Next month the commercial spaceflight company founded to make spaceflight cheap and easy enough to eventually put humans on Mars will try a novel cost-cutting tactic: recycling.
Rather than using up the fuel in the first stage of its 22-story-tall Falcon 9 rocket and letting it fall to Earth as garbage, SpaceX will try to land the 14-story-tall first stage of the rocket on a barge at sea.
That means piloting a headless rocket stage that will be moving at 3,600 miles per hour when it is blown free of the Falcon 9 payload capsule to a neat, vertical landing on platform just three times the width of the rocket's landing legs, on top of an autonomously piloted barge trying to hold its position in the tossing waves of the Atlantic Ocean.
"The odds of success are not great – perhaps 50 percent at best," according to a SpaceX announcement of the plan three days before a Dec. 16 launch that was ultimately delayed and is now scheduled for Jan. 6.
"At 14 stories tall and traveling upwards of 1300 m/s (nearly 1 mi/s), stabilizing the Falcon 9 first stage for re-entry is like trying to balance a rubber broomstick on your hand in the middle of a wind storm," the announcement warns.
SpaceX was able to recover the parts of a Falcon 9 twice already, most recently in July, by relighting the engines on the falling first stage to slow its fall, control its trajectory, deploy its landing legs and come very close to a dead stop just above the surface of the ocean, before being released to fall sideways into a "soft" water landing, as can be dimly seen in footage from the chase plane below:
"It sort of sat there for several seconds then tipped over and exploded," Musk told a during a forum at MIT in October, according to the Washington Post.
You can see a more controlled rocket-powered descent in this footage of a July 17 test of the steering fins on the Falcon 9 Reusable lifting off and returning to the pad:
If the booster stage is able to land safely on the barge, Musk said, it should be in good enough shape to be refueled and reset for another launch with very little repair work. The ocean landings required extensive repairs, but were still recoverable.
Musk's goal is to build vehicles that can launch from one pad, put payloads into orbit and have at least the primary stage land back at the original pad using the same rockets to control its flight rather than using wings to land like an airplane, as the Space Shuttle did, or parachutes and an ocean landing, as in most U.S. space missions.
Russian spacecraft have used rockets for decades to land at bases on the ground, but were also slowed by a combination of parachutes and atmospheric drag rather than using only the rockets to control their descent.
Falcon 9 will rely only on rocket motors and small steering fins to control its landing.
"You really have to get good at propulsive landing if you want to go somewhere other than Earth," he said at MIT, according to the Post.
Being able to reuse rockets would help cut the cost of a trip to orbit from a traditional $2,000 per pound to less than $10 per pound; Falcon9 currently flies for about $1,000 per pound, according to Musk.
"A fully and rapidly reusable rocket – which has never been done before – is the pivotal breakthrough needed to substantially reduce the cost of space access," according to the SpaceX announcement. "While most rockets are designed to burn up on re-entry, SpaceX is building rockets that not only withstand re-entry, but also land safely on Earth to be refueled and fly again."
The launch currently scheduled for Jan. 6 will carry supplies to the International Space Station.