Scale-Up Manufacturing and Evaluation of All-metal FEEP/Colloid emitter arrays
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Transcript of Scale-Up Manufacturing and Evaluation of All-metal FEEP/Colloid emitter arrays
Scale-Up Manufacturing and Evaluation of
All-metal FEEP/Colloid emitter arrays
Dr. Craig Friedrich
Dr. Jeff Allen
Dr. L. Brad King
Background and Motivation – Apply Experience and Proven Technology of Mechanical Micromachining
Micromilling with 1um lateral x 4um vertical steps
Liquid metal jet micromilled in moly – exit 100um
Optical metrology, nm vertical, sub-micron lateral
25um drilled hole and wire thru hair
Micromilling machine – rebuild to update stages
and controls
Objective of Research – Mass Fabrication and Large Array Thrusters to Support Testing and Further Thruster Development
Taylor cone emissionsite
Single emitterneedle
ElectrochemicallyEtched Tungsten Emitter Tip
Capillary flow ofLiquid metal (FEEP)Or ionic liquid (Colloid)
Goal is arrays of emitters that have predictable performance and low cost, one piece with no assembly, near net shape with PM, net shape with finish EDM if necessary.
Micromachined molybdenum substrate with
holes and well, tungsten wires inserted, tips chemically etched
Technical Approach – Micromachining of Green Compact Molds and Compaction for Thruster Arrays and Further Thruster Development
Propellant Reservoir
Green / sintered refractory metal, more
complex green molding
Propellant Reservoir
Green / sintered refractory metal, easier complex green molding
Schematic Only – Not to Scale
Touch-up EDM possible if needed
Technical Approach - Sintering of Compacted Nano / Micropowders
Material Rel. Density
Rel. Resistivity
Rel. Therm. Cond.
Rel. Therm. Exp.
Sinter Temp C
Sinter time (min.)
Molybdenum 1 2.48 2.4 1.07 2050 120
Tantalum 1.62 1.01 1 1.4 2400 480
Tungsten 1.87 1 3.01 1 2350 480
Nanopowder particles are 50 – 100 nanometers in size and have a specific surface area of several square meters per gram;
Michigan Tech has the capability to micromachine molds, produce green compacts, and sinter these powders creating nano / microporous thrusters for efficient indium wetting;
Robust fabrication process will allow further thruster development addressing refractory metal porosity (powder size), indium feed system (interior vs exterior feed, cone geometry), etc.
Anticipated Results
A repeatable process whereby FEEP/colloid thruster arrays can be produced quickly and inexpensively via mechanical microfabrication processes and whereby the performance of these thrusters can be established;
Develop a process and fabrication testbed whereby arrays of emitter tips can be manufactured for testing;
Use the fabrication testbed to determine how fabrication process variables affect thruster performance;
Use the fabrication testbed to determine how thruster geometry affects propellant flow and wetting;
Use the fabrication testbed to establish limits on size and number of emitters in an array, and the cost vs performance.