Is a supersonic boat possible?

strap a russian supercavitating torpedo to one of these things, and bobs your uncle.

 

How's about we define "boat" (for the purposes of this discussion) as a vehicle that moves over the surface of the water, with some fixed rigid part of it in contact with the surface, nocloser to the end of the body than 10% of LOA. i.e. the rigid, fixed part must be within the main body of the vehicle, not trailing behind it.
Steve

PS - the simple answer to the question originally posed must be "Yes". It is just that no-one has figured it out yet, but a s/s boat IS possible...

 

It's definately possible, eventually, at least.

 

Sean,

Perfect! I have an old 1.5Kw radar--now what did I do with those scram jets?...

 

As I recall, Bluebirds last speed attempt was a crash because he probably crossed a small wavelet from his first run. Drives, controls, hull shape and power would have to look like a cross between the jet cars and jet fighters. Since the cars are not powered by the wheels, all water propulsion is off also. Lip Service as to calling it a boat.

 

I am aware of only one watercraft to ever exceed the speed of sound. Built by Convair and first flown on May 9, 1953, the XF2Y Sea Dart had a V-hull, delta wing, and twin waterski-like hydroplanes that extended from the bow/nose for takeoff and retracted once clear of the surface. Power was twin J46 turbojets (6000# each). The craft could reach 695mph at 8,000 feet altitude. On water, the beast was a pilot's hell to handle and vibrated like a jackhammer in waves higher than two inches. To the best of my knowledge, no other watercraft of any sort has approached this speed. (And yes, folks, the XF2Y is technically an airplane, although it behaves as a conventional boat below about 50 knots.)

Now, to reach that speed while in contact with the water....

Well, the obvious solution is to dangle a rope off the back of a Super Hornet or something like that. I think that counts as cheating. So we go with a boat shape for the bottom and airplane shape on top, but since only about 2" of hull could possibly touch the water at this speed, it's mostly about aerodynamics. And power. A helluva lot of power. Stick an afterburning M88 or F100 jet engine in it, either has enough power to toss a 9-ton boat directly upwards about 50,000 feet. We make the boat strong and rigid (read -> heavy) to take the incredibly huge loads, and shock-mount the cabin, 'cause this brute will vibrate like crazy upon hitting the wake of a muskrat. Now we add 40 bottles of Alberta Rye Whiskey, and have the crew draw straws. Short straw drives...

Oh, so you want to go supersonic in water? Now there's something. A kilometre-and-a-third per second. We can only just do that in air right now, and that's only with spacecraft and missiles, up at flight level 800 where there's almost no air anyway. So we fire a rocket-propelled missile straight into the lake from far enough back for it to accelerate up to speed.... oh, whoops, at velocities over a few hundred km/h, water is as rigid and unyielding as granite.

We routinely cut 2-inch steel plates with water jets at the speeds we're talking about here. For some reason, I don't think a supersonic boat will ever be practical. Possible, maybe- and some nutbar will try- but it's not something that is likely to work too well.

 

Bluebird

A LOT of factors were involved in the Bluebird crash.

http://www.users.myisp.co.uk/~climengs/bluebird/coniston.htm

 

Sea Dart

Landing and takeoff speeds on the Sea Dart were about 120 knots. Don't big offshore boats run those same speeds NOW?

 

Boats

A boat is something that MUST operate on the surface of the water because it's NOT an airplane.

For example, Donald Campbell's Bluebird? NOT an airplane.

 

keep it coming, i rated this trhread 5 star

(have to run)

 

Is any one here versed on the instantanious energy a 2" wave will transfer to the keel and/or hull skin at 800 mph? Maybe a solid hull of Titanium would survive? No human will. - G force would probably shred the body from any harness.

 

Hull Design

In case you hadn't noticed, none of the discussion from me about potential supersonic boat configurations has involved planing hulls, but instead considers hydrofoil boats (like the START of this thread) or supercavitation concepts.

 

supersonic hydrofoil boat

Fair enough. Excellent thread by the way.

Much of this discussion has hinged on the definition of a boat. A jet dragging a wire does not a boat make. However, I don't suppose anyone will argue that a hydrofoiled moth - i.e. "flying moth" - is not a boat. Put some big jets on a hydrofoiled hull, that at speed (still crazy fast!), will lift the hull above the catastrophic chop.

If the jet and hull provide a stabilizing downward force that is countered by a lifting foil it becomes hard to argue that it is not a boat. That is, it can't fly. Ever. The vessel needs water to do what it does. It can be successful because the foil lifts the hull clear of the danger zone (relative danger ).

Look forward to reading more.

Kevin

 

another thought

if a foiled vessel is riding a couple feet above the mean surface of the water, how does the air flowing around the vessel deform the surface of the water? what kind of deformation would be beneficial to control?

Kevin

 

Surface effects would probably render the vessel out of the water making it an aircraft, if it did't, the water pressure would probably destroy it. Although the one I'm working on can get airborne at 0 kts, at about 60 kts it will become airborne anyway.