An Explosion Knocked Out Anduril’s Rocket Motor Test Site in Mississippi

A rocket motor exploded during a test at an Anduril facility in Mississippi last Friday, marking another setback in the startup’s hopes of becoming a major supplier of missile propulsion systems for the defense industry. Anduril publicly confirmed the incident after an inquiry from WIRED.

No one was injured in the blast, which damaged Anduril’s testing stand, the company’s chief operating officer Matt Grimm said in a social media post on Tuesday hours after WIRED contacted the company about the incident.

Three people familiar with Anduril’s operations, who were granted anonymity to discuss a sensitive situation, tell WIRED that they can't recall another time in the past few years when a similar test resulted in an explosion, and they were unaware of what may have caused last week’s mishap. The incident halted a key step in the prototype testing work that generates revenue for Anduril's rocket motor unit, and rebuilding the setup could take up to a couple of months, one of the people says.

Grimm wrote in his post, which included photos of charred equipment, that Anduril expects to resume testing within weeks. “Anduril is continuing to build and test rocket motors weekly, and the production facility remains on schedule,” he said. “Disciplined iteration begets steady progress, and we're already putting the pieces of our test stand back together for the next test.”

Shannon Prior, an Anduril spokesperson, didn’t respond to a request to comment for this story beyond pointing to Grimm’s post.

Anduril planned to begin mass production of rocket motors on July 1, 2025, but a year later, it has not done so, four people familiar with the matter say, disputing Grimm’s contention that the effort is on schedule. A former Pentagon official who helped award a multimillion-dollar grant to Anduril previously told WIRED that he anticipated years of delays despite the company’s promises to deliver the complex technology on time. Solid rocket motor production in the US is largely controlled by just a couple of companies, leading to shortages that the Pentagon is trying to overcome by supporting startups.

Anduril has been valued at $61 billion by investors and fulfilled billions of dollars in government contracts around the world by developing drones, submarines, and surveillance gear, but its rocket motor unit based in McHenry, Mississippi, has encountered repeated challenges. In March, WIRED reported about a series of safety and technology issues at the McHenry facility, including an employee accidentally burning his hand with an igniter and the purchase of costly equipment that failed to perform as intended.

On social media, Anduril founder Palmer Luckey framed some of the incidents described in WIRED’s earlier reporting as “whining about … inane stuff.” The company’s chairman, Trae Stephens, wrote in a separate post that Anduril is "scaling faster than anyone in this industry" and "fixing problems as we find them."

Before it can begin mass-producing rocket motors in McHenry, Anduril has been generating revenue by designing, building, and testing prototype motors for customers such as the US Navy. That business earned the company tens of millions of dollars in revenue last year, according to a person familiar with the figure. Even critics of the unit say the testing business has done well. After the prototypes are built, Anduril measures how well the designs perform, including the amount of time the propellant burns. Customers get the data to inform their plans. That work may now be held up.

Mass production may not begin for another year, two people say. After WIRED’s report in March, Anduril executives such as Grimm offered to give the rocket motor unit whatever resources it needed to get going, one of the people says. Ultimately, in April, the team decided to move struggling equipment into storage and start putting together a new setup for mass production that will require a greater amount of manual labor, according to another person.

“It’s a hot mess,” says the same source. “They completely gutted the building and started from scratch what they had spent three years developing.”

Anduril got into the rocket motor business in 2023 when it acquired the defense startup Adranos, which originally established the facility in McHenry. By then, the site had already experienced a series of technical and construction problems. In 2021, a fire caused partly by improper waste disposal melted the aluminum wall of one building, according to a person familiar with the incident. In the following years, several people say that parts of other buildings and setups had to be rebuilt because of construction errors. This year, the company put off plans to buy new equipment for its in-house machining shop, which cuts and shapes raw materials, and invested the funds instead in correcting issues elsewhere, one of the people says.

The strategy shifts, production delays, and recent loss of perks such as free lunches and snacks have contributed to declining morale and several employee departures at the McHenry site, several people familiar with the matter say. Anduril has been steadily bringing in new recruits and, according to a public job listing, is searching for a new head of production in McHenry for at least the second time in a year, who will be tasked with shaping one of the company’s “most mission-critical business lines.”