Design,Fabrication And Performance Of Planar Solid Propellant Micro-thruster

Planar solid propellant micro-thruster has the advantages of simple structure,rapid response and adjustable thrust,which can be used as a micro-propulsion system for micro-satellite.In this paper,two kinds of micro-thrusters with different sizes were designed and fabricated used SU-8 photoresist and PCB as main substance.The energy conversion of Ni-Cr thin film bridge at constant current was studied.In addition,the design and performance of the propellant were also carried out.At last,the ignition and micro impulse performance of the micro-thruster was successfully tested.The main research contents and conclusions are as follows:The planar solid propellant micro-thruster with"sandwich biscuit"structure consisted of an ignition circuit layer,a combustion chamber layer（micro-medicine chamber and Laval nozzle）,and a sealing layer.Ni-Cr thin film bridge was used as ignition element.Gold material was used as wire and pad and PCB was used as sealing layer.SU-8 photoresist and PCB were used as main materials of combustion chamber with two different size.A double V-shaped Ni-Cr thin film bridge was designed,which meet the requirements of no firing of the 1A1W5min.Subsequently,the energy conversion performance of this Ni-Cr bridge was studied under constant current.The result shows that the 50%fusing current of the Ni-Cr bridge for 5 minutes was 1.785A,and the 50%bursting current of 50ms was 3.220A.The temperature rising process of the Ni-Cr thin film bridge was simulated using COMSOL software which shows that the corner of V-shaped bridge possessed the fastest heating rate.In addition,the energy matching relationship between the ignition bridge and the thermite was also investigated.The experiment showed that the 50%firing current of the Ni-Cr thin film composite Al/Cu O/NC firing device at 50ms was 3.052A.B/KNO₃ was assembled through a high voltage electrostatic spraying,and the nanoparticles were dispersed uniformly in NC binder.The effects of NC on the properties of B/KNO₃ were studied by means of SEM,DSC,T-jump ignition temperature,and closed bomb test.The results show that NC can improve the combustion performance and gas production thrust of B/KNO₃.Combustion chamber layers were fabricated by using SU-8 photoresist and PCB,and the effects of spin,pre-bake,exposure and developing parameter on photolithography result was studied.It shows that increasing the pre-bake time in an appropriate amount is helpful to eliminate the interfacial difference caused by the second spin.Insufficient exposure can easily cause swelling.And insufficient development time resulted in large line width deviation.The planar solid propellant micro-thruster was sealed and bonded by MD130 adhesive,and the propulsion performance was tested with a micro impulse test platform.The impulse of the micro thruster based on SU-8 photoresist loaded with 1.9mg nano thermite was 127.9μN·s,and the igniting time of which was 0.2ms.The impulse of micro thruster based on PCB used two layers of propellant（nano-aluminum agent for the bottom charge:0.9mg,and the main agent B/KNO₃/NC7.5%:12.0mg）was 1231.7μN·s,and their igniting time of which was 4.9ms.