In other words, you need to understand aerodynamics, and mechanics of friction related to gravity related to torque. And how they all relate to moving a ground vehicle up a slope ramp. Just knowing these basic relationships can help you get you ground vehicle in the air. I have learned about gear ratios and their relation to the linear distance the vehicle can travel. The type of string used on the rear axle is very important.
Fishing line is the best.
The axles and tires must, I say must, be frictionless if possible and the weight on the back must be heavy enough so the torque of the mouse energy is not lost. Configuration of mousetrap energy is important to get a even amount of torque at first then at the end of the ramp get a rush of torque to propel your vechicle off the ramp into flight. Because I wanted my wings wider to make for a better glider also using a 2 liter bottle vs a 1 liter bottle.