FR2633381A1 - DEVICE COMPRISING A POST-ACCELERATION TUBE AND A PROJECTILE - Google Patents

Abstract

The device comprises a post-acceleration tube 1 having a larger caliber than the barrel tube, and which has at least three guide ribs 2 arranged on the inner periphery at a certain distance from each other, extending substantially in longitudinal direction of the post-acceleration tube 1 and delimiting by their internal end surfaces forming guide surfaces 3, an outline having a transverse shape which corresponds to that of the section of the projectile 5. Use in projectile and tube weapons. post-acceleration.

Description

I 2633381

  The present invention relates to a device comprising a gun and a projectile related thereto wherein:

  a post-acceleration tube which is filled

  sand with explosive gas, is arranged coaxially in front of the barrel tube; and - the projectile sliding without play in the barrel tube, is guided in the post-acceleration tube

  keeping a certain distance from a

  portion of the inner wall of said post-acceleration tube and has an outer contour such that between the inner wall of the post-acceleration tube and the outer wall of the projectile forms a diffuser along the entire length

of the last.

  But the present invention also applies very

  expressly to the barrel, the projectile or the post-

  acceleration described hereinafter alone, respectively.

  In order to increase the output speed

  can get in a usual barrel tube, it has been pro-

  posed, primarily on the theoretical level, to send the projectile, when leaving the mouth of the barrel, through a channel coaxial with the barrel tube and placed in front of him, filled with explosive gas, and to conceive the projectile relative to the inner section of the circular cylindrical channel so that the intermediate free space between said projectile and the wall

  channel, extending from the point of the projection

  tile and against its direction of flight, forms a

  broadcaster, as is also the case in a

  reactor. If the projectile is moved through the explosive gas previously admitted into the channel forming the post-acceleration tube at an ultrasonic velocity,

  develops on the projectile an increase of

  sion, as is also the case for a diffuser of a stato-reactor. The thrust waves taking birth

  as a result of the ultrasonic velocity flow

  explosive gas until it ignites, the

  resulting pressure then generates the desired additional thrust on the rear

convergent projectile.

  This theoretical reflection was verified by a practical test, drawing from a smooth barrel tube a sub-calibrated projectile provided with a thrust surface in a post-acceleration tube. The post-acceleration tube was closed at both ends by

  a solid membrane that had to withstand the strong pressure

  initially in this one and was traversed by the projectile.

  The ends of the guide surfaces protruding radially

  The body of the projectile slid into the smooth post-acceleration tube, the caliber of which coincided with that of the barrel tube. A device was provided between the barrel tube and the post-acceleration tube to remove the constituent parts of the surface

  thrust in the barrel tube to

sea a seal for gases.

  Although this known device resulted in an increase in the velocity of the projectile, it nevertheless presented a series of serious drawbacks which made

  its subsequent practical use very problematic.

  This known projectile requires surfaces of

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  which are arranged longitudinally, are rigid

  long, in order to guide the projectile into the

  post-acceleration tube. Naturally such

  Guiding faces have a high resistance to air, which is particularly unfavorable in the case of the high flight speeds envisaged. Moreover, the radial length of these guide surfaces can not be

  chosen at will, so that the caliber of the post-

  acceleration which determines the dimensions of the diffuser in connection with the dimensions of the body of the projectile,

  can not be chosen optimally.

  Moreover, the post-acceleration tube must

  have an internal machined surface with a high pre-

  decision; openings in the wall of the tube, for example for the introduction of gas, are problematic;

  measuring probes or disks can not be used

  positive lights that emerge inside the tube

post-combustion.

  The membranes that seal the post-tube

  acceleration must be able to withstand the recommended internal pressure of 10 bars of the gas filling the post-acceleration tube and are therefore very stiff because of the relatively large size and thus slow down

  the projectile unfavorably.

  But the most difficult thing is to distance the sur-

  thrust surface, the constituent parts of which do not

  not penetrate the post-acceleration tube because they could clog the "diffuser", ie the intermediate volume between the body of the projectile

and the wall of the tube.

  Use of the post-acceleration tube

  known with a stretched tube gun is not possible.

