System Overview:
The weather balloon assembly built by the Launch PSU ’05 team is comprised of
three distinctive elements: a balloon, a parachute and an imaging/tracking payload. At
the top of the assembly and arguably the most important component is the balloon itself.
This is connected to the parachute with 50 lb test kite string, which is used for all of the
assembly connections. From the parachute, individual loops of kite string are attached to
small carabiners located at each of the four corners of the protective bag that enclose the
payload box. The polystyrene payload box contains a GPS/radio unit with an antenna
built into the lid, a resistive heater element and an imaging system comprised of two
digital still cameras and one digital camcorder. Also included in the payload box are
battery packs to power the resistive heater and the GPS/radio unit as well as a timing
circuit to run the digital camcorder. Protruding from the bottom of the payload box is an
emergency strobe light used to make visual contact with the balloon assembly in the night
sky. Detailed descriptions of all of the components comprising the balloon assembly can
be found below.
Assembly Schematic
Balloon:
Launch PSU: IMAGE ‘05 uses the same type of balloon as the previous year's
team. We have examined the altitude requirements, payload weight, and delivery time
constraints, keeping in mind that we have only eight academic weeks to launch. In
addition, with the previous launch gaining an altitude of 116,760 ft, we thought it would
be easy to achieve the extra 14,000 ft by simply lightening our payload. The balloon,
which is purchased from Raven Industries, is made from 0.35-mil polyethylene with a
“burst-panel” designed to rupture at a designated altitude at the top of the balloon. From
the manufacturer's website, the final volume of the balloon is estimated to be 54,000 ft3
when fully inflated. Helium is used to fill the balloon due to its safety over hydrogen.
Compared to other balloons, especially latex or totex, the polyethylene balloon is
much more likely to reach 130,000 ft with our payload than any other. The free lift
characteristic of the polyethylene balloon outperforms all other balloon materials and is
the deciding factor for our final balloon purchase. Due to the high cost, only one of these
balloons was purchased which leaves no room for error.
Filler Assembly:
Polyethylene balloons, like the one purchased, do not expand like latex or totex,
but allow their initial volume of gas to fill the entire balloon before rupture. The balloon
we used is initially over 50 feet in length and to fill requires roughly three 245 ft3 helium
bottles.
The balloon is filled through a neck, which we call a “snorkel,” at the top of the
balloon. The neck is approximately 25 feet long and 6 inches in diameter and made of
the same thin material as the main balloon, which creates a stability issue with the helium
from the tanks exiting at a pressure of 2200 psi. At this pressure, the velocity of the gas
leaving the tank is sufficient to rip the neck wide open. To solve this problem, we use a
diffuser system that was developed by last year’s launch team. Its construction is
detailed in the Launch PSU '04 report.
The main balloon filling procedure is detailed in Appendix F along with a
procedure designed as a backup in case the primary failed. In short, our main procedure
takes into account an unforeseen difficulty from last year in the balloon filling, which has
to do with pulling down on the snorkel while determining the lift on the balloon. Pulling
down reduces the lift such that more gas is needed before the balloon can lift the tare
weights. We theorize that this can be taken care of by simply raising the snorkel slightly
until the gas moves from it to the balloon, letting the snorkel slacken slightly, and then
checking the lift.
Parachute:
In order to determine an appropriate parachute size and shape for our payload, we
have researched the Internet for parachute calculations (solved for drag vs. weight) and
suppliers. As a starting point, we used a parachute calculator that last year’s team found.
We later concurred these calculations with tables produced by manufacturers that
correlated payload weight with parachute size.
The calculator can be found at:
http://www.washingtonhighpower.com/Chute%20Calculator.htm
A system weight of 8 pounds (which includes the payload, parachute, and two
extra pounds of lift) is used with a descent rate of 15 ft/s and a launch altitude of 5,000
feet to determine the size of parachute needed. The descent rate needs to be small
enough to prevent damage to the cameras and tracking equipment.
