Josh firth schaefer_project_portfolio

29509 Anthony Road - Valley Center, CA 92082 – (760) 520-3141 – [email protected]

JOSHUA FIRTH-SCHAEFER Undergraduate - Physics

During my time at Cal Poly San Luis Obispo, I have been engaged in several projects of varying levels of difficulty,

importance, and complexity. These undertakings have been completed through my involvement with the university club,

Cal Poly Space Systems; they have served to fuse my growing knowledge with my passion for building rockets.

The following is a summary of the various projects I worked on since Fall 2015; note the increasing importance and

intricacy of the projects as time goes on. The knowledge I accumulated enabled me to tackle increasingly complicated

endeavors requiring more research and skill.

2015 – 2016 Academic year

Yearlong Construction of a rocket to take place in the 2016 IREC competition at Green River, Utah.

Rocket Title: Uncle SAM.

Propulsion: Student-built hybrid motor; 400lb thrust and 230 second ISP.

This was a monumental undertaking that took over two-dozen students spread across multiple subsystems to complete.

Unfortunately, due to a leaking pyro-valve, our rocket didn’t launch during the competition. However, the valve was

repaired and launched in September 2016 at the FAR facility in Mojave, CA. The rocket lifted off our launch rail

beautifully, but due to the nitrous oxide being warmed by hot desert conditions, our mass flow was lower than expected,

resulting in lower thrust. The rocket eventually broke up in flight; however, despite slamming into the ground at terminal

velocity, our hybrid motor combustion chamber survived. What follows are my contributions to building Uncle SAM.


Test Rocket 2

Our second test rocket was 6” in diameter, and was meant to test full-diameter components including electronics, the

recovery system, and possibly our active control system. However, this rocket never flew. The separator mechanism (for

splitting the rocket in half to deploy the parachute) failed during testing, the parachutes and guidance system weren’t

ready, and we were already working on a variant of our competition rocket that would use a commercial solid instead of

our hybrid motor. However, we used what we learned from manufacturing this rocket to build our third and final test

rocket; this was also the first time that I was responsible for fabricating primary composite structures for a rocket, and

the first time I assembled a complete SolidWorks model for a rocket.

Once again, I was tasked with manufacturing the engine mount and sanding the carbon body tube. I was also responsible

for manufacturing the fins using dimensions from Open Rocket (a free amateur rocket-designing software), as well as

finding a means to develop a rocket that can have its engine mount, including other components, removed, repaired, or

replaced

The CAD model I developed was

mostly used to demonstrate to the

club that I was capable of utilizing

the software, as well as to present

my engine mount design to the

Test Rocket sub-system lead. The

nose cone and separator were

designed by other club members.

My design was praised and refined

by club officers, and I later worked

on assembling the engine mount,

and fabricating the body tubes.

During the construction phase, I

designed and built the assembly of

the engine mount. Using both my

ideas for the new modular mount,

as well as the insightful

suggestions of senior members, I

cut and machined the fins, the fin

mounts, and placed barbed inserts

into the centering rings. Others cut

out the centering rings and

secured the fin mounts to the

motor mount. I also assisted in

manufacturing the composite body

tubes, and conducted all the

finishing work.

After spending until midnight in the

machine shop finishing the rocket,

we spent much time admiring our

creation. Although this rocket

didn’t fly, we were so proud of our

construction and ideas that our

final test rocket incorporated much

of the design features used on this

one. At the time, this was one of

the greatest projects I had been a

part of, though more was to come.


Aside from my usual duties of

assembling and fabricating

relatively simple components, I

was given my first task on a mill.

Six holes needed to be drilled and

counter-sunk in order to bolt on

our separator ring. I was shown

how to set up an operate the mill

as well as the rotary chuck, and

was then left alone to complete the

task. Minor milling tasks assigned

to me would become routine after

this point.

Test Fires

One of the more exciting jobs to be

done at Cal Poly Space Systems is

test fires. Our campus has a

propulsion laboratory where we can

test our motors without traveling to

Mojave. We conducted a total of

four test fires; I participated in three.

For all the tests in which I was

present, I participated in a specific

role beyond assisting in setting up

test equipment. For the first test fire,

I was a range safety officer,

whereby I ensured the testing range

was clear of people or vehicles. For

the third and fourth tests, I was

operating the control box, which

meant I was responsible for

activating nitrous and nitrogen

valves, and the engine when the

order was given. For all tests, clear

and specific test procedures were

handed out to essential personnel

and were followed to the letter.