  Given this state of the art, the

  The object of the present invention is to eliminate at least

  the disadvantages mentioned above and to propose preferably a device of the type described above, which is more suitable for an effective practical application than the known device, or which all

  at least allows to consider this one.

  According to the invention, this device is characterized in that: the post-acceleration tube has a larger gauge than the barrel tube; and the post-acceleration tube has at least three guide ribs disposed on the inner periphery at a distance from each other, extending substantially in the longitudinal direction of the

  post-acceleration tube and defining by their

  internal end faces forming forming surfaces, an outline having a transverse shape which

  corresponds to that of the section of the projectile.

  According to the present invention, the post-tube

  acceleration has guiding ribs that extend

  substantially longitudinally in said post-acceleration tube and protrude on its inner wall. The internal radial longitudinal surfaces of these guide ribs which are at least, and preferably three, delimit a

  contour corresponding to the caliber of the projectile,

  to the body of the projectile, so that the projection

  tile is guided in the post-acceleration tube by said internal surfaces or by their lateral edges. The primary advantage of the present invention lies in the fact that the projectile is guided on the body of the projectile itself, so that it does not need to have suitably rigid guidge surfaces and that it presents therefore less resistance to air. At the same time, only part of the inner surface of the post-acceleration tube is intended for

cooperate with the projectile.

  Thus the projectile does not require any

  thrust face to be propelled into the barrel tube itself, so that we avoid the problems that are related to the fact that we must prohibit the elements of the

  push surface the entry into the post tube

  acceleration. The post-acceleration tube has at least

  three internal grooves extending substantially in

  longitudinally, separated by the guide ribs, that is to say by their guide surfaces, grooves whose surfaces do not come into contact with the projectile; thus it is not necessary to pay particular attention to the finishing of the surfaces of these parts of the internal surface, of the post-acceleration tube which

  are occupied by these throats. More important, however, is

  the fact that there is no constraint to the choice of the depth of these grooves: we can optimize

  the latter in such a way that it results simultaneously

  An optimum section for the formation of the "diffuser" by an adaptation to the relevant speed zone and by the corresponding optimum composition of the explosive gas mixture, without the optimal shape initially already given to the projectile being influenced.

so far.

  Furthermore, it is possible, and even recommended according to a preferred embodiment of the present invention, to arrange the holes provided in the known post-acceleration tube and intended for setting up a measurement probe, or for introduction of gas, or

  analogous, so in the post-tube

  acceleration according to the present invention they open into the bottom of said grooves. As a result, these holes not only do not influence the movement of the projectile, but it is even possible to climb

  in these holes, devices that emerge in the

  the tube almost to the level of the guide ribs. Thus it becomes possible to carry out measurements in areas remote from the wall; it is particularly important to make possible by a complementary ignition system such as a spark plug, a precise action on the detonation of the filling in explosive gas, because the triggering of this detonation caused by the spark plug no longer occurs inside a piercing forming a kind of pre-combustion chamber, as was the case until now, but it is produced directly inside the tube by a spark plug which emerges

inside said tube.

  Another advantage of the present invention lies in the fact that the two membranes which close the post-acceleration tube have to cover a smaller distance than was necessary in the tubes of

  post-acceleration known until then, since the said membranes

  They can be fixed on the front surfaces of the guide ribs. Thus said membranes may have a smaller thickness than they had hitherto, which decreases all the braking that they exert on the projectile and therefore increases

  the effectiveness of the device according to the present invention.

  The post-acceleration tube conforms to the pre-

  This invention can be directly added to the barrel tube itself or be made in one piece with the latter; between them two, it does not actually matter

  a simple outlet of air which serves to

  the air cushion propelled forward by the

  jectile, so that it does not flush the filling

  in gas from the post-acceleration tube.