We chose to use a 72-inch, hemispherical parachute, because it requires a smaller
size compared to round or x-form parachutes, translating into less overall weight. The
initial “catch” of the hemispherical parachute in the air produces a greater shock than that
of the “softer” opening x-form, but this was deemed not to be a problem since the small
size of our payload would likely not break the 50-lb test string.
After ordering and receiving the parachutes, we tested them by dropping a testbox off of a six-story parking garage as seen in the figure below. The parachute opened 4
out of 5 times, and the box floated to the ground at an easy pace.
Parachute test
Payload Box:
The module (SPOT) is created from a 2” thick polystyrene container with outer
dimensions of 10.25”x 9.75”x 10.75” and a volume of just over .30 ft3 on the inside. One
of the FAA restrictions for high altitude balloons is that no face on a payload box can
have over 3 oz. per square inch. With the smallest face being 100 in2, the weight limit
could have been be up to 20 lbs., but the FAA also restricts flying any payload over 6
lbs., with an absolute maximum of 12 lbs. (See Appendix D for FAA Regulations.) Since
SPOT was only one box, it is capped with a maximum weight of 6 lbs.
Polystyrene makes a great foundation for a high altitude balloon module. Some of
the benefits are:
• Light weight
• Easily manipulated / easy to work with
• Low thermal conductivity
• Inexpensive
• Easily accessible (you can purchase a small bait cooler from almost
anywhere for a few dollars)
Plain polystyrene box
Preparation of the payload box:
SPOT is primarily carved out by using a grinding bit with a high speed Dremel
tool. Hand held 120-grit sandpaper is used for smoothing and finishing work. When
creating SPOT’s camera ports, a Dremel cutting disk is ground down to the desired
diameter then plunged through normal to the surface in the proper location. For cutting
out the larger diameter holes, the Dremel is again utilized with a grinding bit attached and
a metal ring used as a template. A template can easily be made to any diameter needed if
a CNC machine is accessible.
Cutting a bore through the polystyrene
Since SPOT’s walls are 2 inches thick and the camera lenses only protrudes 1
inch, countersinks are needed to keep the side of the box out of view of the cameras. A
countersink tool can be made from a 16oz water bottle, glue, and some sandpaper. The
steps to produce this tool are:
1.
2.
3.
4.
Cut off the top of the plastic bottle
Cut 5 to 6 strips of sand paper 3/8” x 2”
Glue strips vertically around the top of the bottle
Allow glue to dry sufficiently before using
Once the countersink tool has time to set, it is lined up with the hole sight and
twisted perpendicular to the box. Light pressure is applied to the tool, being careful not to
apply too much pressure and possibly damage the box. The tool is continuously twisted
until the proper depth of the countersink is achieved.
Countersink tool
Countersink tool in action
Finished Countersink
This process is repeated for the three camera ports located on different sides of the
module. Each and every component has some sort of custom cut out in order to fit
everything inside. See below for detailed drawings of the module.
There is one data logger that is used to measure outside pressure during the flight.
In order to read the outside pressure, the logger needs to be ported to the outside of the
box. It is too difficult a task to drill a clean hole in the polystyrene, so an under cut hole is
drilled, then a plastic tube is gently pressed through until flush with the inside wall.
Epoxy is applied around the openings to help secure the placement and limit any
unwanted venting. Adhesive backed Velcro is also used as the common attachment point
for most of the components.
Tube, outside of box
Tube and Velcro, inside of box
The list of other cuts made to the box were:
• Camera ports 3X
• Internal pocket for data logger
• Internal pocket for heater batteries
• Slot to allow video camera to slide in
• Timer cut outs 2X
• Timing circuit cut out 1X
• Strobe cut out 1X
• Heater mounts 3X
Modified box to accommodate components
Camera port locations
Box Bag:
Our design criteria for attaching the payload to the rest of the system requires that
we make a bag with multiple attachment points that can act as a cover over our box. The
bag needs to have at least the outer dimensions of the payload box (10 “ X 9 “ X 10 “),
but with a tight enough fit to prevent it from moving around and blocking the cameras. It
also needs to be tough enough to absorb forces and shocks produced by the balloon
lifting it into the air and the parachute catching on the way down.
