Preparation of Papers for AIAA Technical Conferences

102 Pages·2017·11.73 MB·English

UBC Rocket – Cypress & Payloads
Team 70 Project Technical Report for the 2017 IREC
Joren Jackson1, Simon Bambey2
University of British Columbia, Vancouver, BC, V6T1Z4, Canada
Eric Bast3, Johnathan McMillan4, Tirth Kinariwara5, Riley Aldis6, Dominique Low7, Sahba el-Shawa8, Jenny Yu9,
Jordan Jones10
University of British Columbia, Vancouver, BC, V6T1Z4, Canada
Serene Pal11, Sophie Burkholder12, Robert Chisholm13, Olly Ye14, Sam Lightbody15, and Nicholas Toglia16
University of British Columbia, Vancouver, BC, V6T1Z4, Canada
Nomenclature
COTS = commercial off the shelf
CONOPS = concept of operations, the general flight profile of a rocket

SRAD = student researched and developed
C = coefficient of drag
d

1 Team Captain, UBC Rocket
2 Team Captain, UBC Rocket
3 Aerostructures Team Lead, UBC Rocket
4 Aerostructures Team Lead, UBC Rocket
5 Recovery Team Lead, UBC Rocket
6 Recovery Team Lead, UBC Rocket
7 Avionics Team Lead, UBC Rocket
8 Avionics Team Lead, UBC Rocket
9 Payload Team Lead, UBC Rocket
10 Payload Team Lead, UBC Rocket
11 Payload Team Member, UBC Rocket
12 Payload Team Member, UBC Rocket
13 Aerostructures Team Member, UBC Rocket
14 Aerostructures Team Member, UBC Rocket
15 Avionics Team Member, UBC Rocket
16 Aerostructures Team Member, UBC Rocket
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I. Abstract
T
HE Cypress Rocket is the first competition rocket fielded by UBC Rocket since its foundation nine months ago.
It is designed to travel to 10,000’ powered by a Commercial Off the Shelf motor, to deploy a payload at apogee,
and to return safely to the ground under two student designed and built parachutes. Outside of the propulsion system,
Cypress is largely student developed and constructed. Carbon fiber body tubes, machined aluminum internal structure,
3d printed aerodynamic features, a fully functional apogee detection system, and both rocket parachutes were all
designed, built, and verified by UBC students.
In order to deploy the payload, a unique recovery architecture was applied that includes the use of a non-
pyrotechnic main deployment system. This system applies common safety-critical skydiving hardware to allow both
the main and drogue parachutes to exit the rocket out of the same opening, allowing the payload to exit out of the
other end, therefore not affecting parachute deployment.
The payload system incorporates three distinct units, each fulfilling its own distinct useful purpose. The first team
developed a rocket sonde experiment capable of measuring the atmospheric boundary layer in addition to other
common parameters of interest. The second payload team aims to prove the concept of using the unique properties of
electrorheological fluid for damping applications in aerospace. The third team developed a unit to allow easy, modular
recovery of any CubeSat standard payload from apogee after being deployed by Cypress or other sounding rockets.
Overall, the goal of this year’s competition entry is to develop a foundation as a new team, and begin to build
institutional knowledge in as many aspects of rocketry as possible, so as to accomplish higher, faster, and more
advanced rocketry goals in the near future.