  The air outlet openings may be located at the beginning of the post-acceleration tube and open into the grooves, so that the internal guide surfaces of the guide ribs may be directly connected with the bore of the tube core.

  of cannon. This avoids any free movement of the projec-

  tile that is simply disadvantageous, as well as the disadvantages that may result from membranes in which air outlet openings should be provided. But it would also be possible, and possibly advantageous, to create a through bore for the barrel tube and the post-acceleration tube and to provide a sealing sleeve on the projectile; in this case, and at the end of the process of loading the barrel, this complete bore would be filled with explosive gas which would be pushed back by the projectile, during the initial acceleration of the latter, of the barrel tube in the post-acceleration tube. he would then be compressed. After placing the membrane on the side of the mouth, the

  gas filling could be controlled automatically-

  by the locking movement. Such a gun would already be completely usable in practice, in comparison with the previously described device which can finally only operate under conditions

experimental laboratory.

  Preferably, the barrel tube is smooth and the projectile is made self-stabilizing, for example by moving its center of gravity forward. In this case, the guide ribs are preferably given a rectilinear shape; but it would also be possible, and possibly advantageous, to

  to give a helical shape in order to confer

  a slight rotation to minimize influences

  irregularities which lead to deviations from

port to the goal.

  A specific advantage of the present invention

  However, it can also be applied to guns having a stretched tube: in this case, the gauge delimited by the inner faces of the guide ribs corresponds to that of the grooving fields.

  of the barrel tube, and the guide width of said

  faces does not exceed the width of said barrel tube fields. Preferably, the guiding surfaces form the extension of said fields, and therefore present the

  same helical shape with the same pitch as these.

  In the case of very high and narrow guide ribs, it may also be advantageous for their helical progression towards the mouth of the post-acceleration tube to be degressive, that is to say to have a step increasing, and this , in fact, to such an extent that the rotation printed to the projectile in the tube

  which is totally sufficient for its stabilization

  simply maintained during post-acceleration.

  The stress of the guide ribs in the direction of the

  pheric is thus reduced to a minimum value.

  But conversely, it would also be possible, and possibly even advantageous in some cases, to provide a post-acceleration tube with a helical pitch

  with a lower value or a progressive value.

  sively growing; in this case, the barrel tube could have a propeller that is not quite

  sufficient to give the projectile the necessary rotation

  sary. This provision prevents the pre-departure

  matured projectile out of the barrel tube or it makes possible a greater acceleration of the projectile in

  barrel tube, so that the effectiveness of the

  tif according to the present invention is also improved by such a measurement. Naturally, the guide ribs must be made in such a way that they are capable of transmitting the forces that these guide ribs must exert on the projectile to increase

its rotation.

  Finally it is also possible to draw with the device according to the present invention a sub-calibrated projectile which may even have optimized aerodynamic guide surfaces in the case of the realization with a smooth tube: in this case, this part of the outer contour of the projectile which forms the "diffuser" by cooperating with the bottom of the throat of the post-acceleration tube is constituted at least

  partially by the thrust surface that does not

  the projectile itself only after leaving the post-acceleration tube. While the thrust surface passes through the post-acceleration tube, the segments of said thrust surface are held together between

  them by the guide surfaces of said post tube.

  acceleration. Thus it is possible to benefit equally

  all the advantages of the present invention with projectiles controlled by guiding or sub-calibrated surfaces. The explosive gas is preferably a mixture of hydrogen or hydrocarbons with oxygen and inert addition gases such as nitrogen and helium, so that by a modification of the mixture of Nitrogen and helium the speed of sound in the gas mixture can be adjusted and the Mach number can be maintained in an optimal zone, despite the

  velocity variations of the projectile. It is thus possible

  ble to adjust the gaseous current in the "diffuser" according to the velocity of the projectile in the post-acceleration tube so as to always obtain the optimal degree of efficiency. Depending on the speed zone, the combustion will occur under subsonic regime as in a RAMJET or ultra-sonic regime as in the case

  SCRAMJET (lit by an oblique detonation wave).

  The present invention will be described by way of nonlimiting example with more details using

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  schematic drawings attached which represent: - figure 1, a longitudinal section through

  part of the post-acceleration tube according to the pre-

  invention, at the moment it is traversed by a projectile according to the present invention; - Figure 2, a representation similar to that of Figure 1, however in an even more schematic form, different speed conditions from those of the representation of Figure 1 being shown here; and FIG. 3, a section on a larger scale at

  through the post-acceleration tube of Figure 1.

