RK-7 "Kodiak" Liquid Fueled Engine

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RK-7 "Kodiak" Liquid Fueled Engine
Part image
Liquid fuel engine by
Reaction Systems Ltd

Radial size Medium
Cost (total) 1 100.00 Funds
Mass (total) 1.25 t
Drag 0.2-0.3
Max. Temp. 2000 K
Volume  ?
Impact Tolerance 9 m/s
Research Heavier rocketry.png Heavier Rocketry
Unlock cost 4 400 Funds
Since version 1.4.1
Part configuration LiquidEngineRK-7.cfg
Maximum thrust (1 atm) 247.00 kN
(vacuum) 260.00 kN
Isp (1 atm) 285 s
(vacuum) 300 s
Fuel consumption 17.68 Units of fuel/s

Thrust vectoring No

The RK-7 "Kodiak" is a liquid fueled engine similar to the LV-T30 "Reliant" Liquid Fuel Engine, but with improved first-stage performance and a "Soviet" theme.


The Kodiak has the same weight and cost as the Reliant, but its atmospheric specific impulse is 7.5% higher, and it can burn fuel 12% faster; these combine to give it 20% higher thrust at sea level. Its high atmospheric thrust-to-weight ratio is only outmatched by five engines, all of which are much more expensive.

Its vacuum Isp is lower than the Reliant's; the crossover in Kerbin's atmosphere is at 7km above sea level. So the Kodiak is best used as a first stage engine or a liquid booster. (Particularly, it can be attached to the FL-C1000 Fuel Tank, imitating the appearance and role of the Soviet R-7 boosters which inspired both of these Kerbal parts.)

The Kodiak has no thrust vectoring / gimbal range. Visually, it is meant to pair well with the RV-1 "Cub" Vernier Engine, which imitates Soviet vernier engines from the same era.

The Kodiak does have the disadvantage of being unlocked late in the tech tree (level 6, versus the Reliant's level 3). It was also considerably less useful prior to the changes made in version 1.6.

Product description

A bear of an engine. This quad-nozzled beast comes with multiple cowling options, and no gimbal. Don’t forget those verniers.

Reaction Systems Ltd


This engine has three models that can be switched in the editor. The Bare and Shroud Big variants are radial size medium, while the Shroud Small is size small.

Bare variant
ShroudBig variant
ShroudSmall variant
The different variants of the engine


While bears are often used as a symbol of Russia, Kodiaks live exclusively in the United States.

Real-world comparison

The RK-7 was inspired by the Soviet RD-107 engine.


  • Increased unlock cost from 4200 to 4400
  • Decreased cost from 1300 to 1100
  • Increased crash tolerance from 6 to 9
  • Increased EC generation from 3 to 5
  • Increased ASL thrust to 247
  • Increased vacuum thrust from 240 to 260
  • Improved Isp
  • Added ModuleTestSubject
  • Initial Release