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II. Table of Contents

I. Abstract 2
II. Table of Contents 3
III. Introduction 4
IV. System Architecture 5
A. General Design Process 5
B. Rocket Overview 5
C. Propulsion 6
D. Aerostructures 7
1. Nose Cone 7
2. Fins 7
3. Body Tube 7
4. Internal Structure 8
E. Recovery 9
1. Parachutes and Rigging 9
2. Release and Deployment Systems 10
3. Apogee Detection 11
4. Tracking 13
F. Payload 14
1. Modular Assistive Descent System (MADS) Unit 14
2. Electromechanical Experimental Control System (EMECS) Unit 15
3. Project Ozone Unit 16
V. Note on Safety Critical Wiring and Connectors 17
VI. Mission CONOPS Overview 17
VII. Conclusions and Lessons Learned 19
VIII. Appendices 19
A. Appendix I – System Weights, Measures, and Performance 20
23
B. Appendix II – Project Test Reports 24
4. Recovery test report 24
5. Payload Recovery Test Report 32
C. Appendix III – Hazard Analysis 39
D. Appendix IV – Risk Analysis 40
40
41
42
E. Appendix V – Checklists 43
F. Appendix VI – Technical Drawings 47
1. Nose Cone 48
2. Upper Body 52
3. Lower Body 64
4. Payload 75
75
G. Appendix VII – MADS Technical Analysis 89
5. Spectra 1000 91
6. Spectra 1000 91
7. 1 ¾” Oval Threaded Link 91
8. Type II Nylon Cord 91
H. Appendix VIII – Parachute Design and Manufacture 92
References 102

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III. Introduction
UBC Rocket is a new engineering design team at the University of British Columbia Vancouver campus, hosted
under the banner of the Integrated Engineering program. Formed only nine months ago, we have already grown to one
of the largest and most active student design teams on campus. Our long term goal is to design, manufacture, and
launch a rocket to the Kármán line. At the same time, we aim to field competitive entries in consecutively more
advanced IREC categories every year.
As an engineering design team at UBC, we receive funding and support from the Department of Applied Science,
as well as the Mechanical Engineering and Integrated Engineering programs. However, a majority of funding comes
from outside sources, including large companies such as Lockheed Martin, Siemens, Fluor, Pratt & Whitney, and
MDA; as well as Vancouver-based aerospace specialists like Urthecaste, AvCorp, and Coast Rocketry.
UBC Rocket is comprised of 55 active members, representing four different faculties and seven engineering
disciplines. Our meetings on Sundays regularly bring over 45 team members together to work on our rocket. These
members are organized into a relatively flat organizational structure built around the following 5 teams:
• Aerostructures
• Recovery
• Avionics
• Payload
• Systems and Integration
Additionally, an administrative team comprised mostly of business students is responsible for the team’s finances,
social media presence, and other administrative tasks. Each subteam is headed by 1-3 subteam leads depending on the
size of the team. These leads are senior students with relevant technical and leadership experience, and are responsible
for the day to day running of their subteam. Team leads meet regularly in discussions led by the Systems and
Integration lead for higher level decisions and planning. Two team captains provide general oversight of the team and
the project. The team structure can be seen in Figure 1 below.

Figure 1. Team Structure Diagram.

This year’s entry to IREC is the Cypress rocket – named for a local mountain overlooking the UBC Campus. Cypress
is designed to travel to 10,000’ AGL on a COTS motor, maximize the use of SRAD components while minimizing
complexity and risk, and deliver a 3U Cubesat payload to apogee. The following report outlines the overall
development process of the Cypress project, design, analysis, and validation details of the rocket - including the
propulsion, aerostructures, recovery, and payload systems, and the Concept of Operations for the rocket launch.

