<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Where can we find some real information about this faulty re-entry. How can a module like the Soyuz reentry module make anything BUT a ballistic reentry? Doesn't a lifting reentry require something remotely resembling wings? <br />Posted by JimL</DIV></p><p>Soyuz spacecraft, like Gemini and Apollo, have their center-of-mass ("center-of-gravity" or "CG") offset from the physical center axis of the spacecraft. As a result, the vehicle does not point in the same direction as the velocity vector. In other words, it is flying at a skewed angle. The result is that the blunt end tends to develop a lift component. If the lift component is up relative to the direction of flight, the spacecraft tends to extend its range, if held in that attitude. If the vehicle is rolled so the lift vector is pointed toward the Earth, the range will be decreased dramatically. If the lift vector points to the right relative the flight path, the spacecraft will curve to the right, and similarly to the left. Now you can guide the vehicle by rolling the spacecraft one direction or the other. If you roll continuously, the spacecraft will effectively "corkscrew" around its long axis, enough so it goes into a pure ballistic re-entry path. Apparently, the Soyuz guidance system is programmed to go into the continuous roll as a default if things aren't going according to plan. Recall what Peggy Whitson said about it rolling continuously.</p><p>So far as finding out what caused the anomaly is concerned, that will have to come from the Russians. It's their "bird". As I've posted elsewhere, it may be something as "simple" as a quality control issue with the explosive bolts. Too hard a heat treatment on the bolt's steel might raise the tensile strength of the bolt, making the charge insufficient to break it. On the other hand, it could be something involving multiple conditions that caused the separation to not be clean. As much as I, too, am very curious, we'll just have to wait for the reports.</p><p> Ad Luna! Ad Ares! Ad Astra!</p>