The Mechanics Behind Electromagnetic Propulsion

For years, space exploration has relied solely on rocket engines powered by chemical fuels. However, as we step into the 21st century, aerospace experts are exploring groundbreaking methods to reach the stars, such as light propulsion, nuclear-fusion propulsion, and antimatter propulsion. Among these innovations is a propellant-free spacecraft concept, driven by electromagnets, which promises to take us further into space than ever before.

At extremely low temperatures, electromagnets exhibit a unique phenomenon: they vibrate momentarily when electrified. David Goodwin, a program director at the U.S. Department of Energy's Office of High Energy and Nuclear Physics, suggests that harnessing this vibration in a single direction could generate enough thrust to propel spacecraft faster and farther than any existing propulsion technology.

Goodwin shared his groundbreaking concept at the Joint Propulsion Conference on July 8, 2001, in Salt Lake City, Utah. In this feature of How Stuff Will Work, discover the inner workings of Goodwin's electromagnetic propulsion system and its potential to revolutionize deep-space exploration.

Jolting Into Space

While the U.S. Department of Energy (DOE) isn't typically involved in crafting propulsion systems for NASA, it focuses on advancing superconducting magnets and high-speed, high-power solid-state switches. In the 1990s, Goodwin led a session for NASA's Breakthrough Propulsion Physics Project, which aims to design propulsion systems that eliminate the need for propellant, utilize high-energy systems, and ultimately defy inertia.

"It seemed logical to leverage the technology developed by DOE scientists to assist NASA in achieving its objectives, and that's where the idea originated," Goodwin explained. This led to his concept of a space propulsion system employing super-cooled, superconducting magnets vibrating at 400,000 times per second. If this rapid pulsing can be channeled in one direction, it could result in a highly efficient propulsion system capable of reaching speeds approaching a fraction of 1 percent of the speed of light.

In the initial 100 nanoseconds (billionths of a second) as an electromagnet powers up, it enters a non-steady state, enabling rapid pulsing. Once fully powered, the magnetic field stabilizes, and pulsing ceases. Goodwin's design involves a solenoid, which consists of superconducting magnetic wire coiled around a metal cylinder. The entire structure measures 1 foot (30.5 cm) in diameter, 3 feet (91.4 cm) in height, and weighs 55.12 pounds (25 kg). The wire used is a niobium-tin alloy, with multiple strands woven into a cable. The electromagnet is then cooled to 4 degrees Kelvin (-452.47 F / -269.15 C) using liquid helium.

To induce vibration in the magnet, an imbalance in the magnetic field must be created. Goodwin intends to strategically place a metal plate within the magnetic field to amplify the vibrations. This plate could be crafted from copper, aluminum, or iron. Aluminum and copper plates, being superior conductors, exert a stronger influence on the magnetic field. The plate would be charged and isolated to establish the asymmetry, then discharged in microseconds (millionths of a second) before the magnet oscillates in the opposite direction.

"The challenge lies in harnessing this non-steady state condition to ensure movement in only one direction," Goodwin explained. "It's highly uncertain whether this is achievable, which is why we aim to conduct an experiment to determine its feasibility." With support from Boeing, Goodwin is pursuing NASA funding to carry out this experiment.

Central to the system is the solid-state switch, which regulates the flow of electricity from the power supply to the electromagnet. This switch rapidly activates and deactivates the electromagnet 400,000 times per second. Resembling an oversized computer chip, the solid-state switch is akin to a microprocessor the size of a hockey puck. Its role is to transform steady-state power into rapid, high-power pulses operating at 30 amps and 9,000 volts.

In the following section, discover the power source for this system and how it could propel spacecraft beyond the boundaries of our solar system.

Beyond Our Solar System

The U.S. Department of Energy is also developing a nuclear space reactor for NASA, which Goodwin suggests could serve as the energy source for the electromagnetic-propulsion system. The DOE is seeking NASA funding, with a 300-kilowatt reactor potentially operational by 2006. This system would transform the reactor's thermal energy into electrical power to drive the propulsion mechanism.

"For missions to deep space, such as Mars and beyond, nuclear power is essential if you intend to transport any significant mass," Goodwin stated.

The reactor will produce energy via induced nuclear fission, a process that splits atoms like uranium-235, releasing immense heat and gamma radiation. A single pound (0.45 kg) of highly enriched uranium, similar to that used in nuclear submarines or aircraft carriers, contains energy equivalent to about 1 million gallons (3.8 million liters) of gasoline. Compact and efficient, a baseball-sized amount of uranium could sustain a spacecraft for extended periods, enabling it to cover vast interstellar distances.

Thermal energy from a nuclear reactor could be converted into electricity to power the spacecraft.

"While reaching the nearest star remains unfeasible, missions to the heliopause are within reach," Goodwin explained. "If the system performs exceptionally well, it could achieve speeds approaching a fraction of 1 percent of the speed of light. Even so, traveling to the nearest star would still take hundreds of years, making it impractical."

The heliopause marks the boundary where the solar wind from the sun collides with the interstellar wind generated by other stars. Situated approximately 200 astronomical units (AU) from the sun (its precise location remains uncertain), one AU represents the average distance between the sun and Earth, roughly 93 million miles (150 million km). For context, Pluto lies 39.53 AU from the sun.

To transport humans, a significantly larger device would be necessary, but the compact 1-foot diameter, 3-foot-tall electromagnet could propel small, unmanned spacecraft, such as interstellar probes, across vast distances. Goodwin highlights the system's efficiency, emphasizing its ability to channel substantial power through a superconductor. The challenge lies in converting this power into propulsion without damaging the magnet, as rapid vibrations could push it to its structural limits.

Critics argue that Goodwin's system will merely cause the magnet to vibrate intensely without achieving movement. Goodwin acknowledges the lack of evidence supporting the system's success, stating, "It is highly speculative, and on my most optimistic days, I believe there's a one in ten chance it might work." However, a century ago, the idea of reaching space seemed equally improbable.