The drive chamber took up the rear quarter of the ship and fully two-fifths of its volume. Most of that was filled by the six huge plasma thrusters that channelled the engine’s output. Cocooned in space suits, Cait and Harris stood on the gantry running along the mid line of the rear wall. The vast superstructure surrounded them, and out past the thrusters lay the infinite. The starfield crowded into an ellipse, as if viewed through a thick lens. Cait knew at this speed the view was blue-shifted as well, but she couldn’t tell the difference. The combined effect made her feel like an ant clinging to a very small ledge.
Her eyes drifted back to the featureless, black heart of the drive. Their survival depended on balance — macro and quantum, thrust and inertia. The Black Box was the fulcrum, fed by the vacuum surrounding it. On one hand, it sucked hydrogen atoms into its nanotubes, cut them off from the quantum wavelengths that kept them spinning, and fed the energy released to the huge plasma thrusters. And on the other, it generated a quantum field that enhanced the push and decreased the inertia just enough so the harnesses could absorb the residual v-shift from the drive pulses.
Exactly 189 x 1030 bucky-tubes sat inside the box, cycling ten times that number of hydrogen atoms through every second. The processing power to keep it balanced was tremendous, and it all relied on the proper functioning of the neural network that made up the Phillips persona.
The process described derives energy from the vacuum of space. It's been theorised but is not considered possible at this stage. But this is science fiction, and we don't know what might be possible in the future.
For a discussion of zero point energy and bucky-tubes, have a look at the following sites:
Carbon nanotubes on Wikipedia
Zero Point Energy on Wikipedia
Nasa on a Zero Point Energy Star Drive
Zero Point Energy on the Space Exploration Day website
You can find out more information about Horizon on the Horizon Page.