The pursuit of nuclear fusion has captivated some of the brightest minds worldwide for many years. The appeal is clear — replicating the energy production of stars right here on Earth could mean almost limitless clean power. Despite numerous attempts and some key advancements, this dream remains unfulfilled, and we are probably still years away from witnessing a functioning fusion power plant on Earth.
Conducting fusion reactions in space may appear to add complexity to an already intricate technology, but it could potentially happen sooner than on Earth. Furthermore, it might enable spacecraft to reach speeds of up to 500,000 miles (805,000 kilometers) per hour — surpassing the record set by NASA’s Parker Solar Probe, which reached 430,000 miles (692,000 kilometers) per hour.
With backing from the UK Space Agency, a British startup called Pulsar Fusion has introduced Sunbird, a space rocket concept meant to rendezvous with spacecraft in orbit, attach to them, and propel them to their destinations at astonishing speeds using nuclear fusion. Pulsar’s founder and CEO, Richard Dinan, explains, “It’s very unnatural to do fusion on Earth. Fusion doesn’t want to work in an atmosphere. Space is a far more logical, sensible place to do fusion because that’s where it wants to happen anyway.”
As of now, Sunbird is in its early construction stages and faces significant engineering hurdles, but Pulsar aims to achieve fusion in orbit for the first time by 2027. If the rocket becomes operational, it could potentially halve the travel time of a future mission to Mars.
Nuclear fusion differs from nuclear fission, the process powering existing nuclear plants. Fission involves splitting heavy, radioactive elements like uranium into lighter ones using neutrons, releasing immense energy to generate electricity. Fusion, on the other hand, involves merging very light elements like hydrogen under high temperature and pressure to create heavier elements. “The sun and the stars are all fusion reactors,” Dinan notes. “They are element cookers — transforming hydrogen into helium — creating the heavy elements that form everything as they die. Ultimately, the universe is mostly hydrogen and helium, with all other elements cooked in a star through fusion.”
Fusion is highly sought after because it produces four times more energy than fission and four million times more energy than fossil fuels. Unlike fission, fusion does not rely on dangerous radioactive materials, instead utilizing deuterium and tritium, heavy hydrogen atoms with extra neutrons. Fusion reactors would operate on small amounts of fuel and produce no hazardous waste.
However, initiating fusion requires significant energy input to replicate the conditions found in a star’s core — extreme temperature and pressure, along with effective confinement to sustain the reaction. The primary challenge on Earth has been generating more energy from fusion than is needed to initiate the reaction, with limited success so far.
While numerous organizations are researching nuclear fusion as a power source on Earth
The main goal of Sunbird is to achieve faster exhaust speed by utilizing nuclear fusion reactions that occur within a plasma, which is a hot, electrically charged gas. Unlike reactors on Earth, Sunbird would employ linear magnets to heat up the plasma and create the necessary conditions for the fuel to fuse together. This innovative approach would allow for efficient propulsion without generating neutrons from the fusion reaction, as seen in traditional reactors. Instead, Sunbird would utilize a more costly fuel known as helium-3 to produce protons for propulsion.
Although the Sunbird process may be costly and impractical for energy production on Earth, its value lies in saving fuel costs, reducing spacecraft weight, and significantly decreasing travel time. Sunbirds would operate similarly to city bikes at docking stations, allowing for recharging and maintenance before embarking on interplanetary journeys. The aim is to have stations strategically placed near destinations like Mars and low Earth orbit for efficient travel back and forth.
Pulsar, under the leadership of CEO Richard Dinan, is conducting fusion propulsion tests using a vacuum chamber to simulate space conditions. The company plans to conduct an in-orbit demonstration this year to validate the functionality of key components. By 2027, they aim to launch a small portion of the Sunbird prototype to confirm the feasibility of their fusion propulsion concept.
While the initial prototype will serve as a linear fusion experiment costing around $70 million, a fully functional Sunbird is projected to be ready in four to five years pending adequate funding. Initially intended for satellite transportation in orbit, Sunbird’s true potential lies in interplanetary missions. Examples include delivering cargo to Mars in under six months, deploying probes to outer planets within a few years, and expediting asteroid mining missions.
Other companies, such as Helicity Space and General Atomics, are also exploring nuclear fusion engines for space propulsion. With the aerospace industry’s growing interest in fusion technology, Pulsar aims to be a pioneering force in achieving practical fusion propulsion for space exploration.
Pulsar Fusion has developed a new propulsion system that they plan to test in space in 2027. This system aims to provide a more efficient means of propulsion for a crewed mission to Mars compared to existing options. According to Aaron Knoll, a senior lecturer specializing in plasma propulsion at Imperial College London, there is significant potential in utilizing fusion power for spacecraft propulsion. While fusion energy is not yet a viable technology for power generation on Earth, Knoll highlights that it can already be harnessed for spacecraft propulsion without waiting for further advancements. He explains that, unlike on Earth where energy output must exceed energy input, any energy output from fusion power in space can enhance thrust and efficiency, even if it is less than the energy supplied.
Despite the promise of fusion propulsion, there are considerable technical challenges in adapting fusion technology for space use. Current fusion reactor designs are bulky and require a range of supporting equipment, necessitating substantial efforts to miniaturize and streamline these systems for space applications. Bhuvana Srinivasan, a professor at the University of Washington specializing in Aeronautics & Astronautics, acknowledges the potential of nuclear fusion propulsion for spaceflight. She highlights the possibility of using this technology to establish a lunar base in a single mission, revolutionizing space exploration capabilities. Srinivasan also emphasizes the importance of compactness and lightness in fusion propulsion systems, underscoring the additional engineering hurdles that must be overcome.
Srinivasan envisions fusion propulsion as a transformative advancement that could enable humans to venture farther into space and revolutionize uncrewed missions, particularly for resource gathering on celestial bodies like the Moon. She notes the potential abundance of helium-3, a valuable fusion fuel, on the Moon, which could be crucial for deep space exploration missions launched from a lunar base. This access to rare resources could open up new opportunities for planetary and interstellar exploration, providing not only scientific and exploratory benefits but also potential economic and societal advantages that are yet to be fully realized.