Our team decided to make the bag out of a rescue-orange nylon material. The bag
is cut from one piece of material, in a “cross” formation, to reduce the number of edges
that need to be sewn with each edge having a 1-inch overlap. The overlap from one edge
of the box is sewn to the overlap of the adjacent edge, which allows large areas for
sewing and greater stitch-integrity. Velcro is sewn along the inside of the lid of the box
and the outside of the top of the box. We use a black mesh material sewn to the eight
corners of the box, looped through black d-rings, to act as attachment points. These
straps are sewn to the body of the bag. We had a laminated nametag made with our
school and address on it, which is attached to the bag via a mesh material.
Holes are needed in the bag as ports for our cameras, beacon strobe light, and
antenna. Two holes are cut on the opposite short sides of the bag for the still cameras,
one hole on one of the long sides for the video camera, one hole in the bottom for the
beacon light, and two small holes at the top of the long sides for the antenna to stick
through. These holes are reinforced with stiching to make sure they cannot rip in midflight.
A schematic of the bag appears in Appendix H, and below is a picture of the
finished product with the carabiners used to attach the parachute to the bag.
The finished bag with carabiners
GPS/Radio:
TO BE COMPLETED (OR COPIED AND PASTED) BY JOSH HATCH!
Resistive Heater:
Since the balloon module is traveling up to an altitude where the temperature is in
excess of –70 °C, a heating system was designed to keep all critical components within
their operating temperatures. The first step towards building a heating system is to
estimate the expected heat loss (See Appendix C for calculations). In making the
estimate, all components inside the box and their operating temperatures are considered.
The cameras and data loggers are known to function only above 0 °C. With an outside
temperature of –70 °C, the worst-case temperature difference is used in calculating the
estimated heat loss. SPOT-05 had a total estimated heat loss of 6 Watts.
One simple way to make a heater is to apply a current through a resistive material
that will then heat up. Three separate designs for a heater were considered for this
project. The first is a flexible neoprene heater that is a custom unit ordered from a local
vendor that has a 2-week lead-time. The draw back from this design is that it requires
extremely high amperage that cannot be achieved with out flying a motorcycle or small
car battery. The additional weight from flying one of these larger batteries would put the
balloon outside of the FAA regulations (See Appendix D). The positives about the
neoprene heater are that it is flexible and is able to wrap around the inside of module
allowing conductive heat transfer amongst the components when there is no air left inside
the module.
Previous balloon missions have used batteries connected to resistors to make
heaters inside their boxes. Two resistor type heaters were constructed and tested. The first
design is made up of eight 40Ω aluminum wire clad resistors connected in parallel. The
bank of resistors is powered using six 9V batteries in parallel. This heater produces 16.2
W but the draw off the batteries is not sufficient over a long period of time. The second
heater built is made of five 1Ω ceramic resistors connected in series. This heater also
produces 16.2 W when connected to the six 9V batteries, but the surface temperature of
these resistors is measured at 128 °F as compared to only 85 °F for the aluminum
resistors. The heating element is made out of aluminum because it is easy to work with,
readily available and conducts heat much better than plastic or phenolic. With
conduction as the primary mode of heat transfer from the resistors to the aluminum
element, the ceramic resistors were chosen because of their higher surface temperature.
The aluminum resistors are too efficient of heat sinks to be used for this design.
Aluminum resister heater
Ceramic resistor heater
An FEA (finite element analysis) was performed using Pro-Engineer’s thermal
modeling package. The results below show that the heating element is able to maintain
temperatures between 86 °F and 90 °F. Conditions for this model are with the ambient
temperature of 40 °F and only 1.7 W per resistor. The resistors are attached to the
aluminum with 3M Scotch Weld epoxy.
