Physicists Propose a New Way to Reach Alpha Centauri in a Single Generation
A team of scientists has proposed a new method of space travel that could make journeys to other star systems possible within a single human lifetime. The core of their idea involves beams of electrons accelerated to nearly the speed of light.
Jeff Greason, CTO of Electric Sky and chairman of the Tau Zero Foundation, explains that the main challenge in reaching other stars is the vast distances involved. The nearest star system, Alpha Centauri, is 4.3 light-years away—about 2,000 times farther than Voyager 1, the most distant human-made object, has traveled.
The research, conducted by Greason and physicist Gerrit Bruhaug from Los Alamos National Laboratory, was published in the journal Acta Astronautica. According to the scientists, modern chemical rockets—even with extra acceleration from planetary or solar flybys—cannot reach the speeds needed for interstellar travel.
The Challenge of Delivering Energy to a Spacecraft
The main problem is how to deliver enough energy to a spacecraft in an efficient and practical way. There simply isn’t enough room onboard for the fuel or batteries required for such acceleration. Additionally, scientific organizations are generally unwilling to fund missions lasting more than 30 years, as the wait for results would be too long.
Previously, physicists mostly considered using laser beams made of photons for such long-distance missions. The most promising ideas included laser-powered interstellar ramjets and laser sails. Ramjets would compress hydrogen from interstellar space, powered by a laser beam from Earth, while laser sails would use the momentum of photons to push the spacecraft forward.
However, both concepts have serious drawbacks. Ramjets are hindered by the extremely low density of interstellar matter and the enormous energy required for nuclear fusion. Laser sails are simpler in design, but it’s difficult to maintain beam accuracy and intensity over such vast distances.
The Advantages of Electron Beams
Electrons are much easier to accelerate to near-light speeds and have unique advantages. The main issue is that electrons have a negative charge and repel each other, causing the beam to disperse. Greason and Bruhaug, however, found a way to prevent this.
At relativistic speeds—close to the speed of light—time slows down, so the electron beam doesn’t have time to disperse and remains focused. Space isn’t empty; it contains a very thin, ionized gas plasma. As the electron beam passes through this plasma, it pushes away the light electrons, leaving the heavier ions behind.
This process creates a magnetic field that pulls the beam together, preventing it from spreading out. This effect is called a “relativistic pinch.” According to the scientists’ calculations, such a beam could deliver enough energy to accelerate a 1,000 kg probe (about the mass of Voyager 1) to 10% the speed of light. This would allow it to reach Alpha Centauri in 40 years instead of the current 70,000.
Greason notes that such compressed relativistic beams already exist in space, for example, in the jets of charged particles emitted by black holes. However, many questions remain: Can we artificially create these conditions? Would the Sun’s magnetic field disrupt the beam? How would we launch it?
How the System Would Work
The scientists propose placing a beam-generating spacecraft near the Sun, where intense sunlight would provide the necessary energy. But delivering energy is only half the challenge. The spacecraft must also convert that energy into thrust by expelling some kind of propellant. The process must generate minimal heat, or the spacecraft could melt.
Greason admits that the team has some ideas for converting the beam’s energy into thrust, but these remain purely theoretical and need further development.
Next Steps and Potential Applications
To test the theory, computer simulations and space experiments are needed. For example, a satellite could direct a beam at the Moon to verify the calculations. Compared to laser sails, electron beams could work over distances 10,000 times greater and accelerate much heavier spacecraft. This is important because laser systems are currently considered only for probes weighing a few grams, which would struggle to send data back to Earth.
The researchers emphasize that the cost of creating a powerful beam depends directly on the required power. Therefore, the relativistic electron beam approach could be much more affordable than alternatives. Heavier probes weighing tens of kilograms would have enough room for power sources, scientific instruments, and communication systems needed to exchange information.
The technology for long-distance energy transmission could be useful not only for interstellar travel but also within our Solar System—for example, to transmit energy from the Sun to other objects like the Moon.