The highest specific impulse chemical rockets use liquid propellants. This type of propellent has a long history going back to the first rockets and is still in use in for example the Space Shuttle and Ariane 5. Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... A Soyuz rocket, at Baikanur launch pad. ... NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ... Ariane 5 mock-up Ariane 5 is a European expendable launch system designed to deliver satellites into geostationary transfer orbit and to send payloads to Low Earth orbit. ...

History

Early development

On March 16, 1926, Robert H. Goddard used liquid oxygen and gasoline as propellants for his first successful liquid rocket launch. Both are readily available, cheap, highly energetic, and dense. Oxygen is a moderate cryogen — air will not liquify against a liquid oxygen tank, so it is possible to store LOX briefly in a rocket without heroic insulation measures. Gasoline has since been replaced by RP-1, a highly refined grade of kerosene. This combination is quite practical for rockets that need not be stored, and to this day, it is used in the first stages of most orbital launchers, as well as the long-range offensive missiles of China and North Korea. March 16 is the 75th day of the year (76th in leap years) in the Gregorian calendar. ... 1926 (MCMXXVI) was a common year starting on Friday (link will display the full calendar). ... Robert Hutchings Goddard (1882-1945) Robert Hutchings Goddard (October 5, 1882 – August 10, 1945), U.S. professor and scientist, was a pioneer of controlled, liquid-fueled rocketry. ... Liquid Oxygen In Test Tube Liquid oxygen (also LOx, LOX or Lox in the aerospace and submarine industry) is the liquid form of oxygen. ... Gasoline or petrol is a petroleum-derived liquid mixture consisting mostly of hydrocarbons and enhanced with benzene or iso-octane to increase octane ratings, used as fuel in internal combustion engines. ... Rocket fuel is a propellant that reacts with an oxidizing agent to produce thrust in a rocket. ... Cryogenics is the study of very low temperatures or the production of the same, and is often confused with cryobiology, the study of the effect of low temperatures on organisms, or the study of cryopreservation. ... RP-1 (refined petroleum) is a highly refined form of kerosene similar to jet fuel, used in the United States as a rocket fuel. ... Kerosene or paraffin oil (British English, not to be confused with the waxy solid also called paraffin wax or just paraffin) is a colorless flammable hydrocarbon liquid. ... The second stage of a Minuteman III rocket A multistage (or multi-stage) rocket is, like any rocket, propelled by the recoil pressure of the burning gases it emits as it burns fuel. ... An expendable launch system is a single-use launch vehicle usually used to launch a payload into space. ... A missile (British English: miss-isle; U.S. English: missl) is, in general, a projectile—that is, something thrown or otherwise propelled. ...

1950s

During the 1950s there was a great burst of activity by propellant chemists to find high-energy liquid propellants better suited to the military. Military rockets need to sit in silos for many years, able to launch at a moment's notice. Propellants requiring continuous refrigeration, and which cause their rockets to grow ever-thicker blankets of ice, are not practical. As the military is willing to handle and use hazardous materials, a great number of dangerous chemicals were brewed up in large batches, virtually all of which were dead ends.

For instance, in the case of nitric acid, the acid itself (HNO₃) is not stable, and gives off NO₂ fumes (hence the name white fuming nitric acid). Unlike nitrous oxide (N₂O), these nitrogen dioxide fumes are extremely toxic. The addition of large amounts of dinitrogen tetroxide (N₂O₄) makes the mixture red, but keeps it from changing composition, leaving the problem that nitric acid will eat any container it is placed in, releasing gases that can build up pressure in the process. The breakthrough was the addition of a little hydrofluoric acid (HF), which forms a self-healing metal fluoride on the interior of tank walls and makes Inhibited Red Fuming Nitric Acid storable. Although the development of military propellants was treated with the greatest secrecy, the trick to inhibiting nitric acid was published shortly after its discovery in 1954 and Russian rockets with the same fuel appeared shortly afterwards, the first being the SS-1B ("Scud"). Eventually the chemists gave up stabilizing HNO₃ with N₂O₄, and just used straight N₂O₄, which is a slightly better oxidizer anyway. (In the propellant table below, note that N₂O₄ is always in equilibrium with NO₂, and so mixtures are sometimes quoted with the latter.) R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ... [1] R-phrases , S-phrases , , , , , Supplementary data page Structure and properties n, εr, etc. ... Nitrogen tetroxide (or dinitrogen tetroxide) is the chemical compound N2O4. ... Hydrofluoric acid is a solution of hydrogen fluoride in water. ... For other uses, see Scud (disambiguation). ...

