User:Craigboy/Waste Management Systems in Space



Waste Management Systems in Space refers to the systems used to collect urine, menstrual, and fecal waste in the weightless or low gravity environments of outer space. When WCS fail it can result in unhygienic and aesthetically unpleasing conditions, along with the spread of substantial quantities of bacterial contamination, noxious odor problems, and crew reluctance to use.

You poop less and drink less water. You urine has more calcium. In the absence of weight, the collection and retention of liquid and solid waste is directed by use of air flow. Since the air used to direct the waste is returned to the cabin, it is filtered beforehand to control odor and cleanse bacteria. In older systems, waste water is vented into space and any solids are compressed and stored for removal upon landing. More modern systems expose solid waste to vacuum to kill bacteria, which prevents odor problems and kills pathogens. WCS has been defined as.

Background
When astronauts traveled into space, the absence of gravity causes fluids to distribute uniformly around their bodies. Their kidneys detect the fluid movement and a physiological reaction causes the humans to need to relieve themselves within two hours of departure from Earth. As a result, the space toilet has been the first device activated on shuttle flights after astronauts unbuckle themselves.

Basic parts


There are four basic parts in a space toilet: the liquid waste vacuum tube, the vacuum chamber, the waste storage drawers, and the solid waste collection bags. The liquid waste vacuum tube is a 2 to 3 ft long rubber or plastic hose that is attached to the vacuum chamber and connected to a fan that provides suction. At the end of the tube there is a detachable urine receptacle, which come in different versions for male and female astronauts. The male urine receptacle is a plastic funnel two to three inches in width and about four inches deep. A male astronaut urinates directly into the funnel from a distance of two or three inches away. The female funnel is oval and is two inches by four inches wide at the rim. Near the funnel's rim are small holes or slits that allow air movement to prevent excessive suction. The vacuum chamber is a cylinder about 1 ft deep and six inches wide with clips on the rim where waste collection bags may be attached and a fan that provides suction. Urine is pumped into and stored in waste storage drawers. Solid waste is stored in a detachable bag made of a special fabric that lets gas (but not liquid or solid) escape, a feature that allows the fan at the back of the vacuum chamber to pull the waste into the bag. When the astronaut is finished, he or she then twists the bag and places it in a waste storage drawer. Samples of urine and solid waste are frozen and taken to Earth for testing.

Soyuz
The Russian Soyuz toilet (the Russian acronym is Soyuz АСУ) is part of the Soyuz orbital module. A photo of the АСУ components is shown in Figure 9 and a schematic is illustrated in Figure 10. The Soyuz АСУ provides very basic WCS functions for two days from launch to orbital docking and eight hour reentry missions. The system normally remains dormant for up to 180 days on-orbit. However, it was periodically used on MIR for menstrual waste collection during female crewed MIR missions. There is no automation, instrumentation, or fluid transfer, but the system does use air flow to entrain urine, control fecal material, and control odors. Several of the components are similar or use similar technology as the ISS Service Module (SM) АСУ described subsequently. The АСУ operates by the crew standing in the aisle way and manually positioning a combination funnel and fecal receptacle attached to a hose (Museum of Discovery and Science, 2006). The crew can direct the 250 l/min of air to the fecal receptacle or split it between both the urine funnel and fecal receptacle. Air flow is directed through a static separator tank containing polyvinylformaldehyde foam material, which adsorbs the urine, before exiting a charcoal air filter and fan. A manual squeeze bulb and valve provides urine contingency operations in the event of fan failure, as illustrated in Figure 9. For fecal collection, a porous bag is placed in the receptacle. Once defecation is complete, the bag is removed, placed sequentially in three bags, and then placed in a wet trash compartment. Based on personal conversations with АСУ trainers, urine collection is acceptable but fecal use is avoided if at all possible with the crew using diet restrictions and preventive measures prior to flight. The system has limited capacity and the history of flight anonymities is unknown.

