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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 Systems Design
• Lecture #18 - October 30, 2014 • Crew Systems/PPT Systems Project • Rocket engine basics • Survey of the technologies • Propellant feed systems • Propulsion systems design
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© 2014 David L. Akin - All rights reserved 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
Notes:
• I will be posting separately (later today) details on the third team project (Crew Systems/Power, Propulsion, and Thermal Systems) and the next problem set
• From here on out, a single problem set will be issued for each of the disciplinary lecture sets (CS, PPT, LSM, AVS)
• Today at 3:30 in AVW 2116, the guest speaker in ENAE 788X will be Robert Giglio, chief rover designer for Astrobotic
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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
€
Ve =2γγ −1
ℜT0M
1− pe
p0
%
& ' '
(
) * *
γ −1γ
+
,
- - -
.
/
0 0 0
€
M ≡ average molecular weight of exhaust
€
ℜ ≡ universal gas const .= 8314.3 Joulesmole°K
€
γ ≡ ratio of specific heats ≈1.2
4
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!
€
Ve =2γγ −1
ℜT0M
5
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
€
T = ˙ m Ve + pe − pamb( )Ae
€
T = ˙ m c ⇒ c = Ve + pe − pamb( ) Ae
˙ m
€
AtAe
=γ +12
#
$ %
&
' (
1γ −1 pe
p0
#
$ % %
&
' ( (
1γ γ +1
γ −11− pe
p0
#
$ % %
&
' ( (
γ −1γ
*
+
, , ,
-
.
/ / /
€
Isp =cg0
"
# $ $
%
& ' '
6
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
A Word About Specific Impulse
• Defined as “thrust/propellant used” – English units: lbs thrust/(lbs prop/sec)=sec – Metric units: N thrust/(kg prop/sec)=m/sec
• Two ways to regard discrepancy - – “lbs” is not mass in English units - should be slugs – Isp = “thrust/weight flow rate of propellant”
• If the real intent of specific impulse is
Isp =T
mand T = mVe then Isp = Ve!!!
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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
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
€
VeVe,ideal
= 1− pep0
#
$ % %
&
' ( (
γ −1γ
8
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
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
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
U N I V E R S I T Y O FMARYLAND
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
U N I V E R S I T Y O FMARYLAND
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
U N I V E R S I T Y O FMARYLAND
Advanced 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
U N I V E R S I T Y O FMARYLAND
Liquid Rocket Engine
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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
Liquid Propellant Feed Systems
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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
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
U N I V E R S I T Y O FMARYLAND
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
U N I V E R S I T Y O FMARYLAND
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
U N I V E R S I T Y O FMARYLAND
Gas Generator Cycle 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
U N I V E R S I T Y O FMARYLAND
SSME Powerhead Configuration
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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
SSME Engine Cycle
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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
U N I V E R S I T Y O FMARYLAND
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
U N I V E R S I T Y O FMARYLAND
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
U N I V E R S I T Y O FMARYLAND
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
U N I V E R S I T Y O FMARYLAND
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
U N I V E R S I T Y O FMARYLAND
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
U N I V E R S I T Y O FMARYLAND
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 + ✓
o
t = ✓ � ✓o
1
2
⌧
It2 + ✓
o
t = ✓ + 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
35
!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
U N I V E R S I T Y O FMARYLAND
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
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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
Apollo CSM RCS Assembly
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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
Lunar Module Reaction Control System
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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
LM RCS Quad
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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
Viking Aeroshell RCS Thruster
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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
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
U N I V E R S I T Y O FMARYLAND
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
U N I V E R S I T Y O FMARYLAND
Cold Gas Thruster Exhaust Velocity
44
Ve
=
vuut 2�
� � 1
<T0
M
"1�
✓pe
po
◆ ��1�
#
Ve =
vuut 2(1.4)
1.4� 1
8314.3(300)
28
"1�
✓2
300
◆ 1.4�11.4
#= 689
m
sec
Assume nitrogen gas thrusters
M = 28
T0 = 300 K
p0 = 300 psi
pe = 2 psi
� = 1.4< = 8314.3
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
45
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Total Impulse
• Total impulse It is the total thrust-time product for the propulsion system, with units <N-sec> !!!!
• To assess cold-gas systems, we can examine total impulse per unit volume of propellant storage
46
It = Tt = mvet
t =⇢V
m
It = ⇢V ve
ItV
= ⇢ve
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
Performance of Cold-Gas Systems
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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
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)
49
Density!1300 kg/m3
Density!625 kg/m3
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
N2O Performance Augmentation
• Nominal cold-gas exhaust velocity ~600 m/sec • N2O dissociates in the presence of a heated
catalystengine temperature ~1300°C exhaust velocity ~1800 m/sec
• NOFB (Nitrous Oxide Fuel Blend) - store premixed N2O/hydrocarbon mixtureexhaust velocity >3000 m/sec
50
2N2O �! 2N2 +O2
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
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
!51
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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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
U N I V E R S I T Y O FMARYLAND
VASIMR Engine Concept
55
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
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Ion Propulsion
• Uses electrostatic forces to accelerate ions
• Injects electrons to keep beam neutral
• High Isp (~3000 sec) at low thrust (~10 N)
• Substantial mass penalty for electrical power generation
56
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
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 = E
t1c2 =
Pc 2
57
Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design
U N I V E R S I T Y O FMARYLAND
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
58