FEA of heater element shows the heat distribution
The final heating element is configured to use four 1.5 V C-cell batteries instead
of multiple 9V batteries. The 9V batteries have very low discharge capacities despite
their high voltage. The standard discharge rate for a 9V is .120mA with a capacity of
1200 mAh. The C-cell batteries have an 8.3 Ah capacity and approximately 2.5A
continuous discharge rate that would allow the heating system to work for a total of 3.5
hours. Since the estimated flight time could possibly exceed 3 hours, the heater is
designed to turn itself on or off as needed to help extend the life of the batteries. To
complete this task, a snap disk thermostat is installed inline with the heater’s power
source.
STO-85 Snap disk thermostat
The thermostat has a preset value for it to open and close. An ST0-60 and STO-85
were both tested inside a freezer and then compared to see which would meet the heating
requirement. The STO-60 has an opening value of 13-18 °C, but when tested it failed to
reset until the temperature was well below the published reset value of 2 °C. This is too
close to the failure temperature of the heat dependent components making it an unwise
choice. The STO-85 has an opening value of 27 to 32 °C and when tested it worked well.
With the STO-85, the reset value is 19 °C, which is low enough to not risk damaging any
of the onboard equipment. The STO-85’s higher opening value also doubles as a failsafe
to prevent the heater from overheating the inside of the box (See Appendix E for test
results). To ensure that heater element would not melt the box at the mounting points,
Delrin slugs are inserted to support the heater. These slugs also prevent wear and damage
to the box from inserting and removing the heating element. In order to increase the time
it took for the heater to turn on and thus prolong the battery life, all the components are
pre-heated using a heating pad along with a set of ski boot dryers.
Assembly drawing of heater
Parts list for heater assembly
The heater is inserted into the back Delrin plugs followed by the mounting
bracket slipping into the third Delrin plug. After the mounting bracket is extended all the
way, two 6-32 socket headed cap screws are tightened to secure the heater in place.
The components diagramed below were fabricated from 1/16th thick aluminum.
Each piece was cut out using a band saw and all slots and holes were completed with a
mill and drill press.
Main heating element
Heater mounting bracket
Imaging System:
Imaging is deemed to be a key goal for the Launch PSU ’05 system. We are
particularly interested in capturing high resolution still images of the sun rising over the
curvature of the earth and digital video of the descent of the payload and parachute. The
final payload design includes two digital still cameras facing out 180° from one another
as well as a digital video camera facing out of one of the remaining sides of the box. The
digital still cameras used are Canon Powershot S70s which feature high resolution
imaging at 7.1 megapixels as well as the convenience of a built-in intervalometer which
allows the cameras to be programmed to take pictures every two minutes for a total of
one hundred pictures during the flight. The cameras are outfitted with 1 GB memory
cards that provide sufficient space for the storage of 100 full resolution images. The
batteries that come with the cameras have sufficient capacity to power the cameras for the
duration of the flight. Furthermore, their overall weight comes in at just over a pound,
which makes them an ideal choice for performance and weight efficiency.
Canon Powershot S70
Digital video is chosen as the best option for the flight because of the availability
of small lightweight digital camcorders as opposed to their bulkier and heavier analog
counterparts. A Canon Elura 50 model is selected because of its weight, coming in at
under a pound with the battery and tape included. The team was able to use an existing
model of this camcorder that was in the lab thus incurring no additional cost for imaging.
A Canon BP-2L12 battery pack is used with the camcorder to provide sufficient power to
the unit for the duration of it’s recording. The main drawback of the digital camcorders
is their reduced tape time, being only two hours when using an 80-minute tape in the LP
recording mode. For this reason, a timing circuit needs to be built which can trigger the
video camera to start recording during the ascent in order to have enough time to film the
descent. With an estimated flight time of three hours, the timing circuit needs to trigger
the video camera after one hour. After researching several timer options, including a
standard 555 timing circuit that proved to be difficult to set properly, a circuit is designed
that could be triggered by two standard digital kitchen timers. One digital timer is used
to trigger the power up switch on the camcorder while the other one triggers the
recording function. The timing circuit built is described below in further detail.
