How Rocket Lab Recovered Electron’s First Stage From Space
On Rocket Lab’s most recent mission, it ended with the first stage of the Electron rocket slowly falling into the ocean. Interestingly, this was exactly what the company was planning and hoping to happen. For years now Rocket Lab has been trying to figure out how to consistently and efficiently reuse the first stage of a small lift launch vehicle.
Due to the size and fuel margin, a lot of other reuse options are off the table such as a propulsive landing which SpaceX commonly uses with Falcon 9. This is a big reason why Rocket Lab is trying to prepare the rocket for reuse in the factory with heat shields, waterproofing, etc. On the most recent recovery mission just over a week ago, the first stage had a difficult journey between stage separation and splashdown.
This process takes minutes of time and puts the first stage up against immense forces and heat. All of which Rocket Lab needed to account for in order for Electron to splashdown in one piece. Here I will go more in-depth into the dangerous journey between stage separation and splashdown, how the first stage held up, the future reuse timeline, and more.
Launch To Splashdown
On July 17th, during Rocket Lab’s 39th Electron mission, called “Baby Come Back” Electron deployed seven satellites to space before attempting a controlled first stage descent and splashdown. Soon after spalshdown, Rocket Lab and CEO Peter Beck provided different pictures and video of the recovery event. For example, Rocket Lab tweeted saying, “Launch, rinse, repeat. Electron is another step closer to becoming the first reusable small rocket.” This included a close-up of the first stage being removed from the water.
Focusing on this image, you can see that for the most part, the first stage is in great condition. Physically it’s intact and the only noticeable damage is to the paint job toward the bottom of the stage. Something you would expect to happen after reentering the Earth’s atmosphere. In reality, a lot happened between stage separation and this point.
At two and a half minutes after launch, at an altitude of ~80 km, Electron’s first and second stages separated as planned. The second stage continued on to orbit and successfully deployed the 7 satellites on board. Meanwhile, the fun really began for Stage 1 as it commenced its descent. Re-entering Earth’s atmosphere is a brutal experience. Rocket Lab knew Electron’s first stage would be subjected to intense pressure and heat, experiencing flow temperatures in excess of 2400 °C and reaching speeds of 2350 m/s during its descent. They call this potentially destructive process ‘The Wall.’
One of the ways we set out to survive ‘The Wall’ was by using a reaction control system (RCS) to position the stage as it falls. Using the RCS they are able to reorient the stage to an ideal angle as it descends. They’ve tested the RCS on a few previous missions and data showed good positioning, but there’s nothing like getting the stage back to prove it. On this mission, Stage 1 reoriented very well, with the RCS performing nicely to position the stage for the perfect re-entry angle of attack.
After decelerating to <Mach 2, and around 7 minutes 40 seconds after lift-off, the drogue parachute on Electron’s first stage was deployed to increase drag and stabilize the stage as it descended. During Electron’s final few kilometers of descent, the large main parachute successfully deployed and further slowed the stage and enabled a controlled splashdown. The parachute system behaved perfectly, with expected descent rates, correct timings on deployment events, and nice clean parachute deployments. From there, Rocket Lab’s recovery team rendezvoused with the stage on the water, successfully bringing it onto a vessel using a specially designed capture cradle. The stage is now en route back to Rocket Lab’s production complex for analysis ahead to inform future recovery missions, and eventually re-flight of an Electron.
After the splashdown, Peter Beck was quoted saying, “We’re delighted to have delivered yet another successful Electron mission and would like to thank the teams at Space Flight Laboratory, Spire Global, and NASA, for entrusting us with their innovative science and tech demonstration missions. With this mission we’ve made big strides toward reusability with Electron and we are now closer than ever to relaunching a booster for the first time.”
Rocket Lab Recovery
The main goal, and what Rocket Lab has been working toward for years is not to just recover the booster but refurbish and launch it again. By now the company has recovered a few boosters but never launched one a second time. The reason is they are simply not ready. Within the booster is a long list of important components from the Rutherford engines to the heat shield and even various electronics. All of which the company needs to test after reentry and exposure to salt water before they are confident it can be reused.
