As I remember, Russians once even launched "Soyuz" (R-7) on Pentaborane, achieved some additional kilograms of load. Fortunately , all finished ok, but they don

As I remember, Russians once even launched "Soyuz" (R-7) on Pentaborane, achieved some additional kilograms of load. Fortunately , all finished ok, but they don't repeat these experiment "because of expensive".