Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Propulsion Systems Design• Lecture #18 - October 29, 2020 • Rocket engine basics • Survey of the technologies • Propellant feed systems • Propulsion systems design
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© 2020 David L. Akin - All rights reserved http://spacecraft.ssl.umd.edu
http://spacecraft.ssl.umd.edu
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Grading Rubric for Team Project #2• Overall design (interior/exterior views, dimensioned 3-
view, functionality in mission application) – 10 pts • Habitability design (crew accommodations, usage
allocation, galley, waste management, windows) - 10 pts
• Life support systems design (trade studies, installation in CAD design, provision of resupply) – 10 pts
• Accommodation of visiting vehicles (docking ports, hatches, cargo interfaces) – 10 pts
• EVA accommodations (airlock(s)/suitports, suit donning/doffing/recharging stations, dust remediation) – 10 pts
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Grading Rubric for Term Project #2• Logistics management (volume allocation, crew
access, ability to restock) – 10 pts • Concept of operations (How will the habitat be
used? “day in the life”… how well does it fit the mission?) – 10 pts
• Presentation quality (“telling the story”, engaging the reader, adhering to principles from class) - 10 pts
• CAD quality (details, fidelity, complexity) - 20 pts • “Above and beyond” (extra effort outside of
nominal expectations) - 10 pts extra credit
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Propulsion Taxonomy
Ion
MPD
Non-ThermalThermal
Non-ChemicalChemical
Monopropellants Bipropellants
Pressure-Fed Pump-Fed
LiquidsSolids Hybrids Air-Breathing
Solar Sail
Laser Sail
Microwave Sail
MagnetoPlasma
ED Tether
Nuclear
Electrical
Solar
Beamed
Cold Gas
Mass Expulsion Non-Mass Expulsion
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Thermal Rocket Exhaust Velocity• Exhaust velocity is
where
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ve =2γ
γ − 1ℜToM̄
1 − ( pepo )γ − 1
γ
M̄ ≡ average molecular weight of exhaust
ℜ ≡ universal gas constant = 8314.3JoulesmoleoK
γ ≡ ratio of specific heats ≈ 1.2
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Ideal Thermal Rocket Exhaust Velocity• Ideal exhaust velocity is
• This corresponds to an ideally expanded nozzle • All thermal energy converted to kinetic energy of
exhaust • Only a function of temperature and molecular
weight!
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ve,ideal =2γ
γ − 1ℜToM̄
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Thermal Rocket Performance• Thrust is
• Effective exhaust velocity
• Expansion ratio
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T = ·mve + (pe − pamb)Ae
T = ·mc ⟹ c = ve + (pe − pamb)Ae·m (Isp = cgo )
AtAe
= ( γ + 12 )1
γ − 1
( pepo )1γ γ + 1
γ − 11 − ( pepo )
γ − 1γ
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
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 vacuum Ve
• Isp,vacuum=455 sec --> Isp,sl=397 sec
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ve1ve2
=p
γ − 1γ
o − pγ − 1
γe1
pγ − 1
γo − p
γ − 1γ
e2
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Solid Rocket Motor
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From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Solid Propellant Combustion Characteristics
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Solid Grain Configurations
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Short-Grain Solid Configurations
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Advanced Grain ConfigurationsFrom G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Liquid Rocket Engine
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Liquid Propellant Feed Systems
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Space Shuttle OMS Engine
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 2001
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Turbopump Fed Liquid Rocket Engine
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Sample Pump-fed Engine Cycles
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Gas Generator Engine Schematic
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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SpaceX Merlin 1D Engines
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Falcon 9 Octoweb Engine Mount
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Staged-Combustion Engine Schematic
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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RD-180 Engine(s) (Atlas V)
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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SSME Powerhead Configuration
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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SSME Engine Cycle
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Liquid Rocket Engine Cutaway
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From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 2001
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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H-1 Engine Injector Plate
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Injector Concepts
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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TR-201 Engine (LM Descent/Delta)
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Solid Rocket Nozzle (Heat-Sink)
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Ablative Nozzle Schematic
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Active Chamber Cooling Schematic
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Boundary Layer Cooling Approaches
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Hybrid Rocket Schematic
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Hybrid Rocket Combustion
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Thrust Vector Control Approaches
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Reaction Control Systems• Thruster control of vehicle attitude and translation • “Bang-bang” control algorithms • Design goals:
– Minimize coupling (pure forces for translation; pure moments for rotation)except for pure entry vehicles
– Minimize duty cycle (use propellant as sparingly as possible)
