New hybrid rockets prepare for inaugural flights

By Trevor S. Elliott and Joseph Majdalani|December 2023

The Hybrid Rockets Technical Committee studies techniques applied to the design and testing of rocket motors using hybrid rocket systems.

This was a year characterized by remarkable advancements in hybrid rocket technology across the globe. New space ventures and research institutions pushed boundaries while achieving significant milestones and propelling the industry forward.

German startup HyImpulse drew attention with the qualification tests of its HyPLOX75 hybrid rocket engine. Powered by paraffin and liquid oxygen, this engine has a 30-second burn duration and 75 kilonewtons of thrust. In August, the engine passed two vital qualification tests, verifying that the technology is ready to power the SR75 sounding rocket. The SR75 was designed as a suborbital technology demonstrator that would host microgravity payloads. Hy-Impulse plans to conduct the inaugural launch of an SR75 in early 2024. The company said in November that the inaugural launch would be conducted from Australia, but plans call for at least two future launches from the United Kingdom. In July, the U.K. Civil Aviation Authority granted HyImpulse a license to launch an SR75 from SaxaVord Spaceport in the Shetland Islands.

In Australia, Gilmour Space Technologies prepared for the inaugural launch of its hybrid-powered Eris orbital rocket, fueled by the 120-kilonewton Sirius hybrid rocket engine. That launch is scheduled to occur from a private site in northern Queensland. The Sirius engine, which completed flight qualification testing last year, is to propel both the first and second stages of the Eris. A Phoenix liquid-propellant engine is to power the third stage. During the unveiling of the Eris at Gilmour’s production facility in May, Australian Prime Minister Anthony Albanese hailed the rocket as the nation’s first domestically produced orbital launch vehicle. Pending regulatory approvals, Gilmour is targeting a launch window that would open in December from the Bowen Orbital Spaceport, Australia’s commercial orbital launch site.

Taiwan’s National Cheng Kung University, specifically the Satellite and Rocket Propulsion Laboratory, also contributed significantly to global advancements in hybrid rocket technology. Building on their past experience, researchers are targeting late this year or early 2024 for the inaugural launch of a 10.5-meter-tall sounding rocket with a 29-kilonewton thrust first-stage engine and a 14-kilonewton thrust second stage engine. Each engine is to be fueled by a hydroxyl-terminated polybutadiene, paraffin and nitrous oxide propellant. Anticipated to weigh around 700 kilograms, this rocket is projected to reach an altitude of 80 kilometers while carrying up to 50 kilograms of suborbital science experiments. To prepare for the inaugural launch, SRPL researchers developed and launched pilot sounding rockets in 2019 and 2022 to validate their two-stage rocket technology.

These milestones demonstrate the breadth of innovation and dedication underlying the field of hybrid rocket technology as well as the continued efforts and ingenuity of engineers driving the field forward. If all goes as planned, we are on an exciting trajectory for the future of space exploration.