Russia's best defenses against ballistic missiles ring Moscow, leaving much of the rest of the country exposed to Ukraine's growing missile arsenal. That concentration is why Ukraine's homegrown ballistic missiles could cause Russia real trouble beyond the capital, even as Russia's air defenses show gaps elsewhere, expert Vadym Kushnikov says, Ukrainian Radio reports.

Russia has the systems to stop ballistic missiles, Kushnikov continues, but it has massed the best of them around Moscow: the S-500 "Prometey", with interceptors adapted from the A-135, the Soviet-era shield built to defend the capital from missiles.

Other regions, by his assessment, are left more open to Ukraine's massed and combined strikes. That matters now that Ukraine's own ballistic missile, such as the Sapsan, is entering combat.

The best defenses ring Moscow

"If you analyze the characteristics, Russia today has concentrated its most modern S-500 complexes, with 77N6-N and 77N6-N1 interceptors, in Moscow Oblast," Kushnikov says.

Elsewhere, he said, Russia is short of air-defense complexes, the S-400 among them, a shortfall he said is visible in satellite imagery.

Ukraine's ballistic program grows

Ukraine's deep-strike arsenal has been shifting from foreign-supplied systems to homegrown ones. Alongside its Neptune and Flamingo cruise missiles, it now fields the Sapsan, an Iskander-class ballistic missile with a range of about 500 kilometers, which President Volodymyr Zelenskyy confirmed was in combat late last year.

A domestic ballistic missile will let Ukraine strike deep inside Russia without waiting for a Western green light.

Production faces hard hurdles

Building them is the hard part. Ukraine's rocket-engineering tradition runs deep, Kushnikov suggests, but its production sites, mostly in the east, are direct targets of Russian strikes.

The missiles also depend on components that are difficult to make, chiefly solid-fuel rocket engines and the guidance that steers a warhead flying at five times the speed of sound along a ballistic arc.

"The combination of all these factors is exactly what our engineers have worked on for years, building the Ukrainian ballistic shield," he adds.