`=> text(Hot air balloon)` is an oldest type of flying machine. It has an envelope that holds heated air and, most often, a gondola or a wicker basket underneath it which carries passengers. Hot air is lighter than cold which lifts the balloon.

`=> text(Gas balloon)` is filled with a gas that is lighter than air - helium or hydrogen. Different balloons can be gas balloons, and this type has a lot of subtypes.

`=> text(Cluster balloons)` are clusters of helium-inflated rubber balloons which also can have gondola or a harness that carries a pilot. Cluster balloons are controlled in flight by jettisoning or deflating balloons or by jettisoning the ballast.

`=> text(Hopper balloon)` (or just Hopper) is a small, one-person hot air balloon, very similar to standard hot air balloons but with one seat or a harness. Because of their size, their flights last only 1 to 1.5 hours.

`=> text(Airship or dirigible)` is a type of a lighter-than-air steerable balloon that uses engines to move through the air. They can have rigid, semi-rigid and non-rigid bodies.

`=> text(Toy balloon)` is a small balloon filled with air or helium used for child play, party decoration, and advertising. These balloons are made of rubber, latex or foil and in many colors.

`=> text(Balloon helicopter)` is a type of a toy balloon that has a plastic propeller. This propeller is hollow and leads air through each propeller blade which makes propeller rotate.

`=> text(Water balloon)` is a toy balloon filled with water and used as a projectile in play fights.

`=> text(Solar balloon)` is a balloon, usually made out of material that is light and black or dark balloon material, that gains buoyancy when the air inside is heated by the sun's radiation.

`=> text(Fire balloon)` was a type of balloon used by Japan during World War II. It was a hydrogen balloon which carried bombs.

`=> text(Research balloons)` are balloons that are used in scientific research. They carry instruments that do meteorological, atmospheric, astronomic, and military research and are usually unmanned. Some of them were even used on other planets (Vega 1 and Vega 2 on Venus in 1984).

`=> text(Balloon rocket)` is a long and narrow toy balloon used to demonstrate physical principles and the functioning of a rocket.

`=> text(Barrage balloon)` or a blimp, is a non-rigid balloon tethered with metal cables, used to defend against aircraft attacks making the approach of airplanes more difficult.

`=> text(Observation balloon)` were usually hot air balloons or blimps with a gondola that were used for intelligence gathering and artillery spotting.

`=> text(Ceiling balloon)` is a type of meteorological balloon that is used to determine the height of the base of clouds above ground level. They are filled with gas, and its ascent rate is known, so the height of clouds is determined according to the time the balloon needs until it reaches the cloud.

`=> text(Balloon catheter)` is a balloon used in medicine. It consists of a soft catheter and a small inflatable balloon at its end. During a catheterization procedure balloon helps passage within the body.

`=>` Balloons are also inserted into the esophagus, stomach or uterus, and inflated to alleviate or stop the refractory bleeding.

`=>` Angioplasty is a surgical procedure in which very small balloons are inserted into blocked or partially blocked blood vessels near the heart. Balloon, placed like that, is inflated to remove or compress arterial plaque.

`=>` Some balloons are used as decoys during the war. They are shaped like tanks or some other real item of military equipment, and its purpose is to deceive the enemy.

Hot air balloons are an ingenious application of basic scientific principles.

The basis of how the balloon works is that warmer air rises in cooler air. This is because hot air is lighter than cool air as it has less mass per unit of volume. Mass can be defined by the measure of how much matter something contains.

The actual balloon (called an envelope) has to be so large as it takes such a large amount of heated air to lift it off the ground.

A hot air balloon is made up of 3 main parts:

`text(The Envelope)` - The actual fabric balloon which holds the air
`text(The Burner)` - The unit which propels the heat up inside the envelope
`text(The Basket)` - Where the passengers and pilot stand

The burner uses propane gas to heat up the air in the envelope to move the balloon off the ground and into the air. The pilot must keep firing the burner at regular intervals throughout the flight to ensure that the balloon continues to be stable. Naturally, the hot air will not escape from the hole at the very bottom of the envelope as firstly, hot air rises and secondly, the buoyancy keeps it moving up.

The controls for piloting a balloon are actually extremely simple.

`text(To move the balloon upwards -)` the pilot opens up the propane valve which lets the propane flow to the burner which in turn fires the flame up into the envelope. Works in much the same way as a gas grill, the more you open the valve, the bigger the flame to heat the air, the faster the balloon rises.

`text(To move the balloon downwards -)` the 'Parachute Valve' at the very top of the balloon is what is used to bring the balloon down towards the ground. It is essentially a circle of fabric cut out of the top of the envelope which is controlled by a long chord which runs down through the middle of the envelope to the basket. If the pilot wants to bring the balloon down he simply pulls on the chord which will open the valve, letting hot air escape, decreasing the inner air temperature. This cooling of air causes the balloon to slow its ascent.