Only twenty-five years ago, the United States, following in the footsteps of the Ming emperors, abandoned its own pioneering program of space exploration. Even as the Apollo astronauts were returning from the Moon, the Nixon administration issued orders to effectively burn the fleet, destroying the Saturn V rockets and the other technological wonders that NASA had just developed to open the universe to humanity. At that time, America’s leaders could console themselves with the equivalent of the advice of the Ming court bureaucrats - exploration is too expensive, and nothing of value exists beyond what is already familiar.
Now we know better. The recent discoveries of numerous planets - potential homes for life - orbiting other stars, and of actual evidence for life on Mars, indicate forcefully that the universe is alive. Recent technological developments, ranging from demonstrations of prototype reusable launch vehicles to practical high-temperature superconducting wire, have made it clear that engineering solutions exist for all of the problems barring the way to establishing a spacefaring civilization. In other words, the universe is open - open for us, and open for others. Therefore, we must boldly face outward. To do otherwise is to knowingly stick our heads in the sand and accept the demoralizing notion of humanity as beings of a lesser order. To do otherwise is to abandon the tradition of pioneering - a tradition accepting of the challenge offered by new climates, new worlds, new technologies, and new ideas - that lifted humanity out of the Rift Valley and, more recently, gave birth to the dynamic career of Western civilization.
As John F. Kennedy said in 1961 when committing the United States to the race to the Moon: "A new ocean has opened and free men (and women) must sail it." The universe has presented us with its challenge. To remain who we are, we must accept. We must enter space.
Robert Zubrin | Entering Space: Creating A Spacefaring Civilization