International Journal of Advancements in Technology
Open Access

Designing and Simulation Analysis of a Rocket in Ansys

Yashraj Asthana^{* *}Correspondence: Yashraj Asthana, Department of Mechanical Engineering, Indian Institute of Technology Patna, Bihar, India, Tel: 9050999578, Email:

Author info »

Introduction

Humans have always dreamt of flying up to which there is no limit. It was around 1799 when sir george cayley identified the forces acting: weight, lift, drag and thrust and then bring the concept of flying fixed-wing machine, with separate systems for propulsions, lift, controls, designing a successful glider to carry a human aloft. To sustain aerodynamics flight, we require continuous working propulsion, unlike other transportations such as land and water, as they can survive without propulsion. By taking advantage of moving in a fluid, propulsion is achieved by the engines that through air backwards at a very high speed and get the same amount of force according to newton’s third law of motion, which pushes their machine forward. This force is known as thrust and the other force which opposed it is the drag force. For a space vehicle to run, its propulsion, i.e., thrust force, must be more than drag force and vehicle’s weight. If the propulsion thrust is not enough to overcome drag force and the vehicle’s weight, then the space vehicle will not fly.

What is aerospace propulsion?

Propulsions is the phenomena of pushing fluid out of nozzle at a very high speed and then getting the same amount of thrust which moves the vehicle in forward direction (Figure 1). The energy source used in it is generated by combustion of fuel and propellant (usually oxygen). Both substances are stored in separate air-tight cylinders. A preferred mixture of fuel and propellant is transferred to combustion chamber in which mixture is ignited and energy is generated.

Figure 1: Propulsion section.

After that this high energy exhaust is passed through the nozzle. When it passes through the nozzle its kinetic energy increases and pushes the fluid behind the rocket. In return the fluid also exerts the same amount of force on the rocket which helps in overcoming drag force and its weight and moves the rocket forward.

What is a rocket?

A rocket is an aircraft or a projectile in space which helps in sending or launching guided missile into space [1]. A large amount to hot exhaust is expelled by its bottom. When we see gas molecules in the exhaust, they do not weigh much individually but the velocity with which they exit the rocket’s nozzle is very high, thus by exiting they provide a lot of momentum, helps in giving further movement to the Aircraft in opposite direction. Satellites are launched into space with the help of rocket. Its weight is about 165000 pounds, when empty. For proper launching of satellites into space, it is required to develop a very high momentum such that it gave an approximate speed about eight kilometers per second to the rocket (Figure 2).

Figure 2: Rocket interior.

What kind of materials are used to make a rocket?

A material which has a very high strength and has less weight at the same time is the current requirement of the scenario. It is so because rocket must withstand or overcome a high amount of force at its launch [2]. Therefore, for the mainframe, rockets use grade titanium or aluminum since both are very strong as well as have light weight. One material is also an appropriate option other than these two, which have the same property and that material is carbon in the form of composites. Because of this, the value or cost of carbon composite materials is very high. However, aluminum has a low melting point. So, for mitigating this factor Silica fibers are used as heat shields as they have great heat insulation properties. Moreover, a layer of glass is also employed to coat these fibers for increasing its effectiveness [3].

Features of a rocket

Certainly, there are three main features of a Rocket:

(i) High thrust in mega newton units.

(ii) High exhaust speed (ten times the speed of sound in atmosphere).

(iii) High thrust-to-weight ratio [4] (Figure 3).

Figure 3: Ansys fluent.

Methodology

Working of a rocket

Imagine a person standing on a skateboard, throwing a ball in a forwarding direction. The skateboard will move in a forward direction, but the person will move backwards [5]. The person moves backwards because when he applied force on the ball, the equal and opposite force applied to him by the virtue he moves backwards. Newton’s 3rd law of motion is the reason behind this. A thrust is produced in a rocket by the high-speed fluid exhaust [6]. This exhaust is produced by the combustion of propellant and oxidized in a chamber at very high pressure (40-210 bar). The exhaust is then passed through a converging-diverging supersonic nozzle in which the internal energy is converted into kinetic energy, which results in the propagation of a high velocity which pushes the rocket body in the opposite (upward direction). For the efficient performance of a rocket, high temperature and high pressure are mandatory requirements. Due to this, a more extended nozzle is then fitted in the rocket, resulting in high exhaust velocity. Thus, a high amount of speed and thrust is provided to the missile, which also increases its thermodynamic efficiency. An approximate equation for calculating the net thrust of a rocket engine is given below [7].

F_n=mv_e=mv_e-act+ A_e (P_e-P_amb)

Where:

m=Exhaust gas mass flow

v_e=Effective exhaust velocity

v_e−act=Actual jet velocity

A_e=Flow area at nozzle exit plane

P_e=Static pressure at nozzle exit

P_amb=Ambient pressure

The mv_e−act term represents the momentum thrust, which remains constant at a given throttle setting, whereas the pressure thrust term is represented by the term A_e(P_e−P_amb) [8].

