Running head: GYROSCOPIC STABILIZATION VS. STABILIZATION FINS 1

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1 Running head: GYROSCOPIC STABILIZATION VS. STABILIZATION FINS 1 Gyroscopic Stabilization vs. Stabilization fins in Model Rocketry Donald S. Corp, Maccoy G. Merrell Waxahachie Global High School January 12, 2017

2 GYROSCOPIC STABILIZATION VS. STABILIZATION FINS 2 Table of Contents Abstract 3 Gyroscopic Stabilization..4 Detrimental Effects of Gyroscopes..4 Beneficial Effects of Gyroscopes...4 Design of Gyroscopes for Stabilization...5 Gyroscopic Stabilization in Practice...5 Fin Stabilization..5 Detrimental Effects of Fins.6 Beneficial Effects of Fins...6 Design of Fins for Stabilization..7 Fin Stabilization in Practice 7 Comparison of Methods of Stabilization 7 Advantages of Fin Stabilization over Gyroscopic Stabilization.8 Advantages of Gyroscopic Stabilization over Fin Stabilization.8 Practicality of Each Form of Stabilization..8 References..9

3 GYROSCOPIC STABILIZATION VS. STABILIZATION FINS 3 Abstract Fins have been used for stabilization in every aircraft invented. The passing of the space age introduced a new form of stabilization. Gyroscopes, like fins, stabilize aircraft. However, each type of stabilization works via different mechanisms and grant different advantages. Fins use the air current around quickly moving objects to stabilize aircraft into a stable direction, based on the direction of thrust. Gyroscopes, on the other hand, use rotational inertia to guide the rocket into the position at which it started. While both forms of stabilization are practical in commercial and professional aircraft, the field of model rocketry is different. In model rocketry, the generally low altitudes combined with low speeds introduces a problem. Despite the low speeds, fins are still superior when stabilizing model rockets. Fins do not require added weight in order to be effective, unlike gyroscopes, and thus are much more practical in model rockets. The small motors of model rockets cannot support added loads, such as gyroscopes. Keywords: fins, gyroscopes, model rocketry, stabilization

4 GYROSCOPIC STABILIZATION VS. STABILIZATION FINS 4 Gyroscopic Stabilization Gyroscopic stabilization operates via gyroscopic precession. As forces act perpendicular to the axis of rotation, the gyroscope along with whatever is directly attached to it experience a correcting force. The original orientation of the rocket at the time which the gyroscope begins to spin, is held until the gyroscope ceases to spin. Gyroscopes are often large and heavy. Gravity is a natural need of the gyroscope in order to produce Figure 1 Mx = Iz ' ' My = 0 Mz = 0 Figure 1. Demonstrates the forces at work and their location, as well as the calculations used to determine force. (Beal, 2003). force. (Lewin, 1999) Detrimental Effects of Gyroscopes The use of gyroscopic stabilization in rocketry exhibits numerous effects on the rocket that are not intended. The added weight can decrease overall flight height and time. It has a considerably high energy expenditure as well, due to the speed the gyroscope must rotate. As a result of this, safety hazards are also increased. Malfunctions, as in other types of stabilization, can completely disable the system. Beneficial Effects of Gyroscopes Despite the various drawbacks of gyroscopic stabilization, benefits also exist. Gyroscopes do not need air current to function, so they can be stowed within the vessel rather than on the outside of it. This causes a significant reduction in drag. Another benefit to the internal system is that it cannot be damaged by debris. Even more so, maintenance can be performed on the

5 GYROSCOPIC STABILIZATION VS. STABILIZATION FINS 5 stabilizer without leaving the vessel. In the case of model rocketry, retrieval can be significantly less costly as the gyroscope is protected within the rocket itself. (Rogers, 2017) Design of Gyroscopes for Stabilization Stabilization gyroscopes are often designed for great force within a small area. The gyroscope contains a heavy metal disk, attached to a machine-driven axis. The gyroscopes translational axis are restrained, but the rotational axis are allowed to move. The movement of the rotation axis directly effects the rocket s orientation, causing it to remain upright (Massachusetts Institute of Technology, 2008). The ability of the gyroscope to stabilize rockets comes from the natural consequences of rotational inertia. As the disk spins, forces are generated perpendicular to the axis of rotation and the acceleration of gravity. As a result, the gyroscope remains fixed upright, perpendicular to the horizon. Gyroscopic Stabilization in Practice. Gyroscopic stabilization is already common practice among vehicles of other terrains. One example are yachts. The ships are now equipped with stabilization gyroscopes to keep it level in stormy and rough waters. Gyroscopes are also utilized in aircraft, primarily for guidance. Helicopters utilize gyroscopes in order to stabilize the rotational axis of the craft, preventing them from flipping over during flight. All orbital spacecraft use gyroscopes to position themselves within space, where other forms of positioning devices would not work. Fin Stabilization Fin stabilization is the more traditional route to take when designing a rocket. The fins do several things to keep the rocket steady. The fins of a rocket rely entirely on aerodynamic drag in order to effect the rocket. When the rocket is in motion the rocket is greatly affected by the air around it and stability fins take advantage of this. Control fins are very similar but can adjust

