General Atomics Electromagnetic Systems (GA-EMS) has successfully tested the nuclear fuel that may one day propel and power the spacecraft of the future. The trials verify that the fuel can survive the harsh environment of a nuclear rocket reactor.
Up until now, the main way of propelling spacecraft has been through chemical rockets. To be fair, that's nothing to sneer at. Chemical engines put the first satellite into space, the first man on the Moon, and have sent the first deep space probes hurtling out of our solar system.
However, chemical rockets have reached the theoretical limits of their capabilities. In fact, they already did so when the first German V-2 rocket reached space in 1942. Since then all the advances have been in making rockets larger and more efficient through innovations peripheral to the rocket engine itself.
There are alternatives to chemical rockets, such as ion drives and solar sails, but these produce minuscule thrust and have limited applications. For really ambitious projects, what space engineers want is something with at least a third more power than the best chemical rocket. If such an engine could be made, it would allow for fast shuttles between low Earth orbit and the Moon, the ability to quickly shift orbits at short notice, and to send large crewed missions to Mars and other planets in a reasonable time frame.
The best, in fact, the only, candidate for this is the Nuclear Thermal Propulsion (NTP) system or nuclear rocket. First conceived of in 1945, this is a rocket that replaces burning chemical fuel with a nuclear reactor that is used to heat up a propellant. This propellant is most likely hydrogen, though anything could be used, including water. This is because the propellant doesn't provide any power. It's just reaction mass to be expelled to generate thrust according to Newton's First Law.
The basic principle is simple but with engineering the devil is always in the details. One of these details is that such a reactor must operate at very high temperatures and strong vibrations and survive. We're talking 2,326 °C (4,220 °F), with highly reactive superheated hydrogen gas thrown into the bargain.
Any conventional nuclear fuel would have trouble standing up to that but what the rocket engineers need is a fuel that can not only survive, but refrain from cracking or splintering in the process.
According to Scott Forney, president of GA-EMS, the recent tests carried out at NASA’s Marshall Space Flight Center at Redstone Arsenal, Alabama have proven that the latest fuel can survive without erosion or degradation at operational temperatures. The fuel was subjected to full reactor heat and hydrogen gas and kept there for 20 minutes – about what a nuclear engine would have to endure during a boost maneuver. Other tests looked at how the fuel handled variations in protective features that weren't specified.
"To the best of our knowledge, we are the first company to use the compact fuel element environmental test (CFEET) facility at NASA MSFC to successfully test and demonstrate the survivability of fuel after thermal cycling in hydrogen representative temperatures and ramp rates," said Dr. Christina Back, vice president of GA-EMS Nuclear Technologies and Materials. "We’ve also conducted tests in a non-hydrogen environment at our GA-EMS laboratory, which confirmed the fuel performed exceptionally well at temperatures up to 3,000 °K (4,940 °F, 2,726 °C), which would enable the NTP system to be two-to-three times more efficient than conventional chemical rocket engines. We are excited to continue our collaboration with NASA as we mature and test the fuel to meet the performance requirements for future cislunar and Mars mission architectures."
Source: General Atomics
