At the recent SolidWorks World 2011 in San Antonio, Tex., a striking keynote wowed the audience by describing the “old days” when engineers might use nothing but their wits to triumph over a high-pressure situation. Apollo 13 Mission Control Director Gene Kranz and Captain Jim Lovell took turns to describe, in a direct and stoic manner, how thinking on their feet and staying fearless helped save the astronauts’ lives.
High-tech accidents are not usually a result of a single event, but of a series of happenstances and this was the case with the Apollo 13 journey, says Kranz. “For example, the cryogenic tanks containing oxygen and hydrogen housed fans to stir the contents,” he says. “About 200,000 miles out, under orders, the crew turned on the fans. Soon after, an explosion ripped through the ship’s command module, the cabin that housed the crew and had equipment for re-entry and splashdown.” The explosion also emptied the air supply in the service module, the portion of the ship that provided propulsion, electrical power, and storage for consumables. The ship was thus almost powerless and losing oxygen quickly. This situation led to Lovell’s now-famous remark to ground control, ‘Houston we have a problem.’” The trip was aborted but the problem remained how to bring everyone home safely.
Command control decided to use the gravitational forces of the Moon along with the small amount of the ship’s remaining propulsion to “slingshot” the craft back to an Earth orbit, says Kranz. “We quickly had to figure-out how to hook together the command module’s square carbon-dioxide-scrubber cartridge to fit the lunar module’s round cartridge. The lunar module is the landing portion of the spacecraft. We rigged the stuff together with a metal box and duct tape.”
The crew was then to perform mid-course maneuvers using rangefinder marks on the porthole, which they lined-up with Earth. Each member was to pull a handle, helping steer the craft towards the correct re-entry angle. “But when I looked around, everyone was too busy taking pictures of the dark side of the moon,” says Kranz. “A gentle reminder about floating forever frozen in space soon brought everyone to task. History tells the rest: Landing on the Moon was aborted but because we returned to Earth safely, NASA called the trip a ‘successful failure’.”
After the craft had returned, it was determined that the explosion also came about partially because of poor thermostat design — an issue that had actually gone unnoticed in previous space flights. The original thermostats had been designed for a 28-V dc bus. This was later changed to 65 V to pressurize the tanks more rapidly. But the tank subcontractor failed to upgrade the design, so the temperature sensor could not read above the highest heater operational temperature, about 100 °F — a necessary capability in this case.”
Lovell says it’s doubtful that highly risky, life-threatening ventures like this could happen today. “But the mission taught good engineering skills that carry into the future,” he says. “Most importantly, develop intense listening skills. Keep your mouth shut until you hear what others on your team have to say. Know everyone on your team well. You should also keep abreast of technological breakthroughs, important because they always predate sociological advances.”