As Sequoia Capital’s first defense tech investment, Mach Industries is an industry darling, raising over $80 million since its founding in 2023. Its founder, Ethan Thornton, now 21, began Mach as a teenage MIT student before dropping out to focus full-time on his startup.

But a few months before landing a seed investment from Sequoia in the summer of 2023, Mach had a major setback: a hydrogen gun prototype it was building exploded, sending hundreds of pieces of shrapnel flying and injuring a team member, Forbes first reported.

Speaking to TechCrunch during his appearance at StrictlyVC in San Francisco on April 3, Thornton addressed the incident publicly for the first time, saying it happened due to a lack of safety resources.

“At the time, we were trying to self-fund it, and we didn’t have the money to sort of run these procedures the way they should have been,” he said.

After the explosion, Mach Industries “essentially shut down all work” until it raised funds from Sequoia Capital, Thornton said. Now, with those resources secured, Thornton says Mach has a full safety team and is working with the US military to develop new weapons.

The startup has also pivoted away from its initial focus on hydrogen, a gas that’s famously volatile. Speaking at StrictlyVC, Thornton said hydrogen was “probably a bad tech bet” that required further development. But the pivot hasn’t fazed Mach–far from it. 

Now, Mach is building different kinds of weapons altogether, such as a new cruise missile and a bomb called “Glide” that can be fired from the edge of space. It also recently landed a U.S. Army contract and announced plans for a network of decentralized factories it calls “Forge.”

“Building a lot of prototypes” is a key part of why VCs have poured $85 million into the company, according to Thornton.

“It’s not necessarily my ability to build these things, but more so our ability to actually work with the federal government to get programs of record built around them,” he remarked.