California Polytechnic University,

Pomona

Hybrid Rocket Team

October 2nd, 2015

California Polytechnic University Pomona Aerospace Engineering Department

Dr. Donald Edberg

2

Executive Summary

A group of Aerospace Engineering students in the Undergraduate Missiles Ballistics and

Rocketry Association was put together to construct Cal Poly Pomona’s first ever Hybrid Rocket.

Only one member out of this 15 people team had previous experience with rocketry so it was

expected for the group to run into problems and mishaps, but the main purpose was to use the

principles engineering learned in class and apply them to a real project on a bigger scale. Given a

set criteria of achieving a launch to 10,000 feet above ground level with a max drift of 2,500 feet

from the launch rail, the team came together and helped one another overcome obstacles which

even included an entire trip to the Mojave Desert where the rocket didn’t launch. The rocket was

to be propelled by a hybrid motor consisting of an oxidizer and a solid fuel in which this case the

oxidizer was nitrous oxide. Everything was built around the motor so that the center of gravity

and center of pressure can be adjusted to maintain optimum results. Two 4 foot carbon fiber

tubes were used with a 6 inch inner diameter that held two 4 foot card board tubes that contained

the frame of the inner rocket. The frame held the motor together and housed the electronics bay,

ejection charges, and the parachute, but most importantly the frame kept the entire rocket strong

enough to withstand all the forces including a crash landing.

After several failed attempts due to the ground support equipment not functioning as

planned, the rocket finally launched on the 5th

attempt during 15- 20 mph wind conditions where

it soon began to tilt and much of its vertical climb was lost due to the distance it was covering

horizontally. It is estimated the rocket reached a max altitude between 2,500 ft. and 3,000 ft with

a drift distance of 880ft. and a flight of 20 seconds before it crash landed due to the momentum

of the rocket tearing off the parachute during deployment. Unfortunately the data recovered was

not helpful because the datalogger did not register the correct data due to a malfunction which

was most likely caused by the crash landing. Several lessons were learned and a lot of experience

was gained during this project. The rocket might have crash landed, but not a single person on

the team gave up hope after so many failed attempts and the team was finally able to launch the

first ever Hybrid Rocket made at Cal Poly Pomona.

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Table of Contents

Section Page

Title Page 1

Executive Summary 2

Table of Contents 3

1.0 Introduction 4

2.0 Team members & Roles 5

3.0 Aerodynamic Analysis 6

3.1 Structural Analysis 8

3.1.1 Buckling Analysis 8

3.1.2 Lateral Load 12

3.1.3 Compression Analysis 16

3.2 Controls Analysis 20

3.3 Recovery System Analysis 22

3.3.1 Recovery System 22

3.4 Safety 28

4.0 Construction Design 33

4.1 Manufacture and Materials 36

4.2 Integrate Controls and Batteries 40

4.3 Parachute and Shock charges 41

4.3.1 Parachute production 41

4.3.2 Parachute ejection charges 43

4.4 Construction assembly 44

5.0 Testing 49

5.1 Electronics 49

5.2 Ground Equipment 49

5.3 Parachute 51

6.0 Procedure 53

6.1 Launch Pad 53

6.2 Ground Support Equipment 54

6.3 Flight Motor Assembly 56

7.0 Post Launch Summary 60

7.1 Results 61

7.2 Conclusions 69

8.0 Recommendations 81

9.0 Appendix 82

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1.0 - Introduction

Mission criteria

The project’s mission is to design and execute Cal Poly Pomona’s first hybrid rocket

using an M-class hybrid motor consisting of a liquid oxidizer and solid propellant. The rocket

design will also be able to reach a minimum apogee of 10,000 feet above ground level and a

maximum drift distance of 2,500 feet. The altitude will be measured with an altimeter. The

rocket shall be reusable and weigh no more than 50 pounds. The propulsion system should be

capable of throttle control and the entire rocket shall be recovered with minimal damage. This

project is designed to impart experience on building and constructing large rockets. Whether the

launch is successful or not, we hope to pave the way for future students at Cal Poly Pomona to

build upon and experiment with rockets of their own using ours as a foundation.

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2.0 Team members and roles

Moiz Khan - Team Leader

Josh Kennedy (Safety Officer) - Aerodynamics

Isaac Orozco - Aerodynamics

Guadalupe Romero - Aerodynamics

Miguel Lopez - Aerodynamics

Omar Benitez - Systems Engineering

Francisco Davila (Deputy) - Propulsion

Gerladson Evangelista - Propulsion

Tai Chi Kieu - Structures

John Tangan - Structures

Victor Sanchez - Structures

Arvin Artoonian - Recovery System

Fernando Sanchez - Recovery System

Alejandra Castellon - Controls

Austin Miller - Controls

The Aerodynamics group will be in charge of coming up with the calculations of drag

caused by the fin design and also the nose cone that is chosen. From their findings, the design

will be adjusted so the rocket can theoretically achieve its mission criteria.

The propulsion group will be working with the structures group to provide the forces that

are going to be seen on the structure of the rocket and how the structure will have to be modified

so it can take the load.

The Recovery System group will be designing an entire chute from scratch which will be

suitable for the hybrid rocket. They will find the drag caused by the chute to slow the rocket

down during descent to an acceptable velocity for the landing and the drift distance.

The systems engineering group will make sure all processes of the project are on task and

all the parts are available for the build. They will also be working with the controls group.

The controls group will be in charge of the rockets electronics which will control the

ejection charges and also collect data of the rockets flight characteristics.

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3.0 – Aerodynamic Analysis

The M-1000 motor is manufactured by Hypertek and made to produce 395 lbf of average thrust

with a 9.0 seconds thrust duration. This will definitely accelerate the rocket very quickly and the

aerodynamics must be sufficient so that this power is optimized in the vertical direction so the

maximum altitude can be achieved.

Drag coefficient can be determined experimentally or analytically, but first dynamic pressure is

found by

𝑞 =1

2𝜌𝑣∞

2

This gave us drag force

𝐷 = 𝑞𝐶𝑑𝐴

The main types of drag affecting a rocket are: skin friction which is caused by the kinematic

viscosity of air. Pressure drag, that is directly affected by the body geometry and wave drag

when a rocket reaches supersonic speeds.

Aerodynamics and stability are important on a rocket performance. The center of

pressure is the point through the sum of all aerodynamic forces act. To have a stable rocket the

CP should be aft of the center of gravity or CG. There are many ways to find the center of

pressure, one of them is by using the Barrowman Equations. There are some assumptions that

have to be made in order of using it. Small angles of attack, speeds lower than the speed of

sound, smooth airflow over the rocket, large length to diameter ratio, no discontinuities in the

body, axial symmetry, and thin flat plates.

𝑥𝐶𝑃 =𝛴𝐶𝑁,𝛼𝑖𝑥𝑖

𝛴𝐶𝑁,𝛼𝑖

where the normal force coefficient 𝐶𝑁,𝛼varies from with component geometry, each rocket

component i has its own center of pressure at 𝑋𝑖 from the nose cone tip. The total CP distance is

a weighted average of the component CP distances.

The problem with unstable rockets is that they can spiral out of control under small

disturbances, compared with stable rockets in which their trajectory is not perturbed by wind.

When rockets reach transonic and supersonic speeds, drag forces tend to increase, and want to

break apart the rocket. For strength, carbon fiber and slow curing epoxy was used on the body.

Also avoid large aspect ratios due to bending moments, which can lead buckle and failure of the

rocket structure.

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Rectangular cross section fins were used in the hybrid rocket. Fins are very important on

the design of a rocket; here are different types of fin designs and their characteristics.

Figure 3.0.1: Different types of fin designs.

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3.1 – Structure Analysis

3.1.1 Buckling Analysis of the Lower Tube:

Stress analysis is key to designing a vehicle capable of handling the great forces associated

with rocket flight. When the structure is loaded, it can collapse even if the stress is lower than

the yield strength of the material. This phenomenon is called Buckling. Buckling takes place

when the static load coincides with the specific load where elastic stability is lost. The shape of

the deformation at the critical load is called a Buckling Mode.

There are two methods for analyzing whether buckling will take place in a structure.

Apply an actual load.

Apply a unit load (1N)

Fig 3.1.1 shows a lower fuselage tube of the rocket, where the load of entire rocket weight

(155.7N) will apply on. Here, we need to make sure that the lower tube will not buckle before we

start to assembly the rocket.

Figure 3.1.1:

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Using Finite Element Method on CATIA V5 to Analyze the Tube Buckle:

In order to conduct the analysis, mesh needs to be applied to the tube. Here Constant-Strain

Triangular (CST) was used to divide the structure into small triangular units for analysis.

