The American physicist who directed the U.S. fusion program during its golden age in the 1970s and co-invented the fusor — later becoming a prominent critic of fusion timeline optimism.
ReviewedLast reviewed: 9 Aug 2026·Category: Scientists & Pioneers
Career
Robert L. Hirsch (born 1935) earned his Ph.D. in nuclear engineering from the University of Illinois. He co-invented the Farnsworth–Hirsch fusor with Philo Farnsworth in the 1960s at ITT — an inertial electrostatic confinement device that remains widely used for neutron production and education.[1]
Leading the U.S. Fusion Program
The Hirsch era (1972–1976): As director of the AEC/ERDA Division of Controlled Thermonuclear Research, Hirsch oversaw the largest expansion of U.S. fusion funding. He championed the construction of TFTR, the PLT tokamak, and doubled the fusion budget. His strategy focused on building ever-larger experiments to reach reactor conditions.
Hirsch later held senior positions at ARCO, EPRI, and served as a consultant on energy policy. He became known for arguing that the fusion community consistently underestimates the time and cost required for commercial fusion.[2]
The Fusor
The Farnsworth–Hirsch fusor uses electrostatic fields to accelerate and confine ions. While not viable for energy production (the energy input far exceeds fusion output), fusors are the simplest devices capable of producing fusion reactions and are built by hobbyists, universities, and companies for neutron generation.[3]
Sources
Hirsch, R.L. "Inertial-Electrostatic Confinement of Ionized Fusion Gases." Journal of Applied Physics, 38, 4522, 1967.
Hirsch, R.L. "Fusion research: Time to set a new path." Issues in Science and Technology, Summer 2015.
Dean, S.O. "The United States Magnetic Fusion Energy Program." Journal of Fusion Energy, 17, 289, 1998.