Hyperdrive

Most modern interstellar space travel is achieved using variations on the tachyon transference drive (TTD), variously called the tachyon drive or hyperdrive. This circumvents the laws of mass and energy by “flipping” a vessel travelling at speeds approaching the speed of light into tachyonic particles. These particles have no mass in the convention sense, as they are incapable of interacting with sub-luminal matter. They also travel at the speed of light within their own point of reference, but their trajectory takes them on a loop initially backwards in time. During their transit, the subjective shipboard time is the same as if they had been travelling at the speed of light between two points. However, because of the backward loop, they in fact arrive in normal space at a point in time contiguous with their departure.

The tachyon “flip” is achieved by a tachyon field effect, a burst of energy which kicks all particles within the field to a higher energy state. To use a crude example, the tachyon burst is like dropping a huge stone into the water next to a moving boat. The boat is cast up onto the head of a wave, and rides along it until the wave dissipates and it is returned to normal sea level. In a TTD, the tachyon burst must be configured precisely with the distance of the jump required.

The tachyon drive has a number of issues which limit its range. Firstly, the amount of energy required to jump increases geometrically with the distance required, to the extent that long jumps become unfeasible. The closer the ship is travelling to the speed of light, the less energy is required to make the jump. Conversely of course, the slower the ship is travelling, the more is energy is required. In practice most ships accelerate to about 40% of C before jumping. Larger transit ships get around this problem by accelerating to upwards of 70% of C, but constantly travelling on a loop between star systems, using smaller vessels to load and unload passengers and cargo.

The second problem is particle dispersal. A beam of light, even tightly focused laser light, diverges over a long distance, and the same is true for tachyons projected by a TTD burst. Solid objects decohere over long distances, so that if a ship jumps too far, when it recoheres the molecular bonds will have broken, and all that reappears is a cloud of charged particles.

In practice tachyon drives are limited to a range of roughly seven light years. Though it is possible for ships to reappear in normal space then jump again, in practice this is dangerous because

One of the most crucial problems involved with early TTD development is that of transporting sentient creatures. When flipped into a tachyon cloud, the wave form essential to brain function is interrupted. When the ship returns to normal space, simple life forms and plants can resume their normal existence at the point they started. In more complex creatures it causes loss of memory and brain function at best, death at worst.

Various attempts were made to enable brain function to continue, or even to “reboot” brains by backing up neural wave state at the point of transition (storing it in solid-state memory). This had not only prohibitive technical problems, but also philosophical ones, since sentient beings felt that they suffered true brain death at the flip-point, and thereafter had their brains reinjected with a synthetic personality which was merely a copy of their own.

This problem was solved with a drastic modification to the tachyon burst technology. Rather than flipping matter into a cloud of tachyons incapable of interacting with any other particles, the particles could still cohere and interact with each other, but only with those particles in the original field.

This solved the problem of transporting living brains, but added the problem of time debt. Since living beings were now functional and potentially fully conscious during the journey, they were forced to experience the time dilation created by the tachyonic burrowing backward and then forward in time - potentially years on a multi-stellar journey. This was solved by resurrecting an ancient branch of technology: long term cold storage, or hypersleep.

It also required building ships and equipment which could endure for millennia, since a ship in regular service could accumulate centuries of time debt in a single round trip.