Reporters get 12 years labor in N. Korea prison: "Two U.S. journalists detained in North Korea while covering defectors living along the China-North Korea border have been sentenced to 12 years in labor prisons, the country's state-run media said today. The court sentenced Laura Ling and Euna Lee for the 'grave crime they committed against the Korean nation.'
"(Via CNN.com.)
Spy planes due in Afghanistan are late: "The Air Force’s delay in deploying MC-12W spy planes to Afghanistan could hamper a summer offensive planned against the Taliban, a spokesman for Defense Secretary Robert Gates said."
(Via Air Force Times - News.)
Remember Blue Thunder, the high-tech police helicopter from the eponymous movie and TV series of the early 80s? The one with the 'Whisper Mode' for silent flight? Well according to an eminent rotorcraft academic, aural stealth at the push of a button might just be possible. He calls it 'acoustic cloaking'.
Video: via Youtube
According to Dr Fredric Smith, professor of aerospace engineering at the Univeristy of Maryland giving the Nikolsky lecture at AHS Forum 65 in late May, there are two main kinds of rotor noise. Blade-vortex interaction (BVI) noise is the annoying one, caused by'each blade slicing through the tip vortex shed by the preceding blade. BVI noise is directed downwards and best mitigated by modifying the approach to put the vortices above or below the rotor.
The other main source is thickness noise, 'which is caused by the blade displacing the air and is directed in the plane of the rotor. This is the one that makes helicopters detectable at a distance, and the one you need to get rid of if you want a stealthy rotorcraft.
Prof Smith reported on recent tests that showed the shape of the acoustic pulse from thickness noise could be modified by controlling the drag force on the blade as it rotates. Using trailing-edge devices on the blade to control drag it's possible, at the point where the pulse is directed towards the observer, to generate an anti-noise pulse to cancel out the sound from the rotor. 'It's basically a beam,' he said. 'You can kill the noise in a certain direction.'
It's still early days in the research, nothing has been flown and the impact of drag control on rotor performance has not been established, he said. Also the technique is likely to send noise in other directions. But with helicopter manufacturers experimenting with active rotor control using on-blade flaps and slats, 'acoustic cloaking' could yet emerge as one of the key benefits.
"(Via Ares.)
UAV-based Missile Interceptors Reconsidered: "
The pursuit of Boost Phase Intercept (BPI) from unmanned aircraft is back after an 18-year pause for development of new generations of long-endurance aircraft and very fast interceptor missiles.
The advances demonstrated by new, faster, higher-altitude, larger-payload' UAVs' is revitalizing the concept of BPI - the tactic of striking enemy ballistic missiles within the first minute or so after launch.
With Sec. Robert Gates revamping national security strategy by budgeting for more unmanned airborne weapon systems, advocates of the UAV/BPI combination are rallying support for another effort, perhaps built around versions of Northrop Grumman’s Global Hawk or larger versions of General Atomics Aeronautical Systems' Predator, such as the turboprop B-model or the all-jet C-variant capable of carrying up to a 3,000-lb. payload of 2-3 very fast missiles - perhaps a variant of Raytheon’s NCADE/AMRAAM design - and advanced sensors linked to a sophisticated command and control systems and able to loiter near areas where mobile ballistic missile launchers operate.
Credit: General Atomics
During boost phase, the ballistic missile’s rocket engine produces a plume of heat and light that makes a huge target for high-speed defensive interceptor missiles. Supporters say it is the only effective way to guard against a single, nuclear-tipped missile, particular those aimed by Iran and North Korea at Israel, South Korea, Japan and U.S. forces there. The concept was examined when it was discovered during the 1991 Gulf War that none of Iraq’s mobile Scud launchers were found and attacked in time to prevent a launch.
Concepts developed in the post-war period included the U.S. Raptor Talon and Israel’s IBIS HA-10 but programs stalled over the lack of small, fast interceptor missiles. However, in the past 18 years, UAVs have gotten larger and interceptors have gotten smaller and ballistic missiles have proliferated which makes the concept interesting again.
(Via Ares.)
