Neutron on pad
Rocket Lab's Neutron features a distrinctive design the company says is intended to enable the vehicle to be rapidly reused and be cost-competitive with other medium-class rockets. Credit: Rocket Lab

WASHINGTON — Rocket Lab released new details Dec. 2 of the design of its Neutron medium-class rocket, a vehicle with a unique design the company says is intended to enable frequent and low-cost reuse.

Rocket Lab unveiled the updated design of Neutron in a brief video presentation. The vehicle, made of carbon composite materials, is seven meters wide at its base, standing on fixed landing legs, and gradually tapers. That design intended to reduce heat loads on the vehicle during reentry before landing back at the launch site.

Rather than jettison the rocket’s payload fairing during launch, the “Hungry Hippo” fairing opens in four parts. Neutron then releases a lightweight, expendable upper stage with the payload before the fairing closes and the stage reenters. The vehicle will be able to place 8,000 kilograms into low Earth orbit while recovering the first stage, or up to 15,000 kilograms if the first stage is expended.

Neutron will be powered by a new engine called Archimedes, using methane and liquid oxygen propellants and generating about 225,000 pounds-force of thrust. The first stage will have seven Archimedes engines while the upper stage will have a single vaccum-optimized version of the engine.

“We’ve really optimized the vehicle from day one to be reusable. Every decision is based around that,” Peter Beck, chief executive of Rocket Lab, said in an interview.

That includes, he said, a design decision early on to be able to turn around that first stage for another launch within 24 hours of landing. “Not because I intend to relaunch the vehicle every 24 hours, but it drives all of the design decisions,” he said.

That design requirement, he said, led to decisions such as having the rocket return to the launch site rather than land on a barge. It was also a factor in the use of methane fuel rather than kerosene, as the latter creates soot that takes time to clean from engines.

While Archimedes is a new engine design, Beck said the company deliberately decided not to push the envelope in terms of its performance. “That’s an area where we’re not innovating,” he said. “What we’re trying to do is build an engine that is hugely reliable and can fly again and again.”

Instead, Rocket Lab is focusing on the structure of the vehicle. It will use carbon composite materials, as it does with the Electron rocket, but using a new technology called automated tape laying that enables composite structure to be built at rates of meters per minute. He noted that, by comparison, metallic 3D-printing technologies produce structures at the rate of millimeters per minutes.

“Poor mass efficiency in structures drives a requirement for high-performance engines, so if you can be really mass efficient in your structures, then you get to cheat on your engines,” Beck said, allowing the company to avoid what he called a “circle of doom” where increased mass of a vehicle component requires more propellant, which increases the mass of tanks and other structures.

Other companies, such as SpaceX when developing its Starship vehicle, have rejected composites because of their high costs versus metals like stainless steel. “Composites get a bad rap from people who don’t know how to make composites,” he said. “Our approach is incredibly fast and incredibly cost efficient.”

When Rocket Lab announced Neutron in March, the company said the first launch would be in 2024 from Wallops Island, Virginia. The company did not state a launch date or location in the Neutron update video presentation.

Beck said in the interview that 2024 remains the target date for a first launch. “It is a very steep development program to climb,” he said, but added that the company will take advantage of technologies previously demonstrated on Electron, from avionics to valves, for Neutron. The funds the company raised by going public through a SPAC merger will be sufficient to pay for Neutron’s development. “We hope to have something on the pad in 2024 and we’ll be pushing very aggressively to try to meet that.”

The company said in a statement it is “currently working through a competitive process to select launch site, rocket production facility and Archimedes engine test facility on the U.S. East Coast,” but Beck didn’t give a schedule for selecting it.

Rocket Lab has started to talk with potential customers of the vehicle, including those planning satellite constellations that Neutron is optimized to deploy. Beck mentioned interest from the U.S. Space Force, which awarded Rocket Lab $24.3 million in September to support work on Neutron’s upper stage.

Beck declined to give a launch price for Neutron, but said it would complete with other vehicles in its class on price. “There would be no point in building this vehicle if we didn’t think we could be incredibly cost-competitive with everything that is currently in operation and everything that is proposed.”

The Neutron design revealed in the video is different from what the company showed in March when it announced the vehicle. That earlier design looked like a more conventional launch vehicle with some similarities to the Falcon 9, notably landing legs folded against the side of the first stage.

“The Neutron rendering we put out was a very traditional launch vehicle. It would work, but it wasn’t achieving what we wanted to achieve,” he said of that original concept. “Partly we wanted to spend more time refining our design. Partly we’re sick of people copying us, so we just put something out there that people could copy all they want and it wouldn’t matter.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...