FIELD OF THE INVENTION
This invention relates to a Centrifugal Cannon based Sprinkler (CCS) system mounted on a deployment helicopter to aerially scatter Sensor Nodes (SNs) while traversing the candidate region. The present invention is an assembly of variable sized cannons connected to a common junction point.
BACKGROUND OF THE INVENTION
Sensor Nodes (SNs) is a device designed to monitor the particular changes taking place in its surrounding and a crucial part in any remote monitoring system. Wireless sensor network (WSN) is a system formed by the set of wirelessly connected SNs placed at different geographical locations within a target region. The efficiency and effectiveness of any WSN is greatly affected by the precise placement of SNs. The manual placement of SNs is only feasible for small scale regions but it becomes tedious, when the size of a target region is extremely large and manually unreachable.
The classification of deployment schemes are based on the initial arrangement of SNs {Figure 1}. In point initiated relocation schemes all SNs are initially dumped at one point within a candidate region, from where they relocate themselves to suitable positions within a candidate region. Some of these scheme requires SNs with locomotion capabilities for relocation while other schemes simply use randomly scattered SNs as initial arrangement (These schemes mostly use static SNs), while other relocates the SNs to more suitable positions after initial random scattering.
Random scattering of SNs from sky is well known method of deployment in vast and unreachable regions. Many researchers in their work have assumed the random positions of SNs within a candidate region after aerial deployment but the detailed model for random scattering of SNs, its efficiency and effectiveness has not been covered.
Arial dropping has been proposed by numerous researchers as most effective method for deployment of SNs. Aerially dropping SNs over predefined points is called Point-to-point dropping and has been proposed by some researchers, which uses a small robot helicopter for dropping SNs but the method is feasible only for small scale candidate regions due to limited flight radius and small weight carrying capacity of robot helicopters.
Aerial deployments over the large scale regions require actual helicopter as it has sufficient weight carrying capacity and flight radius. It has to scan the candidate region multiple times, following a particular scan pattern to effectively cover the entire region. It is similar to plowing of any agricultural field.
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Researchers have proposed various models for deployment. Corkeet. al. [1-2] proposed an autonomous scheme for deployment of SNs using a robot helicopter. It uses a screw grooved assembly for dropping SNs one after another at predefined locations. Although the model effectively deploys and maintains the small area WSN, it cannot be used for large area deployments. Yoshiaki et. al. in [3], proposed a deployment method for large-scale aerial deployment of SNs using dual-mode parachutes (parachutes can change their mode from “Glide” to “Falling” and vice-versa). While in air they perform local communications to determine their densities based on which operable state is selected (dense nodes Glide in random directions for random time interval in order to scatter while other remains Falling). This approach uniformly distributes SNs while hovering above the candidate region but densities can only be determined by the SNs flying approximately at same level (i.e., SNs within communication range), while other SNs flying at different altitudes may again lead to non-uniform deployment and mechanics of parachutes are not defined for this model.
Mark A. Carlson [4] presented a method for emplacing sensors, comprising the steps of modifying an existing sensor to attach an autorotational mechanism and deploying said sensor by autorotational means. It does not explicitly talks about CCS structure mounted on the aircraft for positioning of sensor nodes.
