US3028125A - Catapult - Google Patents

Description

April 3, 1962 A. c. SCURLOCK ETAL 3,028,125

CATAPULT 4 Sheets-Sheet 1 Filed July 11. 1952 I WFW A a;

M. 2 4M5 M7 Q Y Q B 1 m. 1

April 3, 1962 A. c. SCURLOCK ETAL 3,028,125

CATAPULT Filed July 11, 1952 4 Sheets-Sheet 2 m I l r TOTAL HEAT 40.5355 WWTFVIE'DATEFEECW I 94/1RUERESI'IW/NED AT BIEHW ENEEGY L057 INVENTORS ARCH CZ Sconce/K,

MAL/1E0 1E: fi/cz 514 5464 l. 11411.53

! BY wofm AGENT Filed July 11, 1952 4 Sheets-Sheet 3 AVERAGE GAS TEMPERATURE "K CHAEGE pare/Bur Ala/VG- 7055 Cl/AEGE EESTEA/NED 147' 52556 1 H00 TIME 69C.

l INVENTORS i 5AE5AA lluss BY fm AGENT April 3, 1962 A. c. SCURLOCK ETAL 3,028, 5

CATAPULT 4 Sheets-Sheet 4 Filed July 11. 1952 3,028,125 CATAPULT Arch C. Scurlock, Fairfax, Va, Millard L. Rice, Takoma Park, Md., and Barbara 1. Wales, Alexandria, Va,

assignors to Atlantic Research Corporation, Alexandria,

Va., a corporation of Virginia Filed July 11, 1952, Ser. No. 298,244 3 Claims. (Cl. 244-63) This invention relates to an improved catapult launcher. More specifically, it relates to catapults wherein the propellant charge is restrained at the piston.

It has hitherto been the practice to restrain the propellant charge at the breech or to allow it to distribute itself along the tube as in a Kent distribution. In either case the evolved gases must move forward into the space behind the moving piston. Assuming that the charge is properly designed to produce a substantially constant pressure in the catapult tube, the gases evolved by a charge restrained at the breech move at a velocity relative to the catapult tube wall which is substantially equal to that of the piston and the gases evolved by a charge distributed along the tube according to a Kent distribution mOVe at a velocity approximately equal to one half of the piston velocity.

The higher the velocity of the combustion gases, the greater are the heat losses due to convectional heat transfer. Some heat loss is also caused by radiation. However, in the conventional catapult, heat loss due to convection is much higher than heat loss due to radiation. In order to maintain the desired constant pressure in the catapult tube, heat losses must be compensated for by substantially increasing the amount of propellant charge.

The object of this invention is to reduce substantially heat losses due to convectional heat transfer in catapult launchers and thereby either to reduce considerably the amount of propellant charge required or to increase performance.

Other objects and advantages will become obvious from the drawings and the following detailed description.

FIGURE 1 shows, diagrammatically, a longitudinal section through a catapult tube wherein the propellant charge is restrained at the piston.

FIGURE 2 is a diagrammatic, longitudinal section through a catapult tube showing a modification.

FIGURE 3 illustrates graphically the comparative energy losses for different charge distributions.

FIGURE 4 shows the average gas temperature in the catapult for different charge distributions.

FIGURE 5 shows catapult tube pressures obtained with different charge distributions.

In general, our invention comprises attaching the propellant charge to or otherwise restraining it at the piston so that the burning charge moves with the piston and the combustion gases are discharged rearwardly of the piston. Since the gases are evolved directly into the space left behind the moving piston, the distance they travel is reduced to a minimum with corresponding reduction in gas velocity relative to the tube wall and in convectional heat transfer. Where the charge is properly designed to maintain constant pressure, the distance of gas travel is substantially zero. Thus the gases are substantially stationary relative to the tube wall and convectional heat losses are almost entirely eliminated. Reduction of convectional heat loss considerably reduces the amount of propellant charge required. Som convective heat loss is caused by turbulence in the gases but this is relatively small.

The propellant charge may be restrained at the piston in any desired manner. In FIGURE 1, charge I is inserted into recess 2 in hollow piston 3. The recess opens rearwardly of the piston at 4. The opening may be p A 3,028,125 E Patented Ap 3, 1962 covered with a perforated cover or grill 5 which permits free discharge of the combustion gases. The remainder of the figure shows a conventional catapult tube 6 equipped with launching platform 7, slot 8 and a slot sealing strip 9. The piston engages with the load at it).

