Experimental Study at Low Supersonic Speeds of a Missile Concept Having Opposing Wraparound Tails

AbstractA wind-tunnel investigation has been performed at low supersonic speeds(at Mach numbers ofl.60, 1.90, and 2.16) to evaluate the aerodynamic char-acteristics of a missile concept capable of being tube launched and controlledwith a simple one-axis canard controller. This concept, which features anaxisymmetric body with two planar canards and four wraparound tail finsarranged in opposing pairs, must be in rolling motion to be controllable inany radial plane with the planar canards. Thus, producing a constant rollingmoment that is invariant with speed and attitude to provide the motion isdesirable. Two tail-fin shaping designs, one shaved and one beveled, wereevaluated for their efficiency in producing the needed rolling moments, andthe results showed that the shaved fins were much more desirable for thistask than the beveled fins.IntroductionTactical missiles that do not require high maneu-verability (air-to-ground or antitank) can make useof more simple stability and control techniques thanare required for missiles needing high maneuverabil-ity (air-to-air or surface-to-air). One such simplifiedtechnique is to have the missile airframe rolling inflight. This spinning motion not only enhances sta-bility but also allows the missile to be controlled inany radial plane by small planar canards driven by asingle-axis controller (i.e., no differential deflections).Another desirable feature for this class of missile isthe ability to fold all the fins, which could includecanards, wings, or tails, into or around the bodyfor compact tube storage. The fins would then bedeployed as the missile exits the launch tube. Ex-amples of current systems using folding fins can bcfound in reference 1 and include: (1) tile Redeye mis-sile, which has fins that fold rearward; (2) its replace-meat, the Stinger missile, which has short-span tailfins that fold into a necked-down region of the body;and (3) the TOW missile, which has wings that foldrearward and tails that fold forward.Another method of accomplishing compact tubestorage for tail fins is to have them wrapped aroundthe body circumferentially before and during launch.The aerodynamics of wraparound tail fins is thus ofgreat interest for this class of missile and has beenthe subject of numerous studies for many years bythe Department of Defense (refs. 2--4), NASA (refs. 5and 6), and others (refs. 7-9).The traditional wraparound-fin configuration hasfour curved fins mounted in a cruciform arrange-ment, with each fin curving in the same directionand wrapped around approximately 25 percent ofthe body circumference before deployment. Theprevious studies cited in the aforementioned refer-ences were all conducted using this traditional ar-rangement, which is illustrated in the sketch infigure l(a). This arrangement produces a non-symmetric configuration and is known to producenonlinear and sometimes erratic aerodynamics, es-pecially in rolling moment, even at small angles ofattack. (See refs. 2 5.) One current system that em-ploys the traditional wraparound folding arrange-ment in a design consisting of three tail fins is theDragon missile (ref. 1).In the present study, a novel fin arrangement de-signed to overcome these undesirable aerodynamicfeatures is investigated. This arrangement haswraparound tail fins mounted in opposing pairs,as shown in the sketch in figure l(b). When un-opened, the opposing fin pairs overlap and fit insidea body cavity to allow storage within a constant-diameter launch tube. This arrangement has sev-eral potential aerodynamic advantages over the tradi-tional wraparound arrangement, and these are listedas follows:1. Because of overlapping, the fin spanwise arclength is not limited to 25 percent of tile bodycircumference.2. Symmetry on the model is established, whichshould eliminate some of the undesirable aero-dynamic characteristics of the traditional wraparoundfins.3. Deployment of these fins by blasting them intothe open position can be accomplished by using twoside-mounted scarfed nozzles located underneath theoverlapping fins, whereas four such nozzles would berequired for the traditional wraparound fins.