The Space Shuttle is a good example of asymmetric launch vehicle. It required heavily-gimballing engines to keep everything balanced.

As a KSP enthusiast, I found that attaching the external tank to the nose of the Orbiter essentially solved that problem. But we know NASA never used such a design.

Why was the ET not aligned with the Orbiter ?

  • $\begingroup$ How do you separate the tank safely? $\endgroup$
    – GdD
    Commented Nov 8, 2019 at 13:43
  • $\begingroup$ What about the very long pipes from tank to engines? Where to place them? How to separate? How to acheive a constant bubble free flow without pogo problems? $\endgroup$
    – Uwe
    Commented Nov 8, 2019 at 14:23
  • 3
    $\begingroup$ Almost every configuration for the shuttle that you could imagine was considered at some point by NASA. The Space Shuttle Decision covers some of the considerations, especially chapter 8. history.nasa.gov/SP-4221/ch9.htm $\endgroup$ Commented Nov 8, 2019 at 16:35
  • $\begingroup$ In addition, NASA, has been very wary of having fuel tanks "above" people. This is part of the reason why the lunar lander was below the crew capsule. $\endgroup$
    – ghellquist
    Commented Jan 3, 2023 at 14:23

2 Answers 2


The best place for the tank is below the orbiter just above the engines.

This placement allows short and straight pipes from the tanks to the engines. All parts could be balanced and aligned. No heavy gimbaling necessary. Solid fuel boosters could be aligned parallel to the tank. Separation of the tank from the orbiter is as easy as a conventional stage separation.

The engines are not needed in orbit and for reentry, but they could not be recovered easily.

This placement was used for the never realized spacecraft Hermes.

Your placement of the tank above the nose of the orbiter requires too long and bend pipes. The heat shield at the nose of the orbiter is not a good place to connect the pipes and struts to the tank.

But the liquid cryogenic engines of the Shuttle should be recovered with the orbiter itself, so the tank could not be placed directly above the engines.

  • $\begingroup$ This doesn't answer the question, which was why the ET of the shuttle was not aligned. $\endgroup$
    – GdD
    Commented Nov 8, 2019 at 18:23
  • $\begingroup$ This placement is to be used for the never realized SLS as well. $\endgroup$
    – dotancohen
    Commented Nov 11, 2019 at 8:44

The original design concept was for the Orbiter to ride piggyback on a manned, reusable winged booster.

When budget realities forced elimination of the booster, it was replaced by the tank/solid booster combination, but the piggyback mounting was retained.

enter image description here

link to image source


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