Why do rockets need oxidizers

Once ignited, however, solid propellants burn continuously, limiting the number of applications. Examples of rockets using solid propellants include the first stage of military missiles, commercial rockets and the first stage boosters that are attached to both sides of the liquid-fuel tank on the space shuttle. Though attached, the two cylindrical boosters are separate units from the tank, which itself supplies the shuttle orbiters own liquid-fuel engines.

Ammonium perchlorate mixed with powdered aluminum that is held together in a rubberlike matrix is the most common solid propellant. Liquids, in particular low temperature liquids, offer the highest specific impulse values and can be started and stopped at will throughout a mission, which makes them the best candidates for space travel.

For example, liquid hydrogen and liquid oxygen have a very high specific impulse and are used for the upper or second stages of a rocket. Dense liquids such as RPsimilar to kerosene--are sometimes used for the first stage but lack the high specific impulse for use in space. Rounding out the propellant options, gaseous fuels lack density but can offer some performance and long-term storage advantages for space travel.

The specific requirements of a mission are the primary consideration for propellant selection. For example, NASAs new human launch system, designed to replace the space shuttle, will use solid propellants for the first stage, liquid hydrogen and oxygen for the second stage, and liquid propellants for the service module in order to reach the International Space Station. This propellant architecture can then evolve to support future lunar and Mars missions. These factors mean that monopropellants require larger combustion chambers.

It is much more promising and safer to use disuperoxide salts with cations not of reducing but of oxidizing nature. Such a salt may be, for example, the salt of nitronium cation and disuperoxide anion:. We have to note, however, that the technology of such salts production presents significant difficulties due to low basicity of nitronium cation. However, way is known for production of nitronium derivatives in anhydrous environments, such as acetyl nitrite, solution of benzoylnitrite in acetic anhydride, 13 as well as a solution of tetranitromethane in pyridine.

Thus, the technology for producing of the rocket fuel oxidizer based on disuperoxide includes steps:. All operations are carried out in devices carefully isolated from the environment in the absence of moisture. Having 1 ton of rubidium, it is possible to produce about tons of disuperoxide per year. This is an open access article distributed under the terms of the, which permits unrestricted use, distribution, and build upon your work non-commercially. Withdrawal Guidlines.

Publication Ethics. Withdrawal Policies Publication Ethics. Aeronautics and Aerospace Open Access Journal. Mini Review Volume 3 Issue 4. Keywords: rocket fuel, oxidants, ozone, combustion, super peroxides. Using oxidizing agents with a high Gibbs formation energy makes possible to increase rocket fuel specific impulse.

High-energy oxidizing agents can be compounds of superoxides super-peroxides. Ashless disuperoxides production in industrial quantities is technically possible.

Oskar J Haidn. Advanced Rocket Engines. Sutton GP. History of liquid propellant rocket engines in the United States. Journal of Propulsion and Power. The Dynamics of Unsteady Detonation in Ozone. Spakovszky ZS. MIT; J Phys Chem. Liquid oxygen and liquid hydrogen are used as the propellant in the high efficiency main engines of the Space Shuttle.

Another cryogenic fuel with desirable properties for space propulsion systems is liquid methane o C. Future missions to Mars will likely use methane fuel because it can be manufactured partly from Martian in-situ resources.

Liquid fluorine o C burning engines have also been developed and fired successfully. Fluorine is not only extremely toxic; it is a super-oxidizer that reacts, usually violently, with almost everything except nitrogen, the lighter noble gases, and substances that have already been fluorinated. Despite these drawbacks, fluorine produces very impressive engine performance. Because of fluorine's high toxicity, it has been largely abandoned by most space-faring nations.

Some fluorine containing compounds, such as chlorine pentafluoride, have also been considered for use as an 'oxidizer' in deep-space applications. Hypergolic propellants are 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. Also, since 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. 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. MMH is more stable and gives the best performance when freezing point is an issue, such as spacecraft propulsion applications. UDMH has the lowest freezing point and has enough thermal stability to be used in large regeneratively cooled engines. Consequently, UDMH is often used in launch vehicle applications even though it is the least efficient of the hydrazine derivatives.

Aerozine 50 is almost as stable as UDMH and provides better performance. The oxidizer is usually nitrogen tetroxide NTO or nitric acid. Nitrogen tetroxide is less corrosive than nitric acid and provides better performance, but it has a higher freezing point. Consequently, nitrogen tetroxide is usually the oxidizer of choice when freezing point is not an issue, however, the freezing point can be lowered with the introduction nitric oxide.

The resulting oxidizer is called mixed oxides of nitrogen MON. The number included in the description, e. Hydrazine is also frequently used as a monopropellant in catalytic decomposition engines.

In these engines, a liquid fuel decomposes into hot gas in the presence of a catalyst. The decomposition of hydrazine produces temperatures up to about 1, o C 2, o F and a specific impulse of about or seconds. Hydrazine decomposes to either hydrogen and nitrogen, or ammonia and nitrogen.

Other propellants have also been used, a few of which deserve mentioning: Alcohols were commonly used as fuels during the early years of rocketry. Lichens occupy some of the most extreme habitats on earth, from tropical rainforests to the Antarctic. As a group, they tend not to be very sensitive to temperature though individual species prefer certain temperature ranges , and they tolerate drought pretty well.

Some species, however, are highly sensitive to air pollutants, such as sulfur dioxide and heavy metals. Rusty Russell botanist, Natural History Museum. It's your turn to Ask Smithsonian.

Illustration by Jos. Jerry Hughes Tulsa, Oklahoma They know because you have conditioned them. Gary Graves curator of birds, Natural History Museum If there is no oxygen in space, how do rockets ignite their engines?