Isogrid

An isogrid is a structure which has a sheet of material (usually metal) with integral metal stiffeners in a triangular pattern on one side. Isogrids are fabricated by machining material away from a thick sheet or plate of metal, leaving a continuous flat surface on one side and a series of triangular pockets with thicker integral stiffeners between the pockets on the other.

The isogrid structure is effective as a self-stiffened structure where both overall stiffness and strength are important, such as in space launch vehicle rocket structures where the bottom stages of a rocket have to support the full weight of upper stages and payloads.

The name "isogrid" is derived from isotropic - where a material has equal properties measured in any direction, and grid, referring to the sheet and stiffeners structure. The triangular pattern used in isogrids gives a more even approximation of isotropic behavior than other simple shapes.

Some space launch vehicles which use isogrid structures include:
* Delta families
* Atlas-5 rocket

The Space Shuttle lightweight and superlightweight external tanks utilize an integrally machined stringer system which is not a true isogrid, though it is somewhat similar. Since the structure is arranged at right angles it is considered an "orthogrid" rather than an isogrid with triangular stiffeners of an isogrid.

External links

* [http://femci.gsfc.nasa.gov/Isogrid/ Isogrid Plate Modeling, Dr Wiliam Case, 1997]
* [http://femci.gsfc.nasa.gov/Isogrid/NASA-CR-124075_Isogrid_Design.pdf Isogrid Design Handbook, NASA CR-124075, McDonnell Douglas, 1973]