New US underwater drone
Discussion
popeyewhite said:
I think we're some way of a commercially or technically viable airflight capable submersible. Moving smoothly underwater and gliding through air are two different very complex abilities.
Both the US and the Soviet Union looked at it. The Americans came close to commissioning a prototype, back in the Cold War.In fairness, it would be easier to do with a drone, as you don't have to carry the weight of a pressure hull big enough to put humans in.
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AnotherClarkey said:
It is a well established and very elegant concept using variable buoyancy to allow it to glide forward while ascending and descending in the water column. Sometimes Wiki can be very helpful...
https://en.wikipedia.org/wiki/Underwater_glider
' At a certain depth, the glider switches to positive buoyancy to climb back up and forward, and the cycle is then repeated.'https://en.wikipedia.org/wiki/Underwater_glider
It's not really changing buoyancy though is it - merely changing the angle of the hydroplanes. The weight of the device is the same - unless you're going to play submarines with compressed air.
I think that structure could glide, and be made strong enough to pancake on the water intact, before setting off underwater.
If you want it to change depth in the water, you don't need hoofing great wings and they'd increase water resistance - so it either glides in air, or they must be for something else...
Simpo Two said:
' At a certain depth, the glider switches to positive buoyancy to climb back up and forward, and the cycle is then repeated.'
It's not really changing buoyancy though is it - merely changing the angle of the hydroplanes. The weight of the device is the same - unless you're going to play submarines with compressed air.
I think that structure could glide, and be made strong enough to pancake on the water intact, before setting off underwater.
If you want it to change depth in the water, you don't need hoofing great wings and they'd increase water resistance - so it either glides in air, or they must be for something else...
It does actually change the buoyancy - and can do it repeatedly. It glides in the water, translating vertical motion driven by gravity (descending) or buoyancy (ascending) to horizontal travel in much the same way as a sailplane - although a sailplane can't manage the buoyancy-driven bit...It's not really changing buoyancy though is it - merely changing the angle of the hydroplanes. The weight of the device is the same - unless you're going to play submarines with compressed air.
I think that structure could glide, and be made strong enough to pancake on the water intact, before setting off underwater.
If you want it to change depth in the water, you don't need hoofing great wings and they'd increase water resistance - so it either glides in air, or they must be for something else...
Have a look here:
https://en.wikipedia.org/wiki/Buoyancy_engine
Simpo Two said:
If you want it to change depth in the water, you don't need hoofing great wings and they'd increase water resistance - so it either glides in air, or they must be for something else...
Think flying wing or lifting body: yes, it encloses its powerplant, payload and control systems, but it does so with a form that also generates hydrodynamic lift (at low cruising speeds).Equus said:
Think flying wing or lifting body: yes, it encloses its powerplant, payload and control systems, but it does so with a form that also generates hydrodynamic lift (at low cruising speeds).
Hydrodynamic 'lift', yes. What I have difficulty with is the idea it increases buoyancy - it's like saying an aeroplane gets lighter as it ascends.Simpo Two said:
Hydrodynamic 'lift', yes. What I have difficulty with is the idea it increases buoyancy - it's like saying an aeroplane gets lighter as it ascends.
That bit is explained by AnotherClarkey's link, and is effectively just like the 'blown' ballast tanks of a normal submarine, but you're only trying to achieve a change between very slight positve bouyancy and very slight negative bouyancy.AnotherClarkey's analogy with a slope-soaring glider is a good one: a slope soarer picks up altitude from an updraft over a slope, then gradually glides down... rinse and repeat.
A bouyancy engine driven drone picks up altitude (reduced depth) by decreasing its bouyancy to float upwards, then gradually glides down... rinse and repeat.
FWIIW, I'm not convinced that this drone necessarily uses a bouyancy engine (at least not all the time). Whilst they are very efficient, the downside of those is that you necessarily end up with a sawtooth 'flight profile' as you go through the repeated float/glide cycles. Fine - and perhaps even beneficial - if you're doing oceanographic surveys... less so if you're trying to sneak up on a Russian missile cruiser. I suspect that it will have at least some capability for powered, level 'flight' and manoeuvring as well.
otolith said:
Presumably the big win with using changes in buoyancy to propel it is complete silence.
Yes, silence and very low energy consumption. I think like some predecessors (ZRay) it has some propellers or waterjets for auxiliary propulsion (manoeuvring and travel on the surface) but the primary means of travel is by means of variable-buoyancy propulsion.I imagine it will be able to loiter around for weeks or months in total silence operating completely autonomously. It could be covering huge distances or just ambling up and down outside Murmansk etc. This is the first one which they are describing as 'payload capable' which obviously makes you wonder what it could be packing.
Edited by AnotherClarkey on Friday 3rd May 14:06
Simpo Two said:
It's not really changing buoyancy though is it - merely changing the angle of the hydroplanes. The weight of the device is the same - unless you're going to play submarines with compresssed air.
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It may have a hollow air filled chamber which it squeezes to become less bouyant, like a swim bladder in a fish. As it floats up to the surface, the wings push it forward in the same way as one of them flat swimming floats will scoot along if you hold it underwater then let go..
Super Sonic said:
It may have a hollow air filled chamber which it squeezes to become less bouyant, like a swim bladder in a fish. As it floats up to the surface, the wings push it forward in the same way as one of them flat swimming floats will scoot along if you hold it underwater then let go.
That makes some sense, though it seems a rather slow way to proceed, albeit quietly which is important.But it would show up on sonar... or is the shape too 'stealthy' for that?
Edited by Simpo Two on Friday 3rd May 15:04
Equus said:
popeyewhite said:
I think we're some way of a commercially or technically viable airflight capable submersible. Moving smoothly underwater and gliding through air are two different very complex abilities.
Both the US and the Soviet Union looked at it. The Americans came close to commissioning a prototype, back in the Cold War.In fairness, it would be easier to do with a drone, as you don't have to carry the weight of a pressure hull big enough to put humans in.
I wonder what happens when the US Navy device encounters seaweed, flotsam and jetsam? Maybe it stays deep enough to be below most of it?
otolith said:
Super Sonic said:
Jetsam is stuff thrown off boats. Not stuff that falls off airplanes, if that's what you are thinking!
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