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Yes, it IS rocket science !

MNW67 said:
Is there any reason, in theor,y why a rocket coming down shouldn't be as stable as a rocket going up. Instinctively, it feels like it won't be. But I can't think what the scientific explanation would be.
Click to expand...
Consider a game of darts where you try to land the dart tail first.
 
On the subject of landing the booster, I think it was the wings that helped them make a breakthrough along with directional thrusters. The main problem seems to be trying to avoid setting fire to yourself as you fly in to the hot gasses that you just burned to keep you from falling too quickly.
 
MNW67 said:
Is there any reason, in theor,y why a rocket coming down shouldn't be as stable as a rocket going up. Instinctively, it feels like it won't be. But I can't think what the scientific explanation would be.
Click to expand...
Reverse propulsion.

Cars are better going forward,
 
MNW67 said:
Is there any reason, in theor,y why a rocket coming down shouldn't be as stable as a rocket going up. Instinctively, it feels like it won't be. But I can't think what the scientific explanation would be.
Click to expand...
It goes up at Mach gazillion with aerodynamic control using velocity and drag for stability. It sheds truckloads of fuel weight as it goes. To come down, it still needs a load of fuel for essentially, controlling a rock that wants to accelerate not slow gently to 0 m/s at a perfect point in time.
 
MNW67 said:
Is there any reason, in theor,y why a rocket coming down shouldn't be as stable as a rocket going up. Instinctively, it feels like it won't be. But I can't think what the scientific explanation would be.
Click to expand...
The simplest version is that In terms of stability, the bit for the first stage doesn't have a pointy nose cone. After the second stage is ejected it's essentially a pringle tube.

To be more complicated you need to keep the centre of drag behind the centre of mass. That naturally helps keep the flight stable. Going up thats pretty easy as the engine block is quite heavy. Even then the stages need active control, either vectoring engines or reaction control thrusters or active surfaces to keep the stage pointing in the right direction.

With a returning stage theres no nice nosecone to keep airflow smooth and with landings legs the centre of drag is still at the bottom end which means it will tend to try to flip so that's at the back. In reality if they aren't being controlled the stages tumble chaotically.

The dart analogy is pretty good.
 
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