John Paul Strachan, Wei Yi, Jianhua Yang [5] presented an installation platform for deploying an earth-based sensor network utilizing a projected pattern from a height. The installation platform includes an aerostatic aircraft, at least one sensor-location projector, and a projector stabilizer. The sensor-location projector is coupled with the aerostatic aircraft, and is configurable to project the projected pattern including at least one sensor-location marker associated with a location for a sensor in the sensor network. The projector stabilizer is configurable for maintaining the sensor-location projector in a sufficiently static orientation relative to the location for the sensor to allow deployment of the sensor within a specified distance of the location on a surface of the earth from the sensor-location marker. In this work a sensor network deployment system along with a method for deploying the sensor network are also provided. This work does not explain about CCS method for shooting sensors out of the canon using centrifugal technique
Usman Hafeez, David Mauer [6] proposed a system and method for placing, activating, and testing sensors. The system comprises one or more server computers, one or more communication hubs, one or more unmanned aerial vehicles, and one or more sensors. The method comprises the steps of receiving geographic sensor placement locations, receiving sensor parameters, determining the geographic location of sensors, respectively sending location query signals to the unmanned aerial vehicles, respectively receiving location reply signals from the unmanned aerial vehicles, and calculating a geographic flight path for the unmanned aerial vehicles. The method also
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comprises calculating mission objectives and the energy needs of the unmanned aerial vehicles to complete the mission objectives. The method then determines the most efficient combination of unmanned aerial vehicles to complete the mission objectives and assigns the tasks to the unmanned aerial vehicles. The unmanned aerial vehicles place, activate and test the sensors. The proposed system does not disclose spreading by CCS and method for CCS is also not present
George A. Mathew, Kunal Srivastava, Amit Surana, Shaunak D. Bopardikar [7] proposed a method of sensor node position determination for a sensor network is provided. A coverage distribution is defined based on a number of sensor nodes and sensor footprints of the sensor nodes. A desired position for each of the sensor nodes is determined based on the coverage distribution and a prior probability distribution defined on a bounded domain for the number of sensor nodes as a minimization of a distance between the coverage distribution and the prior probability distribution. The desired position to configure the sensor nodes is output. The proposed method does not explicitly talks about method of distribution however it talks about area optimization for placement of nodes.
The aim of the present invention is to propose a low cost & environment friendly system for time efficient and precise placement of SNs in large-scale candidate region.
The present invention is a generic model and can be used for the deployment of mobile or static SNs and can be used to effectively deploy SNs for any kind of deployment, such as barrier, blanket or point of interest based. The present invention is also suggested the techniques for the uniform distribution of SNs within a candidate region and also considered the emergency conditions raised by natural calamity which is ignored in most of the work by various researchers.
SUMMARY OF THE INVENTION
This invention proposes a model to randomly disperse the SNs from the sky. It comprises of a Centrifugal Cannon based Sprinkler (CCS) mounted on a deployment helicopter to aerially scatter SNs while traversing the candidate region. The CSS is an assembly of variable sized cannons connected to a common junction point (center of this junction forms the axis of rotation). This assembly is rotated with the help of motor in order to centrifugally launch the SNs through the cannons. Following are the main concerns of the proposed model:
• In this invention a well-defined mechanism for random scattering of SNs within a large scale candidate region.
• The invention minimizes the number of scans over the region and time taken to scatter the SNs within a large scale candidate region.
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The proposed System is low cost, environment friendly, time efficient, feasible and cost effective in comparison to the existing state of art models of deployment and can be opted as an effective alternative to deal with emergency conditions. The System is designed primarily to be used for random aerial deployments over large-scale candidate region.
Sensor Nodes (SNs) is a device designed to monitor the particular changes taking place in its surrounding and a crucial part in any remote monitoring system. Wireless sensor network (WSN) is a system formed by the set of wirelessly connected SNs placed at different geographical locations within a target region. The efficiency and effectiveness of any WSN is greatly affected by the precise placement of SNs. The manual placement of SNs is only feasible for small scale regions but it becomes tedious, when the size of a target region is extremely large and manually unreachable. In this invention, for fast and precise deployment of SNs in a large scale target region, an automated mechanism has been proposed. To launch the SNs from a moving carrier helicopter it uses an assembly of rotating cannons. To launch SNs accurately on the pre-computed desired locations the entire system is synchronized. The proposed System Model is inspired from centrifugal sprinkler used in agriculture fields for spraying water to the crops. It consists of an assembly of cannons of variable lengths, one end of which is connected to a common junction point called Multi-path Intersection Point (MIP). Before scattering SNs are dumped in to a hopper, while the flow control knob regulates the rate of spreading of SNs. The vertical pipes are used to connect the Hopper and MIP and SNs reaches from Hopper to MIP, through these pipes. The speed of the motor governs the angular velocity of the arrangement. This arrangement is referred as Centrifugal Cannon based Sprinkler (CCS) in this literature. The proposed model in the invention is time efficient and can be used for quick establishment of WSN in large scale target regions and the coverage achieved by the proposed model is very close to optimal. The proposed model works efficiently for plain surfaces but, in the hilly regions the performance degrade as vertical and horizontal lines of the reference grid may not remain parallel throughout the target region.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1: Deployment pattern for complete coverage.
