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->A liquid propellant rocket OR liquid rocket is a rocket with a rocket engine that uses liquid propellants.
->Liquids are desirable as they have a reasonably high density and high specific impulse.
->Liquid rockets can be monopropellant rockets using a single type of propellant or bipropellant rockets using two types of propellant.

Advantages:
->Liquid-fueled rockets have higher specific impulse than solid rockets and are capable of being throttled<shut down, and restarted.
->Only the combustion chamber of a liquid-fueled rocket needs to withstand high combustion pressures and temperatures.
->Cooling can be done regeneratively with the liquid propellant
->On vehicles employing turbopumps, the propellant tanks are at a lower pressure than the combustion chamber,decrasing tank mass.
->The primary specific impulse advantage of liquid propellants is due to availablility of high-performance oxidizers.
->Some gases,notably oxygen and nitrogen, may be able to be collected from the upper atmosphere,and transferred up to low earth orbit for use in propellant depots at substantially reduced cost.
Disadvantages:
->The main difficulties with liquid propellants are also with oxidizers.
->Storable oxidizers,such as nitric acid and nitrogen tetroxide,tend to be extremely toxic and highly reactive,while cryogenic propellants by definition must be stored at low temperature and can also have reactivity/toxicity issues.
->Liquid-fueled rockets require potentially troublesome valves, seals, and turbopumps, which increase the cost o)f the launch vehicle.
->Turbopumps are particularly troublesome due to  high performance requirements.
Propellant Density:
->Although liquid hydrogen gives a high specific impulse,its low density is a disadvantage:hydrogen occupies about 7 times more volume per kilogram than dense fuels such as kerosene.
->The fuel's tankage,plumbing, and pump must be corresponding larger.
->This increases the vehicle's dry mass, reducing performance.

-Pavan Varadarajan (110239)

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A liquid-propellant rocket or liquid rocket is a rocket engine that uses liquid propellants. Liquids are desirable because their reasonably high density allows the volume of the propellant tanks to be relatively low, and it is possible to use lightweight centrifugal turbopumps to pump the propellant from the tanks into the combustion chamber, which means that the propellants can be kept under low pressure.

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A hybrid rocket usually has a solid fuel and a liquid or gas oxidizer. The fluid oxidizer can make it possible to throttle and restart the motor just like a liquid-fueled rocket. Hybrid rockets are also cleaner than solid rockets because practical high-performance solid-phase oxidizers all contain chlorine, versus the more benign liquid oxygen or nitrous oxide used in hybrids. Because just one propellant is a fluid, hybrids are simpler than liquid rockets.

The primary remaining difficulty with hybrids is with mixing the propellants during the combustion process. In solid propellants, the oxidizer and fuel are mixed in a factory in carefully controlled conditions. Liquid propellants are generally mixed by the injector at the top of the combustion chamber, which directs many small swift-moving streams of fuel and oxidizer into one another. Liquid fueled rocket injector design has been studied at great length and still resists reliable performance prediction. In a hybrid motor, the mixing happens at the melting or evaporating surface of the fuel. The mixing is not a well-controlled process and generally quite a lot of propellant is left unburned, which limits the efficiency and thus the exhaust velocity of the motor. Additionally, as the burn continues, the hole down the center of the grain (the "port") widens and the mixture ratio tends to become more oxidizer rich.

There has been much less development of hybrid motors than solid and liquid motors. For military use, ease of handling and maintenance have driven the use of solid rockets. For orbital work, liquid fuels are more efficient than hybrids and most development has concentrated there. There has recently been an increase in hybrid motor development for nonmilitary suborbital work:

The Reaction Research Society (RRS), although known primarily for their work with liquid rocket propulsion, has a long history of research and development with hybrid rocket propulsion.

Several universities have recently experimented with hybrid rockets. Brigham Young University, the University of Utah and Utah State University launched a student-designed rocket called Unity IV in 1995 which burned the solid fuel hydroxy-terminated polybutadiene (HTPB) with an oxidizer of gaseous oxygen, and in 2003 launched a larger version which burned HTPB with nitrous oxide.

Portland State University also launched several hybrid rockets in the early 2000s.

Scaled Composites SpaceShipOne, the first private manned spacecraft, is powered by a hybrid rocket burning HTPB with nitrous oxide. The hybrid rocket engine was manufactured by SpaceDev. SpaceDev partially based its motors on experimental data collected from the testing of AMROC's (American Rocket Company) motors at NASA's Stennis Space Center's E1 test stand. Motors ranging from as small as 1000 lbf (4.4 kN) to as large as 250,000 lbf (1.1 MN) thrust were successfully tested. SpaceDev purchased AMROCs assets after the company was shut down for lack of funding.

