A shortfin mako shark in the North Atlantic, near the Azores

>>Capable of swimming at speeds of up to 74 km/h (46 mph), the shortfin mako is the world’s fastest species of shark. Scientists now have a new understanding of how it’s able to reach such speeds, and they believe that their findings could be applied to improving human technology.<<

https://newatlas.com/mako-shark-scales-speed/58718/

PermeateFree said:

A shortfin mako shark in the North Atlantic, near the Azores

>>Capable of swimming at speeds of up to 74 km/h (46 mph), the shortfin mako is the world’s fastest species of shark. Scientists now have a new understanding of how it’s able to reach such speeds, and they believe that their findings could be applied to improving human technology.<<

https://newatlas.com/mako-shark-scales-speed/58718/

If I remember correctly, a swimming costume using shark scale technology has already been banned by the Olympics.

> on key parts of the shortfin mako, those 0.2-mm-long denticles are capable of flexing up to an angle of 40 degrees out from the body. Thanks to the mako’s pop-out denticles, though, flow separation is greatly minimized along the length of its body. The protruding scales help prevent the formation of eddies.

But that’s not how I remember it. This is actually new.

> making them more aerodynamic

And, more importantly, delaying the onset of stall.

The following is the version I remember.

https://www.bionicsurface.com/en/drag-reduction-with-shark-skin-technology-riblets-and-coating/

And this https://www.nasa.gov/audience/forstudents/5-8/features/F_NASA_Goes_to_the_Olympics.html

There are well over 1,300 spin-offs of NASA technology. What do technology to reduce drag in airplanes and a racing yacht have in common? They both use “riblets.” Riblets are not small pieces of barbecue meat. Riblets are V-shaped grooves with angles that point in the direction of the air flow. They are no bigger than a scratch. And they look like very tiny ribs. Riblets help reduce “skin-friction” drag. NASA learned that fast-swimming sharks have something like riblets on their skin. A riblet skin was invented for NASA. It was later used on the U.S. rowing shell that competed in the 1984 Summer Olympics in the four-oar-with-coxswain category.

Riblet technology has also been used in competition swimsuits. U.S. swimmers who wore these suits won 13 gold medals, three silver medals and one bronze medal in the 1995 Pan American Games.

mollwollfumble wonders if this technology with help with rockets, because skin friction drag on rockets has a huge influence on maximum altitude.

mollwollfumble said:

mollwollfumble wonders if this technology with help with rockets, because skin friction drag on rockets has a huge influence on maximum altitude.

FWIW I came up with a system that would reduce aerodynamic drag on a rocket by about 50%. I thought it up independently, but after a search for anything similar I found that someone else had a similar idea in the mid 90’s. They did a bunch of CFD on the system and it showed a 50% reduction in drag.
So occasionally, I can come up with clever stuff.

Spiny Norman said:

mollwollfumble said:

mollwollfumble wonders if this technology with help with rockets, because skin friction drag on rockets has a huge influence on maximum altitude.

FWIW I came up with a system that would reduce aerodynamic drag on a rocket by about 50%. I thought it up independently, but after a search for anything similar I found that someone else had a similar idea in the mid 90’s. They did a bunch of CFD on the system and it showed a 50% reduction in drag.
So occasionally, I can come up with clever stuff.

:-O

More details please !

mollwollfumble said:

Spiny Norman said:

mollwollfumble said:

mollwollfumble wonders if this technology with help with rockets, because skin friction drag on rockets has a huge influence on maximum altitude.

FWIW I came up with a system that would reduce aerodynamic drag on a rocket by about 50%. I thought it up independently, but after a search for anything similar I found that someone else had a similar idea in the mid 90’s. They did a bunch of CFD on the system and it showed a 50% reduction in drag.
So occasionally, I can come up with clever stuff.

:-O

More details please !

Do you want me to post it here, or perhaps in a FB message?

Spiny Norman said:

mollwollfumble said:

Spiny Norman said:

FWIW I came up with a system that would reduce aerodynamic drag on a rocket by about 50%. I thought it up independently, but after a search for anything similar I found that someone else had a similar idea in the mid 90’s. They did a bunch of CFD on the system and it showed a 50% reduction in drag.
So occasionally, I can come up with clever stuff.

:-O

More details please !

Do you want me to post it here, or perhaps in a FB message?

Here would be best. I only check facebook about once a fortnight.

Righto.
One of my party tricks is to combine two otherwise unrelated technologies/materials/etc into something that works better than just the one.

Years back I read about the Russian Shval torpedo. Most torpedos do about 40 kts or so, but the Shkval does over 200 kts thanks to the rocket motor that powers it. The rocket in itself isn’t enough to make it go that fast, what it does is had a blunt-ish cap on the nose that simply pushes the water out of the way so that instead of the usual ~ 1m x 6-7m torpedo running completely covered in water, it’s only about 0.2 metres and the rest of the torpedo flies along pretty much in a reasonable vacuum. So the total drag is hugely reduced and thus that’s how it goes so fast. Rumours are that the later versions might do 300 kts.

