Awesome SpaceX launch yesterday

I admit to living in a news blackout. Very little goes on in the outside world that I know about, but I did catch glimpses of the recent launch and today I watched the whole thing. The launch is one thing, but the rockets returning back to a landing pad boggles my mind. How they managed to make that happen is beyond my comprehension. Just amazing to watch. Only today did I learn that they're sending a car to Mars. ??? Well, it's a start. It is pretty awesome to see the next stage of the space program unfolding and rocket launches return to the Florida coast. Oh, and the highest telemetry reading I saw was close to 27,000 kmh. Sunnova beach, that's hauling the freakin' mail! It was still accelerating as well.

In reply to ncjay :

Having watched someone's video of those boosters coming down- it's almost even more amazing.  They were super sonic up until the last second.  

It's such a simple answer to the 'how to reuse a rocket' question- but such a hard execution.  It would be interesting to see data that shows how much money is saves, especially doing it in that manner (either on the boat or on shore).

They're not saying exactly, but in April last year they said it costs much less than half as much to reuse a stage as to rebuild one. They're aiming for eventual 30-40% savings on launches that cost $62 million.

I think the fast approach, hard decel method is considered preferable because of the shorter burn time. It's ridiculous to watch, especially on one of the feeds with telemetry. 

ncjay said:

Well, it's a start. It is pretty awesome to see the next stage of the space program unfolding and rocket launches return to the Florida coast.

Rocket launches never left Florida though?  Only the manned mission was decommed, but non-manned launches by NASA, SpaceX, and ULA have never stopped.

Saw an explanation for why the center section didn't land: It ran out of some special fuel it has on board that's needed for igniting the engines, so only one engine started.

Keith Tanner said:

...I think the fast approach, hard decel method is considered preferable because of the shorter burn time. It's ridiculous to watch, especially on one of the feeds with telemetry. 

If you think about it it makes sense to wait until that last possible second to burn.  The boosters are being slowed by atmospheric drag, and the lower they get, the more atmosphere, so more free braking.  The engines are optimized for lifting a full rocket with full fuel and payload so the ability to throttle to very low thrust (e.g. hover) with almost no fuel and no payload (effectively making them way more powerful then at liftoff) will be difficult/impossible.  Because the boosters are effectively overpowered the only way to make a smooth landing is to perfectly time the deceleration so that velocity reaches zero at the ground.

Think of it has a reverse calculation of that booster taking off and reaching the height where the booster fires on decent.  Of course drag and the fact that the booster is getting lighter the closer to the ground it gets (because it's burning fuel weight) has to be added in. 

Maths be hard.