Safe way to transport human by utilizing engineering principals
Introduction
In military a catapult is a ballistic device for launching a projectile over a long distance with no aid of explosive gadgets. The need for unmanned aerial vehicle (UAV) catapult catapult launch was initiated due to the following reasons. UAV catapult launch eliminates the need of a take -off path. In addition, for a UAV to take off from runway it requires additional fuel. This fuel will increase the total weight of aircraft. There are some systems designed for launching devices (LDs). During the design of these LDs it was found that they should be of lightweight, have small storage space and require minimal personnel to operate. The categories of LDs are:
o
Pneumatic
o
Hydraulic
o
Bungee cord
o
Kinetic energy
o
Electromagnetic
o
Rocket assisted take-off (RATO).
UAV launching device selection
The task of a LD is to hand over to unmanned aerial vehicle the accumulated energy so that as the UAV is leaving the catapult catapult it has speed more than than 15% for a given UAV. UAV. The Pneumatic LDs (hydraulic) are the best because they have large catapult power and also they can launch multiple UAV types.
They have uniform acceleration in their launch rails. However, they are complex in construction thus making them unreliable. RATO device is has almost zero length launch and has higher acceleration. It is the most reliable drive for launching UAV in adverse environmental conditions.
Figure1. MDS hercules pneumatic launcher with aerial target banshee
- Max UAV launch mass is 250 kg - Max UAV launch speed is 55 m/s
Figure 2: Aries ALPPUL LP-02 pneumatic launcher with UAV SIVA - Max UAV launch mass is 360 kg - Max UAV launch speed is 34 m/s
Bungee catapult employs stored energy in a powered, highly elastic bungees to launch a UAVs. LD with elastic cord employs simplest design structure compared to other design of LDs. Due to their simple design, they have low purchase price and low cost of maintenance. However, they have less launch take-off power with take-off weight of 50 -55kg. Bungee catapult is disadvantageous in that there is initial jerk which can affect payload of a UAV.
Take-off of UAV catapult system
For take-off, the plane is moved by flight crew into position at the rear of catapult and the tow bar is attached on the plane’s front wheels to the slot
in the shuttle. At the same time, the flight crew raises jet blast deflector (JBD) behind the plane. When the holdback, catapult and JBD are position, and the necessary checks have been made, the shooter (catapult officer) makes the catapult ready. When the vehicle is ready, the shooter opens valves to fill the cylinders of catapult with stem of high pressure. The steam is responsible for force of propelling the pistons at high speed, slinging the forward part of the plane to create sufficient lift for take-off.
The catapult officer will monitor the
pressure build up and when it is up to the necessary level the will operator of the plane (pilot) will blast the engine.
The holdback will keep the plane
on the shuttle as the engine is generating considerable thrust.
The catapult
officer will release the pistons; force will cause the holdbacks to release as the steam pressure slams plane and shuttle forward. Finally, the tow bar pops out of shuttle to release the plane. The system can drive an aerial vehicle of 20, 000kg from 0 to 165 miles in two seconds.
Figure 3: An F/A-18 Hornet launching from the USS George Washington
Landing of aerial vehicle using catapult system is a difficult task for pilots. The flight deck runway space is around 150 meters for landing planes and it is not sufficient for high speed heavy jets. To land on the deck, the plane is built with a tail hook. The pilot will have to snag the tail hook on an arresting wire, which are made of high-tensile steel wire. The wires are stretched across the flight deck and are attached to the ends of the hydraulic cylinders stationed below the deck. When the tail hook snags the arresting wire, it pulls the wire out and the hydraulic system absorbs the kinetic energy to bring the plane to a stop. The wires can stop 24, 500 kg aircraft travelling at 241 km/h.
Figure 4: An F/A-18C Hornet catches an arresting wire on the USS Nimitz.
Conclusion
From this research it was found unmanned aerial vehicles use the principle of catapult system in their operations. The catapult system like the Bungee cord can be used in adverse environmental conditions thus they can be in rescue operations. Also this catapult system can be used in public transportation whereby an aircraft of total mass of 24, 500 kg can travel 241 km/h. Also from this research, it was found that the catapult system employed to design aircrafts for use in parks for the purpose of fun and amusement.
References
1. Scientific Technical Review, 2016,Vol.66,No.4,pp.22-28
2. Zoran Novaković Integration of Тactical - Medium Range UAV and Catapult Launch System 3. http://science.howstuffworks.com/aircraft-carrier4.htm