Explosion halts Anduril’s Mississippi rocket motor testing, delaying mass production

An explosion during a rocket motor test at Anduril’s facility in McHenry, Mississippi, last Friday damaged the testing stand and halted prototype testing, a key revenue-generating activity for the company’s rocket motor unit. Anduril confirmed the incident after inquiry from WIRED, stating no one was injured. The company’s chief operating officer, Matt Grimm, shared photos of the damaged equipment in a social media post, noting that Anduril expects to resume testing within weeks.

The blast occurred as Anduril worked to transition from designing and testing prototype rocket motors to mass production, originally planned to begin on July 1, 2025. However, four people familiar with the matter told WIRED that mass production has yet to commence a year later, contradicting Grimm’s claim that the facility remains on schedule. One source estimated that rebuilding the testing setup could take up to two months, further delaying the resumption of critical testing activities.

Anduril acquired the McHenry facility in 2023 when it purchased the defense startup Adranos, which had established the site. Since then, the facility has faced repeated technical and operational challenges. In 2021, a fire caused by improper waste disposal melted an aluminum wall in one building. Subsequent years saw construction errors requiring rebuilding of parts of other buildings and setups. Earlier this year, the company postponed plans to purchase new equipment for its in-house machining shop, reallocating funds to address other issues instead.

The rocket motor unit has generated tens of millions of dollars in revenue for Anduril by designing, building, and testing prototype motors for customers such as the US Navy. This work involves measuring performance metrics like propellant burn time and providing data to customers. The explosion and subsequent halt in testing may disrupt this revenue stream. Sources familiar with the matter described the current state of the facility as chaotic, with one calling it a "hot mess" after the company decided to dismantle struggling equipment and start anew with a setup requiring greater manual labor.

Morale at the McHenry site has declined amid production delays, operational setbacks, and the loss of workplace perks like free lunches and snacks. Several employees have departed, and the company is actively recruiting for a new head of production—a role that has been posted at least twice in the past year. The facility’s challenges have raised concerns about Anduril’s ability to meet the Pentagon’s demand for diversified suppliers of missile propulsion systems, particularly as the defense startup seeks to expand its role in the industry.