A comment below this answer to my question "Runway landing with a front skid instead of wheel - how does steering happen? (Dreamchaser)" says:

In fact, the Space Shuttle didn't originally have nosewheel steering. It was added after brake damage incidents.

If this is so, at what point in the Shuttle's development, testing, and extensive flight history did this happen? It seems like adding a complete, reliable nose wheel steering system to a mature design would be quite an undertaking.


That comment is incorrect, the Orbiters always had a nosewheel steering system (NWS).

Perhaps the author is remembering that the original system was inadequate: it was zero-fault tolerant for loss of hydraulic pressure, for one thing. It was redesigned after the Challenger failure (as were many of the Orbiter systems, including the brakes) to remove inadequacies in its design.

A diagram of the original system can be found in the 1982 press manual.

enter image description here

The text-only version of the 1988 update to the press manual has a terse description of the modifications:

The nose wheel steering system was modified on Columbia (OV-102) for the 61-C mission, and Discovery (OV-103) and Atlantis (OV-104) are being similarly modified before their return to flight. The modification allows a safe high-speed engagement of the nose wheel steering system and provides positive lateral directional control of the orbiter during rollout in the presence of high crosswinds and blown tires.

The Shuttle Crew Operations Manual gives a schematic of the upgraded system showing the addition of Hydraulic System 2 for redundancy. You can see from the diagram that this had the added bonus of providing hydraulic redundancy for nose gear deploy. (The main gear was only deployed by hydraulic system 1, and had a pyrotechnic backup release system).

enter image description here

The "Direct" mode of the system - which put the system in a non-fly-by-wire mode and controlled the steering directly from the rudder pedals - was removed and replaced by a redundant avionics system. You can see in the yellow picture above that the original NWS switch gave the commander a choice of GPC/Direct/Off (where GPC is the computer-supported mode). The picture below shows the switch to control the upgraded system, where the choices are System 1/System 2/Off.

enter image description here

The linked manuals have extensive descriptions of the original and upgraded system should you wish further reading.

  • 1
    $\begingroup$ Great! I had a hard time believing that differential braking of the Space Shuttle's wheels would ever have been the only way to steer the thing after touchdown. $\endgroup$
    – uhoh
    Aug 10 '18 at 13:33
  • 1
    $\begingroup$ Good intuition! The original system was really bad though and since the brakes were bad too, it wasn't a good situation. $\endgroup$ Aug 10 '18 at 13:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.