19 Mile High Club
Department of Mechanical
and Materials Engineering
Wright State University
Dayton, OH 45435
February 20, 2011
Senior Design Class
Russ Engineering 148
Wright State University
Dayton, OH 45435
Dear Dr. Roberts,
The following preliminary report has been prepared with the intent of clearly defining the team’s
goals and work thus far. To adequately hit all of the necessary points for this report the team
divided the work up amongst the three of us and compiled the team’s individual sections to make
one comprehensive proposal.
Our team anticipates and appreciates your response and constructive criticism of the following
work.
Regards,
Jon Welch
Alex Fletcher
Michael Adams
High Altitude Balloon Team
19 Mile High Club
February 20, 2011
Alex Fletcher
Michael Adams
Jon Welch
Dr. Joseph Slater
ME 490 Senior Design
Dr. Rory Roberts
Wright State University
Approval:
ABSTRACT
It is the intent of this senior design team to design, test, manufacture, and implement an
atmosphere reentry vehicle. Building upon the work of previous senior design teams, this team
seeks to research the documented work of teams that have tried unsuccessfully to achieve this
and successfully bring the team’s vehicle back safely.
Based on the results of previous team’s efforts, it will be necessary for this team to start
from scratch. Material selection, shape, and general function will all need to be re-evaluated.
With only a six pound limit, and working in conjunction with computer and electrical
engineering teams this team will need to implement appropriate electrical equipment to monitor
and record at the very least: acceleration data, location, and video.
The most basic description of this teams’ work is as follows: Using lighter than air gases
this team will seek to lift a reentry vehicle to 100,000 feet. At or near that altitude the balloon
containing the lighter than air gas should expand beyond its maximum limit and break. Upon
balloon breaking the team’s reentry vehicle will descend through the outer atmosphere back
toward earth. This team intends to then induce drag to aid in the negative acceleration of the
vehicle as it approaches 60,000 feet. Using the drag device it is this teams’ intent to safely return
the vehicle back to the surface of earth. At this time it is this teams’ responsibility to retrieve the
vehicle and download acceleration and video data for analysis of the effects of high altitude on
the team’s vehicle.
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TABLE OF CONTENTS
1 Introduction ............................................................................................................................. 1
2
Experimental Procedure .......................................................................................................... 7
3
Expected Results.................................................................................................................... 12
4
Budget and Personnel ............................................................................................................ 16
5
References ............................................................................................................................. 18
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TABLE OF FIGURES
Figure 1: Basic Lift Layout ........................................................................................................................... 2
Figure 2: Re-entry Vehicle with Protective Sheath....................................................................................... 3
Figure 3: Basic Vehicle Layout .................................................................................................................... 4
Figure 4: Layered Component Mounting...................................................................................................... 5
Figure 5: In-line Nichrome wire ................................................................................................................... 7
Figure 6: Vacuum Test on Great Stuff Foam ................................................................................................ 9
Figure 7: Example of Flight Tracks From Possible Launch Sites .............................................................. 11
Figure 8: Example of Balloon Flight Track ................................................................................................ 11
Figure 9: GPS and APRS Devises .............................................................................................................. 13
Figure 10: Spherachutes Suggested Sizing ................................................................................................. 14
Figure 11: Spherachutes Parachute Specifications ..................................................................................... 15
Figure 12: Gantt Chart ................................................................................................................................ 16
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TABLE OF TABLES
Table 1: Pay vs. Age ..................................................................................................................... 16
Table 2: Value of Time Spent ....................................................................................................... 17
Table 3: Licenses and Certificates ................................................................................................ 17
Table 4: Material Procurement ..................................................................................................... 18
Table 5: Total Expenses ................................................................................................................ 18
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1
INTRODUCTION
The basic premise of this design project is to simulate and assess the conditions experienced
by a Martian atmosphere re-entry vehicle. In order to do this, this team intends to use a lighter
than air gas filled balloon to lift the team’s vehicle to the near space atmosphere. Upon reaching
desired altitude the team’s vehicle will descend back toward earth, experiencing and recording
conditions relatively similar to those found around the Martian atmosphere.