Canon Elura 50 digital camcorder and Canon BP-2L12 battery
Since there is not a reliable way to secure the cameras to the polystyrene walls of
the payload box and have them be removable, a mounting plate is made. The plate is
made of .25” thick acrylic plastic that was chosen for two reasons: it is easy to work with
and it does not act as a heat sink, absorbing all of the heat from the components mounted
to it. Fifty-five holes are drilled throughout the piece in order to reduce its overall weight
by over 80%. The mounting plate has a tight fit across the bottom of the inside of the box
that keeps the cameras securely located and stable during the flight.
Camera mounting plate
Timing circuit:
A timing circuit is used for the digital camcorder that utilizes two kitchen timers,
exploiting the fact that they are easy to program and they put out an audible output upon
the completion of their count down. One circuit is used to power up the device and the
other to activate the record function of the camcorder. For each of the two timers the
transistors are removed and the IC output is fed directly to its respective SCR. The SCR
is required since output of the timer is very short and not wide enough to trigger either
input on the video camera. Once the SCR is triggered, it allows current flow through the
optical isolator, thus closing the contact between the power and common inputs of the
video camera. A few resistors are placed in the circuit in order to protect the components
from excess current and possible damage. Once the contacts have been closed, they
remain closed until the 9 V battery used to power the circuit no longer supplies enough
current. To protect the fragile circuit and also to provide a mounting surface, the circuit is
potted inside a matchbox using a non-conductive epoxy.
Schematic of timing circuit
Timing circuit potted with in a matchbox with epoxy
Modified Kitchen Timers
Modifications required for the video camera are made in order to bypass both the
power and record switches. Each switch has a positive lead soldered to it, and they both
share a common ground.
Control chip from Canon Elura 50. Three wires were added to the video camera to
make the necessary connections; one wire to ground, 1 wire to the power switch, and
one wire to the record switch (on back side of board)
Small hole drilled through the camera casing allowing the entrance for the external
wiring to be fed in
Sensors and Data Loggers:
Temperature and pressure measurements are critical for any balloon launch in
order to calculate altitude and to assess the environmental conditions in both the upper
atmosphere and the payload box itself. The Launch PSU ’05 team uses a similar sensor
configuration from what was used in the Launch PSU ’04 payload. An Onset Computer
Hobo H8 four-channel logger is used to measure ambient temperature through a RTD
temperature probe plugged into one of the external channels on the logger. This probe is
inserted through the wall of the payload box in a small tube and the temperature it records
is used to calculate altitude.
To measure ambient pressure and internal temperature, a MadgeTech
PRTemp101 is used. The MadgeTech reads pressures to 0 psi in 0.002 psi increments
which is important for measuring the very low pressures encountered in the upper
atmosphere. A probe is thread through a small tube in the side of the box to the outside
in order to measure the ambient pressure. The MadgeTech is able to measure the internal
temperature of the box from the built-in temperature probe on the device.
Hobo H8 Data Logger and MadgeTech PRTemp101 Recorder
Strobe Light:
Since the balloon is launched in early dawn, a strobe light is added to SPOT-5 to
allow for visibility up to 2 miles away. The strobe light used is designed for emergency
situations and has a projected battery life of over 2 hours with continuous use. To prepare
the strobe light for the box, it’s battery housing is removed, leads are soldered directly to
the light and run to an internal battery pack inside the box. This allows for a slight weight
reduction in the light itself and also keeps the batteries warm through out the flight. The
strobe is controlled by one of the switches on the switchboard.
