Prepared under
QIP-CD Cell Project
Lecture - 28
Jet Propulsion
Ujjwal K Saha, Ph. D.
Department of Mechanical Engineering
Indian Institute of Technology Guwahati
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Liquid Propellant Rockets-Space
‰
Jet velocity: 2000 - 3500m/s.
‰
Highest thrust, can be throttled.
‰
Long sustained flight (5mins+).
Ariane 5
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Liquid Propellant Rocket for GW
• Jet velocity: 2000-3500 m/s.
• Highest thrust/weight, can be throttled.
• Short and medium range (< 50 km).
• Low signature plume.
Lance
3
Basic Operating Features
• Fuel and oxidant tanked separately and delivered to
combustion chamber at specific rates and pressures.
• Propellant flowrates (and hence thrust) variable upon
demand.
• Disadvantages compared with solid propellant rockets:
– increased complication;
– Storage problems (usually LOX & LH2 which must be
maintained at very low temperatures);
– more costly;
– reduced reliability.
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Primary Propulsion
Auxiliary Propulsion
Impart high velocity to propel a
vehicle along its flight path.
Attitude
control,
trajectory
corrections, space maneuvers.
Booster and Upper stages of
launch vehicles and large
missiles - (Boost Propulsion).
Propulsion)
Spacecrafts, Satellites,
Space rendevous – (Reaction
Control Systems).
Systems)
F=4500 N to 8 x 106 N; High
Specific Impulse.
F=0.001 N to 4500 N.
specific Impulse.
No.
of
Thrust
Chambers/engine = 1 to 4.
No. of Thrust Chambers/engine
= 4 to 24. Firing Duration =
Chamber Pressure = 2.4 to 21
Mpa.
Chamber Pressure = 0.14 to 2.1
Mpa.
Cryogenic and Storable Liquids.
Stored Cold Gas /Liquids.
Firing Duration = 5-40 secs.
Low
0.02 secs.
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Service:
¾ Single Flight
¾ Reusable type (SSME)
¾ Restartable type (RCS)
Stage:
¾ Upper Stage
¾ Booster Stage
Feed System:
¾ Gas Pressure Feed System (RCS)
¾ Turbo-pump Feed System (BP)
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Solid/Liquid Rockets
Liquid Fuel
(pressure fed)
pressurant
Solid Fuel
Liquid Fuel (turbo
pump fed)
oxidizer
fuel
Turbo pump
Thrust
chamber
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Propellant: A propellant consists of a fuel and
an oxidizer. A fuel is a substance which burns
when combined with oxygen producing gas for
propulsion. An oxidizer is an agent that releases
oxygen for combination with a fuel. Most rocket
engines use chemical propellants, which can be
classified as liquid propellants, solid propellants,
gelled propellants, hybrid propellants, or
gaseous propellants depending on their physical
state.
Liquid propellants can be further subdivided into
bipropellants and monopropellants. In an ion
propulsion system the propellant particles are
first ionized and then accelerated to yield a
high-speed exhaust. The gauge for rating the
efficiency of rocket propellants is specific
impulse.
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Three main categories of liquid propellants may
be distinguished:
•petroleum-based
•hypergolic
•cryogenic
Additionally, liquid propellants may be classed
as bipropellants (in which a liquid fuel and a
liquid oxidizer are stored separately) or
monopropellants.
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1. Monopropellant: Oxidizers and fuel both are in
a single substance. A monopropellant decomposes
into a hot gas when an appropriate catalyst is
introduced. It may be a mixture of several
compounds (HAN), or it may be a homogeneous
material like H2O2, N2H4.
HAN (hydroxyl ammonium nitrate): A relatively
new, synthetic, rocket fuel; chemical formula
NH2OH+NO3. It has the potential to be used both as
a liquid monopropellant and an ingredient in solid
propellants.
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2. Bipropellant: Bipropellants are commonly
used in liquid-propellant rocket engines, where
the fuel and the oxidizer are held separate prior
to combustion.