Figure 2: Random scattering of SNs by CCS while moving on the traversal path.
Figure 3: Centrifugal Cannon based Sprinkler (CCS) system, wherein system comprises sensor nodes (SNs) (301), a Hopper (302) connected with a regulator (303), a motor (304) with a conveyer belt (305) attached at a frame (306) and an assembly of cannons (307)
Figure 4: Internal structure of Multi-path Intersection Point (MIP).
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Figure 5: Structure of Sensor Node capsule.
Figure 6: Working Centrifugal Cannon based Sprinkler (CCS) system.
Figure 7: Traversal track followed by helicopter.
Figure 8: Serpentine scan path followed by helicopter.
Figure 9: Concentric scan path followed by helicopter.
Figure 10: Parallel-lines scan path followed by helicopter.
Figure 11: Spherical scan path followed by helicopter.
Figure 12: Distance traveled for CCS and point to point dropping model using various region- traversing schemes.
DETAILED DESCRIPTION OF THE INVENTION
In this invention, a System Model is proposed as shown in Figure 2 which is inspired from centrifugal sprinkler used in agriculture fields for spraying water to the crops. It works on the principle of centrifugal energy, i.e., at specific RPM the centrifugal force exerted on the object depends on the distance at which it is held from the center.
It consists of an assembly of cannons (of variable lengths) one end of which is connected to a common junction point called Multi-path Intersection Point (MIP) as shown in Figure 3. Hopper is used for dumping and holding the SNs before scattering, while the flow control knob regulates the rate of spreading of SNs. The Hopper and MIP are connected with vertical pipe through which SNs reaches from Hopper to MIP. The lower portion of Figure 4 shows the internal structure of MIP where the circle on the surface represent the holes of the connected pipes (cannons) through which SNs are spreads in the deployment area. This arrangement is connected with a motor and conveyer belt which rotates the vertical pipe along with MIP. The angular velocity of the arrangement is governed by speed of the motor. Here after this arrangement will be referred as Centrifugal Cannon based Sprinkler (CCS) in this literature.
In this method of spreading, SNs are packed inside spherical containers as shown in Figure 5to ensure uniform shape and their protection. This packing consists of sticky material at the bottom side which acts as shock absorber when SNs strike with the surface in the deployment area when spread from CCS carried by flying helicopter. Each cannon fires the SNs with certain initial velocity which directly depends on the length of the cannon and angular velocity of the motor. Entry of SNs into particular pipe is stochastic in nature and so is its launch direction.The maximum radius within which CCS can deploy the SN largely depends on the length of the longest cannon of the CCS. It is equal to the horizontal distance Dmax covered by the SN launched from the longest cannon of CCS. However, the width of area within which the deployment takes place in a single scan is double of the Dmax.
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The flow chart (see Figure 6) shows the working of CCS. The working of CCS may be visualized as the concurrent execution of two threads.
Thread 1:
It is concerned with the movement of deployment helicopter above the scan path. The deployment helicopter mounted with CCS traverses the entire candidate region (with a constant speed and altitude) following the pre-determined scan-path.
Thread 2:
It is concerned with the working of sprinkler. The control knob regulates the flow of SNs to the sprinkler. After the release of a SN, it waits for the time interval 1/r seconds for the release of next SN, where r is the rate of deployment of SNs. The rate of deployment is dependent on the speed of deployment helicopter (VH), total number of SNs to be deployed and width of the scan-path (see Error! Reference source not found.7).
Followings are the notations used in flow chart.
 setHelicopterSpeed(VH): Assigns the speed of a deployment helicopter.
 setDroppingHeight(H): Assigns the flying altitude of a deployment helicopter.
 setDeploymentRate(r): Sets the deployment rate of CCS.
 setRPM(ω): Sets the angular velocity of CCS.
 startHelicopterMovementOnPath(): Initiates the movement of deployment helicopter above the scan path.
 moveOnPath(): Continues the movement of deployment helicopter above the scan path.
 endOfPath(): Returns “true” if end of the scan-path is reached else returns “false”.
 releaseSN(): load the SN for launch by random cannon of the sprinkler.
 launchSNFromCCS(): Launch the SN from random cannon.
 wait(t): Haults the SN regulator for time interval t before loading the next SN.
