Thursday, February 24 was the final launch for the Shuttle Discovery, which set off on its 39th flight. The final mission represents the end of an era for the space program, and the swan song for a shuttle that is absolutely steeped in gases and welding technology.
To start, the Discovery’s bright orange external fuel tank holds a total of 535,000 gallons of liquid hydrogen and liquid oxygen. The shuttle’s main engines burn the cryogenic propellants to accelerate from 3,000 mph to over 17,000 mph in a matter of six minutes to reach orbit. At that rate, you can bet the engines are burning the gas pretty fast. According to NASA, the engines consume liquid fuel at a rate that would drain an average family swimming pool in under 25 seconds. No wonder they need such a big tank.
As for the gas mix, the Space Shuttle’s main engines operate at a liquid oxygen/liquid hydrogen mixture ratio of 6 to 1 in order to produce 470,000 pounds of vacuum thrust. Because the gases are hydrogen and oxygen, the exhaust is mainly water.
A half million gallons of gas may seem like a lot, but that only accounts for the actual takeoff. NASA goes through a lot of gas in order to test the main engines as well. According to NASA, “Each time a shuttle main engine is test-fired for the 8-½ minutes it takes to launch a Shuttle into orbit, it burns 132,000 gallons of liquid hydrogen and 49,000 gallons of liquid oxygen.”
How does the gas get from Air Products to NASA for these engine tests? By tug boat, naturally. It’s a fascinating five-hour trek that Captain Rocky Pullman has been making for 32 years, and you can read about it here.
In addition to gases, the Discovery was the first shuttle to use longitudinal friction-stir welds on two of the liquid hydrogen tank barrels. Previously, the panels were joined by fusion welding, and the change made a significant improvement to the structural integrity of future shuttles.
As many times as Discovery has taken off into space, it’s always an amazing sight to watch the shuttle take off. And it will never cease to amaze me what we can accomplish with a little welding and a whole lot of gases. Check out a video of the launch below:
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