Done by YATEE 110232

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A cryogenic engine uses a cryogenic fuel or oxidizer (or both) liquefied, which is stored at very low temperatures

Cryogenics is the study of the production and behavior of materials at extremely low temperatures (below -150 degree Centigrade) to lift and place the heavier objects in space.

The United States, Russia, Japan, India, France and China are the only countries that have operational cryogenic rocket engines.

A Cryogenic rocket stage is more efficient and provides more thrust for every kilogram of propellant it burns compared to solid and earth-storable liquid propellant rocket stages.

The cost of building cryogenic and semi-cryogenic engines  is estimated to be Rs 208 crores

-V.Venu 100240

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WORKING OF A CRYOGENIC PROPELLANT IN A ROCKET

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110233 Aayushi

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For rocket engines to produce practical thrust, substantial mass flows of both the oxidizer and fuel are required.

With far higher performance than traditional propellants, cryogenic propellants enable missions with greater range and payload by significantly increasing specific impulse, or the amount of thrust provided per unit mass of rocket fuel.

In their natural state, gases are highly flammable liquids that are chilled to subfreezing temperatures and condensed into cryogenic propellants.
Future, long-term human exploration missions beyond low-Earth orbit will require high-energy propulsion options, which these liquids offer.

Cryogenic propellants are difficult to store for extended periods of time due to their low temperatures. They are less ideal for use in military rockets that must be kept launch-ready for extended periods of time due to this.

Liquid oxygen (LO2 or LOX) is most usually utilised as the oxidizer and liquid hydrogen (LH2) as the fuel.
At -253 degrees Celsius (-423 degrees Fahrenheit), hydrogen is still liquid, whereas oxygen is still liquid at -183 degrees Celsius (297 degrees Fahrenheit).

In addition, liquid hydrogen has a very low density (0.071 g/ml) compared to other fuels, necessitating a much larger storage volume.
by: Aayushi 110233

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Low-energy propellants :
Perchloryl fluoride-Available fuel
Analine-Acid

Medium-energy propellants:
Hydrazine-Acid
Ammonia-Nitrogen tetroxide

High-energy propellants:
Liquid oxygen-JP-4
Liquid oxygen-Alcohol

Very high-energy propellants:
Liquid oxygen and fluorine
Liquid oxygen-Hydrazine

Super high-energy propellants:
Fluorine-Hydrogen
Ozone-Hydrogen
Fluorine-Diborane

-R.Sri Krishna 110225

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Some rocket designs impart energy to their propellants with external energy sources. For example, water rockets use a compressed gas, typically air, to force the water reaction mass out of the rocket.

Eg Thermal Rockets
Thermal rockets use inert propellants of low molecular weight that are capable of getting heated by high temp. mechanisms
Solar Rockets concentrate solar radiations to heat the fuels.

-R.Sri Krishna 110225

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WHERE ARE HYPERGOLIC PROPELLANTS USED?
-A hypergolic propellant combination used in a rocket engine is one whose components spontaneously ignite when they come into contact with each other.
WHAT ARE THE ADVANTAGES OF HYPERGOLIC PROPELLANTS?
-Hypergolically fueled rocket engines are usually simple and reliable because they need no ignition system.
-As hypergolic rockets do not need an ignition system, they can fire any number of times by simply opening and closing the propellant valves until the propellants are exhausted
COMMON FUELS:-
-Hydrazine, Monomethylhydrazine and unsymmetrical dimethylhydrazine, and oxidizer, nitrogen tetroxide, are all liquid at ordinary temperatures and pressures. They are therefore sometimes called storable liquid propellants. They are suitable for use in spacecraft missions lasting many years.
Done By Vedanth 110231

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Liquid Propellants - 110223 Shruti Deepak.

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What are hypergolic propellants?

-A hypergolic propellant combination used in a rocket engine is one whose components spontaneously ignite when they come into contact with each other.

Components of a hypergolic propellant

-The two propellant components usually consist of a fuel and an oxidizer. The main advantages of hypergolic propellants are that they can be stored as liquids at room temperature and that engines which are powered by them are easy to ignite reliably and repeatedly. Common hypergolic propellants are difficult to handle due to their extreme toxicity and corrosiveness.

Advantages

-Hypergolic rocket engines are usually simple and reliable because they need no ignition system.

-As hypergolic rockets do not need an ignition system, they can fire any number of times by simply opening and closing the propellant valves until the propellants are exhausted and are therefore uniquely suited for spacecraft maneuvering

-Another advantage of hypergolic propellants is their high density compared to cryogenic propellants.

-Shyamcharan Bharathi 110224

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What are propellants?

Propellant, any gas, liquid, or solid the expansion of which can be used to impart motion to another substance.

Solid propellant rocket is a rocket with a rocket engine that uses solid propellants.