Strobe light mounted to the bottom of the box
Switch board and Wiring harness:
The small size of the payload box makes it nearly impossible to make power
connections to all of the onboard devices once they have been loaded. A switchboard is
created to simplify this process by centralizing the power triggers to all components
inside the box. This allows the onboard devices to be installed and connected to power
without being turned on until the box is ready to be sealed. Since all the components run
off of their own power sources, a removable wiring harness is also constructed. All of
the connections on the wiring harness are made with Molex ® 70066 2 and 3 position
connectors. These connectors are small, reliable and easy to use, although they require a
very expensive crimping tool for installation.
Switchboard and wiring harness
Exploded view of the final box assembly, less the lid assembly
A list of major components that make up SPOT-05
1. Module
2. 2 digital still cameras
3. 1 digital video camera
4. Camera mounting tray
5. Controlled heating system
6. Internal data logger
7. External data logger
8. Strobe light
9. GPS and Radio transmitter
10. Programmable timing circuitry
11. Internal wiring harness with switch board
12. 16 batteries of various sizes
All the components that reside inside the box minus the GPS/radio
Final box assembly, less the lid assembly
Lid assembly with antenna, GPS, and radio boxes
There is a specific order that components need to be assembled at launch time.
This is needed in order for everything to fit properly inside of the tight space.
Assembly sequence:
1. Set all camera settings (except intervelometers)
a. Leave display time on for 1 min longer on camera paralleling Video
2. Attach cameras on base plate
3. Insert base plate
4. Adjust all camera lenses (clean)
5. Add putty around ports
6. Insert battery pack
7. Set intervelometers on still cameras
8. Insert wiring harness
9. Plug in strobe and battery
10. Insert heating element
11. Insert timing circuit
12. Program Hobo
13. Program Madgetech
14. Set video timers
15. Insert Data loggers
16. Insert thermostat
17. Plug in switch board
18. Power up sequence
a. Start timers
b. Turn on heater
c. Turn on Strobe light
d. Activate timing circuit
e. Start cameras
f. Shut lid
19. Tape lid shut
20. Attach to balloon and keep fingers crossed!
Completed assembly ready for launch.
Appendix A: Suppliers
Balloon:
Raven Industries
Sulphur Springs Balloon Plant
186 County Road 3502
Sulphur Springs, TX 75482
Phone: (903) 885-0728
Fax: (903) 885-1032
Contact: Mike Smith, Aerospace Engineer
http://www.ravenind.com/RavenCorporate/eng_films/balloons_small.htm
Parachute:
Spherachutes
1912 31st Ave.
Greeley, CO 80634
Phone: (970) 352-4262
E-mail: [email protected]
Website: http://www.spherachutes.com
Filler Assembly:
PVC
HPS Pipe & Supply
598 Baseline
Cornelius, OR 97113
E-mail: [email protected]
Custom Hose
Associated Hose Products Inc.
4444 NE 148th Ave.
Portland, OR 97230
Phone: (503) 257-4673
Tank Fitting
Air Gas
341 SE Baseline St.
Hillsboro, OR 97123
Phone: (503) 640-3644
Hone
Baxter Auto Parts Inc.
1001 SE Tualatin Valley Hwy, Ste. A34
Hillsboro, OR 97123
Phone: (503) 547-0119
Box:
Invitrogen Corporation
1600 Faraday Ave
PO Box 6482
Carlsbad, CA 92008
Phone: 760-603-7200
Fax: 760-602-6500
http://www.invitrogen.com
Digital Still Cameras:
Beach Camera
http://www.beachcamera.com
GPS/ GPS Antenna:
GPS City
http://www.gpscity.com
TNC/Transmitter:
http://www.byonics.com/pockettracker/
Strobe:
Electrical Components for Timers/Heater Element:
Fry's Electronics
29400 SW Towncenter Loop West
Wilsonville, OR
503-570-6000
http://www.outpost.com
Appendix B: Costs
Appendix C: Calculations
Heater Power Capacity:
Power =
V2
R
Resistors used: 5 x 1 ohm, 5 ohms total
Voltage is 4 x 1.5 Volts C cell batteries in series, 6 Volts total
Power =
62
= 7.2W
5
The Current draw:
I R=P
I=
P
R
Using the values from above,
I=
7 .2
= 1.2amps
5
How long will it last with the given battery capacity of 8.3 amp hours and 1.2 amp draw?
