Ghost: Stealth Attack Hydrofoil Uses Supercavitation | Hacker News Reader

Ghost: Stealth Attack Hydrofoil Uses Supercavitation

businessweek.com

37 pointsHoff18 comments

Not stealth. Far to many flat 90/45* surfaces and corners. Nobody with any understanding of radar was involved in the design of that thing.

Not supercavitating. Supercavitation is based on cavitation, not sucking down air from the surface. http://en.wikipedia.org/wiki/Supercavitation. And the amount of energy needed to create a supercavitation void around those hulls ... The Shkval is essentially an underwater rocket and it still uses exhaust gases to top up the bubble in which it flies (see the little holes near the nose) http://en.wikipedia.org/wiki/VA-111_Shkval.

Not a hydrofoil. No foils. It looks to be a SWATH hull (Small Waterplane Area Twin Hull) another great Canadian invention. http://en.wikipedia.org/wiki/Small-waterplane-area_twin_hull

Who did this guy know at Businessweek to get this sales pitched turned into an "article"?

Won't an air envelope reduce friction as much as a vapor envelope?

RE: SWATH: their patent http://www.rexresearch.com/sancoff/sancoff.htm discusses hydrofoils and SWATH as prior art [0182], [0183], but fails to describe how their "buoyant tubular foils" (BTFs) [200] are different.

They're pontoons on movable outriggers. Novel, but useless. An air envelope would certainly reduce friction but would basically kill buoyancy. Big metal tubes don't float in air. So without any real foils/wings to generate lift, even if a bubble could be formed, the pontoon would literally fall to the bottom of the bubble.

Supercavitating hulls (ie the ShVal torpedo) suspend themselves within a bubble via their noses. They are moving so fast that the nose, the only spot where the torpedo touches the water, provides enough lift to keep the thing in the bubble. But you need rocket-like accelerations to keep this going.

From their patent "whereby to provide propeller generated super-cavitated water flowing from the propellers and thence along an outer surface of said vehicle;" WTF? There is no such thing as super-cavitated water. Cavitation presupposes a CAVITY, a void ... something other than water. Maybe water with bubbles? Prop wash?

http://www.google.com/patents/US20120097086

Another noteworthy design deviation (compared to run of the mill SWATH) of this vessel is the dihedral angle of the pontoon supports. Based on the wake behind the vessel, it appears that the pontoon supports might even be providing some lift. This could provide a hydrofoil like lifting effect, but the design of those supports wouldn't make a terribly efficient foil. The aspect ratio is all wrong. Hydrofoils typically have a very short chord, because water generates plenty of lift without a high aspect ratio.

This thing just sounds like a whole lot of smoke and mirrors. Hopefully the guy can sell it to some Hollywood studio to use in Mission Impossible 10 so he can recoup some of his investment.

It also reminds me of this Canadian invention: http://en.wikipedia.org/wiki/HMCS_Bras_d'Or_(FHE_400)

Ya, but that ship was an actual hydrofoil. The foils act like wings to generate lift from movement. The thing in the OP uses movable pontoons, buoyancy, to haul itself up regardless of speed.

Note also that real hydrofoils angle their foils in parallel to the hull. It's essentially a dihedral effect like that of an airplane. As the ship lists one way, the foil on the downward side pushes more directly upwards, righting the ship. The 'foils' on the OP are mounted in the opposite manner, generating opposite effect. If they generated any actual lift the ship would flip instantly.

Sancoff began contemplating ways to give back to his country. To him, that meant shifting his focus from medical devices to weaponry.

That's a disappointing comment.

This thing looks like it could really turn the tide in our fight against Cobra.

Yeah too bad these stealth designs work like ass against WWII era long wave radar. Sure, you can't use long wave for targeting, but something this big sitting so high out of the water seems easy to hit with a shoulder fired rocket. It seems like these super high tech ships and aircraft exist mostly to create jobs in various congressional districts. Then the get sold on the mythology of a cold war nightmare scenario that never happened.

oh well. at least we're safe from COBRA.

"Hinges allow the struts to move up and down like wings. While parked, or traveling through shallow waters, they can be extended to the side."

Maybe you missed this while scanning the article. This would allow the boat to sit high or low on the water; reminds me of the citroen cx which had high adjustable suspension.

Another military device using supercavitation is the Soviet (now Russian) supercavitating torpedo:

https://en.wikipedia.org/wiki/VA-111_Shkval

Max speed is 200 knots (230 mph) and it can go for almost 10 miles. That seems almost unreal, an object that size, going at that speed under water.

There are numerous problems with this ship but the main reason why it won’t be used is that the US Navy already has a very similar ship that has been in testing since 2006 and is all around better than the vehicle in the article.

http://en.wikipedia.org/wiki/M80_Stiletto

50+ knots top speed, 4 x 1,650 hp engines

can carry a landing craft, 12 troops, and up to 20 tons of cargo

“A key feature of this vessel is that it can set up a network between a special forces team by launching an unmanned aerial vehicle (UAV) that relays information between the team and boat. The Stiletto can also carry surveillance UAVs to provide reconnaissance for the SEAL team, and, using a clustered supercomputer on board, will be able to send real-time images to the team on shore.”

Cost between $6 million and $10 million each.

For extremely stealth missions SEALs would use a underwater vehicle deployed from a C-130, another ship, or a submarine. http://en.wikipedia.org/wiki/SEAL_Delivery_Vehicle

“The 88-foot (27 m) long vessel has a notable hull design, an M-shaped hull that provides a stable yet fast platform for mounting electronic surveillance equipment or weapons, or for conducting special operations. The hull design does not require foils or lifting devices to achieve a smooth ride at high speeds in rough conditions. Its shallow draft means the M80 Stiletto can operate in littoral and riverineenvironments and potentially allows for beach landings. The faceted design suggests that the vessel has a low radar signature (i.e., stealth) in the frontal aspect and somewhat so from the sides.”

http://www.naval-technology.com/projects/m80-stiletto/

http://www.wired.com/2008/09/stiletto-vs-dru/

http://www.gizmag.com/stiletto-experimental-ship-with-carbon...

Also see ekranoplanes http://en.wikipedia.org/wiki/Ground_effect_vehicle

(And hydrofoils, I was very excited by hydrofoils when I was a kid)

http://en.wikipedia.org/wiki/Hydrofoil

Reminds me of the villains boat in Tomorrow Never Dies [1]

1: http://i.dailymail.co.uk/i/pix/2011/06/19/article-2005464-0C...

Which was based on the real Sea Shadow. http://en.wikipedia.org/wiki/Sea_Shadow_%28IX-529%29

Nothing like this will ever compare with a submersible in terms of "stealth". Who knows, maybe there already exists a supercavitating shallow draft sub for the spooks to use.

Detailed schematics here: http://www.rexresearch.com/sancoff/sancoff.htm

Isn't cavitation a bad thing when trying to be quiet in the water?

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