– Meet requirements for maximum rotational and linear accelerations
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Single-Axis Equations of Motion
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⌧ = I ✓̈
⌧
It = ✓̇ + C1
at t = 0, ✓̇ = ✓̇o =)⌧
It = ✓̇ � ✓̇o
at t = 0, ✓ = ✓o =)1
2
⌧
It2 + ✓̇ot = ✓ � ✓o
1
2
⌧
It2 + ✓̇ot = ✓ + C2
1
2
⇣✓̇2 � ✓̇o
2⌘=
⌧
I(✓ � ✓o)
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Attitude Trajectories in the Phase Plane
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!3.00%
!2.00%
!1.00%
0.00%
1.00%
2.00%
3.00%
!20.00% !10.00% 0.00% 10.00% 20.00% 30.00% 40.00%
tau/I=0%
!0.001%
!0.002%
!0.003%
!0.004%
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Gemini Entry Reaction Control System
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Apollo Reaction Control System Thrusters
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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RCS Quad
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Apollo CSM RCS Assembly
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Lunar Module Reaction Control System
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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LM RCS Quad
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Viking Aeroshell RCS Thruster
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Viking RCS Thruster Schematic
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Space Shuttle Primary RCS Engine
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Monopropellant Engine Design
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Cold Gas Thruster Exhaust Velocity
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Ve =
vuut 2�� � 1
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Cold-gas Propellant Performance
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Total Impulse• Total impulse It is the total thrust-time product for
the propulsion system, with units
• To assess cold-gas systems, we can examine total impulse per unit volume of propellant storage
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It = Tt = ṁvet
t =⇢V
ṁ
It = ⇢V ve
ItV
= ⇢ve
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Performance of Cold-Gas Systems
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Self-Pressurizing Propellants (CO2)
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Self-Pressurizing Propellants (N2O)
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Density1300 kg/m3
Density625 kg/m3
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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N2O Performance Augmentation• Nominal cold-gas exhaust velocity ~600 m/sec • N2O dissociates in the presence of a heated
catalyst engine temperature ~1300°C exhaust velocity ~1800 m/sec
• NOFB (Nitrous Oxide Fuel Blend) - store premixed N2O/hydrocarbon mixture exhaust velocity >3000 m/sec
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2N2O �! 2N2 +O2
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Pressurization System Analysis
Pg0, Vg
PL, VL
Pgf, Vg
PL, VL
Adiabatic Expansion of Pressurizing Gas
Initial Final
€
pg,0Vgγ = pg, fVg
γ + plVlγ
Known quantities:
Pg,0=Initial gas pressure
Pg,f=Final gas pressure
PL=Operating pressure of propellant tank(s)
VL=Volume of propellant tank(s)
Solve for gas volume Vg
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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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
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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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 --> ρ=49.7 kg/m3 (4500 psi = 31.04 MPa) MHe=185.1 kg
€
4500 psi( )Vg1.67 = 388 psi( )Vg
1.67 + 312 psi( ) 17.39 m 3( )1.67
€
ρHe =pg,0M ℜT0
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Autogenous Pressurization• Use gaseous propellants to pressurize tanks with
liquid propellants • Heat exchanger to gasify and warm propellants,
then route back into ullage volume • Eliminates need for pressurized gases for ullage
and high-pressure storage bottles (e.g., Falcon 9 failures)
• Issue: start-up transient
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Nuclear Thermal Rockets• Heat propellants by passing
through nuclear reactor • Isp limited by temperature
limits on reactor elements (~900 sec for H2 propellant)
• Mass impacts of reactor, shielding
• High thrust system
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Electrostatic Ion Thruster
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Hall-Effect Thruster
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Ion Engine Schematic
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Ion Engines Existing/In Development• NSTAR (NASA Solar Technology Application
Readiness) – DS1 and Dawn – 30 cm, 2.3 kW, 92 mN, 3120 sec
• NEXT (NASA Evolutionary Xenon Thruster) – Available 2019 – 6.9 kW power, 236 mN thrust, Isp 4190 sec
• HiPEP (High Power Electric Propulsion) – TRL 3 – 670 mN, 39.3 kW, 7 mg/sec prop, Isp 9620 sec
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Variable Specific Impulse Magnetoplasma
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By Source (WP:NFCC#4), Fair use, https://en.wikipedia.org/w/index.php?curid=35831241
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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VASIMR Engine Concept
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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VASIMR Operating Specifications• Optimum operating point
– Isp 5000 sec – Thrust 5.7 N – Power 200 kW
• Can be derated for higher thrust at lower Isp • Compare to ion engines at equivalent power
– 87 NSTAR thrusters: 8 N, 3120 sec Isp – 29 NEXT thrusters: 6.8 N, 4190 sec Isp – 5 HiPEP thrusters: 3.4 N, 9620 sec Isp
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Solar Sails• Sunlight reflecting off sail
produces momentum transfer
• At 1 AU, P=1394 W/m2 • c=3x108 m/sec • T=9x10-6 N/m2
€
T = 2 ˙ m V = 2 ˙ m c
€
E = mc2 ⇒ m = Ec 2
⇒ ˙ m = Et
1c2
=Pc 2
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Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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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
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