Electrothermal feasibility of carbon microcoil heaters for cold/hot gas microthrusters
2006 (English)In: Journal of Micromechanics and Microengineering, Vol. 16, 1154-1161 p.Article in journal (Refereed) Published
With the miniaturization of spacecraft the need for efficient, accurate and low-weight attitude control systems is becoming evident. To this end, the cold/hot gas microthruster system of this paper incorporates carbon microcoils—deposited via laser-induced chemical vapor deposition—for heating the propellant gas (nitrogen) before the nozzle inlet. By increasing the temperature of the propellant gas for such a system, the specific impulse (Isp) of the microthruster will increase. The benefits of a higher Isp are lower propellant mass, higher thrust and shorter burning times. Therefore, the feasibility of achieving this increase with the carbon microcoils is investigated. The carbon microcoils have been characterized experimentally with respect to their electrothermal performance, i.e. resistance, temperature, parasitic heat losses and degradation in ambient. The resulting heat losses from the heater and the heated gas have been estimated through a combination of experiments, numerical simulation and approximate analytical expressions. At high powers, degradation of the carbon material leads to coil failure in ambient where trace oxygen was present. Thus, the next generation of carbon microcoils to be tested will have a protective coating to extend their lifetime. Theoretical modeling showed that an increase in the propellant gas temperature from 300 to 1200 K and a corresponding two-fold increase in the Isp can be achieved if 1.0 W of power is supplied to each coil in a three-coil thruster. These simulation results show that if the coils are capable of dissipating 1 W of heat at 1700 K coil temperature, the doubling of the Isp may be achieved. Comparing to the electrothermal characterization results we find that the carbon coils can survive at 1700 K if protected, and that they can be expected to reach 1700 K at power below 1 W.
Place, publisher, year, edition, pages
2006. Vol. 16, 1154-1161 p.
Inorganic Chemistry Engineering and Technology
IdentifiersURN: urn:nbn:se:uu:diva-22611DOI: 10.1088/0960-1317/16/7/007OAI: oai:DiVA.org:uu-22611DiVA: diva2:50384