Although much efforts are in progress to build Turbine-Based Combined Cycle engines, most of powered hypersonic vehicles are designed and built around supersonic combustion ramjets, or SCRJ. Their thermodynamic cycle is essentially a Brayton cycle where compression is dynamic rather than done by rotating machinery. As SCRJ cannot develop thrust when velocity is zero, cycles combining SCRJ with gas turbine or rockets (combined cycles) are discussed together with their specific impulse performance. Combining rocket or ramjets with air ejectors are reported among the combined cycles tested in the past for certain applications. Even more sophisticated combined cycles consisting in liquifying air during flight, such as LACE and ACES, are discussed, among them the SABRE cycle developed in the UK that employs a liquid air-fed rocket engine burning hydrogen. The major advantage of all LACE cycles stays in reducing the weight of oxidizer at take-off; charts showing the ratio between take-off gross weight and onboard oxidizer weight as a function of the speed enabled by the airbreathing engine or of the oxidizer-to-fuel ratio demonstrate the effectiveness of LACE cycles but also their complexity. In sizing hypersonic vehicles and their propulsion system, some of the characteristic times of importance that define the fundamental physics are size invariant while others are not, a critical consideration for testing articles in wind tunnels.
Propulsion Cycles
sp propuls
2023-11-28
43 pages
Article/Chapter (Book)
Electronic Resource
English
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