THERMAL TRANSPIRATION BASED MICROSCALE PROPULSION AND POWER GENERATION DEVICES

With the continually decreasing size and weight of communication, control and instrumentation systems for aerospace vehicles due to advances in microelectronics and micro electro-mechanical systems (MEMS), there is considerable interest in miniaturizing the propulsion and power systems as well. While many miniature space and airbreathing propulsion system concepts have been proposed, e.g. [1], most require moving parts. All miniaturized propulsion devices with moving parts experience more difficulties with heat and friction losses due to higher surface to volume ratios than their macroscale counterparts. Moreover sealing, fabrication and assembly are much more difficult at small scales because microfabrication processes have much poorer relative precision than convectional macroscale processes. Additionally, all air and space vehicles, regardless of size, require electrical power. The use of combustion processes for electrical power generation provides enormous advantages over batteries both in terms of energy storage per unit mass and in terms of power generation per unit volume, even when the conversion efficiency in the combustion process from thermal energy to electrical energy is taken into account. Most current micro-scale power generation concepts employ scaled-down versions of existing macroscale devices, in particular internal combustion engines, though again such micro-devices experience more difficulties with heat losses, friction, sealing, fabrication, assembly etc. than their macroscal