The R-56 were five proposed rockets developed by the OKB-586 design bureau under Mikhail Yangel. No formal terms for the five different designs have been discovered resulting in Bart Hendrickx writing in the Journal of the British Interplanetary Society referring to the initial two designs as the Small and Big versions. Hendrickx referred to the later three designs as “Monoblock”, “first polyblock” (similar to the Big R-56) and “second polyblock” (similar to the Small R-56). The monoblock version was considered for use in the Soviet lunar program.