SpaceX Raptor: Bringing Elon Musk's Mars-Bound Engine From Dream to Reality

SpaceX is about to achieve a modest goal it set out to accomplish 16 years ago: send a rocket to Mars, kickstart a second Space Race, and inspire a new generation of scientists.

At the International Astronautical Congress in Adelaide, Austrailia, back in September 2017, CEO Elon Musk outlined an ambitious plan to build a giant rocket, known as the BFR. At its heart will be 31 Raptor engines, powered by liquid oxygen and methane. The resources are ideal for setting up a refueling station on Mars, enabling return flights and even trips into the further reaches of the galaxy.

This week, Musk confirmed that the team behind the engine is making good progress. Here’s how it came together:

Elon Musk Space Race

SpaceX was borne out of the will to explore Mars. It was founded by Musk in 2002, after the X.com co-founder (the company which later became PayPal) became despondent that NASA was not planning a mission to the red planet. The agency made up 4.4 percent of government funding in 1966, but since then that figure had slumped to under one percent.

Musk told Aeon that he “wanted to send a greenhouse to Mars, filled with plants that would become, in the course of their long journeying, the most distant travellers of all multicellular life.”

The hope was that by exciting the popular imagination, the venture would also help re-establish space exploration as national priority.

The company grew over the years, but by 2008 it looked like the Mars dream was dead. Its Falcon 1 had failed to launch three times over the preceding two years, and a cash-strapped Musk was struggling to keep it going. On December 23, 2008, SpaceX was struck by a miracle: NASA awarded the company a $1.6 billion contract, and the Mars plan suddenly seemed real again.

SpaceX Mars Raptor Takes Form

Freshly funded, SpaceX got to work. At the American Institute of Aeronautics and Astronautics on June 18 2009, the company dropped its first hints of how it would get to Mars.

“We also have begun initial design of the Raptor LOX hydrogen upper stage, which dramatically increases payload performance,” Max Vozoff, senior mission manager for the company, said during the “Innovations in Orbit” event.

At the following year’s conference, on July 30, the company’s McGregor rocket development facility director Tom Markusic outlined a number of rocket engines. The Raptor, as noted by NASASpaceFlight, used a new propellant and new engine cycle — a stark break from the company’s original philosophy of keeping costs down and using simple propellants. The original plan was a staged combustion, liquid hydrogen and oxygen engine capable of extreme force. It could deliver vacuum thrust of 150,000 pounds and 470 seconds of specific impulse, ideal for an upper stage as used in a giant rocket.

SpaceX News Goes Quiet

Over the years, SpaceX dropped more hints about the applications of its engine. A March 2012 story notes that “details [of Raptor] are tightly held.” However, the following month, company president Gwynne Shotwell described engines with “more than 1.5 million pounds” of thrust.

In October of that year, Musk gave his biggest hints so far about Raptor. He described a new rocket called MCT, with “a very big core size” and “several times” more powerful than the Merlin. He also promised more details “between one and three years” from then.

SpaceX Raptor Comes Out of Hiding

At the Royal Aeronautical Society in London in November 2012, Musk outlined his plan to take humans to Mars in just 15 years. The Raptor was key to this plan, as it provides a means of actually returning from Mars after the mission. The plan was to burn liquid oxygen and methane, as the latter is in abundance in the Martian atmosphere. Musk finally had a way of bringing his rocket home.

From June 2011 to November 2015, SpaceX employee Jeff Thornburg’s LinkedIn page listed him as principal propulsion engineer for the Raptor engine’s development. In this role, he “lead all Raptor engine development activities for the world’s first methane full-flow staged combustion cycle rocket engine.” Thornburg left the company in November 2015 to found Interstellar Technologies — not to be confused with the Japanese firm of the same name.

SpaceX Raptor Progress in Mississippi

On October 23, 2013, SpaceX signed an agreement with the state of Mississippi to test the Raptor rocket in Hancock County, Mississippi. The plan to use NASA’s John C. Stennis Space Center was met with a warm reception from Thornburg:

“We are looking to test the whole engine at Stennis, but the first phase starts with the components,” SpaceX spokeswoman Emily Shanklin said in an October 25 email to SpaceNews. “The E-2 stand at Stennis is big enough for components, but we would need a bigger stand for the whole Raptor.”

The problem was that the E-2 stand was rated for 100,000 pounds of thrust, but the Raptor would generate more than 661,000 pounds.

SpaceX Raptor Engine Specs Start to Get Some Tweaks

While the Raptor project had changed over the years, Shanklin still described it at the time as “a highly reusable methane staged-combustion engine that will power the next generation of SpaceX launch vehicles designed for the exploration and colonization of Mars,” noting that the engine “is the first in what we expect to be a family of engines.”

The component tests were successfully completed in 2014 and 2015. In September 2016, reports suggested the company had shipped a Raptor to the McGregor test site. The project was taking a firmer shape.

The Interplanetary Transport System

At the International Astronautical Congress in Guadalajara, Mexico, in September 2016, Musk unveiled the Interplanetary Transport System launch vehicle. The vehicle would use 42 Raptor engines in its first stage booster to generate 28.6 million pounds of force at liftoff. The plan built on the ideas outlined four years prior, to use Martian resources to power the rocket.

“It would be pretty absurd to try to build a city on Mars if your space ships just kept staying on Mars and not going back to Earth, you’d have this massive graveyard of ships,” Musk said.

The ITS was replaced at the same conference the following year by something altogether more practical and cooler.

The BFR Rocket Takes Shape

At the following year’s IAC, Musk took to the stage and made a bold proclamation: an unmanned mission to Mars by 2022, followed by a manned mission in 2024. The plan would beat his Royal Aeronautical Society predictions by around five years.

Central to this plan was the BFR — an abbreviation that stands for “big” and “rocket” — powered by a staggering 31 Raptor engines, a successor vehicle to the ITS that could also replace the Falcon series of vehicles. It could also pave the way for an inter-Earth transport service, moving people to any part of the planet in under an hour.

The sea-level engines will produce a thrust of 1,700 kilonewtons with a specific impulse of 330 seconds at sea level, rising to 356 seconds in a vacuum, and an exit diameter of 1.3 meters. The vacuum engines will have a total thrust of 1,900 kilonewtons with a specific impulse of 375 seconds and an exit diameter of 2.4 meters. All this added up to a rocket capable of producing liftoff thrust of 5,400 tons to lift the total vehicle mass of 4,400 tons.

SpaceX Raptor Progress: The Future Arrives?

Musk wrote on his Twitter page Wednesday that the Raptor team is making “good progress”:

The Raptor could see action in a full rocket soon. Musk said at the South by Southwest conference in Austin, Texas in March that the BFR was coming together well, and the company could start testing parts of its launch system as soon as next year.

In short, Musk’s company could still achieve its main goal just 20 years after its formation, inspiring a new generation to travel the stars.