Figure 3.1.2: Meshing

Restraints and loads were applied to the column. The bottom edge was restrained with a clamp

with neither rotation nor displacement. An applied force of 155.7N was distributed on the top

edge since the entire rocket will connect to the lower tube to stand up on.

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Figure 3.1.3: Constraints and Loads

Static analysis was performed to obtain the Von Mises stress with the aim of comparing it with

the yield stress of the material of the tube to make sure it stays within in an acceptable range.

Figure 3.1.4: Statics Analysis

Buckling analysis was performed with a Number of Modes: 10, Maximum Iteration Number: 50,

and Accuracy: 0,001.

Figure 3.1.5: Buckling Analysis

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After compute by the computer, a result of 10 buckling mode was obtained with 10 critical load.

1st Mode: Pcr = 9139,98N

Figure 3.1.6: 1st Buckling Mode

10th Mode: Pcr = 27450N

Figure 3.1.7: 10th Buckling Mode

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At this point, comparing the load from the entire structure to the critical load at the 1st mode, it is

safe to assemble the part, since the load is much smaller compared to the critical load.

To evaluate sensitivity, the lateral load was also applied.

3.1.2 Lateral Load on the Tube

Similar to the longitudinal load, the displacement result for the lateral load was obtained as

Figure 3.1.2.1 below.

Figure 3.1.2.1 lateral Load

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10 buckling modes are obtained with 10 critical loads in lateral direction.

1st Mode: Pcr = 2153,36N

Figure 3.1.2.2: Buckling Mode 1

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5th Mode: Pcr = 2205,75N

Figure 3.1.2.3: Mode 5

15

9th Mode: Pcr = -2285,96N

Figure 3.1.2.4: 9th Mode

Notice here, both positive and negative critical loads due to the lateral force can cause the

buckle on both sides of the column.

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3.1.3 Compression Analysis on the Fin

Since the entire rocket will be supported by 4 fins that are 900 from each other. One fin is

analyzed and symmetry is used to find the results for each one.

Figure 3.1.3.1: Geometry of the fin

Since the axial load applied on each fin will be the same, it can be assumed that each fin has

43.4N of force being applied on it.

Meshing is applied on the fin to begin using FEM, here CST is still being used to divide the fin.

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Figure 3.1.3.2: Meshing on Fin

Next step is applying the load and restrain on the fin. Here the load of entire rocket will be

divided by four since symmetry is used.

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Figure 3.1.3.3: Applying Load

Figure 3.1.3.4: Applying Restrain

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After computing the element on the computer Von Mises stress’ is obtained to compare with the

yield strength and the principal stress’ of nodes on the fin.

Figure 3.1.3.5: Von Mises stress

Figure 3.1.3.6: Principle Stresses

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3.2 – Controls Analysis

The electronics used in the Hybrid Rocket were an Arduino Mega 2560 connected to a

10 degree of freedom sensor board from Adafruit and an SD card data logging board from

Adafruit. There was also an interconnected real time clock circuit for time stamping the data log

with each entry. This same computer was also the trigger for two parachute ejection pyrotechnic

charges initiated by relays. Two extra relays were used to transmit a roger beep during normal

operation and an alarm during parachute deployment over a 2-way radio.

Figure 3.2.1: Arduino Mega 2560

Figure 3.2.2: Adafruit 10 Degree of Freedom Inertial Measurement Unit

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Figure 3.3.3: Adafruit SD card data logging board with real time clock

During testing all aspects of the code were operating correctly. The accelerometer,

gyroscope, and magnetic compass were outputting data that was in range when moving the

device along the various axes. The barometric pressure sensor and temperature sensor were

also reading correctly compared with known local ambient conditions. The barometric pressure

sensor was a mission critical input device because it is required to calculate altitude which in

turn controls the timing of the parachute ejection.

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3.3 - Recovery System Analysis

3.3.1- Recovery System

The initial design of the recovery system was chosen to be dual deployment; however,

after careful analysis and consulting with Rick Maschek, a single deployment was preferred. The

single deployment method decreased the chances of failure and complexity of the system;

therefore, increasing the success rate of the recovery system.

The recovery system must manage the speed of the vehicle in order to keep the kinetic energy of

the rocket below 75 ft-lbf. A kinetic energy greater than 75 ft-lbf could result in the structural

failure and cause the vehicle to be non-reusable. The parachute size was determined by using

following equations:

𝐾𝑖𝑛𝑒𝑡𝑖𝑐 𝐸𝑛𝑒𝑟𝑔𝑦 = 𝐾𝐸 = 1

2𝑚𝑣2

∑ 𝐹𝑧 = 𝐷𝑟𝑎𝑔 − 𝑊𝑒𝑖𝑔ℎ𝑡 = 𝑚𝑔 = 0

𝐷𝑟𝑎𝑔 = 𝑊𝑒𝑖𝑔ℎ𝑡 =1

2𝑝𝑣2𝑆𝐶𝑑

Performance of the recovery system also depends on the correct operation of the deployment

altimeters. The functionality of the recovery altimeters is tested using sample codes that mimic

similar tasks used for the recovery system. Overall verification of performance is achieved by

completing ground tests and launch test.

Parachute Diameter Calculation

Descent velocity:

𝐾𝑖𝑛𝑒𝑡𝑖𝑐 𝐸𝑛𝑒𝑟𝑔𝑦 = 𝐾𝐸 = 1

2𝑚𝑣2 , 𝑣 = 𝑑𝑒𝑠𝑐𝑒𝑛𝑡 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦

𝐺𝑖𝑣𝑒𝑛 𝐾𝐸 = 75 𝑓𝑡 ∙ 𝑙𝑏𝑓

1

2𝑚𝑣2 < 75𝑓𝑡 ∙ 𝑙𝑏𝑓

𝑆𝑜𝑙𝑣𝑖𝑛𝑔 𝑓𝑜𝑟 𝑑𝑒𝑠𝑐𝑒𝑛𝑡 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝑤𝑒 𝑔𝑒𝑡:

𝑣 < √2 𝑔 (75 𝑓𝑡. 𝑙𝑏𝑓)

𝑚

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Calculating the minimum diameter of the main parachute:

𝐴𝑠𝑠𝑢𝑚𝑒 𝑟𝑜𝑐𝑘𝑒𝑡 𝑖𝑠 𝑑𝑒𝑠𝑐𝑒𝑛𝑑𝑖𝑛𝑔 𝑎𝑡 𝑎 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝑠𝑝𝑒𝑒𝑑 (𝑠𝑡𝑒𝑎𝑑𝑦 𝑠𝑡𝑎𝑡𝑒).

𝐴𝑠𝑠𝑢𝑚𝑒 𝑡ℎ𝑒 𝑣𝑒ℎ𝑖𝑐𝑙𝑒 𝑠𝑖𝑚𝑝𝑙𝑦 𝑚𝑜𝑣𝑒𝑠 𝑑𝑜𝑤𝑛𝑤𝑎𝑟𝑑 (𝑐𝑜𝑛𝑠𝑡𝑟𝑎𝑖𝑛𝑒𝑑 𝑡𝑜 𝑧 − 𝑎𝑥𝑖𝑠).

𝐷 = 𝑑𝑟𝑎𝑔; 𝑊 = 𝑤𝑒𝑖𝑔ℎ𝑡;

∑ 𝐹𝑧 = 𝐷 − 𝑊 = 𝑚𝑔 = 0

𝑝 = 𝑎𝑖𝑟 𝑑𝑒𝑛𝑠𝑖𝑡𝑦

𝑆 = 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑎𝑟𝑎𝑐ℎ𝑢𝑡𝑒

𝐶𝑑 = 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 𝑜𝑓 𝑑𝑟𝑎𝑔

𝐷 = 𝑊 =1

2𝑝𝑣2𝑆𝐶𝑑

𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑎𝑟𝑎𝑐ℎ𝑢𝑡𝑒:

𝑆 =2𝑊

𝑝𝑣2𝐶𝑑

𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟:

𝑆 = 𝜋𝑟2

𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 𝑜𝑓 𝑡ℎ𝑒 𝑚𝑎𝑖𝑛 𝑝𝑎𝑟𝑎𝑐ℎ𝑢𝑡𝑒 = 2 ∙ √𝑆

𝜋

Using 𝑣 = √2𝑊

𝑝𝐶𝑑𝑆 we can calculate the total drift of the rocket after main parachute deployment

until landing.

𝐴𝑠𝑠𝑢𝑚𝑒 𝑡ℎ𝑒 ℎ𝑜𝑟𝑖𝑧𝑜𝑛𝑡𝑎𝑙 𝑤𝑖𝑛𝑑 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝑖𝑠 15 𝑀𝑃𝐻 (22 𝑓𝑡/𝑠𝑒𝑐).

