U-M Leads $35M Space Propulsion Project with Nuclear Microreactor

The U.S. Space Force is investing $35 million in a groundbreaking project led by the University of Michigan. The initiative focuses on developing spacecraft that can “maneuver without regret” by combining fast chemical rockets and efficient electric propulsion using a nuclear microreactor. This effort, known as the Space Power and Propulsion for Agility, Responsiveness and Resilience Institute, involves eight universities and 14 industry partners, marking one of the largest national endeavors in space propulsion and power, crucial for defense and exploration.

Current spacecraft propulsion relies on either chemical rockets, which are powerful but fuel-heavy, or slower, fuel-efficient electric propulsion powered by solar panels. Chemical rockets pose a high risk of regret due to limited fuel but are necessary for rapid maneuvers. Electric propulsion, like a 100-kilowatt Hall thruster from U-M, could be faster if sufficient power is available. The key challenge is finding power sources for such thrusters.

A team is developing a nuclear microreactor to power faster electric propulsion, exploring a new avenue for safe, sustainable space power. Other subteams will convert microreactor heat into electricity and design electric engines to use this energy for thrust. The propulsion system will include a chemical rocket for agility. While chemical rockets require fuel to burn, electric propulsion accelerates propellant, turning atoms into ions for high-speed thrust.

The project aims to simplify refueling by demonstrating dual-purpose fuels for chemical and electric propulsion. “The Space Force is tasked with securing America’s interests in, from and to space,” stated Joshua Carlson, the Space Force program manager. The collaboration combines academic and business partners to advance commercial manufacturing. Ultra Safe Nuclear Corp. will design a lightweight microreactor, and U-M engineers will simulate its output to test system components.

Two teams will transform thermal energy into electricity. U-M and Spark Thermionics will explore thermionic emission cells, utilizing the reactor’s heat and space’s cold to generate electrical current. Another U-M team will partner with Antora Energy for thermal photovoltaics, similar to solar cells that convert heat into electricity. Cornell University, Advanced Cooling Technologies, and Ultramet will design panels to radiate waste heat, as the reactor’s energy exceeds what conversion methods can handle.

Subteams are examining different electric propulsion types: Hall thruster, applied-field magnetoplasmadynamic thruster, and electron cyclotron resonance thruster. All thrusters need a module turning propellant into gas, developed by Western Michigan University and Champaign Urbana Aerospace. A cathode from Colorado State University will neutralize the propellant to prevent electric charge build-up. A new chemical rocket concept will be developed by U-M and Pennsylvania State University, with Benchmark Space Systems providing a commercial system for testing.

U-M, Cornell, Colorado State, and the University of Colorado are contributing computer modeling and experimental diagnostics. Analytical Mechanics Associates will evaluate the entire system. “We are very grateful to the U.S. Space Force and Air Force Research Laboratory for this opportunity. We’re excited to get started on this work with this exceptional national team,” Jorns said.

Eric Viges at U-M’s Space Physics Research Laboratory will serve as a chief engineer. U-M subteam leads include:

• Andrej Lenert, associate professor of chemical engineering.
• Stephen Forrest, Peter A. Franken Distinguished University Professor of Engineering, Paul G. Goebel Professor of Engineering, professor of electrical engineering and computer science, and of material science and engineering.
• Mark Kushner, William P. Allis Distinguished University Professor of Electrical Engineering and Computer Science, George I. Haddad Collegiate Professor of Electrical Engineering and Computer Science, professor of electrical engineering and computer science, of nuclear engineering and radiological sciences, and of chemical engineering.
• John Foster, professor of nuclear engineering and radiological sciences, and of aerospace engineering.
• Solomon Adera, assistant professor of mechanical engineering.
• Mirko Gamba, associate professor of aerospace engineering.
• Venkat Raman, professor of aerospace engineering, and of mechanical engineering.
• Christopher Limbach, assistant professor of aerospace engineering.
• Alex Gorodetsky, associate professor of aerospace engineering.
• Oliver Jia-Richards, assistant professor of aerospace engineering, and of climate and space sciences and engineering.

Al-Thaddeus Avestruz (electrical and computer engineering) will participate as a consultant.

Leads from other universities include: Sadaf Sobhani, Fabien Royer and Elaine Petro (Cornell); Jinia Roy (Wisconsin); Kristina Lemmer (Western Michigan); John Williams and Azer Yalin (Colorado State); Richard Yetter (Penn State); Edgar Choueiri (Princeton); Justin Little (Washington); and Iain Boyd (Colorado).

Northrop Grumman, Lockheed Martin, Westinghouse, and Aerospace Corp. form the advisory board.