Passive Porous Tube Nutrient Delivery System

PONDS was developed as a water/nutrient delivery system for the Vegetable Production System, called VEGGIE, on the International Space Station (ISS). PONDS uses an innovative wicking material to passively link a water/nutrient reservoir to a plant cylinder. The system enables higher germination rates and improved growth conditions compared to the VEGGIE water/nutrient delivery system currently used on the ISS. PONDs consists of two primary components: a water/nutrient reservoir (Figure 1), and a detachable plant cylinder containing growth substrate and wicking material (Figure 2). The reservoir includes a viewing window that allows the user to observe and record water-use data. The plant cylinder, which screws into the reservoir system, is made from commercial-off-the-shelf materials and fittings. Both the reservoir and plant cylinder include oxygen-permeable windows to enhance aeration to the root zone. Water is delivered from the reservoir to the substrate contained within the plant cylinder via the wicking material inserted into the growth substrate. The wicking material is intrinsically hydrophilic, providing improved capacity compared to the system previously used with VEGGIE. As a result, PONDS can continuously supply water to the root zone within the plant cylinder on demand.

The Surface-Adhering BioReactor (SABR) is a novel microbial cell cultivation platform that mimics the way vascular plants use transpiration to deliver nutrients to their cells. In this biomimetic platform, microbial cells are cultivated as immobilized cells on a porous substrate where transpiration is used to passively deliver water and nutrients as well as harvest and concentrate secreted biomolecules by the microbial cells. The SABR transports nutrients to microorganisms without using a pump. Instead, evaporation and the cohesive property of water are exploited to pull the nutrient medium through the device, with a high degree of control, on an as needed basis. It eliminates the hydrodynamic shear stress on the cells and decreases the working volume of water needed for cultivation by a factor of 25 compared to planktonic bioreactors. Furthermore, the transpiration mechanism allows for the concentration of secreted products in areas of relatively fast evaporation, thus providing a passive means of secreted product harvesting. By matching the time scales of nutrient medium delivery and product harvesting with the time scales of growth and product formation, minimal energy is wasted in bioreactor operation. Transpiration enables a passive cooling system for the cells where either externally imposed or internally generated heat due to cellular activity is mitigated, thus preventing overheating that can lead to decreased productivity or even cell death. This technology enables significant reductions in energy input for cultivating microorganisms.

The photobioreactors allow light to enter through their transparent upper surface and optimizes the efficiency of light utilization with a light-reflective lower surface inside. Deployed in the marine environment, the gradient between the freshwater inside the system and the saltwater outside drives forward osmosis. The water removed through semi-permeable (forward osmosis) membranes is cleaned as it is released into the marine environment. In addition, this process concentrates nutrients in the algae medium to stimulate growth, and concentrates the algae to facilitate harvesting. The harvested algae can be used to make biofuels, fertilizer, animal food, or other products. The photobioreactors are intended for use in naturally or artificially protected marine environments with small waves and gentle currents. The system can also be used in artificial brine pools and freshwater basins or reservoirs, however in freshwater the forward osmosis feature cannot be used.

Conventionally, the approaches of creating artificial gravity in space was envisioned as a large rotating space station that creates an inertial force that mimics the effects of a gravitational force. However, generating artificial gravity with large rotating structures poses problems, including (1) the need to mass balance the entire rotating spacecraft in order to eliminate or minimize rotational imbalance causing gyroscopic precession/nutation motions and other oscillations of the rotating spacecraft; (2) the potentially prohibitive cost, time and schedule to build such a large rotating system; (3) the need to mass balance the spacecraft in real-time so as to minimize passenger discomfort and structural stress on the spacecraft; (4) the difficulty in docking other spacecraft to the rotating spacecraft; (5) the absence or minimal presence of non-rotating structure for 0G research and industrial use; and (6) the generation of extraneous Coriolis effect on spacecraft inhabitants. The novel technology can help solve the problems referenced above and other problems by (1) providing a non-rotating space station or structure, and connecting modules that generate artificial gravity by traveling along a circular path around the non-rotating space station; (2) providing modules that are more easily built and balanced; (3) providing a stationary structure that can provide a platform for other components that do not need gravity to function; (4) providing capability to actively interrogate what levels of mass imbalance are acceptable, for use in determining operational constraints; and (5) reducing or eliminating Coriolis effect on occupants in habitation modules. The concepts of the invention are very cost-effective and allow for building a minimal initial system to produce artificial gravity at the first phases of construction, before the full structure is built. An additional benefit is that construction and assembly of new capabilities can be performed without disrupting the ongoing artificial gravity environment of the existing structure.

Early exploratory research with the plasma treatment of water and inedible biomass revealed problems with both efforts. Plasma treatment of water lowered the pH of the water below acceptable levels for plants. Additionally, inedible biomass treated with plasma for nutrient recovery has to be dissolved in acid to enhance that nutrient recovery, and acid can be difficult and dangerous to handle. The technology described here utilizes a single plasma torch to treat both water and inedible biomass. Plasma treatment of the water creates useful species, such as nitrates, to the water which are beneficial for plant growth. However, plasma treatment of water also forms nitric acid, causing the water to be too acidic for plants. Plasma treatment of inedible biomass breaks down the cellulose inside the plant material and reduces it to ash, liberating nutrients such as potassium, calcium, sodium, and phosphorus. Researchers determined that careful dosage of the appropriate amount of the recycled ash to the plasma treated water balances the water's pH level and also adds nutrients that can further enhance plant growth. This method eliminates the need for acid treatment of the plasma treated biomass. For cleaning applications, water can be treated with plasma to either high or low pH extremes for shock sanitation treatment. The system requires a high voltage power supply and a plasma torch. The torch requires a tube for gas transportation, an electrode inside the tube, and an electrode outside the tube. Air can be used for both treatments. The plasma system can be optimized to condense the system into a lunchbox sized package to generate the treated water and ash.