𝑎 = 𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑎𝑙𝑡𝑖𝑡𝑢𝑑𝑒; 𝑣 = 𝑑𝑒𝑠𝑐𝑒𝑛𝑡 𝑟𝑎𝑡𝑒

𝑤ℎ = ℎ𝑜𝑟𝑖𝑧𝑜𝑛𝑡𝑎𝑙 𝑤𝑖𝑛𝑑 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 = 22𝑓𝑡/𝑠

𝐷𝑟𝑖𝑓𝑡 = 𝑎

𝑣∙ 𝑤ℎ

24

Since the maximum allowable drift is 2500 feet from launch point, the drift between apogee and

the main parachute deployment can be calculated by subtracting maximum allowable drift from

Drift value from above equation.

𝐷𝑟𝑖𝑓𝑡 = 𝑎

𝑣∙ 𝑤ℎ

𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑑𝑒𝑠𝑐𝑒𝑛𝑡 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝑓𝑟𝑜𝑚 𝑎𝑝𝑜𝑔𝑒𝑒 𝑡𝑜 𝑚𝑎𝑖𝑛 𝑑𝑒𝑝𝑙𝑜𝑦𝑚𝑒𝑛𝑡 𝑣 =𝑎 ∙ 𝑤ℎ

𝐷𝑟𝑖𝑓𝑡

Using above equations and known parameters, the following was calculated:

Input Data

ρ at 13,000 ft (3962.4 m) 0.82 kg/m^3 0.0512 lb/ft^3

ρ at 10,000 ft (3048 m) 0.9093 kg/m^3 0.0562 lb/ft^3

Chute Drag Coeff. 1.5 Dome

shaped

0.75 Flat

sheet

Max KE 101.686346 Nm 75 lb.ft

Max Drift 762 m 2500 ft

Assumed wind speed 6.7056 m/s 22 ft/s

Altitude (est. peak) 3048 m 10000 ft

Altitude (true peak) 3962.4 m 13000 ft

Avg. Thurst 996.4539 N

Impulse 9835 N-s

Mass (boost) 17.5 kg 38.58 lb

Mass (coast) 13.5 kg 29.76 lb

Diameter 0.127 m 5.00 inch

burntime 9.87 sec

Results

Area 0.012667687 m^2

qb 376.4752509

burnout v 317.8196198 m/s

p 0.250376208

burnout alt 1875.223811

qc 150.858244

coast alt 1964.350196 m

max H 3839.574007 m 12,596.87 ft

Descent V (no chute) 3.88131986 m/s 12.7391236 ft/s

Chute Surface Area 11.27065885 m^2 121.1351487 ft^2

Chute Diameter 3.78817219 m 12.41910068 ft

Main Chute Drift 670.56 m 2200 ft

25

Deployment of the Parachute

The single-stage recovery system is set to deploy at apogee (10,000 ft). The main parachute

ejects from the top of the upper body structure, just below the nose cone. This staging is

illustrated in Figure 3.3.1.

Based on the calculations, the diameter of

the parachute must be 12.4 feet in order to

have a soft landing. Each parachute cord

withstands 170 pounds of force. To

increase the strength of the cords, 2 cords

are used for each intersection. Two

ejection charges are used to ensure the

deployment of the parachute. The first

ejection charge is 4 grams of black

powder and the back-up ejection charge is

5.5 grams of black powder. The

secondary ejection charge is programed to

go off 2 seconds after the main ejection

charge.

Ejection Charges

In order to ensure separation and ejection of the parachute at the proper time, the altimeter is set

to light a two-foot low-current electric match. There are holes between the lower bulkhead and

altimeter compartment to allow the lead on each e-match through; the holes are shut with epoxy

to seal the chamber from the other chambers in the vehicle body. Improper assembly of an e-

match could result in electric shock and premature ignition of ejection charges.

Basic Ideal Gas Law is used to determine the amount of black powder needed.

𝑃𝑉 = 𝑁𝑅𝑇

𝑃 = 𝑑𝑒𝑠𝑖𝑔𝑛 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑖𝑛 𝑝𝑜𝑢𝑛𝑑𝑠 𝑝𝑒𝑟 𝑠𝑞𝑢𝑎𝑟𝑒 𝑖𝑛𝑐ℎ

𝑉 = 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑐𝑦𝑙𝑖𝑛𝑑𝑟𝑖𝑐𝑎𝑙 ℎ𝑜𝑢𝑠𝑖𝑛𝑔 𝑐𝑜𝑚𝑝𝑎𝑟𝑡𝑚𝑒𝑛𝑡

𝑁 = 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑝𝑜𝑤𝑑𝑒𝑟 𝑖𝑛 𝑝𝑜𝑢𝑛𝑑𝑠

𝑅 = 𝑢𝑛𝑖𝑣𝑒𝑟𝑠𝑎𝑙 𝑔𝑎𝑠 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 (𝑖𝑛 • 𝑙𝑏𝑓/𝑙𝑏𝑚)

𝑇 = 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑐𝑜𝑚𝑏𝑢𝑠𝑡𝑖𝑜𝑛 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑓 𝑝𝑜𝑤𝑑𝑒𝑟 𝑖𝑛 𝑅𝑎𝑛𝑘𝑖𝑛𝑒

𝑁 =𝑃𝑉

𝑅𝑇

Figure 3.3.1: Flight Sequence

26

Based on the above equations, the amount of needed black powder charge to deploy the 12 feet

parachute at apogee is calculated to be about 4 grams. Each black powder ejection charge

consists of a well of black powder contained in a plastic charge tube with the shroud of an e-

match immersed in the well.

Shock Chord

The shock cord used was a half-inch braided Kevlar Cord similar to the third cord from the left

shown in the Figure 3.3.2. The length of the cord needed was determined using a rule of thumb

from previous experience. The length was made to be 1.5 times the length of the rocket. This

made the length of the shock cord approximately 14 feet. The tensile stress applied on the shock

cord due to the load is important since keeping the parachute and body together is essential for

recovery. Kevlar stretches less upon separation and has a higher tensile strength making it a good

choice for the shock cord. The shock load on the cord was estimated to be about 492lbs. using a

method developed by a Ron Reese, the equation is below. Some reasonable approximations are

made for some of the variables. A recovery system manufacturer rated a rope with similar

material and construction at 7200 pounds. The cord is able to withstand the shock load

comfortably with strength to spare. The shock cord was tied to the body tube at all four metal

rods under the bulkhead with the metal plates seen in Figure 3.3.3. The parachute was then

secured by several knots tied to a carabiner as seen in Figure 3.3.4. The other end of the rope was

tied to a metal ring inside the nose cone. The parachute configuration looks similar to the one in

Figure 3.3.5.

Shock Load = (−𝐵+√(𝐵2−4∗𝐴∗𝐶)

4∗𝐴

A= (0.005 × Rope Stretch × Rope Length)/ Rope Load

B=-2 × A × Load

C = -Load × Fall Distance

Estimated values:

Rope stretch ≈2%

Rope Length= 14 ft.

Rope Load ≈720 lbs

Load= 35 lbs.

Fall ≈ 5 feet

27

Figure 3.3.3: Parachute Deployment

Drift Calculation

The drift of the rocket is dependent on a few factors such as launch angle, weather cocking

during vertical ascent and drift after parachute deployment due to the wind. The parachute

calculations do not take in to account weather cocking. The following formula is the basis for the

single-stage parachute drift calculations:

∆𝐴 = 𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑎𝑙𝑡𝑖𝑡𝑢𝑑𝑒 𝑑𝑢𝑟𝑖𝑛𝑔 𝑡ℎ𝑒 𝑚𝑎𝑖𝑛 𝑑𝑒𝑝𝑙𝑜𝑦𝑚𝑒𝑛𝑡

𝑣𝑚 = 𝑚𝑎𝑖𝑛 𝑑𝑒𝑠𝑐𝑒𝑛𝑡 𝑟𝑎𝑡𝑒

𝑣ℎ = ℎ𝑜𝑟𝑖𝑧𝑜𝑛𝑡𝑎𝑙 𝑤𝑖𝑛𝑑 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦

𝐷𝑟𝑖𝑓𝑡 = ∆𝐴

𝑣𝑚∙ 𝑣ℎ

The calculated result is 2200 feet which is within the requirement of 2500 feet radius.

Figure 3.3.2: Different shock cords

28

3.4 - Safety

Materials Documentation

All hazardous chemicals and materials used throughout the course of this project will be

annotated with references leading to the Material Safety Data Sheet (MSDS). Digital

copies of all MSDS documents will be stored in a three ring binder will all MSDS sheets

will be kept in the main work facility in this case the jet engine lab. All chemicals and

explosives will be labeled and properly stored. Dangerous materials will label to clearly

identify it and provide information on its properties. All labels will have the exact title of

the corresponding MSDS to help the team locate a material in the google drive file or

three ring binder.