The balloon is considered standard among the high altitude balloon community. It is a
simple latex enclosure that will be filled with helium prior to launch. Helium will be used as it is
relatively safe, and is still economically the best option for lighter than air purposes. There is
some concern currently related to the limited supplies of helium, and how the constant losses
through experiments like these are further depleting the reserves. It may at some time become
economically feasible to rely on hydrogen for operations of this kind. At this time however, the
team will focus solely on helium as the team’s carrier gas.
One member of each mechanical engineering team has been tasked with familiarizing
themselves with the filling apparatus associated with safely and reliably filling the balloons prior
to launch. For this team, Jon Welch was selected for this task. Jon has spent some time
familiarizing himself with the regulators, pressure switches, and fittings necessary to adequately
prepare for each balloon launch. Depending on such conditions as wind direction and strength,
atmospheric pressure, and ceiling desired Jon will need to make relatively specific calculations to
determine the appropriate volume of helium that should be used for each launch.
Because the balloon will be elevating to altitudes near space, the atmospheric pressure
will become so slight that the balloon will eventually burst under its own pressure. It is at this
time that the next phase of the team’s preparations will be put to the test. The team will be
launching two separate “packages”. The first is a “control box”. The second is the team’s reentry vehicle. These two will be attached via a tether that can be severed at the team’s discretion
via electronic servo/actuator. Accompanying the control box, which will be positioned vertically
above the re-entry vehicle, will be the team’s primary parachute as shown in Figure 1.
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Figure 1: Basic Lift Layout
This parachute will be tethered to the balloon to provide some level of insurance, should
the team’s electrical components fail. Ideally, the control box will release the team’s vehicle at
the team’s request. The vehicle will fall toward earth until it deploys its own parachute upon
reentering low atmosphere and ultimately lands safely back on earth. The potential exists
however for the vehicle to not separate from the control box. In this case the primary parachute
will be in place to slow the descent of both packages. This will hopefully allow safe recovery of
the package and the data stored in it.
The control box will house the necessary controls to facilitate the release of the test
vehicle at the predetermined altitude and location. While the control box is definitely a critical
element of this build, it is not the primary concern. The elements in the control box have been
used, tested, and documented in great detail by past groups. The team is approaching this project
with the attitude that the team will be able to take over where prior groups left off rather than reexamining and re-learning the lessons of prior groups. The team intends to capitalize on the
work of prior teams by implementing the successful portions of their designs. With this
mentality the team hopes to focus primarily on a new and possibly more exciting task.
The team’s primary focus is on the successful deployment of a parachute from the
secondary vehicle, the re-entry vehicle. The goal is to use electrical control of the release
mechanisms to allow the re-entry vehicle to free fall from nearly the time the lift balloon bursts
through 65,000 feet. At this altitude it is the intent to electronically deploy a parachute. The
parachute will be stored in a compartment at the top of the vehicle and will be attached to the
chassis section of the craft. It is the plan to use the lid of the craft as a catalyst chute. Upon
electric activated release of interior hard mounting points the lid will be aerodynamically forced
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from its position atop the vehicle. As it is slowed at a rate faster than the vehicle it will pull out
the parachute, which was stored underneath it prior to release. The light and relatively “dirty” lid
will provide more than adequate drag to pull the chute from its resting position in the upper
cavern of the vehicle.
With the parachute now deployed it will fall onto the interior chassis of the structure to
support the impulse load of the rapidly tensioning parachute lines. The chute lines connect to a
carbon fiber chassis. This chassis is the backbone of the re-entry vehicle. The carbon fiber
chassis has been determined to be more than adequate in terms of strength and rigidity.
