Tupolev, however, was worried about Nikita Khrushchev's growing interest in rocket weapons.
Rockets seemed invincible for existing and future anti-aircraft systems.
The NORAD system, which was being developed and deployed by the United States at the time was practically impermeable for the strategic bombers of that era.
Tu-121 was conceived as an aircraft able to reach speeds of over 2,000 km/h and a flight altitude of 50 km which would allow it to easily penetrate both American air- and missile defence systems.
However, even at the early stages, Tupolev himself realized that his bureau was unable to develop such an aircraft.