Last week, the private rocket company SpaceX performed an extraordinary feat: returning the first stage booster of an orbital rocket back to ground, landing vertically on its tail, right in the center of the landing pad.
Think about what SpaceX did: They took a 12 story rocket weighing 20 tons moving at nearly 4,000 mph, slowed it, stopped it, turned it around, let it fall nearly 125 miles to the ground, reignited the engines, had it follow a descent path, automatically correcting its orientation and attitude, until it landed within a few yards of the pre-chosen spot.
Now SpaceX has released lovely high-res photos of the event.
Moments before landing (photo 1 below), the booster comes in at a slight angle from vertical. Onboard software senses the orientation of the booster (as well as wind speed and other factors) and corrects for it to ensure it lands vertically. Note the landing legs, deployed earlier, after the booster separated from the rest of the rocket, sticking out the bottom at an angle.
A second or two later (photo 2), the booster has reoriented itself, and is very near vertical, ready to land. The rocket exhaust is hitting the ground and billowing out.
From a remotely controlled drone, the view is even more dramatic (photo 3). As you can see, the booster is almost exactly centered over the stylized X (the SpaceX logo, but also a convenient way to mark a spot. Say).
This was the first step in SpaceX's plan: getting the booster back on the ground. The next step, the critical one, is to reuse the booster (or whichever one is brought back down to the ground next). Once that has been achieved, then Elon Musk and SpaceX will have shown they can reuse that rocket, and potentially save tens of millions of dollars on a launch into orbit.
Musk estimates the cost to build a first stage Falcon 9 at around $60 million, while the fuel costs around $200,000. If they can reuse that booster, then even if it costs a few million bucks to fix it back up, that's a savings of over $50 million in launch costs— on a launch that costs roughly $90 million to start with.