Scientists have toyed with the idea of nuclear rockets since the 1950s. Will they finally become a reality?

UK startup Pulsar Fusion just revealed a nuclear fusion-powered rocket that could halve travel time across the solar system.

The spacecraft, called ‘Sunbird’, is designed to remain in orbit for quick deployment. It attaches to larger rockets, speeding them to distant worlds in a fraction of the time.

On its website, Pulsar Fusion claims Sunbird can fly 1000–2000 kg of commercial cargo to Mars in roughly four months.

Meet ‘Sunbird’

Pulsar Fusion’s Sunbird spacecraft acts somewhat like a space tug. In a concept video shared on the company’s website, Sunbird can be seen attaching to a Starship-like rocket before powering it to Mars.

Using existing technologies, NASA estimates it would take seven to eight months for a rocket such as Starship to reach Mars. According to Pulsar Fusion, its new spacecraft could cut this travel time dramatically.

The company claims it could propel a spacecraft with a mass of about 1,000kg (2,200lb) to Pluto in four years. As a point of reference, NASA’s New Horizon spacecraft took roughly eight years to reach the distant planet. Using Sunbird for an Earth to Saturn mission would take approximately two years, according to the firm. A trip to Mars, meanwhile, would take as little as four months.

Sunbird is powered by Pulsar Fusion’s in-development Duel Direct Fusion Drive (DDFD). This is a compact nuclear fusion engine that provides thrust and power. According to the information available on Pulsar Fusion’s website, DDFD provides a specific impulse of 10,000–15,000 s and 2 MW of power. When fired up, it would temporarily become the hottest place in the solar system, producing exhaust speeds of more than 500,000mph (804,672km/h).

Pulsar Fusion started developing the engine in 2023 at its headquarters in Milton Keynes, UK. Static tests are set to “begin in 2025 followed by an In Orbit Demonstration (IOD) of the core technology components in 2027”.

Are nuclear rockets the future of space travel?

Scientists and engineers have floated the idea of nuclear rockets around since the 1950s. They would roughly double the efficiency of traditional chemical rockets while delivering much higher thrust than ion propulsion systems.

Cutting down travel time is an incredibly important goal for the space industry. Lower travel times are crucial for astronaut health due to higher exposure to cosmic radiation during transit.

Historically, though, the issue with nuclear propulsion has been the funding required to develop these advanced systems. Long-term development has often been cut short due to budget cuts. These have led NASA to focus on programs that would provide a faster return on their investment.

NASA’s NERVA program, for example, was cut in 1973, despite promising results. It was cut due to budget cutbacks and a call to focus on the Space Shuttle program.

In a 2023 interview with IE, former NASA astronaut and Ad Astra founder Franklin Chang Diaz said funding was the main stumbling block to sending his nuclear electric propulsion engine to orbit. “The technology is there,” he explained, “[but] the timeline for when we’ll see a VASIMR demonstration in space is all dependent on the funding.”

Pulsar Fusion is collaborating with the Universities of Cambridge and Southampton, as well as the Nuclear Advanced Manufacturing Research Centre (AMRC). In 2022, the company secured funding from the UK Space Agency.

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