There are many examples, including RP-1 (a
kerosine-containing mixture) and liquid oxygen
(used by the Atlas family), and liquid hydrogen
and liquid oxygen (used by the Space Shuttle).
Examples
Oxidizers: LOX, H2O2
(Conc.), HNO3 (RFNA,
WFNA), N2O4.
Fuels: RP-1, LH2,
N2H4 (MMH, UDMH),
Alcohol.
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12
Fuels
Petroleum-based Propellant: A type of liquid propellant
in which the fuel is refined from crude oil and consists of a
mixture of complex hydrocarbons, i.e. organic compounds
containing only carbon and hydrogen. The petroleum used
as rocket fuel is kerosene, or a type of highly refined
kerosene known as RP-1. RP-1 is a kerosene fraction,
obtained from crude oil with a high napthene content which
is subjected to further treatment, including acid washing and
sulfur dioxide extraction.
Liquid Hydrogen: in its liquid state, used as a cryogenic
rocket fuel; hydrogen gas turns to liquid under standard
atmospheric pressure at -262.9°C. When oxidized by liquid
oxygen, liquid hydrogen delivers about 40% more thrust
per unit mass than other liquid fuels, such as kerosene.
Molecular weight: 2.016; density: 0.071 g/ml. Commonly
referred to in rocketry as LH2.
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Hydrazine (N2H4): A clear, highly toxic, nitrogen/hydrogen
compound with a fishy smell. It is used as a liquid rocket fuel,
both as a monopropellant, especially in attitude control
thrusters, and as a bipropellant. As a monopropellant in
catalytic decomposition engines, it is ignited by passing it
over a heated catalyst (alumina pellets impregnated with
iridium) that decomposes the fuel and produces ammonia,
nitrogen, and hydrogen exhaust gases. The decomposition of
hydrazine produces temperatures of about 1700°F and a
specific impulse of 230-240 seconds. As a bipropellant it is
also a hypergolic propellant used, for example, in the second
stage of the Titan family of launch vehicles in a 50%
hydrazine / 50% UDMH mixture known as Aerozine 50.
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MMH: A clear, colorless, hygroscopic liquid, with the
chemical formula CH3NHNH2, that is derived from hydrazine.
MMH is used as a hypergolic liquid rocket fuel, with nitrogen
tetroxide as an oxidizer, in the orbital maneuvering system
(OMS) and reaction control system (RCS) of the Space
Shuttle Orbiter. The specific impulse of the MMH/N2O4
combination in the Space Shuttle orbiter ranges from 260280 seconds in the RCS, to 313 seconds in the OMS. The
higher efficiency of the OMS system is attributed to higher
expansion ratios in the nozzles and higher pressures in the
combustion chambers.
UDMH: A hypergolic liquid rocket fuel derived from
hydrazine. It has the chemical formula (CH3)2NHH2. UDMH is
often used instead of, or in mixtures with, hydrazine because
it improves stability, especially at higher temperatures. UDMH
is employed by many Russian, European, and Chinese
rockets. The Titan family of launch vehicles and the second
stage of the Delta use a fuel called Aerozine 50, which is a
mixture of 50% UDMH and 50% hydrazine.
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Oxidizers
Liquid Oxygen: in its liquid state, used as the oxidizer in
many liquid-propellant rocket engines. Oxygen gas turns to
liquid under standard atmospheric pressure at -183°C.
Molecular weight: 32; density: 1.141 g/ml. Commonly
referred to in rocketry as LOX.
Nitric acid (HNO3): A commonly used oxidizer in liquidpropellant rocket engines between 1940 and 1965. It most
often took the form of RFNA (red fuming nitric acid),
containing 5-20% dissolved nitrogen dioxide. Compared to
concentrated nitric acid (also known as white fuming nitric
acid), RFNA is more energetic and more stable to store, but
produces poisonous red-brown fumes. Because nitric acid is
normally highly corrosive it can only be stored and piped by
a few materials such as stainless steel. However, the addition
of a small concentration of fluoride ions inhibits the corrosive
action and gives a form known as IRFNA (inhibited red
fuming nitric acid). Like nitrogen tetroxide, it is hypergolic
(reacts upon contact with) hydrazine, MMH and UDMH.
