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LV-N "Nerv" Atomic Rocket Motor

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LV-N "Nerv" Atomic Rocket Motor
Part image
Liquid fuel engine by
Jebediah Kerman's Junkyard and Spaceship Parts Co.
Radial size Small
Cost (total) 10 000.00 Fund
Mass (total) 3.00 t
Drag 0.2
Max. Temp. 2500 K
Impact Tolerance 12 m/s
Research Tech tree nuclear propulsion.png Nuclear Propulsion
Unlock cost 45000 Fund
Since version 0.17
Part configuration liquidEngineLV-N
Maximum thrust (1 atm) 13.88 kN
(vacuum) 60.00 kN
Isp (1 atm) 185 s
(vacuum) 800 s
Fuel con­sumption 1.53 units of fuel/s

Thrust vectoring × No
Testing environments
On the surface × No
In the ocean × No
On the launchpad × No
In the atmosphere ✓ Yes
Sub orbital × No
In an orbit × No
On an escape × No
Docked × No
Test by staging × No
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, 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).


The LV-N has low thrust and a very high mass, giving it the worst thrust-to-weight ratio of all liquid engines. For this reason, it is a very poor choice for propulsion in skycranes, despite its high vacuum specific impulse. Its Isp while in atmosphere is also quite poor, making it not recommended for operation within atmospheres or for landings on larger bodies.

However, when outside the atmosphere, its efficiency becomes superb with a vacuum Isp of 800 s, by far the highest of any liquid fuel engine. This remarkable efficiency makes it quite popular for upper stages as it is ideal for interplanetary travel. With the 1.0 update, this engine consumes only liquid fuel. As such, it is much more mass-efficient to build your craft with tanks that only contain liquid fuel and no oxidizer.

It will overheat when run at full throttle for the long burns typical of nuclear-powered craft, but will usually stabilize before completely filling the overheat bar. It is also quite long, being almost exactly the same length as a Mainsail engine. LV-N 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!
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


  • The description of this part contains a reference to Douglas Adams' Hitchhiker's Guide to the Galaxy series, in which the human race is described as "Mostly harmless".
  • 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.
  • 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.


  • 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.
  • Cost increased from 1700 to 8700 (and made meaningful)
  • Alternator added; engine now generates 5.0 electric charge per second.
  • Initial release