In fact, it's part of what gives the Falcon 9 its unprecedented thrust — the force behind its launch that allows it to push more than 50,000 pounds of cargo into orbit. The extra reserves also provide more wiggle room to reach orbit, and for SpaceX to land and recycle the rocket's booster — the biggest and most expensive part of the Falcon 9.
Once inside the rocket, however, the fuel begins to warm up, expand, and boil off. That fuel loss starts the launch clock ticking.
"That changes how much performance you get carrying into orbit, and we don't want to cut into those margins," Insprucker said.