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Nitrogen tetroxide (N2O4): A yellow-brown liquid that is
among the most common storable oxidizers used by liquidpropellant rocket engines today. Like nitric acid, it is
hypergolic (reacts upon contact with) hydrazine, MMH
(monomethyl hydrazine), and UDMH (unsymmetrical
dimethyl hydrazine). It is used, for example, with MMH in the
Space Shuttle orbital maneuvering system. Although it can
be stored indefinitely in sealed containers, its liquid
temperature range is narrow and it is easily frozen or
vaporized.
Hydrogen Peroxide (H2O2): A highly oxidizing compound
of hydrogen and oxygen. H2O2 is colorless and caustic to the
skin. Pure hydrogen peroxide is stable, but the slightest
impurity will enhance decomposition, often violently,
liberating oxygen. Concentrated solutions of hydrogen
peroxide are highly corrosive and toxic. H2O2 is used as a
bleach and a a deodorizer. Molecular weight: 34.02 g/mol.
Hydrogen peroxide is dangerous to handle and easily
decomposes, making it difficult to store.
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3. Hypergolic Propellant: A form of liquid propellant in
which the fuel ignites spontaneously upon contact with an
oxidizer, thereby eliminating the need for an ignition
system. The easy start and restart capability of hypergolics
make them ideal for spacecraft maneuvering systems.
Also, since hypergolics remain liquid at normal
temperatures, they don't pose the storage problems of
cryogenic propellants. On the debit side, hypergolics are
highly toxic and must be handled with extreme care.
Hypergolic fuels commonly include hydrazine, monomethyl
hydrazine (MMH), and unsymmetrical dimethyl hydrazine
(UDMH). The oxidizer is typically nitrogen tetroxide (N2O4)
or nitric acid (HNO3).
4. Anergolic/Non-hypergolic Propellant A propellant in
which the liquid fuel and liquid oxidizer do not burn
spontaneously when they come into contact. Familiar
examples are: Liquid oxygen and Ethanol, WFNA and jet
engine fuel, and LOX-LH2 combination.
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5. Cryogenic Propellant: A form of liquid propellant
for rocket engines that must be kept at very low
temperatures to remain liquid. The common examples
are LH2 and LOX. Cryogenic propellants require special
insulated containers and vents to allow gas from the
evaporating liquids to escape. The liquid fuel and
oxidizer are pumped from the storage tanks to an
expansion chamber and injected into the combustion
chamber where they are mixed and ignited by a flame
or spark.
Because of the low temperatures of cryogenic propellants,
they are difficult to store over long periods of time. For this
reason, they are less desirable for use in military rockets
which must be kept launch ready for months at a time. Also,
liquid hydrogen has a very low density (0.59 pounds per
gallon) and, therefore, requires a storage volume many times
greater than other fuels. Despite these drawbacks, the high
efficiency of liquid hydrogen/liquid oxygen makes these
problems worth coping with when reaction time and
storability are not too critical. Liquid hydrogen delivers a
specific impulse about 40% higher than other rocket fuels.
