September 27, 2016

— Elon Musk has a plan for how to send humans to colonize Mars.

The SpaceX CEO revealed his design for a large, 100-seat spacecraft, and an even larger reusable rocket on which to launch the ship, on Tuesday (Sept. 27) at the International Astronautical Congress (IAC) in Guadalajara, Mexico.

"What I really want to try to achieve here is make Mars seem possible, make it seem as though it's something that we can do in our lifetimes and that you can go," said Musk.

During an hour-long presentation, Musk outlined SpaceX's Interplanetary Transport System (ITS), which he said could deliver upwards of a million people to Mars to establish a self-sustaining colony over the course of 40 to 100 years.

"History is going to bifurcate along two directions. One path is that we stay on Earth forever and then there will be some eventual extinction event," said Musk, explaining his reasons for going to Mars. "The alternative is to become a spacefaring civilization and a multiplanet species."

"I hope you would agree that is the right way to go, yes?"

Click to enlarge video and view in new pop-up window. (SpaceX)

The system, which could be ready to launch its first crew as soon as 2025, could also be used to expand humanity's reach to other planets, too, Musk explained.

"[It] can actually go anywhere in the solar system by planet hopping or moon hopping. So by establishing a propellant depot in the asteroid belt or on a moon of Jupiter, you can make flights from Mars to Jupiter no problem. In fact, even without a propellant depot at Mars, you can do a flyby of Jupiter," he said.

"The system really gives the freedom to go anywhere that you want in the greater solar system," Musk said.

The system

SpaceX's Interplanetary Transport System is comprised of four key components.

"I don't like calling things systems, because everything is a system," said Musk. "[But] it's actually more than a vehicle. There is the rocket booster, the spaceship, the tanker and the propellant plant."

The rocket, which is essentially a much larger, much more powerful version of SpaceX's Falcon 9 booster, will stand 254 feet tall (77.5 meters), 39 feet wide (12 m) and will be powered by 42 Raptor rocket engines. Like the Falcon 9's first stage, it will be able to fly back and land vertically, so that it can be reused, but will also have thrusters to allow for a more precise touchdown.

Animation still showing SpaceX's ITS booster returning to Launch Pad 39A at Kennedy Space Center, Florida to be reused. (SpaceX)

"With the addition of some maneuvering thrusters, we can actually put the booster right back on the launch stand," said Musk, describing how the rocket could return directly to the pad, rather than using a designated landing area or ocean-based floating platform.

The spaceship, which Musk envisions seating at least 100 people, but perhaps as many as 200 per flight, would be a super-scaled up and stretched model of SpaceX's Dragon spacecraft, which the company is now building to fly four astronauts (at a time) to and from the International Space Station. Standing 162 feet tall (49.5 m) and 56 feet wide (17 m), the ship will be equipped with nine Raptor engines and two large solar array sails.

"I think we will name the first ship that goes to Mars the 'Heart of Gold,'" said Musk, referencing a spacecraft from author Douglas Adams' "Hitchhiker's Guide to the Galaxy" science fiction book series. "I like the fact that it was driven by an 'infinite improbability [drive],' because I think our ship is also extremely improbable."

The tanker, a hollowed-out model of the ship, will be used to refuel the ship in Earth orbit before it departs for Mars. Musk said he envisions needing three to five flights of the reusable tankers to prepare the spacecraft for its roughly 90-day voyage to Mars.

Topped by either the spaceship or tanker, SpaceX's ITS rocket will stand 400 feet (122 m) tall, 37 feet (11 m) taller than NASA's Saturn V. At launch, the ITS will generate 3.6 times the thrust of the Apollo-era rocket.

Comparison of SpaceX's ITS and NASA's Saturn V rocket (SpaceX)

The last component of the system, the propellant plant, will generate the fuel and oxidizer that will be needed to refuel the ship for the trip back to Earth using materials found on the Red Planet.

"Mars happens to work out well for that because it has a carbon dioxide atmosphere, it has got water ice in the soil and with [those] you can produce methane and oxygen," Musk explained.

