微型推进器

Micro Aerospace Solutions Micro Wet mass = 175 g ••II = .17 mNs bit = .17 mNs bit ••Thrust = 50 mN Thrust = 50 mN ••Size = 2” diameter tank Size = 2” diameter tank ••4 thrusters 4 thrusters ••Lifetime = 50,000 firings Lifetime = 50,000 firings ••Flight-ready Flight-ready
the PPT man
Andy Sadhwani 2006 Thrusters Team Leader
Pulsed Plasma Microthruster
0.03 A
5V
Voltage Stepper 1500 V
1000 A for 10 ns
Capacitor
Pros
Teflon Coax
High ISP Small Low Power
Vacuum Arc Thrusters (VAT)
Different cathodes vary impulse Variable pulsing (width & freq) Lighter PPU than PPT MVAT – increased thrust? High EMI Not tested Hard to fit 3 in CubeSat
CubeSat Constraints
What’s so hard about adding thrusters?
Size: < 10 x 10 x 10 cm Weight: < 1 kg Power: < 1 Watt Minimum Ibit ~ 10-4 Ns Flight ready ? Affordable ?
Solid Propellant MEMs
High propellant densities Low power No moving parts, feed systems, pumps, leakage Tiny arrays of multiple nozzles allow for range of thrust One-time-only firing Too expensive!
Monopropellant MEMs Bipropellant MEMs Solid Propellant MEMs Cold gas thrusters (micro & MEMs)
. . . more?
Evaluation Criteria
Primary Propulsion vs Attitude Control?
SSTL [Water] SSTL [Water] ••Power = 3 W Power = 3 W ••Dry Mass = 13 g Dry Mass = 13 g ••Thrust = 3.3 mN Thrust = 3.3 mN ••Size = 10 cm long Size = 10 cm long
Picture courtesy of Northrop Grumman
Picture courtesy of LAAS, France
Cold Gas Thrusters
Reliable, simple systems with long flight history Benign propellants High Ibit Continuous & pulsed operations Propellant volume Very low power COTS valves available Leakage
Cons Low Thrust EM Interference Much R&D Left
Specs Thrust: 0.006 mN Rotate 90º: 12 min (4,500 pulses) Lifetime: Forty 90° rotations (200,000 pulses ) Input: 5 V at 30 mA Output: 1500 V at 1000 A for 10 ns at 6 pps
Marotta Marotta ••Dry mass = 50 g Dry mass = 50 g ••II = 44 mNs bit = 44 mNs bit ••Thrust = 445 mN Thrust = 445 mN ••Power = 0.4 W Power = 0.4 W ••Flight-ready Flight-ready
UK-DMC Micro-Resistojet, 2003
MEMs Resistojet
Entire system on silicon chip Easy to fit 3 axis system Research at: Aerospace Corp, Tshingua U, Indian Institute of Technology Still in research stage Thrust not well characterized
Thrust < 1 N vs Ibit ~ 0.1 mNs
CubeSat constraints:
1 kg, including all fuel 1 W (average power) 10 x 10 x 10 cm cheap!
(Viable) Types of Micropropulsion
Alameda Applied Sciences Alameda Applied Sciences ••Power = 4 W Power = 4 W ••Mass = 150 g Mass = 150 g ••Thrust = 54 uN (90° in 10 min) Thrust = 54 uN (90° in 10 min) ••II = 1 uNs bit = 1 uNs bit ••Size = 4 xx4 xx4 cm Size = 4 4 4 cm
Micropropulsion for Nanosatellites
Olivia Billett - AA 236A 2006
Mission Statement
Why do we need thrusters for CubeSats?
Attitude Control Camera Pointing Formation Flying Rendezvous Vehicle Inspection Orbit Changes De-Orbit Capability Research and Development Because they’re cool
Picture courtesy of Nasda.go.jp
Picture courtesy of Micro Aerospace Solutions website
Bipropellant MEMs
Very high thrust-to-weight ratio High propellant densities Low power Research at Stanford (Mech Eng) Ibit too high for attitude control. Good for primary propulsion only Still in research stage More complex system, harder to fabricate
Electric Propulsion
Pulsed Plasma Thruster (PPT) Vacuum Arc Thruster (VAT) Micro Resistojet Colloid Microthrusters
Chemical Propulsion
Monopropellant MEMs Bipropellant MEMs Solid Propellant MEMs Cold gas thrusters (micro & MEMs)
Chemical Propulsion
Monopropellant MEMs Bipropellant MEMs Solid Propellant MEMs Cold gas thrusters (micro & MEMs)
Monopropellant MEMs
High propellant density Low power, high Isp Wide range of impulse and thrust levels Hyrazine (high Isp) and hydrogen peroxide (noncorrosive, easy handling) Essentially size of 1U High Ibit
MTU HuskySat micro-Vacuum Arc Thruster
Micro Resistojet
Simple system Fuel: water, nitrous oxide Larger versions used for years Low impulse Test failed – propellant leak? Research discontinued (water) Weight of propellant
(Viable) Types of Micropropulsion
Electric Propulsion
Pulsed Plasma Thruster (PPT) Vacuum Arc Thruster (VAT) Micro Resistojet Colloid Microthrusters
Chemical Propulsion