Abstract
Recycling systems aboard spacecraft are currently limited to approximately 80% water recovery from urine. To address challenges associated with odors, contamination, and microgravity fluid flow phenomena, current systems use toxic pretreatment chemicals, filters, and rotary separators. Herein, a semipassive and potentially contaminant- and biofouling-free approach to spacecraft urine processing is developed by combining passive liquid–gas separation, nanophotonic pasteurization, and noncontact Leidenfrost droplet distillation. The system aims to achieve >98% water recovery from wastewater streams in zero, Lunar, Martian, and terrestrial gravitational environments. The surfaces of the phase separator are coated with carbon black nanoparticles that are irradiated by infrared light-emitting diodes (LEDs) producing hyperlocal heating and pasteurization during urine collection, separation, and storage. For the prescribed flow rate and timeline, the urine is then introduced into a heated 8.5-m-long helical hemicircular aluminum track. The low pitch and the high temperature of the track combine to establish weakly gravity-driven noncontact Leidenfrost droplet distillation conditions. In our technology demonstrations, salt-free distillate and concentrated brine are successfully recovered from saltwater feed stocks. We estimate equivalent system mass metrics for the approach, which compare favorably to the current water recovery system aboard the International Space Station.