Kidneys are a filter system. The main job of the kidneys is to remove waste from the blood and return the cleaned blood back to the body. Each minute about one litre of blood ï­ one-fifth of all the blood pumped by the heart - enters the kidneys through the renal arteries.
The volume of helium in the balloon has been estimated as being able to lift a total load, including the balloon material and the structure beneath it, of 65 pounds (29 kg) at sea level and 48 pounds (22 kg) at 8,000 feet (2,400 m).
A typical balloon system - envelope, gondola, fuel tanks, and 40 gallons of fuel - will weigh about 600 pounds, deflated on the ground. In the air, the complete system, including the weight of the air inside the envelope, will weigh about 2 Â½ tons.