Electron with recovery hardware (Block upgrade)

Electron was conceived as an expendable two-stage launcher: on a small-lift rocket, every kilogram of recovery hardware comes straight out of the payload. Rocket Lab nevertheless began studying first-stage reuse internally in late 2018, after analysing the data gathered by sensors on its earlier flights, and announced recovery and reflight plans publicly on 6 August 2019. Cost was only part of the motive; reuse was also a way to meet launch demand that the production line alone would struggle to supply. The company ruled out propulsive landings of the kind SpaceX performs — it has said Electron is not large enough to carry the propellant needed for an upright landing — and chose instead to let the atmosphere slow the stage, an approach it calls the "aerothermal decelerator", whose exact details it keeps proprietary.

The first phase was pure data gathering. Flights 6 and 7 ("That's a Funny Looking Cactus" and "Make it Rain") carried instruments on the first stage to feed the reflight programme. Flight 8 ("Look Ma No Hands") added Brutus, a recorder that collected re-entry data from the first stage and was designed to survive splashdown in the ocean.

Flight 10, "Running Out Of Fingers", launched on 6 December 2019 and introduced the block upgrade that defines this configuration. The first stage gained extra guidance and navigation hardware, onboard flight computers, S-band telemetry to record and livestream data during re-entry, and a reaction control system. After stage separation the booster flipped 180 degrees and was steered through the atmosphere so that its base heat shield faced the flow at the right attitude and angle of attack. With no deceleration hardware aboard, it survived the passage through what Rocket Lab calls "the wall" and struck the ocean at 900 km/h, as planned: the goal was to prove re-entry, not to recover the stage. Flight 11, "Birds of a Feather", the first launch for the US National Reconnaissance Office, repeated the success, and no further tests of that kind were planned.

In mid-February 2020 low-altitude tests checked the parachutes, and in March 2020 a helicopter dropped an Electron test article that deployed its parachutes while a second helicopter, carrying a long boom, snagged the drogue line at 1500 m and brought the article back to land. The first real recovery came on Flight 16, "Return To Sender", on 20 November 2020: the booster made a soft ocean landing under parachute and was picked up by a vessel, while the second stage delivered thirty payloads to a 500 km Sun-synchronous orbit, among them a titanium mass simulator shaped like the garden gnome "Gnome Chompski". On Flight 20, "Running Out Of Toes" (15 May 2021), the mission was lost when the second stage shut down early, yet the first stage, fitted with an advanced heat shield based on lessons from the first recovered booster, still splashed down safely. On Flight 22, "Love At First Insight" (18 November 2021), a parachute deployed higher than before and an improved heat shield were tested, and for the first time a helicopter tracked the descent.

Flight 26, "There And Back Again", launched on 2 May 2022 (3 May local time in New Zealand) and deployed 34 satellites. After the drogue and main parachutes had opened, Rocket Lab's Sikorsky S-92 helicopter met the descending stage at about two kilometres and hooked the parachute line with a long line. The pilot then detected load characteristics unlike those seen in testing and released the stage, which splashed down and was recovered by the contracted vessel Seaworker. Peter Beck explained that the crew had about ten minutes after confirmation of a good parachute to reach the stage, which had entered from space at seven times the speed of sound. A second attempt on Flight 32, "Catch Me If You Can" (4 November 2022, carrying the Swedish MATS satellite), was called off when telemetry from the stage was lost; the helicopter backed away and the booster landed at sea. Rocket Lab later abandoned helicopter capture in favour of ocean landings.

Recovery hardware takes roughly 10–15 per cent of the payload a given launch can carry; for the heavy CAPSTONE lunar mission the first stage was stripped of it entirely. The capacity increase announced in August 2020, to 225–300 kg and driven mainly by battery advances, was meant in part to offset that mass. Ocean landings continued with "The Beat Goes On" (24 March 2023) and "Baby Come Back" (18 July 2023), which tested improved water sealing, a lighter parachute and new hardware on the recovery vessel. One recovered Rutherford engine passed five full-duration hot-fire tests and was cleared to fly, and on 23 August 2023 "We Love The Nightlife", the 40th Electron mission, flew with a refurbished Rutherford taken from the "There And Back Again" booster. "Four Of A Kind" (31 January 2024) brought back yet another first stage from the sea.