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Comment by kevinsundar | Hacker News Reader

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kevinsundar

Direct link to an animation of catching a rocket with a helicopter: https://youtu.be/joONWIGtcdY?t=858

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Catching things in the air is hard...

But it's been done[1].

[1]: https://en.wikipedia.org/wiki/Fulton_surface-to-air_recovery...

More like these, given that the rocket will be falling rather than tethered:

https://en.m.wikipedia.org/wiki/Mid-air_retrieval

Also https://en.wikipedia.org/wiki/Corona_(satellite)#Recovery

Like he says in the video, catching is actually the easy bit.

Having the booster survive the re-entry heating and aerodynamic loads while only using passive methods to slow it is the hard bit.

In case anyone's youtube is also not opening at the right spot, the animation is around 10:00.

Can't edit my top post for some reason but here's the updated link: https://youtu.be/joONWIGtcdY?t=583

Looks like the video got truncated after the livestream.

Same technique as NASA investigated for recapturing a Saturn V booster:

"[The helicopter] would be gigantic. The rotor diameter would be over 120 meters (400 feet). Its empty weight would be over 200,000 kilograms (450,000 pounds), with a useful load of nearly 250,000 kilograms (550,000 pounds), for a gross weight of a whopping 453,000 kilograms (1,000,000 pounds)"

http://www.thespacereview.com/article/3741/1

I've only watched the animation, not the whole video, but it seems like this is missing a crucial step. It seems to show the first stage magically start moving backwards, rather than continue to move forwards (coasting) and use thrusters to turn around for re-entry down-range. I'm sure the actual rocket experts will have it right, but is it me or the animator that's misinterpreted things?

yeah I wondered about that too, I suspect it naturally arcs over and comes down heavy end first (a bit like a shuttlecock) with empty tanks the heavy end is the motors.

It's just a combination of camera tracking and the acceleration of the second stage. The rocket follows a ballistic trajectory, there's no need for it to turn around. Or are you just thinking of orientation? The rocket will probably have RCS to do it's flip and re-enter with proper orientation.

Yes, orientation. The orientation doesn't change on screen, and yet it's going thrusters first to the right, which looks like where it's come from.

Yeah, I gotta get a new job.

Same. This got my envy meter charged up for a good week of feeling sad that I'm not working on things like this.

The failure modes on that look fun. I wonder how much they are planning on paying the pilot.

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