NASA could send probe to 'potentially habitable' exoplanet 4 light years from Earth

NASA could one day send a fusion-powered probe to Proxima Centauri b - a potentially habitable exoplanet located just over four light years from Earth - with new research indicating the mission could be completed within a single human lifetime. Proxima b, discovered in 2016, orbits the red dwarf star Proxima Centauri and is the closest known exoplanet to our solar system. Scientists believe it lies within its star's habitable zone, the region where conditions could permit the existence of liquid water - a prerequisite for life as it is currently understood.

The prospect of exploring Proxima b directly has long been viewed as technically unfeasible due to the immense distances involved. However, a theoretical mission design outlined by aerospace engineer Amelie Lutz at Virginia Tech suggests a 500kg spacecraft, propelled by a compact nuclear fusion engine, could reach the planet and enter orbit in approximately 57 years.

In her master's thesis, discussed on the Universe Today website, Ms Lutz wrote: "Recent significant developments in power production using nuclear fusion allow for a realistic discussion of fusion propulsion systems for spacecraft. This study provides a framework for large-scale spacecraft missions to Proxima b."

Unlike lightweight interstellar concepts such as Breakthrough Starshot, which proposes sending gram-scale probes propelled by ground-based lasers, Lutz's study focused on a full-scale scientific spacecraft carrying a robust suite of instruments designed for orbital operations and detailed observation.

The probe would be equipped with 11 instruments, including imaging spectrometers, magnetometers, and subsurface sounding tools capable of analysing Proxima b's atmosphere, surface composition, and internal structure. The spacecraft's power and propulsion would be provided by a nuclear fusion reactor operating on deuterium-helium-3 (D-He3) fuel - a combination known for its high energy efficiency and relatively low neutron radiation.

Lutz compared three fusion propulsion designs: the Fusion-Driven Rocket (FDR), the Inertial Electrostatic Confinement (IEC) system, and the Antimatter Initiated Microfusion (AIM) engine. Each was analysed against four fuel types: deuterium-deuterium (D-D), deuterium-tritium (D-T), proton-boron-11 (p-B11), and deuterium-helium-3 (D-He3). The combination of an FDR using D-He3 fuel proved the most viable.

She concluded: "The analysis indicated a slow flyby and bounded orbit are most ideal for data collection. These can only be supported by the FDR employing D-He3 with a mission time of 57 years."

The mission would rely on using gravitational lensing to transmit data back to Earth. By placing the spacecraft on the far side of Proxima Centauri and aligning it precisely with Earth, signals could be boosted via the gravitational field of the star itself, potentially allowing high-bandwidth communications over interstellar distances.

Although helium-3 is scarce on Earth, it has been identified in greater quantities in lunar regolith. Some space agencies and private firms have previously proposed the Moon as a future source of helium-3 for terrestrial fusion power generation. However, the feasibility of large-scale extraction remains uncertain.

The propulsion system described in Lutz's work remains theoretical. Fusion propulsion has yet to be demonstrated in space, and D-He3 fusion has not been achieved under operational conditions. Even so, the analysis offers a structured model for developing long-range interstellar missions based on current trends in fusion research.

Proxima Centauri b is approximately 1.3 times the mass of Earth and completes an orbit of its parent star every 11.2 Earth days. It receives about 65% of the sunlight Earth does. However, red dwarf stars are known for strong stellar flares, which could strip away a planet's atmosphere or expose its surface to high levels of radiation. Whether Proxima b has retained a magnetic field or protective atmosphere is unknown.

Despite these uncertainties, Proxima b remains one of the most compelling targets in the search for life beyond the solar system. It appears on virtually all shortlists of potentially habitable exoplanets compiled by astrophysicists and planetary scientists.

Other candidates include LHS 1140 b, a rocky planet about 1.7 times the size of Earth located 40 light years away; TRAPPIST-1e, one of seven Earth-sized planets in the TRAPPIST-1 system; TOI-700 d, located 101 light years away in the constellation Dorado; and Kepler-442b, which orbits a relatively stable K-type star 1,200 light years from Earth.

Each of these planets meets basic criteria for potential habitability: a roughly Earth-sized mass, an orbit within the host star's habitable zone, and preliminary evidence suggesting the possible presence of an atmosphere. However, their distances make them much harder to reach, strengthening the case for Proxima b as the most accessible candidate for direct scientific investigation.

While there are currently no confirmed NASA plans for a mission to Proxima b, the agency has funded a number of advanced propulsion studies under its NASA Innovative Advanced Concepts (NIAC) programme. The study by Ms Lutz represents one of the most detailed mission concepts yet published targeting a fully orbital interstellar mission.

She concluded: "Future work includes the investigation into the requirements for communication of data back to Earth and the implementation of an autonomous decision-making architecture that guides the spacecraft at extreme distances."

If launched within the next few decades, such a mission could return data from Proxima b before the end of the 21st century.