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Wed November 26, 2014
"Houston, We Have A Problem"
SciWorks Radio is a production of 88.5 WFDD and SciWorks, the Science Center and Environmental Park of Forsyth County, located in Winston-Salem.
Every kid ‘gets’ that when you let go of the open end of an inflated balloon and it flies around the room, its speed is determined by the amount of air in the balloon. It really doesn’t take a rocket scientist.
However, this same principle of physics was used by a rocket scientist to save the lives of the Apollo 13 Astronauts. NASA’s Apollo program ran from 1961 to 1972, successfully landing 6 spacecraft and twelve astronauts on the Moon. The Apollo spacecraft consisted of 3 modules: 1) The command module was a home base, where the three astronauts lived during the mission. It was also their ride back to Earth. 2) The Service module provided power for the command module and the propulsion systems. 3) The Lunar Module was the craft that took astronauts from Apollo to the moon and back. It had its own power and propulsion systems. Apollo 13 experienced a life threatening problem well after launch, and it took a team of engineers on the ground to bring the crew home safely. North Carolina native Dr. Stokes Fishburne, was among those engineers.
At the time I was an aerospace engineer at Grumman Aerospace Corporation. Grumman built the lunar module.
So what happened that day in 1970?
They got about seventy five percent of the way to the moon when an explosion occurred in the service module, in one of the fuel cell supplies of oxygen that were needed to provide electrical power to the command module (and) to the Astronauts. They moved the astronauts from the command module, which was small and had very limited power, to the lunar module which had its own power supply.The lunar module had to provide the power (and) the rockets. It had to provide water for drinking, and all of the stuff which had not been counted on. NASA knew that they would then have to come up with a technique to separate the command module from the lunar module on the way back.
There were many problems to be solved in order to get the crew home alive. Dr. Fishburne and his partner Dr. Richard Oman were assigned to figure out how best to separate the lunar module from the command module just before reentry.
We needed some type of force to separate the lunar module from the command module to a sufficient distance that they would not collide with each other during the actual re-entry through the Earth’s atmosphere. Whatever process we developed could not employ any rockets or electrical power that was needed for maneuvering during reentry. The only force available was that which would be generated by the air in the lunar module. It would work like this: there are two doors between the lunar module and the command module. We would leave the first door from the lunar module, coming towards the command module, open. But we would close the door at the other end of the tunnel, so that the astronauts were still within their environment on the command module.
And this is where the flying balloon comes in. Or, to be more technical, the engineers applied Newton’s 3rd law of motion . Simply stated, for every action there is an equal and opposite re-action.
Then we put the right amount of air into the lunar module and at the proper moment the astronauts would release the latches that held the lunar module and the command module together. And the lunar module air would act like a big balloon. It would push the lunar module off in one direction and a blast from the air would push the command module off into the other direction hopefully with the right velocity to land properly. All we had to do was get the pressure in the lunar module 2.7 pounds per square inch, much, much less than the pressure we experience on the surface of the earth. That was enough to generate about two thousand pounds of force to separate these two spacecraft. The spacecraft was not light. The command module weighs about 13,000 pounds, and the lunar module weighs about 32,000 pounds. It’s not a trivial thing to separate these in opposite directions with exactly the velocity of about 5 miles an hour.
So, how did it all work out?
The command module, now the reentry vehicle, settled into the reentry and into the areas where we scheduled to be, the impact area, with safe astronauts and exactly on time. It’s a little tricky but it can be done with simple equations. It was the culmination of the old principal: if you got a job to do, do it right the first time. Thousands of engineers worked many many many problems in this whole Apollo 13 episode and they did it right the first time.