Nuclear energy is an excellent source of energy for space. Solar panels struggle to gather enough energy to power a spacecraft or probe as you move away from the sun, and chemical rocket fuel tanks are simply too large. Nuclear reactors can generate heat, electricity, and/or propulsion in space. They could be used to power a Mars or Moonbase, or they could be configured as a nuclear-powered rocket to travel there.
Nuclear thermal propulsion, which uses the heat produced by nuclear reactions as fuel, could one day be used in human spaceflight, possibly even missions to Mars. Its development, on the other hand, poses a challenge. On a regular basis, the materials used must be able to withstand high heat and bombardment with high-energy particles.
Will Searight, a nuclear engineering doctoral student at Penn State, is helping to fund research that could make these advancements a reality. He published the results of a preliminary design simulation in Fusion Science and Technology, an American Nuclear Society publication.
Nuclear thermal propulsion, which uses heat from nuclear reactions as fuel, could be used one day in human spaceflight, possibly even for missions to Mars. The materials used must be able to withstand high heat and bombardment of high-energy particles on a regular basis.
Searight simulated a small-scale laboratory experiment known as a hydrogen test loop to better understand nuclear thermal propulsion. The setup simulates the operation of a nuclear reactor in space, where flowing hydrogen travels through the core and propels the rocket – at temperatures of nearly 2,200 degrees Fahrenheit. Searight created the simulation using dimensions from detailed drawings of tie tubes, which make up a large portion of the test loop through which hydrogen flows. The drawings were provided by industry partner Ultra Safe Nuclear Corporation (USNC).
“Understanding how USNC’s components behave in a hot hydrogen environment is critical to getting our rockets into space,” said Searight. “We’re thrilled to be collaborating with one of NASA’s primary reactor contractors on its space nuclear propulsion project, which aims to produce a demonstration nuclear thermal propulsion engine within a decade.”
Searight used Ansys Fluent, a modeling software, to design a simulation loop from a stainless steel pipe with an outer diameter of about two inches, with the help of Leigh Winfrey, associate professor and undergraduate program chair of nuclear engineering. The loop is connected to a hydrogen pump in the model and circulates hot hydrogen through a test section adjacent to a heating element.
While consistent heating of hydrogen to 2,200 degrees Fahrenheit was possible, Searight discovered that a heating element directly above the test section was required to prevent a reduction in heating. Data from the modeling software revealed that the flow of hydrogen through the test section was smooth and uniform, reducing uneven heat distribution through the loop, which could jeopardize the setup’s safety and lifespan. The results also confirmed that stainless steel would allow for more convenient and cost-effective construction of the loop.
“We are excited to take the first steps toward developing a one-of-a-kind capability for extreme environment simulation at Penn State,” Winfrey said. “This preliminary work will allow us to pursue research that has the potential to have a significant impact on the future of space exploration.”
Searight’s preliminary work could pave the way for expanded testing of materials that could one day be used to create faster, more efficient space travel using reactor-fueled rockets.
The George P. Shultz and James W. Behrens Graduate Scholarship was recently awarded to Searight by ANS. The award will help Searight continue his work on the test loop. Shultz, a nuclear nonproliferation advocate and Presidential Medal of Freedom recipient who died in February, and Behrens, a former ANS board member who held numerous positions in the national security sector, are both honored with the $3,000 scholarship.
A NASA Small Business Innovation Research contract supported this work.