In this conceptual image, eight SuperDraco thrusters fire as a Dragon spacecraft enters the Martian atmosphere at supersonic speeds. (credit: SpaceX)

This week SpaceX announced plans to land a Dragon spacecraft on Mars by 2018. This would be a monumental achievement for NASA or any other national space agency, let alone a single company, considering the 6,000kg Dragon is nearly an order of magnitude more massive than anything previously landed on the red planet.

With the long-term goal of Mars colonization squarely in its crosshair, SpaceX has been testing key technologies needed to land on Mars for years. One of them is supersonic retro-propulsion, which Ars revealed has been tested on upgraded Falcon 9 rockets since September 2013. Supersonic retro-propulsion proved a resounding success.

But the Falcon 9 and its Merlin engines won’t be going to Mars. SpaceX will use a different type of engine, the SuperDraco thruster, to propulsively land on the red planet. Here’s how the landing will work: as the Dragon (dubbed Red Dragon) begins its descent to Mars at supersonic speeds, the spacecraft will fire eight of these thrusters into this onrushing atmosphere. To achieve this maneuver these engines must be capable of both high thrust, and a controllable thrust.