Introduction
The decent of our balloon packages is one of the very few things that we have little control over. In the past we have only been concerned with using a parachute that slows the decent enough that our hardware is not damaged by the landing. The current design has no control in direction and is very susceptible to the direction of the wind. This can make for some very long searches at the end of the day. We've decided that it is time to increase our control over the decent of our packages. We plan on doing this by researching directional parachutes and mechanical ways of controlling them. We will be scaling down a directional parachute for our small weight requirement and designing a gear box to control the lead lines. This semester will culminate in a demonstration of our mechanical system during a moored launch. Next semester we will begin exploring control systems from an electrical engineering standpoint.
Background Information
One main problem of using a high altitude opening parachute is that, even with sophisticated computer models, the drop-zone is so large we spent a great deal of time searching for the package. To better control where a package will land the military has developed a wide range of ram-air parachute packages guided by GPS and radio to deliver cargo to an exact location. For example the marines Sherpa TM/MC GPS guided parachutes can land within 70 meters of their intended target point after being dropped at 25,000 feet and 15 miles away.
Purpose
The purpose of the the CPT project this semester is to prove whether or not the proposed system is feasible. Ultimately the project is to help make recovery of the balloon easier. The CPT project will create a system that will show if greater control of the path that the payload takes during its decent is possible. With greater control of the path that the payload takes we will be able to guide the payload to an area that is easier to reach, helping to increase the likelihood of recovering the capsule.
Design
The design uses a basic ram-air parafoil to give the package direction during descent. Air trapped in the parachute gives it shape. The shape forces the air to pass through the cells from the front of the parachute to the back (see pictures). This is what makes it go forward. To turn, control lines are attached to the cells on each end of the parachute in such a way that when the control line is pulled the cells on the end collapse (see #54a in drawing). This causes an imbalance in lift and therefore the entire parachute banks. As a precaution, one control line could be set to real in automatically in case of a control systems failure in which case the parachute would simply spiral down and be pushed entirely by the wind as our current parachute is. The control box (#100 ) will be separate from any other capsules and attached directly to the parachute. A harness (#80) will be attached below the control box that will fit most packages.
Fall 2008
People Involved
Outcomes/Goals
By the end of the semester we plan to complete the following:
- Design a 1/10th scale revision
- Construct model
- Test design
- Design a 1/2 th scale revision
- Construct model
- Begin flitght bevaiour testing
- Devise Test methods and regiment
Timeline
Under Revision
here is the schedule to be revised
Parachute
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We have decided to revise the current 1/10th scaled, choosing to go with a more rectangular parafoil with open bottom cells for reduced complexity. If cell bottoms prove necessary in testing they can be easily added later. If the 1/10th scale model proves adequate we will move on and build a 1/2 scale model.
Testing
Once the parachute has been designed numeous tests will be done in order to develop a behavioral model. These tests will involve shortening the lead lines by a specific amount and observing the severity of the turn produced. Initial tests will be carried out by dropping it from a small height. We plan on developing a method for easily repeating the test. Currently we are working with an idea of a test system similar to a moored launch. Using a balloon thats tied to the ground to lift the test payload to the desired altitude of 100 ~ 200 ft.