International Space Station
There are two toilets on the International Space Station, located in the Zvezda and Tranquility modules. They use a fan-driven suction system similar to the Space Shuttle WCS. Liquid waste is collected in 20 litre containers. Solid waste is collected in individual micro-perforated bags which are stored in an aluminum container. Full containers are transferred to Progress for disposal. An additional Waste and Hygiene Compartment is part of the Tranquility module launched in 2010. In 2007, NASA purchased a Russian-made toilet similar to the one already aboard ISS rather than develop one internally.

On May 21, 2008, the gas liquid separator pump failed on the 7-year-old toilet in Zvezda, although the solid waste portion is still functioning. The crew attempted to replace various parts, but was unable to repair the malfunctioning part. In the interim, they used a manual mode for urine collection. The crew had other options: to use the toilet on the Soyuz transport module (which only has capacity for a few days of use) or to use urine collection bags as needed. A replacement pump was sent from Russia in a diplomatic pouch so that Space Shuttle Discovery could take it to the station as part of mission STS-124 on June 2.

The Soviet/Russian Space Station Mir's toilet also used a system similar to the WCS.

While the Soyuz spacecraft had an onboard toilet facility since its introduction in 1967 (due to the additional space in the Orbital Module), all Gemini and Apollo spacecraft required astronauts to urinate in a so-called "relief tube," in which the contents were dumped into space (an example would be the urine dump scene in the movie Apollo 13), while fecal matter were collected in specially-designed bags. The Skylab space station, used by NASA between May, 1973 and March, 1974, had an onboard WCS facility which served as a prototype for the Shuttle's WCS, but also featured an onboard shower facility. The Skylab toilet, which was designed and built by the Fairchild Republic Corp. on Long Island, was primarily a medical system to collect and return to earth samples of urine, feces and vomit so that calcium balance in astronauts could be studied.

Even with the facilities, astronauts and cosmonauts for both launch systems employ pre-launch bowel clearing and low-residue diets to minimize the need for defecation. The Soyuz toilet has been used on a return mission from Mir.

NPP Zvezda is a Russian developer of space equipment, which includes zero gravity toilets.

Project Mercury
There were only six Mercury flights, they all consisted of all male crews and were relatively short in duration. The first two missions last only about 15 minutes, the second two last only about five hours did not exceed 34 hours mission duration and consisted of all-male crews. The crew never left their pressurized suits. Urine waste was collected in an intimate contact prophylactic roll-on cuff Urine Collection Device (UCD). Although a very simple mechanism, the UCD system experienced at least one unexpected in-flight leakage (JSC Life Science Data Archive, 2006). Later Mercury missions allowed transfer of urine from inside the UCD to an external storage bag using a manual syringe pump and enabled samples for medical analysis to be collected. Crew defecation was avoided through the use of a low solids residual diet prior to the flight.

Project Gemini
The ten Gemini missions lasted up to 14 days and consisted of all male crews operating in and outside of their pressurized suits. Gemini developed most of the WCS hardware later utilized on the eleven Apollo missions which lasted up to 12 days, and two Apollo-Soyuz flights. The Apollo hardware has previously been described in detail (Sauser and Jorgensen, 1975) but it is summarized here due to frequent comparisons between Apollo and Constellation missions. The functionally of the Mercury UCD roll on cuff and bag was improved for in-suit operations as the Urine Collection Transfer Assembly (UCTA) and an out-of-suit configuration as the Urine Transfer System (UTS), shown in Figure 1. Apollo 12 and later flights utilized a non-contact Urine Receptacle Assembly (URA). The URA allowed urination volumes of up to 700 ml to be captured. The URA consisted of a hand held cylindrical unit consisting of a hydrophilic screen on the surface to capture the urine and minimize splashing. The urine was retained in a honeycomb filled cavity under the screen. The urine in the honey comb was evacuated overboard when the URA was connected to the vacuum vent system. The URA was a significant improvement because the device was easier to use and clean, however, urine spills were common. The URA pulled the urine into the device with up to 0.01 m3/minute of air flow. However, the urine velocity vector from the crew was the primary delivery force. The low air flow rate is not suitable for female usage due to the low velocity vector during urination.

