Today at 4:33 PM ET, after SpaceX launches a resupply mission to the ISS, it will attempt to land the Falcon 9 rocket on a drone platform at sea. Here, in a feature from the May 2015 issue of Popular Mechanics, we explain how the wild landing works, step by step.
On the video it looks like a rocket launch played on rewind: A slender, fourteen-story aluminum-lithium-alloy tube, engines spouting fire, comes to Earth instead of roaring into space. Then, calamity. The footage from January shows the rocket veering at a too-sharp 45-degree angle, then exploding. That was the fiery end to the initial attempt by Space Exploration Technologies (SpaceX) to land the first stage of a Falcon 9 rocket for reuse on an unmanned ship floating in the Atlantic off Florida's coast. The day was technically not a failure. The second stage of the Falcon 9 delivered its payload to the International Space Station on behalf of NASA. But everyone was far more interested in what happened afterward, with the "autonomous spaceport drone ship" landing, because of what it could mean for the space industry.
Today's launch systems drop spent stages into the sea, but SpaceX and other private space companies want to fly them down to Earth—or a barge on the ocean—and reuse them. SpaceX officials say this could drive launch costs from about $60 million down to $7 million, and thus change the way the world industrial- izes—and possibly colonizes—space. "That will lead to space travel being just as easy and inexpensive as traveling from New York to London is today," says James Pura, director of the Space Frontier Foundation.
SpaceX determined that the crash was caused by an inadequate supply of hydraulic fluid during the flight's last few minutes. The fluid powers fins that help steer and stabilize the rocket. Engineers set to work preparing to try again, and on Monday afternoon, April 13, they will. Here's how the process will work. (Click to expand.)
1. Launch and stage separation
A two-stage Falcon 9 rocket rises from its launchpad, and at an altitude of fifty miles the first-stage booster separates. The payload continues into space, riding on the second stage. The first stage coasts to about a hundred miles in altitude, then begins to descend.
2 Boost-back burn
Three of nine engines from the first stage reignite. The rocket has its own guidance- control system, which gimbals (orients) the Merlin 1D engines to rotate the rocket between 120 and 180 degrees. This aims the rocket toward the drone ship. The booster is traveling at nearly 3,000 miles per hour.
3. Supersonic retro-propulsion burn
The center engine ignites to slow the descent and gimbals itself to help the booster become fully vertical. Four grid fins extend to stabilize and further brake the cylinder. Each moves independently to control roll, pitch, and yaw. The rocket's speed drops from 3,000 miles per hour to about 560.
4. Landing burn
The engines initiate a final burn to slow the craft to about five miles per hour. Four carbon-fiber-and- aluminum-honeycomb landing legs unfold, powered by compressed helium.
5. Touchdown and recovery
The booster lands on the floating pad. Technicians on a vessel positioned miles away head over to board the drone ship and secure the rocket to the deck with metal shoes and vent any leftover gases. The drone ship ferries the first stage to shore, where it can be processed, cleaned, and reused. Flight length: about nine minutes. ￼
6. Floating landing pad
The drone ship is equipped with a dynamic positioning system that uses azimuth- thruster engines to keep it at a specific GPS point hundreds of miles (in the case of the January test, about 200 miles) away from the launchpad, give or take ten feet. ￼