Cutler, James

Longmier, Benjamin

Sheehan, J.P

DigitalCommons@USU

The Plasma Ambipolar Thruster for Responsive In-Orbit Transfers(PATRIOT) MissionJ. P. Sheehan, Benjamin W. Longmier,and James CutlerOutline• Propelled nanosatellite missions• The CubeSat Ambipolar Thruster (CAT)– Design– Magnetic field– Initial firing• Micronewton thrust stand• PATRIOT mission goals11th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014 2Maneuverable CubeSats could enable many new missions• Previously inaccessible orbits– Orbits that are not accessed by launch vehicle– Highly elliptical orbits– Geostationary orbits– Polar orbits– Earth-Moon, Earth-Sun Lagrange points• Cluster formation flying• Long-lived low altitude orbits 3Credit: NASA11th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014CubeSat Ambipolar Thruster (CAT)• ~0.6U for thruster• Mass: <1 kg• 0.4U – 0.9U for propellant tank• Uses “free” spring space4• ~1U for spacecraft controls• 0.5U – 1.0U for instruments• Powered by 10s of V• 10 – 50 W, assisted by batteries11th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Plasma liner contains plasma, directs flow of gas• Quartz tolerates high temperatures• Showerhead disperses gas, protects downstream elements from plasma• Physical nozzle follows magnetic nozzle511th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Antenna generates plasma,heats electrons• 3D printed– Complex geometries possible• Solid silver to maximize conductivity• Helical half-twist– Ideal for launching helicon• Power leads connect to RF source• Couples RF energy into electrons via helicon plasma wave611th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Faraday shield contains RF,encases thruster• 3D printed– Low cost– Rapid iteration• Titanium• Contains RF within thruster• Structural support for liner, magnets711th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Fully assembled CAT engine811th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Magnetic nozzle replacesphysical rocket nozzle911th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Measurements match simulations to within 10%10• Permanent magnets– No power requirements– Currently NdFeB– SmCo for higher Curie temperature• Maximum strength in device of 800 G• Net dipole moment of 55 A·m2– Dipole cancelation designs• Earth’s gravity takes over at ~40 cm11th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Xenon testing: plasma follows magnetic field lines1111th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Beam-deflection micronewton thrust stand12• Measure 10s mN, resolution 10s μN• Thruster supported on mount plate• Thrust moves plate, deflects thin beams– Euler-Bernoulli beam theory• Deflection measured by optical displacement sensor (obscured)• Tensionless gas feed system11th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014PATRIOT mission will testCAT on orbit• Objectives– Turn CAT on– Thrust measurement– Observable orbit change– Earth escape• Multiple flights• Non-propulsion requirements– Long range communications– Power systems– Attitude control– RF shielding1311th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Conclusions• CAT’s magnetic field is consistent with predictions to within 10%• Inductive discharge achieved in prototype device• Novel thrust stand in development• Wide variety of propellants being explored1411th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Tensionless gas connector• Deliver gas without restricting motion• Coaxial feed design• Viscous, non-volatile liquid – Galinstan: eutectic metal• Liquid damps oscillations• Similar design in development for RF15gas inviscous liquidgas out11th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Design procedure and parameters• Design begins from power requirements• Plasma density, B field driven by helicon dispersion relation• Approximate performance parameters for 3U CubeSat, xenon propellant1611th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Magnets create converging-diverging magnetic field• NdFeB permanent ring magnets• Magnetic field           at throat: 800G• Decays to Earth’s magnetic field            in 40 cm• Plasma detaches at 0.5 G at the furthest• Nozzle efficiency: 83%173U CubeSat      .Note: figure does not represent final magnet design11th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Passive magnetic stabilization1811th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Earth escape from LEOfiring from perigee1911th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Thrust stand for micronewtonforce measurements2011th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Mission to Europa:6U CubeSat, double CATs2111th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Ambipolar ion acceleration mechanism• Electrons heated by helicon wave• Electrons rush out of nozzle• Slow ions dragged along by  E field• Electrons lose thermal energy to ion kinetic energy• Higher electron temperature → higher ion velocity• Eion = 2Te• Mechanism is critical for thrust, performance models2211th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014Quasi-1d3v particle-in-cell simulations in development• Axial spatial dimension• Axisymmetric• Magnetic mirror forces accounted for𝐵𝐵𝑟𝑟 = −𝑟𝑟𝐿𝐿2 𝜕𝜕𝐵𝐵𝑧𝑧𝜕𝜕𝜕𝜕• Modified semi-implicit Boris algorithm particle mover• Verification campaign nearly completed– Two-stream instability (right)– Sheath– Magnetic mirror2311th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014• Gases: xenon, krypton, argon– Benchmark testing– Flight certified hardware– Miniature flow systems• Solids and liquids: no pressure vessel• Solid/liquid propellants– Water– Galinstan– Mercury– Iodine• Iodine propellant system– Solid storable– Heat to control vapor pressure/mass flow rateSolid storable propellants greatly reduce volume requirements2411th Annual Summer CubeSat Developers’ Workshop, Logan, UT, Aug. 3, 2014

The Plasma Ambipolar Thruster for Responsive In-Orbit Transfers (PATRIOT) Mission

https://digitalcommons.usu.edu/cgi/viewcontent.cgi?filename=0&article=3150&context=smallsat&type=additional

The Plasma Ambipolar Thruster for Responsive In-Orbit Transfers (PATRIOT) Mission

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