Anyway in 2017 I was thinking about rockets that have to make the trek through the thick atmosphere for a while to get up far enough into the vacuum of space, and I suddenly realised that because air and water are both fluids, it might be possible to do much the same thing at the pointy end of a rocket. So after a bit of thought I came up with something like a solid-fuelled rocket in the tip of the nose that fired into the direction of flight, but in the exhaust there’d be a carbon-carbon cap that diverted the energetic exhaust gasses in a fan out of the nose at about a 45° angle. If you lit the drag-reducing rocket as the main rocket was going through about mach 0.8 (that’s where the transonic drag starts to become annoying) and size it so it would fire all the way up to about the 40 km mark where there’s not much air left, that would work in a similar manner to the Shkval torpedo. Also, if you sized the drag-reducing rocket just right and got the exhaust angle just right, it would easily provide enough thrust to cancel out any weight it added to the entire structure and so not be any weight performance penalty at all.
I had a poke around and found a paper on a similar thing from 1995. I’ll have to dig around in my rocket papers stash to find it.

I also thought that what might have been able to be done with the Apollo missions is to not waste the rockets on the abort system tower on top of the Command Module – At the point where it would have been not needed any more and ignited to get rid of it, perhaps it could have been fitted with a little larger rockets so that if everything was running nominally, they could have burnt those abort rockets for a while to get a bit of a boost out of it before letting it go. Probably not worth the trouble though. And of course I’ve been eyeing-off the SpaceX Dragon 2 capsule for the same reason.

Oh and another thing I noticed with rockets from the last decades or so – A lot of them have a larger diameter top section than the lower ~80% or so. I realised that they’re doing a cheap & nasty version of the drag-reduction thing, by using the larger diameter front to make a big enough hole in the air for the rest of the rocket below it. Simple but I bet it works well.

Spiny Norman said:

Righto.
One of my party tricks is to combine two otherwise unrelated technologies/materials/etc into something that works better than just the one.

Years back I read about the Russian Shval torpedo. Most torpedos do about 40 kts or so, but the Shkval does over 200 kts thanks to the rocket motor that powers it. The rocket in itself isn’t enough to make it go that fast, what it does is had a blunt-ish cap on the nose that simply pushes the water out of the way so that instead of the usual ~ 1m x 6-7m torpedo running completely covered in water, it’s only about 0.2 metres and the rest of the torpedo flies along pretty much in a reasonable vacuum. So the total drag is hugely reduced and thus that’s how it goes so fast. Rumours are that the later versions might do 300 kts.

Anyway in 2017 I was thinking about rockets that have to make the trek through the thick atmosphere for a while to get up far enough into the vacuum of space, and I suddenly realised that because air and water are both fluids, it might be possible to do much the same thing at the pointy end of a rocket. So after a bit of thought I came up with something like a solid-fuelled rocket in the tip of the nose that fired into the direction of flight, but in the exhaust there’d be a carbon-carbon cap that diverted the energetic exhaust gasses in a fan out of the nose at about a 45° angle. If you lit the drag-reducing rocket as the main rocket was going through about mach 0.8 (that’s where the transonic drag starts to become annoying) and size it so it would fire all the way up to about the 40 km mark where there’s not much air left, that would work in a similar manner to the Shkval torpedo. Also, if you sized the drag-reducing rocket just right and got the exhaust angle just right, it would easily provide enough thrust to cancel out any weight it added to the entire structure and so not be any weight performance penalty at all.
I had a poke around and found a paper on a similar thing from 1995. I’ll have to dig around in my rocket papers stash to find it.

I also thought that what might have been able to be done with the Apollo missions is to not waste the rockets on the abort system tower on top of the Command Module – At the point where it would have been not needed any more and ignited to get rid of it, perhaps it could have been fitted with a little larger rockets so that if everything was running nominally, they could have burnt those abort rockets for a while to get a bit of a boost out of it before letting it go. Probably not worth the trouble though. And of course I’ve been eyeing-off the SpaceX Dragon 2 capsule for the same reason.

Thanks. That makes perfect sense.

Spiny Norman said:

Oh and another thing I noticed with rockets from the last decades or so – A lot of them have a larger diameter top section than the lower ~80% or so. I realised that they’re doing a cheap & nasty version of the drag-reduction thing, by using the larger diameter front to make a big enough hole in the air for the rest of the rocket below it. Simple but I bet it works well.

I don’t think so. The longer and slimmer the rocket, the less the drag, quite startlingly so. What I believe happened is that they wanted to carry these lightweight bulky payloads into space and only had slim powerful rockets. So compromised by putting a big fairing on the top to fit the payload in. The drag would get a lot worse, but the rocket was powerful enough anyway to handle the extra drag.

mollwollfumble said:

I don’t think so. The longer and slimmer the rocket, the less the drag, quite startlingly so. What I believe happened is that they wanted to carry these lightweight bulky payloads into space and only had slim powerful rockets. So compromised by putting a big fairing on the top to fit the payload in. The drag would get a lot worse, but the rocket was powerful enough anyway to handle the extra drag.

Righto, but I still think it would help at higher mach numbers. A little, anyway.