On September 12, 1962, then US president John F Kennedy informed the public of his plan to put a man on the Moon by the end of the decade.

It was the height of the Cold War and America needed a big victory to demonstrate its space superiority after the Soviet Union had launched the first satellite and put the first man in orbit.

"We choose to go to the Moon," Kennedy told 40,000 people at Rice University, "because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win."

Sixty years on, the United States is about to launch the first mission of its return program to the Moon, Artemis. But why repeat what has already been done?

Criticism has risen in recent years, for example from Apollo 11 astronaut Michael Collins, and the Mars Society founder Robert Zubrin, who have long advocated for America to go directly to Mars.

Today NASA uses wheeled rovers to navigate the surface of Mars and conduct planetary science, but research involving Texas A&M University scientists will test the feasibility of new surface-exploration technology: walking robots.

Ryan Ewing, Robert R. Berg Professor in the Department of Geology and Geophysics at Texas A&M, and Marion Nachon, associate research scientist in geology and geophysics, are co-investigators on the project supported by NASA and led by Feifei Qian, a WiSE Gabilan Assistant Professor at the University of Southern California Viterbi School of Engineering. The aim of the research is to create and test walking, or "legged," robots that could more easily glide through icy surfaces, crusted sand and other difficult-to-navigate environments, thus significantly enhancing scientists' abilities to gather information from planetary bodies.

While the Mars Exploration Rovers and other robots have been successfully sent into space, they typically operate based on pre-programmed agendas that require human scientists and engineers to input detailed instructions regarding where to go and what to do prior to the robots' arrival at the planet.

Earlier this week, the Artemis I moon mission was scrubbed again; now we have to wait for a new launch window.

Just 40 minutes before the Space Launch System rocket was set to take off from Kennedy Space Center in Florida on September 3, a leaking fuel line caused engineers to scrub the launch.

So what is a launch window, and why can't a rocket go up at any time? And what does it mean to "scrub" it?

Waiting for the right alignment

A launch window is like waiting for the stars to align. The rocket will be "thrown" off the surface of Earth. This toss must be timed perfectly so the craft's resulting path through space sends it—and everything it's carrying—towards the intended location at the right time.

For Artemis I—a mission to send the Orion capsule into orbit around the moon—the "right time" means waiting for the moon to be as close to Earth as possible (known as "perigee") during its 28-day cycle. Hence why we'll now be waiting roughly four weeks for the next moonshot.