A Closer Look At Rocket Lab’s Helicopter Recovery Method
Rocket Lab has been on the road to partial recovery and reusability for years now. Starting back in 2020 the company began testing Electron booster maneuvers and controlled water landings after stage separation. This process eventually led to multiple mid air catch attempts using a helicopter and a trailing parachute engagement line. However, there have been two missions where this was the goal and neither was able to successfully catch and control the rocket stage.
This brings up the question of is this process something Rocket Lab can consistently improve on and complete in the future. Not to mention the fact that small lift launch vehicle reusability is a lot less rewarding financially than larger rockets. All of which are important factors that Rocket Lab needs to consider going forward.
With all this being said, the company is very confident in this process and partial Electron reusability. By now they have already completed many different tests with recovered components such as the Rutherford engine that provided promising results. Here I will go more in-depth into Rocket Lab’s reusability history, whether or not this process is worth it, what to expect in the future, and more.
Past Attempts
On 6 August 2019, Rocket Lab announced recovery and reflight plans for the first stage of Electron, although plans had started internally from late 2018. Electron was not originally designed to be a reusable launch vehicle as it is a small-lift launch vehicle but was pursued due to an increased understanding of Electron’s performance based on analysis of previous flights through sensors on the vehicle. In addition, reusability was pursued to meet launch demands. Before Rocket Lab attempted to catch Electron out of the air, they first made sure that they could get the Electron booster to slowly and safely land in the ocean.
This first attempt occurred years ago in November 2020, with the Return to Sender mission. This mission was intended to mark a major milestone apart of Rocket Lab’s plan to make Electron a reusable launch vehicle. During the coast, a reaction control system re-oriented the first stage 180-degrees. This put the stage at the ideal angle for reentry, enabling it to survive incredible heat and pressure during its descent back to Earth. After decelerating to Mach 2, a drogue parachute was deployed to stabilize the stage. Finally, the main parachute was deployed and the stage splashed down in the ocean where Rocket Lab recovered it.
This was Rocket Lab’s 16th mission and a promising start to the recovery program. Next on the 20th and 22nd missions, the company attempted the same recovery and splashdown to ensure they were ready for an actual catch attempt. This led to May of last year when launched from Pad A at Rocket Lab Launch Complex 1 on New Zealand’s Mahia Peninsula, the “There And Back Again” marked the company’s 26th Electron launch. This mission was a recovery mission where, for the first time, Rocket Lab attempted to catch Electron’s first stage as it returned from space under parachutes using a helicopter.
After launching to space, Electron’s first stage returned to Earth under a parachute. 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. However, soon after the catch, Rocket Lab reported that the helicopter pilot detected different load characteristics than previously experienced in testing and offloaded the stage for a successful splashdown. The stage was then loaded onto Rocket Lab’s recovery vessel for transport back to the Company’s production complex for analysis and assessment for re-flight as planned. Despite the drop in the ocean, Rocket Lab saw the mission as a success and mentioned that the mid-air capture was a major milestone in Rocket Lab’s pursuit to make Electron a reusable rocket to increase launch frequency and reduce launch costs for small satellites.
Finally, we have the most recent attempt only months ago during the Catch Me If You Can mission. Similar to the previous attempt, the goal was to catch Electron’s booster out of mid air using a helicopter. In this case, the company was once again unsuccessful. Specifically, Rocket Lab reported that they had planned to attempt a mid-air capture of Electron’s first stage with a helicopter if conditions allowed. However, not all requirements were met to ensure a successful capture due to a brief telemetry loss with Electron’s first stage during its atmospheric re-entry. Due to this, the helicopter was moved out of the capture zone per standard safety procedure. On the bright side, the Electron first stage completed a safe splashdown, and Rocket Lab’s recovery vessel brought it onboard and back to Rocket Lab’s production facility for inspection and analysis.
Future Reusability
Now that we know more about Rocket Lab’s history of attempting to recover and catch Electron’s booster, we can take a closer look at the difficulty of this process, and what it means going forward. Rocket Lab CEO Peter Beck has said, “Bringing a rocket back from space and catching it with a helicopter is something of a supersonic ballet. A tremendous number of factors have to align and many systems have to work together flawlessly.” In another similar quote he stated, “Bringing a rocket back from space is a challenging task and capturing it mid-air with a helicopter is as complex as it sounds. The chances for success are much smaller than that of failure because many complex factors that must perfectly align.” Based on these quotes it’s clear that Rocket Lab understands how difficult this process is.
In an effort to increase launch opportunities and reduce manufacturing costs, Rocket Lab believes it can evolve Electron into the world’s first and only reusable and operational small rocket. Using a modified Sikorsky S-92 large helicopter, Rocket Lab attempts to capture the Electron rocket’s first stage mid-air as it returns from space after launch. The helicopter is a large twin engine vehicle typically used in offshore oil and gas transport and search and rescue operations. A closer look at the mission profile gives a better idea of this process and all the parts that need to work together. Shortly before lift-off, the customized Sikorsky S-92 recovery helicopter will deploy to the capture zone at sea, approximately 160 nautical miles off New Zealand’s Banks Peninsula. Once launched, Electron’s first and second stages will separate at approximately T+2:32 minutes into the mission. The payload will continue to orbit onboard the rocket’s second stage while Electron’s first stage descends back to Earth.
At this point in the mission, Electron’s return is expected to reach speeds of up to 8,300km (5,150 miles) per hour and temperatures of up to 2,400 degrees C (4,352 F). At approximately T+7:20 minutes after lift-off, Electron’s first parachute will deploy followed shortly after by the rocket’s main parachute. The double deployment of parachutes helps to slow the returning first stage to 0.4% of its top speed during descent: from 8,300km per hour to just 36km per hour. As Electron enters the capture zone, Rocket Lab’s recovery helicopter will match the rocket’s speed and descent from above, attempting to secure the trailing parachute engagement line to the helicopter via a hook at the end of a long line. Once captured and secured, Electron will be transported back to land and to Rocket Lab’s Auckland Production Complex. There, technicians will receive and prepare the stage for inspection to assess its suitability for re-use. With this process in mind, it helps demonstrate all the moving pieces.
Looking a few months in the past highlights some progress Rocket Lab has made regarding rocket refurbishment. While catching the booster out of mid air is not easy and so far not close to consistent, water landings offer some benefits. In September of 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 recent recovery mission, ‘There And Back Again’, launched on May 2, 2022. As we know, 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. 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. While the future of Rocket Lab catching Electron’s booster out of mid air is not guaranteed, the company could make progress with consistent water recoveries and refurbishment.
Conclusion
Rocket Lab has been working on partial reusability on Electron for years now. In that time period, they completed multiple water landings and failed to catch and return the booster on two separate attempts. We will have to wait and see how it progresses and the impact it has on the space industry.