A test fire of SpaceX's newest engine reached the power level necessary for the company's next round of rocket designs, CEO Elon Musk said on Twitter.

"Raptor just achieved power level needed for Starship & Super Heavy," he tweeted on Feb. 7, four days after he shared a photograph of the first test of a flight-ready engine.

The Raptor engine is designed to power the spaceship currently known as Starship as part of the rocket assembly currently known as Super Heavy (previously dubbed the BFR). The first Raptor test fire took place in September 2016, when the company was targeting an uncrewed Mars launch in 2018.

Three Raptor engines like this one are built in to the Starship Hopper, which has been under construction in Texas and which SpaceX will use to begin testing the rocket technology in real life.

Eventually, SpaceX plans to assemble 31 Raptor engines into the Super Heavy rockets, with another seven Raptors on the Starship itself. The engines are fueled by a mix of liquid methane and liquid oxygen and are about twice as powerful as those aboard the Merlin engines currently flying in the company's Falcon 9 and Falcon Heavy engines.

Email Meghan Bartels at mbartels@space.com or follow her @meghanbartels. Follow us @Spacedotcom and Facebook.