Catch a falling missile and bring it back to shore…
On Tuesday (Monday night in New York), Rocket Lab, a small rocket company, delivered the first half of that feat during its final launch from New Zealand’s east coast.
After sending a payload of 34 small satellites into orbit, the company used a helicopter to capture the rocket’s 39-meter-long, used booster stage before it splashed into the Pacific Ocean.
In the future, Rocket Lab hopes to refurbish a restored booster and then use it for another orbital mission, a feat so far only accomplished by one company: Elon Musk’s SpaceX.
A video stream from the helicopter showed a long cable dangling from the plane with a cloudy sky below. Then the booster came into view, dangling under the parachute.
“There we go, we have our first glimpse of it,” said Murielle Baker, the commentator on the Rocket Lab broadcast. The grappling hook on the end of the helicopter’s cable chopped the parachute line before the captured booster swung and left the camera view.
Cheers from Rocket Lab’s mission control initially confirmed a successful catch.
However, the company later released an update that qualified the success. Rocket Lab chief executive Peter Beck said on Twitter that the helicopter pilots reported that the booster was not hanging under the helicopter quite the same way it did during test flights and that they let it go to plunge into the ocean, where it was recovered by a Rocket Lab ship.
Ultimately, Rocket Lab would like the helicopter to transport a captured booster all the way back to land and avoid saltwater damage that makes booster reuse challenging and potentially impractical.
Rocket Lab gives most of its missions whimsical names. This one was called “There and Back Again”, a nod to the booster’s recovery and the subtitle of JRR Tolkien’s novel “The Hobbit”. Director Peter Jackson’s trilogy of Hobbit films was shot in New Zealand.
Rocket Lab’s booster catch is the latest development in an industry where rockets used to be expensive disposable items. Reusing all or part of a rocket helps reduce the cost of delivering payloads to space and can speed up the rate of launch by reducing the number of rockets to be manufactured.
“Eighty percent of the cost of the entire rocket is in that initial phase, both in materials and labor,” Rocket Lab CEO Peter Beck said in an interview on Friday.
SpaceX pioneered a new era in reusable rockets and now regularly lands and flies the first stages of its Falcon 9 rockets. The Falcon 9’s second stages (as well as Rocket Lab’s Electron rocket) are still being discarded, mostly burning up as they re-enter Earth’s atmosphere. SpaceX is designing its next-generation super rocket, Starship, to be fully reusable. Competitors such as Blue Origin and United Launch Alliance, and companies in China, are similarly developing missiles 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 airplane-like operations.
For the Falcon 9, the booster fires multiple times after being detached from the second stage, slowing it down slowly towards a spot on a floating platform in the ocean or on land. The Electron is a much smaller rocket, which makes reuse more challenging.
“You have to use all your propellant to get missions going,” Mr. Beck said. That ruled out the possibility of propulsive landings like the Falcon 9 boosters.
Instead, Rocket Lab engineers came up with a more fuel-efficient approach, adding a system of thrusters that expels cold gas to orient the booster when it falls, and thermal shielding to protect it from temperatures over 4,300 degrees Fahrenheit.
The booster separated from the second stage at an altitude of about 80 miles, and during the descent it accelerated to 5,200 miles per hour.
“For example, if we landed flat, on the side, the rocket would just burn,” said Mr. Beck. “So we need to orient and control that first stage to put down the heat shield and motors throughout the flight profile.”
The friction of the atmosphere acted as a brake. About 7 minutes, 40 seconds after takeoff, the speed of the booster’s fall slowed to less than twice the speed of sound. At that point, a small parachute called the drogue was deployed, adding additional resistance. A larger main chute further slowed the booster to a slower pace.
Rocket Lab had shown on three previous launches that Electron boosters can survive the return. But during those missions, the boosters splashed into the ocean and were taken out for research.
This time, a Sikorsky S-92 helicopter hovering in the area encountered the booster in mid-air and dragged a rope with a grappling hook across the line between the pilot and the main parachutes.
With almost all of its propellant consumed, the booster was much lighter than at launch. But it was still a heavy piece of metal—a cylinder four feet in diameter and about the height of a four-story building and weighing nearly 2,200 pounds or a metric ton.
mr. Beck said Rocket Lab would eventually like to capture boosters for about half of its missions. The extra weight of the thrusters, parachutes and thermal protectors reduces the 550-pound payload by 10 to 15 percent.
Later this month, Rocket Lab could launch CAPSTONE, a NASA-funded but privately operated mission, that will study a highly elliptical path around the moon that will be used by a future US space station on the moon. Rocket Lab hopes to open a second launch site on Wallops Island in Virginia before the end of this year.
