![]() ![]() Pulled by the moon's gentle gravity, the sphere would fall the remaining 1,100 feet to the surface, striking at a speed of about 75 mph. Ten seconds later, after slowing the lander almost to a hover, the rocket would burn out and be cast off. Attached to the capsule would be a solid-fuel retrorocket, which was to ignite when Ranger was 10 miles above the moon. ![]() The victor, by a surprisingly wide margin, proved to be blocks of balsa wood, oriented with the end grain radiating out around the sphere for maximum energy absorption.īy the summer of 1960, a 26-inch-diameter sphere weighing 92 pounds began to take shape at a division of the Ford Motor Company in Newport Beach, California. "All we were thinking about," he says, "was 'Let's get a transmitter down so we can prove we're there.' "īut how to protect sensitive scientific instruments from a crash as violent as an Indy race car hitting a concrete wall? To identify the best energy absorber, a variety of materials, including aluminum honeycomb, cardboard, and, in Burke's words, "anything crushable," were subjected to tests such as being dropped from a helicopter and slammed around with laboratory equipment. If this "survival package" seemed a less than elegant plan for humanity's first landing on the moon, Burke didn't mind. He and his team began talking about developing a rugged spherical capsule capable of withstanding such an impact. With all these uncertainties, Burke figured that Ranger might strike the moon at speeds up to 200 mph. Furthermore, nobody knew how to predict precisely how fast the spacecraft would be going relative to the moon, or even the exact location of the moon itself. No one could be sure a solid rocket would deliver the amount of braking needed to counteract all of the lander's excess speed. But the JPL engineers knew that solid rockets, while simpler than liquid-fuel ones, were also more unpredictable. Solid-fuel rockets were already being used in military airlifts to supplement parachutes when tanks and other massive objects were dropped out of airplanes. The best Ranger could do was fire a blast from a solid-fuel braking rocket to slow its descent before its lander simply fell to the surface-a "hard landing." But this so-called "soft landing" was beyond the reach of existing technology. Ideally the lander would settle onto the moon at only a few miles per hour. By the time Ranger reached the vicinity of the moon it would be traveling at 4,500 mph. ![]() But Ranger project manager James Burke and his team found that executing this task was anything but simple. In terms of physics, the concept for any lander is simple to describe: Just as it reaches its destination, it must undo the work of the launch rocket, canceling the kinetic energy the launch and the gravitational pull its destination give it. Early in 1960, NASA headquarters gave formal approval to JPL's Project Ranger. That was the goal of JPL director William Pickering, who pushed for a mission to deliver a package of scientific instruments to the lunar surface. Although the Soviets had, in September 1959, already hit the moon with their Luna 2 probe, a true moon landing had yet to be achieved. In the years after Sputnik, with the United States stinging from one Soviet space first after another, engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, dreamed of scoring a first of their own. It's an anxiety that began almost four decades ago, when the cold war was being waged in space. Of those five minutes, Spear says: "I don't know how I'm going to stand it."īut Spear is only the latest in a long line of engineers to face the uncertainty that precedes every robotic landing on another world. If it does not, Spear and his team of engineers and scientists-who labored for more than five years to create Pathfinder and send it to Mars-will shoulder one of NASA's greatest disappointments. If it survives, this robotic emissary, which was launched by a Delta rocket last December, will undertake the first exploration of Mars' surface in more than two decades. Just five minutes after speeding into the Martian atmosphere at 17,000 mph, the Pathfinder lander will strike the Red Planet. That's how long it will take for Mars Pathfinder to make this Fourth of July either a day of celebration or a day of sorrow for Tony Spear. ![]()
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