A hybrid rocket propulsion system comprises propellants of two different states of matter, the most common configuration being a rocket engine composed of a solid propellant lining a combustion chamber into which a liquid or gaseous propellant is injected so as to undergo a strong exothermic reaction to produce hot gas that is emitted through a De Laval nozzle for propulsive purposes. Diagram of a de Laval nozzle, showing approximate flow velocity increasing from green to red A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube that is pinched in the middle, making an hourglass-shape. ...

These systems are superior to solid propulsion systems in the respects of safety, throttling, restartability, and environmental cleanliness. Hybrid systems are slightly more complex than solids, but the reduction of safety, storage and transport issues may be an offsetting factor. The Space Shuttle is initially launched with the help of solid-fuel boosters A Solid rocket or a solid fuel rocket is a rocket with a motor that uses solid propellants (fuel/oxidizer). ...

In its simplest form a hybrid rocket consists of a pressurised tank full of oxidizer leading into a valve and from there into a combustion chamber lined with a fuel and on into a conventional rocket engine. To light the engine the valve is opened permitting oxidizer to reach the fuel, and an ignition source is supplied to start the combustion. The combustion burns along a hole through the long axis of the chamber called a 'port' and then out through the rocket nozzle producing thrust.

Common oxidizers include gaseous or liquid oxygen and nitrous oxide. Common fuels include ABS plastic or synthetic rubber, although many combustible substances can be made to work. Unconventional fuels such as salami, bagels, or chocolate have been used. General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ...

Hybrid safety

Generally, well designed and carefully constructed hybrids are very safe. However, ruptures could occur due to:

• pressure vessel failures- if the combustion chamber burns through, the relatively large combustion chamber could catastrophically fail.
• blow back- nitrous oxide tanks particularly have been known to blow-back and cause a monopropellent detonation (combustion instabilities are one of the main causes of this phenomenon, particularly towards the end of a burn when the tank pressure is low, ensuring sufficient pressure drop across the injectors is necessary at all times.)
• hard starts caused by an excess of oxidizer in the combustion chamber prior to ignition, particularly monopropellants like nitrous oxide.

The fuel itself is generally inert and cannot normally explode; and unlike solid rockets, cracks are safe unless material falls and blocks the nozzle, dependent on the physical properties of the material (rubberised fuel will pass through without exploding the chamber).

Propellant combinations in rocketry are sometimes given an 'explosive equivalence'. This, multiplied by the weight of propellant gives an equivalent weight of TNT that would give the same effect as a crash of the vehicle. The explosive equivalent of hybrid rockets propellant is often taken to be 0, whereas liquids are 10-20% and solids are around 100%.

Disadvantages of hybrids

The mixture control in hybrid rockets may be less accurate than either solid rockets engines or liquid fuel rocket engines. As the burn progresses, the port through the combustion chamber widens. This increases the surface area that is subject to combustion, and may increase the rate of fuel evolution. However the oxidizer can tend to blow through the ever widening port without fully reacting with the fuel. This changes the mixture ratio adversely, and most hybrids become oxidizer rich towards the end of the burn; impairing the average specific impulse. Proper design of the oxidizer feed system fuel composition and physical layout of the fuel can try to minimise these issues. The Space Shuttle is initially launched with the help of solid-fuel boosters A Solid rocket or a solid fuel rocket is a rocket with a motor that uses solid propellants (fuel/oxidizer). ... A liquid rocket engine has propellant and oxidiser in liquid form, as opposed to a solid rocket or hybrid rocket. ... The specific impulse (commonly abbreviated Isp) of a propulsion system is the impulse (change in momentum) per unit mass of propellant. ...

Organizations working on hybrids

In 1998 SpaceDev acquired all of the intellectual property, designs, and test results generated by over 200 hybrid rocket motor firings by the American Rocket Company (Amroc) over its eight year life. SpaceDev developed and produced all of the hybrid rocket motors for Paul Allen's SpaceShipOne. SpaceDev is currently developing SpaceDev Streaker, an expendable small launch vehicle, and SpaceDev Dream Chaser, capable of both suborbital and orbital human space flight. Both Streaker and Dream Chaser use hybrid rocket motors that burn nitrous oxide (N2O) and synthetic rubber (HTPB). SpaceDev's SpaceShipOne rocket motor was the largest of its kind ever produced. SpaceDev is an innovative publicly traded space development company in the aerospace industry, now most prominent for its spaceflight and microsatellite work. ... Founded in 1985 by George Koopman, Bevin McKinney and Jim Bennett, the American Rocket Company, or AMROC, was a company that developed hybrid rocket motors. ... SpaceShipOne is small, having a three-person cabin and short but wide wings. ... The SpaceDev Dream Chaser is a planned crewed suborbital spacecraft being developed by SpaceDev and NASA. The project was publicly announced on September 20, 2004, and may fly in 2008. ...

