Jolting Into Space
The U.S. Department of Energy (DOE) is typically not in the business of developing propulsion systems for NASA, but it is continually working on better superconducting magnets and very rapid, high-power solid-state switches. In the mid-1990s, Goodwin chaired a session for NASA's Breakthrough Propulsion Physics Project, which is working to design propulsion systems that have no propellant, use a very high energy system and can eventually overcome inertia.
"It seemed that there should be some way to use this technology that [DOE scientists] were developing to help NASA meet their goals, and it basically sprang from that," Goodwin said. What sprang from the DOE research was Goodwin's idea for a space propulsion system that uses super-cooled, superconducting magnets vibrating 400,000 times per second. If this rapid pulse can be directed in one direction, it could create a very efficient space propulsion system with the ability to achieve speeds on the order of a fraction of 1 percent of the speed of light.
During the first 100 nanoseconds (billionths of a second) of an electromagnet ramping up, the electromagnet is in a non-steady state that allows it to pulse very rapidly. After it ramps up, the magnetic field reaches a steady state and no pulsing occurs. Goodwin describes the electromagnet he is using as a solenoid, which is basically a superconducting magnetic wire wrapped around a metal cylinder. The entire structure will have a diameter of 1 foot (30.5 cm), a height of 3 feet (91.4 cm) and a weight of 55.12 pounds (25 kg). The wire used for this propulsion system is a niobium-tin alloy. Several of these wire strands will be wrapped into a cable. This electromagnet is then super-cooled with liquid helium to 4 degrees Kelvin (-452.47 F / -269.15 C).
For the magnet to vibrate, you need to cause an asymmetry in the magnetic field. Goodwin plans to deliberately introduce a metal plate into the magnetic field to enhance the vibrating movement. This plate would be made of either copper, aluminum or iron. The aluminum and copper plates are better conductors and have a greater effect on the magnetic field. The plate would be charged up and isolated from the system to create the asymmetry. Then the plate would be drained of electricity in the few microseconds (millionths of a second) before the magnet were allowed to oscillate in the opposite direction.
"Now, the catch here is, can we use this non-steady state condition in such a way that it only moves in one direction?" Goodwin said. "And that's where it's very uncertain that that can be done. That's why we would like to do an experiment to find out." Together with the cooperation of Boeing, Goodwin is seeking funding from NASA to perform such an experiment.
The key to the system is the solid-state switch that would mediate the electricity being sent from the power supply to the electromagnet. This switch basically turns the electromagnet on and off 400,000 times per second. A solid-state switch looks something like an oversized computer chip -- imagine a microprocessor about the size of a hockey puck. Its job is to take the steady-state power and convert it to a very rapid, high-power pulse 400,000 times per second at 30 amps and 9,000 volts.
In the next section, you'll learn where the system draws its power from and how it may send future spacecraft beyond our solar system.