Greetings and Salutations:

The aft of the Orbiter has been called "a plumbers nightmare" for good reason 
as the picture shows.

To give you an idea of the size of the aft, it is about 2 stories in height 
high.  Basically all of the metal colored lines in the aft are Main 
Propulsion System lines carrying cryogenic liquid hydrogen and liquid oxygen 
to the main engines and sending gaseous hydrogen and oxygen back to the ET 
(External Tank) to repressurize it during ascent.  Below is a description of 
the picture.  The pictures are scanned in 8X10 pictures taken from the 50-1 
door, left hand forward of the T-0 lines, side right before launch of OV-102 
Columbia.

Starting from the left, the small gray / metal line is the 2 inch GH2 return, 
to repressurize the ET.  This is to give you a reference size.  Next to it is 
the 4 inch recirc return line (4" is the internal size and does not include 
width between the inner and the outer vacuum jacket wall).  Above that is the 
bottom half of the 17" line that connects between the Orbiter and the ET.  In 
the middle of the page is the 8" fill / drain line that fills and drains the 
ET on the ground.  That goes to the manifold that branched down to the SSME's 
(Space Shuttle Main Engines).  On the bottom right of the picture is a shot 
looking down at E-1 (Engine 1 Center).  You can just barely see the LPFTP 
(Low Pressure Fuel Turbopump) connected into the MPS system.

The orange lines going everywhere are titanium lines covered with insulation 
from the hydraulic system.  The dark gray lines are PVD - purge vent drain 
ducts that route air during normal processing and GN2 during ET tanking.  The 
green color is Corpon, a corrosion protection paint that is basically an 
epoxy.

The pictures "aft01.gif" thru "aft07.gif" are the original scans of the 
pictures that made up the composite picture "aft.plumbers.nightmare.gif".  If 
you piece it together better, tell me & I will get it onto ames.

Ken Hollis
hollis@titan.ksc.nasa.gov