What is the basic principle of rocket propulsion

The principle of rocket propulsion works on the 'Newton's Third Law of Motion'. It states
that for every action, there is an equal and opposite reaction'. As far as the rocket is
concerned, the engine of the rocket releases hot burning fuel in the downward direction.

The bulk density of a substance is determined by dividing the total mass of the
substance by the volume that it occupies.

liquid propellants are substances that undergo rapid combustion, producing gaseous
products.

What do you remember about the common earth storage propellants?

What do you mean by pressuring gas

How would you compare pressure feed system from pump feed system

What do you mean by zero “g” problems

What do you mean by pump feed systems?

Regenerative cooling, in the context of rocket engine design, is a configuration in which

some or all of the propellant is passed through tubes, channels, or in a jacket around
the combustion chamber or nozzle to cool the engine. This is effective because the
propellants are often cryogenic.

Mixture ratio (MR) is defined as the ratio between the mass flow rate of the oxidizer and that of
the fuel of a liquid propellant rocket engine

The TPS system used by space vehicles inhibits the conduction of heat on the interior
of the vehicle by combining an underlying layer of thermal insulation with high-
temperature resistant surface materials
A flow control valve adjusts and controls the volume flow of air within a pneumatic
system. They can often be used to adjust the speed of operation of an actuator. They
should not be confused with pressure controllers, or regulators.

Dump cooling, which is similar to regenerative cooling because the coolant flows
through small passages over the back side of the thrust chamber wall. The difference,
however, is that after cooling the thrust chamber, the coolant is discharged overboard
through openings at the aft end of the divergent nozzle. This method has limited
application because of the performance loss resulting from dumping the coolant
overboard. To date, dump cooling has not been used in an actual application.

Film cooling provides protection from excessive heat by introducing a thin film of
coolant or propellant through orifices around the injector periphery or through
manifolded orifices in the chamber wall near the injector or chamber throat region. This
method is typically used in high heat flux regions and in combination with regenerative
cooling.x

Cryogen Boiling point (1 atm) oC (oF) Critical pressure psiga

He -269(-452) 34

H2 -253(-423) 188

N2 -196(-321) 492

736
O2 -183(-297)

 Cryogenic Engine:
o A cryogenic engine/cryogenic stage is the last stage of
space launch vehicles which makes use of Cryogenics.
 Cryogenics is the study of the production and behaviour
of materials at extremely low temperatures (below -150
degree Centigrade) to lift and place heavier objects in
space.
o A cryogenic engine provides more force with each kilogram
of cryogenic propellant it uses compared to other
 propellants, such as solid and liquid propellant rocket
engines and is more efficient.
o It uses Liquid Oxygen (LOX) and Liquid Hydrogen
(LH2) as propellants which liquefy at -183 deg C and -253
deg C respectively.
 Semi Cryogenic Engine:
o Unlike a Cryogenic engine, a Semi Cryogenic engine uses
Refined kerosene instead of liquid hydrogen.
o The liquid oxygen is used as a Oxidiser.
 That’s the advantage of using a Semi Cryogenic engine
as it requires Refined Kerosene which is lighter than liquid
fuel and can be stored in a normal temperature.
o Kerosene combined with liquid oxygen provide a higher
thrust to the rocket.
o Refined Kerosene occupies less space, making it possible
to carry more propellant in a Semi Cryogenic engines fuel
compartment.
o A semi cryogenic engine is more powerful, environment
friendly and cost effective as compared to a cryogenic
engine.

What is a cryogenic propellant?

"Cryogenic propellants are rocket propellants that are stored at very low
temperatures. Cooling some common room-temperature gases allow them to be
used as high-performance rocket propellants. Typically, cryogenic propellants are
stored in a liquid state at their boiling point.

What are the benefits of using a hybrid rocket?

The hybrid rocket motor provides several distinct advantages such as simplicity,
safety, low cost and thrust throttling over both solid-propellant and liquid-
propellant motors, which make it suitable for a broad range of applications
including sounding rocket, tactical missile, launch vehicle propulsion and space ...

The advantage of a solid motor is that it can provide huge amounts of thrust, and
therefore it is often used as a booster, making a satellite launching rocket gain high initial
velocity before using higher-efficient liquid motors to gain horizontal velocity above the
densest part of the atmosphere.

