Deep Space Propulsion Systems - University of Thessaly · Deep Space Propulsion Systems. Dr. Joshua...
Transcript of Deep Space Propulsion Systems - University of Thessaly · Deep Space Propulsion Systems. Dr. Joshua...
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Deep Space Propulsion Systems
Dr. Joshua L. RoveyAssistant Professor of Aerospace EngineeringMissouri University of Science & Technology
Presented to:Missouri S&T Physics Colloquium
January 28th, 2010
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Outline
I. Rocket Propulsion Basics1) Propulsion, an energy conversion process2) Mustang vs. Prius, Chemical vs. Electric3) Deep-space, the Need for Speed
II. State-of-the-Art Deep Space Propulsion1) SoA Ion Thrusters2) Ion Thruster Physics3) Effects of Long-lifetime Operation
III. The FUTURE!1) Available Power in Space2) Why Plasmoid Propulsion?3) Current efforts in Plasmoid Propulsion
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PART I:Rocket Propulsion Basics
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Propulsion Basics
Stored Chemical/Electric Energy
An Energy Conversion Process
Propellant Stream Kinetic Energy
Vehicle Kinetic Energy
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Propulsion Categories
• Chemical Propulsion– Energy liberation limited by
chemical reaction– Limited to ~ 4000 m/sec
exhaust velocity (10,000 mph)– High-thrust, due to high mass
flow rate (1 mustang per sec)– Best for escaping near-Earth
gravity• Electric Propulsion
– Energy limited by power supply
– Higher-exhaust velocity (50,000 to 200,000 mph)
– Low-thrust, due to low mass flow rate (1 paper clip every min)
– Space propulsion
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Mustang vs. PriusChemical Propulsion Electric Propulsion
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Electric Propulsion Categories
Electric Propulsion
Electrothermal Electromagnetic Electrostatic
MPDsArcjet PPT Hall Thrusters Ion Thrusters
Type
Thrust Range (mN)
Specific Impulse
(sec)
Thruster Efficiency
(%) Thrust
Duration Typical Propellant
Kinetic Power per Unit Thrust
(W/mN) Resistojet (thermal) 200-300 200-350 65-90 Months NH3, N2H4, H2 0.5-6 Arcjet (thermal) 200-1000 400-1000 30-50 Months H2, N2, N2H4, NH3 2-3 Ion thruster 0.01-200 1500-5000 60-80 Months Xe, Kr, Ar 10-70 PPT 0.05-10 600-2000 10 Years Teflon 10-50 MPD 0.001-2000 2000-5000 30-50 Weeks Ar, Xe, H2, Li 100 Hall thruster 0.01-2000 1500-2000 30-50 Months Xe, Ar 100
Monopropellant rocket 30-100,000 200-250 87-97 Hours or Minutes N2H4
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Electric Propulsion in Orbit
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Deep Space Missions: the Need for Speed
1.0
0.8
0.6
0.4
0.2
0.0
mf /
mi
101 102 103 104 105 106 107
Specific Impulse, Isp (s)
AdvancedChemical
AdvancedNEP System
System
Earth to LEO (7.6 km/s)LEO to Earth Escape (3.2 km/s)LEO to Mars, 40 days (85 km/s)LEO to Mars, 0.7 yr (5.7 km/s)Jupiter Icy Moons Orbiter (50 km/s)LEO to Alpha Centauri (30,000 km/s)g
cgm
TIsp =≡&
cU
o
f eMM Δ−
=
fpo MMM +=
∫=t
TdtI0
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PART II:State-of-the-Art Ion Thruster
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What is Plasma? What is it good for?
• Ionized Gas• Gas of free charged
particles; electrons and ions
• High temperatures remove electrons from atoms
• Plasma can exert forces (E&M, pressure, etc.)
• Plasma can be manipulated using electric and magnetic fields
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Ion Thruster Physics
• How an Ion Thruster Works1) Hollow cathode
creates/emits electrons
2) Electrons collide with xenon atoms to create plasma
3) Plasma ions expelled at high velocity
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NASA Ion Thrusters
• NSTAR – 30 cm diameter– NASA design– Manufactured by Boeing
(now L3-communications)– 2 kW, Xenon propellant, 100
mN, 3500 sec– Deep-space One (1998 -2001,
comet Borelly)– DAWN (2007 – 2015, Vesta,
Ceres 2011 – 2012)• NEXT – 40 cm diameter
– NASA design– Manufactured by Aerojet– 8 kW, Xenon propellant, 350
mN, 4500 sec– Completed almost 2 yrs of life
testing
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Why does the cathode erode?
Cathode after approximately 3.5 years of operation inside an ion thruster
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NSTAR Ion Thruster
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Experiment
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Results
TH8
TH15
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Trajectory & Erosion Simulation
DCA Keeper
Impacting Ion Trajectories
near-DCA Electric Field Structure
40 60 80 1000
0.5
1
1.5
Radial Location (% Keeper Radius)Er
osio
n (N
o. o
f Spu
ttere
d A
tom
s) Cold Ion ProfileWarm Ion Profile
• Near-Cathode potential structure focuses ions into Cathode• Ions have enough energy to cause sputtering erosion• Over time, this leads to destruction of the cathode • And eventually termination of engine operation
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PART III:The FUTURE!
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How much POWER!?
212
P mv= &
12 spP TI g=
• Fixed Power• Specific impulse
decreases with increasing thrust!
0.001
0.01
0.1
1
10
100
1000
Thru
st (N
)
1032 3 4 5 6 7
1042 3 4 5 6 7
105
Specific Impulse (sec)
1 kW
1 MW
HET Ion10 kW
100 kW
0.1 kW
Plasmoid Thruster
10 MW
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Scale-up Ion Thrusters?
• Increased Power requires Increased Size
• Size correlates with Weight
• Need:– Increased Power
Density– Increased Thrust
Density– Increased Plasma
Density
0
10
20
30
40
50
0 20 40 60 80Thruster Diameter (cm)
Pow
er L
evel
(kW
)
Max Possible Poweri
NSTARXIPS
SERTII
NEXT
NEXIS
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Missouri Plasmoid Experiment (MPX)
• Aid the development of future Plasmoid Propulsion devices
• Study – Formation processes– Energy conversion– Loss mechanisms– Instabilities
• How?– MPX, a cylindrical pulsed
inductive plasmoid test article– High-speed probes and
spectroscopy– Advanced MHD and
collisional-radiative modeling
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Summary
I. Rocket Propulsion Basics– Chemical vs. Electric = Mustang vs. Prius– Electric Propulsion is FLYING NOW!
II. State-of-the-Art Deep Space Propulsion– Ion Thrusters are the State-of-the-Art for Deep
Space propulsion– NASA DAWN mission thrusters are on NOW!
III. The FUTURE!– Higher Power, Higher Thrust, Higher Exhaust
Velocity– Pulsed Inductive Thrusters?
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QUESTIONS?
Aerospace Plasma Laboratoryhttp://campus.mst.edu/aplabProf. Joshua Rovey112 Toomey [email protected]