Rocket Lab Gets A Little Closer...

... to booster reuse for their light duty, orbital class booster, Electron.  Last night's launch from New Zealand of their 39th mission (7th of this year) was completely successful, including recovery of the booster, as seen in this tweet from last night.

Rocket Lab has implemented an entirely different approach to booster recovery than SpaceX; it relies on neither using residual fuel for engine burns or soft landing on a barge at sea.  Instead, after stage separation, the booster continues to coast upward in altitude to a maximum (same as the Falcon 9 first stage).  The booster uses its reaction control thrusters to orient itself to survive the intense heating that occurs from atmospheric drag during reentry; the booster eventually reaches speeds up to Mach 8, eight times the speed of sound, during descent.  Once the booster starts to enter the denser parts of the atmosphere, it deploys a drogue parachute to start dropping the speed.  Once the speed has been reduced enough, it deploys the main parachute and splashes down in the ocean.  

Main chute deployed, seconds before splashdown last night (US Eastern time).

Rocket Lab has been working on this approach for a few years and was the subject of a write-up here at the end of March.  In the lead-up to attempting a recovery that didn't involve catching the booster with a helicopter, they were clearly moving in this direction.

Murielle Baker, a Rocket Lab spokesperson, said “It turns out Electron survives a swim in the ocean well enough that many of its components actually pass re-qualification for flight, so for this mission we are putting the theory to the test of whether we need a helicopter at all.”  Part of the experiment will have the recovery ship flush critical parts of the booster, such as its Rutherford engines, with fresh water to get the salt out of areas most susceptible to the damage.  

Once the booster is back at Rocket Lab’s Auckland factory, the company will disassemble and inspect the nine main engines and remove avionics for examination and re-testing. Rocket Lab has already hot-fired a Rutherford engine recovered from an Electron flight and found it passed all tests to fly again.

I've read elsewhere that Rocket Lab's engineers did most of their changes to the booster for reuse by sealing critical areas in it, to make rinsing the saltwater out of it easier and more productive.  The trade there is that every pound of RTV silicone sealant or conformal coating added is one less pound to orbit. 

The rocket will now be brought back to New Zealand for their teams to look over the data and make adjustments for future launches. It is unlikely this rocket will fly again, but there is a high chance 1 or more of the engines could make another flight as the company marches forward to reusability of the entire first stage.