Naslov: Miktobi i svemirska stanica
Poruka od: Taki 12.08.2002. 23:28:47
Ne znam koliko ste upuceni u sve probleme koji prate odrzavanje svemirskih stanica, ali jedan od najvecih je kako spreciti gljivice i mikrobe da se tamo nastane. Njih ima svugde i prilicno je komplikovano obezbediti toliko sterilnu sredinu koliko je potrebno za tu vrstu tehnologije. Kosmonauti provode nekoliko dana pred put u sterilnim prostorijama da bi se ocistili od mikroba, sve sto ide gore se sterilise na najsofisticiraniji moguci nacin, ali opet je neizbezno da se na stanici jave kojekakvi nezeljeni putnici. Gljive i mikrobi imaju svoj metabolizam i izlucuju prilicno agresivne hemikalije koje bi veoma brzo dovele do korozije i ostecenja materijala od kojih je stanica izgradjena. Sa druge strane predstavljaju ekstremnu opasnost za kosmonaute jer su to organizmi koji lako i brzo mutiraju i ne moze se pretpostaviti u sta bi mogli da se izmetnu u jednoj tako hermetickoj sredini kakva je stanica... da ne duzim:
Microbes on the Space Station
Wherever humans go microbes will surely follow, and the Space Station is no exception. In this article we take a look at Microbes on the Space Station and how they will be kept in check.
by Patrick L.Barry
Long before the first humans boarded the International Space Station (ISS), something else was living there.
Something unseen, but potentially dangerous. Something with an uncanny ability to survive and reproduce in even the most hostile environments. Something capable of attacking the Station's crew and even the Space Station itself.
Of course we're not talking about some man-eating alien from a science fiction movie. These lurking, mischievous life forms aboard the Space Station are simply microbes: viruses, bacteria and fungi.
"Microbes were the first inhabitants of the Space Station," said Monsi Roman, chief microbiologist for the Environmental Control and Life Support Systems (ECLSS) project at NASA's Marshall Space Flight Centre.
The Space Station's micro-organisms are hitchhikers; they were carried there on ISS hardware and by the assembly crews themselves. "When the Station went up, microbes went with it," says Roman. "Microbes will be the last ones in the Station, too."
Microbes are a fact of life anywhere that humans go. The majority are harmless, and several types are actually beneficial to humans. Nevertheless, certain microbes can pose a health threat to the Station's crew and even attack the materials and hardware of the Station itself. Scientists and engineers at NASA must find ways to keep such micro-organisms on the Space Station under control.
Living in a microbial world
Microbes are everywhere.
"Just stand and breathe, and you're releasing microbes," Roman said. "You can wash and scrub and use antiseptic soap, and you'll still have microbes on your skin. You have them everywhere: in your clothes, on your skin, in your hair, in your body -- everywhere you could think of."
Many people may find the thought of microbes living on and in their bodies disturbing, but living with an entourage of stowaway microbes is natural.
"Generally speaking, microbes are invisible, and so people just don't think of them as much as you do some other things," said Dr. Duane Pierson, director of microbiology at NASA's Johnson Space Centre.
"People need to be reminded that we live in a microbial world," Pierson said. "They were here before us and they'll probably be here afterwards. We co-exist with them very well."
In fact, bacteria in people's intestines help to digest food, providing some otherwise unattainable nutrients, such as vitamin K. A person's resident microbes also actually protect them from infection by competing with dangerous microbes looking for a place to grow.
While it is natural for a person to live with a host of resident microbes, seven people -- each with their own set of microbes -- living in a small, air-tight can for months or years is certainly not.
"When the crew goes up to the station, they'll each have their own microbial flora, and when they return back, for the most part they've exchanged that flora with each other," Roman said. Most of these exchanged microbes are fought off by the crew's immune systems and their own resident microbes, Pierson noted, but the potential for infection is there.
The first step in protecting the health of the crew is testing each crewmate for infection before launch. Only healthy crew members are allowed to fly into space, and they're quarantined before launch to prevent them from contracting harmful germs at the last moment.
Once on the Space Station, the air, water and surfaces with which the crew members interact must be kept clean.
The air in the Space Station will be kept in constant motion, and all the air on the Station will pass through filters -- called High Efficiency Particle Air (HEPA) filters -- on its way to the temperature and humidity control systems.
"The filters were originally designed to remove particulates," Pierson said. "They're very good at removing small particles," such as microbes.
