In this thesis the use of thin foil conical profile X-ray mirrors for high energy, large aperture, and lightweight telescopes is investigated. The telescope performance is studied using analytical solutions and ray tracing simulations. Expressions for the number of mirrors in a module, the collecting area, the efficiency of aperture utilisation, and the resolution are calculated for on-axis sources. For off-axis sources ray tracing is used and expressions to describe the performance are derived empirically. The sensitivity and effect of singly reflected rays on the image are also investigated, and the comparison is made with Wolter (I) profile optics. A technique for the production of super-smooth surfaces using a layer of acrylic lacquer is described. Several materials have been coated using this method to assess their suitability as potential mirror substrates. To quantitatively assess the quality of both substrate and lacquer finishes a program of X-ray scattering measurements has been carried out. Several different types of surfaces have been examined both before and after lacquer coating. Particular attention has been payed to the ability of the lacquer to remove surface features of different spatial wavelengths. An epoxy replicated test flat is also examined which provides an interesting comparison with the lacquer coating technique for the production of thin X-ray mirrors. As a consequence of the wide range of materials examined it has been possible to compare most of the different techniques for producing thin X-ray mirrors. There is no one solution for all applications and thin foil mirrors are indeed a competitive technology.