However, relative to foam, carbon fiber is heavy. For these reasons the team opted to use carbon
fiber as sparingly as possible and only in structural demanding applications, leaving foam to take
care of the shock absorbent responsibility. While carbon fiber members will serve as the
structural backbone of the structure, the foam components serve an equally important role. The
foam components will be used sacrificially as bumpers. Even with proper parachute deployment
the package is likely to impact earth or some other solid structure attached to earth at twenty
miles per hour. At these speeds the carbon fiber chassis would likely crack or splinter
completely. Accordingly, the team will attach a foam nose cone to the team’s structure that will
absorb the impact of landing. Prior data suggests that even without parachute deployment
properly implemented foam bumpers should allow for successful landing of the team’s vehicle in
all but the worst landing conditions. In addition to the foam nose cone the team is currently
considering the use of foam bands that will encompass the outer structure of the team’s vehicle
as shown in Figure 2.
Figure 2: Re-entry Vehicle with Protective Sheath
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While the team is confident that the structure will be aerodynamically stable the team is
concerned that a turbulent landing could result in some impacts to the sides of the team’s vehicle.
The blunt of the impact is expected to be felt and absorbed through the nose bumper, not the
outer diameter of the vehicle. With this in mind, the team is considering the addition of foam
strips along the vertical direction of the structure. This will not yield complete protection but the
team is in the process now of deciding how much protection is necessary, and how much is
excessive, as the weight is the team’s largest constraint.
Figure 3: Basic Vehicle Layout
The team’s vehicle will be carrying an electronics suite that is currently being assembled
and tested by the team’s electrical engineering counterparts. The electronics will monitor and
log such things as instant acceleration, position, and video footage. The team intends to encase
their electrical components in a semi laminar the weave of wax paper and epoxy. This blend is
intended to yield the lightest possible structure that will also provide some level of shock
absorbent value. It is the team’s hope that the internal lattice will crush upon impact and protect
the relatively sensitive electronics suite housed inside. Testing is still being conducted to
determine the optimal material and layout for protection and reliability of the electronics. Early
planning called for the use of foam modules to be used for encompassing the electronics. This
strategy called for the use several layers of foam that would be fitted to each electronic
component. The foam modules would be stacked on one another in a cylindrical fashion as
shown in Figure 4.
4
Figure 4: Layered Component Mounting
This configuration would aid in structural stability as the well as shock resistance.
Unfortunately, this plan had to be abandoned due to constraints of the electrical systems.
According to the team’s electrical engineering counterparts the foam casing would generate a
static charge that is likely to interfere with the accuracy and reliability of their instruments. To
combat this static charge, discussions were held regarding the use of insulation to protect the
electronics from the static charge around them. The additional complexity and the weight
associated with this method led to steering the design in an alternative direction. This is why the
team is currently experimenting with a lattice structure of slightly harder materials
The team’s design is limited by several constraints. Perhaps the most pronounced and
non-negotiable is the weight limitations on the structure. The control box and re-entry vehicle
are allowed to sum to a total of six pounds each. FAA restrictions mandate that free falling
objects re-entering near earth atmosphere be less than six pounds. These restrictions are in place
for numerous reasons, the most obvious of which being the safety issues associated with heavy
objects careening toward earth and the structures on it. While the six pound limit may seem
arbitrary, the team is obliged to abide by it. As such every aspect of the design has been closely
examined to determine if it is as light as possible. Every structural component has been chosen
and thinned to the least possible mass to achieve this goal. The idea, being to save weight for
important components like batteries and electronics. In order to save as much the weight as
possible this group has opted to use, for the first time, carbon fiber structural components. Past
designs used entirely foam structural members and geometry. While foam is incredibly light and
excellent for absorbing an impact it leaves some to be desired in terms of strength to the weight
ratios. For this reason the team opted to use foam as much as possible, but leave the load
carrying to the much stronger and lighter per mass necessary carbon fiber. The use of carbon
fiber as the primary chassis allows rigid mounting points for the additional hardware as well.
