--- Randall Clague <[EMAIL PROTECTED]> wrote: > On Fri, 03 Oct 2003 10:20:44 -0700, Pierce Nichols > <[EMAIL PROTECTED]> wrote: > > Long burn time passively guided rockets have a > tendency to do rather > >extreme gravity turn maneuvers that result in lots > and lots of > >horizontal velocity at burnout. Hence, the slant > range and dispersion > >are greater. > > OK - this matches both my observations and my > intuition. But, I don't > see why this is so. Mathematically, it seems to me > that a gravity > turn is independent of whether the vehicle is under > power; and that , > second for second, the trajectory will look the > same, powered or not. > What is different is the proportion of the flight > that is powered. > > Can someone resolve this paradox?
Just a guess but, manufacturing error? As in, the vehicle isn't absolutely perfectly balanced. It's balanced within a certain margin of error, perhaps down to the lowest level one can measure, but there's imbalance beneath that threshold. Under active control, one scarcely notices: correct as if one were correcting for a bit of turbulence, so it seems little different from other noise in the system. Under passive control, though, it builds up: once you're pointing just a bit to the side, if your center of mass isn't exactly in the middle of the vehicle, drag will exert a net torque around that center - and whatever imbalance caused the initial rotation may be magnified. Or even with a perfectly balanced rocket, a small gust of wind can induce a torque, turning the rocket so drag alone can induce more. _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
