Editing Space Shuttle external tank (section)

===Liquid hydrogen tank===
[[Image:Sts et1.jpg|thumb|The {{convert|70|ft||adj=mid|-long}}, {{convert|17|in||adj=mid|-diameter}} liquid oxygen feedline runs externally along the right side of the liquid hydrogen tank up and into the intertank. Two {{convert|5|in|adj=on}} diameter re-pressurization lines run beside it. One supplies hydrogen gas to the liquid hydrogen tank and the other supplies oxygen gas to the liquid oxygen tank. They are used to maintain the [[Ullage (rocketry)|ullage]] pressure in each tank during the launch.]]
The LH<sub>2</sub> tank is the bottom{{efn|name=orientation}} portion of the ET. The tank is constructed of four cylindrical barrel sections, a forward dome, and an aft dome. The barrel sections are joined together by five major ring frames. These ring frames receive and distribute loads. The forward dome-to-barrel frame distributes the loads applied through the intertank structure and is also the flange for attaching the LH<sub>2</sub> tank to the intertank. The aft major ring receives orbiter-induced loads from the aft orbiter support struts and SRB-induced loads from the aft SRB support struts. The remaining three ring frames distribute orbiter thrust loads and LOX feedline support loads. Loads from the frames are then distributed through the barrel skin panels. The LH<sub>2</sub> tank has a volume of {{convert|53488|cuft}} at {{cvt|29.3|psi}} and {{cvt|-423|F}} (cryogenic).

[[File:Space Shuttle external tank assembly 01.jpg|thumb|Interior of a liquid hydrogen tank during assembly at the NASA rocket factory, with humans for scale]]

The forward and aft domes have the same modified ellipsoidal shape. For the forward dome, mounting provisions are incorporated for the LH<sub>2</sub> vent valve, the LH<sub>2</sub> pressurization line fitting, and the electrical feed-through fitting. The aft dome has a manhole fitting for access to the LH<sub>2</sub> feedline screen and a support fitting for the LH<sub>2</sub> feedline.

The LH<sub>2</sub> tank also has a vortex baffle to reduce swirl resulting from slosh and to prevent entrapment of gases in the delivered LH<sub>2</sub>. The baffle is located at the siphon outlet just above the aft dome of the LH<sub>2</sub> tank. This outlet transmits the liquid hydrogen from the tank through a {{convert|17|in}} line to the left aft umbilical. The liquid hydrogen feed line flow rate is {{cvt|465|lb/s}} with the main engines at 104% or a maximum flow of {{cvt|47,365|USgal/min}}.