Facilities Involved

All facilities utilized by the team will have all necessary safety equipment as required,

depending on the chemicals and materials being dealt with. The team will be made aware

of all safety equipment and be instructed on the proper use for each one. Facilities will

include a briefing sheet that will state a concise summary of all pertinent hazards and

protocols. Facilities being used will include the jet engine lab and the Friends of Amateur

Rocketry (FAR) launch site located in Mojave California.

Team Member Responsible

The team member responsible for the execution of the safety plan and overall safety of

the team will be the safety officer. The designated safety officer for the team is Josh

Kennedy, a 2nd year Aerospace Engineering undergraduate student.

Procedure for NRA/TRA Personal

All personnel involved in the launch will abide by NAR High Power Safety Code which

will be stored in the google drive and the three ring binder. All personnel will follow the

procedure as stated below regarding hazardous materials handling and rocketry

operations.

The following safety procedures come from the High Power Rocket Safety Code 2012

edition.

● NAR/TRA members will only fly rockets, handle motors, and handle fuel within

the scope of their certification and training

● Rocket materials must be lightweight such carbon fiber, wood, foam etc, and

avoid excessive use of metal.

● Only commercially made motors are allowed.

29

● Motors may not be tampered in any way.

● No heat source or open flame will be allowed within 25 feet of any motors.

● Only the fuel provided will be used, no homemade fuel will be used.

● The launcher must be 1500 feet away from any occupied building or public

highway.

● The motor will only be launched with an electrical launch system with electrical

motor igniters to be installed only at a designated preparing area.

● The launch system will have a safety interlock that is in series with the launch

switch that is not installed until the rocket is ready for launch, and will use a

launch switch that returns to the “off” position when released. The function of

onboard energetics and firing circuits will be inhibited except when the rocket is

in the launching position

● In the event of a misfire the safety interlock will be removed or disconnect the

battery then wait 60 seconds, only after 60 seconds may someone approach.

● Before launch the stability of the rocket will be checked.

● A warning system will be established.

● A check will be performed to make sure no one is in violation of the minimum

safe distance.

● When arming the rocket, no persons are to be on the launch pad except authorized

personnel.

● The rocket will be launched from a launcher that provides rigid guidance until the

rocket has attained a speed that ensures a stable flight, and that is pointed to

within 20 degrees of vertical.

● In the event of the wind exceeding 5 miles per hour a launcher of sufficient length

that permits the rocket to attain a safe velocity.

● A blast deflector will be used to deflect rocket exhaust from the ground and all

flammable material will be cleared from the launch zone.

● The motor shall not exceed 40,960N (9208 pound-second) of total impulse.

● The rocket will not weigh more than one-third of the certified average thrust of

the high power rocket motor.

● The rocket will not be launched into clouds, near airplanes, nor on trajectories

that take it directly over the heads of spectators or beyond the boundaries of the

launch site, and will not put any flammable or explosive payload in the rocket.

● The rocket will not be launched in winds in excess of 20 miles per hour.

● Safety personnel shall comply with Federal Aviation Administration airspace

regulations and make sure the rocket does not exceed any altitude restrictions.

● The rocket launch will take place outdoors in an open area where trees, power

lines, occupied buildings, and persons not involved in the launch do not present a

hazard, and that is at least as large on its smallest dimension as one-half of the

maximum altitude to which rockets are allowed to be flown at.

● The launcher will be 1500 feet away from any occupied building or any public

highway on which traffic flow exceeds 10 vehicles per hour, not including traffic

30

related to the launch. The launcher will also be no closer than the minimum safe

distance.

● The rocket shall have a parachute that allows the rocket to return undamaged in a

condition allowing it to be flown again.

● Only flame retardant or fireproof wadding will be used in the rocket.

● The rocket shall not be recovered from power lines, tall trees, or other dangerous

places, fly it under conditions where it is likely to recover in spectator areas or

outside the launch site, nor attempt to catch it as it approaches the ground.

For all important phases of this project such as construction, assembly, launch, and

recovery a safety meeting shall be convened by the safety officer. The safety officer will create a

list of hazards before each meeting as well as a safety overview sheet. These sheets will be stored

on the team’s google drive folder as well as the three ring binder.

Methods for Including Safety Precaution Statements

In order to ensure the safest possible work environment the safety officer will continually

update the MSDS sheets, review upcoming plans and procedures, consult teammates on

hazard with their associated tasks, and ensure proper safety equipment is used. If

necessary hazardous equipment will have labels designating the appropriate Personal

Protective Equipment (PPE). Hazardous equipment will also have an attached briefing

sheets detailing risks and proper operation of the equipment.

Compliance with Federal, State, and Local Rocket and Motor Laws

Federal, state, and local laws regarding rockets, and motors, will be observed by the

members of the Hybrid Rocket Pro-Team. The team’s database will consist of a three

ring binder, and a Google Drive, containing the documents regarding these laws. The

documents in this database will contain information relevant to the Cal Poly Pomona

Office of Environmental Safety, the Occupational Safety and Health Administration

(OSHA), the Division of Safety and Health (DOSH), which is also known as Cal/OSHA,

the National Association of Rocketry (NAR), and the National Fire Protection

Association (NFPA). In the database, there will also be digital copies of NFPA 1127,

NAR High Power Safety Code, Federal Aviation Regulations (14 CFR, Subchapter F,

Part 101, Subpart C), and the Code of Federal Regulation 27 (Part 55: Commerce in

Explosives). The Hybrid Rocket Pro-Team will strive to meet the requirements set by

these laws. Every member of the team will become familiar with these laws, and

demonstrate knowledge of them before the production, and testing, of the Hybrid Rocket

begins.

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Possession of Rocket Motors

The task of purchasing, and obtaining, the rocket motors will be the responsibility of the

Hybrid Rocket Pro-Team’s certified rocket mentors. The team’s certified rocket mentors

include Matthew Ross (NAR Level 2), and Francisco Davila (NAR Level 1). All of the

team’s rocket motors, and propellants, will be obtained from licensed local suppliers.

Aside from purchasing, and obtaining, the rocket motors, the team’s certified rocket

mentors will also be responsible for storing the rocket motors at their residence. The

rocket motors will be stored in their original shipping containers, and they will be

transported, along with the fuel, within the trunk of a vehicle to the launch sites for

safety.

Student Compliance of Safety Regulations

The members of the Hybrid Rocket Pro-Team will be taught the safety guidelines, and

practices, necessary to ensure the safety, and well-being, of everyone involved in the

construction, and testing, of the rocket. If an accident ever occurs, the safety officer will

instruct the team members what to do to resolve the problem, and avoid further accidents.

The safety acknowledgement form contains the safety regulations stated below, and it has

been read and signed by every team member. This form which was signed by each team

member to launch at F.A.R can be found in Appendix B in Figure 9.1.

● Range safety inspections will be performed on each rocket before flight

● Every team member will accept the determination of the safety inspection

● If team members fail to accept determination they may be removed from the program

● The Rocket Safety Officer (RSO) will determine every issue regarding rocket safety

● The Rocket Safety Officer (RSO) can cancel any rocket launch for safety reasons

● Team members who fail to comply with safety guidelines will not be allowed to

participate in the launching of the rocket

Launch Day Safety:

Given the dangers of the rocket the following safety procedures were strictly observed before

both launch attempts:

· Top to bottom structural checks of the rocket

· Mounting and unmounting the rocket engine and fueling system

· Configuration of launch rail and mounting to rocket before launch

· Sufficient water to avoid dehydration at launch site

· Preflight checks of all launch equipment

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· Made sure everyone was in protective bunkers prior to launch

· Proper fueling and set up from a safe distance with the oversight of FAR personnel

· Proper countdown and warnings

· Proper defueling of rocket after aborted launch attempt

· Waited till rocket landed to leave bunkers

· Safe retrieval and removal of rocket motor

33

4.0 – Construction: Design

The entire project was first brainstormed on paper and on a white board but as the choices

were becoming finalized, drawings using Solid Works were being created. The Solid Works

models allow for a better visualization of what needs to be constructed and the dimensions of

each object. This also allows for everyone on the team to see whether or not the parts will fit

together and exactly what size something needs to be made in order for the rocket to be

constructed properly. Below are some of the designs throughout the stage of the rocket which

were made and changed several times as the project progressed in the build stage. The solid

motor portion of the rocket was created so that it could be understood what dimensions the frame

must be so that the motor can easily slide in and out so that it can be reusable as shown in Figure

4.0.1

Figure 4.0.1: Motor Casing

The entire outer section of the body tube needed to be designed around the motor casing

and the frame so that the assembly can take place in the simulation. Once everything fits

perfectly, that allows the team to go ahead and order the parts needed such as the cardboard tube

from Public Missiles Ltd. which slides into the carbon fiber tube. The tube can be seen below in

Figure 4.0.2. The entire length of the solid and nitrous motor is 54.5 inches when assembled

together. They have a diameter of 4 inches and this is why the inner diameter of the bulkheads

must be 4 inches while their outer diameter must be 6 inches.

