wolit@alice.UUCP (Jan Wolitzky) (05/31/85)
It appears that NASA has just discovered what owners of Grumman singles have known for years: that if you use differential braking for steering, you wear out your brakes real fast. The shuttle has sustained brake damage on all 17 landings to date. They use differential braking to steer since the nosewheel is controlled by a single hydraulic system, which doesn't meet their reliability requirements, and the split rudder is used for aerodynamic braking during landing. (Sounds just like a government decision, right? Use the rudder to brake and the brakes to steer.) They've finally decided to do it the other way around, starting with the next flight. I could almost hear the money wearing away whenever I had to use brakes to steer on my Cheetah. We'd go through a set of pads every hundred hours or so. We learned to taxi faster than we'd otherwise like, so the rudder could be used for steering. Interestingly, I have in hand the most recent copy of NASA Tech Briefs (an excellent publication, by the way, with loads of great ideas spun off from NASA's work), in which they describe a system, "developed for the shuttle," for using a split rudder for both steering and braking. They describe using two mechanical differentials for combining steering and braking inputs to control both halves of the rudder, but a hydraulic system (like the shuttle uses) would be even easier to design. Does anyone know whether the shuttle now can use the rudder for both functions simultaneously? -- Jan Wolitzky, AT&T Bell Labs, Murray Hill, NJ; 201 582-2998; alice!wolit (Affiliation given for identification purposes only)