that it was indeed capable of besting American ABM systems at that time and beforehand. End of deployment and associated reasons There are two main technical disadvantages of the FOBS to consider: Its nuclear payload was drastically reduced relative to that of an ICBM due to the high level of energy needed to get the weapon into orbit. According to American intelligence, the FOBS' nuclear warhead mass needed to be roughly to of that of an ICBM, and required a more robust ablative system, due to the higher entry velocities. The FOBS was less accurate than an ICBM. This was empirically demonstrated in the series of Soviet R-36O flight tests that occurred over 1965-1971. There are a number of other factors to consider that prompted the end of FOBS deployment in the Soviet Union: The FOBS wouldn't be able to overcome later early warning radar system developments made by the US, especially those that came in the form of space-based radar deployments. The US established missile detection systems of this type by the early 1970s. The FOBS was made to counter relatively simple ground-based systems like the BMEWS, not the more expansive radar network that followed it. The Soviet FOBS thus had lost one of its primary capabilities only several years into its deployment, a FOBS strike no longer having an adequate probability of going undetected by the US. An additional primary use of the Soviet FOBS—its ability to counter an American ABM system—was found out to be needless as time passed. Contrary to earlier Soviet projections, the US never built a large ABM system purposed in fending off a Soviet ICBM attack. The only significant American ABM system constructed was Safeguard (initially called Sentinel), but it was shut down by 1976 and mainly China-oriented anyway; it would have been practically useless in the face of anything beyond a limited Soviet nuclear attack regardless of the FOBS. Soviet SLBM technology grew into a good replacement for the FOBS on the basis of low flight time, high range (via the submarine's ability to move near its target), and the element of surprise. The FOBS potentially acted as a dangerous accelerant to the Cold War arms race for the reason that it was most useful in the context of a pre-emptive nuclear strike. A nation observing their enemy developing the FOBS could logically conclude that they viewed a first strike as a