ICES-2020-236 The Water Management on the Russian Segment of the International Space Station and Prospective Space Stations Petr Andreychuk,1Sergey Romanov2 and Alexander Zeleznyakov,3 RSC Energia, Russia, Korolev. Leonid Bobe,4Alexey Kochetkov,5 AlexanderTsygankov6 and Dmitry Arakcheev,7 NIICHIMMASH, Russia, Moscow. Yury Sinyak8 IMBP RAN, Russia, Moscow The paper summarizes the experience gained with the Russian Segment of the International Space Station (RS ISS) water management system during the missions ISS-1 (since November 2, 2000) through ISS-60. The performance data of the system for water recovery from humidity condensate (SRV-K) and urine feed and pretreatment (SPK-U) systems in the Russian orbital segment are presented. The key role of water recovery onboard the ISS and the need to supplement the RS water supply hardware with a system for water reclamation from urine SRV-U is shown. The prospects of regenerative water supply system development are considered. Nomenclature “Electron-V” = oxygen generation system” CDRA = CO2 removal system CDCS = CO2 concentration system CDRS = CO2 reduction system HW = hygiene water ISS = International Space Station RS ISS = Russian segment of the ISS USOS = US orbital segment of the ISS LSS = life support systems MFR = membrane filter-separator PDV-U = urine distillation (water recovery) subsystem RMVD = rotary multistage vacuum distiller SOV = water purification facilities SPK-U = urine feed, separation and pretreatment system SRV = water regeneration system SRV-HG = hygiene water processing system SRV-K = the system for water recovery from humidity condensate SRV-U = urine reclamation system SRV-U-RS = updated urine reclamation system for RS ISS SVO = water management (water supply) system SVO-ZV = water supplies (stocks) system THP = thermoelectric heat pump WPCS = waste purification and collection system 1 Head of sector, LSS department, Russia,.141670 Korolev, Lenin street, 4a. 2 Deputy of chief designer, Russia,.141670 Korolev, Lenin street, 4a. 3 Head of science center, Russia,.141670 Korolev, Lenin street, 4a. 4 Head of laboratory SRV, Russia, 127015 Moscow, B.Novodmitrovskaya, 14. 5 Head designer, Russia, 127015 Moscow, B.Novodmitrovskaya, 14. 6 Head director, Russia, 127015 Moscow, B.Novodmitrovskaya, 14. 7 Senior research fellow, Russia, 127015 Moscow, B.Novodmitrovskaya, 14. 8 Head of department, Russia, 123007 Moscow, Khoroshevskaya street, 76a. Copyright © 2020 RSC-Energia, NIICHIMMASH, IMBP RAN I. Introduction. mplementation of promising orbital and interplanetary missions is associated with improvements in crew life I support systems (LSS). One of the LSS key components are water supply systems. The systems should provide maximum recovery of water from water-containing products of life and from bioengineering systems meeting the needs of minimum water consumption the crew. Experiences in the design and operation of “Salut”, “Mir” and the International Space Station (ISS) water supply systems as well as the use of supplies delivered made it possible to obtain the data on human water balance on the space station and the operation parameters of the recovery systems.1,2,3 In the near future, due to the energy, volume and mass restrictions, the water recovery systems will be based on physical/chemical processes. The processes selected depend on the trace contaminant content in the feed liquid and the requirements for the water recovered: a sorption/catalytic and an ion-exchange processes for humidity condensate from the cabin and greenhouse atmosphere, distillate from urine processor and water from carbon dioxide reduction; membrane filtration (ultra-filtration and reverse osmosis) with an ion-exchange post-treatment of hygiene water; the distillation method accompanied by distillate sorption/catalytic purification.4,5 The RS ISS uses water recovered from humidity condensate (SRV-K2), the system of reception and preservation of urine SPK-U, the system of water-supplies (SVO-ZV), and the water regeneration system from urine (SRV-U-RS) that is tested on RS ISS now. The paper summarizes the experience gained with the RS ISS water management system during missions ISS-1 (since November 2, 2000) through ISS-60. The performance data SRV-K and SPK-U are presented. The key role of water recovery onboard the ISS and the need to supplement the RS water supply hardware with a system for water reclamation from urine SRV-U is shown. The prospects of regenerative water supply system development are considered. II. The System of Water Recovery from Humidity Condensate (SRV-K) The method for the removal of dissolved impurities includes sorption/catalytic and ion-exchange processes, first in the gas-liquid and then in the liquid phase is used in this system. The processes of catalytic oxidation of hard-to- sorption low-molecular organic compounds (for instance alcohols and glycols) are the most difficult