Difference between revisions of "J-20 "Juno" Basic Jet Engine"

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{{:J-20 "Juno" Basic Jet Engine/Box}}
The '''J-20 "Juno" Basic Jet Engine''' is the first [[Jet engine|air-breathing engine]] which uses [[liquid fuel]] and [[intake air]]to unlock in the [[Technology tree|tech tree]]. It is also the most basic one, hence the name. Although it is inferiour to the later jets in terms of thrust, fuel efficiency and speed capability, it yet is the first engine allowing for reasonable extended athmospheric flight. It is also the only jet engine with a tiny form factor, allowing for some fun ultra-light builds.
== Performance and usage ==
[[File:J-20 Juno Basic Jet Engine velocity curve.png|thumb|Visualization of the thrust multiplier curve for velocity]]
[[File:J-20 Juno Basic Jet Engine atmosphere curve.png|thumb|Visualization of the thrust multiplier curve for atmospheric pressure]]
Being the most basic one, it lacks many of the defining traits of the other jet engines. Regarding its performance stats, it can be counted to the low-speed engines, as well as the bigger [[J-33 "Wheesley" Basic Jet Engine]]  and the enormous [[J-90 "Goliath" Turbofan Engine|J-90 "Goliath"]]. Having the same thrust-to-speed behaviour, it has a considerable lower fuel efficiency and no thrust reverse. Note that 'low fuel efficiency' has to be seen only referring to jet engines, as it is still better than all (athmosphere-usable) rocket engines by a factor of 20.
As with all jet engines, its thrust decreases significantly with altitude. Its maximum '''stationary''' thrust is rated at 20 kN at sea level. At about 8,000 m it generates just 10 kN, and at about 15,000 m it generates no more than 3.3 kN, ceasing to work entirely at about 18,300 m. Note that the behavior between these points (as shown in the part stats) is slightly non-linear.
Thrust output also varies with '''speed''', although far less than on the more advanced engines. Similar to the other two low-speed engines, its thrust does not noteably increase with speed, in contrast to the high-speed engines. Up to Mach 0.5 the thrust drops to about 80%, recovering to 105% at about Mach 1.5. Going faster, the thrust drops considerably quick, limiting usage to about Mach 2.1.
The [[Specific_impulse|I<sub>sp</sub>]] stays constant over the full range of application, which is a big change compared to KSP in pre-1.0 versions. It is rated at 6,400 s, putting it in the middle range of the Jet engines, with even the [[J-404 "Panther" Afterburning Turbofan]] high-speed jet being more efficient. As it is capable of sustained Mach 2 flight even with lowest tech plane parts, it is well suited low and partly medium range flight, while fuel efficiency makes longer range trips difficult, unless the pilot is very patient (Jeb is not...) and low speed is not a problem.
Its tiny (Mk0) size makes it useful for fuselage-mounted engines when used with the [[Mk0 Liquid Fuel Fuselage]] and the [[Small Circular Intake]]. Note that there are no aerodynamically-shaped command pods which share the same Mk0 size as the J-20, however many [[Probodobodyne Inc.]] cores have the same general diameter. This engine is not for impatient pilots, as its acceleration is minimal, especially on the bumpy level 1 [[runway]] in early [[career]] mode.
Overall, it works best between 8,000 and 12,000 m altitude. Flying lower, the high air resistance requires more thrust which lowers the fuel efficiency, while in higher areas the engine's thrust output is simply too low for reasonable performance in flight.
Note that currently, the only planets which this engine will work on are [[Kerbin]] and [[Jool]]'s moon [[Laythe]].
== Product description ==
|A small turbojet. Not very efficient, anemic thrust, but hey--it's cheap! And it's so cute...look at the little thing!
== Trivia ==
The Juno may be named after the [https://en.wikipedia.org/wiki/Junkers_Jumo_004 Junkers Jumo 004], one of the first jet engines.
== Changes ==
* Initial release

Revision as of 18:08, 17 March 2017