASA and private companies will be interested in a relatively low-cost, commercial capability to carry scientific payloads to the surface of Mars.
Previously, through initiatives such as the Commercial Lunar Payload Services program to have private companies deliver scientific payloads to the Moon, NASA has indicated a willingness to work with the private sector to conduct scientific missions on other worlds.
"It’s always great to see new players bringing new ways of doing business to the space sector," said Bobby Braun, head of space exploration at the Johns Hopkins University Applied Physics Laboratory and an industry leader in the study of Mars. "Initiatives like this grow the community and could pave the way to new approaches that accelerate the pace of space science and exploration."
The Terran R rocket is a two-stage, methane-fueled rocket. With both the first and second stages returning, it can lift 20 metric tons to low Earth orbit. In a fully expendable mode, as it would be for Mars missions, Terran R can send 35 metric tons into low Earth orbit. Ellis acknowledged that a 2024 target for launching such a large rocket, with 3 million pounds of thrust at launch, is aggressive. But it's doable, he added, with development work on Aeon-R main engines progressing well.
Orion-inspired
Impulse Space has been testing space thrusters that provide a less toxic alternative to the hypergolic fuels such as hydrazine typically used by spacecraft. Mueller said his company's propulsion system is based on a propellant mix of ethane and nitrous oxide, which is storable and cost-effective. The company plans to perform an in-space demonstration in 2023, likely providing "last mile" services for a small satellite.
In less than a year since its founding, Impulse has grown to 40 employees. Mueller's favorite constellation is Orion, so he named the company's first spacecraft after that. Impulse's larger in-space thrusters are named Rigel, after the brightest star in the constellation; and the smaller thrusters are named Saiph, one of the fainter stars.
"They're super safe," Mueller said of Rigel and Saiph. "They're non-toxic, non-corrosive, and self-pressurizing. And so there's just very little safety cost around them that you have around hypergols or peroxide. It's not the most ideal high-performance propellant, but we're optimizing for cost."
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