Due to the increased mission length, fecal collection had to be addressed. The Gemini/Apollo fecal bag consists of a non-permeable nylon-polyethylene bag with adhesive ring at the top that attached to the crew buttocks, shown in Figure 2. The bag contained an integrated finger cot on the side. There was no air flow and the crew used the finger cot to manually detach the feces and manipulate it into the bag. Wet wipes and tissues were used for cleanup and also placed in the bag. The feces were stabilized by adding a germicidal agent into the bag and manually kneading it through the feces. The bag was rolled up, sealed, and placed in a second vented storage bag. Several configurations of adhesive rings and finger cots were developed and flown. The fecal bag system was marginally functional and was described as very ‘distasteful’ by the crew. The bag was considered difficult to position. Defecation was difficult to perform without the crew soiling themselves, clothing, and the cabin. The bags provided no odor control in the small capsule and the odor was prominent. Due to the difficulty of use, up to 45 minutes per defecation was required by each crew member, causing fecal odors to be present for substantial portions of the crew’s day. Dislike of the fecal bags was so great that some crew continued to use preflight countermeasures and used medication to minimize defecation during the mission. The Apollo fecal bags and a lighter weight UCD type device are still used by Shuttle as contingency devices. The Apollo devices are included in the analysis for comparison purposes but are not recommended for Constellation missions for primary WCS functions due to the overwhelmingly negative Apollo crew feedback.

Skylab
The three Skylab flights lasted up to 84 days and consisted of all male crews operating primarily outside of their pressurized suits. The volume required for waste management was copious by comparison to all other space vehicles. Collection and stabilization of urine and fecal waste for subsequent medical analysis was a primary requirement of the Skylab WCS. Hence, many of the WCS hardware features were oriented toward capturing each crew’s waste separately. Skylab provided significant increases in WCS capability and crew comfort through the use of air flow to eliminate intimate crew contact for waste collection (MSFC Skylab Orbital Workshop Vol III, 1974). Air flow was increased to 140 l/min to eliminate previous URA splashing and urine pooling problems. Urine was entrained with airflow through a hose mounted funnel. Urine was separated from the air using rotary separators and collected in individual bags for medical evaluation. Fecal collection used a deployable sit-on seat with air flow entrainment. The crewmember’s buttocks formed a seal with the seat. Air flow entered radically below the seat and converged on the bolus, drawing it down into a gas permeable bag mounted below the seat, illustrated in Figure 3. The airflow aided in the separation and capture of the bolus and minimized the need for manual feces manipulation. Individual fecal bags were used and removed for vacuum drying and storing. Air flow was returned to the cabin after odors were removed with a charcoal filter. Both urine and fecal collection systems generally received positive crew comments compared to Apollo although the crew recommended both urine and fecal airflow rates up to 50% higher to improve entrainment. The Skylab WCS was not included in the study because detail component information was unavailable to enable separation of the medical sampling hardware from the collection hardware. However, all following US and Russian WCS systems use air flow entrainment as the primary urine and fecal collection mechanism so this technology improvement is adequately captured in other analyzed WCS.

Space Shuttle Waste Collection System


The toilet used on the Space Shuttle is called the Waste Collection System (WCS). In addition to air flow, it also uses rotating fans to distribute solid waste for in-flight storage. Solid waste is distributed in a cylindrical container which is then exposed to vacuum to dry the waste. Liquid waste is vented to space. During STS-46, one of the fans malfunctioned, and crew member Claude Nicollier was required to perform in-flight maintenance (IFM). An earlier, complete failure, on the eight-day STS-3 test flight, forced its two-man crew (Jack Lousma and Gordon Fullerton) to use a fecal containment device (FCD) for waste elimination and disposal.