Until all this data is gathered we won’t see a reused Electron booster lift off. This being said, they are making very fast progress now that a set plan is in place. For example, in the past Rocket Lab was trying a few different methods such as catching the stage out of mid-air with a helicopter. This involved a lot of practice and during the two actual attempts, didn’t work quite well. However, now with a set plan in place, they have already made specific reuse upgrades to the booster for this exact application.
On this recent launch, the company put a lot of focus on getting to Electron’s booster as fast as possible, and removing it from the water quickly as well. Even with efforts to waterproof the stage, the less time it’s in the ocean the better off Rocket Lab is.
“There are some internal vehicle changes to improve its ability to keep water out of the areas where we don’t want it,” said Peter Beck, in an interview. “We’ve taken this next opportunity to improve the watertightness of the vehicle.” He also commented that the new method of getting Electron out of the water “makes it much simpler to recover and much less likely to damage the stage during recovery.”
Beck said the company is taking a “methodical” approach to reusability, making incremental steps that get it closer to full reuse. “I’m sure we’ll learn something from this mission and we’ll probably make some tweaks again to the next one. We’re methodically walking step-by-step and taking the opportunity to get it right.” He added that while reusability was an “important economic lever” for the company, it was not an urgent requirement. The company has previously emphasized that reusability would allow it to increase launch activity without having to scale up its factory. This highlights that while Rocket Lab is absolutely trying to reuse the first stage, it’s not a top priority that the company depends on. This will likely contribute to the timeline and how long before we see a reused booster lift off.
In the coming months, we can expect a few more booster splashdown attempts each with a slightly upgraded Electron booster. Until they get this process perfect, they will continue to try. All this being said, besides the progress made on the recent flight, the company has already tested and made clear that the engines can be reused.
Late last year, Rocket Lab successfully test fired a reused Rutherford first stage engine for the first time – a significant technical achievement in the Company’s efforts to make its Electron launch vehicle the world’s first reusable orbital small rocket.
Rocket Lab conducted the full duration, full-thrust test fire of the refurbished Rutherford engine at the Company’s engine test facility. The engine was previously successfully launched to space and returned to Earth during Rocket Lab’s recovery mission, ‘There And Back Again’, launched on May 2, 2022. The mission was the first time Rocket Lab attempted a mid-air capture of Electron’s first stage, using parachutes on the rocket to slow its descent from space before a helicopter plucked the rocket from the sky as it approached Earth’s surface. The Electron stage was ultimately released for a soft ocean splashdown, before it was collected by vessel and returned to Rocket Lab’s production complex. In other words, similar to the recent recovery the entire booster including its Rutherford engines were exposed to the water.
Despite this, the refurbished Rutherford engine passed all of the same rigorous acceptance tests Rocket Lab performs for every engine, including 200 seconds of engine fire and multiple restarts. Data from the test fire shows the engine produced full thrust of 21kNs within 1000 milliseconds of ignition and performed to the same standard of a newly-built Rutherford engine. This Rutherford engine will now continue as an engine life-leader for future Rutherford development.
Rocket Lab founder and CEO Peter Beck said: “We’ve always been at the forefront of innovation with Electron, having pushed the boundaries of many technologies including carbon composites, electric turbo-pumps and 3D printed rocket engines. Now, we’re leading the pack once again bringing reusability to small launch vehicles. Being able to refly Electron with minimal refurbishment is the ultimate goal, and so the fact that the recovered components on this engine performed on the test stand with minimal rework is further validation that we’re on the right path.”
Conclusion
Rocket Lab is continuing to push forward toward Electron partial reusability. If successful, this would be a very big deal and contribute to a significant increase in launch cadence and reduced costs. We will have to wait and see how it progresses and the impact it has on the space industry.