Rocket Lab prepares to recover the main stage of its launcher mid-flight

During Electron’s last mission, on November 18, 2021, Rocket Lab took advantage of the return under parachute of the main stage of the small launcher to demonstrate the capabilities of thehelicopter recovery to follow and get close enough to the stage to capture it in flight. The maneuver did not go to the end. It was not the goal. As expected, the stage ended its flight by landing on the ocean. It was only a demonstration.

After its separation with the top stage of Electron, the main stage turned around towards the ocean under parachute. He once again performed a controlled “dive” into the ocean, from where he was recovered. While parked 370 kilometers off the point of impact, Rocket Lab’s recovery helicopter successfully followed the return from the stage. During its descent, the floor reached a speed maximum speed of around 10,000 km / h, while maintaining communications with the Rocket Lab control and recovery building stationed at sea.

Rocket Lab teams joined the floating stage on the ocean to secure it and prevent it from sinking approximately 80 minutes after the launcher took off, halving the time taken during previous recoveries to reach the stage. The floors that are not currently reused are brought back to the Rocket Lab production complex in Auckland, New Zealand, where they are reviewed in order to prepare for future refurbishment operations in order to be reused.

An unprecedented aerial capture

After the success of this demonstration, Rocket Lab is done with the landings. Make way for much more serious things with the mid-flight recovery of the stage with the help of a helicopter which will carry additional fuel tanks to guarantee it sufficient flight time to fly behind the stage, catch it in full flight and bring it back to dry land. This first attempt is scheduled for the first half of 2022.

For this mid-flight capture, the stage will need to be modified. It will be equipped with a thermal protection system applied to the entire stage and to its nine Rutherford motors to help it withstand the high temperatures which can reach up to 2,400 degrees Celsius during the start of the school year. The parachute will be reinforced and modified with the addition of an engagement line so that the helicopter can capture it.

A more difficult recovery than it seems

As surprising as it may seem, it is more complicated to recover a small stage than a large one, in particular because its constructive index is high. This index measures the dry mass ratio of the floor to the mass of propellants embedded. The higher this index, the greater the heat flow. As a result, the stage will enter like a ball, which certainly explains the choice of recovering it in flight rather than landing it on solid ground or on a open sea platform, as it does so well SpaceX ! Conversely, a larger stage will have a lower constructive index and therefore will brake much better than a small stage.

Rocket Lab will retrieve the main stage of the Electron launcher by helicopter

Article by Remy Decourt published on 08/08/2019

A pioneer and now a leader in the reuse of launcher stages, SpaceX has paved the way and shown that this is technologically possible. Although the economic equation of this reuse has not yet been resolved, Rocket Lab is embarking on this path and wants to make its Electron launcher partially reusable … using a helicopter!

the Rocket Lab Electron Light Launcher, capable of launching payloads of 150 kilograms into orbit sun-synchronous, ideal for meeting the needs of theEarth observation, could become partially reusable. Rocket Lab has just announced its intention to recover and reuse the main stage of its launcher, which costs around $ 5 million. This stage uses nine Rutherford engines that run on a mixture of oxygen liquid and of kerosene.

This choice is dictated by economic considerations. It is also made possible by SpaceX which has technologically demonstrated that the reuse of a floor was possible. In addition, satellite operators are now much more inclined than yesterday to use second-hand launchers to launch their satellite.

SpaceX, pioneer of reuse

That said, the difficulty of carrying out this program should not be underestimated. As surprising as it may seem, it is more complicated to recover a small stage than a large one, in particular because its constructive index is high. This index measures the dry mass ratio of the stage and the mass of the propellants on board. The higher this index, the greater the heat flow. Result, the floor will enter like a ball, which certainly explains the choice to recover it in flight rather than landing it on solid ground or a open sea platform, as SpaceX does so well! Conversely, a larger stage will have a lower constructive index and therefore will brake much better than a small stage.

To limit the costs of this adaptation (the stage was developed as a conventional consumable stage), the latter will therefore not use a landing system like the SpaceX Falcon 9 for example, whose motors are used to bring the floor back to the ground which arises by deploying legs. The idea of ​​Rocket Lab is to use a helicopter instead of such a system. After separating from the upper floor, the main floor will descend into theatmosphere and deploy a parachute, in order to reduce its speed. At the appropriate time, the helicopter will catch it by the cable that connects it to the parachute.

In June, during a commercial flight, an Electron launcher had carried a few instruments allowing it to collect data specific to its recovery efforts. The same will be true for an upcoming launch later this month, with a view to making a first attempt at recovery later this year.