Propulsion Systems Design - Dave Akin's Web Site

35 Pages·2004·3.01 MB·English

Propulsion Systems Design
• Rocket engine basics
• Solid rocket motors
• Liquid rocket engines
• Monopropellants
• Bipropellants
• Propellant feed systems
• Hybrid rocket engines
• Auxiliary propulsion systems
U N I V E R S I T Y O F
Rocket Propulsion
MARYLAND
© 2004 David L. Akin - All rights reserved Launch and Entry Vehicle Design
http://spacecraft.ssl.umd.edu
Thermal Rocket Exhaust Velocity
• Exhaust velocity is
 
γ−1
 
 
2γ ℜT p γ
0  e 
V = 1 − 
 
e
γ −1 M   p  
0
 
where
M ≡ average molecular weight of exhaust
Joules
ℜ ≡ universal gas const.= 8314.3
mole°K
γ ≡ ratio of specific heats ≈ 1.2
U N I V E R S I T Y O F
Rocket Propulsion
MARYLAND
Launch and Entry Vehicle Design
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Ideal Thermal Rocket Exhaust Velocity
• Ideal exhaust velocity is
2γ ℜT
0
V =
e
γ −1 M
• This corresponds to an ideally expanded
nozzle
• All thermal energy converted to kinetic
energy of exhaust
• Only a function of temperature and
molecular weight!
U N I V E R S I T Y O F
Rocket Propulsion
MARYLAND
Launch and Entry Vehicle Design
€
Thermal Rocket Performance
• Thrust is
T = m˙ V + ( p − p )A
e e amb e
• Effective exhaust velocity
 
A c
T = m˙ c ⇒ c = V + ( p − p ) e  I = 
 
e e amb sp
m˙ g
 
0
• Expansion ratio
 
1 γ−1
1
   
   
A γ + 1 p γ γ + 1 p γ
γ−1
t  e   e 
=   1 − 
   
A  2   p  γ −1   p  
e 0 0
 
U N I V E R S I T Y O F
Rocket Propulsion
MARYLAND
Launch and Entry Vehicle Design
€
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Nozzle Design
Pressure ratio p /p =100 (1470 psi-->14.7 psi)
• 0 e
A /A =11.9
e t
Pressure ratio p /p =1000 (1470 psi-->1.47 psi)
• 0 e
A /A =71.6
e t
Difference between sea level and ideal vacuum V
• e
γ−1
 
V p γ
e  e 
= 1−
 
V p
 
e,ideal 0
I =455 sec --> I =333 sec
• sp,vacuum sp,sl
U N I V E R S I T Y O F
Rocket Propulsion
MARYLAND
Launch and Entry Vehicle Design
€
Solid Rocket Motor
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
U N I V E R S I T Y O F
Rocket Propulsion
MARYLAND
Launch and Entry Vehicle Design
Solid Propellant Combusion Characteristics
From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986
U N I V E R S I T Y O F
Rocket Propulsion
MARYLAND
Launch and Entry Vehicle Design
Solid Grain Configurations
From G. P. Sutton, Rocket Propulsion Elements
(5th ed.) John Wiley and Sons, 1986
U N I V E R S I T Y O F
Rocket Propulsion
MARYLAND
Launch and Entry Vehicle Design
Short-Grain Solid Configurations
From G. P. Sutton, Rocket Propulsion Elements (5th ed.)
John Wiley and Sons, 1986
U N I V E R S I T Y O F
Rocket Propulsion
MARYLAND
Launch and Entry Vehicle Design
Advanced Grain Configurations
From G. P. Sutton, Rocket Propulsion Elements
(5th ed.) John Wiley and Sons, 1986
U N I V E R S I T Y O F
Rocket Propulsion
MARYLAND
Launch and Entry Vehicle Design