SpaceX Launch & Recovery

SpaceX Launch & Recovery

The Silicon Graybeard reports on watching a Falcon 9 launch from, and return to, Cape Canaveral.

This photo captures the entirety of the first stage's activity. The launch is the big, bright arc stretching up and to the left. At the top of the arc, the engines shut off, the second stage separates, and the first stage booster turns over. That is the blank spot after the end of the arc. The we have the bluish, fuzzy area. That is the booster firing an engine to cancel its forward speed, slow down to a stop and then accelerate back toward the launch site. This doesn't take nearly as much power as the launch because it is no longer carrying the second stage and it is almost empty of fuel, much like an empty beer can that still has a teaspoon of beer sloshing around in the bottom of the can that you can get if you tilt your head way back and hold the can near vertical.

Now it's heading back to the launch site. When it gets close, like a few miles, it fires the engine again to kill most of it's speed. That's the straight line just to the right of the main arc in the top half of the image. When it gets close to the landing site, it fires the engine again to drop its speed to near zero so it can touch down without damage.

Fuel management is critical. Start with too much fuel and you won't be able to slow down enough because you will be carrying too much mass. Start with too little fuel and you are liable to run out before you land. In either case you are going to crash instead of landing.