To begin the flight a sailplane must achieve its initial height (potential energy).
Launching a sailplane is done with the use of some outside energy.
There are two predominant means of launching a sailplane: aerotow and ground launch .
Aerotow involves towing a sailplane to a suitable altitude behind a powered aircraft. At he tail of the towplane is attached a 200 foot rope to a hook located in the nose area of the sailplane. As the towplane climbs it pulls the sailplane up with it and both pilots fly in formation. At a suitable altitude, the sailplane pilot releases the tow rope and flies away. The tow rope remains attached to the towplane as it returns to the ground.
WINCH LAUNCH :
A ground launch usually involves a winch . The winch has several thousand feet of cable attached to the sailplane's center of gravity, usually located under the nose of the sailplane. As the winch reels in this cable, the sailplane starts rolling, gets air flowing over its wings, generates lift, and takes off. The sailplane climbs at a very steep angle, similar to launching a kite. At altitude, and while there is still 1000+ feet of cable or more left, the sailplane pilot will release the rope and fly away.
Another form of ground launch is an auto launch . The method is similar to the winch launch, but where as the winch is stationary and winds the cable in, the autotow involves forward motion by a vehicle pulling the sailplane
SELF LAUNCHING GLIDERS