Counter Spin: Problem Definition & Requirements

Problem Definition

In November 2010 several payloads were sent up to 85,000 ft by a standard weather balloon. In the picture below you can see the layout of the payloads on the weather balloon.

Payload Arrangement and Balloon Lanuch

This picture shows a balloon launch how the payloads are arranged.

The payloads and weather balloon are connected with rope. The rope is not rigid and twists very easily. As the balloon travels upward, it encounters atmospheric winds. The atmospheric winds blow on the payload imparting a moment about the rope that causes the payload to spin about the vertical axis.

The picture to the left shows a launch. From the picture you can get an idea of how the balloon and its payloads are connected.

The video below shows the stability problem in action.

The goal of this project is to, within the constraints of a payload, create a single axis attitude control system that will make a video of the flight worth watching.

Flight Profile — About the Weather Balloons

The weather balloon pictures above is attached by rope to several payloads. Each payload is a contained structure weighing less than 2 lbs [.9 kg]. The payloads on the top and bottom contain GPS sensors and RF transmitters which are used to track the balloon through it’s flight.

The weather balloon is filled to a capacity that determines its flight profile. The balloon reaches a certain altitude at which the atmospheric pressure decreases enough to cause the balloon to expand and pop. The gas used by the balloon is Helium and typically it can lift 20 lbs to altitudes up to 125,000 ft [38 km].

Once the balloon pops, despite its parachute, it falls like a rock through the less dense layers of the atmosphere. Once the popped balloon reaches a lower altitude its parachute catches and its payloads safely land (hopefully :).

Counter Spin Requirements

1. Mounting

The payloads have a bronze 10 mm lamp rod going through them with an attachment point on each end for ropes to attach. Project Counter Spin must use the same mounting method to attach to the ropes.

2. Weight

The aggregate weight of the entire payload system including the mounting rods must not exceed 2.25 lbs and preferably weigh less than 2.00 lbs.

3. Control System

The control system shall provide one dimensional attitude control for a video camera mounted on or within the payload. The camera footage shall be bearable to watch and preferably beautiful.

4. Other Sensors

The payload shall also contain an accelerometer, pressure sensor, and temperature sensor. Preferably the payload shall contain a solar cell and outside temperature sensor. The sensors shall be used to collect and record their data for post processing.

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