MOJAVE, Calif. — Billionaire Virgin Galactic founder Richard Branson, saluting the bravery of test pilots, vowed Saturday to find out what caused the crash of his prototype space tourism rocket, killing one crew member and injuring another.

In grim remarks at the Mojave Air and Space Port where the craft was under development, Branson gave no details of Friday’s accident and deferred to the National Transportation Safety Board, whose team had just arrived.

“We are determined to find out what went wrong,” he said, asserting that safety has always been the top priority of the program that envisions taking wealthy tourists to the edge of space for a brief experience of weightlessness and a view of Earth below.

“Yesterday we fell short,” he said. “We’ll now comprehensively assess the results of the crash and are determined to learn from this and move forward.”

Branson added, however, that “we are not going to push on blindly.”