Making the trip to Mars fun and affordable

During Apollo, NASA spent between $100 billion and $200 billion (in current year dollars) to send 12 Americans to the surface of the moon.

"That is an incredible thing, probably one of the greatest achievements of humanity, but that is a steep price to pay for tickets," noted Musk. "You can't create a self-sustaining civilization if the ticket is $10 billion per person."

Musk said his system is designed to get the cost of moving to Mars to be roughly equivalent to the average price of a house in the United States.

"Really the key is making this affordable to almost anyone who wants to go," said Musk. "Assuming optimization over time ... the architecture allows for a cost per ticket of less than $200,000, maybe as little as $100,000, depending on how much mass a person takes."

SpaceX's Interplanetary Transport System architecture. (SpaceX)

At that price, said Musk, the trip to Mars should appeal to anyone with an "exploratory spirit."

"If you are an explorer, if you want to be on the frontier and push the envelope and be where things are super exciting, even if it is dangerous, that is really who we are appealing to here."

That said, Musk also emphasized that the ITS spaceship was designed to make the journey enjoyable.

"In order to make it appealing ... it has to be really fun and exciting. It can't feel cramped or boring," Musk said. "The crew compartment is such that you can do zero-g games, you can float around, there will be movies, lecture halls, cabins, a restaurant. It will be, like, really fun to go. You're going to have a great time."

More than just a dream

"This is a not an artist impression," stated Musk about an animation of the ITS on a journey to Mars. "The simulation was actually made from the SpaceX engineering models. So it is not, 'Well, this is what it might look like,' this is what we're planning to make it look like."

To that end, SpaceX has produced and begun testing two of the key components of the interplanetary spaceship and rocket booster.

First test fire of SpaceX's Raptor interplanetary engine. (SpaceX)

"We decided to start off development with what we think are probably the two most difficult elements of the design," said Musk. "One is the Raptor engine."

The Raptor engine will have the highest chamber pressure of any engine ever built, and possibly the highest thrust to weight ratio as well.

On Monday (Sept. 26), SpaceX announced it conducted its first firing of a Raptor engine.

"I really wanted to show that we've made some hardware progress in this direction," said Musk.

Musk also revealed the company's first carbon fiber tank of the type that will be used for methane and liquid oxygen.

SpaceX's first ITS development carbon fiber tank. (SpaceX)

"This is really the hardest part of the spaceship. The other pieces we have got a pretty good handle on, but this is the trickiest so we wanted to tackle it first," Musk said. "Initial tests with cryogenic propellant actually look quite positive, we have not seen any leaks or major issues."

Investing in a multiplanetary species

As of now, the resources being put into the development of the interplanetary transport are low, well under five percent of the company, said Musk.

"As we finish development of the final version of Falcon 9, which should be sometime next year, and Dragon 2, and get the reusability of the boost stage and Dragon 2 sorted out, then we will gradually apply more and more resources to the interplanetary system," he said.

Musk said he expects most of SpaceX's engineers will be working on the ITS within the next two years, when about $300 million will go toward the effort each year.

"In order to make this whole thing work, and work reliably, before it starts generating some kind of positive cash flow, it is probably an investment on the order of $10 billion," he said.

Musk acknowledged that it will be a challenge to fund the whole endeavor, suggesting eventually it would likely need to become a public-private partnership. Until then though, SpaceX is relying on the revenue generated by its satellite launches and contracts with NASA to fly crew and cargo to the space station.

Artist rendition of SpaceX's ITS spaceship at Jupiter. (SpaceX)

"Right now, we're just trying to make as much progress as we can with the resources that we have available and just keep moving the ball forward," said Musk. "I think as we show this is possible, that this dream is real — not just a dream, but something that can be made real — I think the support will snowball over time."

"The main reason I'm personally accumulating assets is to fund this," Musk commented. "I really don't have any other motivation for personally accumulating assets except to be able to make the biggest contribution I can to making life multiplanetary."