34

Figure 4.0.2: Initial Rocket Body Tube with Nose Cone

The bulkheads are the primary component that keeps everything together in the structural

aspect of the rocket. They are 6 inch in diameter and the inner diameters are 4 inches which

allows the hybrid motor to slide in to the inner portion and the outer portion fits snug within the

6 inch inner diameter of the cardboard tube. Holes were drawn in the bulkhead which will allow

the steel rods to fit through and go throughout the body of the rocket giving it a strong and sturdy

structure. These designs can be seen below in Figures 4.0.3 and Figure 4.0.4.

Figure 4.0.3: Motor Support Bulkhead (Aluminum)

35

Figure 4.0.4: Rocket Frame with Bulkheads

The fin design was a direct scaled down version of the German V-2 rocket fin. Initially

controlled fins were planned but with time constraints it was not achievable so the flaps were not

added to the final product although there was room left for the addition if everyone decided to go

forth with the plan. The fins were designed by looking off of blueprints of the V-2 fins found

online and scaling it down so that it would be sufficient for the Hybrid rocket. This design can be

seen below in Figure 4.0.5.

Figure 4.0.5: V-2 Fin Design on Smaller Scale for Hybrid Rocket

36

4.1 - Construction-Manufacture/Materials

Bulkheads:

A number of plywood bulkheads were utilized to center the motor inside the body tube of

the rocket. Bulkhead dimensions were created using SolidWorks shown in figure 4.1.1 and

printed in actual size to allow for a simpler method to correctly achieve the right dimensions to

be cut out onto plywood. Once they were cut, the bulkheads were sanded down as needed in

order to be inserted into the rocket body tube with ease. Even though the diameter of the motor

was used to cut the bulkheads, the bulkheads were sanded to fit better around the motor. This

allowed the motor to be inserted through the bulkheads with less effort, and to still be held in the

center of the rocket body tube.

Figure 4.1.1: Bulkhead Dimensions created with SolidWorks

37

Carbon Fiber:

Two cardboard cylinder tubes were used as mandrels for the rocket body tube, and sheets

of carbon fiber were wrapped around these tubes. Epoxy and hardener were used to bind the

carbon fiber to the tubes. The tubes were too large to be placed in an oven to cure the carbon

fiber, so they were dried at room temperature. Figure 4.1.2 below shows the carbon fiber

wrapped over the cardboard tube.

Figure 4.1.2: Tube wrapped with carbon fiber and left to dry

Steel Rods for Support:

Four steel rods were used to support, and space out, the bulkheads. In order to insert the

steel rods, each bulkhead had four holes drilled into it. These rods were held in place by a

washer, and a nut, on either side of the bulkhead. The most difficult part of inserting the steel

rods was to ensure that the holes drilled into each bulkhead were aligned correctly. At first, the

holes were not aligned, and this caused the steel rods to bend when they were inserted. This

problem was solved by using one of the bulkheads as a template, so that the drilled holes could

be aligned more easily as seen below in figure 4.1.3. The steel rods can be seen in figure 4.1.4

38

which keeps the whole motor intact and provides great structural support for the rocket. The

completed structure can simply slide into the carbon fiber tubes.

Figure 4.1.3: Bulkhead used as template for other bulkheads

Figure 4.1.4: Steel rod structure

Cardboard Cylinder Tubes:

Two cardboard cylinder tubes were used to make the rocket body tube. At first, the team

planned to use a mandrel to make the rocket body tube exclusively out of carbon fiber. However,

39

a mandrel with the diameter needed to house the rocket motor, and all the other components of

the rocket, could not be acquired. As a result, two cardboard cylinders with the desired diameter

were used as mandrels. Each cylinder was 4 feet long, and had a diameter of 6 inches. The

diameter of the cylinder is equal to the outer diameter of the bulkheads. All of the bulkheads

were sanded to fit slightly loose inside the cardboard tubes, so that they could be inserted easily

along with the motor inside the rocket body tube. Since the tubes were used as mandrels, they

became part of the rocket body tube because the carbon fiber wrapped around them could not be

removed. While building the rocket body tube, one of the cylinders was damaged, and a piece at

one end of it was missing. This problem was solved after the carbon fiber was placed over the

cardboard tubes because the carbon fiber hardened, and covered the damaged part of the tube.

Two tubes were used and each one was 6 inches in diameter and 4 feet long and can be seen in

Figure 4.1.5 below.

Figure 4.1.5: Cardboard tube

Fins:

The fins were constructed from a core of wood then laminated with two sheets of carbon fiber on

either side. This served to strengthen the fins while adding low drag. A final layer of carbon fiber

was used to attach the fins to the lower body tube. Several layers of epoxy were applied to

harden and form a smooth surface for airflow ensuring maximum aerodynamic performance. Fin

40

manufacturing can be seen below which includes having the wooden pieces and then having the

carbon fiber cut outs which will be applied on them for reinforcement.

Figure 4.1.6: Applying epoxy to carbon fiber in order to adhere to plywood fins.

4.2 - Construction-Integrate controls/batteries

The main portion of the electronics is located above the liquid nitrous oxide tank. In this

section we focus on the electronics used for parachute deployment. These electronics consist of

an altimeter which is connected to a pair of electronic matches to set off the black powder

charges for the deployment of the parachute as shown in figure 4.2.1.

Figure 4.2.1: Electronics

41

Above the charges shown in the diagram, a nomex blanket is used to cover the parachute

from any fire damage caused by charges explosions. Towards the center of gravity of the rocket

shown in orange, there were two set of mini cameras in figure 4.2.2, one facing up towards the

nose, and one facing down towards the fins of the rocket. These were used to record the launch,

parachute deployment, and landing.

Figure 4.2.2: Onboard camera

4.3 - Construction-Parachute/Shock Charge

4.3.1- Parachute Production

For the 12 feet diameter parachute with a 1 foot spill hole, Brand RIP Stop Nylon was used for

the material. The same material was used and tested by NASA Student Launch for the

competition and it was proven to be durable and strong. After cutting the fabric into proper

pieces, each section was attached to the other section by sewing the endings twice to ensure the

parachute would not rip apart due to applied forces. The recommended stitching length is 5% to

10% of the basic parachute diameter. After completely attaching all pieces, the parachute cords

were sewed on each endpoint of parachute. The technique used to attach the cords to the

parachute is as follows: two pieces of nylon were cut in a square shape. The sides of each square

were about 1 foot. The cord was placed in between two squares and was sewed in zig-zag format

then the nylon squares were attached to the endpoints of the parachute by sewing. Figure 4.3.1

shows how the parachute was made and Figure 4.2.1 shows how it looked when done.

42

Figure 4.1.1: Creating the chute

Figure 4.3.2: Parachute at F.A.R. after the launch test

43

4.3.2- Parachute Ejection Charges

The materials needed for the parachute deployment were: shot gun shells figure 4.3.1, black

powder figure 4.3.2, and electronic matches figure 4.3.3. First a hole was drilled on the side,

towards the bottom of the shot gun shell where the electronic match was placed for ignition.

Figure 4.3.2.1: Shot gun shells Figure 4.3.2.2: Black Powder

The plastic tube was filled with black powder. In this case the rocket was quite large with

a diameter of six inches, because our University never made this size of rocket before, two shot

gun shell were used instead of one for redundancy. One filled with 2.8 grams, and the second

shell with 2.6 grams of black powder. These charges were connected to the altimeter of the

rocket, so when it reached apogee, the first charge will go off, and two seconds later the second

charge will be activated to make sure all the parachute was out of the rocket.

44

Figure 4.3.2.3: Electronic matches

4.4 - Construction-Assembly

Assembly - Motor with bulkheads and steel rods:

To assemble, the rocket bulkheads were used in order to keep the motor in place, and

steel rods were utilized in order to distribute the load on the bulkheads (Figure 4.4.1). Each

bulkhead was positioned at a certain point on the steel rods, so that the motor could be held in

place by the bulkheads at different points. Steel plates were also added in between the washers

and the bulkhead at the end of the motor (Figure 4.4.2). This was done to ensure that the

bulkhead had enough support to keep the rocket from going right through the wood.

