Rocket Lab won't be launching Neutron in '26

It stuck me as ironic when I saw the headline about the Neutron's First Launch slipping again this evening, because we had just put up a little reference to the Neutron back on October 5 saying it wasn't slipping.

The last thing I published about the Neutron was just over three weeks ago, August 11, and the focus was on their goal to launch the new rocket before the end of this year. While they didn't say anything like, "2026 ain't happening; the new date is ..." the deadline is squeezing them, but they haven't given up on it.

They announced today that their Neutron launch vehicle won’t fly until 2027, citing an issue discovered during manufacturing of the rocket’s carbon composite fuel tanks. This probably falls into the category of being a news story because it's a statement by Rocket Lab CEO Peter Beck. It was pretty widely known that they were being pushed to their limits with this vehicle and entering domains of the industry they're not experts in. 

Peter Beck, Rocket Lab’s founder and CEO, identified a manufacturing defect as the reason for Neutron’s latest schedule slip. The problem lies in the dome sections at the ends of the rocket’s first stage propellant tanks.

“Recently, we identified an issue with the manufacturing process for the propellant domes specifically, and this caused us to delay production and investigate further,” Beck said in a video released by Rocket Lab.

This is leading to some probably inevitable discussion of whether or not they know what they're doing with carbon fiber construction. Carbon composite structures, are generally low weight, high strength, and corrosion resistance. But it's not like laying down metal tubes and joining pieces together, and especially not when designed for ultimate strength to weight ratios with minimum amounts of the carbon fiber cloth and epoxy. They want the epoxy to completely cover every graphite thread, but not one gram of epoxy more.

Engineers discovered voids, or air pockets, between layers of carbon fiber that make up the domes’ composite structure. Carbon composite manufacturing involves laying down carbon fiber layers in a mold, then curing, or heating, the material to bind the fibers together. But this is a tricky process, especially for large structures that won’t fit into an autoclave, a high-pressure thermal curing chamber common in modern aerospace factories.

The Neutron rocket’s first stage is the “largest pressurized structure ever made out of carbon composite,” Beck said. “Because of its scale, we’ve had to develop new out-of-autoclave processes to build Neutron, and this includes custom cure cycles for the very large pieces, like the forward and aft domes for the propellant tanks on Stage One.”

They believe that these voids came from an attempt to fix an issue found after a Neutron propellant tank unexpectedly ruptured during a hydrostatic pressure test in January, a failure blamed on a manufacturing defect at a “critical join” in the tank.

Propellant tank domes inside Rocket Lab’s Neutron factory. Credit: Rocket Lab

Rocket Lab said the problem appears to be solved after modifying the manufacturing process again. An aft propellant dome made with the updated procedure passed inspection.

“We’ve solved the problem,” Beck said. “That gives us complete confidence to move forward with the new forward dome. That process to make a new forward dome, combining with all the time that it took to investigate, identify, and resolve the issue, has pushed Neutron’s first launch date to next year.”

Rocket Lab's Electron, small payload-class rocket, has been very successful and made them one in the industry to keep your eyes on. The Electron rocket is 3.9 feet in diameter, capable of putting 660 pounds into Low Earth Orbit, while the new Neutron measures 23 feet across at its widest point and will be capable of putting 29,000 pounds into LEO. That's quite a step up. 

I think it's a bit unfair to emphasize their failures and ignore their successes in the Neutron development. They've achieved quite a lot, but still have more than a little bit left to go. As a rough guess, say they're around 80% done. The remaining work could go quickly. Or not. 

They still have lots to do before they can do the first launch. The one that sounds biggest is qualification of the rocket’s methane-fueled Archimedes engine, nine of which will power the Neutron booster. They reported in August that it was heading into the “final stretch” of engine qualification testing. 

Once that is complete, teams will begin the launch campaign on Virginia’s Eastern Shore. Launch campaigns for new rockets often take months before a first flight, involving multiple integrated fueling tests, countdown rehearsals, and a static fire.

Engineers often discover new problems during integrated testing, requiring repeat tests and tweaks to procedures and hardware on the launch pad and the rocket. ...

And that's why they do such testing. 

Neutron seem to be being designed "from the ground up" to be a competitor to SpaceX's Falcon 9, reusable and similar payloads. It looks like Neutron will be hitting the market as Falcon 9 is being retired - as SpaceX has talked about doing soon as they move more toward Starship. 

Illustration of Rocket Lab's Neutron with the "Hungry Hungry Hippo" system delivering an upper stage with payload. Image credit: Rocket Lab