Aestus is a

hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. The ...

liquid Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...

rocket engine A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed Jet (fluid), jet of high-temperature gas produced by the combustion of rocket propellants stor ...

used on an

upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...

Ariane 5 Ariane 5 is a retired European heavy-lift space launch vehicle operated by Arianespace for the European Space Agency (ESA). It was launched from the Guiana Space Centre (CSG) in French Guiana. It was used to deliver payloads into geostationar ...

family rockets for the orbital insertion. It features unique design of 132 coaxial injection elements causing swirl mixing of the MMH propellants with

nitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

oxidizer. The

pressure-fed engine 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 ...

allows for multiple re-ignitions.

Operations

Fuel and oxidizer are stored in two aluminium alloy tanks, fuel tank is spherical while oxidizer tank is enlarged due to different volumes required from engine operations. Before engine is started it is purged with helium and fuel is pressurized. Then oxidizer valve is opened in a center of injector followed by fuel injectors arranged on a chamber wall. Hypergolic propellants spontaneously ignite on contact expanding to supersonic velocities and escaping through cooled nozzle extension.

History

Aestus was developed by the Ottobrunn Space Propulsion Centre between 1988 and 1995 with first flight as an upper stage of

G flight 502 and performed as designed. The first improvements were developed between 1999 and 2002 improving the frame performance and adjusting propellant mixture ratio from 2.05 to 1.90 with a first flight on an Ariane 5 flight 518 on 26 February 2004. Ignition qualification programme preparing engine for handling new

Automated Transfer Vehicle The Automated Transfer Vehicle, originally Ariane Transfer Vehicle or ATV, was an expendable automated cargo spacecraft, cargo spacecraft developed by the European Space Agency (ESA), used for space cargo transport in 2008–2015. The ATV desi ...

that requires 3 ignitions per flight was completed in 2007 and flew with

Jules Verne ATV The ''Jules Verne'' ATV, or Automated Transfer Vehicle 1 (ATV-1), was a robotic cargo spacecraft launched by the European Space Agency (ESA). The ATV was named after the 19th-century French science-fiction author Jules Verne. It was launched on ...

on Ariane 5 flight 528.

Aestus II / RS-72

Aestus II (also known as ''RS-72'') was a

turbopump A turbopump is a fluid pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The most co ...

-fed version of the pressure-fed Aestus developed in a collaboration between the Ottobrunn Space Propulsion Centre and

Pratt & Whitney Rocketdyne Pratt & Whitney Rocketdyne (PWR) was an American company that designed and produced rocket engines that use liquid rocket propellants, liquid propellants. It was a division of Pratt & Whitney, a fully owned subsidiary of United Technologies Corpo ...

(

Boeing The Boeing Company, or simply Boeing (), is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, and missiles worldwide. The company also provides leasing and product support s ...

Rocketdyne Rocketdyne is an American rocket engine design and production company headquartered in Canoga Park, California, Canoga Park, in the western San Fernando Valley of suburban Los Angeles, California, Los Angeles, in southern California. Rocketdyne ...

at the time). It was designed for improved performance, thrust and reliability over its predecessor. Aestus II development was supported by

which provided turbopump for the engine. The first prototype variant, called RS-72 Pathfinder, successfully completed 14 tests at the

White Sands Test Facility White Sands Test Facility (WSTF) is a NASA rocket engine test facility and a resource for testing and evaluating potentially hazardous materials, space flight components, and rocket propulsion systems. NASA established WSTF on the White Sands M ...

, reaching a 60 second burn time at 100% power in May 2000.

References

{{Ariane Rocket engines using hypergolic propellant Spacecraft propulsion Rocket engines using the pressure-fed cycle