Rocket Ascents... Can divers breach like a fish (split from Accident in Mich)

[CIBDiving]

Why would we assume that any acceleration would occur after the first few meters?

There won't be - just as in air, a 'terminal' velocity would be reached, as soon as lift equals drag acceleration stops.

What am I missing?

Not a thing - the only Question is - can a diver achive a velocity of about 20 ft/sec.
If they can, than it's possible for a diver to 'breach', if not than they can't.

As for terminal velocity Question - anybody have any drag coeficients for a diver??

 

[lamont]

I would think that some terminal ascent rate would be reached relatively fast and it would just be a cruise to the surface. Where is the acceleration from?

The accelleration comes from the buoyant force. Once the BCD is fully inflated (and expanding air is going out the OPV valve) this force will be constant. If the system was frictionless then the velocity of the object would increase linearly. But, the resistance of the water is going to go as the square of the velocity (BOW fact) and you can work out the exact velocity where the forces will be balanced which will be the terminal velocity. Its going to depend on the surface area of the diver as they go through the water -- so someone big who is flared will have a lower terminal velocity (and lower accelleration) than someone skinny who is going up vertically.

And, of course, the inverse tachyon particles push you up. Can't forget those. They come from the whales in the ocean, just like in Star Trek IV...

 

[Saipanman]

I'm not a scientist, but I was an undergrad for 7.5 years, thereby making me smarter than most of you, so here's my guess:

Either the breaching diver was using a flux capacitor or the guy who allegedly saw the diver breach was using a bit of THC.

Just my educated guess.........

 

[serambin]

Forget my earlier drysuit test, I have a simpler far more disgusting and accurate test.

1. Side of beef "trim" to desired weight (bouyancy is probably similiar to a person).
2. 40lb lift bag. Roughly the lift capacity of most BCs.
3. Weight belt.

Slice a hole in the beef and secure weight belt through hole with approx. 10lbs of weight to simulate weights worn.

Attach lift bag to belt.

Fire away.

Start out with a heavier weight, say 200lbs. The nearly neutral bouyancy of the meat could be used to compensate for the weight of the diver and a nearly empty tank. Both of which are near neutral in the water, but heavy after the breach.

If you want to get scientific you could wrap it in an old weightsuit for added bouyancy and attach the lift bag directly to the beef and, finally, hit the quick release on the weight belt buckle as you finish filling the lift bag to simulate a panicked rush to the surface.

I wouldn't advise eating the meat afterwards, but if your crazy enough to try this, a little bacteria isn't gonna scare you off.

What a waste of good meat . . . I mean, like have a BBQ instead dude.

Stan

 

[serambin]

I'm not a scientist, but I was an undergrad for 7.5 years, thereby making me smarter than most of you, so here's my guess:

Either the breaching diver was using a flux capacitor or the guy who allegedly saw the diver breach was using a bit of THC.

Just my educated guess.........

Your correct, you ain't no scientist if it took you 7.5 years for a degree.

 

[Saipanman]

The first four years entailed learning how to spell "You're" correctly. The last 3.5 I learned about sarcasm...

 

[serambin]

The accelleration comes from the buoyant force. Once the BCD is fully inflated (and expanding air is going out the OPV valve) this force will be constant. If the system was frictionless then the velocity of the object would increase linearly. But, the resistance of the water is going to go as the square of the velocity (BOW fact) and you can work out the exact velocity where the forces will be balanced which will be the terminal velocity. Its going to depend on the surface area of the diver as they go through the water -- so someone big who is flared will have a lower terminal velocity (and lower accelleration) than someone skinny who is going up vertically.

And, of course, the inverse tachyon particles push you up. Can't forget those. They come from the whales in the ocean, just like in Star Trek IV...

I think it's the tachyons. I find that only Tachyons ( or single malt scotch ) an breach me 6 feet in the air.

Stan

 

[serambin]

The first four years entailed learning how to spell "You're" correctly. The last 3.5 I learned about sarcasm...

I assume your grades on spelling wasn't the problem, so why did it take 3.5 years to learn sarcasm?

Stan

 

[Saipanman]

Too much single malt scotch. Or not enough, I'm not sure which.

 

[TheYellowSubmarine]

I think theoretically breaching might be possible by someone who knows just how to do it. Its possible to get the entire body to clear the surface in a much shorter distance by being horizontal. Then the centre of mass only needs to be (conservatively) about 1 foot above the surface of the water. If you have a really big wing, your centre of mass might be at surface level at equilibrium (ie, just sitting there). So I'll assume that upward forces stop at the surface, and so you need a velocity to get you up 1 foot (about 5MPH). If you had very streamlined gear, and were very quick and agile, you could rise vertically (to minimise surface area perpendicular to the velocity, increase streamlining, etc to attain the maximum possible velocity), then just as your centre of mass clears the surface, very smoothly move into the horizontal position. Of course this would require super precision(you've got about a quarter of a second to perform the maneuver once your centre of mass hits the surface). This would also require lots of strength and agility(you've got a whole lot of scuba gear, tank,etc to move down into position, and somehow bring your legs out of the water, without inducing any extra downward forces).

Theoretically speaking of course...

(by the way, I'm doing my masters in physics)