Allow me to share with you, the evolution of the OSIRIS series of rockets: OSIRIS Mk.I was the first of the OSIRIS rockets, it, unfortunately, failed to take off as the stage 1 boosters destroyed the stage 1 and 2 main rocket motors. OSIRIS Mk.II was a huge improvement. And it actually took off. However, there were still problems to be ironed out. OSIRIS Mk.III was a small improvement of the Mk.II, but nothing really noteworthy. OSIRIS Mk.IV was a complete failure. The removal of the stage 1 boosters resulted in the stage 1 main rocket motors not providing enough thrust to get off the ground. OSIRIS Mk.V was the platform on which the Mk.VI and VII rockets were built. The addition of smaller, solid fuel motors as stage 1 boosters generated enough force for the Mk.V to take off, and reach for the skies. The only problem was the lack of fuel for the stage 2 and 3 liquid engines. OSIRIS Mk.VI was an attempt to fix the fuel problem. Sadly, the stage 2 liquid motors still lacked enough fuel to escape the atmosphere. OSIRIS Mk.VII was the final product of 3 hours of testing. No one had yet to die, and the Mk.VII punched the kerbals into space, and eventually, on orbit. While true, orbit was reached, it didn't last. After 40 minutes of flight, the orbit turned out to be flawed and the space rocket crashed. The kerbals so excited about reaching orbit, that they forgot to open the parachute, and thus, crashed.
