Small? With the sole exception of Buran, every payload orbited by anyone since Skylab has been in that class or lower. - - - Updated - - - MAKS was not Spiral; it was a small hydrolox/kerolox spaceplane with a large drop tank, using the existing An-225 for airlaunch. The tripropellant motor was successfully tested, and the whole thing was probably technically viable. Economic and political viability are different matters entirely, of course, and it still wasn't SSTO.