GB2230844A

GB2230844A - Air breathing missiles

Info

Publication number: GB2230844A
Application number: GB8328105A
Authority: GB
Inventors: Eustace Laurence Goldsmith; Ian Mcgregor
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1982-10-28
Filing date: 1983-10-20
Publication date: 1990-10-31
Anticipated expiration: 2003-10-20
Also published as: GB2230844B; SE8305863L; DE3338697A1; IT8349204A0; SE8305863D0

Abstract

The ingestion of vortices into engine intakes 13, Fig 1, at the rear of a guided missile 10 is prevented by having intakes whose breadth increases with radial distance from the surface of the missile and by providing, forwards of each of the intakes, longitudinally extending vortex anchoring edges 12. The edges are constituted by strakes extending along a cylindrical missile body or, where the missile body is of triangular or square cross-section (Figs 5 & 6 not shown) by the corner edges of the body. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO GUIDED MISSILES The present invention relates to guided missiles of the type which have engine intakes toward the rear thereof.

IXhen a body such as that of a guided missile moving at high velocity pitches or yaws wake vortices are set up over that part of the body which has become the trailing part. If the missile is air breathing these vortices, or part thereof, may be ingested into the intakes, leading to a drop in the pressure recovery therein.

This can not only reduce the power of the engine but also cause damage thereto, deleteriously affecting missile delivery.

In some known multi-intake missiles of this type strakes formed by cable runners have been fitted at stations intermediate the intakes in an effort to alleviate this problem. It was not entirely successful.

By the present invention is provided a solution to the problem in a manner which is particularly economical in terms of missile structure and propulsive power.

According to the present invention a missile with engine intakes toward the rear end thereof, has, for each intake a vortex anchoring edge extending longitudinally of the missile and approximate the plane in which lie the missile longitudinal axis and the intake longitudinal axis, the intake effectively increasing in breadth with radial distance from the missile surface.

Preferably the edge lies within the said plane.

The vortex anchoring edges may be arranged to be those formed by a missile fuselage having substantially a triangular (preferably equilateral) or quadrilateral (preferably square) cross section. Alternatively the edges may be constituted by strakes, which may then extend along an otherwise substantially cylindrical, preferably right cylindrical missile fuselage. Such strakes are advantageously sharp edged. Their breadth need be no greater than 0.1 body calibres; 0.02 calibres is adequate.

Advantageously the edges extend forward at least to the missile shoulder, and preferably to the base of the nose cone, eg 0.8 body calibres (that is body diameters) aft of the nose.

According to a feature of the invention the edges may terminate one or two body calibres ahead of the intakes.

They may however terminate at or behind the intake mouth, in boundary layer diverters, thereby also structurally stabilising the intakes.

In one embodiment of the invention the shape of each intake mouth is such that an angle between 90" and 1700 is subtended adjacent the missile fuselage about which angle the intake is substantially symmetrical, thereby reducing the likelihood of vortex ingestion even in more extreme angles of incidence.

In another embodiment of the invention the intakes mouths are half axisymmetric, with the circular boundary facing the missile body. This affords the advantage of readily enabling the provision of a boundary layer bleed from the outer part of the intakes. The size of the intake mouths may be such that the entire intake entry area totals 25-50% of the maximum missile body cross sectional area. For storage consideration the distance of each intake from the missile body is preferably minimised to no less than 1-2 boundary layer thicknesses on the missile body adjacent the intake mouths.

Preferably the intakes mouths are 8 to 9 body calibres rearward of the nose and lie entirely in the same missile radial section plane. Nevertheless by 'toward the rear' in this specification, is intended any position, usually aft of at least three missile body diameters, at which vortices ahead of the intakes are generated by the missile body in the wake of an angle of incidence.

Guided missiles in accordance with the present invention will now be described by way of example with reference to the accompanying drawings, of which Figure 1 is a side elevation of part of a first missile, Figure 2 is a front elevation thereof, Figures 3 and 4 are side and front elevations respectively of a second missile, Figures 5 and 6 are front elevations of third and fourth missiles respectively and Figures 7 and 8 are graph illustrating pitot pressure variations at incidences of 10 and 140 respectively.

Illustrated in figures 1 and 2 therefore is a first guided missile 10 having four engine intakes 11 mounted symmetrically about the missile toward the rear end or base thereof. The mouth of each intake is distanced from the missile body by a structure comprising a strake 12 and a boundary layer diverter 13.

The strake 12 is in sharp edged plate form and extends from the intake to between the shoulder 10s of the missile and the nose cone lic thereof. The strakes 12 are coincident with the radii joining the missile axis with that of the associated intake.

Each intake mouth subtends at the strake an angle 11a. The arrangement is such that for all likely angles of incidence of the guided missile in flight body vortices thereby generated generally ahead of the intakes 11 and both anchored at the strakes 12 and avoided by the intakes.

In one example of the first missile the angle lia is 1500.

