A helicopter caught and released a rocket this week
Here's why Rocket Lab attempted the tricky move with a falling rocket stage, and how the maneuver works.
Late in the morning of May 3, a rocket blasted off into the heavens from a launchpad in New Zealand. Minutes later, as its second stage continued upwards towards orbit, the first stage of the rocket descended by parachute into the waiting hook from a recovery helicopter. The hook snagged the parachute line, where it was held—and then released. The launch, both a successful orbital delivery and useful feature test for rocket-maker Rocket Lab, highlights a future possible form of recoverable rocket launches.
At the heart of Tuesday’s launch was the novel recovery attempt. Getting to orbit is expensive work, and the ability to recover and reuse rocket components can lower the costs of each launch. Recovery in this instance was attempted by a Sikorsky helicopter.
“At 6,500 ft, Rocket Lab’s Sikorsky S-92 helicopter rendezvoused with the returning stage and used a hook on a long line to capture the parachute line,” Rocket Lab said in a release. “After the catch, the helicopter pilot detected different load characteristics than previously experienced in testing and offloaded the stage for a successful splashdown.”
For this specific launch, the catch ended up being more of a catch-and-release, but that attempt still went an important way to demonstrating the viability of the option. Knowing that the release worked—that the helicopter crew was able to snag the rocket and then determine they needed to jettison the booster—is a key part of proving viability. A method that involves helicopters but jeopardizes them pairs reusability with risk to the human crew.
Rocket Lab founder and CEO Peter Beck noted that it’s a tricky dynamic. “Once we receive confirmation that we’re under a good chute, we’ve got about 10 minutes to get on station and rendezvous with the stage,” he said, on a media call, “and not only rendezvous with the stage in a position in space but also in altitude and a descending altitude, a kind of three-dimensional problem if you will.”
[Related: SpaceX’s first paying ISS passengers say they’re not ‘space tourists’]
This launch, said Rocket Lab in the release, “is the first time a helicopter catch attempt was introduced to recovery operations and today’s mission will inform future helicopter captures.”
In addition to the helicopter snag, the rocket booster was slowed by its initial drogue parachute, as well as by a large main parachute. The drogue parachute stabilized and slowed the booster as it fell, with the main parachute deployed much closer to impact, working as a harder brake. Both parachutes were deployed by the time of the helicopter intercept.
“Trailing behind the main chute is the little drogue chute with a 150-foot line and there’s a 150-line hanging off the helicopter with the capture mechanism,” said Beck. “It’s kind of like Ghostbusters in a way, you want those two streams to cross, those streams being the helicopter long line and the line between the main chute and the drogue chute—those cross and grapple and capture, and then the helicopter slowly decreases the velocity of its descent.”
In this instance, after recovery from the ocean, the rocket booster stage was collected and sent back to where the company produced it for future analysis.
“It’s an incredible display of logistics and moving pieces. To even get something that’s entering from space at seven times the speed of sound on a ballistic arc to rendezvous with a helicopter was a huge achievement,” said Beck. “We got an image of it on a boat coming home. Little bit wetter than we hoped but incredibly successful.”
The company has a long history of adapting from imperfect initial results. When Rocket Lab sent its first Electron rocket up in 2017, the rocket did not quite make it into orbit as planned.
Since then, Rocket Lab claims it has had 26 Electron rocket missions, deploying a total of 146 satellites. Of those, 34 were deployed with the latest launch, and those include satellites that Rocket Lab says are “designed to monitor light pollution, demonstrate space junk removal technologies, improve power restraints in small satellites, validate technology for sustainable satellite systems that can avoid collisions with untrackable space objects, enable internet from space, and build upon a maritime surveillance constellation.”
The company primarily launches small satellites suitable for constellations. It is, and has been since at least 2016, deliberately targeting launches at a scale that doesn’t make sense for larger rockets. For example, SpaceX uses large recoverable rocket boosters, which reserve fuel to have a blast-slowed descent. This return approach, which can be done on launch pads or on special drone-landing platform ships at sea, restarts the rocket engines as they approach the surface for a controlled touchdown (when everything goes smoothly). Blue Origin does something similar.
So why doesn’t Electron just do it the same way SpaceX does? According to CNN, “[t]he company has said Electron is not large enough to carry the fuel supply needed for an upright landing, and a saltwater ocean landing can cause corrosion and physical damage.”
[Related: Jeff Bezos is suing NASA. Here’s why.]
Reusing boosters saves on materials cost, and it also saves on manufacturing time. Provided the rocket is not too badly damaged from seawater, refurbishing is a faster turnaround to readiness than starting from scratch.
If the helicopter hook technique can succeed in the future, a guided and slowed descent shortens that turnaround time even further, making it increasingly likely the company will be able to field as many launches as it schedules and population orbit with more and more satellites.
In the video of the capture attempt, filmed from a camera mounted on the helicopter, the hook can be seen dangling in the air below, a yellow tether suspended in air. The booster, parachute deployed, drifts into the frame. The sky below orbit is vast, full of room for trial and error. The successful snag is the story Rocket Lab is actively telling about the test, but the release of the cord to save the helicopter proves the concept can be attempted again, now with pilots who know what a catch and release feels like.
Watch the recovery attempt below: