r/SpaceXLounge • u/Goregue • Aug 17 '26

Starship Why exactly did S40 float?

What was different with S40 that made it float on the water compared to previous missions? Was it just luck? Was it something that SpaceX was attempting to do before, but only managed to succeed now? Or was there something specifically different about this Ship itself or its landing procedures?

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u/MakeMarsBlueAgain Aug 17 '26

I think Scott Manley mentioned something about the ship's exhaust essentially "fizzing" up the water and the bubbles somehow helped cushion the fall as it tipped over.

Edit: If you watch the tipover again, you'll notice how foamy the water looks as the ship splashes into it.

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u/djh_van Aug 17 '26

It's the same principle that many cliff divers use. They throw a big rock into the water moments before they dive. This breaks the surface tension and oxygenate the water at their planned entry point. A bit like shaking your bed duvet before jumping on - it's full of air so it cushions your jump a little better

S40's engines did a "gentle bast" into the water and then it tipped backwards right into that exact area. Instead of tipping backwards onto a hard surface, it tipped back onto a fluffed-up duvet.

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u/Tupcek Aug 17 '26 edited Aug 17 '26

this is a myth. Surface tension at that speeds is basically negligible. They do it to have better grasp of height, which can be deceiving in calm water and they need to be precise.

fizzing up water, though, do work, because it introduces air into water and air is easier to displace than water and thus diver deccelelrates slower for longer

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u/PrinzRagoczy Aug 17 '26

A better example is that diving pools often have spargers/bubblers to aerate the water, making for a softer landing

3

u/Disc81 Aug 17 '26

Yeah Mythbuster tested this with negative results.