Pulsar Fusion has achieved first plasma in the exhaust test system of its Sunbird nuclear fusion rocket, marking an early step toward a propulsion technology with the potential to dramatically reduce interplanetary travel times.
During the test plasma was confined within the exhaust architecture of the Sunbird system using electric and magnetic fields to guide and accelerate charged particles through the exhaust channel.
Plasma is superheated ionized gas and is the only state of matter which allows atomic nuclei to overcome their natural electrostatic repulsion and fuse.
The UK-based company demonstrated the milestone live during a technical session at Amazon’s MARS Conference in Ojai, California, presented by Pulsar Fusion CEO Richard Dinan. The test was performed by Pulsar scientists at the company’s facility in Bletchley, UK, and live-streamed to the conference stage during Dinan’s presentation.
“The Sunbird program showcased this milestone live in California at the MARS Conference, hosted by Jeff Bezos, which was an exceptional moment and a genuine privilege,” said Richard Dinan, CEO of Pulsar Fusion. “There is no greater platform to share this first test than here, surrounded by an esteemed group of world leading machine learning and robotics academics/entrepreneurs, Nobel laureates, astronauts. I am grateful to the MARS Conference and Jeff Bezos.”
Krypton was used as the propellant for the initial test series, selected for its relatively high ionization efficiency and inert characteristics at the mass flow rates required for early testing.
Krypton is increasingly recognized as a viable alternative propellant for plasma-based propulsion systems. As reported in this ATI feature on spacecraft propulsion, sources of xenon, the conventional propellant for electric thrusters, are running low, making heavier alternative gases an important area of research for the sector.
The next steps for the Sunbird fusion rocket program
The next development phase will see Pulsar gather detailed performance data, including thrust and exhaust velocity measurements, using a thrust balance, E×B probes and retarding potential analyzer (RPA) instruments. This data will enable the company to plan the first Sunbird mission.
Pulsar’s engineers also plan to do experiments that will incorporate rotating magnetic field heating, radio frequency heating systems and a dedicated thrust balance to enable more detailed performance measurements.
The company also plans to upgrade the engine to rare-earth, high-temperature superconducting magnets, enabling stronger magnetic fields and the exploration of higher plasma density and pressure conditions. This upgrade ultimately aims to support experimental work with aneutronic fusion fuel cycles as part of continued Sunbird development.
To maximize the mission lifetime of Sunbird, Pulsar has developed a research program in collaboration with the UK Atomic Energy Authority to study the effects of neutron radiation on the reactor walls and magnets, a primary cause of wear within the reactor
Pulsar Fusion’s technology roadmap
The first plasma milestone represents the latest progression in Pulsar’s long-term strategy to combine its nuclear fusion research with its electric space propulsion business. The Bletchley, UK-based company began constructing what it described as the largest practical nuclear fusion rocket engine ever built in 2023, with plans to fire an 26ft (8m) wide fusion chamber.
The company has also built and tested a 10kW Hall effect thruster (HET) at the University of Southampton as part of a project for the UK Space Agency, developing the thruster to be combined with a nuclear reactor. Pulsar is backed by the UK Space Agency and the European Space Agency.
Nuclear fusion propulsion for space travel
Fusion propulsion has the potential to deliver both high thrust and high exhaust velocities, a combination that current propulsion technologies cannot achieve individually. Chemical rockets generate high thrust but relatively low exhaust velocities, limiting ultimate spacecraft speed, while electric propulsion systems such as ion or Hall thrusters achieve high exhaust velocities but produce very low thrust.
If realized, the technology could accelerate the transportation of materials and components for deep-space infrastructure, where transport speed is directly tied to operational and economic efficiency.
