[ExI] space-x sticks the landing

[Anders Sandberg]

On 2015-12-22 09:12, Anders Sandberg wrote:
>
> In the pictures it looks like the vehicle came in from the sea side, 
> which makes sense from a safety perspective, but I can't figure out 
> the orbital mechanics.

Ah, here Elon explains it:
http://www.spacex.com/news/2015/12/21/background-tonights-launch

> In the case of the Falcon 9 rocket, the boost stage is able to 
> accelerate a payload mass of 125 metric tons to 8000 km/h and land on 
> an ocean platform or to 5000 km/h and land back at the launch site. 
> The second one is lower because the rocket is moving super fast away 
> from the launch site, so it has to do a screetching U-turn with 
> nitrogen attitude thrusters, then fire the engines to create a 
> reversed ballistic arc, then reorient again for atmospheric entry 
> and have the engines pointed in the right direction for the landing 
> burn. Since the propellant is liquid, it wants to centrifuge out 
> during these maneuvers, so there has to be a system of baffles and 
> internal holding tanks to keep it in place. It also needs three 
> axis control surfaces that don't melt easily and work well from 
> hypersonic through subsonic speeds.



-- 
Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University

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