to implement. The task is a complete purification to distilled grade. Then salts, microelements and biocide are added to the potable water. This method is used in the systems SRV-K on orbital space stations “Salut”, ”Mir” and ISS (Figure 1).6,7,8,9 Figure 1 shows a diagram for SRV-K. Each process steps are described here: (#1)filtration in a gas/liquid stream; (#2) heterogeneous catalytic oxidation of organic impurities in gas/liquid stream by oxygen of carrier air at temperatures and pressure on a station; a direct-flow separation of a liquid through capillary-porous walls of pipes (#3) with suction by a membrane spring pump (#5); pumping a liquid (#6); catalytic, ion-exchange and sorption purification of a liquid in a semi-static mode (# 7); the monitoring of water quality (#8); contact injection of food salts and ions of silver (position 10); storage of liquids in containers with variable volume (# 11 and #12); recovered water heating and pasteurization in the subsystem III and supplying astronauts with hot and ambient potable water. The humidity condensate is transported from the air conditioning system to the SRV-K2M system by air flow. The liquid is purified and separated in the static separator into the membrane, #5, (Figure 1). Before filling up of the membrane (except of the equipment for preheating and distribution of water to the crew), the system is in standby mode and consumes virtually no energy. After filling the membrane (#5), the liquid is pumped out by the pump #6 for 16-18 seconds. Then, the system again switches to the standby mode. For a crew of 3 people (4.8 liters of condensate needs to be cleaned per day) such situation is repeated 27 times a day, i.e. a system work period for the receipt and purification of humidity condensate is less than 10 minutes a day. Therefore, SRV-K has a unique low energy consumption for the reception and purification of condensate – no more than 2 Wh per 1 liter of recovered water. The average daily power consumption of the system for a crew of 3 people is 30W taking into account the energy costs for heating water for drinking and cooking. 2 International Conference on Environmental Systems Technical data for SRV-K type systems: Mass 140 kg (“Salut”); 104 kg (Mir); 115 kg (ISS). Specific mass consumptions, kg/L H2O: 0.12 (Mir);0.08 (ISS). Average daily energy consumptions for 1 crew member: 14 W-hour (Mir); 10 W-hour (ISS). Water recovered: 15500 L (Mir); 22265 L (ISS February 1, 2020) Figure 1. The SRV-K2M system for water recovery from humidity condensate on ISS. The system consists of blocks that are replaced as spare parts are delivered from the ground. The specific weight (including the equipment to be replaced) for the production of 1 liter of water is 0.08 kg. The regenerated water met water quality requirements for the entire operation time. Power consumption and mass requirements of the water recovery system SRV-K (from November 2, 2000 until February 01, 2020) are presented in Table 1. Table 1. The water recovery system SRV-K(from November 2, 2000 until February 01, 2020) Mass of the initially installed system 115 kg Average daily power consumption for 3 person crew * for feed and recovery 0.4 W * for feed, recovery and heating 10 W/per 1 crew member Specific energy for feed and recovery 2 W-hr/L H2O The water recovery rate in SRV-K, % 100 Mass of the hardware replaced during the flight (ORU) * specific 0.08 kg/L H2O 3 International Conference on Environmental Systems Amount of water recovered from humidity condensate and 22265 L other water Amount of water consumed from SRV-K 34970 L Savings in mass of water to be delivered in the absence of 26000 kg water recovering (including the mass of tanks 0.25kg/L minus mass of the replaced hardware delivery) Thus, the process of sorption-catalytic purification of liquids such as humidity condensate is sufficiently effective and recommended for use in advanced water regeneration systems. The main objective of improving the system is to increase the resource and the corresponding reduction in the weight of the equipment. Such events are already taking place. For example, the introduction of a two-stage separation scheme using a membrane filter-separator allowed to increase the service life of the static separation unit of the system in 10 times without increasing energy costs. III. Urine Feed and Pre-treatment (SPK-U) System. In the system SPK-U (Figure 2)2,6,7,10,11,12 urine from the crew is sucked in the urinal (1) with an air stream by the fan (12). Pretreatment chemicals (3) providing chemical and microbiological stability of urine in storage and subsequent processing and flush water (4) are metered out by the pump (2) in a gas-liquid flow. The urine is separated from the carrier air in the rotary separator (7). The carrier air passes through the backup static separator (9) filled with a water-retentive material and vented to the atmosphere.