Space Grant Consortium - University of Wisconsin - Green Bay

Electronics and accessories
Altimeter. Per recommendation by Frank Nobile, an altimeter was purchased from Adept
Rocketry to be used in the dart stage of the rocket. At the time of purchase it was not decided
whether the parachute would be deployed at apogee or at 750 feet above ground. Hence, a model
was chosen with the options for dual deployment. Weighing in at only 26 grams, the ALTS2 is a
very bare minimum altimeter. It reports maximum altitude, but not accelerometry data. This is
acceptable because the only function really required by this device is the ability to deploy the
parachute at the proper time. The altimeter is connected to e-matches from Wildman Rocketry.
Black powder is then used as the propellant for ejection, as it is the generally accepted standard.
Locating beacon. Being able to track the rocket was an extremely important objective.
GPS systems would be ideal. However, they are also bulky and expensive, and if there is trouble
making contact with the satellites, they can be completely useless. An alternative to GPS is radio
tracking, similar to how one would track wildlife or hunting dogs. It works by having a very
small radio transmitter on the rocket that transmits a radio signal. Then a radio receiver listens to
that signal using a directional antenna. By waving the antenna in various directions, one can
easily tell where the signal is coming from and thus where the rocket is.
Only a few models could actually be found on the internet. The smallest and cheapest were
found at Adept Rocketry. Weighing in at only 14 grams and a receivable range of over one mile
on the ground, it was the obvious choice to go with. A directional antenna was also purchased
from Adept Rocketry to go with a receiver purchased from the Ham Radio Outlet. An important
note here is that to purchase this equipment, an FCC amateur radio license needed to be obtained.
This involved taking an FCC test and paying a small fee.
Booster parachute. A parachute was chosen from Public Missiles Ltd. that was 30 inches
in diameter. This parachute was chosen because there was already going to be an order placed at
PMI and it would save on shipping to order through them. The size was chose based on a target
falling weight of 1 Kg. Using their weight to parachute diameter chart PDF found here [2], the
smallest parachute that would still hold 1 Kg was chosen. Additional tests using RockSim
ensured that the rocket would not be falling at a speed greater than 20 feet per second.
To attach the parachute to the booster, an 11 foot section of 3/8” nylon tubular webbing was
used. This webbing was chosen because the stretch of it would decrease the stress on the booster
when the parachute opened up. The width of the webbing provides more strength than is really
needed, but this allows room for error in case part of the webbing is melted during the ejection
charge. The length of webbing was chosen to allow more stretch and also to prevent the webbing
from ripping a hole down the side of the body tubing. [2] A parachute “slider” was also rigged
up for the parachute to slow the opening of the parachute. The idea from this comes from BASE
jumping parachutes, which use a similar mechanism to prevent the parachute from opening too
quickly [3].
Dart parachute. This parachute was chosen in a similar fashion the booster’s parachute.
However, because PMI only carried an 18 drogue chute and not a normal chute, an order had to
be placed through Madcow Rocketry. This chute was of similar construction to the PMI one
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