this question How much of a rocket's energy is used to achieve altitude vs horizontal velocity? addresses the energy split of kinetic vs. potential energy to get to space - and to stay there.

We know, that the potential energy is a piece of cake vs. the kinetic energy needed. However, still rockets are launched from Aircraft. And while this has other advantages (weather independence, flexibility of launch location), I wonder how much energy is saved that would otherwise be needed to overcome aerodynamic drag.

Obviously, this depends on the aerodynamic characteristics of the launch vehicle. I found in literature a CD of 0.5, which should probably fit most rockets. But then, I am lacking the velocity/altitude profiles.

Can someone provide an approximate relation between Ekin Epot Edrag ?

Best regards, Hendrik

  • 4
    $\begingroup$ We typically talk in terms of delta-v, change in velocity, rather than energy, for launchers. See this post for the delta-v cost due to air drag for a launch to LEO. space.stackexchange.com/a/49596/6944 $\endgroup$ Jan 20 at 23:26
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    $\begingroup$ I've done some crude sims on this and in delta-v terms drag loss is about 1-2% of total delta-v expended. $\endgroup$ Jan 21 at 0:16
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    $\begingroup$ I've heard "gravity drag" takes 0.5 to 1.5 km/sec of delta-v. Direct aerodynamic drag will be way less, but the cut in thrust in most launch programs near max-Q due to aerodynamic pressure will have a gravity drag penalty that perhaps could larger than direct aerodynamic drag. $\endgroup$
    – uhoh
    Jan 21 at 1:29


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