Real scientists never truly retire. At 74, Victor Kudryavtsev continued his work as a leading scientist at the Central Research Institute of Machine Building, known in the West as TsNIIMash — Russia's main rocket development center, located in the town of Korolyov near Moscow.

Kudryavtsev has worked for Russian space industry for 48 years. He raised a family, trained countless young researchers, and was proud of his contributions to the exploration of space. His studies focused on spacecraft survival of the fiery re-entry into a planet atmosphere. He received state awards and enjoyed respect of his peers in Russia and abroad.

All this changed in the early hours of July 20, when a dozen FSB (Russian Federal Security Service — successor of KGB) commandos raided his apartment. In front of his wife Olga and two visiting 9 and 12 year-old granddaughters, who were scared to death, they pulled the elderly Kudryavtsev from his bed.

They took him to the Lefortovo prison in Moscow. He was asked to leave behind his medications for a heart condition and diabetes. In the hours that followed the FSB raided Kudryavtsev’s office at TsNIIMash, his summer house, his garage, and the apartments of his family members. They were seeking evidence of spy activities or valuables that could be interpreted as payments from foreign entities.

The searches all came up empty. And six weeks later, the prosecution has not presented any material evidence of a crime. Kudryavtsev did not work on weapons and has had no access to secrets for more than 20 years, beginning when his daughter married a foreigner and settled abroad.

Still, following his arrest, he was accused of high treason for disclosing top-secret data on the Russian newest hypersonic weapons to a source in the West. The term “hypersonic” refers to a rocket speed in excess of five times the speed of sound.

According to Kudryavtsev’s family, the investigation of his alleged crime has focused on an unclassified project being pursued by his and two other Russian research institutions in collaboration with Belgium's Von Karman Institute of Fluid Dynamics and the German Aerospace Center in Cologne. The final joint report on the project, submitted in 2013, proposed a new technology for tackling heat generated by the re-entry of a hypersonic vehicle in the atmosphere that threatens structural integrity of the vehicle. Although this is of general value to the aerospace industry, this new technology can also be used in weapon designs.

Kudryavtsev’s recent trouble traces back to March of this year, when Russian president Vladimir Putin announced the development of a highly maneuverable, nuclear capable Hypersonic Glide Vehicle “Avangard” that could be delivered atop an intercontinental ballistic missile and strike anywhere in the world within half an hour, invincible to any existing countermeasures. According to Putin, it would be combat-ready by 2020.

Two months later, CNBC, citing anonymous sources within U.S. intelligence, reported that Russia had successfully tested the Avangard weapon. This must have triggered Russian concern that technical data about supersonic glide vehicle had leaked to the West. Having no clue how the information was acquired by the U.S., the FSB looked for a scapegoat to calm the fury of the Russian military and, probably, of Putin himself.

Kudryavtsev, with his expertise in the field and his contacts with European scientists, happened to be an obvious target.

Clearly, TsNIIMash would not have conducted an open research in collaboration with the European Union without blessing from the Russian aerospace industry. In a Kafkaesque twist, Kudryavtsev is now paying a price for legally collaborating with Belgian and German scientists before relations with Russia went south in 2014 due to Russian invasion of Ukraine.

During the first two weeks in Lefortovo prison, Kudryavtsev lost 10 pounds. On Aug. 15, the St. Petersburg Union of Scientists sent a letter to President Putin, asking him to rescind Kudryavtsev’s pre-trial detention on the grounds of his age and poor health. The Council on Human Rights in the Russian Federation filed a similar appeal on Aug. 23. On Sept. 3, according to Kudryavtsev’s lawyer, he was transferred to the isolation unit of the Moscow City Hospital No. 20 for evaluation.

Eugene M. Chudnovsky is a Distinguished Professor at the City University of New York and Co-Chair of the Committee of Concerned Scientists.