The second missile 30 illustrated in Figures 3 and 4 has four engine intakes 31 mounted symmetrically about the missile toward the rear end or base thereof. Ahead of each intake 31 and on the radius joining the intake axis with the missile axis, are strakes 32. The strakes 32 are sharp edged plates extending from some point on the missile nose cone to just ahead of the intakes 31.

The intakes 31 are half axisymmetric in cross section, with the flat surface facing outwards. In this flat surface is provided a boundary layer bleed (not shown).

In a typical example of the second missile the strakes 32 have a breadth of 0.1 calibre and extend from 0.8 calibre to 7 calibres aft. The intake mouths 31 are located at 8 calibres aft and commence two boundary layer thicknesses (determined at cruise) from the missile body. The total intake area equals 37.5% of the body cross sectional area.

The third missile,illustrated in Figure 5, has a fuselage 50 cross section whereof has the form of an equilateral triangle.

The edges 50a thus formed constitute vortex anchors. Three engine intakes 51, similar in shape to those 31 illustrated in Figure 4, are each located one outboard of the edges 50a.

The fourth missile, illustrated in Figure 6, has a fuselage 60 of square cross section, the corners 60a whereof constitute vortex anchors. Four engine intakes 61, similar in shape to those 31 illustrated in Figure 4 are each located one outboard of the edges 60a.

Figures 7 and 8 show the results of tests on a typical example of the second missile. In the tests pitot pressure was measured 0.2 calibres from the body surface at a station 7.5 calibres aft of the missile nose and at a plurality of angles 0 around the body, where = 0 coincides with a station above one strake. The figures illustrate the results of tests at M = 1.8 and missile incidence angles of 10 and 140 respectively, the full lines showing the pressures without strakes fitted, and the dotted lines with strakes fitted. Without strakes, there is a big dip in pitot pressure around the 30 roll position as the pitot tube passes close to the centre of the body vortex. With the strakes fitted this variation of pitot pressure is almost completely eliminated at a = 100, and very much reduced at 140.

Claims

1 A guided missile having engine intakes toward the rear thereof and, for each intake a vortex anchoring edge extending longitudinally of the missile and approximate the plane connecting the missile and the intake longitudinal axes, the intake effectively increasing in breadth with radial distance from the missile surface.

2 A guided missile as claimed in claim 1 and wherein the vortex anchoring edges are arranged to be those formed by a missile fuselage having an equilateral triangular cross section.

3 A guided missile as claimed in claim 1 and wherein the vortex anchoring edges are arranged to be those formed by a missile fuselage having a square cross section.

4 A guided missile as claimed in claim 1 and wherein the edges are constituted by strakes.

5 A guided missile as claimed in claim 4 and wherein the strakes have a breadth between 0.02 and 0.2 missile fuselage calibres.

6 A guided missile as claimed in any one of claims 1 to 5 and wherein the edges are sharp.

7 A guided missile as claimed in any one of claims 1 to 6 and wherein the edges commence forward of the base of the missile nose cone.

8 A guided missile as claimed in any one of the preceding claims and wherein the edges terminate ahead of the intakes.

9 A guided missile as claimed in claim 8 and wherein the edges terminate between one and two missile fuselage calibres ahead of the intakes.

10 A guided missile as claimed in any one of the preceeding claims and wherein the shape of each intake is such that an angle between 90" and 1700 is subtended adjacent the missile fuselage.

11 A guided missile as claimed in any one of claims 1 to 9 and wherein the intakes are half axisymmetric in shape.

12 A guided missile as claimed in any one of the preceding claims and wherein the outer part of each intake incorporates a boundary layer bleed facility.

13 A guided missile as claimed in any one of the preceding claims and wherein the entire intake entry area totals 25-50% of the missile fuselage cross sectional area.

14 A guided missile as claimed in any one of the preceding claims and wherein the closest distance of each intake mouth from the missile fuselage is at least 1-2 boundary layer thicknesses as measured in missile cruise conditions.

15 A guided missile as claimed in any one of the preceding claims and wherein the intake mouths lie entirely in the same missile radial section plane.

16 A guided missile substantially as hereinbefore described with reference to the drawings.

Amendments to the claims have been filed as follows 1 A guided missile having engine intakes toward the rear thereof and, for each intake a vortex anchoring edge extending rearwardly towards the intake mouths and longitudinally of the missile and in the plane connecting the missile and the intake longitudinal axes, the intake effectively increasing in breadth with radial distance from the missile surface.

5 A guided missile as claimed in claim 4 and wherein the strakes have a breadth between 0.02 and 0.1 missile fuselage calibres.

10 A guided missile as claimed in any one of the preceding claims and wherein the shape of each intake is such that an angle between 900 and 1700 is subtended adjacent the missile fuselage.

11 A guided missile as claimed in any one of claims 1 to 9 and wherein the intakes are axially symmetric in shape with an outwardly facing flat surface.