45

Figure 4.4.1: Motor assembled with bulkheads and rods

Figure 4.4.2: Steel plates for reinforcement

46

Assembly - Carbon fiber fins:

The fins of the rocket were cut out of plywood, and the dimensions of the fins were

designed using SolidWorks. A two dimensional sketch was created, and printed out to be used as

a template. After the template was used to cut out the fins, the fins were covered in carbon fiber

and then aligned on the rocket after it dried (Figure 4.4.3). A plastic cover was then placed over

the fins covered in carbon fiber so that air bubbles would not form. Even though the plastic cover

remained on the fins until the carbon fiber dried, air bubbles still appeared on some of the fins.

This problem was solved by sanding the fins to remove the air bubbles, and then applying

another coat of epoxy. The fins were also sanded to remove excess carbon fiber on their edges,

the sanded fins can be seen in Figure 4.4.4.

Figure 4.4.3: Fin aligned on tube

47

Figure 4.4.4: Sanded fins

Assembly - motor and body tube:

After the body tube was finished and the motor was encased in the structure the two were

put together. Sliding the bulkhead/motor into the body tube was not too difficult; it was just a

case of making sure the bulkheads were aligned properly with the steel rods in order to slide

easily into the body tube (Figure 4.4.5). These bulkheads were all hand cut so they weren’t

perfect in size as it would have been if they were laser cut but the team decided to go ahead and

manually cut them to get some good experience. The demanding part of this assembly was

getting screws to attach the rocket body tube to the bulkheads. Unable to see where the

bulkheads aligned with the body tube it became clear a method for deciding where to drill was

needed. This led to the idea of measuring the bulkhead distances prior to sliding the

motor/bulkhead into the body tube. In order to assure the holes drilled in the body tube were

aligned to have the screws drill into the bulkheads, a regular piece of paper was utilized. By

48

simply wrapping the piece of paper around the body tube and taping it so its ends would align a

method for creating aligned holes for the bulkheads was achieved (Figure 4.4.6).

Figure 4.4.5: Half of the motor after being slid onto the body tube of the rocket

Figure 4.4.6: Process of drilling holes onto the body tube of the rocket in order to screw

the body tube onto the bulkheads

49

5.0 - Testing

5.1- Electronics Testing

The parachute deployment and data logging system used an Arduino with barometric

pressure sensor, accelerometer, magnetic compass, and gyroscope sensors, an SD card, and

electronic relays. The Arduino was programmed to use barometric pressure to calculate

approximate altitude. When a drop in altitude was detected, the Arduino would turn on one relay

and then another a few seconds later. These relays were connected to electronic matches in two

different ejection charges.

This system was tested by being assembled inside a small box with lightbulbs installed

instead of electronic matches/ ejection charges. The box was tied to a string and lowered from

the top of a flight of stairs roughly 8 feet. The system was confirmed working because the lights

would illuminate when the box was descending. This was also confirmed by the data log on the

SD card installed in the Arduino.

5.2 – Ground Equipment Testing

Rick Maschek was present during the ground equipment testing because he was

the only one who owned all of the equipment which costs upwards of over $1,000. The

team needed rick to come down to Cal Poly Pomona and go over the procedure so

everything was brought down except for the oxygen and nitrous tanks. This was later

found to be a problem because on launch day the tanks were the reason the team were

having failed attempts since the solenoids were not functioning correctly.

The ground equipment consisted of the following:

• Launch Stem; a coaxial tube with adjustable mount that fits to the launch rod or rail and

has male 4AN fittings for the gaseous oxygen and nitrous oxide lines.

• Gaseous oxygen (GOX) line; a 10-foot stainless steel-braided hose with red female

4AN fittings.

• Nitrous oxide line; a 10-foot stainless steel-braided hose with blue female 4AN fittings.

• Nitrous oxide Solenoid Assembly; consisting of fill solenoid, dump solenoid, blue male

4AN fitting, and CGA 326 tank fittings for industrial nitrous oxide tanks. CGA 660 tank

valve fittings for hot rod nitrous oxide tanks are an available option.

• GOX Assembly; consisting of an oxygen regulator, CGA 540 tank fitting, solenoid

valve, check valve and a red female 4AN fitting.

• Ignition module; 7500VDC output generates an arc across the ignition wire for ignition

of the fuel grain. Fuse-protected, comes with spare fuses.

50

• Launch Controller; equipped with Safe & Arm key switch, LED power indicator, three-

position rotary switch for Fill/Dump/Fire functions, and momentary toggle actuator

switch. Reverse polarity protected.

• Satellite Control Box with color-coded sockets; two outlets for the nitrous oxide fill and

dump solenoids, plus outlets for the GOX solenoid and ignition module.

• 100 foot 3-prong extension cord for connecting the launch controller and satellite

control box.

• One roll of 24 gauge 2-conductor ignitor wire.

The Ground Support Equipment performs three functions, each of which is controlled remotely

via the launch controller:

• filling of the flight oxidizer tank

• dumping of the flight oxidizer tank in the event of an aborted launch

• non-pyrotechnic ignition of the motor

The equipment testing follows as below:

1. Split and strip insulation from one end of a 4 inch piece of ignition wire. Twist the

stripped wire ends to avoid fraying. Cut

the other end straight across – make this a clean cut with sharp scissors or cutters.

2. Attach the stripped ends to the alligator clips of the ignition module, and let the cut end

dangle where it is

visible. Make sure that the alligator clamps are not shorted together and that the wire or the clips

are not in contact with

you or anything else.

3. Fully open the oxygen tank valve and adjust the regulator to between 80 and 100 psi. If

you hear any leakage, turn the

oxygen off and make sure the fittings are tightened.

4. Fully open the nitrous oxide tank valve and verify that there are no leaks. Remember that

nitrous oxide tanks without

siphon tubes must be mounted upside down to allow liquid nitrous oxide to flow into the oxidizer

tank.

5. Set launch controller switches as follows: Safe/Arm key switch on Safe, rotary switch on

Fill (top) position, and activate

switch Of.

6. Attach the battery cables to a 12V DC source capable of supplying at least 10 amps.

Either a car battery or a gel-cell

battery will be adequate. Please note that the launch controller circuitry is reverse-polarity

protected and the clips may be

attached either way to the power source.

7. Turn the Safe/Arm key switch to the Armed position. The indicator light should now be

on.

8. Make sure that the launch pad area is clear prior to checking the oxidizer fill system.

Briefly push the activate toggle switch

51

up and nitrous oxide should be released from the launch stem. As nitrous oxide escapes from the

fill tube, the vaporizing

liquid plume should be easily visible. Release the toggle switch.

9. Move the rotary switch to the dump position, and activate the toggle switch. The dump

solenoid clicks as it opens - listen

for the sound (no nitrous oxide will be released). Release the toggle switch.

10. Double check that the ignition wires are clear of any part of the GSE or other materials,

and especially away from you!

Move the rotary switch to the fire position, and activate the toggle switch. A steady high-voltage

arc should be seen at the

end of the ignition wire, and oxygen should be heard escaping from the start oxidizer tube. Do

not place any part of your

body near the ignition circuitry while this test is in progress – serious electric shock could result.

5.3- Parachute Testing

Parachute Cords:

A drop test was performed to ensure the strength and durability of the cords. A 1.5 foot Braided

Mason Line 100% Filament Nylon Cord was attached to a 20 lb weight and was dropped to test

its strength. Based on the test results the strength of the cord was estimated to be 165-172 lbs.

For each endpoint, two cords were used instead of one. Since the parachute consists of 6

endpoints, the force applied by the weight of the rocket at the moment of deployment gets

distributed between the six cords. Doubling the cords decreases the distributed force by a factor

of 2.

Figure 5.3.2: Drop test to determine the

strength of the parachute cord

52

Ejection Charge:

An ejection charge test was performed to confirm the calculated amount of black powder

was enough and if the nose cone and parachute would deploy properly. This test was done by

securing the upper body tube and enabling the ejection charges by a long wire from a safe

distance. The calculated amount of black powder and the test results were in agreement. A

secondary ejection charge with a higher amount of black powder was also placed next to the

main ejection charge with a 2 second delay to ensure the parachute would be deployed.

Figure 5.3.3: Ejection Charge Test

53

6.0 - Procedure

6.1 Launch Pad

At FAR, there were many different types of launch pads to choose from. We

chose the one most adequate for our rocket.

A jack was used to lower the launch rail to a horizontal position.

The launch stem assembly was placed on the launch rail with C-clamps for the

connection of the nitrous oxide lines.

Figure 6.1.1: Rocket on one of the many launch rails at F.A.R

54

6.2 Ground Support Equipment

The Nitrous Oxide tank had to be taken out in a cooler filled with ice due to the

hot weather (over 108 F).

Figure 6.2.1: Team preparing rocket and keeping the nitrous tank cool in the ice cooler

The nitrous oxide solenoid assembly was mounted onto the nitrous oxide tank.

The tank fitting which connects the tank valve to the solenoids was to be

moderately tight. The nitrous oxide line was attached afterwards.

