The invention provides a heat shrinkable polyester film which has (1) a hot-water heat shrinkage of not less than 55% and not more than 90% in a main shrinking direction of the film when dipped in hot water at 98 C.; (2) a hot-water heat shrinkage of not less than 5% and not more than 12% in a direction orthogonal to the main shrinking direction of the film when dipped in hot water at 98 C.; (3) a difference in specific heat capacity C.sub.p between at a lower and a higher temperature than Tg of not less than 0.1 J/(g.Math. C.) and not more than 0.7 J/(g.Math. C.) when a reverse heat flow is measured with a temperature modulated DSC; and (4) a tensile breaking strength of not less than 70 MPa and not more than 150 MPa in the direction orthogonal to the main shrinking direction of the film.

A deployable structure includes a hydride material to be converted into hydrogen gas; and a sheet material encapsulating the hydride material; wherein the sheet material is to be plastically deformed by the hydrogen gas to have an expanded structure. A method of manufacturing a deployable structure includes: forming a sheet material comprising an outer shell structure and a hollow interior; placing a hydride material capable of being converted into hydrogen gas into the hollow interior; sealing the outer shell structure; and converting and releasing the hydrogen gas to expand and plastically deform the sheet material.