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Tuesday, July 21, 2009
Draper fetes Apollo engineers, touts new moon landing tech
By Rodney H. Brown
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More than 100 former Apollo program engineers returned to Charles Stark Draper Laboratory Inc. yesterday to help the contract engineering firm celebrate the 40th anniversary of the height of the Apollo program, the first landing of a man on the moon.
Among the speakers at the event was Eldon C. Hall, who was in charge of developing the guidance computer for the Apollo lunar mission. With the announcement in 1962 that the U.S. would land a man on the moon in less than a decade, the engineers tasked to develop the various systems were, Hall said understatedly, under “time constraints.”
One of the biggest challenges they faced in such a short window, he noted, was reducing technology that filled rooms in the 1950s to a box about a foot square and six inches deep by the end of the ’60s.
Also on hand was Don Eyles, a former principal engineer in the Draper Apollo program, who helped solve one of the biggest problems with the Apollo 11 landing and fixed a problem with Apollo 14, both of which were issues that could have aborted a lunar landing.
When Apollo 11 landed on the moon, its computer was being flooded with bad data that caused much of its CPU cycles to get used up — as much as 13 percent at one time, Eyles said. The only solution was to essentially reboot the computer, which they did five times while the lunar excursion module was descending toward the moon’s surface.
“I probably would have called for abort,” Eyles said, but the staff at NASA has already run simulations of whether or not the lander could land successfully if it had lost that much CPU time, and discovered it could, so no abort command was given and Apollo 11 made its historic landing.
Eventually, another Draper Apollo engineer, George Silver, discovered that a switch for a radar system that was supposed to be off had been turned on by Edwin “Buzz” Aldrin, and it had been sending such bad data to the computer that it had caused the failures.
On the Apollo 14 mission, Eyles himself found out how to work around the fact that an abort switch kept reporting it was failing, as the lunar excursion module was getting ready to land. That also could have caused the computer to abort Apollo 14’s landing on the moon, and Eyles eventually wrote a software workaround that allowed the mission to go forward.
Draper took advantage of the anniversary to tout its latest moon technology for NASA. Like with the Apollo program, Draper is developing the guidance, navigation and control system for the proposed lunar lander, the Altair. Unlike the Apollo LEM, the Altair is designed to be able to take off after landing and “hop” to a new location elsewhere on the lunar globe for further research, according to Tye Brady, technology director for lunar landing at Draper.
To allow the lander to hop around on the moon, Draper is developing the Autonomous Landing and Hazard Avoidance Technology (ALHAT), a system that uses LIDAR to map the terrain below the lander in fine detail. Draper’s ALHAT allows the astronaut crew to go from complete computer control of a landing to complete manual control — but ideally some combination of the two, Brady said.
Draper has run 20 to 30 people through its prototype simulated control cockpit, and Brady said it is no surprise that the astronauts do much better than most people.
“I usually run out of fuel,” Brady said.
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