Inflatable structures are large cold-air structures that people (usually children) can bounce on for recreation. They have been marketed such names as Moon Bounce, Astrojump, Moonwalk, Bounce house, SpaceWalk, in the US, bouncy castle or inflatable castle in Ireland, the UK and parts of Australia, and as jumping castles in Australia, New Zealand, Canada and South Africa. They are often in the shape of a castle. The walls and floor are soft.

The inflatable structure was designed in 1959 by John Scurlock who was experimenting with inflatable covers for tennis courts when he noticed his employees enjoyed jumping on the covers. [1] He started the Space Walk company to market them for children and called them Space Walks. He started out with a large air mattress and in 1967 added walls.

Inflatable structures were also designed by university students in England around 1961 for a fundraising event.[2]

The surfaces are typically composed of thick, strong PVC or vinyl and nylon, and the castle is inflated using an electric or petrol-powered blower. The principle is one of constant leakage, meaning small punctures are not a problem - a medium-size "bouncy castle" requires a fan with a mechanical output of about two horsepower (consuming around 2 kW electrical power, allowing for the efficiency of the motor).

The term "moonwalk" has evolved as the generic term for enclosed inflatable trampolines in the US. Modern moonwalks in the US are typically supported by inflatable columns and enclosed with netting. The netting allows for supervision as adults can see in from all sides.

UK and Australian bouncy castles have specifications calling for fully inflated walls on 3 sides with an open front and foam "crash mats" to catch children who may jump or fall out of the structure.

Inflatables are rented for functions, school and church festivals and village fetes. Although they are aimed at children, adult castles can be hired in the UK. Because of liability concerns moonwalks are rarely rented to adults in the US. They are often used to wrestle or bounce.

The growth in popularity of moonwalks has led to an inflatable amusement industry which includes inflatable slides, obstacle courses, games, and more. Inflatables are ideal for portable amusements because they are easy to transport and store.