Video showed the rocket barely cleared the top of the launch tower, briefly hovering above the ground before running out of steam.
The 23m vehicle – designed to launch small satellites into low-Earth orbit – was launched from Abbot Point, about 1000km up from the Queensland capital Brisbane.
The payload for the test flight was a jar of Vegemite, a popular Australian toast topping, strapped inside the rocket’s nose cone.
Gilmour said preparations for a second test flight were already under way, with a view to launching within the next “six to eight months”.
“It’s huge what you can prove with just 10 to 15 seconds of flight time,” he said.
He added: “I’m sorry to say the Vegemite didn’t make it.”
The company, which has 230 employees, hopes to start commercial launches in late 2026 or early 2027.
-Agence France-Presse