The team’s goal is to provide the electronic engineering compliment with as much of the weight
available as possible. While the structure could weigh the entire six pounds, this would not leave
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much of the weight allotted for actual electronic activity. Without the electronics the team is
simply dropping dead dumb the weight. It is the team’s intent to use the weight to strength ratio
of carbon fiber as the well as the shock absorbent properties of foam to maximize the usefulness
of the team’s re-entry vehicle. By providing the electrical engineering group with enough space
and the weight carrying capacity the team hopes to be able to launch, utilize, and recover a
scientifically useful vehicle.
Reliability of all systems is second only to the weight in terms of rigid constraints. The
entire system will experience 100+ mph winds, -40 degree F temperatures, and the low pressure
environment associated with near space altitudes (roughly one kPA). As a result all systems will
need to be rugged and reliable. Additionally, steps are being taken to make as many necessary
systems as rudimentary as possible. Batteries, mechanical linkage, and soldered joints are of
primary interest as the extreme temperature variance is likely to wreak havoc on the designs.
The chemical reactions necessary for batteries to supply the necessary current to the devices may
be slowed to unreliable levels. The electrical engineering team will be responsible for ensuring
reliability of all electrical components. However, those electrical components will be actuating
mechanical devices housed within the control box and re-entry vehicle. These mechanical
elements will most definitely have moving mechanical components that are susceptible to
mechanical failures due to the adverse conditions they will be expected to function reliably in.
Accordingly, the team is in the process now of designing connections and systems that will
reliably release the vehicles lid 100% of the time. To achieve this, the team is intending to use
simple proven techniques. For example, it is absolutely critical that the lid separate from the reentry vehicle. In order to ensure reliability of this function the team is employing a dual release
mechanism. The primary clamping device is a radius line that is strung to the lid and held on
with mechanical connections. Upon electrical activation the clamp, a simple lever style tong,
will release and allow the forces that be, to propel the lid away from the main structure. Should
that system fail the radius line has two separate sections of nichrome wire in series with radius
line, as shown in Figure 5 the severing of either will cause lid separation. In a sense this will
provide a triple/double redundancy system to ensure reliable separation of the lid portion of the
vehicle. The remainder of the electronics suite will conform to prior design specifications as the
bulk of them have been tested and used in the past with great reliability. The tracking and
accelerometer systems have been used and documented throughout the course of several senior
design teams. Consequently the team is focusing its attention on the new and untested systems
associated with parachute deployment reliability.
6
Figure 5: In-line Nichrome wire
Overall platform stability is also a primary concern of our team. Tangling and line
fouling has been the Achilles heel of prior attempts to successfully deploy a parachute at altitude.
These tangling issues are directly related to flight instability. If the vehicle is experiencing uncontrollable alterations in negative acceleration and flight trajectory it is not difficult to imagine
unreliable parachute deployment. The ballute design is intended to slow descent primarily and
secondarily to be stable. As such, the team has opted to use a more stable and reliable shape.
The use of an aerodynamically clean structure will provide the structure with ample stability to
maintain steady free fall, ensuring reliable deployment of the parachute and the associated lead
lines. The team is taking a risk however that the parachute will deploy successfully, as the use of
such a lean and slender vehicle will induce minimal drag and impact earth at high speeds if the
parachute is unsuccessful. Even without parachute deployment the bailout design will induce
significant drag and impact earth at roughly 40 mph. The team is not prepared to estimate the
speed of the vehicle at the time of impact; however the team is confident that it will be faster
than previous designs. That said, the team is focusing efforts on the reliable and successful
deployment of the parachute.
2
EXPERIMENTAL PROCEDURE
The major constraint for the Wright State High Altitude Balloon Project is federal
regulations. In order to bypass obtaining permission from the Federal Aviation Administration
(FAA) it is necessary for each package on the balloon to be less than six pounds. This is referred
7
to as an exempt launch. Each balloon may carry up to two packages. The FAA guidelines
regarding exempt balloon launches can be found in Federal Aviation Regulation (FAR) Part 101.
Although launches performed by the Wright State High Altitude Balloon Project do not require
FAA approval, all balloons and packages must stay out of restricted airspace. As a courtesy to
the FAA, the Balloon Team always provides the FAA information about the launch as the
predicted flight path.
