One of the problems facing interstellar travel is the lack of gas stations in space. To get around that, the Bussard interstellar ramjet—a structure that uses hydrogen atoms to initiate nuclear fusion—collects its hydrogen fuel from the interstellar medium. Proposed in 1960 by physicist Robert Bussard, the ramjet called for a 4,000-mile-wide magnetic funnel to collect hydrogen. According to Bussard, the ramjet could approach the speed of light.

Attempting to update the Bussard ramjet, aerospace engineers Robert Zubrin, the current president of Pioneer Astronautics, and Dana Andrews, now the chief technology officer of Andrews Space, made a seredipitous discovery in 1988. The magnetic funnel would create too much drag, making propulsion inefficient, but those same magnetic fields would make a great sail. “We started exploring the magnetic field first as a drag device for deceleration and then as a sail,” Zubrin says. The magnetic sail would harness the force of the solar wind. But, he says, today we lack the technology, such as high-temperature superconductors, to build a good magnetic sail.