ET-137 being loaded into Pegasus. Click for a larger version. Image credit: Lockheed Martin / Michoud Operations

The next to the last External Tank for the shuttle shown here being loaded into a barge after leaving at the Michoud Assembly Facility and bound for the Kennedy Space Center.

The External Tanks are way too large to be moved over the highway or rail systems so they are moved by an enclosed barge called the Pegasus.  The tank was actually loaded on the first of the month but high winds delayed the departure. The journey is about 900 miles and will take six days to accomplish.  The tank will arrive on May 9, 2010 and will be mated to the shuttle Atlantis for the scheduled May 14 launch date.

The final ET is being built and is scheduled to be completed next month.  Another tank called ET-122, damaged in Hurricane Katrina, is being constructed and it is a “spare launch on-need” tank.  These will mark the end the tank building activities for Lockheed Martin after building 133 tanks over 29 years.

There is a website for Michoud Operations with more (and larger) images and links to some pretty interesting PDF files.  One of the files, titled: Space Shuttle External Tank Statistics and Comparisons, I found to be especially interesting.

Here are some highlights:

• The tank is 154 feet (46.9 m) long with a diameter of 27.6 feet (27.8 m).
• The tank supplies propellant (liquid Oxygen and Hydrogen) at a rate of 1,035 gallons per second.
• The propellant temperature: Liquid Oxygen -297^oF (-183 C) / Liquid Hydrogen -423^oF (-253 C)
• The foam covering the tank is only about one inch thick (2.54 cm), yet it protects the super cold propellant insulated from the aerodynamic friction that can heat some parts of the tank to 1,800^oF (982 C)
• The aluminum skin of the tank is less than 0.5 inches (1.3 cm) thick.  Of course it’s a special alloy of aluminum and not like a soda can.
• The ratio of the tank weight to the weight it can carry is 1:27 compared to a “standard” pickup of 3:1.

So, I wonder what is to become of the employees at Michoud?  I wish them the best of luck.