The word ‘cryogenics’ is derived from Greek,
meaning “production of freezing cold”.
cryogenics is the study of the production and
behaviour of materials at very
low temperatures (below −150 °C, −238 °F or 123 K).
Rather than the relative temperature scales of
Celsius and Fahrenheit, cryogenicists use the
absolute temperature scales. These are Kelvin (SI
units) or Rankine scale (Imperial and US units).
Oxygen liquifies at -183c(90k)
Hydrogen liquifies at -253c(20k)
A cryogenic engine is a rocket engine that uses
a cryogenic fuel .
Cryogenic fuels are fuels that require storage at
extremely low temperatures in order to maintain
them in a liquid state.
Various cryogenic fuel-oxidizer combinations have
been tried, but the combination of liquid hydrogen
(LH2) fuel and the liquid oxygen (LOX) oxidizer is
one of the most widely used.
The basic principle driving a rocket engine are:
Newton third law of motion
Law of conservation of momentum
In principle, cryogenic rocket engine derives thrust
like all other rocket engines by accelerating an
impulse carrier to high speeds.
The chemical energy stored in the fuel is converted
into kinetic energy by burning the fuel in the thrust
chamber and subsequent expansion in the nozzle to
o American and Soviet engineers independently, all discovered
that rocket engines need high mass flow rate of both oxidizer
and fuel to generate a sufficient thrust.
o At that time oxygen and low molecular weight hydrocarbons
were used as oxidizer and fuel pair. At room temperature and
pressure, both are in gaseous state. Hypothetically, if
propellants had been stored as pressurized gases, the size and
mass of fuel tanks themselves would severely decrease rocket
o Therefore, to get the required mass flow rate, the only option
was to cool the propellants down to cryogenic temperatures
(below −150 °C, −238 °F), converting them to liquid form.
Hence, all cryogenic rocket engines are also, by definition,
either liquid-propellant rocket engines or hybrid rocket engines
The RL10 was the first
cryogenic rocket engine
to be built in the United
development of the
engine by Marshall
Center and Pratt &
Whitney began in the
1950s, with the first flight
occurring in 1961.
These engines were one
of the main factors
of NASA's success in
On 1 February 2014, this unit was renamed as Indian
Space Research Organisation (ISRO) Propulsion
Complex and was also made an autonomous
department under ISRO. The main activities carried
out at here are:
Assembly and integration of liquid engines and
Testing of liquid engines and stages
High altitude test facilities for upper stage engines
Propellant storage facilities
C E 7.5
The specifications and key characteristics of the
Operating Cycle – Staged combustion
Propellant Combination – LOX / LH2
Maximum thrust (Vacuum) – 75 kN
Operating Thrust Range (as demonstrated during
GSLV Mk2 D5 flight) – 73.55 kN to 82 kN
Chamber Pressure (Nom) – 58 bar
Engine Mixture ratio (Oxidizer/Fuel by mass) –
Engine Specific Impulse - 454 ± 3 seconds
(4.452 ± 0.029 km/s)
Engine Burn Duration (Nom) – 720 seconds
Propellant Mass – 12800 kg
Two independent regulators: thrust control and
mixture ratio control
Steering during thrust: provided by two gimbaled
C E 20
The specifications of the engine as
listed on the LPSC handouts:
Operating Cycle - Gas Generator
Propellant Combination - LOX / LH2
Thrust Nominal (Vacuum) - 200 kN
Operating Thrust Range - 180 kN to
220 kN (To be set at any fix values)
Chamber Pressure (Nom) - 6 MPa
Engine Mixture ratio (Oxidizer/Fuel by
weight) - 5.05
Engine Specific Impulse - 443 ± 3
seconds (4.344 ± 0.029 km/s)
Engine Burn Duration (Nom) - 595
Total Flow rate - 462 kg/s
Nozzle Area ratio - 100
Mass - 588 kg
The major components of a cryogenic rocket engine are:
1.The combustion chamber (thrust chamber)
2. Pyrotechnic initiator
7. cryo valves,
9.The fuel tanks, and
10. rocket engine nozzle.
High Energy per unit mass:
Propellants like oxygen and hydrogen in liquid form give
very high amounts of energy per unit mass due to which the
amount of fuel to be carried aboard the rockets decreases.
Hydrogen and oxygen are extremely clean fuels. When
they combine, they give out only water. This water is thrown out
of the nozzle in form of very hot vapour. Thus the rocket is
nothing but a high burning steam engine
Use of oxygen and hydrogen as fuels is very economical, as
liquid oxygen costs less than gasoline.
Can’t be turned off.
Once the burn starts ,
it goes on until the fuel
is used up.
The amount of fuel
and rate of burn can
be changed in flight
Fuel system is
simpler, safer and
Low efficiency Relatively high
More thrust for a
similar rocket size
must be replaced
are more easily re-
oxygen) must be
kept extremely cold
Cryogenic liquids difficult to store for longer periods
High density requires larger tanks
Highly reactive gases
Boil off rate
Zero gravity conditions
APPLICATIONS OF CRYOGENICS
Liquid nitrogen: used in cryo-therapy, as a coolant, cryonic
Nuclear magnetic resonance spectroscopy: NMR is one of the
most common methods to determine the physical and chemical
properties of atoms by detecting the radio frequency absorbed
and subsequent relaxation of nuclei in a magnetic field.
Frozen food: Cryogenic gases are used in transportation of
large masses of frozen food.
Blood banking: Certain rare blood groups are stored at low
temperatures, such as −165 °C.
And many more…..
An Indian-made cryogenically-powered rocket,
launch vehicle GSLV-D5, carrying a GSAT-14
satellite, blasts off from the Satish Dhawan Space
Centre at Sriharikota, some 110 kilometers (69
miles) north east of Chennai on January 5, 2014
(AFP Photo / STR)