ALICE is a
rocket propellant
Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemic ...
which consists of
nano-aluminum powder and
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 ...
. After mixing, the material is frozen to keep it stable. Hence, the name ALICE, for ALuminum ICE rocket propellant.
Aluminum has a stronger affinity for oxygen than most elements, which is most visible in
aluminothermic reaction
Aluminothermic reactions are exothermic chemical reactions using aluminum as the reducing agent at high temperature. The process is industrially useful for production of alloys of iron. The most prominent example is the thermite reaction between ...
s such as
thermite
Thermite () is a pyrotechnic composition of metal powder and metal oxide. When ignited by heat or chemical reaction, thermite undergoes an exothermic reduction-oxidation (redox) reaction. Most varieties are not explosive, but can create brie ...
. This allows aluminum to burn with a large release of heat in substances that one normally considers to be inert, such as carbon dioxide and water. However, aluminum combustion is normally hindered by the presence of a durable oxide layer that forms on the surface of aluminum particles, requiring significant heat to overcome. Additionally,
aluminum oxide condenses out of the exhaust stream at high temperature, leaving it (and its
heat of condensation
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 ...
) unable to contribute to expansion, unless there is another gas present to function as a working fluid. This generally has relegated aluminum's role in rocketry to that of being an additive to
solid rocket
A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants ( fuel/ oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder; they were used in warfare by the Arabs, Chinese, ...
propellants, increasing their density and combustion temperature, and stabilizing the burn.
The oxide layer in nano-aluminum powder, however, is thinner and easier to overcome than in that of larger particles. This makes the combustion of aluminum with water ice easier to ignite and sustain. Furthermore, as the aluminum consumes the oxygen, it liberates hydrogen which functions as a low molecular mass working fluid to translate the heat of combustion (and subsequently condensation) into expansion and thrust. The high density of the mixture allows for reduced tankage mass and high thrust.
The base combustion reaction is:
: 2 Al + 3 H
2O → Al
2O
3 + 3 H
2
ALICE has been proposed as a propellant well suited for in-situ production on outer space bodies such as the
moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
, as both aluminum oxide (a source of aluminum) and water are abundant resources in the universe, while the high propellant density decreases the dry mass of the rocket. Maintaining the propellant in a frozen state is relatively simple on most bodies in the solar system, while other high performance propellants often involve cryogenic fluids that can pose long-term storage problems.
See also
*
Nano-thermite
References
{{reflist
''aluminum-Ice (ALICE) Propellants for Hydrogen Generation and Propulsion'', Risha et al., 45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, August 2-5, 2009NASA, AFOSR test environmentally friendly rocket propellant, Eurekalert August 21, 2009AFOSR and NASA Launch First-Ever Test Rocket Fueled by Environmentally-Friendly, Safe aluminum-Ice Propellant*
ttp://news.discovery.com/tech/nanoaluminum-rocket-fuel.html aluminum Fuel Could Power Future Space Trips
External links
University-produced development and flight video Purdue
Purdue University is a public land-grant research university in West Lafayette, Indiana, and the flagship campus of the Purdue University system. The university was founded in 1869 after Lafayette businessman John Purdue donated land and mo ...
and
Penn State students, August 2009
Rocket propellants
Spacecraft propulsion
Monopropellants