Rocket Thrust. Thrust is the force which moves the rocket through the air, and through
space. Thrust is generated by the propulsion system of the rocket through the application of
Newton's third law of motion; For every action there is an equal and opposite re-action.

How would you explain the various problems involved in storage and handling of cryogenic
propellants?

Derive the general expression for the thrust produced by a chemical rocket and hence discuss
mixture ratio control.

How would you explain the pump feed and pressure feed system with a neat sketch?

Explain in detail about the different fuel feed systems employed in rocket engines with neat sketch.

How would you demonstrate the hybrid rocket system with suitable sketch

How can you describe the need for multistaging of rockets?

How would you explain the process of dump cooling and film cooling, with neat sketch.

What explanation do you have for the design of expansion nozzle with suitable diagrams.

How would you recognize the different types of chemical propellants used in rockets

What Is Meant By Cooling In Liquid Rocket?

The heat created during combustion in a rocket engine is contained within the
exhaust gases. Most of this heat is expelled along with the gas that contains it;
however, heat is transferred to the thrust chamber walls in quantities sufficient to
require attention.
Thrust chamber designs are generally categorized or identified by the hot gas wall
cooling method or the configuration of the coolant passages, where the coolant
pressure inside may be as high as 500 atmospheres. The high combustion temperatures
(2,500 to 3,600° K) and the high heat transfer rates (up to 16 kJ/cm²-s) encountered in a
combustion chamber present a formidable challenge to the designer. To meet this
challenge, several chamber cooling techniques have been utilized successfully. Selection
of the optimum cooling method for a thrust chamber depends on many considerations,
such as type of propellant, chamber pressure, available coolant pressure, combustion
chamber configuration, and combustion chamber material.

The primary objective of cooling in liquid rocket is to prevent the chamber and nozzle
walls from becoming too hot, so they will no longer be able to withstand the imposed
stresses, thus causing the chamber or nozzle wall to fail.

Methods Of Cooling In Liquid Rocket:

1. Regenerative Cooling
2. Dump Cooling
3. Film Cooling
4. Transpiration Cooling
5. Ablative Cooling
6. Radiation Cooling

2. Dump Cooling In Liquid Rocket:

Dump cooling, which is similar to regenerative cooling because the coolant flows
through small passages over the back side of the thrust chamber wall. The difference,
however, is that after cooling the thrust chamber, the coolant is discharged overboard
through openings at the aft end of the divergent nozzle. This method has limited
application because of the performance loss resulting from dumping the coolant
overboard. To date, dump cooling has not been used in an actual application.

Dump Cooling In Liquid Propellant Rocket Engines

3. Film Cooling In Liquid Rocket:
Film cooling provides protection from excessive heat by introducing a thin film of
coolant or propellant through orifices around the injector periphery or through
manifolded orifices in the chamber wall near the injector or chamber throat region. This
method is typically used in high heat flux regions and in combination with regenerative
cooling.

