Relativistic electron beam could propel spacecraft to Alpha Centauri, study suggests

Getting a spaceship to another star is a tremendous challenge. But that doesn’t stop people from working on it. The most prominent groups currently doing so are Breakthrough Starshot and Tau Zero Foundation, both of which focus on very specific types of propulsion beam power.

A paper by Jeffrey Griesen, chairman of the Tau Zero board, and Gerrit Bluhaug, a physicist at Los Alamos National Laboratory who specializes in laser physics, describes one such beam technique: relativistic electron beams. It looks at the physics of this and how it’s done. It could be used to push a spaceship to another star.

The study is published in the journal “Acta Astronautica”.

There are many considerations when designing this type of mission. One of the biggest things (literally) is the weight of the spacecraft. Breakthrough Starshot focuses on a small design with giant solar “wings” that would allow beams of light to reach Alpha Centauri. But for practical purposes, the arrival of such a small probe would likely gather little or no real information. This is more of an engineering feat than an actual scientific mission.

On the other hand, this paper considers spacecraft sizes up to about 1,000 kg. This is roughly the size of the Voyager spacecraft, which was built in the 1970s. Obviously, more advanced technology will allow for the installation of far more sensors and controls than are available on these systems. However, pushing such a large probe with a beam requires other design considerations. In other words, what type of beam is it?

Breakthrough Starshot plans to push a laser beam, possibly in the visible spectrum, directly onto a light sail attached to the spacecraft. However, given the current state of optical technology, this beam can only effectively advance the spacecraft about 0.1 AU of its journey, for a total of more than 277,000 AU to Alpha Centauri. It will be. That small amount of time could be enough to get the probe to significant interstellar speeds, but only if it’s small and out of the laser beam.

The laser only needs to be turned on for a short time, at most, to accelerate the spacecraft to cruising speed. However, the paper’s authors take a different approach. Instead of supplying power for only a short period of time, why not try supplying power for a long period of time? This allows for more power to be stored, allowing the sturdier spacecraft to travel at a significant fraction of the speed of light.

This type of design also presents many challenges. The first is beam spread. How do such beams remain coherent enough to provide meaningful power at distances more than 10 times the distance from the Sun to the Earth?Most of the papers focus on relativistic electron We discuss this in detail, focusing on beams. This mission concept, known as Sunbeam, uses just such a beam.

There are several advantages to harnessing these fast-moving electrons. First, accelerating electrons to around the speed of light is relatively easy, at least compared to other particles. However, since they all share the same negative charge, they will likely repel each other, reducing the effective propulsion of the beam.

At relativistic speeds, this is less of a problem due to a phenomenon discovered in particle accelerators known as relativistic pinch. Essentially, due to the time lag moving at relativistic speeds, there is not enough relative time for the electrons to start pulling each other apart to any meaningful degree.

Calculations in the paper show that such a beam could deliver up to 100 or 1,000 AU of power, far beyond the point at which other known propulsion systems can make an impact. It also shows that at the end of the beam-powered period, a 1,000 kg spacecraft could travel at 10% the speed of light, reaching Alpha Centauri in just over 40 years.

However, there are many challenges that must be overcome to achieve this. One is how to form this much power into a beam in the first place. The farther the probe is from the beam source, the more power is required to transfer the same force. Estimates range up to 19 gigaelectronvolts for a 100 AU spacecraft. This is a very high-energy beam, and well within the understanding of our technology, since the Large Hadron Collider can form beams with energies that are orders of magnitude higher.

The authors propose using a tool that doesn’t yet exist, but is at least theoretically possible, to capture that energy in space: solarstatite. The platform uses a combination of force from the extrusion of light from stars and a magnetic field that uses magnetic particles emitted by the Sun to keep it from falling into the Sun’s gravitational well. Masu. That would be as close as the Parker Solar Probe’s closest approach to the Sun. That means, at least in theory, it’s possible to create materials that can withstand that heat.

The beam forming itself takes place behind a huge sunshade, allowing it to operate in a relatively cool and stable environment, and also keeping the station safe for the days to weeks required to push the 1,000 kg spacecraft that far. You can stay in. I’ll go. This is why we use statites rather than orbitals. Statite remains stationary relative to the spacecraft and does not have to worry about being blocked by the Earth or the Sun.

Everything so far is still in the realm of science fiction. That’s why the authors first met on the ToughSF Discord server, a gathering place for science fiction enthusiasts. But it does show that, at least in theory, it is possible to launch a scientifically useful Alpha Centauri spacecraft within a human lifetime, with minimal advances in existing technology.