MadSci Network: Engineering

Re: how could I build a rocket stabalizing gimbal

Date: Fri Apr 27 14:02:01 2001
Posted By: David Ellis, Researcher, NASA Lewis Research Center
Area of science: Engineering
ID: 985898902.Eg

I'm not sure if you really are referring to a gimbal system or not.

On large rockets such as the Space Shuttle, gimbals are used to tilt the rocket engines and provide control during flight. A fuller description can be found under Rocket Controls. The gimballing action is computer controlled and allow changes in two directions - yaw and pitch. They do not affect the third direction on a rocket, roll. You can also see the gimbals of the Space Shuttle just before liftoff when it runs through a check of the gimbal hydraulics and controls during the final seconds of the countdown.

The gimbals used in rockets most often use hydraulic systems to adjust the direction of the engine. They have to be able to adjust a heavy rocket engine (hundreds to thousands of pounds) that is producing hundreds to hundreds of thousands of pounds of thrust.

I am presuming your interest is more in model rockets such as those produced by Estes Rockets and sold at local hobby stores. To put a gimbal on one of these would be difficult and most likely impossible. You would need three things at a minimum - a gimbal mechanism, sensors and a control system. The control mechanism would have to have a computer of some type to control the gimbals during the flight. The sensors would be things such as gyroscopes to monitor the flight of the rocket and instruments to provide feedback when changes are made to both the gimbals and the flight path. These could potentially be placed into a hollow nose cone of the larger rockets. Weight is a major problem since standard model rocket engines do not produce extremely large thrusts.

The gimbal mechanism itself represents the hardest challenge. Model rockets typically have a rigid body into which the rocket engine is glued. Gimbals require a movable engine mount. So the entire engine mount will need to be redesigned. For something this size using some sort of elastic material between the engine mount and the body may provide sufficient flexibility for small motions.

However, once the engine can move, a means for moving it and determining how much it has moved and in which direction is still required. Hydraulics are far too heavy and large. I doubt any electric motor is small enough or light enough, but they are one of the few workable possibilities. Simple methods such as rubber bands lack the strength and feedback capabilites needed to control the flight.

In short, there is very ikely no good way to control this small of a rocket. However, short of a major design effort, the possibility of a viable mechanism cannot be completely ruled out.

There are larger rockets being made and flown by amateurs. They are based on sounding rockets, high altitude rockets that can go as far as the edge of space. HobbySpace has quite a bit of information on these rockets and model rocketry in general. These larger rockets tend to be the creation of very serious amateurs or rocketry clubs. They are not launched in people's backyards but at places like White Sands Missle Range in New Mexico. They require permits from the Federal Aviation Administration for flights. In short, they are a very serious endeavors. The major advantage is with the extra size and thrust capability gimbal systems become possible.

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