This paper presents a review of the references on solar sails, which implies that this subject is relevant and actively developed by various researchers from around the globe. It points out that an important role is played by various imperfections, which would affect the parameters of real solar sails compared to the ideal model.

The differential equilibrium equations of the blades of a heliogyro solar sail considering small deformations are written at the beginning of the article. The blade is loaded by light pressure and centrifugal forces, and is fixed at one end in the rotation axis while the other end is free. The differential equation for the blade deflection is obtained. This equation is solved in a statement that the reflection coefficient is independent on the mechanical stress. The deflection function has a simple analytical formulation. The differential equation for the transverse deflection of the solar sail blade is also solved analytically in the formulation of the linear dependence of the reflection coefficient on the tensile stress. The results obtained in both derivations are compared at the maximum amount of deflection of the blade of heliogyro solar sail. It is proved that the maximum difference in the magnitude of the deflection is achieved at tip section. An analytical expression for the relative change in the maximum deflection of the sail blades is given. The chart of this dependency is given for the blade of perspective solar sail with a length of 1000m and made from PET material, which is considered in the linear-elastic formulation.

To calculate the projection of the resultant vector of light pressure on the axis of rotation the hypothesis is introduced that the decrease of the reflection coefficient of the material exactly equals to the increase in the transmittance, and vice versa. Considering this hypothesis for PET material the proportionality factor is found, showing a decrease of the reflection coefficient with increasing tensile stress.

The expression for the infinitesimal light pressure force on the blades of the element of blade of a solar sail in the projection on the axis of rotation is given. This expression is numerically integrated by two formulations for the ideal and non-ideal solar sail. The numerical value characterizing the reduction of the projection of the main vector of the light pressure force for the non-ideal solar sail is obtained. By analyzing the references it is shown that the obtained difference in the light pressure is substantial and can lead to a change in ballistic performance of solar sails.