The basic technology powering our ships is a functional variation of Bussard’s Ramjet. To review, the Ramjet used powerful magnets to generate a funnel shaped magnetic field. This funnel directed ionized interstellar hydrogen to the engine, which was powered by fusion. The concept is attractive because fuel can be gathered as the ship is moving, eliminating the weight generated by storing fuel for the entire trip. It is even more attractive because of a simple principle: the faster the ship travels, the more fuel it gathers; and the more fuel it gathers, the faster it can go. However, the Ramjet has a few problems.

• The strength of magnetic fields decreases exponentially with the distance from the device generating the field. Bussard envisioned a field kilometers wide. The power required to generate such a field is far more than any ship is a capable of generating at present.
• Fusion drives are still a work in process.
• A study done by Zubrin and Andrews, which founded the idea of Magnetic Sails, showed that the amount of turbulence generated with the idea would completely negate forward thrust. It actually was envisioned as a brake after that point!

The GJ667 Lines Company’s variation of the ramjet is called an IonJet. Development is still in progress. If the technology pans out, further details will be provided.

Braking

Stopping the ship becomes an interesting problem when operating at significant fractions of the speed of light. Without the turbulence noted by Zubrin/Andrews the ship would have to be flipped, or funnel inverted, in order to slow the ship down. However, interstellar trips are already too long. It makes more sense to rely on older approaches, such as a high inertia chemical burn using a fuel that can be manufactured in space from water (oxygen) and an ore (phosphorus, sulfur, magnesium, aluminum, etc.). This has the added side benefit of making the flipping of the ship, or inversion of the funnel, a secondary method of braking. Blazing past the last reaches of humanity into noone’s land would be every interstellar traveler’s nightmare!