By Daniel Neville, Thereza Zephir, and Eleanor Trese
JAN 31, 2020
Space is full of objects and processes that can cause catastrophic events. Luckily these dangers such as asteroids or supernovae can be predicted thousands or millions of years before they reach Earth. Unfortunately, there is little we can do to stop these catastrophes from affecting Earth. To avoid these events, we would have to move the entire solar system out of danger’s way. To solve this problem, Dr. Matt Caplan from Illinois State University has envisioned a device called the stellar engine, a “megastructure used to control the motion of a star system.”
To build this structure, humanity would first have to construct another megastructure called a “Dyson Sphere”. According to Earth Sky, Freeman Dyson, the man who imagined the Dyson Sphere, described it as “… a loose collection or swarm of objects traveling on independent orbits around the star” that is able to harness the power of the sun to meet humanity’s energy needs. This Dyson sphere would power the equipment required to transport the supplies and construct the stellar engine.
The first type of stellar engine that Caplan described in his report would be a Shkadov (“passive”) thruster, a thin parabola-like structure that would reflect the sun’s photons in a certain direction. Since photons carry momentum, the photons would move the sail-like structure and therefore the solar system because gravity would create a sort of tether between the sun and the “engine.” Although photons carry a very small amount of momentum, given the fact that the sun releases about ten quattuordecillion (that’s forty five zeroes) photons per second the momentum would be significant enough to cause a change in the solar system’s position. In this design the thruster is repelled by the radiation pressure from the sun, keeping it from falling onto the sun’s surface. Since the mirror could be very susceptible to damage from impacts with objects in space, Caplan suggests a “… ‘swarm’ consisting of many mirrors.” In his email, Caplan also told the Raider Review that the best material to construct the structure would be aluminum and according to his report, the aluminum would only have to be about 0.55 micrometers thick, thinner than a human hair. The thruster would be positioned at the sun’s poles to prevent the sun’s energy from being reflected at the planets. To keep the mirrors at this orientation, the structure would utilize gravity gradient stabilizers. Caplan described these as “… basically long antenna that would point away from the star. The passive thruster might look like a hedgehog, a smooth foil with tiny little hairs sticking out.” This engine would be able to move the solar system along at about a hundred light years every two hundred thirty million years (Kurzgesagt). However, the sun could only be moved in one direction and it would not be able to outrun a supernova blast, severely limiting the practical uses of this type of solar engine.
The second type of stellar engine is an “active thruster” called the “Caplan Thruster.” This device would use extremely powerful electromagnets to collect the hydrogen and helium produced by the sun and it’s solar wind to fuel a nuclear fusion reaction. This reaction would create a beam of energy and push the engine and the sun in a given direction. Since the engine needs to capture a large amount of fuel, the Dyson Sphere that was previously mentioned would reflect energy back to the sun subjecting “… small regions to extreme temperatures, lifting billions of tons of mass off the surface of the sun.” (Kurzgesagt) To help stabilize the engine and prevent it from smashing into the sun, a second beam of hydrogen that was unused in the fusion process would be fired from a particle accelerator back to the sun. This type of stellar engine would be able to reach speeds of about fifty light years every one million years, fast enough to outrun the blast of a supernova that could have the potential to completely destroy Earth (Kurzgesagt). Another benefit of using an active thruster of this design is that the engine could be oriented anywhere around the sun without damaging the rest of the solar system, giving humanity the ability to move the sun in any direction. This would allow us to move our solar system closer to other solar systems, making colonization of other planets much easier.
When asked about the obstacles of building superstructures such as the Dyson Sphere or stellar engine, Caplan responded, “The biggest obstacle is everything. Energy needs, material, practical engineering, cooperation on a literal astronomical scale. It’s possible from physics, but the barriers to building one might be insurmountable.” We will not likely to see this system constructed within our lifetimes. Perhaps the world, during the next thousand years, will be able to overcome these enormous physical and scientific challenges to create humanity’s most ambitious project in history.