Elon Musk revealed a slew of new details on Friday about his bold plan to transform humanity into a multi-planetary species. The BFR — an abbreviation that includes the words “big” and “rocket” — is a reusable ship designed to transport humans to Mars as soon as 2024.

At the International Astronautical Congress in Adelaide, Australia, Musk explained how the company’s success in landing 16 Falcon 9 first stage rockets has enabled the company to bring costs down and plan for more ambitious missions. If you can land a rocket on Mars and set up a refuelling station, you can fill up and return to Earth — or even set off further into space.

“It’s really crazy we’re building these sophisticated rockets and then crash them every time they fly,” Musk said. “This is mad! I can’t emphasise how profound this is and how important reusability is.”

Musk hopes that this reusability feature will enable humans to set up a lunar base on the Moon, a city on Mars, and even terraform the planet much further into the future. As he explained the BFR at the center of this plan, the room was enraptured.

“You can do it, Elon!” an audience member shouted.

“Heh, thanks!” Musk said.

The machine designed to transport humans to Mars, the BFR, is big. Like, really big. The original Falcon 1 rocket, which first launched nine years ago, was 5 feet 7 inches by 69 feet 10 inches and lifted a payload of half a ton, about the size of a decent size satellite. The Falcon 9, SpaceX’s current generation rocket, measures 12 feet by 230 feet and carries a payload of 15 tons, around 30 times that of the Falcon 1. The Falcon 9 also has reuse of the primary booster, with the fairing soon to come.

The BFR eclipses both of these, measuring at a staggering 30 feet by 348 feet, consisting of a first stage booster and second stage ship:

The BFR in its entirety.
The BFR in its entirety.

It’s a fully reusable configuration, compared to the Falcon 9 which is only around 30 percent reusable. It will have a dry mass of 85 tons, plus a propellant mass of 1,100 tons. The whole design is capable of carrying a payload of up to 150 tons, but the typical return payload will come to around 50 tons.

The booster is lifted by 31 Raptor engines to produce produce liftoff thrust of 5400 tons, which will lift the total vehicle mass of 4400 tons. These engines have been put through their paces. The team has run over 1,200 seconds of firing across 42 main engine tests, with the longest test lasting 100 seconds. In a mission to Mars, the engines will run for around 40 seconds during a typical landing. While the test engines operate at 200 atmospheres of pressure, the final version will work at 250, with an eventual goal of reaching 300.

The ship itself is 157 feet long:

The BFR ship.
The BFR ship.

That payload bay is huge, measuring around eight stories tall. It’s so big, in fact, that it can fit a whole stack of Falcon 1 rockets. The cargo area is where the passengers are kept, at a pressurized volume of 825 cubic meters, greater than the cabin of an Airbus A380 jet airliner.

For traveling to Mars, Musk envisions a configuration of 40 cabins in the cargo area, large common areas, central storage, galley, and a solar storm shelter. While the cabins could fit a maximum of six people, two or three is probably a more comfortable number.

“I think this is possibly a good situation at least for BFR version one,” Musk said.

Bear in mind, the journey will take somewhere between three and six months, so comfort is key. Musk hopes that the journey will be worth it, and detailed the Mars city that may await passengers after all that time:

A Mars city.
A Mars city.

Elsewhere in the ship, there’s a new delta wing. This is a change from the configuration shown last year, and it’s there to expand the mission envelope and make it more useful. Depending on whether the ship is entering a planet or moon with no payload, or a smaller-than-usual load, the team may have to adjust course. So there’s now a wing at the back, which also includes split flap for pitch and roll control. This allows the team to control the pitch angle despite having a wide range of payloads in nose, as well as a wide range of atmosphere densities.

The fuel tanks hold 240 tons of methane, while the oxygen tank holds 860 tons of liquid oxygen. A common dome separates the two. A header tank holds landing propellant during transit, as trying to land with a giant empty fuel tank sloshing around with be difficult. The methane and oxygen is chilled below liquid point, giving a 10 to 12 percent increase in density.

At the rear is the engine section:

The engines.
The engines.

These are designed with redundancy in mind. The ship can land with either of the two center engines, so if one fails the ship can switch to the other. The goal is to get the landing risk as close to zero as possible. This is only the initial design, though.

“This is version one, so I think over time there’s potential to increase that impulse by five to 10 seconds and also to increase the chamber pressure by 50 bar or so,” Musk said.

Of course, the key component of Musk’s plan is the refilling stage:

Rockets refilling on Mars.
Rockets refilling on Mars.

Musk envisions two ships mating at the rear section, using the same interface that connects the boosters at lift off. To transfer, the ship would use the control thrusters to accelerate.

All this means that while the BFR is capable of moving a similar size load to NASA’s Saturn V rocket, used to send humans to the moon, its reusability means the cost will plummet:

Launch costs.
Launch costs.

The first BFR missions may lift off as soon as 2022, when two rockets send the first unmanned cargo loads to Mars. By Musk’s own admission, it’s a tight deadline.

“That [2022] is not a typo … although it is aspirational,” he said.

The pressure is on to get the BFR up and running.


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