Falcon Heavy: How It Mastered Its Incredible Drone Ship Landing

SpaceX has successfully completed its most ambitious rocket landing yet. The company’s Falcon Heavy launch concluded Thursday evening with the two outer cores successfully landing on the land and the third central core landing moments later on the Of Course I Still Love You ship.

The landing marked the successful end to the Heavy’s second-ever flight, and the first commercial launch for the world’s most powerful operational rocket. It took off from Launch Complex 39A at 6:36 p.m. Eastern time. Three minutes after launch the center core powered down and the main engine detached. Eight minutes after, the side boosters simultaneously landed on two land-based pads. At the 10-minute mark the center core landed on the ship, making a change from the Heavy’s February 2018 flight where it missed its target by 300 feet and hit the ocean at 300 mph.

Landing the cores is a key aspect of SpaceX’s plan to cut costs on spaceflight. The booster counts for around $46.5 million of the estimated $62 million cost associated with launching a Falcon 9, meaning a breakthrough in this area can change the economics of spaceflight. A Falcon Heavy launch costs between $90 million and $150 million. The company has successfully landed 38 cores in its history: while its first and only landing in 2013 was a failure, it successfully landed 15 cores in 2017.

Falcon Heavy's central core on the landing pad.
Falcon Heavy's central core on the landing pad.

SpaceX adds a number of extras to help save the cores. They use more fuel than would be needed for an expendable rocket, and they have design features like grid fins for steering back to Earth, cold-gas thrusters to flip the rocket, and landing legs for support. Three of the Falcon 9’s nine engines are used to slow the booster down as it comes in to land. A Falcon Heavy is essentially three Falcon 9s strapped together, bringing the engine total to 27 and boosting the total power to over five million pounds of liftoff thrust.

The drone ships that catch the rockets at sea measure about 300 feet by 170 feet. Jalopnik explains that they use GPS and four diesel-powered azimuth thruster engines to stay in position, enabling them to either move autonomously to their correct position or remotely controlled by a crew. They use thrusters originally from deep sea oil rigs to keep the stage in a position to an accuracy of around three meters. In the case of a successful landing, the rocket is welded to the ship and transported back.

The issue with February’s launch was with the core re-entry. SpaceX explained after the event that the team was only able to light one of the three necessary engines for reentry. This meant the rocket couldn’t reach its intended position. The crash also sent shrapnel across the drone ship deck and destroyed two of its thrusters.

The firm’s successful landing bodes well for future missions and could help fund more ambitious plans. The Starship, announced in September 2017 under the name “BFR,” is expected to send 100 tons to low Earth orbit and generate 5,400 tons of liftoff thrust. The ship is huge, with its original version measuring 348 feet tall and 9.7 million pounds of mass. The ship is designed to be fully reusable, with its Raptor engines fueled using liquid oxygen and methane, unlike the liquid oxygen and rocket propellant used for the Merlin engines. This use of an alternative fuel could enable voyagers to harvest fuel on other planets and set up propellant depots, which could help power trips to Mars and beyond.

Media via SpaceX/Twitter