Hydrogen

Many early rocket theorists believed that hydrogen would be a marvellous propellant, since it gives the highest specific impulse. As hydrogen in any state is very bulky, for flightweight vehicles it is typically stored as a deeply cryogenic liquid. This storage technique was mastered in the 1960s as part of the Saturn and Centaur upper-stage programs. Even as a liquid, hydrogen has low density, requiring large, heavy tanks and pumps, and the extreme cold requires heavy and potentially dangerous tank insulation. This extra weight reduces the mass fraction of the vehicle and offsets the specific impulse advantage. Most rockets that use hydrogen fuel use it in upper stages only, where a low thrust-to-empty-mass ratio can be tolerated and where a hydrogen stage's low total mass reduces the size of the lower stages. Those rockets that use hydrogen fuel in their lower stages, like the Space Shuttle, Delta IV, and Ariane 5, often use powerful and dense solid rocket motors at liftoff to improve their acceleration off the pad and thus reduce gravity losses early in flight. General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... The SA-9 (Saturn I Block II), the eighth Saturn I flight, lifted off on February 16, 1965. ... Model of Centaur with Surveyor as payload. ... The Space Shuttle Columbia disaster occurred on February 1, 2003, when the Space Shuttle Columbia disintegrated over Texas during re-entry into the Earths atmosphere, shortly before concluding its 28th mission, STS-107. ... NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ... It has been suggested that some sections of this article be split into a new article entitled Delta IV launches. ... Ariane 5 mock-up Ariane 5 is a European expendable launch system designed to deliver satellites into geostationary transfer orbit and to send payloads to Low Earth orbit. ...

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). The combination delivered 542 s specific impulse in a vacuum, equivalent to an exhaust velocity of 5320 m/s. The impracticality of this chemistry highlights why exotic propellants are not actually used: to make all three components liquids, the hydrogen must be kept below -252°C (just 21 K) and the lithium must be kept above 180°C (453 K). Lithium and fluorine are both extremely corrosive, lithium ignites on contact with air, fluorine ignites on contact with most fuels, and hydrogen, while not hypergolic, is an explosive hazard. Fluorine and the hydrogen fluoride (HF) in the exhaust are very toxic, which makes working around the launch pad difficult, damages the environment, and makes getting a launch license that much more difficult. The rocket exhaust is also ionized, which would interfere with radio communication with the rocket. Finally, both lithium and fluorine are expensive and rare, enough to actually matter. This combination has therefore never flown. General Name, Symbol, Number lithium, Li, 3 Chemical series alkali metals Group, Period, Block 1, 2, s Appearance silvery white/grey Atomic mass 6. ... General Name, Symbol, Number fluorine, F, 9 Chemical series halogens Group, Period, Block 17, 2, p Appearance Yellowish brown gas Atomic mass 18. ... A Tripropellant rocket is a form of spacecraft propulsion that uses two fuels and one oxidizer. ...

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

Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in a dilute solution, slightly more viscous than water. ... Hydrazine is the chemical compound with formula N2H4. ... A (usually liquid) rocket propellant that can be used by itself, without the need for a second component. ... R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ... It has been suggested that this article be split into articles entitled steam and water vapor, accessible from a disambiguation page. ...

Current use

Here are some common liquid fuel combinations in use today:

• LOX and kerosene (RP-1). Used for the lower stages of most Russian and Chinese boosters, and the first stage of the U.S. Saturn V and Atlas boosters. Very similar to Robert Goddard's first rocket.

• LOX and liquid hydrogen, used in the Space Shuttle, Energia, Ariane 5, Delta IV and the Centaur upper stage.

• Nitrogen tetroxide (N₂O₄) and hydrazine (N₂H₄). Used in military, orbital and deep space rockets, because both liquids are storable for long periods at reasonable temperatures and pressures. Often used with hydrazine.

For the moon designated Saturn V, see Rhea. ... For other uses, see Atlas (disambiguation). ... This article or section does not cite its references or sources. ...

Propellant table

JANAF thermochemical data used throughout. Calculations performed by Rocketdyne, results appear in "Modern Engineering for Design of Liquid-Propellant Rocket Engines", Huzel and Huang. Some of the units have been converted to metric, but pressures have not. These are best-possible specific impulse calculations. Standard atmosphere (symbol: atm) is a unit of pressure. ... A pressure gauge reading in PSI (red scale) and kPa (black scale) The pound-force per square inch (symbol: lbf/in²) is a non-SI unit of pressure based on avoirdupois units. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ...

Assumptions:

• adiabatic combustion
• isentropic expansion
• one-dimensional expansion
• shifting equilibrium

Definitions This article covers adiabatic processes in thermodynamics. ... An isentropic process (a combination of the Greek word iso -same- and entropy) is one during which the entropy of working fluid remains constant. ...

Definitions of some of the mixtures: Mass flow rate is the movement of mass per time. ... Bulk density a property of particulate materials. ... Lox can stand for any of several things: Lox (salmon) - a type of salmon produce LOx (oxidizer) - liquid oxygen used as oxidizer in aerospace The Lox - was a Yonkers, NY-based rap trio This is a disambiguation page — a list of articles associated with the same title. ...

• IRFNA IIIa: 83.4% HNO₃, 14% NO₂, 2% H₂O, 0.6% HF
• IRFNA IV HDA: 54.3% HNO₃, 44% NO₂, 1% H₂O, 0.7% HF
• RP-1: see MIL-P-25576C, basically kerosene (approximately C₁₀H₁₈)
• MMH: CH₃NHNH₂

RP-1 (refined petroleum) is a highly refined form of kerosene similar to jet fuel, used in the United States as a rocket fuel. ... Kerosene or paraffin oil (British English, not to be confused with the waxy solid also called paraffin wax or just paraffin) is a colorless flammable hydrocarbon liquid. ...

See also

• Cpropep-Web an online computer program to calculate propellant performance in rocket engines