  Figures 1 and 3 show a tube of

  post-acceleration 1 in longitudinal and transverse section

  dirty. This post-acceleration tube has on its face

  internal three guiding ribs 2 arranged longitudinally

  dinalement in the tube and equidistant from one of the

  other, their guide surfaces 3 oriented towards the in-

  interior thus delimiting a circular outline which is

  represented in dotted line in FIG.

  Between the guide ribs 2 are arranged longitudinal grooves 4 whose bottom has, in section, a circular arc shape coaxial with the surfaces of

guidance 3.

  The transition between the bottom of the groove 4 and the walls of the groove which form the lateral faces of the guide ribs 2, is strongly rounded, so that

  these guide ribs 2 are capable of supporting

  ter strong transverse stresses.

  FIG. 2 shows a projectile 5 which rests on the guiding surfaces 3 by its largest circular section and is thus at a certain distance

respective throat funds.

  The projectile has a cone-shaped pointed nose, a cylindrical middle portion 7

  circular and a rear part which is

in the form of a truncated cone.

  The nose 6 of the projectile therefore forms, with respect to the wall of the throat bottom of each of the grooves 4, an intermediate volume whose importance decreases in the direction of advance of the projectile 5, ie, in FIG. left and right; the intermediate volume formed between the rear part 8 of the projectile and the bottom of the grooves widens in the same direction, and the volume formed between the middle part 7 and the bottom

gorges remain constant.

  If the projectile 5 moves in the post-acceleration tube 1, the influx of air into the free intermediate volume located between the nose 6 of the projectile and the post-acceleration tube is such for a speed of displacement of the appropriate air, that ultrasonic compression occurs; again, for an appropriate air velocity, subsonic compression occurs in the intermediate volume between the rear part 8 of the projectile and the tube

post-acceleration 1.

  It thus forms between the projectile 5 and the post-acceleration tube 1 a moving diffuser

  with the projectile 5, which is powered by the explo-

  sif located in the post-acceleration tube 1 and whose effect corresponds to the diffuser of a stato-reactor

  which gives rise to a combustion chamber pressure

  in the manner of a compressor.

  The area to the right of the projectile (Figure 1) or, for appropriate air circulation, to the right of the ultrasonic booster (Figure 2), behaves

  combustion chamber. Under the influence of pressure peaks

  resulting from it, the explosive gas is

  this area and explodes, so that it exerts

  on the rear part of the projectile. Due to the pressure generated in the diffuser, a penetration

  from the front of the explosion to the front part of the

jectile 5 is not possible.

  In the embodiment of FIG. 1, the moving projectile 5 is fed in the direction

  explosive gas arrow at rest at a higher speed than

  faster than the speed of sound in this gas. Circularly around the nose 6 of the projectile is formed a frontal wave 9 which is reflected on the wall of the tube of

post-acceleration 1.

  In the area of the rear part 8 of the projec-

  tile, sets up a plane thrust wave 10 which delimits

  moth forward an area of high pressure, in which the speed is below the limit

  sound, as in a stato-reactor. This area of

  high pressure extends to the combustion zone. The high pressure acts on that section of the projectile which is located at the thrust wave 10. In the combustion zone 12, the velocity of the gas stream rises to the speed of sound. It is therefore in the embodiment of Figure 1 of a combustion

subsonic with thermal blocking.

  Figure 2 represents very schematically

  tick the device already illustrated in detail on the

  FIG. 1, the speed of circulation of gases being simple-

  It is higher than that of the embodiment of FIG. 1. In contrast to the embodiment of FIG. 1, the velocity of the gas stream remains in the range of the ultrasonic velocities both in the zone of the party

  8 of the projectile behind the projectile 5.

  In this embodiment, the detonation pressure acts on the entire section of the

projectile 5.

  Furthermore, FIG. 3 illustrates the introduction of a gas inlet opening 14, a measuring probe 15 and a spark plug 16 at each

  once in a crossing of the wall of the post-tube

  acceleration 1. These devices 14, 15 and 16 respectively open respectively into the bottom of a groove 4 and the

  middle between two guide ribs 2.

  As the drawing shows, the candle

  mage 16 emerges inside the post-acceleration tube 1, but ends however before the guide contour delimited by the guide surfaces 3 and shown in FIG.

dotted in Figure 3.

