SpaceX Raptor test: Is this the rocket that will take humans to Mars?

Elon Musk tweeted photos of the test firing of the Raptor 'interplanetary transport engine,' as he prepares to deliver a speech at the International Astronautical Conference on making humanity a 'multiplanetary species.'

First Look

In the latest step toward making humanity a “multiplanetary species,” SpaceX founder and chief executive Elon Musk said Sunday that his company has successfully tested its groundbreaking Raptor engine.

SpaceX has an ambitious schedule, seeking to send a manned mission to Mars by 2025, five years earlier than NASA, and, eventually, to colonize the Red Planet. Mr. Musk is due to flesh out some of the details surrounding these aspirations Tuesday, when he is to deliver a speech to the International Astronautical Congress in Guadalajara, Mexico.

At the heart of Musk’s plans lies the Raptor engine. Its mission statement is to serve spaceships with several times more power than the Merlin I engines designed to propel the company’s Falcon craft into low Earth orbit. In so doing, it will provide the muscle to drive SpaceX’s heavy-duty Mars Colonial Transport ships toward the Red Planet.

The Raptor represents something of a departure from SpaceX's typical design ethos, as it relies on a a mix of liquid methane and liquid oxygen, as opposed to the simpler kerosene and oxygen mix used by the Merlin family of engines. But, unlike kerosene, liquid methane and oxygen can in principle be sourced in situ, using the water and carbon dioxide present on Mars.

As photos of the Raptor test have circulated, one aspect of the fiery images that has sparked some curiosity is the appearance of “Mach diamonds,” or “shock diamonds,” a series of diamond-shaped waves of energy visible to the naked eye.

These products of physics and thermodynamics are seen not only in the exhaust plumes of rockets blasting off from Earth and aircraft pounding through the sound barrier, but also erupting volcanoes and active artillery pieces.

Originally discovered by renowned Austrian scientist and philosopher Ernst Mach, they are formed when a gas exits a nozzle at supersonic speeds, at a different pressure than the surrounding atmosphere, as Fraser Cain explains for Universe Today.

But leaving such phenomena aside, another crucial aspect of Musk’s forthcoming speech and his teaser pictures is to move beyond the recent explosion of one of his company’s Falcon 9 rockets during a test firing at Cape Canaveral Air Force Station in Florida – and perhaps to divert media attention from the explosion, as well. 

It may not be so easy to relegate that incident to the history books, however, as critics of SpaceX cite it as a consequence of the company trying to do “too much, too fast,” wondering whether the punishing timetable for its exploration of Mars could suffer similar setbacks.

Certainly, the obstacles to be overcome before the colonization of Mars can make the leap from science fiction to reality are legion, but SpaceX – and other private firms working on similar agendas – hold one significant advantage over the likes of NASA: they are less subject to the whims of political influence.

"For NASA, the vision is determined by the government," Ram Jakhu, the director of the Institute of Air and Space Law at McGill University, in Montreal, told The Christian Science Monitor last week. "Why did the US go to the moon? Because there was a kind of political challenge from the Soviet Union. The United States' vision is political, economic, and strategic."