Time =
8.3
= 6.9hrs
1.2
This is a rough approximation of how long the heater system will operate at a continuous
rate. The battery life is maybe to be significantly less due to the lower resistance of the
heating circuit and lower operating temperature. For this reason, the expected life of the
heater is planned to be of the value above.
Appendix D: FAA Regulations
CFR PART CFR PART 101 -- MOORED BALLOONS, KITES, and UNMANNED
ROCKETS AND UNMANNED FREE BALLOONS
Subpart A -- General
§101.1 Applicability:
(a) This part prescribes rules governing the operation in the United States, of the
following:
(4) Except as provided for in §101.7, any unmanned free balloon [1] that –
(i) Carries a payload package that weighs more than four pounds
and has a weight/size ratio of more than three ounces per square
inch on any surface of the package, determined by dividing the
total weight in ounces of the payload package by the area in
square inches of its smallest surface;
(ii) Carries a payload package that weighs more than six pounds;
(iii) Carries a payload, of two or more packages, that weighs more
than 12 pounds; or
(iv) Uses a rope or other device for suspension of the payload that
requires an impact force of more than 50 pounds to separate the
suspended payload from the balloon.[2]
§101.3 Waivers:
No person may conduct operations that require a deviation from this part except under a
certificate of waiver issued by the Administrator.
§101.5 Operations in prohibited or restricted areas:
No person may operate a moored balloon, kite, unmanned rocket, or unmanned free
balloon in a prohibited or restricted area unless he has permission from the using or
controlling agency, as appropriate.
§101.7 Hazardous operations:
(a) No person may operate any moored balloon, kite, unmanned rocket, or unmanned
free balloon in a manner that creates a hazard to other persons, or their property. [3]
(b) No person operating any moored balloon, kite, unmanned rocket, or unmanned free
balloon may allow an object to be dropped therefrom, if such action creates a hazard
to other persons or their property.
EOSS Annotations:
[1] Payload strings that don’t exceed any of these four limits are exempted from all other
FAR 101 provisions, except 101.7. EOSS reads “payload” to mean those parts of the
flight string that do the work of the mission, independent of how they get to altitude and
back down. Thus we do not include the weight of the balloon, parachute or cut-downs in
this tally; the latter are members of the “flight system”. Tracking beacons, although
arguably flight system components, are included in payload weight, however, since they
are critical to the payload recovery mission goal.
[2] This applies only to the load line between the balloon and parachute. “Impact
strength” is undefined, but should not be equated to the line’s rated tensile strength; a 50lb tensile line will break during launch. The intent of this limit is to ensure that the
balloon detaches in the event of collision with an aircraft. EOSS uses 250 lb. woven
nylon kite line, which did break at a knot during “post-burst chaos” on one flight.
[3] This is the dreaded “Catch 22” clause that the FAA may impose on those who have
gained its unfavorable attention. One cannot successfully argue that a payload string in
flight is totally free from all risks to others. However, taking all reasonable steps to
mitigate those risks, such as keeping the flight crews and controllers up to date on your
location and altitude and avoiding heavily populated areas, will garner the FAA’s respect
and cooperation.
[4] This subpart applies only to those payloads that are not exempt according to Section
101.1 (a) (4). However, it’s still advisable to adhere to as many of these requirements as
reasonably possible (Ibid).
Source: http://www.eoss.org/pubs/far_annotated.htm#_ftn2
Appendix E: Testing
*
Test results from STO-65
Test result from STO-85
Appendix F: Balloon Filling Procedure
Balloon Filling
-
Total Weight: 19.7 lb ~ 20 lb
o Payload: 6 lb
o Balloon: 13.7 lb
Total Lift: 21.7 lb ~ 22lb
o Payload & Balloon: 19.7 lb ~ 20 lb
o Positive Lift: +2 lb
Tare weights needed (mark the weight on the side of the bottle!!)
o 5-lb weight: 1
o 1-lb weight: 3
o ½-lb weight: 1
o ¼-lb weight: 1
** A person with constant vigilance needs to be ready to grab the snorkel and the bottom
of the balloon, in case it slips out of someone’s hands!!