Scattering of SNs may proceed in several ways as below:
(a) Single point hovering: Deployment helicopter scatter SNs within a candidate region using CCS while hovering at certain fixed point above the candidate region (preferably at the center of candidate region), but this method is only suitable for small-scale candidate regions.
(b) Drop while moving: In order to cover large-scale candidate regions SNs are scattered while moving above it. Candidate region can be traversed in various patterns.
(i) Zigzag scan path (ZSP):In this deployment pattern, helicopter moves along a serpentine path separated by distance Dmax from boundaries and 2Dmax from adjacent scan lines (see Figure 8), where Dmax is a maximum horizontal distance up to which a SN can be fired from CCS located at point P and height H.
Inter scan Line Spacing (ILS): It is a distance by which consecutive scan lines are separated. ILS for Point-to-point deployment method is given by Equation (1). However, Inter Boundary-scan line Spacing (IBS) is𝐼𝐿𝑆2.
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𝐼𝐿𝑆=𝑟𝑚𝑎𝑥−{𝑟𝑚𝑎𝑥−(𝐵𝑐𝑟 % 𝑟𝑚𝑎𝑥)}⌈𝐵𝑐𝑟𝑟𝑚𝑎𝑥⌉
(1)
Where, Bcr is a Breadth of a candidate region. Total Path Length (TPL) for conventional method is given by Equation (2)
𝑇𝑃𝐿=(𝐿𝑐𝑟−𝐼𝐿𝑆)∗⌈𝐿𝑐𝑟𝑟𝑚𝑎𝑥⌉+(𝐵𝑐𝑟−𝐼𝐿𝑆)
(2)
Where, Lcris a length of a candidate region.
(ii) Concentric scan path (CSP): In this deployment pattern, helicopter moves along the concentric paths separated by distance 2Dmax (see Figure 9).
(iii) Parallel-lines scan path (PSP): This deployment pattern is similar to serpentine scan pattern with a modification that SNs dropping is paused while switching between scan lines thus ensuring more uniformity in deployment (see Figure 10).
(iv) Spiral scan path (SSP): This deployment pattern follows a spherical path separated by a distance Dmax from boundaries of a candidate region and 2Dmax from adjacent scan lines (see Figure 11).
Case 1: Without air resistance
Initial velocity Vinit with which SN is fired from any cannon Ci is given by Equation (3). Where 𝜔 is angular velocity (radians per second) and 𝑙𝑖is length of a cannon.
𝑉𝑖𝑛𝑖𝑡=𝜔𝑙𝑖
(3)
Time of flight t, of SN fired from any cannon is given by Equation (4).
𝑡=√2𝐻𝑔
(4)
Where, H is a dropping height and g is acceleration due to gravity (g = 9.8). Horizontal distance Dh(li) covered by SN fired from cannon Ci is given by Equation (5)
𝐷ℎ(𝑙𝑖)=𝜔𝑙𝑖∗√2𝐻𝑔
(5)
The location (𝑥𝑙,𝑦𝑙) of dropped SNs are obtained by Equation (6), where 𝑒𝑑 is a deployment error introduced due to various factors not considered in this Model.
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(𝑥𝑙,𝑦𝑙)={ 𝑖𝑓𝑞=1,𝑡ℎ𝑒𝑛𝑥𝑙←𝑥+𝑟𝑎𝑛𝑑(0,𝑒𝑑);𝑦𝑙←𝑦+𝑟𝑎𝑛𝑑(0,𝑒𝑑)𝑖𝑓𝑞=2,𝑡ℎ𝑒𝑛𝑥𝑙←𝑥−𝑟𝑎𝑛𝑑(0,𝑒𝑑);𝑦𝑙←𝑦+𝑟𝑎𝑛𝑑(0,𝑒𝑑)𝑖𝑓𝑞=3,𝑡ℎ𝑒𝑛𝑥𝑙←𝑥−𝑟𝑎𝑛𝑑(0,𝑒𝑑);𝑦𝑙←𝑦−𝑟𝑎𝑛𝑑(0,𝑒𝑑)𝑖𝑓𝑞=4,𝑡ℎ𝑒𝑛𝑥𝑙←𝑥+𝑟𝑎𝑛𝑑(0,𝑒𝑑);𝑦𝑙←𝑦−𝑟𝑎𝑛𝑑(0,𝑒𝑑)}
(6)
Where 𝑞 is a random number and given by equation (7)
𝑞←𝑟𝑎𝑛𝑑(1,4)
(7)
Case 2: Considering air resistance
The force 𝐹𝑑 exerted by air due to aerial drag, is given by Equation (8), where 𝑣 is the current velocity of SN, 𝐴 is cross-sectional area, 𝜌 is density of air (1.255 Kg/m3) and 𝐶𝑑 is a coefficient of drag for sphere (0.5).
