The NK-89 was a modified version of the hydrogen-powered NK-88[1] and was designed to run on both liquified natural gas[2] (LNG) and kerosene.[2] It was intended for use on the proposed Tupolev Tu-156,[2] a modified version of the Tupolev Tu-154B.[2] This aircraft was to have cryogenic tanks in the rear of the cabin and forward baggage hold to store the LNG.[2] Kerosene would be carried in the wing tanks.[2] In January 1989, a test flight of a prototype of this engine was carried out onboard of the Tupolev Tu-155 flying laboratory where LNG was used as fuel.[1]
By default, the engine would run on LNG,[2] but kerosene could be used when flying out of airports where LNG is unavailable[2] or in case of emergency.[2] The switch from LNG to kerosene could be made in-flight in 5 seconds.[2]