Rocket Lab announced on October 14 that it is delaying the first launch of its medium-lift Neutron rocket to 2027. The company said it found microscopic voids between carbon-fiber layers in a component that had been thickened to reinforce the first-stage propellant tank. It has not given a new launch month. The company will correct its manufacturing process and rebuild the part before moving on to testing the complete first stage.
Neutron is designed to carry up to 13 tonnes to low Earth orbit, with a reusable first stage that supports regular launches of satellite constellations. The company is struggling to establish the process on which that plan depends: building large, lightweight vehicles to consistent quality.
Voids appeared in the reinforced dome
The problem was found in the forward dome, the curved component that closes the front end of the tank. In an official development update video, founder and CEO Peter Beck said post-cure inspection revealed voids between layers, and that the company slowed production to investigate the cause. Voids can reduce a component's strength and durability. But finding them does not mean the part would necessarily fail in flight; Rocket Labs says it made the decision to proceed only after confirming the safety margins it requires.
The issue is linked to the response to a test failure earlier this year. The first-stage tank ruptured during hydrostatic testing in January. According to the investigation results Rocket Lab disclosed on page 21 of its February 26 earnings presentation, a manufacturing defect in a critical joint had reduced its strength. The company had expected the tank to pass, and had not anticipated a failure after it reached the expected flight loads.
The tank at that time had been laid up by hand by an outside contractor. That method was chosen to keep tank production moving while the company brought up its automated fiber-placement equipment. The company has since moved to automated placement and, according to Beck, also made a design change that eliminates the joint, along with reinforcement that thickens some sections.
The voids, however, appeared in those thickened sections. The company's explanation is that curing process adjustments had not kept pace with the structural change meant to strengthen the part. Summing this up as a repeat of the January defect would miss the sequence of events: while addressing the problem with the hand-laid joint, a different challenge emerged, namely properly curing the revised structure.
Rocket Lab reproduced the problem in testing and added countermeasures to its manufacturing process. Beck said the aft dome built with the new process resolved the issue, and work has moved on to rebuilding the forward dome. That, however, only supports the manufacture of parts with the improved process; testing of the full first stage still lies ahead.
Automated layup alone does not solve the large-tank problem
A carbon-fiber part is not finished simply by placing fibers on a mold. It must be cured: epoxy resin is heated so a chemical reaction binds the fibers together. In Beck's explanation, a typical autoclave heats and pressurizes a part inside a vessel to compact the layers. For Neutron's large components, the company has been developing a process that cures them without such a vessel, along with heating conditions tailored to each part.
In other words, automation that lays fibers quickly and accurately and a process that cures the part without leaving internal defects must each be made to work separately. Thickening a structure to reinforce it does not automatically guarantee quality after curing.
NASA and Boeing's past development work confirms that manufacturing quality can be a challenge for large composite tanks. In a 2015 conference paper, tanks 2.4 m and 5.5 m in diameter were made with automated layup equipment and cured without an autoclave. They underwent pressure and temperature cycling tests using liquid hydrogen, and the larger tank was also tested under simulated flight loads.
The paper discusses how voids are associated with microcracking and hydrogen permeation, and argues that reducing voids is also necessary to secure interlaminar shear strength near joints. The researchers said the work reduced technical risk for large tanks, but also listed improving layup quality and manufacturing speed as remaining challenges. Building and testing a tank once and refining a process to produce tanks each have their own points to verify.
NASA's tank was designed for liquid hydrogen, and its materials and load conditions differ from those of Neutron, which uses liquid oxygen and methane. Its test results cannot be applied directly to determine whether Neutron passes or fails. For Neutron, the company must confirm the curing conditions that suit its chosen materials and geometry, and show that those conditions deliver the required quality.
First-quarter 2027 is a tank-testing target
In its August 10 earnings release, Rocket Lab said first-stage tank production was on track for its target of delivering the vehicle to the launch site in the fourth quarter of 2026. The October video spelled out the work that must be completed before a new launch date is given.
The August target was delivery to the launch site by year-end, but the October explanation moved the expected completion of first-stage assembly and tank testing to the first quarter of 2027.
| Announcement / stage | Target or outlook stated at the time | Relationship to first flight |
|---|---|---|
| Aug. 10: Vehicle delivery to launch site | Q4 2026 | A delivery goal, separate from conducting a launch |
| Oct. 14: Forward dome manufacturing, curing, inspection | Before the start of Q1 2027 if all goes well | Ultrasonic and other checks for voids or other problems |
| Oct. 14: First-stage assembly, hydrostatic and cryogenic testing | Within Q1 2027 if all goes well | Verification of the complete first stage |
| Oct. 14: First launch | 2027, no specific date | A new target date is expected to be set based on progress in the steps above |
Source: Rocket Lab's August 10 announcement and the October 14 video, 4:30–5:10. The table lines up the schedules as announced for each stage and is not a calculation of days of delay for the same stage.
This first-quarter benchmark, January through March, cannot be read as a flight schedule. The sequence is to finish inspecting the forward dome, assemble it, and then verify that first stage under pressure and at cryogenic temperatures. The next hurdle is whether the improvement seen with the aft dome holds for the rebuilt forward dome and then for the assembled first stage.
Customers are waiting for what comes after the first flight
Commercial customer Kepler Communications announced on August 10 that it plans its first dedicated launch on Neutron for 2028 or later. The mission would deploy next-generation satellites that add optical communications and on-orbit computing capacity. The news that Neutron's first flight has moved to 2027 does not by itself establish that this 2028-or-later mission has slipped.
For U.S. military customers, a track record of success carries its own meaning. The announcement by the U.S. Space Force's Space Systems Command on on-ramping to NSSL Phase 3 Lane 1 in 2025 explained that Rocket Lab and Stoke Space become eligible to compete for individual launch service orders after a successful first launch. Selection into the framework is separate from winning individual missions. Under that condition, a successful first flight is the entry point to the next round of competition.
Rocket Lab is aiming for a vehicle that can fly again and again. Under the official design, the 43 m tall, 7 m diameter Neutron opens its nose fairing to release the second stage inside, and the first stage, with the fairing closed again, returns to sea. The plan is also to reuse the fairing together with the first stage, putting the weight savings from lighter components toward satellite payload capacity.
According to Beck, the company is building out its factory and equipment in parallel with completing the first vehicle, and has already begun building the second and third. The company plans to use the delay period to bring forward improvements intended for future flights. For such advance investment to translate into a steady supply of vehicles, the improved process must repeatedly deliver the required quality.
For now, the inspection of the forward dome and the hydrostatic and cryogenic tests of the assembled first stage will show how far that premise holds. The results will give customers waiting for Neutron the basis for judging its next launch schedule.