It's an Airplane. It's a Submarine. It's Possible?

It's an Airplane. It's a Submarine. It's Possible?: "

Why DARPA thinks a submersible aircraft could be feasible has become'a little clearer with the posting of a presentation on the agency's website. Basically DARPA believes that, rather than'asking for'a flying submarine, by specifying an aircraft that can submerge to shallow depths for short periods it might be possible to reconcile the diametrically opposed design requirements. So it won't look like this...

SkyDiver, from Gerry Anderson's UFO

DARPA is seeking concepts for an aircraft that can clandestinely insert and extract an eight-person special-forces team.'The mission'is to'take off from a runway, fly 1,000nm as a conventional aircraft, fly another 100nm close to the surface, then'travel the final 12nm to the coast underwater. Transit'should'take less than 8'hours, including any time required to land on water and reconfigure'from aircraft'to submarine -'and the vehicle should be able to loiter near the coastline - on or under the surface - for three days in sea state 5. Then return the same way...

(The observant among you might recognise the submersible aircraft in'DARPA's mission profile - it's the Flying Sub from the TV series Voyage to the Bottom of the Sea.)

DARPA identifies five technical challenges. First is the'diametrically opposed'weight requirements'between an aircraft that needs to be light to fly and a submarine than needs to be heavy to submerge. DARPA believes it should be possible to meet these requirements by controlling lift and volume - potentially by generating downforce on the wing and flooding spaces in the airframe to submerge.

The second challenge is to design a shape that works in air and water despite the difference in density. Here the key is that flows are similar in both fluids if something called the Reynolds Number (Re) is the same. DARPA believes it is possible to design a platform that operates at the same Re, airborne and submerged, but at radically different speeds: 100-400kt in air and 5-18kt in water.

1934 - Ushakov's LPL (photo: Unicraft Models'- and check out'this video)

Challenge three is structural - aircraft are pressure vessels with thin skins; submarines have thick skins to withstand crushing loads: the forces are applied in opposite directions. But DARPA believes this problem is dramatically reduced by limiting operating depth to the minimum required to avoid perturbing the surface.

Fourth is wing location. Traditionally seaplane wings are placed high to avoid the waves and shield the engines. Lowering the wing'increases ground effect'while sea-skimming. But the wing'needs to be below the water to generate the downforce required to submerge. DARPA sees a range of possibilities ranging from two separate wings, one for air and'one for water, to a single morphing wing able to change its height, area and airfoil.

1958 - Reid's Flying Submarine (US Patent & Trademark Office)

The final (?)'challenge is the powerplant, which must work submerged as'well as'airborne. Aircraft engines are light; submarine powerplants are heavy. One option is a single engine with air-independent and air-breathing modes. Another is dual powerplants, one breathing air and one running off batteries, fuel cells or DARPA's Aluminum Combustor. The agency believes the shallow depth required will allow use of a snorkel'to provide air to the engine when submerged.

Bidders for the Submersible Aircraft program face related challenges: they must provide not only a detailed description of their proposed concept, but a plan for computational or experimental work that will demonstrate the feasibility of their design in the areas of weight and volume, operation in air and water, structural design, wing geometry and power generation/energy storage. Sounds 'DARPA-hard' to me.

1962 - Convair's subplane (thanks to secretprojects.co.uk)

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(Via Ares.)

Calspan Retires USAF's Last C-131

Calspan Retires USAF's Last C-131: "

A unique aircraft has just retired -'the NC-131H Total In-Flight Simulator (TIFS) owned by the U.S. Air Force Research Laboratory and operated by Calspan. With its unmistakable profile, the heavily modified Convair 580 made its last flight on Nov. 7 from'Niagara Falls'to the Air Force museum at Wright-Patterson AFB, Ohio.

TIFS as it first flew (1000aircraftphotos.com, Van Tilborg collection)

It's hard to understate the contribution the TIFS has made to aircraft design. With the ability to simulate the cockpit environment and control responses of'virtually any'type of air vehicle, the TIFS has played a role in programs ranging from the B-1 and C-17 to the X-29 and X-40. It has simulated the flying qualities of Tacit Blue, the Space Shuttle, a supersonic transport and a million-pound aircraft.

Conceived in the late 1950s to help with design of the hypersonic X-20 DynaSoar, the TIFS was launched in 1966 as a joint USAF/FAA program. The aircraft was to have two interchangeable noses:'one a general-purpose'proboscis for what became the B-1 program; one the droop snoot of a civil SST, which was never built because the program was cancelled. The TIFS started flying in 1968, direct-lift and side-force controls providing the ability to adjust its handling characteristics.

Calspan has a great history of its in-flight simulation work on its website. It started in 1949 with a Vought F4U-5 Corsair modified with an auxiliary rudder to vary yaw stability, and continues today with'the company's'variable-stability Learjets and the VISTA F-16 based at the USAF Test Pilot School and supported by Calspan.

