During the tense standoff between the United States and Soviet Union in the 1960s, both superpowers sought new ways to gain a strategic edge in the nuclear arms race. One of the most intriguing and perplexing weapon systems to emerge from this period was the Soviet Fractional Orbital Bombardment System, known as FOBS.
FOBS represented a novel approach to delivering nuclear warheads that aimed to exploit gaps in the nascent U.S. early warning radar network. The core concept was to place a nuclear weapon into a low earth orbit using a powerful rocket, but one that would not complete a full orbit of the planet. Instead, after reaching a certain point in its trajectory, the warhead would de-orbit and begin its descent towards the target.
This fractional orbit path made FOBS an unpredictable weapon. Unlike conventional intercontinental ballistic missiles (ICBMs) which follow a predictable arc on their way to a target, FOBS could theoretically approach from any direction, even over the South Pole. With the U.S. early warning radars of the time oriented towards the north where Soviet ICBM launches would originate, FOBS presented the frightening prospect of a surprise nuclear attack with little advance notice.
Development of FOBS began in the Soviet Union in the early 1960s. The famous Soviet rocket designer Sergei Korolev proposed an early concept called the GR-1 Global Rocket, but this never progressed beyond the design phase. Instead, the Soviets settled on a version of FOBS based on the massive SS-9 Scarp ICBM developed by Mikhail Yangel’s design bureau.
This R-36O FOBS variant of the SS-9 was a three-stage rocket over 100 meters tall and weighing nearly 200 tons at launch. It could carry a large thermonuclear warhead of up to 5 megatons into an elliptical low earth orbit less than 150 km in altitude. After reaching a certain point in orbit, the warhead would separate from the rocket and begin its high-speed descent.
The Soviets began deployment of their FOBS system in 1968 with 18 silos built at a missile base near Tyuratam (now Baikonur) in Kazakhstan. This was just a year after the Outer Space Treaty had been signed prohibiting the placement of nuclear weapons in orbit. The Soviets skirted this by claiming FOBS did not complete a full orbit and was merely “fractional.”
When American intelligence discovered the operational FOBS deployment in the late 1960s, it caused significant alarm. The U.S. had no comparable system and there were real doubts about whether the existing safeguards against a surprise attack, like the Ballistic Missile Early Warning System (BMEWS) radars, would be able to detect a FOBS strike in time.
However, the FOBS threat began to diminish in the 1970s for several reasons. Continuing improvements in U.S. early warning systems, including the deployment of satellites and over-the-horizon radars, made a surprise FOBS attack much less likely to succeed. The sheer size of the SS-9 rockets also made them vulnerable to a preemptive strike.
More importantly, advances in technology allowed the Soviets to pursue other more survivable delivery systems like submarine-launched ballistic missiles (SLBMs). FOBS came to be seen as an expensive bespoke capability with marginal strategic value compared to the growing Soviet SLBM force.
By the late 1970s, both the U.S. and Soviet Union were moving to place limits on destabilizing nuclear delivery systems as part of the Strategic Arms Limitation Talks (SALT). The SALT II agreement signed in 1979 explicitly required the Soviets to dismantle their FOBS silos, even though the treaty was never ratified by the U.S. Senate. The last FOBS missile was taken off alert in 1983 and the program faded into obscurity.
In retrospect, FOBS is often seen more as a troubling symptom of the runaway nuclear arms race of the Cold War rather than a truly significant strategic capability. While it did spur U.S. efforts to improve early warning and missile defense, FOBS never really shifted the overall balance of power. It was a highly expensive niche system that the Soviets ultimately abandoned in favor of more flexible delivery options.
However, the core concept behind FOBS of using a fractional orbit to deliver a strategic weapon has reemerged in recent years. In 2021, China reportedly tested a nuclear-capable hypersonic glide vehicle that was launched into orbit by a Long March rocket. After circling the globe, the glider vehicle separated and made a high-speed run towards its target, potentially with the ability to maneuver unpredictably.
The full capabilities of this Chinese system remain unclear, but it appears to build on the ideas originally developed for FOBS, combining them with modern hypersonic glide technology. U.S. officials expressed surprise and concern about the test, noting it could in theory allow China to execute a nuclear strike from an unexpected direction with little warning.
So while the Soviet FOBS itself is long retired, in some ways its shadow still hangs over the nuclear balance today. As hypersonic glide vehicles and fractional orbit systems continue to be developed and refined, echoes of this enigmatic Cold War weapon may well shape the strategic environment for years to come. Maintaining stability in this new era of rapidly evolving technologies will require a clear-eyed understanding of the risks and lessons from earlier efforts like FOBS.
