lecture-17 ppt for cubesat
TRANSCRIPT
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
CubeSat Constraints
� Size: < 10 x 10 x 10 cm
� Weight: < 1 kg
� Power: < 1 Watt
� Minimum Ibit ~ 10-4 Ns
� Flight ready ?
� Affordable ?
What’s so hard about adding thrusters?
Previous Missions
What kinds of micropropulsion are currently in use?
Not much. As of 2006:
• 1 CubeSat (UIUC ION), pending launch
• Few nanosats (UW, MTU, U Toronto) but no launches scheduled
In student satellites:
In industry satellites:
Increasing interest from DARPA, AFRL
• SSTL, Northrop Grumman, JPL
(Viable) Types of Micropropulsion
� 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)
. . . more?
Evaluation Criteria
� Primary Propulsion vs Attitude Control?
� 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
� 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)
the PPT man
Andy Sadhwani
2006 Thrusters Team Leader
Pulsed Plasma Microthruster
�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
Specs
�Low Thrust
�EM Interference
�Much R&D Left
�High ISP
�Small
�Low Power
ConsPros
5 VVoltage
Stepper
1500 V Capacitor
0.03 A
1000 A for 10 ns
Teflon Coax
Vacuum Arc Thrusters (VAT)
� Different cathodes vary impulse
� Variable pulsing (width & freq)
� Lighter PPU than PPT
�MVAT – increased thrust?
MTU HuskySat micro-Vacuum Arc
Thruster
� High EMI
� Not tested
� Hard to fit 3 in CubeSat
Alameda Applied Sciences
• Power = 4 W
• Mass = 150 g
• Thrust = 54 uN (90° in 10 min)
• Ibit = 1 uNs
• Size = 4 x 4 x 4 cm
Alameda Applied Sciences
• Power = 4 W
• Mass = 150 g
• Thrust = 54 uN (90° in 10 min)
• Ibit = 1 uNs
• Size = 4 x 4 x 4 cm
Micro Resistojet
UK-DMC Micro-Resistojet, 2003
� Simple system
� Fuel: water, nitrous oxide
� Larger versions used for years
� Low impulse
� Test failed – propellant leak?
� Research discontinued (water)
� Weight of propellant
SSTL [Water]
• Power = 3 W
• Dry Mass = 13 g
• Thrust = 3.3 mN
• Size = 10 cm long
SSTL [Water]
• Power = 3 W
• Dry Mass = 13 g
• Thrust = 3.3 mN
• Size = 10 cm long
� Entire system on silicon chip
� Easy to fit 3 axis system
� Research at: Aerospace Corp, Tshingua U, Indian Institute of Technology
MEMs Resistojet
� Still in research stage
� Thrust not well characterized
IIT
• Power = 1 – 2.4 W
• Thrust = 5 - 120 uN
• Size = 2.5 x 2.5 mm
IIT
• Power = 1 – 2.4 W
• Thrust = 5 - 120 uN
• Size = 2.5 x 2.5 mm
Colloid Microthrusters
� High current � droplets and ions, high ISP
� Low current � droplets only, low ISP
� Tiny arrays of multiple needles with micromachining
� Need external neutralizer
� Operating voltage ~ 15 kV
� Far from flight-ready – still in research stage, unreliable
Busek
• Power = 2 W
• Mass = 80 g
• Thrust = 1 mN
Busek
• Power = 2 W
• Mass = 80 g
• Thrust = 1 mN
(Viable) Types of Micropropulsion
� 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)
Monopropellant MEMs
� High propellant density
� Low power, high Isp
�Wide range of impulse and thrust levels
� Hyrazine (high Isp) and hydrogen peroxide (non-corrosive, easy handling)
� Essentially size of 1U
� High Ibit
Micro Aerospace Solutions
• Wet mass = 175 g
• Ibit = .17 mNs
• Thrust = 50 mN
• Size = 2” diameter tank
• 4 thrusters
• Lifetime = 50,000 firings
• Flight-ready
Micro Aerospace Solutions
• Wet mass = 175 g
• Ibit = .17 mNs
• Thrust = 50 mN
• Size = 2” diameter tank
• 4 thrusters
• Lifetime = 50,000 firings
• Flight-ready
Picture courtesy of Micro Aerospace Solutions websitePicture courtesy of Nasda.go.jp
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
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!
Picture courtesy of Northrop Grumman Picture courtesy of LAAS, France
Cold Gas Thrusters
� Reliable, simple systems with long flight history
� Benign propellants
� Continuous & pulsed operations
� Very low power
� COTS valves available
� High Ibit� Propellant volume
� Leakage
Marotta
• Dry mass = 50 g
• Ibit = 44 mNs
• Thrust = 445 mN
• Power = 0.4 W
• Flight-ready
Marotta
• Dry mass = 50 g
• Ibit = 44 mNs
• Thrust = 445 mN
• Power = 0.4 W
• Flight-ready
Flight history on microsatellites:
NASA ST missions
Picture courtesy of Marotta
Cold Gas MEMs – VACCO MiPS
� Chemically etched valves and system
� Fits all constraints
� Butane propellant – easy handling
� Designed for CubeSats
� Expandable propellant tank
� Not ready/ not for sale?
VACCO
• Wet mass = 456 g
• Ibit = .55 mNs
• Thrust = 55 mN
• Size = 2.5 x 10 x 10 cm
• 5 thrusters � 3-axis control
• Designed for CubeSats
VACCO
• Wet mass = 456 g
• Ibit = .55 mNs
• Thrust = 55 mN
• Size = 2.5 x 10 x 10 cm
• 5 thrusters � 3-axis control
• Designed for CubeSats
Picture courtesy of VACCO Industries
VACCO Piezoelectric Thrusters
Liquid valve
Thruster valve
120 psi
Fuel storage tank10-15 psi
Plenum
2 identical 1” valves controlling flow of iso-butane
10 mN thrust
• 220 ms pulse � 1.5 deg/s rotation rate
• 90 degree turn in 60 seconds
Low power
• To open valve: 200 mW for 20 ms
• No power required to keep valve open
PV=nRT
P
T
Isobutane Self-pressurization
Problem…
Only 2 thrusters donated by VACCO/JPL
. . . can spin up but can never spin down
• Centrifugal effect separates different phases of butane
• Allows complete single-axis control
Gas
Liquid
Inlet tubePerforated baffle plate
Solution: 2-Thruster Design
Tank Location in 2U Assembly
Moment of Inertia
Single Axis
Rotation
Temperature
Protection
Tank Sizing and Characteristics
256320.93
384531.40
769062.79
ManeuversVolume (cm3)
Full Volume = 62.7cm3
Pressure ~ 44 psi @20oC
(Viable) Types of Micropropulsion
� 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)
� Electric Propulsion� Pulsed Plasma Thruster (PPT)
� Chemical Propulsion� Cold gas thrusters (micro & MEMs)
Questions?