The GOX assembly was mounted on the oxygen tank and attached the oxygen

line (with red AN fittings) to the regulator. Due to recommendations, the oxygen

bottle was laid on its side to prevent damage to the valve or regulator in case it

was knocked over by accident.

55

Figure 6.2.2: NOS and GOX Solenoid Assembly along with the Launch controller box to

the left

Launch stem assembly was used which was placed on the launch rail in order to

connect the nitrous oxide line (blue fitting) to the nitrous oxide fitting on the

launch stem (blue fitting). We proceeded to connect the oxygen line (red fitting)

to the oxygen fitting on the launch stem (red fitting).

The oxygen tank and the nitrous oxide tank were placed about six to eight feet

from the launch stand, with no kinks or tight bends in the hoses as seen being

worked on in Figure 6.2.1.

Connection of the satellite control box to the launcher. The box had two duplex

outlets. The duplex outlet with brown and white outlets was for the nitrous oxide

solenoids. The black outlet was for the ignition module, and the green outlet was

for the oxygen solenoid. Plug the nitrous oxide dump solenoid (white plug) into

the white nitrous dump outlet. The team plugged the nitrous fill solenoid (brown

plug) into the brown nitrous fill outlet. Then, we plugged the oxygen solenoid

(green three-prong plug) into the green ignition oxygen outlet. Finally the team

was able to plug the ignition module (black three-prong plug) into the black

ignition spark outlet.

The satellite control box was plugged onto an extension cord that had the correct

voltage to prevent it from igniting again, and run the extension cord to the launch

control area.

The launch controller was connected to a 12 volt battery.

The ground setup equipment was tested one final time before proceeding.

56

Figure 6.2.3 Assembly of Ground Support

6.3 Flight Motor Assembly

Igniter wire of about 24” long was cut and separated the wires at one end and

stripped about 1⁄2” of insulation from each. Then it was twisted so that each wire

would prevent from fraying.

Igniter wire was taped to the launch stem leaving a little extra at the top so the top

end could be trimmed. The top end of the wire was about 1” from the top of the

nitrous oxide fill tube.

57

o The wire was trimmed by making a clean, straight cut as we did for GSE

testing. It was double checked that the cut end was positioned about 1”

from the top of the fill tube and bent the cut end outward slightly.

Figure 6.3.1: Igniter wire being taped onto the Launch Stem

The 10 ft. rocket was carried out in the scorching hot weather by one of the team

mates. WD-40 was used to clean and lubricate the launch rail.

The rocket was then slid down the launch rail.

58

Figure 6.3.2: Rocket being slid down the rail with the launch buttons

Carefully the launch stem was inserted up through the fuel grain. When the fill

tube (the center coaxial tube) passed through the Kline valve O-ring, the team was

able to feel it sit against the injector body indicating correct feeding.

The tie-straps were inserted through the slots in the fuel grain, and looped one

around each protruding bolt on either side of the stop collar on the drop stem. The

tie-straps were joined at the ends and cinched up tightly to pull the drop stem

firmly towards the motor.

Once again, a jack was used to now lift the launch rail into a vertical desired

position as show in action in Figure 6.3.1.

Finally Rick Maschek opened the nitrous oxide and oxygen tank valves and were

ready for launch with the safety officer watching out and making sure everyone

was a safe distance away!

59

Figure 6.3.3: Ground equipment setup and attached to the rocket motor

The nitrous tank can be seen laying in an ice cooler with ice to keep it at a cold temperature in

the picture above. The rest of the ground equipment can be seen except for the oxygen tank

which was kept on the other side away from the nitrous.

Figure 6.3.1 Jack lifting of rocket to desired horizontal positioning

60

7.0 - Post Launch-Summary

The hybrid rocket successfully launched after two unsuccessful attempts on August 15,

2015. Although there were various flaws in our overall launch, the rocket, however, did meet

many of the team’s goals. For example, although the parachute detached from the rocket on its

way down, it did successfully deploy as programmed. In addition, the rocket did not meet the

10,000 foot altitude requirement, but it did reach an altitude of between 2,500-3,000 feet.

Overall, this project was a huge feat for Cal Poly Pomona as it was the first hybrid rocket ever

launched by any students at Cal Poly Pomona and will hopefully set a strong precedent for future

rocket project teams to build from.

61

7.1 - Post-launch-Results

Shortly after the launch the rocket started tilting due to its stability and weather cocking.

The center of pressure and center of gravity of the rocket were too close; therefore, as the rocket

burned its fuel, the center of mass started to shift and the rocket became unstable. Weather

cocking also affected the direction of the flight since the horizontal wind velocity rotated the

vehicle to where it had a new flight direction into the wind. These two factors combined caused

the rocket to tilt until it started descending. The altimeter sent a signal notifying the change in

altitude is no longer positive which triggered the ejection charges to deploy the parachute. At this

point the rocket had a downward coast velocity. The parachute deployed; however, due to the

rocket’s high velocity, the parachute cords did not withstand the exerted forces and they snapped.

All 12 cords were disconnected as shown in the Figure 7.1.0. The chosen cords were designed to

be used at apogee when the velocity of the rocket was at its minimum. Each cord was capable of

withstanding about 170 lbs. The opening shock, also known as the jerk, was much greater than

expected since the rocket became unstable and did not reach a near-zero velocity at apogee. This

exerted force was greater than the breaking point of Braided Mason Line Cord and caused the

parachute to fail.

Figure 7.1.0: Shock cord tied to carabiner

Aside from mechanical problems during the fueling and launch, the rocket flew correctly

and the electronics appeared to work because at least one parachute ejection charge explosion

and smoke was seen. This was followed by the parachute deploying. Unfortunately, the

parachute strings snapped and it was disconnected from the rest of the rocket; thus, causing the

rocket to land hard.

The flight computer was still functioning when the rocket was recovered and was

switched off so that the SD card could be removed and data recovered. The data file was intact

when loaded into the computer, however there were numerous issues.

62

Data Issues:

1) Barometric pressure and altitude values hardly changed throughout entire flight time.

2) No data point was marked for parachute deployment command. A program was

specifically written for a part of the code which would insert the altitude at ejection event into

one cell in an empty column of the data file. This data point was missing. This leads to two

conclusions:

a) The computer worked correctly and triggered the parachute when the rocket

started falling and somehow the data file was incomplete.

b) The computer was not working correctly and the ejection was triggered by an

electrical failure mid-flight.

3) Accelerometer, gyroscope, and magnetic compass data looks correct but seems like the

time is incorrect. Our data graphs were compared to other rocket flights and it looks similar. The

main issue here is that the entire flight was only around 20 seconds long, yet the data log shows

the changes in the datalog indicating extreme motion over much longer periods of times

(minutes).

In conclusion, the data is not useful for anything with a degree of certainty. One of the

biggest problems realized is the data sampling rate. The code sampled data once every 3 seconds.

It should have been sampled at an incredibly higher rate. At a higher rate it would be possible to

detect false readings from true readings. Unfortunately the data that we were left with isn't

specific and is very inaccurate. The temperature appears to fall at random when it should be

constant or increasing. The pressure and altitude seem to be changing when the rocket would

have been standing still. The inertial measurement events last too long before returning to a

steady state value. The only thing known for sure about the data collection is that it is impossible

to interpret. It is very possible the crash at the end of the flight caused a major computer failure

and the data log was affected somehow. Based on estimates from watching previous people at

F.A.R launch their rocket, it is believed the Hybrid Rocket reached a max altitude between

2,500 ft. to 3,000 ft. It was also found that the drift distance of the rocket was about 880 ft. from

the launch stand which meant the rocket tilted quite a bit on its way up which is one reason why

the max altitude is not as high as planned.

63

Figure 7.1.1: Electronics bay before flight (left) and after flight (right). Major damage to

the rocket frame surrounding the electronics can be seen.

Even without data we can be fairly certain the parachute ejection system did work

correctly because of one loud POP (00:12 in video) followed by a second quieter POP (00:13)

which could be heard less than one second later on the video. Smoke can also be seen after each

POP. The computer was programmed to fire one charge and then another approximately 800

milliseconds later. Because the video timing lines up exactly with the computer code, as

excerpted below, we believe the ejection control system worked correctly.

if((difference<-x) && (alt>control) && ecc==0)//where x is the minimum limit for the negative

change in altitude. The combo of these difference<x and alt>control prevent premature deploy.

{

float ejection_event = alt; //altitude at which the ejection charges fired

logfile.print(", ");

logfile.print(ejection_event);

digitalWrite(4,HIGH); //turn on relay connected to pin 4 (relay 1)

delay(800);

digitalWrite(5,HIGH); //turn on relay connected to pin 5 (relay 2)

delay(5000);

Code excerpt highlighted in yellow are the commands that close the relays energizing the

explosive charges for the parachute ejection. The line "delay(800)" is an 800 millisecond delay

between firing the first and second charges. The second charge is meant as a redundancy in the

event the first charge is a dud.

