A flight test of a hypersonic missile system in Hawaii ended in failure due to a problem that took place after ignition, the US Department of Defense said, delivering a fresh blow to a program that has suffered stumbles, Bloomberg reported.

It didn’t provide further details of what took place in the test, but said in a statement sent by email “the Department remains confident that it is on track to field offensive and defensive hypersonic capabilities on target dates beginning in the early 2020s.”

“An anomaly occurred following ignition of the test asset,” Pentagon spokesman Navy Lieutenant Commander Tim Gorman said in the statement.

The trial marked the second unsuccessful test flight of the prototype weapon known as Conventional Prompt Strike. There was a booster failure in its first flight test in October, which prevented the missile from leaving the launch pad. The Conventional Prompt Strike weapon is envisioned to be installed on Zumwalt destroyers and Virginia-class submarines.

The US Army is developing a land-based version.