To: <[EMAIL PROTECTED]> From: "J. R. Molloy" <[EMAIL PROTECTED]> Mailing-List: list [EMAIL PROTECTED]; contact [EMAIL PROTECTED] Delivered-To: mailing list [EMAIL PROTECTED] Date: Tue, 16 Jan 2001 10:03:56 -0800 Reply-To: [EMAIL PROTECTED] Subject: [>Htech] MICRO-THRUSTERS PHASE-CHANGE MICRO-THRUSTERS http://sec353.jpl.nasa.gov/apc/Micropropulsion/01.html MEMS (Micro-Electromechanical Systems) based phase change thruster concepts are currently under investigation matching Class I and II microspacecraft requirements. Among the concepts considered are subliming solid micro-thrusters and vaporizing liquid micro-thrusters, currently under development at JPL. Fabrication of both thruster types relies on micro-machining methods similar to those used in the micro-electronics industry in order to obtain nozzle throat sizes small enough to obtain the required low thrust and impulse bit performances. Both thruster types also use non-gaseous propellants in order to reduce leakage problems. Currently, no suitable flight qualifiable microvalve concept exists to reduce leakage rates. In the case of the subliming solid microthruster, a solid propellant (ammonia salts) is sublimated by heating the tank until a suitable tank pressure is reached. Then a microvalve is opened (due to solid propellant storage the leak rate requirements for this valve are not very stringent) and the gaseous phase of the propellant is vented to produce thrust. In the case of the vaporizing liquid thruster, a suitable liquid propellant (e.g. water, ammonia, hydrazine) is fed into a micro-thin film heater assembly that vaporizes the propellant just prior to exiting the nozzle. Both concepts are in the early development stage at JPL. Hardware fabrication has begun and thrust stand tests are expected to be performed in 1997. Many feasibility issues, however, remain with these and other potential micro-thruster concepts. **Article includes excellent graphics** ô¿ô Stay hungry, --J. R. 3M TA3 Useless hypotheses: consciousness, phlogiston, philosophy, vitalism, mind, free will -----BEGIN TRANSHUMANTECH SIGNATURE----- Post message: [EMAIL PROTECTED] Subscribe: [EMAIL PROTECTED] Unsubscribe: [EMAIL PROTECTED] List owner: [EMAIL PROTECTED] List home: http://www.egroups.com/community/transhumantech/ Alt archive: http://www.planetx.com/majordomo/transhumantech/ Old archive: http://www.planetx.com/transhumantech/threads.html -----END TRANSHUMANTECH SIGNATURE----- (u are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