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IV. System Architecture
General Design Process
Cypress was designed to take part in the 10,000ft category at the Intercollegiate Rocket Engineering Competition,
using a COTS motor. This baseline decision was made due to our team only having been formed last September and
all members having nothing more than basic rocketry experience. The aim for this project was to gain experience with
the various commonly used subsystems in rocketry, and to build experience and knowledge towards development of
more advanced rockets in the future.
The design process started by doing a broad study of existing designs to get an overview of basic rocket design
decisions that were made in other projects. Following this study, a comprehensive review of the rules and guidelines
was conducted which led to the creation of a requirements tracking document, which would form the backbone of all
future design decisions. As the project progressed, the design was updated and tracked to the details of the
requirements document.
Following the requirements analysis, potential implementations were identified and researched further, until a
decision could be made for the optimal implementation. For example, for our parachutes, X-type, cruciform,
hemispherical and elliptical chutes were studied for their performance, as was the feasibility of making them ourselves.
After studying tradeoffs in terms of cost, manufacturability, performance, packing volume and competition scoring,
the X-type parachute was identified as the best option, and the decision to proceed with in-house X-type parachutes
was made. This general analysis and design procedure was followed for all aspects of the rocket engineering process.
To confirm that the implementation meets the requirements, all subsystems were verified in an environment as
similar to actual flight conditions as possible. For example, the above parachutes, as well as their release mechanisms
were tested in free fall. This allowed confirmation of the coefficient of drag, as well as the release mechanisms of the
chutes in an environment that is almost identical to flight conditions.
A dedicated Systems and Integration team is responsible for overseeing this process on a rocket-wide level. This
team maintained an up-to-date RockSim (rocketry simulation software) to ensure that the rocket remained stable and
that the projected apogee is at or near 10,000’ with each design change. Each individual subteam also applied the
general design process on a per requirement level. All leads meet regularly to ensure that the whole team is always on
the same page and the most up-to-date specifications are communicated.
Rocket Overview

Figure 2. Rocket Cutaway.

The Cypress rocket consists of three main structural sections: the nose cone, the upper body tube, and the lower
body tube, which can be seen in Figure 2 above. All of these separate from each other at apogee to allow for
deployment of the payload and parachutes.
1. The nose cone section houses recovery tracking electronics, in addition to providing the typical aerodynamic
benefits of a nose cone.
2. The upper body tube houses three systems. From top to bottom these are the payload, the avionics and the
recovery system. Each of these systems is mounted in a sealed compartment to allow black powder driven
pressure separation to deploy the payload and parachutes without damaging the avionics.
3. The lower body tube houses the propulsion system, specifically the COTS motor we are flying. It is attached
to the upper body section using a coupling tube that is permanently affixed to the lower body section.
Most of our overarching design decisions heavily favoured commonly-used, well documented and proven
implementations. However, we made the decision to push the boundaries on the payload front by making it
deployable. This drove our design of the recovery system to a unique configuration where both the drogue and
main parachutes are deployed from the same side of the upper body tube, while the payload exits the upper body
from the other end. This setup allows a relatively large payload to be deployed with minimal interference to the
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rest of the rocket, however it forces the use of a non-explosive main parachute deployment method as described
in the recovery section of this report (the drogue parachute can still be deployed in a typical manner).
Propulsion
The choice of propulsion system for our rocket was one of the first design decisions that was made. Much of the
remaining design of the rocket was derived around the choice of motor. After discussions with local members of the
Canadian Association of Rocketry (CAR), we received unanimous recommendations for a Cesaroni Technologies
(CTI) or an Animal Motor Works (AMW) motor. Due to an accident at CTI, the supply of rocket engines was limited,
especially in the size range used by a rocket aiming to go to 10,000’. In order to ensure availability of the motor we
would want to use in the rocket, we needed to select one very early in the design process.
To expedite motor selection, a baseline rocket design was derived based on literature review of other similar
rockets and data collected from RockSim. This also allowed us to determine early mass estimates and dimensions that
matched the state of knowledge at that time. From this, the propulsion system requirements was derived.
1. Send a rocket to 10,000’ with the following characteristics
1. 57 – 66lb mass
2. 6 – 7” diameter
3. 6 – 9’ length
2. Allow rocket to meet IREC launch rail departure requirements for stability
3. Be a COTS motor admissible to the IREC 2017
Given these requirements and an early RockSim model, a shortlist of two rocket motors was created - one near the
bottom range of performance, and the other at the higher end. The higher-performing motor, the CTI M1790-SK was
selected as it was the only choice of CTI motor that matched our performance need with a ~10% margin. We selected
an overperforming motor since extra mass/drag can easily be designed for, whereas trying to make a design work with
an underpowered motor is more difficult and risky.
The aerostructures team designed a motor mount around the four grain (4G) motor case used for this motor. The
motor case drawings are published by CTI and allowed the team to quickly consider and design mounting options.
These are discussed in more detail in the aerostructures section.
As the design matured, flight simulations were rerun to ensure that the rocket would still meet apogee and stability
requirements. The decision to select a higher performing motor than initially required was validated, as the final rocket
will fly with no ballast, with the 10% buffer having been used to accommodate mass estimate revisions throughout
the rocket.
Further integration of the propulsion system will occur at the competition site. The fuel will be provided by Moto
Joe and they have kindly offered some assistance in integration if required as our team has limited experience with
preparing a COTS high power rocket motor.