64

Data:

Figure 7.1.2: Accelerometer data

Figure 7.1.3: Magnetic compass data

-15

-10

-5

0

5

10

15

20

0 500000 1000000 1500000 2000000 2500000

m/s

^2

ms

Accleration

accelx (m/s^2)

accely (m/s^2)

accelz (m/s^2)

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

80

0 500000 1000000 1500000 2000000 2500000

uT

millliseconds

Magnetometer

magx (uT)

magy (uT)

magz (uT)

65

Figure 7.1.4: Gyroscope Data

Figure 7.1.5: Barometric pressure sensor data

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

0 500000 1000000 1500000 2000000 2500000

rad

/s

ms

Gyroscope

gyrox (rad/s)

gyroy (rad/s)

gyroz (rad/s)

940

940.5

941

941.5

942

942.5

0 500000 1000000 1500000 2000000 2500000

Pre

ss

ure

(h

pa

)

milliseconds

pressure (hpa)

pressure (hpa)

66

Figure 7.1.6: Altimeter data

Figure 7.1.7: Thermometer data

608610612614616618620622624626628630

0 500000 1000000 1500000 2000000 2500000

alt

itu

de

(m

)

milliseconds

altitude (m)

altitude (m)

45.5

46

46.5

47

47.5

48

48.5

49

49.5

0 500000 1000000 1500000 2000000 2500000

tem

pe

ratu

re (

C)

milliseconds

temp (C)

temp (C)

67

Figure 7.1.8: Puff of smoke (in purple circle) after first audible POP frame capture from

00:12 in video

68

Figure 7.1.9: Video frame capture

From the figure above it can be seen that at 00:14 seconds of flight it is showing initial

smoke puff (purple), cone (yellow), and light wisp of smoke after second audible POP. The

rocket body can be seen just under the red circle as a black spot.

69

7.2 - Conclusions

June 20th

was the first attempt of Cal Poly Pomona’s hybrid team to launch their first ever

Hybrid Rocket. It was difficult to ascertain the source of the failure; however, a voltage from the

shoddy extensions is the most likely suspect. There were simply too many problems with the

ground equipment and setting up the wiring out in the heat which took a long time. During this

time the nitrous oxide tank was warming up since all the ice had melted away and it was pretty

much useless to use the nitrous. Time was of great issue and when the team was ready to retry

again, the airspace was no longer cleared for us since it was 5:00PM and our time slot was over

to launch anything up in the air. There was no choice, but to come back another day and keep

trying.

The team practiced the ground equipment setup several times while they waited a few

weeks to return and attempt the launch again. This time the team knew what problems could rise

and how to overcome them. Once all the equipment was setup the launch controller was set to

“fill” in which the nitrous could be heard filling into the rockets oxidizer tank. However, when

the fire button was pressed, nothing happened and the rocket needed to be taken down once more

to figure out what went wrong. It was apparent that the Launch Stem, pictured below in Figure

7.2.1, was not inserted all the way into the inlet fitting of the oxidizer tank so all of the nitrous

was being leaked out into the atmosphere which was not visible because of the extreme heat on

launch day.

Figure 7.2.1: Launch stem inserted in motor

70

A small piece of tape used to keep the igniter wire on the launch stem was blocking the

path of the end of the stem to insert itself correctly. Once this problem was fixed, the second

attempt on this day was set to go and this time the nitrous was being filled correctly but the

oxygen tank was not dumping oxygen for the igniter to burn enough. This seemed to be the same

problem that occurred on the first launch attempt a few weeks back. This time it was figured that

a voltage drop was occurring once we lowered the rocket down and did a quick ground

equipment check with the Launch stem disconnected. It was found that the extension cord was

encountering too much resistance and had been exposed to too much extensive heat so the

oxygen tank solenoid was not firing due to voltage not being available after the drop. Figure

7.2.2 shows the rocket being taken down one last time.

Figure 7.2.2: Last adjustments on the rocket

71

Figure 7.2.3: Oxygen tank connected to the launch stem

A much bigger extension cord, which was capable of carrying a bigger load was grabbed

quickly from the F.A.R bunker and it replaced the old one. The entire launch procedure was then

repeated and the nitrous was filled for a total of 3 minutes and 30 seconds which is the required

time to fill the tank and the fire button was then pushed. The igniter burned up and a lot of fire

was seen but the rocket stayed on the stand for about 7 seconds before exhaust flames started to

be visible. Even once the exhaust flames were visible, the rocket did not leave the stand for

another 3 seconds and then it finally took off.

72

Figure 7.2.4: Ignition just before take off

73

Figure 7.2.5: Take-off

The rocket was ripped off of the launch buttons because the rail buttons were found to be intact

on the rail after the launch. The rocket started to tilt about a second into flight and then the

horizontal component became greater as the rocket climbed higher. The ejection charges were

fired through the Arduino program, however, the parachute was ripped off due to the momentum

of the rocket in the horizontal direction so the rocket crash landed. The parachute ejection can be

seen below in figure 7.2.6. If the rocket was to deploy soon after apogee with less momentum,

the parachute would have been able to slowly descend the rocket to a soft landing.

74

Figure 7.2.6: Parachute ejection

The rocket crash landed and the data retrieved came out to be extremely impossible to

interpret so there is no exact knowledge of the flight characteristics. It is estimated the rocket

went to a max altitude of 2,500 ft. to 3,000 ft. based off of previous launches from other people

at F.A.R, and the drift distance was roughly 880 ft. It came to the conclusion that most of the

rockets trajectory went into its horizontal component due to the center of pressure and center of

gravity of the rocket being too close and the center of mass shifting. One major component that

affected the rocket in not reaching its projected max altitude of above 10,000 ft was that the

oxidizer tank was not fully filled with the nitrous. This conclusion is due to the fact that there

was never a correct fit with the launch stem into the oxidizer tank so a lot of the nitrous during

the 3 minutes and 30 seconds of fueling was just being leaked outside the rocket instead of going

in. One proof for that is that once the solid motor was retrieved, it was visible that a lot of it was

still unburned since there wasn’t enough nitrous available to produce the combustion with the

rest of the solid fuel. The recovered rocket is shown below in figure 7.2.7.

75

Figure 7.2.7: Recovered rocket

Although the rocket did not reach the maximum altitude set in the mission criteria and the

rocket didn’t have a successful landing, the experience was one that the Hybrid team will

remember for their entire lives. This was the first rocket everyone on this team ever worked on,

and given the amount of time to work on this rocket in between school work was a challenge but

everyone worked hard and kept a positive attitude despite several mishaps that occurred

throughout the stages of this build and launch. Many lessons were learned during this project

including time management and organization, best of all everyone received the self confidence in

knowing that they can build rockets now with the knowledge they gained. Mistakes happen and

disasters occur, but learning from each event is important so next time those problems can be

avoided. It was a great experience to finally see the rocket leave the rail because it seemed very

unlikely it was going to launch. The entire motor and oxidizer tank are completely intact due to

the strong structure built to protect them and are still in perfect condition to reuse for another

attempt which some of the team members are planning on doing in the 2015-2016 year.

76

Figure 7.2.8: Damage to rocket

77

7.2.9: Burned fins from exhaust flame

78

Figure 7.2.10: Motor still in perfect condition after crash

79

Figure 7.2.11: Bottom of rocket after launch

Figure 7.2.12: Bottom of nozzle

80

Figure 7.2.13: Hybrid Rocket Team Post Launch Picture

81

8.0 - Recommendations

Since this was the first time a Hybrid Rocket was built at Cal Poly Pomona, there weren’t

many examples to go by during the design phase and construction phase. Therefore, there were

many problems such as how to fit such a huge motor and making sure the weight is kept at the

minimum along with the C.G and C.P not being thrown off too much. The other big problems

that really hurt the hybrid team were that there simply are way too many things required in the

ground equipment for a hybrid rocket. The ground equipment is extremely expensive and Rick

Maschek was lucky enough to borrow it from someone. There are many components and

connections that need to be made and this means that there are just more things that can go

wrong. For this reason, the hybrid team was not able to do more than one equipment check

before launch day since Rick had to be present with everything in order for the team to do the

checkup. So it is recommended that the team first find if they can get a hold of all the required

ground equipment and then buy the hybrid motor. It is also recommended that a drogue be used

along with the main chute so the speed of the rocket is slowed down so that the main parachute

doesn’t have to exert all of the force.

82

9.0 Appendix

Figure 9.1: Safety Liability Form F.A.R