MAE 5391: Rocket PropulsionOverview of Propulsion Systems

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Rocket Technologies

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Propulsion Technology Options Thermodynamic Systems (TE KE)

Cold Gas Thrusters Liquids

• Monopropellants• Bipropellants

Solids Hybrids

Nuclear (NE TE KE) Electric Systems

Electrothermal (Resistance Heating) Electrostatic (Ion with E field F=qE) Electromagnetic (plasma with B field F=JxB)

With the exception of electrostatic and electromagnetic, all use concept of gas at some temp flowing though a converging/diverging nozzle!

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Chemical Limitations

Why we have thermo!

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0

0

pp

MTRV eu

exit

Vexit= nozzle exit velocity (m/s)

Ru= universal gas constant (8314.41 J/kmol*K)T0= chamber temperature (K)Pe= exit pressure (Pa)P0= chamber pressure (Pa)M= molecular mass of gas (kg/kmol)= ratio of specific heats (no dimensions)

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Cold Gas

Gas MolecularWeight

SpecificImpulse (sec)

Air 28.9 74Argon 39.9 57CO2 44.0 67

Helium 4.0 179Hydrogen 2.0 296Nitrogen 28.0 80Methane 16.0 114

1.5 litre X 600 barNitrogen tanks

Fill/drain valve

Two stage regulator (feed pressure ~ 4bar)

Thruster (0.01N,1.3 *10-5 kg/s,throat diameter0.0133 cm)

Stop valve

Microsat cold gaspropulsion systemlayout proposal

Cold Gas: Expand a pressurized gas through a nozzle

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Liquid MonopropellantParameter Value

Catalyst LCH 227/202

Steady-state thrust (N) 11.1 - 31.2

Isp (sec) 228 - 235

Propellant specific gravity 1.023

Average Density Isp ( sec) 236.8

Rated total impulse (Nsec) 124,700

Total pulses 12,405

Minimum impulse bit (Nsec) 0.56

Feed pressure (bar) 6.7 - 24.1

Chamber pressure (bar) 4.5 - 12.4

Nozzle expansion ratio 61:1

Mass flow rate (gm/sec) 5.0 - 13.1

Valve power 27 W max @ 28 VDC

Thruster mass (kg) 0.52

3 N2H4 4 NH3 + N2 + 336,280 joules

MonoProp: Decompose a single propellant and expand the exhaust through a nozzle

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Liquid Bi-Propellant

Storable Isp 250-320 secfinert=0.03-.13

Cryogenic Isp 320 – 452 secfinert=0.09-0.2

BiProp: Combust (burn) two propellants (fuel + oxidizer) in a combustion chamber and expand exhaust through a nozzle

Finert = 0.04-0.2 Finert=0.11-0.31

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Solids Composite propellant, consisting of an

oxidizing agent, such as ammonium nitrate or ammonium perchlorate intimately mixed with an organic or metallic fuel and binder.

Thrust function of burn area, Isp = 250-300 secFinert=0.06-0.38, 2/3 of motors have fiinert below 0.2

AdvantagesSimpleReliableHigh density IspNo chamber cooling

DisadvantagesCracks=disasterCan’t restartHard to stopModest Isp

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When solids go bad!

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Hybrids

Isp= 290-350 secFinert=0.2

Hybrid: Bipropellant system with liquid oxidizer (usually) and a solid fuel

Catalyst Pack

Combustion Chamber

Nozzle

Test Stand

Load Cell

Fuel Element

H2O2/PE Hybrid Test Set-Up

Polyethylene fuel rod

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Nuclear Thermal Propulsion

NERVA Program Thrust = 890,000N Isp = 838 sec Working fluid = Hydrogen Test time = 30 minutes Stopped in 1972 Finert=0.5-0.7 (shielding)

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Electrothermal-Resistojets

Nozzle

Thermocouple tapping

Stainless steel outer1225W Cartridge heater

Water inlet

Heater thermocouple

Power inputSintered stainlesswater distribution ring

Sintered stainless filterPressure tapping

SiC Heat transfer medium

Cutaway of Mark- III Resistojet

Working Fluid

Thrust (mN) Isp (sec) Power (W) Cp (kJ/kg K) Tc (K)

hydrogen 37 546 100 14.32 1000

water 93 219 100 2.3 1000

nitrous oxide 141 144 100 1.0 1000

Electrothermal-- electrical energy is used to directly heat a working fluid. The resulting hot gas is then expanded through a converging-diverging nozzle to achieve high exhaust velocities. These systems convert thermal energy to kinetic energy

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Electrothermal-Arcjets

In an arcjet, the working gas is injected in a chamber through which an electric arc is struck. The gas is heated to very high temperature (3000 – 4000 K), Arc temp =10,000K on average, and much greater in certain regions in the arc.

Power = 1.8 kW, Isp = 502, Thrust = 0.2N, Propellant = hydrazine

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Electrostatic-Ion Propulsion Electrostatic-- electrical energy is directly converted into

kinetic energy. Electrostatic forces are applied to charged particles to accelerate the propellant.

Deep Space 1 = 4.2 kW, Thrust = 165 mN, Isp = 3800 sec7000 hours of operation is becoming the standard!

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Electromagnetic-MPD Thruster Electromagnetic-- electromagnetic forces directly

accelerate the reaction mass. This is done by the interaction of electric and magnetic fields on a highly ionised propellant plasma.

NH3 MPD, F=23 mN, Isp= 600 sec, P=430 W Stuttgart, Isp=5000sec, F=100N, P=6 MW, hydrogen

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Pulsed Plasma Thrusters

Ctrigger

CMain

Rtrigger

CenterElectrode

IntermediateElectrode

OuterElectrode

Teflon Annulus

PPUSpacecraftGround

Isp = 500-1500 secP = 1 – 100 WThrust = 5mN/W

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Hall Effect Thruster

Power = 50W – 25kWIsp = 500 – 3000 secThrust = 5 mN- 1N

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Propulsion System “Cost” Performance issues

Mass Volume Time (thrust) Power Safety Logistics Integration Technical Risk

The “best” (lowest “cost”) option optimizes these issues for a given set of mission requirements