Lightweight and energy-dense electric motors to power the first hybrid rocket

Each of the five hybrid Sirius engines can develop 115 kilonewtons of thrust.
Jijo Malayil
A spaceship flies into outer space
A spaceship flies into outer space


Things are on course for the most lightweight and energy-dense electric motors ever developed to power Australia's first commercial orbital launch vehicle, the Eris. If the launch is successful, it will be the first rocket ever with hybrid engines to reach Earth's orbit.

The advanced electric motors and inverters used in the project are manufactured by UK-based Equipmake in partnership with Australia's Gilmour Space. This partnership marks the foray of the former into the space industry. With expertise in weight reduction techniques, Equipmake was able to meet Gilmour Space’s stringent requirements for power and weight, which becomes a critical factor in space missions. Equipmake and Gilmour Space started working on the project in late 2020. 

"Developing the extremely lightweight, exceptionally high-energy-density electric motor and inverter unit was one of the most challenging and exciting projects we have undertaken at Equipmake," said Ian Foley, Chief Executive Officer, Equipmake, in a release.

Sirius hybrid engines to power Eris

The bespoke systems are aimed to support Gilmour's orbital-class Eris rocket engines, resulting in the formation of a hybrid rocket propulsion system. The firm had completed the final qualification test-fire of its Sirius hybrid rocket engine before Eris's proposed launch date in April 2023. "A final test conducted in early November found that each engine could generate 115 kilonewtons of thrust," said a release

The launch vehicle measures 23 meters in height and weighs over 30 tonnes. It will be powered by five hybrid engines with solid fuel and a liquid oxidizer. With Eris, a three-stage rocket, the partnership aims to provide a cost-effective and greener alternative to traditional liquid and solid propulsion rockets.

"The electric motor’s rotor uses Equipmake’s proprietary rotor design, in which the permanent magnets are arranged like the spokes of a wheel to deliver a significant performance advantage in a very challenging operating environment." Eris aims to carry a lightweight satellite into a low Earth orbit.

A milestone for Australia 

In the coming years, Gilmour Space plans to develop and launch larger rockets with payload capacities of up to 1000 kilograms into low Earth orbits. This would enable the firm to launch various missions for the Australian government and private companies.

“We’ve been using other countries’ rockets for the last 50 years, but there are a lot of restrictions. If you’ve got an Australian launch vehicle, then if you’re an Australian company or the government, you’ve basically got unfettered access,” said Adam Gilmour, co-founder of Gilmour Space, to NewScientist

A successful mission will also make Australia the 12th country in the world to successfully launch orbital space missions. The other countries on the list include the US, UK, Russia, China, Japan, South Korea, North Korea, France, Israel, India, and Iran.

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