The Reaction Engines Limited LAPCAT Configuration A2 (called the LAPCAT A2) is a

design A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process or the result of that plan or specification in the form of a prototype, product, or process. The verb ''to design' ...

study for a hypersonic speed jet airliner intended to provide, long range, high capacity commercial transportation. The aircraft was designed, as part of the

European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are located primarily in Europe, Europe. The union has a total area of ...

-funded Long-Term Advanced Propulsion Concepts and Technologies (LAPCAT) programme, by the British

aerospace engineering Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is s ...

firm

Reaction Engines Limited Reaction Engines Limited is a British aerospace manufacturer based in Oxfordshire, England. History and personnel In , Reaction Engines was founded by Alan Bond (lead engineer on the British Interplanetary Society's Project Daedalus) and Ric ...

, who said it could be developed into a working aircraft within 25 years once there is market demand for it.

Development

The vehicle is intended to have about range and good subsonic and

supersonic speed Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...

fuel efficiency Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device ...

, thus avoiding the problems inherent in earlier supersonic aircraft. The top speed is projected to be Mach 5+. It calls for the use of

liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully l ...

as a fuel, which has twice the

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 is ...

kerosene Kerosene, paraffin, or lamp oil is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from el, κηρός (''keros'') meaning " wax", and was re ...

, and can be used to cool the vehicle and the air entering the engines via a precooler.

Alan Bond Alan Bond (22 April 1938 – 5 June 2015) was an English-born Australian businessman noted for his high-profile and often corrupt business dealings. These included his central role in the WA Inc scandals of the 1980s, and what was at the time ...

, managing director of Reaction Engines, said "Our work shows that it is possible technically; now it's up to the world to decide if it wants it." The developers say it would be able to fly from

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

in under five hours, compared to around a complete day of travel with normal aircraft. The cost of a ticket is intended to be roughly business class level.

Design

Capabilities

According to

, the A2 design could fly subsonically from Brussels International Airport into the

North Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe a ...

then reaching Mach 5 across the

North Pole The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth's axis of rotation meets its surface. It is called the True North Pole to distinguish from the Ma ...

and over the

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...

. The route described isn't a

great circle In mathematics, a great circle or orthodrome is the circular intersection of a sphere and a plane passing through the sphere's center point. Any arc of a great circle is a geodesic of the sphere, so that great circles in spherical geome ...

, in order to minimise the travel time while avoiding flying supersonically over land, as there are concerns the

sonic boom A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to ...

generated by travelling at supersonic speed could cause significant discomfort for people on the ground. The A2 design is much longer than conventional jets, but would be lighter than a

Boeing 747 The Boeing 747 is a large, long-range wide-body airliner designed and manufactured by Boeing Commercial Airplanes in the United States between 1968 and 2022. After introducing the 707 in October 1958, Pan Am wanted a jet times its size, ...

. It could take off and land on current airport runways. However, the A2 design does not have

window A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent mat ...

s. The heat generated by the hypersonic airflow over the body puts constraints on window design which would make them too heavy. One solution Reaction Engines has proposed is to install

flat panel display A flat-panel display (FPD) is an electronic display used to display visual content such as text or images. It is present in consumer, medical, transportation, and industrial equipment. Flat-panel displays are thin, lightweight, provide better l ...

s, showing images of the scene outside.

Engines

The Scimitar engines use related technology to the company's earlier

SABRE A sabre (French: �sabʁ or saber in American English) is a type of backsword with a curved blade associated with the light cavalry of the early modern and Napoleonic periods. Originally associated with Central European cavalry such as t ...

engine, which is intended for space launch, but here adapted for very long distance, very high speed travel. Normally, as air enters a jet engine, it is compressed by the

inlet An inlet is a (usually long and narrow) indentation of a shoreline, such as a small arm, bay, sound, fjord, lagoon or marsh, that leads to an enclosed larger body of water such as a lake, estuary, gulf or marginal sea. Overview In marine ...

, and thus heats up. It needs much more power to compress that heated air further by the engine's compressor section, which reduces the compressor's efficiency dramatically. Furthermore, this means that high-speed engines need to be made of materials that can survive extremely high

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

s. In practice, this inevitably makes the engines heavier and also reduces the amount of fuel that can be burned, to avoid melting the gas turbine section of the engine. This in turn reduces thrust at high speed. The key design feature for the Scimitar engines is the precooler, which is a

heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct conta ...

that transfers the heat from the incoming air into the hydrogen fuel. This greatly cools the air, which allows the engines to burn more fuel even at very high speed, and allows the engines to be made of lighter, but more heat susceptible, materials such as light

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductili ...

s. The engine inlet diffuser also has to slow the incoming air to subsonic speeds because if the air moved through the precooler and compressor at supersonic speeds, it would cause damage to them. The rest of the engine is described as having high-bypass (4:1)

turbofan The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the ''turbo'' portion refers to a gas turbine engine which ac ...

engine features to give it good efficiency and subsonic (quiet) exhaust velocity at low speeds. Unlike SABRE, the A2's Scimitar engine would not have rocket engine features.

Specifications (LAPCAT A2)

References

External links

* . {{Supersonic transport Hypersonic aircraft Hydrogen-powered aircraft Ramjet-powered aircraft Reaction Engines aircraft Supersonic transports Proposed aircraft of the United Kingdom Emerging technologies