Most commonly used Rocket
Chemical Rocket Engines
Criteria for rating Rocket performance
• Specific Impulse
• Weight of the Engine
What is Electric Propulsion (EP)??
The acceleration of gases for the purpose
of producing propulsive thrust by electric
heating, electric body forces, and/or
electric and magnetic body forces.
Specific Impulses of Various
Solid & Liquid Propellants (In use)
Best Liquid Propellants
• Electrothermal Propulsion
• Propellant is electrically heated in some chamber and then
expanded through a suitable nozzle to obtain thrust.
• Electrostatic Propulsion
• Propellant is accelerated by direct application of electrostatic
forces to ionized particles.
• Electromagnetic Propulsion
• Propellant is accelerated under the combined action of
electric and magnetic fields.
Three Subclasses of this family:(Propellant
A)Resistojets : Heat is transferred to the
propellant from some solid surface, such as
the chamber wall or a heater coil.
B) Arcjets : Propellant is heated by an electric
arc driven through it
C)Radiatively Heated Devices: Highfrequency radiation heats the flow
Chamber Temperature : 3000K , thus limiting the exhaust velocity
not exceeding more than 10km/sec. (~3500m/s)
Propellant : Catalytically decomposed hydrazine
Advantages : Low operational Voltage
Avoids complex power processing
In Use : INTEL SAT V series - 1980
Recent application : Attitude control, Orbit insertion and
deorbit of LEO satellites, including 72 satellites in the
Temperature range should be of 10,000 K to reach exhaust
speeds greater than 10,000m/s.
Effective means : Passing an electric arc directly through
Cathode Fall Region
Anode Fall Region
Telstar-4 series of GEO communication satellites – 1993
1)Difficulty of providing high power in space.
2)Lifetime limiting problems of electrode erosion.
• Scheme of a gridded ion engine with neutralization
Electric Propulsion Applications
2. Interplanetary Missions
Electric thrusters in general are about 1.5 times as
efficient as a good chemical propulsion system
A parameter called an specific impulse comes
into play here. (~20,000 s)
So why use an electric thruster? If the mission is
not time sensitive an electric propulsion system
will use less fuel, and therefore cost less to launch
into space. On average it currently costs about
$10,000 for every kilogram launched into low
Earth orbit. Therefore if time is not a crucial issue
the delay can be worth the money saved at
Presented By :
V SHYAM PRASADA RAO