In FIGURE 2, the charge is attached to the rear of the piston by means of a perforated cage 11.

FIGURE 3 shows comparative heat losses in firings of the same charge when the charge is restrained at the breech, distributed along the tube and attached to the piston. The catapult in this case has an inside tube diameter of 8.5 inches and permits maximum travel of the piston for,.136.5 feet. lbs. of propellant charge are employed with a moving load of 39,500 lbs. The propellant charge used for these calculations consists of 3 substantially wedge shaped units integrally united at their bases to form a composite grain of triangular cross section which is inhibited against combustion on all surfaces except along the edges of the triangle. Such a grain provides the high progressivity required to maintain the desired constant pressures and is more fully described in copending application Serial Number 286,990, filed May 9, 1952, of Arch C. Scurlock, which discloses propellant grains designed to produce substantially constant pressure and acceleration at any desired rate in catapult launchers.

It Will be seen that heat loss due to radiation constitutes a minor proportion of the total heat loss so that by eliminating convectional heat transfer, the energy loss by the system is greatly reduced. The heat loss where the charge is attached to the piston is about the same as loss by radiation and considerably less than the heat loss in the other two systems.

Elimination of convectional heat loss when the charge is attached to the piston result in substantial increase in average gas temperature as shown in FIGURE 4. This accounts for the somewhat higher radiational heat loss in this system as shown in FIGURE 3. However, the in crease in radiation heat loss due to this factor as compared with the energy saving obtained by elimination of convectional heat transfer is so slight as to be insignificant.

FIGURE 5 illustrates the increased pressures obtained when the charge is attached to the piston and the consequent increase in piston velocity.

Restraining the charge at the pistoi thus provides two important advantags. The charge can be employed to give increased performance as compared with the same charge either restrained at the breech or distributed along the tube. If an increase in performance is not required, the quantity of charge can be considerably reduced. In the case of the catapult employed in the foregoing illustrations, the saving in propellant is about 25% of that needed when the charge is restrained at the breech and about 17% of the amount required when the charge assumes a Kent distribution. With longer catapult tubes the saving would generally be greater, since heat losses usually increase with catapult tube length.

Although this invention has been described with reference to illustrative embodiments thereof, it will be apparent to those skilled in the art that the principles of this invention may be embodied in other forms, but within the scope of the appended claims.

We claim:

1. A catapult launcher comprising a piston chamber and a piston which moves within said piston chamber and which is actuated by the pressure produced within said piston chamber by the combustion products of a propellant charge, the piston being provided with means for moving a load positioned exteriorly of the piston chamber, a perforated receptacle attached to the piston at the rear portion thereof, said receptacle serving to hold and restrain the propellant charge therein whereby the propellant charge is secure to and moves with the piston, said propellant-holding means permitting substantially free discharge of the combustion gases into the catapult rearwardly of said piston.

2. A catapult launcher comprising a piston chambe and a piston which moves within said piston chamber and which is actuated by the pressure produced within said piston chamber by the combustion products of a propellant charge, the piston being provided with means for moving a load positioned exteriorly of the piston chamber, said piston containing a recess opening rearwardly of said piston, said recess serving to hold the propellant charge whereby the propellant charge moves with the piston, the opening of said recess being provided with a perforated cover to restrain said charge within said recess and permitting substantially free discharge of the combustion gases into the catapult rearwardly of said piston.

3. A catapult launcher comprising an axially elongated piston chamber having a closed breech end and a piston having a gas pressure barrier portion transversely spanning said chamber which moves Within said piston chamher from a preignition position near said breech end and substantially through the length of said chamber, and which is actuated by the pressure produced Within said piston chamber by the combustion products of a propellant charge, the piston being provided with load coupling means extending transversely of the chamber axis ReEerences (Jited in the file of this patent UNITED STATES PATENTS 1,416,827 Holmes May 23, 1922 2,485,601 Hickman Oct. 25, 1949 2,489,748 Burney Nov. 29, 1949 2,527,020 Martin Oct. 24, 1950 2,541,087 Musser Feb. 13, 1951 2,606,725 Drei'belbis Aug. 12, 1952 2,644,364 'Nass 1 July "7, 1953 2,671,401 Abramson Mar. 9, 1954 FOREIGN PATENTS 129,675 Great Britain July 24, 1919 707,679 Germany June 30, 1941 631,261 Great Britain Oct. 31, 1949

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