The Halo drive (or Kipping Loop) is a Class-B singularity propulsion drive that exploits the extreme gravity of black holes to accelerate spacecraft without using onboard fuel. The fuel is the momentum of the black hole itself.
Originally proposed by David Kipping, the Halo drive allows a civilization to steal kinetic energy from a black hole using a beam of light.
The drive relies on the concept of boomerang photons.
- A ship fires a powerful laser beam toward a black hole (specifically one moving toward the ship).
- The ship aims the laser at a precise angle just outside the event horizon (the photon sphere). The black hole's gravity bends the light 180 degrees, flinging it back at the ship.
- As the light whips around the moving black hole, it steals some of the black hole's momentum. The light returns to the ship with more energy (blue-shifted) than when it left.
- The returning laser strikes a reflective sail on the ship. This double-impact (firing + reflection) transfers the stolen energy into pure thrust.
The Highway Halo (Natural)[]
Type 2 civilizations lack the technology to build black holes, so they use natural ones.
- They map out binary black hole systems across the galaxy. Ships travel from one binary to the next, using the Halo drive to bounce off the black holes like pinballs.
- When a civilization over-uses a binary system for Halo jumps, they drain its orbital energy. This causes the two black holes to spiral inward faster. Glitched binaries that are merging too quickly are a sure sign of a Halo Highway.
The Kerr-Drive (Artificial)[]
Advanced Type 3 vessels (like those equipped with a Kerr-Drive Knot) carry a microscopic black hole inside the engine room.
- The ship fires lasers into its own internal black hole.
- By trapping the light in a "Halo" around the internal singularity, the ship can store petawatts of energy in the light beam, releasing it only when thrust is needed. This effectively turns the black hole into a light battery.