We know that with increasing altitude, the atmospheric pressure decreases, thus the pressure thrust term increases. Therefore, at full throttle, the net thrust of a rocket motor improves. At the surface of the earth the pressure thrust may be reduced by up to 30%, depending on the engine design. This reduction drops roughly exponentially to zero with increasing altitude (Figure 4).

Figure 4: Rocket measurements.

How is rocket designed?

Certain factors on which designing of a Rocket depend on the amount of thrust it should produce, its velocity range, and these factors depend on the type of environment from which it will be launched, viscosity of the fluid in which it will travel etc. Previously, there were no software, so practical experimental methods were used, which were so expensive, resulting in wastage of time and money. But now a days, there are various simulation software in which we can design and experiment analytically and can change its design according to our requirements (Tables 1 and 2).

Table 1: Solution settings and boundary conditions.

Table 2: Free stream conditions.

Software used

We use ANSYS fluent 2021 for the designing and testing of rocket in viscous condition. It majorly consists of five parts (Table 3).

Table 3: Analysis of drag force and pressure on rocket.

In the geometry section, 2D cross-section of rocket is designed and it will be then converted to 3D image. Special care should be taken because if there is any problem in geometry section then we will not get the required solutions and all the four parts are linked to this part.

In meshing the 3D image formed is divided into 1000 or more hexagonal parts to define its shape properly for getting the realistic forces on its body (Table 4).

Table 4: Analysis of drag force and pressure on rocket.

In setup and solutions part, type of material which rocket is made up of is defined and boundary conditions are also defined such as temperature, pressure, viscosity. After that, iterations are made, and calculations occur.

In the results section, drag force acting on the rocket airframe will be calculated.

Results and Discussion

Plotting the key points first, we will create the correct dimensions of the rocket according to the coordinate points given.

Making edges Join these points to make edges, we must be sure that right key points are joined with each other as it is very critical portion of the process.

Making faces the 2D image which is formed is converted to 3D image by using extrusion revolve command.

Creating enclosures rocket is divided into separate parts and enclosures are created around each part in which forces on that part will be measured.

Applying mesh in the mesh part we divide into the distinct elements and then apply proper sizing and then meshing to each part and then generate the required mesh.

Now in the setup and solution part, we define boundary conditions given above such as nozzle inlet temperature, free stream temperature, inlet gauge pressure, viscosity, gradient, viscous model type. We will turn on energy equations and defined the material as air and set its density to ideal. At last, we will run iterations and calculations.

At last, we will enter the solutions part and obtain the drag force acting on the rocket which we have designed.

The CFD analysis of rocket which we have designed is done by ANSYS 2021 to calculate the drag force acting on the rocket airframe and nozzle. We will plot mach number contour also. The energy method is turned on as well as Density based calculations are made because we consider fluid to be compressible. K-epsilon-2 equation model is selected. Second order upwind is selected for both turbulent dissipation rate and turbulent kinetic energy. CFD analysis on ansys software is a great method of testing rocket in realistic conditions or situations because experimental methods are very costly and results in the loss of money as well as time.

Conclusion

As per our results, it is showing that pressure acting on a rocket is in the units of kPa which is indeed an average amount as the size of the rocket is very large and it is also heavy. The average drag on it is 1.33e+4. All the concepts have been subjected to the analytical work and gave much better and realistic results. It means that given coordinates of the rocket are correct and hence it can be manufactured accordingly.

References

1. Farokhi S. Aircraft propulsion. 2014.

   [Google scholar]

2. Flack RD. Fundamentals of jet propulsion with applications. 2005.

   [Google scholar]

3. Sutton GP, Biblarz O. Rocket propulsion elements. 2016.

   [Google scholar]

4. Petrescu RV, Aversa R, Apicella A, Petrescu FI. Modern propulsions for the aerospace industry. ARPN J Eng Appl Sci. 2018;11(2):715-55.

   [Crossref] [Google scholar]

5. Mishra DP. Fundamentals of rocket propulsion. 2017.

   [Crossref] [Google scholar]

6. Maidana CO. Thermo-magnetic systems for space nuclear reactors. Springer Br Appl Sci Technol. 2014:53.

   [Google scholar]

7. Pandey KM, Yadav SK. CFD analysis of a rocket nozzle with two inlets at MACH 2.1. J Environ Dev. 2010;5(2):308-21.

   [Google scholar]

8. Turner MJ. Rocket and spacecraft propulsion: principles, practice and new developments. Springer Sci Bus Med. 2008.

   [Google scholar]