Public interest and recent accomplishments in civil and scientific spaceflight are running at historically high levels. The United States lands rovers on Mars and flies ‘helicopters’ through its tenuous atmosphere. SpaceX and NASA have partnered for three successful human spaceflight launches from U.S. soil to the International Space Station within the past year, the Space Launch System will soon send the Orion spacecraft to lunar orbit, and James Webb Space Telescope is nearly ready for launch. On balance, there is much reason for optimism in the U.S. space community, and recently appointed NASA Administrator Bill Nelson and his deputy, Col. Pam Melroy, bring deep policy and spaceflight experience to the job of leading the world’s preeminent space agency at a time of great momentum and success.
Any NASA administration has a responsibility to execute successfully and safely the programs underway. But equally important is the imperative to make the right kinds of investment decisions for the future, so that momentum is maintained and additional transformational accomplishments can be realized. Many of the successes we see today are a direct result of investment decisions made years ago, such as the 2005 investment by NASA of $500 million for initial development to support commercial spaceflight to sustain the ISS.
Today, we have a unique opportunity to make the entire solar system — including the strategically vital region of space surrounding the Earth and the moon — more accessible, through investments in advanced propulsion systems that will allow us to move more material, shorten transit times, arrive ‘on-station’ with substantial power, and open windows for flight trajectories that are less dependent on the fortuitous alignment of planets and minimum-energy flight paths. Nuclear thermal propulsion (NTP) is the most promising technology to accomplish these goals.
Chemical rockets combust a fuel and oxidizer to generate a hot gas at high pressure that is then vented through a nozzle at very high speed to create thrust. Instead of combustion, NTP uses the energy produced in fission-decay of uranium to heat a fluid — typically liquid hydrogen — which is then similarly vented for propulsion, as well as used to cool the reactor. Launched to space on a rocket as a powered-off and inert “payload,” an NTP in-space propulsion system is only activated once safely in space, where it can then send spacecraft onward to their final destinations.
Using NTP, current travel times to Mars of nearly seven months can be reduced by half or more. Substantially more material can be sent to more distant locations, and we can develop the ability to navigate and travel through our own Earth-moon region of space with greater flexibility, autonomy, and capability. NTP may sound futuristic, but NASA actually performed a substantial amount of research and development during the 1960s and 1970s, even hot-firing a number of engines.
Today, students, scientists, and engineers are reprising this work, across NASA, the Department of Defense, Department of Energy, private sector companies, and in U.S. research universities. In the development of NTP today, we have the advantages of new materials, additive manufacturing techniques, high-performance engineering simulation and modeling software, and other technology tools that were not available to those researching NTP during the time of Apollo.
The United States has been demonstrating the advantages of safe, reliable nuclear propulsion systems here on Earth for almost 70 years. Nuclear-power enables U.S. Navy ships to maximize their time at sea, to navigate freely, and to operate with maximum capacity for independent action. The long-range, high-power capabilities of these systems — among the safest modes of transportation ever devised — minimize the amount of downtime needed to refuel, replenish, or be stationed in port, and maximize the efficacy of the ship and implementation of its missions. Similarly, NTP will enable the U.S. to ‘sail’ the ocean of space with greater efficiency, capability, and autonomy, thereby exercising and helping secure our leadership position in civil and national security spaceflight activities.
The Defense Advanced Research Projects Agency (DARPA), understanding the game-changing potential of this technology, recently awarded contracts for the DRACO program, enabling work toward demonstrating such a system for operation on orbit in the Earth-moon space environment.
A similar commitment from within U.S. civil space leadership will further leverage the existing alignments of executive branch policy, multiple congressional authorizations and appropriations, technical maturation, and renewed interest, at precisely the time when these technology investments must be made to secure the needed foundations for future progress in space. Administrator Nelson and NASA leadership should take advantage of this momentum, to fully support, and to implement the rapid development of an in-space NTP demonstration mission as one of their highest priorities for the future.
John M. Horack is the inaugural holder of the Neil Armstrong Chair in Aerospace Policy at The Ohio State University, with appointments in the College of Engineering, where he also serves as the Senior Associate Dean, and in the John H. Glenn College of Public Affairs. Through more than three decades of work in the space industry, he has held senior executive, scientific research, and teaching positions within NASA, in academia, and in the private sector.
This article originally appeared in the May 2021 issue of SpaceNews magazine.