Microbes can ride in the air on particles of dust or in tiny clumps of bacteria or fungi. On Earth, there might be a couple hundred or thousand microbes in each cubic metre of air.
Water will be disinfected by a machine called a "catalytic oxidator," which heats the water to as much as 265 degrees F. The organic molecules in microbes are oxidised by this process, which kills nearly all of them. Just to be sure, the water is then treated with iodine.
After this disinfection, the water should have less than 100 microbes in 100 millilitres of water.
"The water is extremely clean if you compare it to the water that you drink at home," Roman said. "The water on the Station is many, many times cleaner."
For the health of the crew as well as the Station's hardware, microbes must also be kept from growing on surfaces and in nooks and crannies.
"The biggest threat to the Station from the microbes is degradation of the materials," Roman said. "They'll eat pretty much anything."
"As they grow on surfaces, (fungi) produce an acid which will eventually corrode the material," Roman continued. "They start using most materials as a source of food. Have you seen bathroom tile that's been overgrown by mold? Over time, you will notice that the mold has kind of eaten the tile and grout."
As exemplified by the now-famous problems with mold and other fungi aboard the Russian space station Mir, microbes can not only survive in the metallic world of a space station, they can thrive.
Considering the inhospitable environments in which microbes live on Earth, this should come as no surprise.
"They can live in the driest deserts on Earth; they live in Antarctica and also in these deep sea vents and in that boiling water out at Yellowstone. They are very adaptable, and they can grow just about anywhere as long as they have their basic requirements met," Pierson said.
Growth of microbes on the Station's hardware will be controlled in several ways.
First, all materials used in the Space Station are tested for resistance to fungi, such as mold. A paint with a fungus-killing chemical is also used.
Controlling the humidity of the air in the Station is also an effective way of discouraging microbe growth.
"If you reduce the humidity to 65 to 70 percent -- which is what the Space Station is doing -- it's harder for microbes like fungus to grow," Roman said. "They like higher humidities."
And finally, the Space Station crew will keep surfaces clean the old-fashioned way: they'll clean them.
Housekeeping duties will include regularly wiping down surfaces with a cloth containing an antiseptic solution.
All of these measures to minimize microbes in the air and water and on surfaces should allow the Station and its crew to conduct their mission in good health.
"We have a healthy crew going up there, their food (contains very few microbes), and their water is very clean," Roman said. "So the chance of them getting sick from an infection is very low."
Naslov: Voda na SS
Poruka od: Taki 12.08.2002. 23:28:47
Ako se niste zapitali odakle im voda, evo... meni je to bilo onako bas odvratno :-)
Water on the Space Station
Rationing and recycling will be an essential part of life on the International Space Station. In this article, we explore where the crew will get their water and how they will (re)use it.
by Dr Tony Philips and Patrick Barry
Future astronauts poised to blast off for an extended stay on the International Space Station (ISS) might first consider dashing to the toilet for a quick splash at the lavatory, or better yet, a luxurious hot shower. Once on board the ISS, spacefarers are in for a steady diet of sponge baths using water distilled from -- among other places -- their crewmates breath!
If you're squeamish, read no farther, because the crew will eventually include lab rodents -- and they'll be breathing, too. All of the denizens of the space station lose water when they exhale or sweat. Such vapors add to the ambient cabin humidity, which is eventually condensed and returned to the general water supply.
Sometimes it's better not to think about where your next glass of water is coming from!
Rationing and recycling will be an essential part of daily life on the ISS. In orbit, where Earth's natural life support system is missing, the Space Station itself has to provide abundant power, clean water, and breathable air at the right temperature and humidity -- 24 hours a day, 7 days a week, indefinitely. Nothing can go to waste.
In this article, we will examine how the Space Station's Environmental Control and Life Support System (ECLSS), under continuing development at the Marshall Space Flight Centre, will help astronauts use and reuse their precious supplies of water.
Making a Splash in Space
Before recycling can begin, there has to be some water to start with.
"We have plenty of water on the Space Station now," says Jim Reuter, leader of the ECLSS group at the Marshall Space Flight Centre. "The Russian module Zarya is packed with contingency water containers (CWCs) that were carried over from the Space Shuttle during assembly missions earlier this year. They look like duffle bags and each one holds about 90 lbs."
