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Harrier Hovercraft

Precision Steered Hovercraft
 
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A normal hovercraft typically has one means of accelerating forwards or rearwards (a large propeller at the rear of the vehicle), and one means of steering (louvers behind the prop).

The Harrier Hovercraft still uses a propeller to move forwards, but instead of louvers to steer, it uses aimable attitude jets, similar to those used for VTOL operation on Harrier class airplanes.

A plethora of sensors (accelerometers, gyroscopes, doppler radar aimed at the ground below the vehicle) are used to determine the vehicle's velocity and rotational velocity relative to the ground.

When the rear of the vehicle starts to drift left or right, one of the two jets at the rear is used to precisely counteract that drift.

When the vehicle as a whole is turning at a rate that's either more than or less than that dictated by the pilot's steering wheel and the vehicle's forward speed, one of the front two jets is used to add to or counteract the turning speed.

Under ideal circumstances, these two effects together should allow the hovercraft to steer in a way that feels very much like a wheeled vehicle.

There would be four jet nozzles, one on each corner of the vehicle, aimed skywards. If the vehicle starts to lift off the ground and flip, these are used to counteract that rotation and bring the vehicle's attitude back to being parallel to the ground. This would only be necessary at very high speeds, or in very high winds.

To produce small amounts of deceleration, a clutch disengages the vehicle's propeller from the engine, and a brake is applied to the prop.

To produce a larger deceleration, hydraulic actuators deploy four retractable wheels, with brakes of course. The front two wheels would be swivel casters; this should not detract from the vehicle's handling, and avoid the need for a redundant steering mechanism.

Alternatively (and especially useful off-road) deceleration can be produced by spinning the propeller in reverse. This consumes more energy, but you can't expect wheels to slow you down when your hovercraft is on water.

goldbb, Aug 18 2011

Ground Effect Vehicles http://en.wikipedia.org/wiki/Ekranoplan
More wacky designs than you can shake a VSTOL at. Read up. [Alterother, Aug 18 2011]

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       [AO] GEVs have many the same downsides as hovercraft, namely they steer like planes, not like automobiles. You turn one, and it moves in a highly Newtonian manner -- it keeps going the direction it was, until thrust counteracts the original momentum.   

       Automobiles (and my idea) move in an approximately Aristotelian manner -- namely, if you change the direction the vehicle is pointing, it moves in the new direction. In a car, this is accomplished through wheels on the ground. In my idea, this is accomplished through attitude adjustment jets.   

       Also, typical GEVs bank to turn, whereas with my idea, turning is purely through a yawing action.   

       What kind of GEV use jets for steering? Or jets for flip prevention? Or wheels for on-road braking?   

       Or running the prop in reverse for high-speed braking?
goldbb, Aug 18 2011
  

       Several different types incorporate one or more of those concepts in some form; my point was that when in comes to GEVs, there are more designs than you can shake a VSTOL at. I will remove the 'baked' comment.
Alterother, Aug 18 2011
  

       I remember seeing a picture of a hovercraft with controllable louvers in the side of the rigid body. They were called "puff ports", I think.
baconbrain, Aug 18 2011
  

       The assault hovercraft used by the USMC use vectored thrust.
8th of 7, Aug 18 2011
  

       //deceleration can be produced by spinning the propeller in reverse. //   

       Why not have a variable pitch prop and put on netgative pitch.
TomP, Aug 18 2011
  

       //assault hovercraft// I'm sure it's all very manly and gung-ho, but "assault hovercraft" sounds like it should be in a Monty Python sketch, along with the Mobile Armoured Escritoire.
MaxwellBuchanan, Aug 18 2011
  
      
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