1000 lbs at 25/1 Lift to drag needs 40 pounds of thrust to remain in
level flight. Any thrust above that number would result in either
climb or a faster level speed. So in theory, using those numbers,
40.0000001 pounds of thrust would get the job done - eventually. 100
pounds of thrust (2 large model turbines) would probably give a
reasonable rate of climb for a self-launch.

Rather than do all the math just download a demo version of X-plane,
add a jet to the glider and see what happens. www.X-plane.com

Just remember that the simulation is no better than the data fed into
it............................
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Leon McAtee