Early Tuesday morning, the California firm SpaceX will launch a resupply mission carrying 5,000 pounds of food and experiments to the International Space Station.
But just as important as the stuff going up is what comes back down.
The rocket's massive first stage — a metal tube 14 stories high — won't just drop into the ocean as other rockets do. Instead, it will deploy fins that will allow it to maneuver as it falls. It will then fire its engines in order to gently settle onto an unmanned barge in the Atlantic.
"If we can recover the stage intact and re-launch it, the potential is there for a truly revolutionary impact," SpaceX CEO Elon Musk said in April at the National Press Club. Musk said that recycling the rocket stages could cut the cost of space flight by a factor of 100.
Trying to reuse the stages of a rocket isn't a new idea. The space shuttle's massive solid-rocket boosters used parachutes to return to the ocean. But the boosters had to be extensively refurbished before flying again.
SpaceX's vertical landing trick is far more ambitious. Bringing the rocket down in one piece means it could, in theory, be refueled and reused almost immediately.
But vertical landing is also far more risky. The company says that keeping the rocket stage vertical as it falls is like "trying to balance a rubber broomstick on your hand in the middle of a wind storm." On top of that challenge, the massive stage has to slow down from speeds of nearly a mile a second without the aid of parachutes.
SpaceX has had some success in two previous tests. A flight in April saw the first stage successfully fire just before touching the ocean, but rough seas destroyed it shortly after it hit the water. A second attempt in July also made a soft landing on the water, though the rocket stage was damaged after it toppled into the ocean.
This time, SpaceX has deployed a floating drone barge. The rocket will attempt to touch down on the barge, where it will be recovered. Hans Koenigsmann, SpaceX's vice president for mission assurance, says the tricky part will be hitting the relatively small barge.
He puts the odds of success around 50/50.