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Slide 1 - Mechanical Engineering at Michigan Tech

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Slide 1 - Mechanical Engineering at Michigan Tech Powered By Docstoc
					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       Liquid metal jet micromilled
                           lateral x 4um vertical steps      in moly – exit 100um




 Micromilling machine –      Optical metrology, nm         25um drilled hole and wire
rebuild to update stages   vertical, sub-micron lateral            thru hair
      and controls
  Objective of Research – Mass Fabrication and Large Array Thrusters to
            Support Testing and Further Thruster Development




                              Taylor cone emission
                              site


Single emitter
   needle                   Capillary flow of
                            Liquid metal (FEEP)
                            Or ionic liquid (Colloid)
                                                             Micromachined
                                                        molybdenum substrate with
                        Electrochemically                holes and well, tungsten
                        Etched Tungsten Emitter Tip         wires inserted, tips
                                                            chemically etched

 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.
Technical Approach – Micromachining of Green Compact Molds and
 Compaction for Thruster Arrays and Further Thruster Development

                                              Green / sintered
                                          refractory metal, more
                                         complex green molding


        Propellant Reservoir
                                                   Touch-up EDM
                                                  possible if needed


                                             Green / sintered
                                         refractory metal, easier
                                         complex green molding


         Propellant Reservoir

                  Schematic Only – Not to Scale
    Technical Approach - Sintering of Compacted Nano / Micropowders
   Material    Rel.     Rel. Resistivity   Rel. Therm.   Rel. Therm.    Sinter   Sinter time
              Density                        Cond.           Exp.      Temp C       (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.

				
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posted:5/10/2013
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