  The post-acceleration tube 1 can be

  placed on the front of a conventional single-stage helium gun, which gives the projectile 5 the necessary acceleration

  to reach the ultrasonic speed. The post-tube

  acceleration is intended to form an accessory piece placed at the front of a conventional barrel tube whose projectile is pushed in the usual way with pyrotechnic means. By appropriate adaptation of the gas mixture which is preferably composed of hydrogen, oxygen, nitrogen and helium, the latter serving to adjust the speed of sound in the gas, it is also possible to optimize the distance between the bottom of the grooves and the guide surfaces 3 in the post-acceleration tube shown, and to adapt it to the projectile speed without, for all that,

  any intervention on geometry or con-

  truction of the projectile itself is necessary.

  It is thus possible to achieve a balisti-

  than constant of the order of 25%. The effective pressure (defined as the force exerted on the projectile

  divided by the area of its useful section) remains practically

  constant speed up to a speed of approximately 2300 m / s and then decreases slightly in the

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  subsonic combustion (embodiment of Figure 1, which is taken into account up to

  an absolute velocity of the projectile of about 3,000 m / s).

  It initially amounts to about 60% of the peak pressure developing during combustion, pressure

  for which the post-combustion tube 1 and the projection

  tile 5 must be provided. This means that then

  post-acceleration of the projectile 5 is under a

  constant pressure at around 60% of the maximum pressure and begins to decrease slowly only at a projectile velocity of approximately 2300 m / s,

  post-acceleration tube is used until it is

  maximum pressure corresponding to its resistance to

  sion, by appropriate adaptation of its pressure of

filling.

  In explosive combustion, relatively high pressure spikes occur and are always located at levels of the order of five times

  higher than the effective pressure.

  If the charge of the post-acceleration tube is

  reduced to this area, taking into account who

  in such a way that the maximum permissible pressure for the projectile and the post-acceleration tube is not exceeded, the projectile can only be accelerated with an effective pressure of approximately 20% of this value. However this acceleration can be kept constant up to around 6 000 m / s

  - again by an appropriate adaptation of the composition

initial detonation gas.

  Above, it is understood that the projectile is accelerated in a barrel tube before entering

  in a post-acceleration tube. But he is also

  possible to choose another pre-accelerator mode.

  tion, for example by means of an electromagnetic field,

  without departing from the scope of the present invention.

Claims (6)

  1. Device constituted by a gun and a projectile related thereto, in which:   a post-acceleration tube which is filled   sand with explosive gas, is arranged coaxially in front of the barrel tube; and the projectile sliding without play in the barrel tube, is guided in the post-acceleration tube keeping a certain distance with respect to a part of the inner wall of said post-acceleration tube and has an outer contour such as between the inner wall of the post-acceleration tube and the outer wall of the projectile forming a diffuser throughout the length of the latter, characterized in that - the post-acceleration tube (1) has a larger gauge than the barrel tube ; and the post-acceleration tube (1) has at   least three guide ribs disposed on the periphery   internal region at a distance from each other, extending substantially in the longitudinal direction of the post-acceleration tube (1) and delimiting by their internal end surfaces forming guide surfaces (3), a contour having a cross-sectional shape   which corresponds to that of the section of the projectile (5).   2. Device according to claim 1,   above, with a smooth barrel tube, characterized in that the guide ribs (2) extend in a straight line.   3. Device according to claim 1, characterized   characterized in that the barrel tube is stretched and the guide ribs (2) have a helical shape   and follow the fields of the barrel tube.   4. Device according to any one of   Claims 1 to 3, characterized in that the projectile   is produced in the form of a projectile (5) without   pushing face and that the shape of the contour delimited in section by the guide surfaces (3) coincides with the caliber of the smooth barrel tube, or with the barrel tube fields stretched. 5. Device according to any one of   Claims 1 to 4, characterized in that equipment   annex (14, 15, 16) is arranged in the wall of the   post-acceleration (1) and, each time, between two guides (2).   6. Device according to claim 5, characterized   characterized in that said ancillary equipment (16) emerges   inside the post-acceleration tube (1).