The Molniya (, meaning "lightning"), GRAU Index 8K78, was a modification of the well-known R-7 Semyorka rocket and had four stages. The rocket was given the name Molniya due to the large number of Molniya communication satellites the rockets launched. The 8K78 resulted from a crash program by the Korolev Bureau to develop a booster for launching planetary probes. A larger third stage was added along with a fourth stage (Blok L) that was designed to fire in-orbit to send the payload out of LEO (replacing the inaccurate direct ascent of the first generation Luna probes launched on the 8K72) and the core and strap-ons had the new uprated 8D74K first stage engines. The first couple of 8K78s flown used an 8K74 core however vehicles flown in 1962-63 used the older 8K71 core. The 8K74 core returned for vehicles flown in 1964 and later. The initial 8K78s had a faulty Blok I design that was prone to vibration issues and pump cavitation. The Blok I was redesigned afterward and the improved version was first flown on 11 November 1963. The uprated 8K78M booster was introduced in 1965 but 8K78s continued to fly into 1967. The Molniya also carried early Venera probes to Venus. Molniya (E6) was a minor revision adapted for Luna E-6 series space probes where the guidance system for the entire launch vehicle was moved to the probe itself.

Characteristics

Launches

Molniya rockets were launched 40 times: