Propellant feed systems • Survey of the technologies ...
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Propulsion Systems Design Principles of Space Systems Design U N I V E R S I T Y O F MARYLAND Propulsion Systems Design • Rocket engine basics • Survey of the technologies • Propellant feed systems • Propulsion systems design © 2002 David L. Akin - All rights reserved http://spacecraft.ssl.umd.edu
Transcript of Propellant feed systems • Survey of the technologies ...
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Propulsion Systems Design
• Rocket engine basics• Survey of the technologies• Propellant feed systems• Propulsion systems design
© 2002 David L. Akin - All rights reservedhttp://spacecraft.ssl.umd.edu
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Overview of the Design Process
System-level Design(based on discipline-
oriented analysis)
Vehicle-level Estimation(based on a few
parameters from prior art)
System-level Estimation(system parameters based
on prior experience)
Program Objectives ✑System Requirements
Increasing complexity
Increasing accuracy
Decreasing abilityto comprehend the “bigpicture”
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Propulsion Taxonomy
Non-ThermalThermal
Mass Expulsion Non-Mass Expulsion
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Thermal Rocket Exhaust Velocity• Exhaust velocity is
where
VT
M
p
pee=
−ℜ
−
−
21
10
0
1
γγ
γγ
M average molecular weight of exhaust≡
ℜ ≡ =°
universal gas constJoules
mole K. .8314 3
γ ≡ ≈ratio of specific heats 1 2.
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Ideal Thermal Rocket Exhaust Velocity• Ideal exhaust velocity is
• This corresponds to an ideally expandednozzle
• All thermal energy converted to kineticenergy of exhaust
• Only a function of temperature andmolecular weight!
VT
Me =−
ℜ21
0γγ
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Thermal Rocket Performance• Thrust is
• Effective exhaust velocity
• Expansion ratio
T mV p p Ae e amb e= + −( )˙
T mc c V p pA
me e ambe= ⇒ = + −( )˙
˙
A
A
p
p
p
pt
e
e e=+
+−
−
−
−
γ γγ
γ γγγ1
211
1
1
1
0
1
0
1
Ic
gsp =
0
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Nozzle Design
• Pressure ratio p0/pe=100 (1470 psi-->14.7 psi)Ae/At=11.9
• Pressure ratio p0/pe=1000 (1470 psi-->1.47 psi)Ae/At=71.6
• Difference between sea level and ideal vacuum Ve
• Isp,vacuum=455 sec --> Isp,sl=333 sec
V
V
p
pe
e ideal
e
,
= −
−
10
1γγ
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Propulsion TaxonomyMass Expulsion Non-Mass Expulsion
Non-ThermalThermal
Non-ChemicalChemical
Monopropellants Bipropellants
LiquidsSolids Hybrids Air-Breathing
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Solid Rocket Motor
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Liquid Rocket Engine
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Propulsion TaxonomyMass Expulsion Non-Mass Expulsion
Non-ThermalThermal
Non-ChemicalChemical
Monopropellants Bipropellants
LiquidsSolids Hybrids
Pressure-Fed Pump-Fed
Air-Breathing
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Liquid Propellant Feed Systems
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Pressurization System Analysis
Pg0, Vg
PL, VL
Pgf, Vg
PL, VL
Adiabatic Expansion of Pressurizing Gas
Initial Final
p V p V p Vg g g f g, ,0γ γ γ= + l l
Known quantities:
Pg,0=Initial gas pressure
Pg,f=Final gas pressure
PL=Operating pressure ofpropellant tank(s)
VL=Volume of propellant tank(s)
Solve for gas volume Vg
Space Systems Laboratory – University of Maryland
Pr
oje
ct
Dia
na
Boost Module Propellant Tanks
• Gross mass 23,000 kg– Inert mass 2300 kg– Propellant mass 20,700 kg– Mixture ratio N2O4/A50 = 1.8 (by mass)
• N2O4 tank– Mass = 13,310 kg– Density = 1450 kg/m3
– Volume = 9.177 m3 --> rsphere=1.299 m
• Aerozine 50 tank– Mass = 7390 kg– Density = 900 kg/m3
– Volume = 8.214 m3 --> rsphere=1.252 m
Space Systems Laboratory – University of Maryland
Pr
oje
ct
Dia
na
Boost Module Main Propulsion
• Total propellant volume VL = 17.39 m3
• Assume engine pressure p0 = 250 psi• Tank pressure pL = 1.25*p0 = 312 psi• Final GHe pressure pg,f = 75 psi + pL = 388 psi• Initial GHe pressure pg,0 = 4500 psi• Conversion factor 1 psi = 6892 Pa• Ratio of specific heats for He = 1.67
• Vg = 3.713 m3
• Ideal gas: T=300°K -->ρρρρ=49.7 kg/m3 (300 psi = 31.04 MPa) MHe=185.1 kg
4500 388 312 17 391 67 1 67 3 1 67psi V psi V psi mg g( ) = ( ) + ( )( ). . .
.
ρHegp M
T=
ℜ,0
0
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Propulsion TaxonomyMass Expulsion Non-Mass Expulsion
Non-ThermalThermal
Non-ChemicalChemical
Monopropellants Bipropellants
LiquidsSolids Hybrids
Pressure-Fed Pump-Fed
Air-Breathing
Nuclear
Electrical
Solar
Beamed
Cold Gas
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Nuclear Thermal Rockets• Heat propellants by
passing through nuclearreactor
• Isp limited bytemperature limits onreactor elements (~900sec for H2 propellant)
• Mass impacts of reactor,shielding
• High thrust system
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
VASIMR Engine Concept
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Propulsion TaxonomyMass Expulsion Non-Mass Expulsion
Non-ThermalThermal
Non-ChemicalChemical
Monopropellants Bipropellants
LiquidsSolids Hybrids
Pressure-Fed Pump-Fed
Nuclear
Electrical
Solar
Ion
MPD
Air-Breathing
Beamed
Cold Gas
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Ion Propulsion
• Uses electrostatic forcesto accelerate ions
• Injects electrons to keepbeam neutral
• High Isp (~3000 sec) atlow thrust (~10 N)
• Substantial mass penaltyfor electrical powergeneration
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Propulsion TaxonomyMass Expulsion Non-Mass Expulsion
Non-ThermalThermal
Non-ChemicalChemical
Monopropellants Bipropellants
LiquidsSolids Hybrids
Pressure-Fed Pump-Fed
Ion
MPDNuclear
Electrical
Solar
Air-Breathing
Solar Sail
Laser Sail
Microwave Sail
MagnetoPlasma
ED Tether
Beamed
Cold Gas
Propulsion Systems DesignPrinciples of Space Systems Design
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Solar Sails
• Sunlight reflecting off sailproduces momentumtransfer
• At 1 AU, P=1394 W/m2
• c=3x108 m/sec• T=9x10-6 N/m2
T mV mc= =2 2˙ ˙
E mc mE
cm
E
t c
P
c= ⇒ = ⇒ = =2
2 2 2
1˙
Propulsion Systems DesignPrinciples of Space Systems Design
U N I V E R S I T Y O F
MARYLAND
Propulsion TaxonomyMass Expulsion Non-Mass Expulsion
Non-ThermalThermal
Non-ChemicalChemical Solar Sail
Laser Sail
Microwave Sail
MagnetoPlasma
Monopropellants Bipropellants
LiquidsSolids Hybrids
Pressure-Fed Pump-Fed
Ion
MPDNuclear
Electrical
Solar
Air-Breathing ED Tether
Beamed
Cold Gas
