If you can afford to visit several locations in Russia on your trip, I recommend visiting at least the
Memorial Museum of Spaceflight in Moscow and
Tsiolkovsky Space History Museum in Kaluga. They are easy to get to (if you pay attention to admission hours notices) and contain rich exhibitions. Even more interesting are museums of the enterprises of space industry, but they are costly to visit and take special tricks to get permit of admission for.
Lovers of the Cold War era can consider visiting a
real missile control bunker hidden under Moscow or
a decommissioned ICBM launch base in Ukraine. Visitors can tap the launch button as much as they like.