global warming definition. The term attached to the notion that the Earth's temperature is increasing due to the greenhouse effect. Note: Whether global warming is actually happening is a subject of scientific debate.
Like jet airplanes, space rockets work on a principle called action and reaction (another name for Newton's third law of motion). The massive force (action) generated by hot gases firing backward from a rocket's engines produces an equal force (reaction) that pushes the rocket forward through space.
A solid rocket booster on the X-51A will accelerate the test vehicle to about Mach 4.5, at which point the scramjet engine will kick in to push the vehicle toward 70,000 feet and Mach 6, according to the Air Force.