LV-N "Nerv" Atomic Rocket Motor

From Kerbal Space Program Wiki
(Redirected from LV-N Atomic Rocket Motor)
Jump to: navigation, search
LV-N "Nerv" Atomic Rocket Motor
Part image
Liquid fuel engine by
Jebediah Kerman's Junkyard and Spacecraft Parts Co

Radial size Small
Cost (total) 10 000.00 Funds
Mass (total) 3.00 t
Drag 0.2
Max. Temp. 2500 K
Volume  ?
Impact Tolerance 12 m/s
Research Tech tree nuclear propulsion.png Nuclear Propulsion
Unlock cost 45 000 Funds
Since version 0.17
Part configuration liquidEngineLV-N.cfg
Liquid fuel engine
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 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).


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 a superb efficiency, with a vacuum Isp of 800 s: higher than any other liquid fuel engine. This remarkable efficiency makes it quite popular for upper stages, as it is ideal for interplanetary travel.

However, the Nerv 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 small spacecraft (such as skycranes and small probes), 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.

It 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


  • 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".


  • 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