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Aerostructures
The implementation of the aerostructures is focused on ease of assembly as well as scalability for future, more
ambitious rockets. There are three separable sections of the structure - the nose cone, upper body, and lower body. An
aluminum tube coupler joins the upper and lower bodies together on the ground - at apogee they are separated due to
the overpressure caused by black powder charges. The nose cone is 3D printed, while both bodies are constructed of
carbon fibre. The upper body houses the payload, avionics, and parachute bays, while the lower body houses the solid
rocket motor. Fins are 3D printed and attached using epoxy to the lower body with overwrapped carbon fiber. All
internal bays are machined from 6061 aluminum and use #10-24 hex drive fasteners. The assembled rocket is 7.5’ tall
and has a 6.5” outer diameter, determined by the manufacturing processes available and stability calculations from
RockSim.
1. Nose Cone

The nose cone was designed around three requirements: (1)
minimize aerodynamic drag, (2) provide a low interference
housing for transmitting electronics, and (3) provide a housing for
an outward-facing camera. After researching various nose cone
shapes, an LD Haack curve was selected for the nose cone shape
due to its performance operating in subsonic and transonic regions.
3D printing out of ABS was selected for manufacturing to
accurately obtain the LD Haack curve and to allow transmission
transparency. For quick access to electronics the nose cone is open
at the bottom. A 3D printed coupling plate, attached to the bottom
of the nose cone, connects the nose cone to the upper body tube
Figure 3. Nose cone-body tube interface.
and seals the electronics bay from the rest of the body tube. The

coupling plate utilizes helicoil tap inserts to provide a stiff and reusable fastening solution. The viewing aperture was
made in the side of the nose cone and placed at a downward viewing angle. A Polycarbonate window is fastened from
the outside using an industrial adhesive. The nose cone can be seen in figure 3.
2. Fins
The fins were designed around two requirements: (1) stay attached to the body tube and (2) provide aerodynamic
stability. A NACA 0010 clipped delta fin with 5.90” root chord length, 5.90” semi-span, and 2.95” tip chord length
was chosen based on fin design research and RockSim analysis. The NACA airfoil cross-section gives improved
stability performance versus a flat plate. The root chord length was selected, with the addition of a short lip near the
base, to provide increased surface area for epoxy adhesion and a taper for a carbon fibre overlay. Four fins were
selected to increase the drag of the rocket and eliminated the need for ballast while remaining stable during RockSim
analysis. The NACA 0010 is suitable for transonic regimes and
was 3D printed to ensure accuracy in the fin shape. The fins were
attached using a waterjet-cut jig, JB PlasticWeld epoxy putty
and a carbon fibre overlay. To validate the fin-body tube bond,
two static tests were performed on two half size prototypes in
which increasing weights were hung from the end of an
outstretched fin. The test showed that the fin would hold
upwards of 66 lbs before losing bond stiffness and 110 lbs before
complete bond failure. The expected max loading capacity will
be higher than tested due to a larger bond surface, and a better
designed carbon fiber overlay.
3. Body Tube Figure 4. Lower Body and Fins.
The body tube was designed around three objectives:

(1) strength and stiffness, (2) consistent circumference, (3)
low weight. Carbon fibre was selected for its excellent
strength to weight properties. A full aluminum structure
was considered, but ultimately rejected due to our lack of
access to suitable machining facilities. The tube was
manufactured through a wet layup on an aluminum
mandrel, as it gives the most consistent circumference to
the tubes. A vacuum pump was used in all layups to
maximize the fibre:resin ratio. Eight carbon fibre layers are Figure 5. Carbon fibre layup1.
used to give quasi isotropic properties to the body tubes, as
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seen in figure 5. A plain weave carbon fibre and Aeropoxy epoxy were chosen materials based on experimenting with
different weave patterns and brands of epoxy.
4. Internal Structure
The internal structure of the rocket was split into two sections, an upper and lower assembly, each fitting into its
own body tube. The upper assembly was designed to provide a single removable system attached to the avionics and
recovery mounts. A permanent set ring with L-shaped slots is epoxied to the upper carbon fibre tube. The removable
assembly, consisting of an avionics bay with sealed bulkheads sandwiched between a recovery bay and a payload bay,
includes a ring with two extrusions that fit in the slots of the set ring, forming a twist and lock release system. The
extrusions are threaded, and screws are attached through the body tube to lock the assembly in place. The payload bay
consists of a base plate with aluminum
angle arranged in a square, centered in a
series of rings. This angle acts as guide
rails for the CubeSat payload. The top
centering ring also functions as a stop for
the nose cone coupling plate so that it is
not compressed into the body tube. The
recovery bay includes a removable
protective shroud, and a rigging ring for
the parachutes to attach to. Black powder
deployment charges are mounted on
either side of the avionics bay, pointing Figure 6. Upper Assembly.
into both the recovery and payload bays.
This assembly can be seen in figure 6.
The lower assembly was designed around four requirements: (1) provide a strong connection point for the motor
to be installed, (2) efficiently transmit thrust
force to the lower body tube, (3) provide
resistance to strong vibrations and heat
generated from the motor, and (4) provide
strong mount points for parachute lines. Four
½’’ thick aluminum rings hold the motor and
transmit the thrust and radial loads to the body
tube. The design of the rings focused on ease of

manufacture while taking into account weight Figure 7. Lower Assembly.
reductions made possible through webbing. A
figure of the lower assembly is seen in figure 7.
The aluminum coupler connecting the upper and lower body tubes was designed to provide support to the internal
assemblies, facilitate load transfer through the rocket due to the thrust from the motor, and ensure a stiff connection
between the body tubes. The coupler is a variable thickness hollow cylinder ranging from 0.12” to 0.20”, which
provides lips on both ends for the motor centering rings to transfer load from the motor to the body tube. To validate
the adhesion between the coupler and the body tube, a short circular ring of aluminum was epoxied in a cut off section
of the body tube after being acid etched and loaded in a hand-powered press. The test showed that the bond strength
was 4000lbs, backing up hand-calculations using the adhesion strength provided by the epoxy manufacturer. The
actual coupler provides a significantly larger epoxy surface area
and therefore is expected to hold well over the maximum stress
expected during all stages of flight, as calculated using the total
rocket’s mass and maximum instantaneous acceleration. The
lower body tube with the coupler permanently attached can be
seen in figure 8.
All fasteners used in the aerostructure incorporate either

nylon thread locking nuts or the application of a thread locking
Figure 8. Lower body tube with coupler.
compound to avoid the potential for fastener backout.