The earliest rockets were solid-fuel rockets powered by gunpowder; they were used in warfare by the Arabs, Chinese, Persians, Mongols, and Indians as early as the 13th century.[1]

Commonly used solid propellants:
-the most common rocket propellant has been hydrazine, a toxic compound of nitrogen and hydrogen.

-Ammonium perchlorate  is the work horse oxidizer used in modern rocket propulsion systems. The most widely used solid rocket propellant for space.

-Zinc–sulfur (ZS) propellants.
-Candy" propellants.
-Double-base (DB) propellants.
-Composite propellants.
-High-energy composite (HEC) propellants.
-Composite modified double base propellants.
-Minimum-signature (smokeless) propellants are commonly used solid propellants .

Advantages and disadvantages of solid propellants:

Advantages:
-Simple design (few or no moving parts).
-Easy to operate (little preflight checkout).
-Ready to operate quickly.Will not leak, spill, or slosh.
-Sometimes less overall weight for low total impulse application.
-Can be throttled or stopped and restarted (a few times) if preprogrammed
-Can be stored for 5 to 25 years.
-Higher overall density; this allows a more compact package, a smaller vehicle (less drag).

Disadvantages:
-Explosion and fire potential is larger; failure can be catastrophic.
- Most cannot accept bullet impact or being dropped onto a hard surface.
-Many require environmental permit and safety features for transport on public conveyances.
-Under certain conditions some propellants and grains can detonate.
-Cumulative grain damage occurs through temperature cycling or rough handling; this limits the useful life.
-If designed for reuse, it requires extensive factory rework and new propellants.
-Requires an ignition system.Each restart requires a separate ignition system and additional insulation–in practice, one or two restarts.

By B.Kailash 110236

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-> A solid propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants (fuel/oxidizer).

->The earliest rockets were solid-fuel rockets powered by gunpowder; they were used in warfare by the Arabs, Chinese, Persians, Mongols and Indians as early as the 13th century.

Uses of Solid Propellants:

# Solid rockets are still used today in military armaments worldwide, model rockets, solid rocket boosters and on larger applications for their simplicity and reliability.

# Solids are, however, frequently used as strap-on boosters to increase payload capacity or as spin-stabilized add-on upper stages when higher-than-normal velocities are required.

# Solid rockets are used as light launch vehicles for Low Earth Orbit (LEO) payloads under 2 tons or escape payloads up to 500 kilograms (1,100 lb).

- Shruthi 110222

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Rocket engines need high mass flow rates of both oxidizer and fuel to generate useful thrust.

cryogenic propellants dramatically increase specific impulse, or the amount of thrust delivered per unit mass of rocket fuel, providing much higher performance than conventional propellants and permitting longer-range, higher-payload missions.

Cryogenic propellants are gasses under normal conditions that are chilled to subfreezing temperatures and condensed to form highly combustible liquids. These liquids provide high-energy propulsion solutions critical to future, long-term human exploration missions beyond low-Earth orbit.

-C S Sriraksha 110226

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Liquid propellants used in rocketry can be classified into 3 types: Petroleum, Cryogenic and Hypergolic

PETROLEUM:

• Petroleum fuels are those refined from crude oil and are a mixture of complex hydrocarbons
• Petroleum fuels are usually used in combination with liquid oxygen as the oxidizer.
• The petroleum used as rocket fuel is a type of highly refined kerosene, called RP-1 in the United States.
• Kerosene delivers a specific impulse considerably less than cryogenic fuels, but it is generally better than hypergolic propellants

CRYOGENIC PROPELLANTS:

• Liquefied gases stored at very low temperatures
• Most frequently liquid hydrogen (LH₂) is used as the fuel and liquid oxygen (LO₂ or LOX) as the oxidizer.
• Hydrogen remains liquid at temperatures of -253 oC (-423oF) and oxygen remains in a liquid state at temperatures of -183oC (-297oF).
• 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 that must be kept launch ready for months at a time.
• Furthermore, liquid hydrogen has a very low density (0.071 g/ml) and, therefore, requires a storage volume many times greater than other fuels.

HYPERGOLIC PROPELLANTS:

• Fuels and oxidizers that ignite spontaneously on contact with each other and require no ignition source.
• The easy start and restart capability of hypergols make them ideal for spacecraft maneuvering systems.
• Hypergols remain liquid at normal temperatures, they do not pose the storage problems of cryogenic propellants. Hypergols are highly toxic and must be handled with extreme care.
• Hypergolic fuels commonly include hydrazine, monomethyl hydrazine (MMH) and unsymmetrical dimethyl hydrazine (UDMH). Hydrazine gives the best performance as a rocket fuel, but it has a high freezing point and is too unstable for use as a coolant.

by-Shreeya (110221)