𝐹𝑑= 12𝑣2𝜌𝐴𝐶𝑑
(8)
The velocity of SN is gradually increases with time when drooped from helicopter. The terminal velocity 𝑣𝑡 is the maximum velocity achieved by any SN on its path and given by Equation (9).
𝑣𝑡=√2𝑀𝑔𝐶𝑑𝜌𝐴
(9)
Algorithm 1: Computation of horizontal distance covered by a SN with air resistance.
getHorizontalDistance(H, M, A, vinit )
While H>=vdist
Fv ← (𝜌∗𝐴∗𝐶𝑑∗𝑣𝑣2)2⁄
av ← 𝐹𝑣𝑀⁄
vv ← 𝑣𝑣+(𝑔−𝑎𝑣)∗𝑑𝑡
vdist ←𝑣𝑑𝑖𝑠𝑡+𝑑𝑡∗𝑣𝑣
Fh← (𝜌∗𝐴∗𝐶𝑑∗𝑣𝑖𝑛𝑖𝑡)/2
ah ← 𝐹ℎ/𝑀
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vinit ← 𝑣𝑖𝑛𝑖𝑡−𝑎ℎ∗𝑑𝑡
hdist ← ℎ𝑑𝑖𝑠𝑡+ 𝑣𝑖𝑛𝑖𝑡∗𝑑𝑡
End
Return hdist
End
Model Assumptions
The model assumes that SNs are packed within a spherical container so as to ascertain uniform shape to be used by the scattering machine. It also provides a protective shield to ensure intact landing of SNs. Density of air ρ is assumed to be constant, i.e., 1.255 Kg/m3. Mass, M of SNs is 0.250 Kg.
Testing the Presented Model
Simulation of the proposed model has been performed on Quorum Communication (using the Java Simulator) and results are analyzed using Matlab.
The Simulation parameters and corresponding results of various traversing schemes used for random aerial dropping of SNs within a candidate region is shown in Table 1. It is observed from Table 1 that the coverage achieved by CCS model is 75% which is very close to 83% achieved by point-to-point dropping model. It is also observed that the total distance travelled by deployment helicopter in CCS dropping model is 7504 meters for PSP traversing scheme which is very less in comparison to 39904 meters required by point-to-point dropping model.
In CCS, travelling distance can further be reduced by increasing various parameters like RPM of rotating cannons and their lengths, so CCS dropping model can be calibrated according to the requirement and can be a more preferable option for deployment over large scale candidate region where fast and economical deployment is required.
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Table 1: Simulation parameters and results
Scheme
Scan-Path
RPM
Mass (Kg.)
ILS (m)
Scan Lines
Total Distance (m)
Time (Seconds)
Coverage
(%)
Number of SNs
CCS
ZSP
100
0.3
460
4
7504
250
73
428
Point to Point
ZSP
-
0.3
96
20
39904
1330
84
428
CCS
PSP
100
0.3
460
4
7504
250
75
428
Point to Point
PSP
-
0.3
96
20
39904
1330
83
428
CCS
CSP
100
0.3
460
4
8064
268
71
428
Point to Point
CSP
-
0.3
96
20
39723
1324
83
428
CCS
SSP
100
0.3
460
4
7676
255
70
428
Point to Point
SSP
-
0.3
96
20
38352
1278
83
428
Table 2: Horizontal distance covered by SNs dropped from CCS without considering air resistance.