6 GYROSCOPIC STABILIZATION VS. STABILIZATION FINS 6 their orientation in order to charge the direction of the rocket instead of maintaining it like in a stability rocket (Nakka, 2001). The nature of fins in rocketry means that certain characteristics of the rocket will increase. Drag, as the primary driving force behind the stabilization, will increase. Compared to other stabilization methods, fins are fairly light weight. Detrimental Effects of Fins The drag produced by fins naturally slows the rocket down, by reducing the forward thrust of the rocket. Another flaw within finned rocketry is the need for speed. At speeds approaching zero, the rocket loses all stabilization. This is due to the lack of air current to produce drag. If a fin becomes damaged during flight, the drag the rocket produces can be increased significantly, and the damage cannot be repaired until the flight has been completed. In model rocketry, this can mean that the entire flight fails. Beneficial Effects of Fins The advantages of finned rocketry come Figure 2 Shows the calculations and visual correspondence of drag. (Benson, 2014) primarily from a fin s lightweight structure and selfpowered correction. Due to fins being flat, their volumes are minimal, yet their surface area remains high. Fins do not need to be powered in order to stabilize a rocket, other than by the movement of the rocket itself. Another advantage to finned rocketry is their weight. Typically, systems on rockets are incredibly heavy, and greatly limit the distance a rocket can go. Fins are lightweight, due to their relatively low volume, and thus can be added in large amounts, or added in minimal amounts, with minimal effects.

7 GYROSCOPIC STABILIZATION VS. STABILIZATION FINS 7 Design of Fins for Stabilization A fin s primary purpose is to remain unhindered by air currents in the upwards direction, while using the drag of the air directly to the sides of the fin to hold the rocket in place (Bensen, 2015). In order to accomplish this, fins are generally thin, with large surface areas on each side. The effects produced by fins create similar forces to twisting a knife in a block of cheese. Similarly, increasing the length of the fins increases the force the rocket can utilize to prevent destabilization. Fin Stabilization in Practice. Fins are used in all aircraft today, including in helicopters and in spacecraft. For a demonstration think of sticking your hand out of the window of a moving automobile. When your hand is up, perpendicular to the ground, the air pushes back. If your hand is parallel to the ground the air rushes by much easier and you hand feels very little effect. Now the most important part. If you have you hand held at an angle the moving air would push your hand in the direction of your fingertips. The commonplace forces behind fin stabilization have allowed for physicists to study and explain such forces. This resulted in fin development to be much more advanced and efficient than other forms of stabilization. Comparison of Methods of Stabilization Fins and gyroscopes are the primary methods of stabilization in aircraft. Fins are lightweight and provide a non-expensive form of stabilization as well as free up interior space. On the other hand, gyroscopes work at any speed or altitude, and allow for internal maintenance to be done in flight. Stabilization fins are much more common place among personal aircraft and commercial airplanes, while gyroscopes are abundant in expensive craft such as helicopters and spacecraft. Each method of stabilization works, however their effects on the rocket differ greatly. Advantages of Fin Stabilization over Gyroscopic Stabilization

8 GYROSCOPIC STABILIZATION VS. STABILIZATION FINS 8 Fin stabilization s domination of current stabilization systems is not without reason. Fins are relatively lightweight and are incredibly efficient due to their use of the natural effects of air travel. Fins also are simple, with stabilization fins not having any moving parts and little to no electricity requirements. Their designs can be changed to produce different effects, such as maximizing stabilizing force, or minimizing drag. Advantages of Gyroscopic Stabilization over Fin Stabilization Gyroscopes represent the new era of stabilization technology. Their stabilizing forces are independent of speed and location, allowing gyroscopes to work in a wide array of environments. The ability for gyroscopes to be located nearly anywhere on a vessel allows it to be placed internally, allowing it to be worked on from inside the vessel. The amount of stabilizing force the gyroscope exhorts on the rocket can be changed simply by exchanging the weighted disc for a heavier or lighter one, and increasing or decreasing the rate at which the disc spins. Practicality of Each Form of Stabilization Fins and gyroscopes both serve as viable forms of stabilization in large craft, from drones to space shuttles, but fins are superior in terms of model rocketry. In real rocketry, the lack of atmosphere at high altitudes justifies the use of gyroscopes, allowing the craft to stabilize in an environment where fins would not allow. In contrast, model rocketry never experiences an air free environment. Fins are lighter weight, allowing more of the rocket s limited thrust to be put towards altitude than carrying a large load. As a result, fins are the superior form of stabilization due to their light weight and velocity based stabilizing forces. References Beal, R. (2003, May). Derivation Of The Equations Of Gyroscopic Motion. Retrieved from Gryoscopes.org:

9 GYROSCOPIC STABILIZATION VS. STABILIZATION FINS 9 Benson, T. (2015, October 22). Rocket Stability. Retrieved from Benson, T. (2014, June 12). Size effects on drag. Retrieved from NASA: Lewin, W. (1999). Lecture 24: Rolling Motion, Gyroscopes. Boston, Massachusetts, United States of America. Massachusetts Institute of Technology. (2008) Gyroscopes and angular momentum. In Module: Department of Physics (16). Retrieved from /www/materials/modules/guide16.pdf Nakka, R. (2001, August 6). Richard Nakka s Experimental Rocketry Web Site. Retrieved from Rogers, J. (2017, January 1). Gyro Stabilizers and Fin Stabilizers, What you Need to Know. Retrieved from Jimmy Rogers Yacht Broker: gyro-stabilizers-and-fin-stabilizers-what-you-need-to-know/