Russia's Federal Security Service (FSB) suspects that plans for two of its new, game-changing hypersonic missiles have been leaked to Western spies — and heads are sure to roll as an angry Kremlin investigates the leaks.Russia's Ministry of Defense released on Thursday new footage of two of its most revolutionary weapons systems, a hypersonic Kh-47M2 "Kinzhal" nuclear-capable, anti-surface missile, and the Avangard, a maneuverable ballistic missile reentry vehicle specifically made to outfox the US missile defenses arrayed around Europe.The FSB now suspects these same systems, both of which cope with the challenges of flight at around ten times the speed of sound, have been leaked to the West."It was established that the leak came from TsNIIMash [a Russian state-owned defense and space company] employees," a source close to the FSB investigation Russia's Kommersant newspaper, as the BBC notes."A lot of heads will roll, and for sure this case won't end just with a few dismissals," the source said.The hypersonic arms raceThe US, China, and Russia are all locked in a heated arms race to create weapons that can travel many times the speed of sound in an effort to defeat all existing missile defense.China and Russia frequently test their weapons and have even fielded a few systems ahead of the US, but their focus is nuclear, while the US seeks a higher goal.With nuclear weapons, like the kind Russia and China want on their hypersonics, accuracy doesn't matter. But the US wants hypersonics for percision strike missiles, meaning it has the incredible technical challenge of trying to train a missile raging at mach 10 to hit within a few feet of a target.Nuclear weapons represent the highest level of conflict imaginable, in most cases what's essentially a world-ending scenario. If Russia or China hit the US with nuclear weapons, the US would fire its own nuclear weapons back against nuclear weapons silos, military command centers and even cities, a response likely to end much of life on earth in the process. Basically, that means Russia and China are building weapons they can't use without bringing nuclear retaliation down on their own heads.The US's vision for precision-guided hypersonic conventional weapons that no missile defenses can block has a range of applications. The US's proposed hypersonics can target specific people and buildings, making them useful for strikes like the recent ones in Syria.But if Russia's hypersonic know-how has somehow slipped into Western hands, as the FSB has indicated, their comparative advantage could be even weaker.