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Recovery
Cypress’s recovery system makes use of a slightly modified version of the typical dual deployment parachute
system. Inside of the upper body tube, a sealed avionics bay containing the flight computers and associated electronics
is sandwiched between a parachute bay and a payload bay, which are both open on the other end. The parachute bay
includes a protective shroud inside of the black powder charge, into which the parachutes are placed. This can be seen
in Figures 2 and 6. Dual redundant flight computers detect apogee, and trigger black powder charges which separate
the two rocket sections as well as the nose cone from each other. The separating body tubes pull the drogue parachute
out of the body tube, allowing it to open. The payload falls out of the other end of the body tube and continues its
descent separately. The payload drogue is wrapped together with the shock cord between the nose cone and the upper
body tube, ensuring successful drogue deployment. The main parachute is held in the parachute bay by a 3-ring release
system mounted firmly to the recovery bay, and by a sheet of Kevlar held to the inside of the body tube with small
sections of Hook & Loop. After the rocket falls to 1500’ AGL, the main is deployed by releasing the 3-ring release
system with a linear actuator, allowing the drogue to pull the main parachute out of the bay. The Kevlar’s Hook &
Loop attachments are sized to allow disconnection under the pullout force of the drogue.
This architecture was decided upon based on the team’s desire to have a deployable payload, while maintaining a
minimal number of discrete structural tubes to minimize components, complexity, effort, and risk. Many methods for
achieving payload deployment and dual parachute deployment were identified, and the above system was ultimately
selected for the following reasons:
• All charges and avionics are in the same structure, involving no frangible electronic connections or isolated
electronics
• Only two body tubes and a separating nose cone are required
• Gravity-based payload deployment is simpler than an active system (such as springs or pressure piston) and
easily tested, and places less stress on the payload and body tube than a fully explosive based deployment
The tradeoff for this system is the requirement for a
nonstandard main parachute deployment system.
However, this gave us an opportunity to develop a
unique deployment system that has the potential to
be at least as reliable, and much less dangerous, than
black powder deployment systems.
Figure 9 illustrates the parachute bay and its
components in more detail, while figure 10 shows

the location of the recovery system with respect to
Figure 9. Recovery bay detail.
the entire rocket.

Figure 10. Operation of Recovery System.

1. Parachutes and Rigging
Both parachutes used in our rocket are X-type parachutes. The dimensions and basic drag performance values for
each can be seen in Table 1. Figure 11 describes the basic shape of the X-type parachute, figure 10 above shows the
rigging of both parachutes and their attachment to each other and the rocket and an image of the main and drogue
parachutes can be seen in figure 12.
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A significant amount of analysis and verification took place over the course of the development of the parachutes.
Various parachute types were considered, and two - cruciform and X-type - were prototyped and tested. Testing
included wind tunnel experiments on sub-scale prototypes to determine drag coefficients. The X-type parachute was
found to have good drag properties while being significantly easier to manufacture than other designs. Appendix 8
details this testing and its results. Additionally, the performance of the parachutes was validated through drop testing,
where our estimated coefficient of drag of 1.7 was found to be within 10% of the actual value (1.66 - 1.75). Finally,
the effect of the different atmospheric conditions on parachute performance between standard atmospheric conditions
(which most parachute descent rate calculators use), the atmospheric conditions here (cool and at sea level), and those
at the competition (hot and high) were analyzed and used to size our final parachutes.

Table 1. Main and drogue parachute dimensions and drag
performance.

Figure 11. X-type parachute
Figure 12. Inflated main (left) and drogue (right) parachutes.
gore diagram.
2. Release and Deployment Systems
For deployment of the drogue and payload, the sections of the rockets are forced apart out using pressurized gasses.
Since separation was a high priority task, we decided to implement arguable the most conventional separation system
used in high power rocketry - a pyrotechnic black powder charge. The
implementation of this system is done using a custom designed ejection
canister. The figure below shows a cut section view of the ejection canister.
To prevent accidental rocket separation, a tight friction fit as well as nylon
shear bolts are used on both the upper-lower body tube and upper body tube-
nose cone interfaces. Deployment tests have been carried out in multiple
orientations, including horizontally, vertically, and in free fall, and this
system proved to be reliable, robust and safe. See Appendix 3 for more
details of this verification.

The Main parachute is held in by a 3-ring release attachment while Figure 13. Steps for a 3 ring release
descending under drogue, and is deployed by releasing the attachment, system.
allowing the drogue to pull it out of the body tube.
The forces acting on the drogue suspension line are larger than can be reliably actuated by a compact linear
actuator, necessitating a mechanism for reducing the required actuation force. The 3 ring release system used is a
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