Hypersonic weapons: Why is Russia accusing its own scientists of treason?

Human rights groups see a pattern.

Mr Smirnov says that, in private conversations, FSB officers have admitted to him that cases about sharing hypersonic secrets were being opened “to satisfy the wishes of those higher up”.

He believes the FSB wants to give the impression that spies are hunting Russian missile secrets “to flatter the ego” of Mr Putin.

The cases come amid a wider rise in treason cases.

Sergei Davidis, who leads work supporting Russian political prisoners at the Memorial human rights centre, speaks of an “atmosphere of spy mania and isolationism”, especially since Russia’s full-scale invasion of Ukraine.

Speaking from Lithuania, where his organisation moved after it was banned in Russia, Mr Davidis says he believes the FSB, keen to show it is delivering, “builds up its reporting statistics through the fabrication of cases”.

But he believes there may be other factors in the arrests of scientists, such as competition for state contracts, or even a Kremlin message of dissatisfaction aimed at all scientists involved in hypersonics.

Mr Smirnov says the FSB sometimes offers more lenient sentences if suspects confess and implicate others.

Kudryavtsev was offered a plea bargain under which he would admit guilt and point the finger at someone else, according to his widow, Olga.

He refused. He died of lung cancer in 2021, aged 77, before his case came to trial.