You are being upvoted, but I think that when looking at your proposal seriously, it has flaws.

Let's try with an example.

Until now: government pays $100 to build a rocket to go to the Moon, say $50 now and $50 at launch. Rocket explodes? No problem, you still get your $50.

Your proposal: government pays $100 to build a rocket to go to the Moon. $50 now, $50 if it lands. Ops. No one shows up. Err... Let's try $60 now, $40 if it lands? Nope... Still nobody around to get this contract...

Why? Because a company would charge you (simplifying a bit) $150, of which $100 now, and $50 if the rocket lands.

Congratulations. You have contributed to ballooning the Space budget. Taxpayers are thankful.