Catch a falling rocket and bring it back to shore …
On Tuesday, Rocket Lab, a small company with a small rocket, pulled off the first half of that feat during its latest launch from the east coast of New Zealand.
After sending a payload of 34 small satellites to orbit, the company used a helicopter to catch the 39-foot-long used-up booster stage of the rocket before it splashed into the Pacific Ocean.
“Pretty, pretty epic day,” Peter Beck, the chief executive of Rocket Lab said during a news conference a few hours later. “The difficulty in capturing a stage is, is pretty extreme.”
In the future, Rocket Lab hopes to refurbish a recovered booster and then use it for another orbital mission, an achievement that only one company has so far pulled off: Elon Musk’s SpaceX.
A video stream showed a long cable dangling from the helicopter with cloudy skies below. Then the booster came into view dangling under the parachute.
“There we go, we’ve got our first glimpse of it,” said Murielle Baker, the commentator during the Rocket Lab broadcast. The grappling hook at the end of the helicopter’s cable snagged the parachute line before the captured booster swung and exited the camera view.
Cheers from Rocket Lab’s mission control confirmed a successful catch.
However, the company later provided an update that qualified the success. Mr. Beck, said that the helicopter pilots reported that the booster was not hanging below the helicopter quite in the same way as during test runs and that they let go.
“If the pilots were unhappy at any point, that’s what they were instructed to do,” Mr. Beck said. “Then the stage continued under parachute at a low descent rate and splashed down in the ocean.”
A Rocket Lab ship pulled the booster out of the water. Eventually, the company would like the helicopter to carry a caught booster all the way back to land and prevent damage from salt water.
Mr. Beck did not rule out the possibility that it could be reused. “It’s still my hope that you’ll see this vehicle back on the pad again,” he said.
Rocket Lab gives most of its missions whimsical names. This one was called “There and Back Again,” a nod to the recovery of the booster as well as the subtitle of J.R.R. Tolkien’s “The Hobbit” novel. The trilogy of Hobbit movies by director Peter Jackson was shot in New Zealand.
Rocket Lab’s booster catch is the latest advance in an industry where rockets used to be expensive single-use throwaways. Reusing all or part of one helps lower the cost of delivering payloads to space and could speed the pace of launching by reducing the number of rockets that need to be manufactured.
“Eighty percent of the costs or thereabouts of the rocket is actually in the first stage,” Mr. Beck said in an earlier interview. “So the economics for us are really good. It’s certainly worthwhile doing.”
SpaceX pioneered a new age in reusable rockets and now regularly lands the first stages of its Falcon 9 rockets and flies them over and over. The second stages of the Falcon 9 (as well as Rocket Lab’s Electron rocket) are still discarded, typically burning up while re-entering Earth’s atmosphere. SpaceX is designing its next-generation super rocket, Starship, to be entirely reusable. Competitors like Blue Origin and United Launch Alliance, and companies in China, are similarly developing rockets that would be at least partially reusable.
NASA’s space shuttles were also partially reusable, but required extensive and expensive work after each flight, and they never lived up to their promise of airliner-like operations.
For the Falcon 9, the booster fires several times after it separates from the second stages, slowing it en route to a setting down softly on either a floating platform in the ocean or a site on land.
As a much smaller rocket, the Electron needs to use all of the propellant to lift the payload to orbit. That ruled out the possibility of propulsive landings like the Falcon 9 boosters.
Instead, Rocket Lab engineers figured out a more fuel-efficient approach, adding a system of thrusters that expels cold gas to orient the booster as it falls, and thermal protection to shield it from temperatures exceeding 4,300 degrees Fahrenheit.
The booster separated from the second stage at an altitude of about 50 miles. It then continued to coast upward another 10 miles before beginning to fall, accelerating to 5,200 miles per hour.
“If you don’t have the stage orientated perfectly with the heat shield down, then basically as the re-entry process begins, it’s like a big ball of plasma,” Mr. Beck said. “It’ll basically shred the stage.”
The friction of the atmosphere acted as a brake. Around 7 minutes, 40 seconds after liftoff, the speed of the booster’s fall slowed to under twice the speed of sound. At that point, a small parachute called the drogue deployed, adding additional drag. A larger main parachute further slowed the booster to a more leisurely rate.
Rocket Lab had demonstrated on three earlier launches that Electron boosters can survive re-entry. But on those missions, the boosters splashed in the ocean and were then pulled out for examination.
This time, a Sikorsky S-92 helicopter hovering in the area met the booster midair at an altitude of 6,500 feet, dragging a cable with a grappling hook across the line between the drogue and main parachutes.
With almost all of its propellant expended, the booster was much lighter than at launch. But it was still a weighty piece of metal — a cylinder four feet in diameter and about as tall as a four-story building and weighing nearly 2,200 pounds or a metric ton.
Mr. Beck said he expected that the unexpected load issue would be resolved with more drop tests. The Sikorsky is capable of lifting up to five metric tons, far more than the weight of the booster. “It’s tiny detail,” he said.
Eventually Rocket Lab would like to catch boosters for about half of its missions, Mr. Beck said. Some missions cannot use a reusable booster because the payloads are too heavy. The added weight of the thrusters, parachutes and thermal protection reduces the payload of 550 pounds by 10 to 15 percent.
Other missions have constraints like an instantaneous launch window or a night launch that make catching the booster impractical.
The next couple of Electrons headed to the launchpad do not include the apparatus needed for recovery of the booster. That includes the rocket that is to launch CAPSTONE, a NASA-financed but privately operated mission that will study a highly elliptical path around the moon to be used by a future American lunar space station.
But there is another Electron with a reusable booster on the factory production floor that could be used soon, Mr. Beck said.
“Certainly today has given us just extreme confidence to get on with it,” he said.