The package will be released from the balloon at approximately 100,000 feet. The
package will then be in free fall to 65,000 feet at which time a parachute will deploy to slow the
package down. A virtually endless number of shapes for the package are available. The chosen
shape for the package will have a great effect on the aerodynamic performance of the package
during the free fall stage. A popular shape for the package is a ballute. Ballute is a combination
of the words balloon and parachute. It has the benefit of being stable in flight and acting as its
own parachute.
The chosen shape for the teams’ project is shown above in figure 3. This shape was
chosen due to several factors. First the shape looks like it will be very stable in free fall flight.
Second the carbon fiber midsection was donated to the balloon team. Since this presented a great
opportunity to incorporate an advanced composite material on the package, the design was fit to
this component.
To ensure the package remains under six pounds, material selection is an important
consideration. Past designs have been constructed from polystyrene foam. The benefits of
polystyrene foam are low cost, relatively light weight, and high impact absorption. Some of the
past designs have included high density polystyrene foam which should be avoided as this
increases the weight. Part of the design should include some type of foam in order to observe the
shock of hitting the ground. Advanced composite materials such as carbon fiber and Kevlar were
researched. These materials are beneficial due to their high strength-to-weight ratio. A frustum
made of carbon fiber was donated to the group by a local company who wishes to remain
anonymous.
The design shown incorporates the carbon fiber as the mid-section of the package. The carbon
fiber will act as a chassis on which electronics can be mounted. The bottoms section is the nose.
This is to be made of low density foam which can absorb large amounts of energy. Currently the
product Great Stuff is being studied to see if this is a suitable material. Great Stuff is a spray
foam commonly used to fill in gaps in insulation. The idea is to spray this foam into a mold lined
with a heat shrinkable wrap. Once the foam is cured, a heat gun can be used to tightly fit the
wrap around the foam. The product under consideration for the heat shrinkable wrap is Ecokote
which is commonly used to wrap model airplanes.
To insure the durability of this foam several tests have already been performed. A piece
of cured foam was placed in a cooler filled with dry ice to simulate the low temperature at
8
100,000 feet above mean sea level (msl). The foam was left in the cooler for 30 minutes. The
foam was at first a little more stiff but quickly returned to its natural state. A piece of the cured
foam was also placed in a vacuum chamber to simulate the low density air present at 100,000
feet msl. The foam did not noticeably change shape or decrease in volume in the vacuum
chamber. The vacuum chamber was at 10,000 pascals however the pressure at 100,000 feet msl
is 1,000 pascals. Both the low temperature test and vacuum chamber test were considered a
success for validating the usability of the Great Stuff foam. Figure 6 shows the vacuum chamber
containing the cured foam.
Figure 6: Vacuum Test on Great Stuff Foam
The top section of the package will also be constructed out of some type of foam, either
Great Stuff or polystyrene foam. This section will be circular in shape. It will be attached to the
rest of the package using a nylon cord. Part of this nylon cord will have nichrome wire attached
to a battery power supply. When the parachute is to be deployed the power supply will be
activated which in turn heat the nichrome wire and melt the nylon will cord. This will allow the
top section to fall away from the rest of the package. Several tests using nichrome wire were
performed and each showed the wire melting through the nylon cord with no problem. To insure
that the top piece falls away the top circular section will have a larger diameter than the
midsection. This will allow the air to catch the top section and release it. Another benefit of have
the top section larger than the rest of the package is to induce some more drag on the package as
it is in free fall descent.
