Sooketoo Bhuta, Jeff Bramel, Jay Kho, Mitesh Patel, Vivek Ray, and Marc Sulfridge
9 January 1996
The purpose of this project will be to design, build, and fly a dirigible which utilizes a dual control system consisting of a traditional radio link and a Global Positioning System (GPS) navigational system. The intent of the latter control mechanism is to allow the blimp to travel and maneuver over large distances, independently of operator input from the radio control system. Thus, the blimp should be self-navigable to a large extent, within certain practical limitations. To facilitate practical applications of the blimp, its design will provide for lifting capacity and power in excess of that required for basic operation, thereby allowing the vessel to carry payloads aloft. It will not, however, be an immediate focus to design or construct beyond a preliminary stage any payload for the blimp. (See "Enhancements" below.) Ideally, the blimp will be able to operate aloft for continuous periods of time on the order of several hours, but this specification is contingent upon feasibility.
A blimp was chosen over other airborne craft because it was felt that the design and implementation of the former would be simple enough to be tractable by a small group of students working with a limited budget for a short period of time. A blimp has the potential to achieve many of the same end uses as more complicated systems (such as helicopters or fixed-wing aircraft), but has the advantage of being less complex at a fundamental level. Toward that end, system elements should be kept simple and straightforward, and the total number of subsystems should be kept to a minimum. Although such an approach may constrain the ultimate functionality of the blimp, it will ensure that the project does not stagnate because of insurmountable obstacles.
A key area of application for a GPS self-navigated aircraft is that of remote sensing and investigation. As an example, a blimp outfitted with a camera could be programmed to visit geographical locations and take aerial photographs, perhaps at a cost far less than that of manned aircraft. Such a system could be beneficial in fields such as road traffic monitoring, sports event monitoring, emergency response assistance, and terrain mapping. The low cost of using a radio-controlled blimp for such applications should be emphasized.
Other applications include meteorological data collection, remote sensing along programmed courses, and small payload retrieval and delivery.
Although detailed plans have yet to be formulated, the goals outlined above suggest certain guidelines in designing such a system. It is thought that helium will be used as the source of floatation, since it is less dangerous than hydrogen and far lighter and more practical than hot air. Initial work will involve specification of desired functional attributes, such as payload capacity, top speed, and range. After such attributes have been specified, the designers will calculate the total weight of the system, and thereby determine the necessary size of the blimp. In planning the blimp's size, allowances should be made for the weight of the airtight bladder and payload, including a generous error margin.
Two key elements of the blimp must be carefully considered: The mechanical maneuvering system and the electronic control system. If possible, a single-engine design will be used. The engine will provide thrust for maneuvering, and should also provide a source of electricity for on-board electronics, since batteries are quite heavy. This approach will prove most fruitful when used in conjunction with a clutch system to engage and disengage the thrust and steering propellers, thereby allowing a single engine to provide power to all mechanical systems. It is thought that a small, high-speed engine such as is used on many model aircraft will provide the necessary power in a relatively lightweight package. It is hoped that linking this engine to a high-speed generator or alternator will provide all necessary electricity with a minimal weight penalty; nevertheless, a small backup battery should be included to provide short term electricity in emergency situations such as engine failure.
The electronics will consist of two key sub-components: the radio control system and the GPS self-navigation system. The radio control system will consist of a multiple channel one-way link between the ground and the blimp. Some channels of this system will be proportional, while others will be binary. A receiver on board the blimp will be responsible for interpreting ground signals and activating servo motors and solenoids on the blimp as necessary to control the blimp's activities. In the absence of radio contact with the ground, or if given the proper signals by the ground controller, the blimp should revert to a preprogrammed GPS system. This system, to be implemented in the long term, will center around an onboard computer which will compare preprogrammed positional and temporal data points with actual data from the GPS receiver and calculate maneuvers as necessary. A key future enhancement to this component of the system will be the addition of a radio data link to allow live updating of GPS-based flight plans. For practical and safety reasons, the blimp operator should always be able to override GPS control via radio.
The blimp will be either nonrigid or partially rigidified in key areas such as the nose and payload attachment points. The main body of the blimp will consist of two layers; an inner bladder which can contain the helium without leaks, and an outer shell to constrain the bladder and provide strength. The outer shell of the blimp should be inelastic, strong enough to provide structural support at operating pressures, and tough enough to resist incidental abrasions from ground handling and minor mishaps. The blimp should be designed to be slightly heavier than neutrally buoyant, so that in the event of an engine failure it will return to the ground. However, it may be beneficial to incorporate an air bladder in addition to the primary helium bladder, thereby allowing ballasting and trimming without loss of skin pressure. An ideal operating pressure will have to be determined.
The following is a tentative outline of the project schedule:
The personnel working on this project shall consist of the following members. Each member may be contacted via the e-mail or phone information given, and each desires to obtain the amount of credit indicated:
| Name |
E-Mail |
Phone |
Desired Credit |
| Sooketoo Bhuta |
sbhuta@ugcs |
x1401 |
9 units |
| Jeff Bramel |
bramel@espresso |
x1433 |
12 units |
| Jay Kho |
jaykho@cco |
x1135 |
(see below) |
| Mitesh Patel |
hsetim@ugcs |
x1428 |
9 units |
| Vivek Ray |
vivekray@cco |
x1390 |
6 units |
| Marc Sulfridge |
marcsulf@cco |
x1135 |
12 units |
Although Jay Kho will not be formally registered for the course, he will serve in an advisory capacity, especially for the electronic subsystems.
This provides a total time budget of 48 hours per week, broken down by credit desired. Over the course of ten weeks, this indicates that approximately 480 man-hours of time will be devoted to this project.