# Rocket Lab Neutron

Neutron is a partially reusable medium-lift two-stage launch vehicle under development by Rocket Lab. Announced on 1 March 2021, the vehicle is designed to be capable of delivering a payload of 13,000 kg (28,700 lb) to low Earth orbit in a partially reusable configuration, and will focus on the growing megaconstellation satellite delivery market. The vehicle is expected to be operational sometime in 2025. It uses LOX and liquid methane propellant on both stages of the vehicle.

## Design

An earlier design of Neutron (March 2021), included a rocket 40 m (130 ft) tall with a 4.5 m (15 ft)-diameter payload fairing. Rocket Lab stated that they intended for the first stage of the vehicle to be reusable, with landings planned on a floating landing platform downrange in the Atlantic Ocean called Return On Investment. During the company's earnings call in February 2025, a plan to modify the offshore barge were unveiled.
On 2 December 2021, Rocket Lab unveiled a revised design for Neutron, featuring a tapered shape with a maximum diameter of 7 m (23 ft). Rocket Lab abandoned opts for a return-to-launch-site reusability profile and on a floating platform called Return On Investment. Instead of a conventional payload fairing that is jettisoned and recovered at sea, the fairing is integrated into the vehicle, and opens during stage separation to release the second stage and payload, and then closes before the first stage lands back on earth. The rocket features a unique interstage design where the second stage is "hung" from the first stage structure.
On the 22nd of September 2022, another revised design was unveiled at an investor day, with the first stage engine count increased from seven to nine, and the engine architecture changed from gas-generator to oxygen rich staged combustion. This was done primarily to allow for a lower turbine temperature, while maintaining the same specific impulse. The engine will run with a significantly lower chamber pressure than other similar engines, at the cost of some performance. The number of fairing segments was reduced from four to two.
On the 27th of July 2023, new concept art on the Rocket Lab website showed a further revised design, with a reduction in the number of payload fairing sections from 4 to 2, redesigned landing legs, and small changes to the overall shape of the rocket. The number of payload fairing sections was reduced in order to allow for simpler fairing opening mechanisms while the landing legs were redesigned in order to be optimized for landings on floating platforms, allowing for an increase in launch availability. The redesigned legs feature a folding mechanism similar to the SpaceX Falcon 9 landing legs.

## Operations

On 28 February 2022, Rocket Lab announced that Neutron will launch from the Mid-Atlantic Regional Spaceport (MARS) within NASA's Wallops Flight Facility on the eastern coast of Virginia. It was also announced that the company will build a 250,000 square feet manufacturing and operations facility adjacent to the Wallops Flight Facility. Ground was broken for this facility on 11 April 2022. As of December 2021, Rocket Lab is planning for the first launch to take place no earlier than July 2025. Test firing of Neutron's Archimedes engine occurred at NASA's Stennis Space Center in Hancock County, Mississippi.

## Development timeline

Past and future development milestones for Neutron.
| Date | Milestone | Status |
| Q2 2022 | Moulds and tooling for Neutron completed | Completed |
| Q3 2022 | Full-scale prototype hardware for Archimedes and Neutron being made | Completed |
| 4 Nov 2022 | Opening Archimedes test complex at NASA Stennis Space Center | Completed |
| Q4 2022 | Pre-burner hotfire Test of Archimedes engine for the first time | Completed |
| 10 Jan 2023 | Testing engine ignition on development hardware | Completed |
| Q1 2023 | Test stand infrastructure completed for Neutron Stage 2 tank | Completed |
| 8 Aug 2023 | First Stage 2 build | Completed |
| 4 Oct 2023 | Stage two structural and cryogenic testing | Completed |
| 6 May 2024 | First Archimedes development engine built | Completed |
| 8 Aug 2024 | First Archimedes engine hot fire | Completed |
| 2024 | Testing of all avionics and communications devices with critical onboard software and GNC algorithms | Completed |
| NET 2024 | Flight mechanisms test program | In progress |
| NET 2024 | Stage 1 build | In progress |
| NET 2024 | Stage 2 static fire | Not started |
| NET 2024 | Stage 1 static fire | Not started |
| NET 2024 | Launch complex 3 complete | In progress |
| NET 2024 | Final integration | Not started |
| NET 2024 | Wet dress rehearsal | Not started |
| NET 2025 | Launch | Not started |

## Applications

Neutron is designed to lift up to 15,000 kg (33,100 lb) while expended, 13,000 kg (28,700 lb) while landing the booster downrange and up to 8,500 kg (18,700 lb) with the first stage returning to the launch site. Rocket Lab forecasts Neutron will be able to launch 98% of all payloads launched through 2029. Rocket Lab also intends the design to be able to support constellation deployment, deep space missions, and eventually human spaceflight.

## Launches

The first flight of Neutron is expected to be in the second half of 2025.
According to Rocket Lab, Neutron’s expected debut launch in 2025 also puts the launch vehicle in a strong position to on-ramp onto the U.S. Government’s National Security Space Launch (NSSL) Lane 1 program, an indefinite delivery indefinite quantity (IDIQ) contract valued at $5.6 billion over a five-year period. RFPs for the program opened on October 30th 2024 with approved new launch vehicles to be on-ramped to the program in Spring 2025.
In November 2024 Rocket Lab announced that it has signed a multi-launch agreement with a confidential commercial satellite constellation operator to launch satellite constellation using Neutron. Under the contract, Rocket Lab will launch two dedicated missions on Neutron starting from mid-2026. The missions will launch from Rocket Lab Launch Complex 3 on Wallops Island, Virginia. The launch service agreement for these missions signifies the beginning of a productive collaboration that could see Neutron deploy the entire constellation.