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A key element in the development of more capable nano- and pico-satellites is the development of high specific impulse micro-propulsion systems, which allow for more challenging space missions to be flown. One such system being developed at TU Delft is a micro-resistojet with a planar supersonic nozzle geometry. This is currently fabricated by means of silicon etching, which is unfortunately relatively slow and expensive. As a faster, more accessible alternative, wire electric discharge machining has been used here for creating the supersonic nozzle. This method was combined with COTS heaters and a metal foam heat exchanger to create a new micro-thruster. The thruster was tested in vacuum using nitrogen as propellant at temperatures up to 400 °C. Results showed similar thrust and specific impulse values as reported by others for a comparable silicon-based micro-thruster, thereby confirming the validity of the novel manufacturing method., Aerospace Engineering

A key element in the development of more capable nano- and pico-satellites is the development of high specific impulse micro-propulsion systems, which allow for more challenging space missions to be flown. One such system being developed at TU Delft is a micro-resistojet with a planar supersonic nozzle geometry. This is currently fabricated by means of silicon etching, which is unfortunately relatively slow and expensive. As a faster, more accessible alternative, wire electric discharge machining has been used here for creating the supersonic nozzle. This method was combined with COTS heaters and a metal foam heat exchanger to create a new micro-thruster. The thruster was tested in vacuum using nitrogen as propellant at temperatures up to 400 °C. Results showed similar thrust and specific impulse values as reported by others for a comparable silicon-based micro-thruster, thereby confirming the validity of the novel manufacturing method., Aerospace Engineering

Miniaturized spacecraft (nanosats) require propulsion systems capable of providing extremely low levels of thrust (1-100 uN) and impulse (1uN sec). We have demonstrated the feasibility of a 'digital' monopropellant propulsion system in which the delivery of the monopropellant is in the form of discrete and dispersed microscopic slugs. By utilizing recent developments in experimental microfluidics, a controlled slug formation process represents a virtual 'self-valving' mechanism which affords finer resolution than a micro-valve for a continuous stream. Through a combination of experiment and computation, we have demonstrated the ability to controllably deliver monopropellant fuel as dispersed droplets leading to a throttling of the flow rate by as much as 50% over a continuous flow. This throttling capability allows impulse bits to be correspondingly reduced. In parallel, microfabrication efforts have produced a novel catalytic micro-reactor prototype for the monopropellant decomposition using ruthernium-oxide nanorods. Finally, extensive computational studies have yielded comprehensive performance information critical to the micro-scale design of efficient supersonic nozzles for incorporation in the propulsion system., The original document contains color images.