Aerospace fuel and it’s composition

Created by : Karolis Stonys and

Andrius Račiūnas

2011 m.

Rocket propellant

There are three main types of propellants:

Solid Liquid Hybrid

Solid-fuel rocket

A solid rocket or a solid-fuel rocket is a rocket with a motor that uses solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder

A simple solid rocket motor consists of a casing, nozzle, grain (propellant charge), and igniter.

Propellant families

Black Powder (BP) Propellants Composed of charcoal (fuel), potassium

nitrate (oxidizer), and sulfur (additive), black powder is one of the oldest pyrotechnic compositions with application to rocketry

Zinc-Sulfur (ZS) Propellants

Composed of powdered zinc metal and powdered sulfur (oxidizer), ZS or "micro grain" is another pressed propellant that does not find any practical application outside of specialized amateur rocketry circles due to its poor performance (as most ZS burns outside the combustion chamber) and incredibly fast linear burn rates on the order of 2 m/s. 

"Candy" propellants

In general, candy propellants are an oxidizer (typically potassium nitrate) and a sugar fuel (typically dextrose, sorbitol, or sucrose) that are cast into shape by gently melting the propellant constituents together and pouring or packing the amorphous colloid into a mold.

Others

Double - Base (DB) Propellants Composite propellants. High - Energy Composite (HEC)

propellants. Composite Modified Double Base

propellants. Minimum-signature (smokeless)

propellants.

Advantages

Solid-fueled rockets are much easier to store and handle than liquid-fueled rockets.

Disadvantages

Solid rockets have a lower specific impulse than liquid-fueled rockets.

 If a solid rocket is used to go all the way to orbit, the payload fraction is very small.

Solid rockets can often be shut down before they run out of fuel.

Liquid rocket propellantsHydrogen

Many early rocket theorists believed that hydrogen would be a marvelous propellant, since it gives the highest specific impulse. As hydrogen in any state is very bulky, for flight weight vehicles it is typically stored as a deeply cryogenic liquid.

Lithium/fluorine

The highest specific impulse chemistry ever test-fired in a rocket engine was lithium and fluorine, with hydrogen added to improve the exhaust thermodynamics (all propellants had to be kept in their own tanks, making this a tripropellant).

Monopropellants

Hydrogen peroxide decomposes to steam and oxygen.

Hydrazine decomposes energetically to nitrogen and hydrogen, making it a fairly good monopropellant all by itself.

Nitrous oxide decomposes to nitrogen and oxygen.

Steam when externally heated gives a reasonably modest Isp of up to 190 seconds, depending on material corrosion and thermal limits.

Advantages

Liquid fueled rockets have higher specific impulse than solid rockets and are capable of being throttled, shut down, and restarted.

Some propellants, 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 the oxidizers.

Hybrid rocket

Hybrid propellant engines represent an intermediate group between solid and liquid propellant engines. One of the substances is solid, usually the fuel, while the other, usually the oxidizer, is liquid. The liquid is injected into the solid, whose fuel reservoir also serves as the combustion chamber.

Advantages

Mechanically simpler - requires only a single liquid propellant resulting in less plumbing, fewer valves, and simpler operations.

Denser fuels - fuels in the solid phase generally have higher density than those in the liquid phase.

Less explosion hazard - Propellant grain more tolerant of processing errors such as cracks.

More controllable - Start/stop/restart and throttling are all achievable with appropriate oxidizer control.

Disadvantages

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.

Low regression-rate (rate at which the solid phase recedes) fuels often drive multi-port fuel grains.

Space Shuttle external tank

A Space Shuttle External Tank (ET) is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer.

Components

Liquid oxygen tank

The LOX tank is located at the top of the ET and has an ogive shape to reduce aerodynamic drag and aero thermodynamic heating. The ogive nose section is capped by a flat removable cover plate and a nose cone. The nose cone consists of a removable conical assembly that serves as an aerodynamic fairing for the propulsion and electrical system components. The forward most element of the nose cone functions as a cast aluminium lightning rod.

Intertank

The intertank is the ET structural connection which joins both the LOX and LH2 tanks. Its primary functions are to receive and distribute all thrust loads from the SRBs and transfer loads between the tanks.

Liquid hydrogen tank

The LH2 tank is the bottom portion of the ET. The tank is constructed of four cylindrical barrel sections, a forward dome, and an aft dome. The barrel sections are joined together by five major ring frames. These ring frames receive and distribute loads.