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Slender bodies like arrow shafts, airliner fuselages, and submarine hulls are all capable of generating lift, albeit much less efficiently than a high aspect ratio wing. They also generate little drag, which is their main advantage. I would like to know how their lifting properties compare to that of a wing; to this end I would like to refer to a use case where the slender body makes up most of the airframe: guided missiles.

Luftwaffe MiG-29 firing an R-27

Consider a missile with a long slender body and short lifting surfaces, with a "conventional" air to air missile aspect ratio like that of the R-27 or AIM-120. The exact wing and control surface layout is not relevant, only the form factor. This means we should purposefully exclude munitions equipped with a moderate aspect ratio wing such as the TLAM or JSOW: I am interested in low aspect ratio BVR designs:

AIM-120

R-73, R-60, R-27T and R-27R missiles

AIM-54A

To avoid complications due to the engine or absence thereof, consider it flying in the coasting phase. The lift needed to stay aloft or even climb is then provided by a combination of the wings and the slender main body (where the guidance systems, warhead and sometimes engine are housed).

The question is, what is the proportion of lift coming from the wings compared to that of the fuselage?

NOTES:

  • A good answer should use a real or realistic design to base their calculations on.
  • I have purposefully left the choice of design open, so people can pick one they are familiar with or have data on. All that matters to me is that the general shape must be similar to that of modern AAMs.
  • Feel free to elaborate on how the lift proportion changes at different flight conditions (subsonic vs supersonic); it is quite clear that higher speeds lead to smaller wings.
  • I am aware that short range WVR missiles like the R-60, R-73 or AIM-9 are designed to reach their target before engine cutoff or shortly after; this has no bearing on the question.
  • This answer below presents a good extreme where most of the lift has to come from the body, because the only fins are too far away from the center of mass. In such cases, where the fins act as a stabilizer, their lifting force can still be calculated and compared to the total lift required, if we can assume the location of the CG.
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  • $\begingroup$ The missiles you refer to do not typically operate "in the coasting phase" - they are supposed to strike before they "run out of gas". $\endgroup$
    – MikeB
    Oct 3, 2019 at 13:23
  • $\begingroup$ @MikeBrockington if you have a source I would really like to see it. To my knowledge burn time of the AIM-120 is about 6 seconds, which would not account for most of it's range (source). That being said, assuming engine cut off is a simplification that should not impact the calculations by more than $Sin (\theta)$ with $\theta \ll 1$ and can be disregarded for a first approximation. $\endgroup$
    – AEhere supports Monica
    Oct 3, 2019 at 13:31
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    $\begingroup$ @MikeBrockington Only very short-range missiles have the luxury of hitting before the gas runs out. The exact properties of the solid fuel and the fuel-fraction/aerodynamics of the missiles may not be openly published, but are simple enough that reasonably-detailed simulations can show they won't get anywhere near the designed range if they could only make the kill with the engine active. $\endgroup$
    – aerobot
    Oct 3, 2019 at 15:14
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    $\begingroup$ @CamilleGoudeseune at my university we used the term wings to distinguish them from moveable control surfaces and traditional fins (fixed surfaces at the rear whose main purpose is providing stability). But whether they can be rightfully called wings (in this case) is part of my question :) $\endgroup$
    – AEhere supports Monica
    Oct 3, 2019 at 15:37
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    $\begingroup$ @Jimmy neither can a glider... your point? The fact is that missiles can maneuver in the coasting phase, so they must be able to generate lift at the expense of increased drag, and trade kinetic energy for height like any other aircraft. $\endgroup$
    – AEhere supports Monica
    Oct 3, 2019 at 21:58

1 Answer 1

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What is the proportion of lift coming from the wings compared to that of the fuselage?

It can be almost zero. The ASRAAM's only fins or wings or lifting surfaces or whatever you call 'ems are at its very tail. Any "lift" they impart, that far from the missile's center of mass, would pitch (or yaw) the missile instead of counteracting gravity. So almost all the lift must come from the body having a slight nose-up attitude.

infographic of ASRAAM missile

Another missile with a similar planform is the (ground vehicle launched) LOSAT.

LOSAT missile

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  • $\begingroup$ Yet the missile remains in straight flight, so we could, from its characteristics, quantify the amount of force generated by the fins and the body, and compare them. In fact, in that configuration, the fins are lifting, or the missile would pitch up. $\endgroup$
    – AEhere supports Monica
    Oct 4, 2019 at 8:01
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    $\begingroup$ Also, +1 for the LOSAT, not a usual example, but one I remember from the books I had as a kid. $\endgroup$
    – AEhere supports Monica
    Oct 4, 2019 at 8:03

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