Characteristics of Two Phase Fluids as Microthruster Propellant

Nano- and picosatellites are small satellites that are a more affordable alternative to larger satellites. Nanosats are satellites with a mass ranging from 1kg to 10kg while picosats have a mass that ranges from 0.1kg to 1kg. In addition to their cost, the smaller satellites have the advantage that they are able to carry out missions that would be difficult for a larger satellite. These advantages include using formations to gather data from multiple points and in-orbit inspection of larger satellites. Nano/picosats can be fabricated or procured for under $25k and launched into space for around another $40–60k which makes the total pre-mission expenditures for the satellite under $100k. Currently these satellites have a limited ability to orient themselves and cannot perform orbital maneuvers. For example a satellite could potentially use electro-magnetically charged coils in conjunction with earth’s magnetic field to orient themselves. The problems with the current methods of orientation are they are extremely slow to damp out oscillations due to low power (minutes) and cannot execute out of orbit maneuvers. Once a satellite is deployed from its launcher it is on a set orbit and cannot change its orbital elements on-command for the duration of its mission, limiting their use for science missions. Thus, it would be extremely beneficial for the nano- and pico-satellite community if a micro propulsion system capable of full-authority attitude control and orbital maneuver is developed. This paper describes the limiting characteristics of the refrigerant-based propellant (such as 1,1,1,2-Tetraflurorethan <R-134a> or 1,1-difluoroethane <R-152a>) for the cold gas systems that is currently under development.