SpaceX’s Mars plans call for massive 42-engine reusable rocket


GUADALAJARA, Mexico — SpaceX Chief Executive Elon Musk announced plans by his company to develop a large new launch vehicle and reusable spacecraft that could be ready to take large numbers of people to Mars as soon as the mid-2020s.

Musk, in a highly-anticipated speech at the International Astronautical Congress here that attracted an unusually raucous audience for a professional conference, said that SpaceX had made initial progress on those plans despite only a small fraction of the company working on the effort.

The “Interplanetary Transport System” announced by Musk involves the development of a large reusable booster that will launch a spaceship into low Earth orbit. That spaceship will be fueled by later booster launchers of tanker vehicles, then fly to Mars.

“It’s quite big,” he said of the booster and spacecraft. The size, he said, is driven by the desire to carry at least 100 people, plus cargo, to Mars. “It really needs to be roughly this order of magnitude.”

The booster uses 42 Raptor engines in its first stage, generating a liftoff thrust of 28.6 million pounds-force, or more than three and a half times that of the Saturn. The Raptor engine, which uses methane and liquid oxygen propellant, was recently fired for the first time by SpaceX.

The booster is designed to place 550 tons into low Earth orbit if it’s expended, or 300 tons if it returns to the launch site. Musk described the booster as a “scaled-up version” of the Falcon 9 first stage, but using new composite structures, including propellant tanks. SpaceX has recently built and tested one such propellant tank of the size that would be used by the vehicle, he said.

SpaceX unveils first development tank for Mars spaceship. Credit: SpaceX
SpaceX unveils first development tank for Mars spaceship. Credit: SpaceX

The spaceship placed in orbit by the booster will have three “sea-level” version of the Raptor, like those used on the booster, as well as six vacuum versions of the Raptor optimized to work in space. The spacecraft, which Musk said will have a large internal volume to accommodate 100 or more people, could carry up to 450 tons to Mars, depending on the amount of in-orbit refueling to fill its propellant tanks for the trip.

The spaceship would use a heat shield and the Raptor engines to land on Mars. Musk noted that the spaceship alone is capable of lifting off from the surface of Mars or other bodies with low gravity, like the moon or the moons of Jupiter and Saturn, without the need of a booster.

The system Musk described is intended to fulfill a long-term vision of making humanity interplanetary. While his focus is on settling Mars, he noted the spacecraft could travel throughout the solar system, “planet-hopping” and “moon-hopping” from destination to destination, refueling at each stop. The spacecraft could also be used on Earth by itself as a suborbital point-to-point vehicle.

SpaceX large booster launch
Illustration of SpaceX’s Mars booster and spacecraft taking off. Credit: SpaceX

Costs and schedules

The use of reusability of both the rocket and spacecraft, choice of methane propellant, use of in-orbit refueling and production of propellants on the surface of Mars for return trips are all designed, he said, to reduce the costs of interplanetary travel.

Using what Musk described as traditional, Apollo-like methods, “an optimistic cost number would be about $10 billion per person,” he said of sending people to Mars. “You can’t create a self-sustaining civilization when the price is $10 billion a person.”

Musk said his architecture is design to reduce the cost by several orders of magnitude, or less than $200,000 per person. If the system can meet those goals, “I think the probability of establishing a self-sustaining civilization is very high.”

Musk stated it’s possible that the first spaceship would be ready for tests in four years, with the booster ready a few years after that, but he shied away from exact schedules in his presentation. “We’re kind of being intentionally fuzzy about the timeline,” he said. “We’re going to try and make as much progress as we can with a very constrained budget.”

Elon Musk answers questions about his Mars mission plans at a press conference at the IAC Sept. 27. Credit: SpaceNews/Jeff Foust

In a later press conference, he said that he was sticking to statements he made earlier this year that suggested the first crewed mission could launch in late 2024, landing on Mars in 2025. “That’s optimistic,” he acknowledged, saying any number of issues could delay it. “That said, I don’t think it will be significantly beyond that.”

SpaceX is currently spending only a small part of its overall resources on the Mars effort. “Certainly well under five percent of the company,” Musk said. “We’re spending a few tens of millions of dollars right now on it. It’s relatively small.”

Musk said that investment would ramp up as engineers move from the Falcon 9 and Crew Dragon programs. “We’ll gradually apply more and more resources to the interplanetary system,” he said. “In the next year and a half or two years, we should have most of SpaceX engineering working on the interplanetary system.”

SpaceX artist's concept of interplanetary spaceship arriving at Mars. Credit: SpaceX
SpaceX artist’s concept of interplanetary spaceship arriving at Mars. Credit: SpaceX

At that point, he said, he expects the company to spend about $300 million a year on the system. “In order to make this whole thing work, and work reliably, before it starts generating some kind of positive cash flow, it’s probably an investment on the order of $10 billion,” he said.

Musk said that the funding could come from several sources, including SpaceX’s own cash flow, proposals floated by Musk since last year to develop a satellite constellation, private investments, and his own assets. He also suggested government funding could play a role. “Ultimately, this is going to be a huge public private partnership,” he said.

At the press conference, though, he said that while he has already briefed NASA senior management about his plans, he did not necessarily expect agency funding to help develop it. “In the future, there may be a NASA contract, there may not be. I don’t know,” he said. “If there is, that’s a good thing. If there’s not, it’s obviously not a good thing.”

Musk, though, dismissed questions about the share of funding for the system coming from public or private sources as “pedestrian” compared to the bigger issues that are driving the development of the transport system. “There are larger issues at stake,” he said. “Are we going to be a multiplanetary species or not?”

SpaceX artist's concept of tanker refueling Mars vehicle in Earth orbit. Credit: SpaceX
SpaceX artist’s concept of tanker refueling Mars vehicle in Earth orbit. Credit: SpaceX