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

Revision as of 23:48, 6 March 2017

J-20 "Juno" Basic Jet Engine
Jet engine by C7 Aerospace Division
Radial size		Tiny
Cost	(total)	450.00
Mass	(total)	0.250 t
Drag		0.2
Max. Temp.		2000 K
Impact Tolerance		7 m/s
Research		Aviation
Unlock cost		2 000
Since version		1.0.5
Part configuration		SmallJetEngine.cfg
Maximum thrust		20.00 kN
Isp	(max)	6400 s
Fuel consumption		0.06 /s
Intake air consumption		1.40 /s
Thrust vectoring		No
Electricity generated		1 ⚡/s
Testing Environments
On the surface		Yes
In the ocean		Yes
On the launchpad		Yes
In the atmosphere		Yes
Sub-orbital		No
In an orbit		No
On an escape		No
Docked		No
Test by staging		Yes
Manually testable		Yes
Packed volume		220 l

The J-20 "Juno" Basic Jet Engine is the first air-breathing engine which uses liquid fuel and intake airto unlock in the 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

Visualization of the thrust multiplier curve for velocity

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". 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 I_sp 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

Trivia

The Juno may be named after the Junkers Jumo 004, one of the first jet engines.

Changes

1.0.5

• Initial release