• E-mail
• Print
• Comment
• Font Size
• Digg
• del.icio.us
• Discuss article

NASA Craft Testing Hand-Off Docking System

Posted on: Monday, 11 April 2005, 18:00 CDT

A daylong NASA experiment with a brainy robotic spacecraft could rewrite the playbook for astronauts.

After rising nearly 500 miles, the Demonstration of Autonomous Rendezvous Technology spacecraft, or DART, will attempt a series of approaches to an orbiting satellite using a computer script.

If successful, the $110 million experiment might bring to an end a procedure NASA has used since the Gemini program in the mid-1960s. Since then, pilot astronauts have been responsible for bringing two orbiting spacecraft together. Those manual skills, which shuttle astronauts still rely on to dock with the international space station, were an essential stepping stone to the success of the Apollo moon missions.

The computer-smart DART spacecraft will attempt to duplicate part of the docking feat using technologies unavailable in the earliest days of space exploration. Relying on the military's Global Positioning System satellite navigation network and a new NASA laser ranging system, the 6-foot-long DART will attempt to maneuver within 17 feet of a high-velocity target.

Deep-space missions

DART is to launch over the Pacific Ocean aboard a Pegasus rocket at 12:25 p.m. CDT Friday. The slender rocket ignites after it drops from the wing of a jumbo jet cruising at 40,000 feet on a southerly course.

Automated rendezvous and dockings are considered an essential feature of NASA's Crew Exploration Vehicle, a shuttle replacement proposed as part of the moon and Mars exploration strategy outlined by President Bush last year. Those future deep-space missions will require the joining of several separately launched components into a single spacecraft in Earth orbit, after which the exploration capsule with a team of astronauts, guided by the rendezvous and docking system, would lift off to join the waiting interplanetary spacecraft.

"The goal of DART is basically to have an autopilot," said NASA's Jim Snoddy, the project manager. "DART is a technology development program that would enable the Crew Exploration Vehicle to... autonomously rendezvous and dock in space"

Following the Russians

DART's target is the Multiple Paths, Beyond-Line-of-Site Communications satellite, or MUBLCOM, an experimental military spacecraft that has circled the Earth since 1999.

MUBLCOM does not have a docking mechanism so it will not be possible for DART to actually link up. The Pentagon intends to include a docking demonstration in the unmanned Orbital Express mission planned within the next two years.

Though new to the U.S. space program, automated rendezvous is a staple of Russia's. The Russians have relied on a radar rendezvous system for decades to guide their Soyuz crew and Progress cargo capsules to a succession of space stations.

"Automated systems are valuable," said NASA's Charles Hobaugh, a pilot-astronaut. "I don't think you should become completely reliant on them, however. In my way of thinking, if the sensors are not working for you, the eyeballs are always the perfect backup. You still want to have the manual intervention if things are not going right."

Last October, a Soyuz capsule carrying two Russian cosmonauts and U.S. astronaut Leroy Chiao to the international space station encountered a last-minute failure. As he was trained to do, Russian pilot Salizhan Sharipov took manual control of the accelerating Soyuz and docked it expertly.

Multiple approaches

Work on the automated hardware began in mid-2001 at NASA's Marshall Space Flight Center. Part of the development effort included flight tests of the laser ranging components aboard two space shuttle missions.

DART is programmed to attempt about 50 close-proximity maneuvers over 24 hours, nearing the target satellite from below, swinging in front and over the top of the spacecraft, demonstrating collision avoidance and finally propelling itself away.

DART eventually will burn up harmlessly in the Earth's atmosphere.

-----

DART Mission

-----

To see more of the Houston Chronicle, or to subscribe to the newspaper, go to http://www.HoustonChronicle.com

Copyright (c) 2005, Houston Chronicle

Distributed by Knight Ridder/Tribune Business News.

For information on republishing this content, contact us at (800) 661-2511 (U.S.), (213) 237-4914 (worldwide), fax (213) 237-6515, or e-mail reprints@krtinfo.com.

More News in this Category