LV-N "Nerv" Atomic Rocket Motor

LV-N "Nerv" Atomic Rocket Motor
Liquid fuel engine by Jebediah Kerman's Junkyard and Spacecraft Parts Co
Radial size		Small
Cost	(total)	10 000.00
Mass	(total)	3.000 t
Drag		0.2
Max. Temp.		2500 K
Impact Tolerance		12 m/s
Research		Nuclear Propulsion
Unlock cost		45 000
Since version		0.17
Part configuration		liquidEngineLV-N.cfg
Maximum thrust	(1 atm)	13.88 kN
	(vacuum)	60.00 kN
Isp	(1 atm)	185 s
	(vacuum)	800 s
Fuel consumption		1.53 /s
Thrust vectoring		No
Electricity generated		5.0 ⚡/s
Testing Environments
On the surface		Yes
In the ocean		No
On the launchpad		No
In the atmosphere		Yes
Sub-orbital		Yes
In an orbit		Yes
On an escape		Yes
Docked		No
Test by staging		Yes
Manually testable		Yes

The LV-N "Nerv" Atomic Rocket Motor is a low-thrust, high-efficiency rocket engine. It is modeled after the real-world theoretical nuclear thermal rocket (NTR), which uses a fission reactor to heat its propellant and force it out of the rocket nozzle to generate thrust (as opposed to a normal rocket, which ignites the propellant and uses the energy released by the resulting chemical reaction for that purpose).

Usage

Unlike other rocket engines, the Nerv consumes only liquid fuel. As such, a Nerv-powered craft should make use of liquid fuel fuselages (like the Mk1 Liquid Fuel Fuselage), which contain only liquid fuel and no oxidizer. Alternatively, rocket fuel tanks with the oxidizer removed can be used, although this results in an extremely poor mass ratio.

When outside the atmosphere, the Nerv has superb efficiency, with a vacuum I_sp of 800 s: higher than any other liquid fuel engine and the second highest in the game overall, beaten only by the Dawn ion engine. Compared to the Dawn, it has 150x greater thrust per second of I_sp. Its combination of comparatively high thrust and high efficiency makes it a popular choice for interplanetary stages.

The Nerv has a thrust-to-weight ratio of approximately 2, the lowest of all liquid engines. This makes it a very poor choice for large landers, or other craft that will need to move large masses against strong gravity. Its I_sp and thrust while in atmosphere is incredibly poor; at Kerbin sea level, its thrust-to-weight ratio is below 1 and thus prohibits first-stage rocket use. For these reasons, the Nerv finds its niche in orbital and interplanetary maneuvering of larger crafts that can't afford to use the extremely low-thrust Dawn engine.

The engine is quite long, being almost exactly the same length as a Mainsail engine. Nerv engines on a landing stage require some interesting structure designs to get the landing gear low enough to clear the bottom of the engine.

Product description

“

Despite the big scary trefoil painted onto the side of this engine, its radioactive exhaust, and tendency to overheat, the LV-N Atomic Rocket Motor is harmless. Mostly. Note that the LV-N is the only LV series engine to run solely on Liquid Fuel - the future is glowing bright! — Rockomax Conglomerate

”

Trivia

• Before 1.0, the LV-N consumed both liquid fuel and oxidizer, unlike real-world nuclear thermal rockets. This due to programming constraints, as stated in its parts.cfg file, and Squad's unwillingness to add another tank type. Real NTRs run on liquid hydrogen, but are capable of using other propellants at lower efficiencies. With the addition of liquid-fuel-only tanks for spaceplanes, this constraint vanished.

“

Yes, I know this is wrong. NTRs don't actually burn fuel and oxidizer, but we don't want to jump into making separate tanks for the two yet. — Excerpt from the part.cfg pre-1.0

”

• Before version 1.1.3, this engine used to overheat when run at full throttle for the long burns typical of nuclear-powered craft (though it usually stabilized before completely filling the overheat bar)[1] but this is no longer the case and very long burns can be performed without fear of overheating.
• Interestingly, the LV-N has two shrouds, one for each half of the engine. Both are toggleable in the editor.
• The "Nerv" nickname is likely a reference to NERVA, or "Nuclear Engine for Rocket Vehicle Application", a NASA program to create a nuclear thermal rocket.
• The description of this part may be a reference to Douglas Adams' Hitchhiker's Guide to the Galaxy series, in which the Earth is described as "mostly harmless".
• The Nerv's use of liquid fuel, rather than hydrogen, as its propellant suggests that the true chemical identity of LiquidFuel is methane; methane is used both in combustive rocket engines in real life, and is also an attractive option as a nuclear-thermal rocket propellant.

Changes

1.0

• LV-N “Nerv” Engine now runs solely on Liquid Fuel.
• No longer has a gimbal.
• Cost increased to 10000.
• Mass increased from 2.25 to 3.
• Isp curve extended past 1 atmosphere; Isp drops to 0.001 at 2 atm.

0.24

• Cost increased from 1700 to 8700 (and made meaningful)

0.22

• Alternator added; engine now generates 5.0 electric charge per second.

0.17

• Initial release