From: mikkelhaaheim@gmail.com   
      
   Le vendredi 11 novembre 2016 00:33:11 UTC+1, A Random Person a écrit :   
   > Let's say a torch missile (or anything) is on an intercept trajectory   
   towards a target.   
   > If the target makes a burn to counter, would it necessary take the same   
   amount of delta-v for the missile to keep the intercept?   
   >    
   > I suspect that it's a tradeoff between efficiency of plane changes and   
   oberth effect gains.   
      
   There are a lot of facters involved here, including (but definitely NOT   
   limited to) the initial velocities of both the target and the missile, the   
   performance capabilities of both (T/W ratios, Isp, propellant reserve, etc),   
   initial distance, initial and    
   subsequent closing rate (relative velocity), etc. Combat pilots frequently   
   refer to "missile envelopes", which not only determine how much energy a   
   missile must spend to hit a maneouvering target, but also the limits where   
   interception is even possible.   
   Yes, there are prefered trajectories, depending upon a specific envelope. Not   
   only is it not necessary for target and missile to expend the same delta-Vs,   
   but it is fairly rare that they will expend the same delta-V. Of course, it is   
   entirely possible,    
   if not probable, that the missile will have to expend more delta-V than the   
   target (especially if the target changes vector just prior to an expected   
   impact).    
   As a rule, IF possible, the best vector would be a leading intercept, where   
   the missile follows a straight line course to where the target is going to be,   
   rather than to simply remain pointed at the target all the time. This is   
   difficult with a    
   manoeuvering target. However, IF the flight envelop of a target is known, you   
   can at least reduce the amount of corrections (for instance, a target might be   
   travelling too fast to simply stop and turn, so you can be fairly confident in   
   a minimum lead    
   intercept vector).   
   Also, as a rule, the slower an object is moving, the less delta-V is required   
   to correct for an intercept course. The probem here is that too slow a   
   velocity could allow for a much easier escape. I recommend the book "Fighter   
   Combat: Tactics and    
   Maneuvering" by Robert Shaw.   
      
   Of course, things get MUCH more difficult when you take differing orbits into   
   account.   
      
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