The moon, a luminous disk in the inky sky, appears suddenly above the broad crescent of Earth’s horizon. The four astronauts in the Orion crew exploration vehicle have witnessed several such spectacular moonrises since their spacecraft reached orbit some 300 kilometers above the vast expanse of our home planet. But now, with a well-timed rocket boost, the pilot is ready to accelerate their vessel toward the distant target ahead. “Translunar injection burn in 10 seconds ... ” comes the call over the headset. “Five, four, three, two, one, mark ... ignition....” White-hot flames erupt from a rocket nozzle far astern, and the entire ship—a stack of functional modules—vibrates as the crew starts the voyage to our nearest celestial neighbor, a still mysterious place that humans have not visited in nearly half a century. The year is 2020, and Americans are returning to the moon. This time, however, the goal is not just to come and go but to establish an outpost for a new generation of space explorers.
The Orion vehicle is a key component of the Constellation program, NASA’s ambitious, multibillion-dollar effort to build a space transportation system that can not only bring humans to the moon and back but also resupply the International Space Station (ISS) and eventually place people on the planet Mars. Since the program was established in mid-2006, engineers and researchers at NASA, as well as at Lockheed Martin, Orion’s prime contractor, have been working to develop the rocket launchers, crew and service modules, upper stages and landing systems necessary for the U.S. to mount a robust and affordable human spaceflight effort after its current launch workhorse, the space shuttle, retires in 2010.
To minimize development risks and costs, NASA planners based the Constellation program on many of the tried-and-true technical principles and know-how established during the Apollo program, an engineering feat that put men safely on the moon in the late 1960s and early 1970s. At the same time, NASA engineers are redesigning many systems and components using updated technology.
Orion starts with much the same general functionality as the Apollo spacecraft, and its crew capsule has a similar shape, but the resemblance is only skin-deep. Orion will, for example, accommodate larger crews than Apollo did. Four people will ride in a pressurized cabin with a volume of approximately 20 cubic meters for lunar missions (six will ride for visits to the space station starting around 2015), compared with Apollo’s three astronauts (plus equipment) in a cramped volume of about 10 cubic meters.
The latest structural designs, electronics, and computing and communications technologies will help project designers expand the new spacecraft’s operational flexibility beyond that of Apollo. Orion, for instance, will be able to dock with other craft automatically and to loiter in lunar orbit for six months with no one onboard. Engineers are widening safety margins as well. In the event of an emergency during launch, for example, a powerful escape rocket will quickly remove the crew from danger, a benefit space shuttle astronauts do not enjoy. But to give you a better feel for what the program involves, let us start on the ground, before the Orion crew leaves Earth. From there, we will trace the progress of a prototypical lunar mission and the technologies planned to accomplish each stage.
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