Los Alamos National Laboratory (LANL) scientists recently flight tested a new rocket design that included a high-energy fuel and motor design that they say also delivers a high degree of safety.
Bryce Tappan, energetic materials chemist at LANL, said Thursday in a statement that, typically, a propellant that is high performance is not as safe of a material. Conventional solid-fuel motors work by combining a fuel and an oxidizer, a material usually rich in oxygen, to enhance the burning of the fuel. In higher-energy fuels, this mixture can be somewhat unstable and can contain sensitive high explosives that can detonate under high shock loads, high temperatures or other conditions.
Tappan said Thursday in an email the innovation of the new rocket design is separating the fuel from the oxidizer, as they, by themselves, are not able to detonate. This adds a higher degree of safety, allowing use of higher-energy propellants.
The experimental fuel used in the flight tests was based on high-hydrogen/high-nitrogen energetic salts and was developed and optimized specifically for this rocket. Numerous formulations were tested before the final flight motor was developed, he said. The oxidizer used in the experimental flight motor, Tappan said, was based on ammonium perchlorate. The commercial rocket was powered by aluminized ammonium perchlorate fuel with a hydroxyl-terminated polybutadiene oxidizer mixed together, as usual with traditional solid fuels.
Tappan said the experimental engine design is referred to as the segregated fuel-oxidizer system. This is much like a “reverse hybrid” rocket, he said, in which a liquid fuel would be pumped into a solid oxidizer grain, except LANL used a solid-solid system that provides gaseous fuel, mostly hydrogen, from the decomposition of the energetic fuel portion of the motor.
Multiple flight tests took place on Sept. 25 in Socorro, N.M., on one-inch diameter rockets. One rocket powered by the experimental fuel was tested at the same time as another powered by commercial fuel, each on multiple occasions, to enable a comparison of data gathered on velocity, altitude, burn rate and other parameters.
Tappan said the peak velocity of the experimental motor was about 700 feet per second (ft/s) with a burn time of under one second. The commercial motor, he said, had a peak velocity of around 360 ft/s with a burn time of about 1.5 seconds. Tappan said the altitude of the experimental motor was about 1,100 feet and 1,300 feet for the commercial motor, which had slightly more propellant mass and less drag due to the lower thrust.
Researchers will now work to scale-up the design, as well as explore miniaturization of the system, to exploit all potential applications that would require high-energy, high-velocity and correspondingly high safety margins.
LANL is operated by Los Alamos National Security LLC, a team composed of Bechtel, the University of California, the Babcock & Wilcox Company [BWC] and URS Corp. [URS] for the Energy Department’s National Nuclear Security Administration (NNSA).