R-7 packet scheme

Origins: Tikhonravov and the 'Rocket Packet'

The theoretical origin of the packet scheme lies in Konstantin Tsiolkovsky's 'rocket squadron' (эскадра ракет) concept, sketched in his 1935 work 'The Maximum Speed of a Rocket.' Tsiolkovsky envisioned multiple rockets flying together with only hydraulic connections, but it was Mikhail Tikhonravov who turned this into an engineering design.

In 1947, Tikhonravov, then deputy director of NII-4, began investigating parallel staging to solve two structural problems with sequential staging: the unsolved challenge of air-starting a second-stage engine in flight, and the impractically enormous length of a single very large rocket. His concept was to mechanically join several identical rockets into one 'packet,' ignite all engines simultaneously on the ground, and sequentially drain and jettison the outer rockets.

On 14 July 1948, Tikhonravov delivered an expanded report titled 'Paths to Achieving Long Ranges with Ballistic Rockets' at the Academy of Artillery Sciences. He argued that a packet scheme could theoretically achieve unlimited range and even place an artificial satellite into orbit. The audience was hostile. His department was disbanded as 'pursuing irrelevant problems' and Tikhonravov himself was demoted from deputy director to scientific consultant.

Korolev's Intervention and Okhotsimsky's Optimisation

Sergei Korolev recognised the concept's potential immediately upon reading Tikhonravov's report. In December 1949, he issued an official contract to NII-4 for 'Research on the feasibility and advisability of creating packet-type long-range composite rockets,' reviving Tikhonravov's team. In March 1950, Tikhonravov's second report, 'Rocket Packets and Prospects for Their Development,' demonstrated that a two-stage packet of three R-2-class rockets could deliver a heavy warhead over intercontinental distances.

Korolev favoured a central core with four boosters over the simpler three-rocket packet and commissioned the Steklov Mathematical Institute's Department of Applied Mathematics, led by Dmitry Okhotsimsky, to optimise it. In 1951, Okhotsimsky's team produced a general study of sequential and parallel staging, including fuel transfer between stages, providing the mathematical foundation for the R-7's exact booster proportions and geometry.

Gröttrup's G-5 and the German Contribution

Helmut Gröttrup's German rocket team, confined on Gorodomlya Island, independently developed a similar parallel-staging concept between 1947 and 1949: the G-5, a bundle of multiple G-4-class rockets. This is considered a direct ancestor of the R-7, and the tapered conical booster shape that persisted through Soyuz variants was first proposed by the German team in 1949. For political reasons, the German contribution was long minimised, but contemporary scholarship recognises a triple lineage of Tikhonravov–Okhotsimsky–Gröttrup as the packet scheme's true origin.

Core Design Principle and Historical Significance

The packet scheme's decisive advantage was that all first-stage engines ignited on the ground, completely bypassing the unsolved technical challenge of high-altitude air-start ignition. The core's RD-108 and the four boosters' RD-107 engines, totalling 20 combustion chambers, all fired simultaneously on the launch pad; the boosters separated after approximately 120 seconds upon propellant depletion. This was the only feasible ICBM design path at the time. Although the R-7 was soon obsolete as a weapon, it became the foundation of the Sputnik, Vostok, and Soyuz launch vehicle families.