Evaluation of planting surfaces for crop production in microgravity.

In microgravity, plants can be cultivated on curvilinear domed (convex) surfaces, e.g. cylindrical, spherical, and thoroidal, with light sources arrayed evenly along a concave surface above the crop surface. In this case, the plant stems align along the normals to the crop surface with crowns moving apart as plants grow owing to phototropic reactions. Analyses showed that, compared with crops raised on flat surfaces, the curvilinear crop surfaces carry the promise of significantly increasing the specific productivity of crops both per unit internal growth chamber volume and per unit energy required by plants. The highest effectiveness of volume and power utilization was demonstrated by the spherical crop surface and the least by the cylindrical one. The thoroidal crop surface has an effectiveness between the two. The cylindrical surface of the laboratory model, PHYTOCYCLE, had a specific productivity of 30 g of fresh Pekinese cabbage biomass per kWh which is 28% higher than what has been harvested from a flat crop surface under comparable conditions. PHYTOCYCLE plant growing chamber volume was 40% less than the volume of a flat crop surface growing chamber.