When the top section is jettisoned from the rest of the package, the parachute will then be
deployed. The parachute will lay folded just beneath the top section. As the top falls away they
parachute will be free to deploy in the air flow. The goal is to have parachute deployment occur
at 65,000 feet msl. To help the parachute deploy in the low density air present at 65,000 feet the
team is looking for ways to help propel it from the package. One possible idea is to attach a small
9
piece of wire from the top section to the parachute. When the top falls away it will help pull the
parachute out of the package. The challenge with this is to choose a material for the wire that
will be strong enough to help pull the parachute out but also be the weak enough to allow the top
section to break away once the parachute is deployed. The parachute that has been ordered for
this project is 48 inches in diameter when fully inflated. Past attempts have used a 60 inch
parachute, however the 48 inch parachute was chosen as it is designed for payloads up to six
pounds and it is 2 ounces lighter than the 60 inch.
Before a launch can take place a flight path must be performed. Steve Mascarella has
created a balloon tracking program in excel. The program uses wind speed data obtained from
the National Weather Service along with user input data of package weight and parachute
diameter. The program calculates balloon tracks for all possible launch sites. An example of
flight tracks from the possible launch sites is shown in figure 7. The results then rank the sites to
show which launch sites are not permissible. Launch sites that would not be permissible have
balloon tracks going through restricted airspace or have the package landing more than 60 miles
from Wright State University. From these results a launch site is chosen, normally based off the
conditions of the projected recovery site. An example of a good recovery site would be a farm
that is not near any major highways or other dangerous areas. A poor recovery site would be a
forest or populated area. The balloon track is typically accurate up to several miles. A sample
balloon track is given in figure 8. Once the launch site is chosen, permission is obtained from the
owner of the property. Before the balloon and package are launched a courtesy fax is sent to the
FAA.
10
Figure 7: Example of Flight Tracks From Possible Launch Sites
Figure 8: Example of Balloon Flight Track
11
While the mechanical engineering focus of this project is on the package itself and the
deployment of the parachute, an important task is working with electrical engineering students
on the contents of the package. The team has been working closely with team BluSkye consisting
of Leila Carmichael, Meshal Albattah, and Nathan Binkley. These students are working on
placing several video cameras inside the package and transmit the video feed to the TV antenna
on top of the Russ Engineering building. The video feed will also be recorded in a DVR inside
the package. The teams would like to have one camera placed inside the package pointed
upward. This camera would just be used to show the top section falling away and the parachute
deploying. Another camera will be shooting through a hole or window in the control box to film
the outside.
The control box will consist of a polystyrene cooler that will house all components that
do not need to be the package. Components that can be housed in the control box include: radio
transmitters, GPS receiver, balloon cut down wire, DVR, etc.
To help validate the design chosen for this project an FEA analysis will be performed on
the internal structural framing using ANSYS. These results should show how the frame will react
upon impact. The worst case impact scenario would be in the parachute did not deploy and the
package remained in free fall for the entire descent. From past experience the packages struck the
group between 35 and 45 miles per hour. The FEA analysis should help to determine it the
design can survive this worst case scenario.
In order to study the aerodynamics of the design prior to an actual launch, a CFD analysis
on the package is planned. Currently different CFD programs are being researched to determine
which one will generate accurate results but also has a small learning curve. Outside consultation
may be sought from Dr. John Tam of AFRL on the CFD aspect of the project. To further analyze
the aerodynamics of the package an accelerometer and data acquisition package will be placed in
the package.
The team plans to hold together each section of the ballute with some sort of a bolt.
Currently a piece of threaded pvc pipe is acting as the bolt. This was made by simply threading
two foot section of ½ inch diameter pvc pipe. A mechanical bolt analysis of the bolt will be
completed to determine if it will be able to withstand the loads encountered during a flight.
3
EXPECTED RESULTS
Wright State has been doing this project for many years. With that history there are not too
many things that can come completely unexpected. The team has been lucky that so many
capable teams have preceded it. Many different configurations have been used and they all have
some advantages and disadvantages. The tear drop type approach is at first very intriguing1 . It
has most of the room at the bottom allowing the center of gravity to very low inducing a more
12
stable free fall. The drawback however is that the main reason for this project is that NASA is
looking for a ballute design for a Martian atmosphere entry vehicle. The ballute offers a high
drag design but by nature is top-heavy. This characteristic makes the freefall unstable and
increases the complexity of the project. Considering these options the team settled for a less
conventional ballute design. With a narrower lower and an overextended upper the team is
intending on having the upper create considerable drag which will induce the top to remain
higher than the lower. This will produce a more stable platform and eliminate the capsules
tendency to tumble.