PROCEDURE TO FILL BALLOON #1
** This is the Primary procedure – if it doesn’t work, use #2!!
1. Hook up balloon filling apparatus and check for leaks.
2. Wrap a towel of known weight around the balloon at 2/3 the distance up the
balloon.
3. Attach 5-lb weight to towel (tare weight), using twine.
4. Fill balloon until the 5-lb weight is just lifted off the ground. Allow all gas to exit
the snorkel, into the balloon. Make sure the snorkel is not pulling on the balloon
by allowing it to slack slightly.
5. Remove the 5-lb weight, attach the fish scale to the towel, and check the balloon
lift.
6. The amount of lift at this point is that of the balloon and whatever gas was in the
snorkel; subtract 5-lb from this lift value, and this is the lift from the gas in the
snorkel.
7. Remove the fish scale from the towel and attach 8-lbs, minus the lift from the
snorkel.
8. Continue filling the balloon until the ~8-lbs (or just under) is just lifted off of the
ground. Allow all gas to exit the snorkel, and give it a little slack.
9. Remove the tare weight and attach the fish scale. If the measured lift is lower
than 7 lbs, 13 oz (~7.75 lbs), repeat steps 6 – 8, or just add a little gas.
10. Re-check the lift with the scale. If the lift is ~8lbs (+/- 2 oz, or +/- 0.3 lbs) , make
sure all gas is removed from the snorkel, and tie-off the snorkel by folding it over
on itself several times and tying off with string (or twine). Remove the tare
weights and towel from the bottom of the balloon and attach the payload and extra
weights to make sure the balloon doesn’t float away.
PROCEDURE FOR FILLING THE BALLOON #2
** This is the back-up plan in case Procedure #1 doesn’t work!! (Note: Steps 1-3 are the
same.)
1. Hook up balloon filling apparatus and check for leaks.
2. Wrap a towel of known weight around the balloon at 2/3 the distance up the
balloon.
3. Attach 5-lb weight to towel (tare weight), using twine.
4. Fill balloon until the weight is just lifted off the ground. Hold snorkel securely so
it doesn’t leak (or escape!) and remove from filling device. Bind the end of the
snorkel by wrapping it on itself, creating a loop, and tie with a piece of cloth and
string, such that the cloth is between the string and snorkel so the string doesn’t
create any holes in the snorkel material.
5. Attach the fish scale to the loop in the snorkel – loosely hold the snorkel so that
it won’t float away, but also so you aren’t pulling down on it. The total lift is
5-lb plus the reading on the fish scale.
6. Add enough weight to the towel (bottom of the balloon) such that the total lift
(weight plus fish-scale reading) is at 8-lbs, or a little lower.
7. De-bind the snorkel and reattach it to the filling apparatus. Fill balloon until the
weight is just lifted off of the ground.
8. Repeat steps 4-6 until the total lift (tare weight PLUS fish scale reading) is ~8lbs
(+/- 2 oz, or +/- 0.3 lbs).
9. Remove the snorkel from the fill-apparatus and tie it off by folding it over on
itself several times, making sure no gas escapes, and tie-off with string or twine.
Remove the tare weights and towel from the bottom of the balloon, and attach the
payload and extra weight to ensure the balloon doesn’t fly away while waiting for
launch.
Appendix G: Contacts
Mark Weislogel, Faculty Advisor
[email protected]
Joshua Hatch , Senior Coordinator/GPS/Radio Operator
[email protected]
Andrew Craig
[email protected]
Jesse Hendrickson
[email protected]
Donovan Finnestad
[email protected]
Appendix H: Payload Bag Schematic
GOES HERE!