It's addressed in the sense that they live with it. The rocket still does a suicide burn.
I mean, take a yardstick or short rod or something, and try to balance it upright on the tip of your finger. That's basically what they're doing, but with a -rocket-. It's amazing.
The magic is in a) ensuring the whole construct survives reentry, and b) timing the landing burn - even a single Merlin engine is too powerful for the almost empty rocket to hover, so they need to zero out their velocity at precisely the moment they're hitting the ground. There's no second attempt.
Indeed. For their last launch, they decided to try landing the booster with three engines rather than one, which brings the whole 'hoverslam' concept to the next level.
This was considered so risky that they didn't try landing it on the barge, for fear of damaging it. Instead, they soft landed on the ocean.
But much to everyone's surprise, it actually worked! There's a picture of the Falcon 9 booster floating awkwardly. Musk said they'll try to tow it to shore.
And all that is really the core of why I love SpaceX: continuous improvement. It's a grand thing!
While you drop your hand toward the ground at mach 5.
- The wafer thin margin of actual payload that the booster put up now being shared with landing fuel
- Engine restart after launch
- Re-entry forces on the engines
- The fact (perhaps since addressed) that a single Merlin puts out more thrust at near minimum throttle than the dry mass of the booster itself.
Think about that last one. If you start the burn too early you'll miss the ground .. for a while. The lesson here is trust calculus!