Claims:The scope of the invention is defined by the following claims:

Claim:
1. A deep slot propellant milling machine comprising:
a) A telescopic arm (5) attached to a cylinder (6) mounted on a control unit (9) with the help of a mounting assembly (7).
b) A multistage cutter (2) is attached to a micro fin (4) which is rigidly fixed to the telescopic arm (5)
c) A guidance system i.e., camera and lighting system (3) is attached to one end of the cylinder (6) along with the telescopic arm (5)
d) A vacuum hose (1) is attached to the mounting assembly (7) near to its lower end. A eddy current sensor (8) is attached to the upper surface of the mounting assembly (7).
2. As mentioned in claim 1, mounting assembly is used to fix the machine rigidly with the rocket motor and the telescopic arm is responsible for the movement of multistage blade cutter in all its degrees of freedom.
3. According to claim 1, multistage blade cutter comprising a primary cutter (2a) and a secondary cutter (2b) rotates in anticlockwise direction and an auxiliary cutter rotates in clockwise direction to cut the propellant smoothly without any flaw or discontinuities.
4. As per claim 1, guidance system i.e., camera and lighting system is used to monitor the whole operation which is operated by the control unit interfaced with the computer.
5. As per claim 1, vacuum hose is used to remove the cutaway propellant from the rocket motor to clear the blade pathway for continuous operation.
6. As per claim 1, eddy current sensor is used to identify the presence of foreign particles in the propellants.
7. As per claim 1, the combined usage of multistage cutter along with vacuum hose decreases the heat produced in blades due to friction. , Description:Field of Invention
The present invention pertains to controlling thrust in solid rocket motor by milling/radial slot in the propellant.
Background of the Invention
Thrust characteristics of the solid propellant rocket depends on the surface area of the propellant grain exposed to initial ignition. Augmenting burning surface area leads to increase in pressure and thrust. Once the ignition starts, controlling combustion in solid propellant rocket is a complicated process due to the continuous supply of propellant. Combustion process in the solid rocket motor can be controlled by making radial/circumferential slots in between the propellants. The conventional methods for making slots is by molding the slots in desired size and shape while fabricating the rocket motor itself. The commonly used mold materials are silicon rubber or any foam filler. The propellant in liquid form is then poured into the casting of rocket motor. After the propellant cured ie., conversion from liquid to solid state, the mold material will be carefully removed without disturbing the propellants. While removing mold material there is a possibility for relative motion between the mold material and propellant which in turn electrostatic buildup will occur. The risk factor will be very high for the ignition of propellant. Instead of making slots by molding, machining in the propellant itself may stand as a possible solution to overcome the above mentioned problem.
Machining of solid propellants are known in the prior art. For instance US006023983A discloses the operation of propellant cutting machine. The machine has mounting mechanism to fix rigidly the cutter with solid rocket motor nozzle. The arm with knife edge will be extended linearly along the axis of the machine to make slots in the propellant. The drawback noted in the above mechanism is ribbon of propellant grains formed during cutting process is difficult to remove while operation. The absence of guidance system makes it not suitable for making deep slots in the propellant inside the rocket motor. The multiple stage cutting tool with guidance system will solve the propellant removal problem while operation which was disclosed in US005615983A. The method describes herein suffers from high heat build up around the milling area due to friction between the tool and propellant. The same problem was noted in most of the prior art. US4541757A discloses the operation of propellant milling tool which can able to overcome the previous drawbacks. However, the high heat buildup around the milling region was controlled poses serious attachment and mounting issues of cutter with rocket motor casing for continuous operation.
Accordingly, there is an urgent need and demand for a milling machine to make radial/circumferential slot in the solid rocket motor. The present invention overcome these problems observed in the prior art and discloses herein the operation of deep slot propellant milling machine devoid of the above mentioned drawbacks.

Summary of the Invention
In light of the above mentioned drawbacks in the prior art, the present invention aims to control the thrust produced in solid rocket motor by making circumferential/radial slot in the propellant.
The specific objective of the invention is to design a machine which can able to cut the propellant without the formation of high heat build up around the milling area due to friction between the cutting tool and the propellant.
A further specific objective of the invention is to remove the ribbon of propellant accumulation in the tool path while operation itself in a safe and reliable manner.
Brief Description of Drawings
The invention will be described in detail with reference to the exemplary embodiments shown in the figures wherein:
Figure 1 Pictorial representation of deep slot propellant milling machine
Figure 2 Pictorial representation of enlarged view of multistage cutter
Detailed Description of the Invention
The embodiments of the present disclosure provide a deep slot milling machine which makes radial/circumferential slots in the solid rocket motor as per the required dimension and shape. Deep slot milling machine was designed based on the following criteria, i) Propellant should be cut into number of small pieces to avoid electrostatic build-up and it should be removed instantly. ii) The cutter should be cooled frequently to avoid issues due to heat formation.
With reference to the figure 1 the ‘Deep Slot Propellant Milling Machine’ is provided in accordance to an embodiment of the present disclosure. Telescopic arm (5) is attached with a cylinder (6) to control the movement of the multistage cutter blade in all the degrees of freedom. A stepper motors is provided to hold the cutters at required position. The arm will be operated by control unit (9) interfaced with computer for precise control. The mounting assembly (7) was provided to fix the machine rigidly to the rocket motor assembly.
In accordance to an embodiment of the disclosure, the multi stage cutter blade (2) comprises of three different sets of cutter which is shown in figure 2. The initial cut was made by auxiliary cutter (2c) and secondary cutter (2b) which makes the way for primary cutter (2a) to make a smooth cut on the propellant. The auxiliary and secondary cutters are having number of cutting blades located separately at certain angle to the center axis. The secondary and primary cutter rotates in anticlockwise direction. Meanwhile the auxiliary cutters rotates in clockwise direction. The auxiliary cutters are attached with winglets to reduce drag. The primary cutter is circular in shape to cut the propellant flawlessly into number of pieces to avoid electrostatic build-up. By the usage of multistage cutter friction between the propellant and cutting tool will decrease tremendously. In other hand milling rate will increase.
Even though blades of the multistage cutter will experience small amount of heat while operation that can be nullified by micro fins (4) which is attached behind the multistage cutter unit and it is shown in figure 1. The micro fins ensures the continuous usage of cutter without undergoing heat due to friction while operation
A camera (3) with lighting system will act as guiding system which is attached along with the arm to cylinder (6). The guiding system can able to rotate 3600 and move axially along the cylinder to monitor the operation of the cutter. The presence of guidance system ensures the potential of machine for deep slot cutting in rocket motor. The movement of the guidance system will be controlled by control unit (9) interfaced with a computer.
A vacuum hose (1) is attached along with the mounting assembly to remove the cut away propellant from the rocket instantly. The propellant will not settle down along the blade pathway. In turn friction between the propellant and cutting tool will decrease tremendously. The presence of any foreign particles in the propellant will be indicated by a Eddy current sensor (8) which is fixed above the mounting unit (7).
7 Claims & 2 Figures
Equivalents
The deep slot propellant milling machine of the present invention discloses its usage in terms of cutting propellants in solid rocket motor. The same machine/operation/mechanism may be used to cut the variety of materials even in general machining workshop. The scope of the invention was not limited to its usage as propellant cutter/miller in solid rocket motor.