The Molniya (Russian: Молния, meaning "lightning"), GRAU Index 8K78, was a modification of the well-known R-7 Semyorka rocket and had four stages.

[3] 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 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.