"But it's expensive to ferry water from Earth," he added. "We have to recycle. There's already a Russian-built water processor in orbit that collects humidity from the air. Here at Marshall we're building a regenerative system that will be able to recycle almost every drop of water on the station and support a crew of seven with minimal resupplies."
The ECLSS Water Recycling System (WRS), developed at the MSFC, will reclaim waste waters from the Space Shuttle's fuel cells, from urine, from oral hygiene and hand washing, and by condensing humidity from the air. Without such careful recycling 40,000 pounds per year of water from Earth would be required to resupply a minimum of four crewmembers for the life of the station.
Not even research animals are excused from the program.
"Lab animals on the ISS breath and urinate, too, and we plan to reclaim their waste products along with the crew's. A full complement of 72 rats would equal about one human in terms of water reclamation," says Layne Carter, a water-processing specialist.
It might sound disgusting, but water leaving the space station's purification machines will be cleaner than what most of us drink on Earth.
"The water that we generate is much cleaner than anything you'll ever get out of any tap in the United States," says Carter. "We certainly do a much more aggressive treatment process (than municipal waste water treatment plants). We have practically ultra-pure water by the time our water's finished."
Mimicking Mother Earth
On Earth, water that passes through animals' bodies is made fresh again by natural processes. Microbes in the soil break down urea and convert it to a form that plants can absorb and use to build new plant tissue. The granular soil also acts as a physical filter. Bits of clay cling to nutrients in urine electrostatically, purifying the water and providing nutrients for plants.
Water excreted by animals also evaporates into the atmosphere and rains back down to the Earth as fresh water -- a natural form of distillation.
Water purification machines on the ISS partly mimic these processes, but they do not rely on microbes or any other living things.
"While you try to mimic what's happening on Earth -- which is so complicated if you really think about it -- we have to use systems that we can control 100 percent," said Monsi Roman, chief microbiologist for the project. ECLSS depends on machines - not microbes - because, "if a machine breaks, you can fix it."
The water purification machines on the ISS will cleanse wastewater in a three-step process.
The first step is a filter that removes particles and debris. Then the water passes through the "multi-filtration beds," which contain substances that remove organic and inorganic impurities. And finally, the "catalytic oxidation reactor" removes volatile organic compounds and kills bacteria and viruses.
Every Drop Counts
Once the water is purified, astronauts will do everything possible to use it efficiently. "On the ground, people flick on the faucet and they probably waste a couple of litres of water just because it's free and the water pressure is high," notes Carter.
"On the ISS, the water pressure will be about half what you might experience in a typical household," Carter said. "We don't use faucets on the ISS, we use a wash cloth. It's much more efficient. If you're an astronaut, you'll wet the wash cloth with a spray nozzle and then use the cloth to wash your hands."
On the space station, people will wash their hands with less than one-tenth the water that people typically use on Earth. Instead of consuming 50 litres to take a shower, which is typical on Earth, denizens of the ISS will use less than 4 litres to bathe.
Even with intense conservation and recycling efforts, the Space Station will gradually lose water because of inefficiencies in the life support system.
"We will always need resupply, because none of the water reprocessing technology that is available right now for space flight ... is 100 percent efficient. So there's always some minimal loss," said Marybeth Edeen, deputy assistant manager of environmental control and life support at NASA's Johnson Space Centre
Water is lost by the Space Station in several ways: the water recycling systems produce a small amount of unusable brine; the oxygen-generating system consumes water; air that's lost in the air locks takes humidity with it; and the CO2 removal systems leach some water out of the air, to name a few.
Lost water will be replaced by carrying it over from the Shuttle or from the Russian Progress rocket. The Shuttle produces water as its fuel cells combine hydrogen and oxygen to create electricity, and the Progress rocket can be outfitted to carry large containers of water.
NASA scientists will continue to look for ways to improve the life support systems of the Space Station, reducing water losses and finding ways to reuse other waste products. If the water recycling systems can be improved to an efficiency of greater than about 95 percent, then the water contained in the Station's food supply would be enough to replace the lost water, Edeen said.
"It takes processes that are slightly more efficient than we have developed for the space station to do that," Edeen said. "Those are the next generation water processing systems. Those are being developed now, but they're not ready for space flight yet."
The ECLSS life support system will join the Space Station as part of Node 3, which is scheduled to launch in October 2005. Until then, the environment inside the ISS will be maintained primarily by life support systems on the Russian Zvezda Service Module.