Onboard the capsule will be many instruments in order to verify that the freefall was
stable. The team decided that to include in these components an accelerometer and multiple
cameras. The accelerometer will sense and record the different attitudes and movements made
by the capsule for the entire descent. This raw data will be analyzed and interpreted to give the
team this important information. The EE team will be needed to help in this endeavor. The EE
team has plans of splitting the signal from one of the cameras to a direct feed to the ground and
to a DVR. Part of the team’s requirements is to install an external antenna on the payload in
order to send the direct feed signal back to the school. Also included in the package are GPS,
Automatic Packet Recording System (APRS), and multiple other communication and positioning
devices for payload retrieval (Figure 9).
Figure 9: GPS and APRS Devises
An important aspect of a design is the materials chosen. The major constraint in this
project is the 6 lb. the weight limit. Any material used will have to have an impressive strength
to the weight ratio and be available. Foam is always a candidate because of its easy accessibility
and shock absorption qualities. Some of the problems with foam are its brittle and tensile
strength characteristics. Balsa wood is also a possibility for its strength and light weight but the
team was concerned about the reusability of the material. Carbon fiber is in the team’s
estimation a “dream material.” Generally the cost of carbon fiber is a hurdle for its use in this
type of production environment. The material requires costly equipment and a set of expert
13
skills above what the university is willing or capable of supplying. To the team’s great pleasure
the team has arranged the procurement of a carbon fiber chassis. There is considerable
excitement to see how well this material will test.
The capsule will have to undergo many analyses before being deployed. The many
designs will be drawn in SolidWorks and subjected to CFD (Computational Fluid Dynamics)
testing. The results of this testing will greatly influence the final dimensions of the capsule’s top.
The current design is a partial dome with the center raised only a couple of inches higher than the
sides. This might be changed to a higher bulge depending on the CFD testing. An added benefit
could be more room for the parachute and parachute release equipment.
This leads us to choices in parachutes. In previous years the common logic and advisors
suggestions has always been to incorporate a 60 inch parachute into the capsule1 . The team’s
research followed the manufactures information and found that they produce their 48 inch to
handle a maximum payload of 6 lbs (Figure 10).
Figure 10: Spherachutes Suggested Sizing
Due to FAR 101 regulation the team’s entire capsule the weight including the parachute must be
6 lbs or less. The team also discovered that downsizing to a 48 inch parachute also saved us 2 oz
(Figure 11).
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Figure 11: Spherachutes Parachute Specifications
The 48 inch seems to be a good fit, but the drag and impulse testing will have to be completed to
be sure. The first drop is scheduled for March 6th. It is the team’s intention to have the capsule
ready for a parachute deployment test. This drop is mainly an Electrical Engineering mission
critical operation so there is nothing ballute related required of the team. However, it is a good
opportunity to test everything that can be made ready by that date.
To date no High Altitude Balloon team has had a successful parachute deployment. This
fact makes engineering a working design highly motivating. Many different teams have tried
very unique ideas to complete this task. Almost everything from compressed air to combustible
material has been employed to engage the parachute. After researching the reports and several
conversations with advisors it is believed that none of the previous teams have contacted
professional parachute packers to get an explanation of proper techniques. The team has
contacted a skydiving school that is willing to spend a couple of hours to give a quick overview
of proper packing instruction. The team has yet to schedule the lesson due to time constraints on
both parties but since this is a high priority for the team, accommodations will be made.
Understanding that this is a skill that probably will not be mastered on the first attempt, makes
the March 6th date all the more important. Proper packing techniques are important but that isn’t
the only worries for parachute deployment.