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. Based in the Southern California desert, the Reaction Research Society is the oldest continuously operating amateur experimental rocket group in the United States. ...

Several universities have recently experimented with hybrid rockets. BYU, the University of Utah, and Utah State University launched a student-designed rocket called Unity IV in 1995 which burned the solid fuel hydroxyl-terminated polybutadiene (HTPB) with an oxidizer of gaseous oxygen, and in 2003 launched a larger version which burned HTPB with nitrous oxide. Stanford University researches LOX/paraffin hybrid motors. Many other universities, such as the University of Arkansas at Little Rock, the University of Illinois, and Portland State University have hybrid motor test stands that allow for student research with hybrid rockets. Brigham Young University, often referred to as BYU, is the flagship university of The Church of Jesus Christ of Latter-day Saints (LDS Church). ... The University of Utah (also The U or the U of U or the UU) is a public university in Salt Lake City, Utah. ... Utah State Universitys main campus is located in Logan, Utah. ... 1995 (MCMXCV) was a common year starting on Sunday of the Gregorian calendar. ... Hydroxyl-terminated polybutadiene (HTPB) is a polymer of butadiene terminated at each end with a hydroxyl functional group. ... R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ... The Leland Stanford Junior University, commonly known as Stanford University (or simply Stanford), is a private university located approximately 37 miles (60 kilometers) southeast of San Francisco and approximately 20 miles northwest of San José in an unincorporated part of Santa Clara County. ... 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. ... Paraffin is a common name for a group of alkane hydrocarbons with the general formula CnH2n+2, where n is greater than about 20, discovered by Carl Reichenbach. ... Dickinson Hall University of Arkansas at Little Rock is the third largest university, by enrollment, in Arkansas. ... The University of Illinois is the set of three public universities in Illinois. ... Portland State University Portland State University (or PSU) is a public state urban university located in downtown Portland, Oregon. ...

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 (4.5 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 due to lack of funding. SpaceShipOne is small, having a three-person cabin and short but wide wings. ... SpaceDev is an innovative publicly traded space development company in the aerospace industry, now most prominent for its spaceflight and microsatellite work. ... Founded in 1985 by George Koopman, Bevin McKinney and Jim Bennett, the American Rocket Company, or AMROC, was a company that developed hybrid rocket motors. ... The John C. Stennis Space Center (or SSC), located in Hancock County, Mississippi at the Mississippi/Louisiana border, is NASAs largest rocket engine test facility. ...

There are a number of hybrid rocket motor systems available for amateur/hobbyist use in high-powered model rocketry. These include the popular HyperTek systems and a number of 'Urbanski-Colburn Valved' (U/C) systems such as RATTWorks, Skyripper Systems,West Coast HybridsandPropulsion Polymers. Recently Contrail Rockets have introduced a hybrid motor system offering thrust equal or greater to equivalently sized solid rocket motors, though the mass fraction is less than contemporary solid motors of equal thrust. The highest thrust High Power Rocket motor available is the Contrail Rockets O-6300.

All of these systems use nitrous oxide as the oxidizer and a plastic fuel (such as PVC or PolyPropylene) or a polymer based fuel such as HTPB. This reduces the cost per flight compared to solid rocket motors, although there is generally more 'GSE' (ground support equipment) required with hybrids. R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ...

These motors vary from 'G-class' (up to 160 Ns) to 'O-class' (up to 40960 Ns) with thrust ranging from 60N to over 6300N, and can propel a suitable rocket to altitudes of up to 30,000ft.

At the July 17, 2006 meeting of the Canadian Space Society [1], a hybrid rocket motor using gaseous oxygen and acrylic was demonstrated. The motor was built by Robert Gissing, Daniel Faber, and Luke Stras as part of a CSS space display for the Toronto Aerospace Museum. The usage of an optical grade acrylic rod as both the fuel and the combustion chamber allows for viewing of the combustion process during firing. A video of a static test firing is available at www.css.ca/meetings July 17 is the 198th day (199th in leap years) of the year in the Gregorian calendar, with 167 days remaining. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... The Canadian Space Society (CSS) is a federally-incorporated non-profit Canadian corporation. ...

See also

• Spacecraft propulsion
• Rocketry
• SpaceDev
• Scaled Composites SpaceShipOne

A remote camera captures a close-up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is used to change the velocity of spacecraft and artificial satellites, or in short, to provide delta-v. ... A rocket is a vehicle, missile or aircraft which obtains thrust by the reaction to the ejection of fast moving exhaust from within a rocket engine. ... SpaceDev is an innovative publicly traded space development company in the aerospace industry, now most prominent for its spaceflight and microsatellite work. ... Scaled Composites SpaceShipOne SpaceShipOnes patch The Scaled Composites Model 316 SpaceShipOne is an experimental air-launched suborbital spaceplane that uses a hybrid rocket motor. ...

External links

• Aspirespace Introduction to hybrid design
• Portland State Aerospace Society paraffin hybrid links
• Hybridrocket, Private Page