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(Via Ares.)

Nuclear Watchdog Publishes Report on Alleged Syrian Nuclear Site

Nuclear Watchdog Publishes Report on Alleged Syrian Nuclear Site: "

Investigators from the International Atomic Energy Agency, which works under the auspices of the United Nations, reported having found traces of enriched uranium in Syria, at Al Kibar, the same site which was allegedly bombed by IAF jets in September 2007.

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The find offers a first potential sign that the country had been attempting to develop a nuclear program.

Sources close to Israeli intelligence agencies report that even if the uranium traces actually found at the bombed site were only slight, but clearly being man-made and not natural ore, they totally refute persistent claims by president Bashar Assad, that the installation at Al Kibar was only an agricultural research station. Moreover, foreign 'visitors', believed to be North Koreans, would have a single reason to be there and that was to inspect local construction work in progress on a nuclear reactor. Syria has repeatedly denied any secret actvity on energy for atomic bomb purposes in violation of the Non-Proliferation Treaty. It says the unverified US intelligence was fabricated. But the IAEA has been probing into US intelligence allegations that Syria was close to completing a plutonium-producing nuclear reactor with North Korean help.

In September 2007 the Israeli Air Force flattened the site in it's mysterious foray into Syrian airspace under the so-called operation 'Orchard', which was carried out on a target in the Deir ez Zor region, close to the Iraqi-Turkish border after midnight on September 6, 2007. Israel keeps an official blackout on the operation, but the CIA declared that US intelligence, having apparently monitored the site for some time, through satellite observation, indicated the site was a nuclear facility under construction, with a military purpose.

For details see: Fulghum, David A 'U.S. Electronic Surveillance Monitored Israeli Attack On Syria', Aviation Week & Space Technology, 2007-11-21.

Photo: US official

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(Via Ares.)

Red Flag Briefing Videos Disappear

Red Flag Briefing Videos Disappear: "

Two video clips that showed an off-the-record briefing by a senior F-15 pilot to retired generals on the latest Red Flag exercise seem to have disappeared from their original place on YouTube.

The discussions included some interesting, possibly classified, and certainly embarrassing details about fighting against the F-22, as well as the performance of the Indian air force’s Su-30MKI and the French air force’s Rafale in September’s Red Flag exercise (Aerospace DAILY, Nov. 6).

But don’t despair, the videos can still be seen on an Indian posting that’s also on YouTube -- http://www.youtube.com/user/IIindianII.

The video segments of most interest concerned a weakness that U.S. F-15 pilots found in mock combat with both the F-22 and the Su-30MKI. When either of the latter aircraft go into a post-stall, thrust-vectoring maneuver too aggressively, it provides a fleeting opportunity for a conventional aircraft to make a quick,' downward, vertical maneuver and close head-on for a single-pass, cannon-range engagement.

A long-time F-15 pilot tried to put the maneuver and its implications into perspective.

‘Air-to-air combat is all about maintaining more energy than your opponent,’ he says. ‘If a young pilot is overly aggressive, he can fly [a thrust-vectoring aircraft] into a place where’s he’s energy deficient,’ he says.

That means a rapid change of direction has turned into a post-stall maneuver. With the F-22’s two-dimensional thrust vectoring, the aircraft can still climb, but slowly. An F-16 or F-15 ascends vertically then flips into a dive directly at the Raptor before it can get its nose (and cannon) pointed at the attacker.

The Su-30MKI has three-dimensional thrust vectoring that is less efficient because the much larger aircraft creates so much drag that the aircraft starts sinking rapidly. The attacker doesn’t have to climb,' it simply rolls into the vertical attack.

Opponents with an altitude advantage, even if they’re flying a conventional aircraft, can attack while the thrust-vectoring aircraft has slowed to turn its nose toward the attacker. ‘If you’ve maintained [your high energy], for a moment there is an opportunity,’ the F-15 pilot says.

The USAF pilot says that as soon as the younger pilots learn to avoid getting excited and stay out of the low-speed turn, they’ll start beating the U.S. F-15s and F-16s with regularity because the Su-30MKI is a more capable aircraft than an F-15 or F-16 with a conventional radar.

The clips also had the U.S. pilot expressing his opinion that French pilots flying Rafale with sophisticated avionics used the event to gather electronic intelligence about the Su-30MKI’s Russian-built radar.

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(Via Ares.)

Exclusive: Inside a U.S. hostage rescue mission

Exclusive: Inside a U.S. hostage rescue mission: "The American businessman lay shackled in a mud hut 8,000 feet up a remote mountain in Afghanistan, armed captors posted inside and outside to prevent any escape attempt."

(Via Air Force Times - News.)