​SpaceX, the aerospace company run by notable entrepreneur Elon Musk, failed to land a Falcon 9 rocket on a robotic barge last Thursday.

The takeoff itself was successful as the rocket was able to launch its payload into orbit, which was a telecommunications satellite for Luxembourg-based company SES.

However, Musk and his engineers “long had doubts about the attempted rocket landing,” according to The Guardian.

SES’s satellite weighed 11,000 pounds coming in at one of the heaviest ever. This ended up reducing the amount of fuel the rocket needed for its thrusters, hampering its ability to slow its return to Earth causing a hard landing.  

SpaceX has had one effective rocket landing on the ground, but having the Falcon 9’s touch down on ocean platforms failed in the past.

Ocean landings, though, may be the best missions for Musk’s reusable rockets because this technique requires less fuel for missions that could involve high-speed travel, reported the Verge.

SpaceX’s next mission will entail a resupply delivery to the International Space Station, but its unknown which type of landing Musk’s company will use.