# How were the Space Shuttle and its External Tank connected (structurally)?

Source: Discovery Launch Captured by Multiple Cameras, NASA, YouTube; edited

A more clickbaity but accurate description of my question would be:

• How did the Space Shuttle / External Tank not shear off?

The view above always fascinated me. Note how once the ET is jettisoned, where it connects is revealed, and it is a small connector.

During lift-off I always thought of the SRBs carrying the ET, and the Shuttle carrying itself, but once the SRBs are jettisoned, and the acceleration is coming only from the Shuttle (thrust-line is now parallel more or less to the ET's vertical axis), I can only wonder how is that small connector possible; how is it designed to withstand such a shear force, yet remain with minimal footprint on the Shuttle underside / heat shield?

• Note that the much of the ET volume is liquid hydrogen, with a density about 1/14 that of water, and once the SRBs separate, it's burned about 1/4 of its contents, so it is somewhat less massive than it appears at a glance. A good question, though! – Russell Borogove Sep 11 '19 at 22:46
• The other connections are at least somewhat more substantial – CourageousPotato Sep 12 '19 at 1:21
• different but related: Shear forces between Shuttle, tank, and boosters - what pushes what? – uhoh Sep 12 '19 at 2:30

There were three attach points. The forward bipod that you show in your answer, and two aft attach points. At each attach point a large explosive bolt held the tank and Orbiter together. Large umbilical door openings in the aft of the Orbiter let the aft bolts pass through and also had all the fluid and electrical connections. After separation tile-covered doors closed over these openings.

• SSME's produced ~400,000 lbf of thrust for a combined 1.2M lbf will all 3 firing at 104%. The thrust of each individual SSME varied slightly based on the number of cores (basically picture a collection of ~ 100 straws through which the propellant mixture flowed) that were operative for each engine. – David C. Rankin Sep 13 '19 at 5:39