SpaceX has certainly roared onto the scene in recent years as the hottest rocket company on the planet, and that has brought out some barbs from competitors. One of them is Boeing, which just dismissed Elon Musk’s Falcon Heavy rocket as much too small to be the rocket that will someday carry astronauts to Mars.

Boeing builds the SLS rocket, which is also a candidate for an eventual Martian mission. In a statement posted to their website, Boeing said that while the Falcon Heavy launch “turned heads” back in February, the SpaceX rocket is too small to meet NASA’s needs for deep space, and the SLS will be the most powerful rocket ever built.

Boeing quoted NASA’s Bill Gerstenmaier, who highlighted the differences between SLS and the Falcon Heavy. Gerstenmaier said the SLS had some capabilities that the Falcon Heavy could not match, although he also had some difficulty explaining why NASA would need a rocket as capable as the SLS for such a mission, according to an Ars Technica report.

“In February, Elon Musk’s SpaceX test launched the Falcon Heavy — a rocket that SpaceX touts as the ‘most powerful operational rocket in the world,'” the Boeing statement reads. “However, the Falcon Heavyfailed to impressthe spaceflight department at NASA. Bill Gerstenmaier, the head of spaceflight at NASA, said the Falcon Heavy is ‘too small’ for NASA’s needs. Ouch.”