Before the Stratolaunch was ever conceived, the Tupolev Bureau proposed a fully reusable replacement for the Buran Space Shuttle
The "OOS" Which stood for Odnostupenchati Orbitalni Samolyot, (one-stage orbital plane)

Like the Stratolaunch system The shuttle would ride under the  Aerospace Transport System (AKS) A Dual fuselage version of the Antonov An-225 with between 24 and 40 Jet Engines
The OSS would have a weight of 675 tons and the AKS would have a weight of 1000 tons for a total of around 1600 tons.


Primarary source
False Steps: The Space Race as It Might Have Been
By Paul Drye


cloud image By Alvesgaspar - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index...
cloud image By Bharatahs - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index...