Test Rocket 3: Valley Forge

Our third and final test rocket was built to test the entire competition rocket above the engine; this meant that the same

recovery system, control system, electronics, payload, and body would be used on Uncle SAM. The only difference was

that we used a commercial solid rocket motor instead of our hybrid motor. Unlike our last two test rockets, not only did

this one fly, but we also recovered it. The only damage was a stripped bolt holding one of the fins, knocking it loose on

impact with the ground. Our drogue chute was also torn, but was intact enough to pull the main chute out of its housing.


As usual, I was responsible for fabricating and assembling the engine mount. However, this time, I learned how to use a rotary table to cut out the centering rings and the notches for the carbon fiber fin mounts.

Unlike other projects, I found myself mostly responsible for integration and assembly rather than fabrication; I drilled and tapped holes into our new separator rings, and later attached them to the rocket. Components from other sub systems, including the electronics, recovery system, and control system needed to be integrated into the rocket according to CAD models.

We launched our third test rocket at the Friends of Amateur Rocketry facility in Mojave. I was responsible for assembly and transport. Uncle SAM Components

Among the numerous components I had to fabricate and assemble for our competition rocket, the most significant was the construction of aluminum feet that would secure carbon fiber rods to the combustion chamber and nitrous oxide tank. By now, I was known for enjoying working in the machine shop, so this job

was immediately offered to me. This was thus far the third lathe job I did, as well as the most complicated. I used more tools for this one task than in any other project. Given the relative intricacy of this task compared to others, this was the most satisfying and rewarding I had done thus far.

For this academic year, we are perusing the same goal as last year: participation in the IREC competition. We are

building a new and more powerful hybrid motor, and are using lessons learned last year to not only build a higher quality

rocket, but also to develop new procedures and techniques to prevent problems we had last year. As a devoted member,

I have been assigned as a Dedicated Manufacturer; I will be responsible for designing and machining components for

2016 – 2017 Academic Year


sub-system leads. I will be participating in design reviews, and projects of greater responsibility as the year progresses.

Additionally, my recent employment as a machine shop technician has expanded my knowledge and skills as a machinist

such that I am capable of performing all machining work that doesn’t need to be done on a CNC.

Nitrous Oxide Test Tank

My first project of the year has been the development and construction of a nitrous oxide tank capable of holding 18

pounds of nitrous at 800 psi. The idea of this tank is to have a sturdy container to protect our nitrous oxide in the unlikely

event of a catastrophic combustion chamber failure; we don’t want a ruptured oxidizer tank releasing decomposing

nitrous. Thus, beyond the pressure and oxidizer mass requirements, I was told that the tank needed a factor of safety of

at least 5 at 815 psi, and be rated to 2500 psi. Once the tank is completed it will undergo hydrostatic testing.

As one might

imagine, this isn’t

just a machining

project, it has also

been a significant

research project.

Not only have I

exceeded all of my

prior capabilities in

SolidWorks and

Excel, I have also

created my first

practical MatLab

code in order to

model the

performance of the

test tank under specific conditions. Additionally, I have

created multiple iterations of this Mat Lab code as new

and superior nitrous oxide data is found and

incorporated. This

project has

demonstrated my

ability to tackle

significant projects on

my own with

autonomy, little

instruction, and

necessary research.

As soon as I was able, I ordered my material and began

work on the tank. Pictured just above is an aluminum

cylinder that will become two end-caps for the tank. This

project has involved nearly fifty hours of work on a

manual lathe and mill, and has served as a rewarding

challenge and learning experience.

Pictured above is one of the end-plates that fits to the

very top and bottom of the tank. Being eight inches in

diameter, it couldn’t fit onto our lathe chucks, so I had to

face it on a mill.

Once completed, the tank

weighed a little over 60

pounds, just four pounds

more than what my MatLab

code predicted. The excess

threaded rod was later

removed with an angle

grinder, and appropriate

plumbing will be attached. It

is able to hold between 12

and 18 pounds of nitrous

oxide at temperatures

ranging from 20 degrees to

70 degrees Fahrenheit.

Engineering

Josh firth schaefer_project_portfolio