Effects of Drag on the Shuttle

The NASA diagram, shown above, depicts the four forces which act on an airplane in flight:  Lift and weight, thrust and drag.

How does drag (which became an issue for Columbia as it attempted re-entry on February 1, 2003) work, generally speaking?

Drag is the force which tries to slow down a moving object.

"To lessen the drag that an airplane feels, most airplanes are made more aerodynamic, or streamlined, to reduce the amount of drag they feel.

"A streamlined airplane has smooth surfaces and no bumpy sections, causing as little resistance to the air as possible."

Just like lift and weight are opposing forces, thrust and drag oppose each other. To stay aloft, and safely fly, an airplane's thrust (its forward energy produced by its engines) must be greater than its drag.

Credits

NASA Diagram.

Information and quoted passage, courtesy NASA's Glenn Research Center.