SYDNEY, May 15, 2025 (BSS/AFP) - An Australian aerospace firm said Thursday it has delayed a historic first attempt to launch a locally developed rocket into orbit, with a jar of Vegemite as its payload.

Gilmour Space Technologies said a ground system glitch forced it to postpone the first test launch of its three-stage Eris rocket by a day until Friday.

"The issue was with an external power system we use during system checks," communications chief Michelle Gilmour told AFP.

"We've identified the fix but ran out of time to implement it and fuel the rocket within today's launch window."

The rocket has a multi-day launch window to fly from a spaceport near the east coast township of Bowen, about 1,000 kilometres (600 miles) up from the Queensland capital Brisbane.

If successful, it would be the first Australian-made rocket to make an orbital launch from Australian soil.

The 23-metre (75-foot) vehicle is designed to launch small satellites into low-Earth orbit but on the first launch it will carry a jar of Vegemite -- a popular Australian toast topping.

Chief executive Adam Gilmour said the firm is not expecting things to go smoothly on the first test.

If it orbits Earth "I would probably have a heart attack, actually, because I'll be so surprised, but deliriously happy", Gilmour told AFP this week.

"We're going to be happy if it gets off the pad -- 10, 20, 30 seconds of flight time: fantastic. So orbit is just not in the realm of my belief right now, even though it's theoretically possible."

The rocket design is for a capacity of 100-200 kilogrammes (220-440 pounds), with further upgrades being developed.

Weighing 30 tonnes fully fuelled, it has a hybrid propulsion system, using a solid inert fuel and a liquid oxidiser, which provides the oxygen for it to burn, Gilmour said.

Gilmour Space Technologies is backed by private investors including venture capital group Blackbird and pension fund HESTA.

The company, which has 230 employees, hopes to start commercial launches in late 2026 or early 2027, Gilmour said, and then to rapidly grow revenues.