A steam rocket (also known as a hot water rocket) is a

thermal rocket A thermal rocket is a rocket engine that uses a propellant that is externally heated before being passed through a nozzle to produce thrust, as opposed to being internally heated by a redox (combustion) reaction as in a chemical rocket. Thermal r ...

that uses

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

held in a

pressure vessel A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. Construction methods and materials may be chosen to suit the pressure application, and will depend on the size o ...

at a high temperature, such that its

saturated vapor pressure Vapor pressure (or vapour pressure in English-speaking countries other than the US; see spelling differences) or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phase ...

is significantly greater than ambient pressure. The water is allowed to escape as

steam Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization ...

through a

rocket nozzle A rocket engine nozzle is a propelling nozzle (usually of the de Laval type) used in a rocket engine to expand and accelerate combustion products to high supersonic velocities. Simply: propellants pressurized by either pumps or high pressure u ...

to produce

thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...

. Steam rockets are usually

pressure fed The pressure-fed engine is a class of rocket engine designs. A separate gas supply, usually helium, pressurizes the propellant tanks to force fuel and oxidizer to the combustion chamber. To maintain adequate flow, the tank pressures must exceed th ...

, but more complex designs using

solar energy Solar energy is radiant light and heat from the Sun that is harnessed using a range of technologies such as solar power to generate electricity, solar thermal energy (including solar water heating), and solar architecture. It is an essenti ...

nuclear energy Nuclear energy may refer to: *Nuclear power, the use of sustained nuclear fission or nuclear fusion to generate heat and electricity * Nuclear binding energy, the energy needed to fuse or split a nucleus of an atom *Nuclear potential energy ...

have been proposed. They are probably best known for their use in rocket-powered cars and motorcycles, and they are the type used in

aeolipile An aeolipile, aeolipyle, or eolipile, from the Greek "αιολουπυλη", also known as a Hero's engine, is a simple, bladeless radial steam turbine which spins when the central water container is heated. Torque is produced by steam jets exi ...

Principle of operation

Water, while under pressure, is heated up to a high temperature (approx. 250–500 °C). As the hot water goes through the nozzle (usually a

de Laval nozzle A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube which is pinched in the middle, making a carefully balanced, asymmetric hourglass shape. It is used to accelerate a compressible fluid to supersonic speeds ...

) and the pressure reduces, the water flashes to

pressing on the nozzle, and leaving at high speed. By the recoil the rocket accelerates in the opposite direction to the steam. The nozzle of hot water rockets must be able to withstand high pressure, high temperatures and the particularly corrosive nature of hot water. The simplest design has a pressurised water tank where the water is heated before launch; however, this gives a very low exhaust velocity since the high

latent heat of vaporization The enthalpy of vaporization (symbol ), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas. T ...

means that very little actual steam is produced and the exhaust consists mostly of water, or if high temperatures and pressures are used, then the tank is very heavy. More complex designs can involve passing the water through pumps and heat exchangers and employing nuclear reactors or solar heating; it is estimated that these can give a

specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse i ...

of over 195 s I_sp, which is still well below the standards of more complex designs, for example the 465 s of the hydrogen-oxygen Vinci engine.

Applications of steam rockets

* An

is pushed around by steam rockets *

Evel Knievel Robert Craig "Evel" Knievel (; October 17, 1938 – November 30, 2007) was an American stunt performer and entertainer. Over the course of his career, he attempted more than 75 ramp-to-ramp motorcycle jumps. Knievel was inducted into the Motor ...

Skycycle X-2 The Skycycle X-2 was a steam-powered rocket owned by Evel Knievel and flown during his Snake River Canyon jump in Idaho in 1974. An earlier prototype was designed, named the Skycycle X-1, by Doug Malewicki and retired U.S. Navy engineer Robert ...

used for the Snake River Canyon jump used a steam rocket designed by

Robert Truax Captain Robert C. Truax (USN) (September 3, 1917 – September 17, 2010) was an American rocket engineer in the United States Navy, and companies such as Aerojet and Truax Engineering, which he founded. Truax was a proponent of low-cost rocket ...

Walt Arfons Walter Charles Arfons (December 10, 1916 – June 4, 2013) was the half brother of Art Arfons, his former partner in drag racing, and his competitor in jet-powered land speed record racing. Along with Art, he was a pioneer in the use of aircr ...

's "Neptune I" dragster, also used a steam rocket designed by Robert Truax * Hot water rockets are used occasionally as auxiliary launch aids and for experimentation purposes. * "Mad" Mike Hughes, American daredevil, manned and launched his steam powered rocket on March 25, 2018 to a height of 1,875 feet (572 m). He died during a later launch on the 22 February 2020. The launch event was being filmed for the Science Channel television series Homemade Astronauts, in which Hughes was to star.

Proposed uses of steam rockets

Solar or nuclear heated steam

s have been proposed for use in interplanetary travel. Although the performance is low, high mass fractions are easy to achieve, and water is expected to be very easy to extract and purify from ice deposits that are found around the solar system.Neofuel, using abundant off-earth resources for interplanetary transport
/ref>

References

{{reflist

Popular culture

Steam rockets have occasionally appeared in

science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel unive ...

stories, especially

steampunk Steampunk is a subgenre of science fiction that incorporates retrofuturistic technology and aesthetics inspired by 19th-century industrial steam-powered machinery. Steampunk works are often set in an alternative history of the Victorian era or ...

. *

Steamboy is a 2004 Japanese animated steampunk action film produced by Sunrise, directed and co-written by Katsuhiro Otomo, his second major anime release as a director, following '' Akira'' (1988). The film was released in Japan by Toho on July 17, 20 ...

Seveneves ''Seveneves'' is a hard science fiction novel by Neal Stephenson published in 2015. The story tells of the desperate efforts to preserve ''Homo sapiens'' in the wake of apocalyptic events on Earth after the unexplained disintegration of the Moo ...

External links

Steam Rockets of Tecnologia Aeroespacial Mexicana

Aquarius
Hot Water Rocket Propulsion Systems site

ordering Rockets and missiles Model rockets

Rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...