For centuries, scientists and engineers dreamed of going to the moon or the planets, but the more they learned about the problems involved, the more improbable space flight appeared.

While there were many difficult questions, the principal problem overshadowing all others was how to propel the vehicle free of the earth's gravitation.

When serious attention finally was devoted to the magnitude of the thrust required and the means for obtaining it, space flight became a real possibility. This assurance of adequate propulsion marked the true beginning of the space age, and continues to be the prerequisite for the more ambitious space flights planned for the future.