Engineering topics

Chambers, Antja

Publications and source records attributed to Chambers, Antja.

3 records

NASA NTRS2017

Preventing Precipitation in the ISS Urine Processor

The ISS Urine Processor Assembly (UPA) was initially designed to achieve 85% recovery of water from pretreated urine on ISS. Pretreated urine is comprised of crew urine treated with flush water, an oxidant (chromium trioxide), and an inorganic acid (sulfuric acid) to control microbial growth and inhibit precipitation. Unfortunately, initial operation of the UPA on ISS resulted in the precipitation of calcium sulfate at 85% recovery. This occurred because the calcium concentration in the crew urine was elevated in microgravity due to bone loss. The higher calcium concentration precipitated with sulfate from the pretreatment acid, resulting in a failure of the UPA due to the accumulation of solids in the Distillation Assembly. Since this failure, the UPA has been limited to a reduced recovery of water from urine to prevent calcium sulfate from reaching the solubility limit. NASA personnel have worked to identify a solution that would allow the UPA to return to a nominal recovery rate of 85%. This effort has culminated with the development of a pretreatment based on phosphoric acid instead of sulfuric acid. By eliminating the sulfate associated with the pretreatment, the brine can be concentrated to a much higher concentration before calcium sulfate reach the solubility limit. This paper summarizes the development of this pretreatment and the testing performed to verify its implementation on ISS.

Muirhead, Dean↗

NASA NTRS2015

Urine Pretreatment History and Perspective in NASA Human Spaceflight

Urine pretreatment is a technology that may seem to have small mass impacts in future spaceflight missions, but can have significant impacts on reliability, life, and performance of the rest of the wastewater management and recovery systems. NASA has experience with several different urine pretreatment systems, including those flow on the space shuttle, evaluated for NASA waste collection systems or used in Russian commodes on ISS, or developed by NASA or industry as alternatives. Each has had unique requirements for shelf life, operational life, and the life or conditions of the stored, treated urine. Each was evaluated under different test conditions depending on mission, and depending on testing experience developed over NASA's history. Those that were flown led to further lessons learned about hardware compatibility and control. As NASA looks forward to human spaceflight missions beyond low Earth orbit, these techniques need to be evaluated in new light. Based on published design reference missions, candidate requirements can be derived for future systems. Initial comparisons between these requirements and previous performance or test results can be performed. In many cases these comparisons reveal data gaps. Successful previous performance is not enough to address current needs.

Anderson, Molly↗

NASA NTRS2013

Miniature Sensor Probe for O2, CO2, and H2O Monitoring in Portable Life Support Systems

A miniature sensor probe, composed of four sensors which monitor the partial pressure of O2, CO2, H2O, and temperature, designed to operate in the portable life support system (PLSS), has been demonstrated. The probe provides an important advantage over existing technology in that it is able to operate reliably while wet. These luminescence-based fiber optic sensors consist of an indicator chemistry immobilized in a polymeric film, whose emission lifetime undergoes a strong change upon a reversible interaction with the target gas. Each sensor includes chemistry specifically sensitive to one target parameter. All four sensors are based on indicator chemistries that include luminescent dyes from the same chemical family, and therefore exhibit similar photochemical properties, which allow performing measurements of all the sensors by a single, compact, low-power optoelectronic unit remotely connected to the sensors by an electromagnetic interference-proof optical fiber cable. For space systems, using these miniature sensor elements with remote optoelectronics provides unmatched design flexibility for measurements in highly constrained volume systems such as the PLSS. A 10 mm diameter and 15 mm length prototype multiparameter probe was designed, fabricated, tested, and demonstrated over a wide operational range of gas concentration, humidity, and temperature relevant to operation in the PLSS. The sensors were evaluated for measurement range, precision, accuracy, and response time in temperatures ranging from 50 aF-150 aF and relative humidity from dry to 100% RH. Operation of the sensors in water condensation conditions was demonstrated wherein the sensors not only tolerated liquid water but actually operated while wet.

Delgado, Jesus↗