Block E (rocket)

Block E is the propulsion unit of Soviet lunar module LK, developed in 1960s by Yuzhnoye Design Bureau as a part of the manned lunar landing program. Block E was designed to soft land LK on the surface of the Moon after orbital velocity was cancelled by Block D and later to launch LK to the Moon orbit for the rendezvous with Soyuz 7K-LOK.

Block E used RD-858, which has one nozzle and is deeply throttleable (from 2050 kg to 858 kg of thrust), as the primary engine. The backup engine was RD-859, which has two nozzles. Engines were equipped with clam-shell doors to prevent damaging it while staying on the surface of the Moon. There were four additional vernier engines placed between main and backup engine nozzles.