Attittude control

They're not talking about good & bad attitude as in mental states, but http://en.wikipedia.org/wiki/Attitude_dynamics_and_control.

JohnDG: You are wrong. Altitude control is needed spacecrafts to stop the astronauts attacking eachother. It controled with Valium Omnipom Lisergic-Acid and others.

The Wikipedia url cited by JohnDG gave the definition, but didn't really address the "how and why". They addressed part of the "how" - the sensing equipment, but not the equipment that generates the required forces to maintain or change attitude. The "why" is fairly easy to understand. The spacecraft has a mission. It could be lots of things, but many spacecraft are communications platforms, and the antennas need to point in a particular direction. If the spacecraft is pointed the wrong way, or tumbling, then the antennas will not be boresighted on the target antenna at the other end of the link. Incidentally, all spacecraft need to point their antennas at earth, because that is how they communicate, regardless of whether their main mission is communications or something else. Some satellites act as observers, of earth targets or outwards. For instance you have Hubble. Hubble is taking photographs of distant items far across the universe, while orbiting Earth. You can see its attitude must be very tightly controlled in order to get a sharp picture. Imagine you trying to get a good picture of something that requires a three second exposure while you are riding a merry-go-round. Now turn inwards - the Worldview satellite and others like it take those pictures for Google Earth. I have seen a very sharp picture of my home taken from hundreds or thousands of kilometers up, with the orbital velocity on the order of 18,000 mph. Finally consider Pioneer 10. This is the first man-made item to leave the solar system. It may not have left just yet, but it will, eventually. It was sending status signals back to earth from the orbit of Pluto, and beyond. And its entire power generation capability was 155 Watts at outset, and the COMM system was transmitting something like 5 Watts or less. It's a pretty good bet that the high gain dish was accurately aimed at Earth for those transmissions. So that is some of the "why". Here's the "how". As noted, the Wikipedia url cited by JohnDG explained how attitude is sensed, but didn't delve into how attitude is maintained or changed. There are two main ways of controlling attitude. One is with thrusters which expel mass. Newton's 3rd law of motion states that for each action there is an equal and opposite reaction. So if you want to turn in a particular direction, you expel something in the opposite direction. Clearly this method has its limitations - once you have expelled all the available thruster fuel, you lose control. So thrusters are usually reserved for not attitude control, but altitude control - to boost back into the original desired orbit when the orbit has decayed some. Another method of attitude control is reaction wheels. This is the gyroscope principle. A spinning gyroscope has torque, which exerts force in a given direction. If the gyroscope is at rest, and you apply power and spin it, then there will be a force in a particular direction, and that new force via Newton, will be opposed by an equal and opposite force, and that will tilt the spacecraft. The reaction wheel is driven by electrical power, typically from solar cells - a renewable source of attitude control that does not run out.

How is generally powered by hydrogen peroxide. What for is, "How would you like to ride all the way to Mars upside down?"

To put it in simple form.

if it is Attitude control ,it must be something to do with stoping the pilots from fighting each other over the controls//?May be ask a medical proffessional

If it is Altitude you mean than it is an instrument to indicate the distance the aircraft is from the sea level,and this will guide the pilot to stay in the proper required altitude during the flight.

think i was a bit hasty in my previous reply, JOHN DG has given the correct referance to answer your question