A NASA-nál már a tisztán elektromos transzkontinentális repülőgépek akkumulátorait tervezik. Ez mekkora előrelépés?

Jet-propelled animals

Main article: Aquatic locomotion § Jet propulsion

Cephalopods such as squid use jet propulsion for rapid escape from predators; they use other mechanisms for slow swimming. The jet is produced by ejecting water through a siphon, which typically narrows to a small opening to produce the maximum exhalent velocity. The water passes through the gills prior to exhalation, fulfilling the dual purpose of respiration and locomotion.[1] Sea hares (gastropod molluscs) employ a similar method, but without the sophisticated neurological machinery of cephalopods they navigate somewhat more clumsily.[1]

Some teleost fish have also developed jet propulsion, passing water through the gills to supplement fin-driven motion.[7]: 201 

In some dragonfly larvae, jet propulsion is achieved by the expulsion of water from a specialised cavity through the anus. Given the small size of the organism, a great speed is achieved.[8]

Scallops and cardiids,[9] siphonophores,[10] tunicates (such as salps),[11][12] and some jellyfish[13][14][15] also employ jet propulsion. The most efficient jet-propelled organisms are the salps,[11] which use an order of magnitude less energy (per kilogram per metre) than squid.[16]

Bebizonyítottam, hogy a jet hajtás jelentéséhez nem feltétlenül szükséges éghető üzemanyag. az angol nyelvben szimplán csőhajtást jelent, ami egy reakciós hajtómű, azt jelenti, hogy egy csőben egyenirányított formában áramlik a folyadék vagy a gáz, aminek ellenreakciójaként az objektum ezzel ellentétes irányba halad.

Jet hajtás szót alkalmazzák az állatvilág egyes tagjaira is, és tengeri hajtóművek is erre épülnek.

Víz alatti jet hajtás ábrája: [link]

[link]

A repülőgép hajtóművekhez hasonlóan 2 fő fajtája van:

Axial and centrifugal

Advantages

Pump jets have some advantages over bare propellers for certain applications, usually related to requirements for high-speed or shallow-draft operations. These include:

Higher speed before the onset of cavitation, because of the raised internal dynamic pressure

High power density (with respect to volume) of both the propulsor and the prime mover (because a smaller, higher-speed unit can be used)

Protection of the rotating element, making operation safer around swimmers and aquatic life

Improved shallow-water operations, because only the inlet needs to be submerged

Increased maneuverability, by adding a steerable nozzle to create vectored thrust

Noise reduction, resulting in a low sonar signature; this particular system has little in common with other pump-jet propulsors and is also known as "shrouded propeller configuration";[3] applications:

Warships designed for low observability, for example the SwedishVisby-class corvette.

Submarines, for example the Royal Navy Trafalgar class and Astute class, the US Navy Seawolf class and Virginia class, the French Navy Triomphant class and Barracuda class, and the Russian Navy Borei class.

Modern torpedoes, such as the Spearfish, the Mk 48 and Mk 50 weapons.

Pump-jets were once limited to high-speed pleasure craft (such as jet skis and jetboats) and other small vessels, but since 2000 the desire for high-speed vessels has increased[citation needed] and thus the pump-jet is gaining popularity on larger craft, military vessels and ferries. On these larger craft, they can be powered by diesel engines or gas turbines. Speeds of up to 40 knots (45 mph; 75 km/h) can be achieved with this configuration, even with a displacement hull.[9]

Pump-jet powered ships are very maneuverable. Examples of ships using pumpjets are the Car Nicobar-class patrol vessels, the Hamina-class missile boats, Valour-class frigates, the Stena high-speed sea service ferries, the United States Seawolf-class and Virginia-class, as well as the Russian Borei-class submarines and the United States littoral combat ships.

HA csőbe teszed a propellert akkor 20%-al megnő a hatásfoka, így elérheti a 80%-ot is.

Egy mérnök beszél erről itt:

[link]

De ha csőbe teszed a légcsavart amit elektromotor hajt, akkor az elégséges.

Egy azonos teljesítményű sugárhajtómű és sima propelleres benzines wankel motor nem tud hasonló hatásfokon működni. Ugyanis a szabadon forgó propeller hatásfoka leesik amint a propeller tollai hangsebességre gyorsulnak. Viszont ha csőbe teszed és több propellert hajtasz vele, akkor már igen. Ugyanis a csőben nem tud kialakulni a propeller végénél az örvény ami lerontja a hatásfokot.