A parachute release mechanism is just as, if not more, important as the packing. It is the
team’s intent on releasing the domed upper to a tether. This action is the catalyst for the
parachute deployment. No matter how the well the chute is packed if the lid doesn’t open it’s
over. Researching this challenge has produced as many questions as answers. What will be the
release mechanism? Will the redundancy be of the same type or not? What are the most reliable
designs used? Is it better to try a new idea? Or should an old idea be tweaked and improved?
One of the previous ideas included the use of servos. They are reliable, easy to use, and simple
to install. They are also heavy and require room to work. Nichrome wire is another favorite. It
too is reliable and easy to install, but it requires more battery power and is more fragile. One of
the earlier attempts put too much force on the wire and it broke under the intense turbulence of
the upper atmosphere. In the end the team decided not to reinvent the wheel. Nichrome seems
to be the most capable candidate. The most promising design ideas is to rig the nylon string
keeping the dome in place before deployment in such a fashion that two eyelets firmly fastened
to the ballute carry the load of the lid being vibrated during the turbulent freefall. The nichrome
wire will be attached to the nylon via wire ties in between the eyelets and free from the loads.
This design also allows us the ability to add another nichrome wire anywhere between the
eyelets for redundancy. Keeping the redundant mechanism of the same type relieves the team of
15
having to install many different types of equipment. The less equipment that goes into the
capsule the easier it is to stay within the 6 lb. the weight limit. With this design the nichrome
should be in constant contact with the nylon with minimal strain on the wire itself.
To date the team’s progress has been on schedule. Figure 12 below indicates the team’s
progress and scheduling thus far.
Figure 12: Gantt Chart
4
BUDGET AND PERSONNEL
The following table has been prepared detailing all expenses. The expenses incurred are
broken up by categories including time spent on project, license and documentation, and
materials. The team will be adhering to the standard table of “engineering salary” to determine
the financial value of the team’s time spent on project
Engineers
Average
Age
Salary
0-24,
$54,642
25-29,
$65,761
30-34,
$83,580
35-39,
$88,441
40-44,
$94,058
45-49,
$93,648
50-54,
$93,038
55-59,
$98,910
Table 1: Pay vs. Age
16
Table 2 describes and lists the expenses accrued due to the team’s time spent working on this
project.
Team
Member
Age
(years)
Pay
Range
Worth ($)
$/hr
Alex
Michael
Jon
22
25
39
0-24
25-29
35-39
54,642
65,761
88,441
26.27
31.62
42.52
Hours
Spent on
Project
62
58
65
total
Wages
Due ($)
1628.75
1833.72
2763.78
6226.25
Table 2: Value of Time Spent
Table 3 describes and lists the expenses accrued purchased licenses and certificates.
Team
Member
Jon
Alex
Michael
License
Ham
radio
Ham
radio
Ham
radio
Expense Frequency
($)
Total
($)
15
1
15
15
1
15
15
3
45
total
Table 3: Licenses and Certificates
17
75
Table 4 describes the expenses of procured materials
Material
Qty
Desc.
Greatstuff
Tensioner
C.F.
Cooler
Bowl
PVC
NSF PE
2
1
1
1
1
1
1
CF
1
scale
1
expandable foam
line tensionor
carbon fiber
Control box
form for lid
.5" x 5'
.5" x 5'
Carbon Fiber
Structure
Lab Scale
cost/unit
($)
Total
($)
4.53
5.23
0
2.99
5.59
3.23
2.55
9.06
5.23
0
2.99
5.59
3.23
2.55
5000
5000
41.99
Total
Table 4: Material Procurement
Table 5 compiles all expenses accrued to date.
Expense
($)
Hours
6226.253
Licenses
75
Materials 5070.64
Total
11371.89
Table 5: Total Expenses
Type
5
REFERENCES
1.
Figure 10 & 11: www.sperachutes.com
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41.99
5070.64
2. Design and Launch of a Reentry Vehicle for Near Space Experimentation; Wright State U
niversity, HAB Team 2008-2009
3. Mark Spoltman; Composites Expert, Hartzell Propellor, Piqua Ohio.
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