RPM
Angular Velocity (𝜔)
Radians/second
Height (H) in meters
Horizontal distance (meters)
C1
C2
C3
C4
C5
C6
C7
C8
10
1.0472
1000
7.5
15
22.5
30
37.5
45
52.5
60
50
5.2360
1000
37.3
75
112
150
187
225
262
300
100
10.4720
1000
75
150
225
300
374
450
523.5
598.3
200
20.9440
1000
150
300
449
598.3
748
897.5
1047
1196
300
31.4159
1000
224.4
449
673
897.5
1122
1346
1570
1795
400
41.8879
1000
300
598.3
897
1196
1496
1795
2094
2393
12
500
52.3599
1000
374
748
1122
1496
1870
2244
2618
2992
Table 3: Horizontal distance covered by SNs dropped from CCS with air resistance.
RPM
Angular
Velocity (𝜔)
Height (H)
in meters
Horizontal distance (meters)
C1
C2
C3
C4
C5
C6
C7
C8
10
1.0472
1000
16.36
30.45
42.82
53.8
63.7
72.8
81.1
88.8
50
5.2360
1000
63.7
102.6
130.6
152.6
170.6
185.9
199.2
210.9
100
10.4720
1000
102.6
152.6
185.9
210.9
231.0
247.7
262.1
274.7
200
20.9440
1000
152.6
210.9
247.7
274.7
295.9
313.5
328.5
341.5
300
31.4159
1000
185.9
247.7
285.9
313.5
335.2
353
368.2
381.4
400
41.8879
1000
210.9
274.7
313.5
341.5
363.4
381.4
396.7
409.9
500
52.3599
1000
231
295.9
335.2
363.4
385.4
403.5
418.8
432.2
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References:
1. P. Corke et al., "Autonomous deployment and repair of a sensor network using an unmanned aerial vehicle," in IEEE International Conference on Robotics and Automation, 2004, pp. 3602-3608.
2. Peter Corke et al., "Deployment and connectivity repair of a sensor net with a flying robot," Experimental robotics IX, pp. 333-343, 2006.
3. Yoshiaki Taniguchi, TomoyaKitani, and Kenji Leibnitz, "A uniform airdrop deployment method for large-scale wireless sensor networks," International Journal of Sensor Networks, Inderscience, vol. 9, no. 3/4, pp. 182-191, 2011.
4. Mark A. Carlson, “Covert sensor emplacement using autorotational delivery mechanism”, U.S. Patent 8172173B2, issued 8 May 2012.
5. John Paul Strachan, Wei Yi, Jianhua Yang, “Installation platform for deploying an earth-based sensor network utilizing a projected pattern from a height” U.S. Patent 20120001017A1, issued 5 Jan 2012.
6. Usman Hafeez, David Mauer, “System and method for placement of sensors through use of unmanned aerial vehicles”, U.S. Patent 9454907B2, 27 Sep 2016.
7. George A. Mathew, Kunal Srivastava, Amit Surana, Shaunak D. Bopardikar, “Coverage optimization for sensor networks”, U.S. Patent 20170205490A1, issued 20 July 2017.

We Claim:
1. A Centrifugal Cannon based Sprinkler (CCS) system mounted on a deployment helicopter comprises sensor nodes (SNs) (301), a Hopper (302) connected with a regulator (303), a motor (304) with a conveyer belt (305) attached at a frame (306) and an assembly of cannons (307).
2. The system as claimed in claim 1, wherein said assembly of cannons is connected (of variable lengths) one end of which is connected to a common junction point or Multi-path Intersection Point (MIP).
3. The system as claimed in claim 1, wherein said Hopper is used for dumping and holding the SNs before scattering, wherein flow control knob regulates the rate of spreading of SNs.
4. The system as claimed in claim 1, wherein said Hopper and MIP are connected with vertical pipe through which SNs reaches from Hopper to MIP.
5. The system as claimed in claim 1, wherein internal structure of said MIP where the circle on the surface represent the holes of the connected pipes (cannons) through which SNs are spreads in the deployment area.
6. The system as claimed in claim 1, wherein angular velocity of the arrangement is governed by speed of the motor.
7. The system as claimed in claim 1, wherein SNs are packed inside spherical containers to ensure uniform shape and protection.
8. The system as claimed in claim 1, wherein said system consists of sticky material at bottom side which acts as shock absorber when SNs strike with the surface in the deployment area when spread from CCS carried by flying helicopter.
9. The system as claimed in claim 1, wherein said cannon fires the SNs with certain initial velocity which directly depends on the length of the cannon and angular velocity of the motor.