Film Cooling In Liquid Propellant Rocket Engines

# HYBRID ROCKET PROPULSION:

Table of Contents:
 What Is Hybrid Rocket Propulsion?
 Basic Concepts Of Hybrid Rocket Propulsion
 Advantages Of Hybrid Rocket Propulsion Compared With Liquid Rockets
 Advantages Of Hybrid Rocket Propulsion Compared With Solid Rockets
 Disadvantages Of Hybrid Rocket Propulsion
 Hybrid Rocket Propulsion Safety
What Is Hybrid Rocket Propulsion?
A hybrid rocket propulsion is a rocket propulsion system where the rocket motor
uses propellants in two different states of matter – one solid and the other
either gas or liquid.
Hybrid rockets avoid some of the disadvantages of solid rockets like the dangers
of propellant handling, while also avoiding some disadvantages of liquid rockets
like their mechanical complexity. Because it is difficult for the fuel and oxidizer to
be mixed intimately (being different states of matter), hybrid rockets tend to fail
more benignly than liquids or solids. Like liquid rocket engines, hybrid rocket
motors can be shut down easily and the thrust is throttleable.
The theoretical specific impulse (Isp) performance of hybrids is generally higher
than solid motors and lower than liquid engines. Isp as high as 400 s has been
measured in a hybrid rocket using metalized fuels. Hybrid systems are more
complex than solid ones, but they avoid significant hazards of manufacturing,
shipping and handling solid rocket motors by storing the oxidizer and the fuel
separately.
Basic Concepts Of Hybrid Rocket Propulsion:
In its simplest form a hybrid rocket consists of a pressure vessel (tank) containing
the liquid propellant, the combustion chamber containing the solid propellant, and
a valve isolating the two. When thrust is desired, a suitable ignition source is
introduced in the combustion chamber and the valve is opened. The liquid
propellant (or gas) flows into the combustion chamber where it is vaporized and
then reacted with the solid propellant. Combustion occurs in a boundary layer
diffusion flame adjacent to the surface of the solid propellant.
Generally the liquid propellant is the oxidizer and the solid propellant is the fuel
because solid oxidizers are problematic and lower performing than liquid
oxidizers. Furthermore, using a solid fuel such as Hydroxyl-Terminated
Polybutadiene (HTPB) or paraffin wax allows for the incorporation of high-energy
fuel additives such as aluminium, lithium, or metal hydrides.
Common oxidizers include gaseous or liquid oxygen or nitrous oxide. Common
fuels include polymers such as polyethylene, cross-linked rubber such as HTPB
or liquefying fuels such as paraffin wax.A hybrid rocket propulsion is a rocket
propulsion system where the rocket motor uses propellants in two different states
of matter

Advantages Of Hybrid Rocket Propulsion Compared With Liquid Rockets:

1. Mechanically simpler – requires only a single liquid propellant resulting in less
plumbing, fewer valves, and simpler operations.
2. Denser fuel – fuels in the solid phase generally have higher density than those in
the liquid phase, reducing overall system volume.
3. Metal additives – reactive metals such as aluminium, magnesium, lithium or
beryllium can be easily included in the fuel grain increasing specific impulse (Isp),
density, or both.
4. Combustion instabilities – Hybrid rockets do not typically exhibit high frequency
combustion instabilities that plague liquid rockets due to the solid fuel grain
breaking up acoustic waves that would otherwise reflect in an open liquid engine
combustion chamber.
Advantages Of Hybrid Rocket Propulsion Compared With Solid Rockets:
1. Higher theoretical Isp – Possible due to limits of known solid oxidizers
compared to often used liquid oxidizers.
2. Less explosion hazard – Propellant grain is more tolerant of processing errors
such as cracks since the burn rate is dependent on oxidizer mass flux rate.
Propellant grain cannot be ignited by stray electrical charge and is very insensitive
to auto-igniting due to heat. Hybrid rocket motors can be transported to the
launch site with the oxidizer and fuel stored separately, improving safety.
3. Fewer handling and storage issues – Ingredients in solid rockets are often
incompatible chemically and thermally. Repeated changes in temperature can
cause distortion of the grain. Antioxidants and coatings are used to keep the
grain from breaking down or decomposing.
4. More controllable – Stop/restart and throttling are all easily incorporated into
most designs. Solid rockets rarely can be shut down easily and almost never
have throttling or restart capabilities.

Disadvantages Of Hybrid Rocket Propulsion:

1. Oxidizer-to-fuel ratio shift (“O/F shift”) – with a constant oxidizer flow-rate,
the ratio of fuel production rate to oxidizer flow rate will change as a grain
regresses. This leads to off-peak operation from a chemical performance point of
view. However, for a well-designed hybrid, O/F shift has a very small impact on
performance because I_{sp} is insensitive to O/F shift near the peak.
2. Low regression-rate (rate at which the solid phase recedes) fuels often drive
multi-port fuel grains. Multi-port fuel grains have poor volumetric efficiency and,
often, structural deficiencies. High regression rate liquefying fuels developed in
the late 1990s offer a potential solution to this problem.
3. Compared with liquid-based propulsion, re-fueling a partially or totally depleted
hybrid rocket would present significant challenges, as the solid propellant cannot
simply be pumped into a fuel tank. This may or may not be an issue, depending
upon how the rocket is planned to be used.