Search Results

A Nutrient Delivery System (NDS) capable of working in microgravity is an essential component of growing plants in space. A substrate-based NDS is a conventional and mechanically simple way to grow plants in microgravity, especially when a nutrient impregnated substrate is used. A substrate moisture sensor is a key element of the control system needed to successfully grow plants in this type NDS. A heat pulse-type moisture sensor has been developed for use in microgravity that has the advantages of a simple, compact design and a low average power requirement. The heat pulse-type moisture sensor was developed to be used in the “Greenhouse 2” Experiment with the Russian plant growth unit, “Svet.” This experiment is part of the SpaceLab/Mir-1 mission which is being conducted on Mir in 1995 and 1996. The design of the sensor allows installation of the sensors into the Svet root module aboard Mir.

The Greenhouse-2 experiment was conducted on the Mir Space Station as a part of the SpaceLab-Mir-1 (SLM-1) mission. The Russian-Bulgarian plant growth unit (Svet), used in the 1990 Greenhouse-1 Mir Space Station experiment, was refurbished for use in this experiment. The Svet root module was loaded with the same type of substrate (Balkanine) that was used in the 1990 experiment except that the grain size was reduced and packing density increased. Heat pulse type moisture sensors developed jointly by Russian and American scientists provided additional monitoring of water distribution inside each module. These sensors determined moisture movement and distribution in real time, thus permitting the crew support team to monitor the moisture level in the root module and estimate the water delivery needs of the root module. The water relations results obtained during the Greenhouse-2 experiment are discussed in this paper.