Small satellites are a big deal these days, with mini-, micro-, nano- and pico-satellites. There are even femto-satellites, each weighing less than 100 grams. Although tiny spacecraft are already in use for some applications, work is continuing on micropropulsion systems for them.
Sandia National Laboratories and Northrop Grumman Corporation (NGC) are collaborating under a Cooperative Research and Development Agreement (CRADA) to improve the performance of microthrusters, or “rockets on a chip,” which can provide impulse for small vehicles, such as satellites.
Microthrusters are individual microelectromechanical systems (MEMS) which can be manufactured using semiconductor fabrication techniques. Each the size of a poppy seed, microthrusters can be manufactured in arrays to produce controlled “impulse bits” of thrust.
The NGC-led MEMS Digital Thruster Program is producing microthrusters for orbital insertion and control, and attitude control functions on small satellites. Propulsion is adjusted in increments by igniting individual thrusters, several thrusters at once, or by firing thrusters in controlled sequences. Microthrusters are so small and light, the propulsion function can be combined with the satellite structure to deliver the required mission delta-v (change in velocity) while minimizing the added weight.
One of the challenges in putting together microthrusters is loading the propellant, and SNL has expertise in advanced manufacturing techniques in propellant loading, as well as in microscale combustion and high-speed diagnostics. SNL has been working to improve performance over what was initially achieved in the late ‘90s.
Under a recently awarded Air Force Research Laboratory (AFRL) contract, Sandia will be performing characterization on both the igniters and the propellant, and the U.S. Air Force Academy, with Cadet participation, will be performing wind tunnel tests to characterize the performance of NGC-fabricated microthrusters. Under a previous Defense Advanced Research Projects Agency (DARPA) contract, thrust from the microthrusters was demonstrated in both the laboratory and in space on board an experimental sounding rocket.
Sandia and NGC have worked together for many years to advance a wide range of technologies. In 2011, the microthruster project was renewed and expanded with an Umbrella CRADA, allowing even more collaboration. Over the years, the partners have studied and developed electron beam (EB) polymer matrix composite (PMC) curing technology, unmanned air vehicle (UAV) persistence capabilities, and worked on other technologies applicable to Sandia’s and NGC’s national security missions.
With the goal of developing and commercializing innovative technologies, Sandia and NGC have joined forces in various disciplines including electronic systems, aerospace, defense, and systems engineering. In the coming months, the partners hope to collaboratively study and develop a high-power solar electric propulsion flight system extensible to NASA’s future transportation and exploration needs.