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PROPERTIES OF LIQUID ROCKET PROPELLANTS
compound
chemical
formula
molecular
weight
density
melting
point
boiling
point
liquid oxygen
O2
32.00
1.141 g/ml
-218.8oC
-183.0oC
nitrogen tetroxide
N2O4
92.01
1.45 g/ml
-9.3oC
21.15oC
nitric acid
HNO3
63.01
1.55 g/ml
-41.6oC
83oC
liquid hydrogen
H2
2.016
0.071 g/ml
-259.3oC
-252.9oC
hydrazine
N2H4
32.05
1.004 g/ml
1.4oC
113.5oC
methyl hydrazine
CH3NHNH2
46.07
0.866 g/ml
-52.4oC
87.5oC
dimethyl hydrazine
(CH3)2NNH2
60.10
0.791 g/ml
-58oC
63.9oC
dodecane (kerosene)
C12H26
170.34
0.749 g/ml
-9.6oC
216.3oC
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Mono and Bipropellants
• Bipropellant Liquid - Energy from chemical reaction of
fuel and oxidizer
‰ Examples:
– LOX/kerosene (Ispv ≈ 330 seconds)
– LOX/hydrogen (Ispv ≈ 450 seconds)
– Nitrogen tetroxide/hydrazine (Ispv ≈ 320 seconds)
• Monopropellant Liquid - Energy from chemical
decomposition of a single fluid
‰
Examples:
– Hydrazine (Ispv ≈ 230 seconds)
– Hydrogen peroxide (Ispv ≈ 150 seconds)
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6. Gelled Propellant: A rocket
propellant that has additives to
make it thixotropic (dynamic
viscosity decreases with time for
which
shearing
forces
are
applied). This means it has the
consistency of jelly when at rest
but can be made to move as a
liquid through pipes, valves, and
injectors when adequate shear
stress is applied. It has got no
spillage/leakage,
no
sloshing
problems, and can be stored for
about 10 years. Experimental
rocket engines have shown gelled
propellants to be generally safer
than liquid propellants, yet be
capable of performing well.
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7. Gaseous Propellant: A working substance used in a
reaction control system. Nitrogen, argon, krypton, dry air,
and Freon-14 have all been employed in spacecraft.
7a. Cold Gas Jets: Methane, Helium, Nitrogen, Argon,
Krypton, dry air, and Freon-14 are stored under high
pressure. Specific impulse ranges from 50 – 120 secs,
with low thrust upto 10 N. Used in small Satellites/Roll
Control.
7b. Warm Gas Jets: System uses an inert gas with an
electric heater/or a monopropellant (N2H4) which is
catalytically or thermally decomposed. Gives high specific
impulse of 100-250 secs.
7c. Bipropellant System: Sometimes, a combination of
N2O4 and MMH is used. Gives specific impulse of 220-325
secs.
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Cold Gas Systems
• Cold Gas Systems: Involves the expulsion of high pressure
gas
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Some Points
‰ A good liquid propellant is one with a high specific impulse.
This implies a high combustion temperature and exhaust gases
with small molecular weights.
‰ Density of the propellant also plays an important role as a
lower density propellant requires a larger storage tank, thereby
increasing the mass of the launch vehicle.
‰ A propellant with a low storage temperature, i.e. a cryogenic,
requires thermal insulation, thus further increasing the mass of
the launcher.
‰ The toxicity of the propellant yet another consideration.
There are safety hazards in handling, transporting, and storing
highly toxic compounds.
‰ Also,
some propellants are very corrosive, however,
materials that are resistant to certain propellants have been
identified for use in rocket construction.
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Liquid Propellant Rocket Engines
can burn many fuels
‰ fuel tank AND oxidizer tank
‰ 25% more thrust than solid
‰ readily available fuel
‰ low combustion temperature
‰ controlled rate of fuel flow
‰ liquids unaffected by temp/humidity
‰ limitations
Limitations
- intricate
- corrosive
- fueling time too long for defense
- bulky - low density
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References
1.
2.
3.
4.
5.
6.
Hill, P.G., and Peterson, C.R., (1992), Mechanics
and Thermodynamics of Propulsion, Addison
Wesley.
Oates, G.C., (1988), Aerothermodynamics of Gas
Turbine and Rocket Propulsion, AIAA, New York.
M.J.L.Turner, (2000), Rocket and Spacecraft
Propulsion, Springer.
Sutton, G.P. and Biblarz, O., (2001), Rocket
Propulsion Elements, John Wiley & Sons.
Zucrow, M.J., (1958), Aircraft and Missile
Propulsion, Vol. II, John Wiley.
Barrere, M., Jaumotte, A., Veubeke, B., and
Vandenkerckhove, J., (1960), Rocket Propulsion,
Elsevier.
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