Mass budget: 1kg max, with a target weight of 0.5kg
The mass budget is a balance of what is achievable and what is a safe weight to have falling to the
ground bearing in mind that, although highly unlikely to land anywhere other than in a rural location,
we do not wish to cause any damage or harm to people or their property.
Of primary importance is our ability to recover the payload and as a consequence of this we have included
two tracking devices in the payload. After extensive research, we chose all our components based on
their performance, weight and price bearing in mind how large a balloon we could afford and how much they
can lift.
When it came to price however, we found that achieving all of
our aims was going to be extremely
difficult within
budget. Fortunately, we managed to secure the generous support
of
a number of companies who could supply the components we desired.
Details of our components and
where they can be purchased are
listed below. Please also visit our
sponsors page to find links to
their websites.
This sign (below) is attached to the top of the payload incase it is
found by someone before us. This is
particularly important should
our tracking devices fail; we should eventually get it back.
Tracking
Xexun TR102-2:
We chose this as our primary tracking device due to a number of factors; weight, size, price, high
accuracy positioning and most importantly, it transmits altitude data rather than just longitude and latitude.
The reason we wanted altitude data in the tracking data is so that when we receive transmissions we
will know if it is still descending or if it has reached the ground.
The Xexun TR102-2 was purchased from http://extrahomesecurity.com
iPhone 3 with ViewRanger app:
Our back-up tracking device is an iPhone 3 generously donated to the project by a member of staff
in the department which will be running the ViewRanger app.
The ViewRanger app also transmits altitude data but also stores position data when out of signal
range. The app is available for iPhone, Android and Symbian smartphones.
Position Logging
Garmin eTrex H:
The most important feature for a position logger in this project is that it continues to log through the
entire flight i.e. to the maximum flight altitude (>30km). It is quite rare for GPS devices to operate at
altitudes >18km due to limits imposed on civilian GPS use. This device is confirmed to work
above this altitude by other users and Garmin directly.
The Garmin eTrex H was purchased from http://www.amazon.co.uk
Temperature Logging
Lascar EL-USB-TC:
We chose this temperature logger because it fits our needs perfectly, weighing approximately 70g and
costing significantly less than other temperature loggers capable of recording temperatures as low as
-200C (-328F).
The EL-USB-TC data logger meets our temperature data acquisition aims and was provided
by
DATAQ Intruments.
Pressure logging
MSR145:
The MSR145 is one of the few pressure data loggers on the market that is capable of measuring
pressures as low as our payload will experience. This capability, and its small size and light weight
make it the perfect component for our project.
The pressure logger was provided by MSR: http://www.msr.ch/en/
Acceleration logging
MSR145:
The MSR145 is also able to measure tri-axial acceleration which we
hope to use, in combination with
the flight footage, to identify
when the payload reaches the stratosphere. At this point there should
be
very little wind (and turbulence) and so acceleration readings
should become negligible.
Humidity Logging
Lascar EL-USB-2:
We chose this humidity data logger because of its small size, light weight, low price and, primarily,
because it can make readings down to 0%RH.
The Lascar EL-USB-TC humidity data logger was provided by Lascar Electronics:
http://www.lascarelectronics.com/
Imaging
Tachyon XC HD Head Cam:
One of our aims was to achieve high definition footage of the curvature or the Earth from near space.
With the Tachyon XC HD we will achieve this.
Important features of this camera with respect to this project are a 6 hour battery life, light weight and
a resolution of 1280 x 720 recording at 30fps.
The head cam was provided by Tachyon XC: http://www.tachyoninc.com
NB. This can be purchased in the UK at: http://www.amazon.co.uk
Canon PowerShot A430:
An important aim for us is to get an undistorted image of the curvature of the Earth. Due to the nature
of video cameras, the edge of images can be distorted so we will include a basic Canon camera
to take pictures at regular intervals to achieve undistorted images.
The standard firmware on a camera such as this is not capable of doing this, so we have loaded
CHDK firmware onto the camera to facilitate this.
Balloon
Two 1600g Hwoyee meteorological balloons:
Hwoyee meteorological balloons are high-quality meteorological balloons, ideal for near space balloon
flights and so were a natural choice.
The size of the balloon required is defined by the weight of the payload; the heavier the payload, the larger
the balloon needed. We had to carefully balance the weight of our payload specification so that
we could afford the necessary balloons for two separate flights.
The balloon was supplied by Random Engineering: http://randomsolutions.co.uk
Parachute
4ft rocket man high altitude payload recovery parachute:
The weight of the payload defined the minimum size of parachute we require for a safe final descent
rate. This specific parachute was chosen because, unlike most parachutes (primarily designed for rocket
flights), it has a loop sewn into the apex of the chute to attach the balloon to.
The parachute was purchased from http://www.the-rocketman.com/
Miscellaneous
Blinking LED's:
To help us recover the payload, should it get dark before it is found, we decided to get four small magnetic
LED buttons to go on the outside of the payload. They are small, lightweight and have sufficient battery life.
The LED's were purchased from http://blinkylights.co.uk
Jaffa Tape:
We want the payload to be brightly coloured to help us find it but also to be highly visible, should it come
down in a less than ideal location. Wrapping the payload in Gaffer tape is ideal for waterproofing the foam
and adding strength to the payload. We therefore decided to use Jaffa Tape since it combines these attributes.
Buzzer:
Another way to help us find the payload is to include a buzzer. We bought a simple 12V buzzer and 9V battery from
Maplin.
Hand warmers & Cord:
To help maintain the internal temperature of the payload at a level suitable for the electronics, hand warmers
are the obvious solution. NB: After testing we decided that the components in our highly insulated payload
generate enough heat to maintain the internal temperature so we left out the hand warmers.
The hand warmers and cord were supplied by Random Engineering: http://randomsolutions.co.uk
