SHIELDING,WASTE and FIRE ProtectionSHIELDING,WASTE and FIRE Protection
Beside other things, shielding is vital in the safety of the
space station and the colonists who will live there. We know that in space
there are many risks, from all kinds of radiation to meteoroids and meteor
showers. Because of this, we will need a suitable protection against
all of them. The radiation protection can be split in two parts:
The passive shielding will be formed all around the space station. It consists
of 4.5 � meter thick layer of Lunar soil, and after that a second layer of two
heavy metals Limonite and Barium. The outside radiation will not be able to
penetrate the two layers of the passive shielding. Why should we use Lunar
soil? Well, the Lunar soil was chosen because, all future space stations will
be built on the Moon, or in space. It will make no difference if we use soils
from other planets or moons. But we should be sure that they don�t contain any
traces of radioactive metals or other kinds of pollution. Secondly, it will not
harm the Earth because it will not be dug from it. The two heavy metals
Limonite and Barium on Earth are used in building walls for nuclear power plants,
storage pits, nuclear shelters and etc. From this we know that they have
the quality of repelling and not letting the radiation to pass through the
metals. Like the soil, Limonite and Barium can be found everywhere in the
galaxy. Picture 1 shows an intersection of a space station wall, with
details of the passive shielding.
Besides the passive shielding, the space station we will have to have
an active shielding too. The difference between the passive and the active
shielding is that the active shielding creates an Electro-magnetic field with
strong potential to change the trajectories of charged particles. The active
shielding is also known as the plasma core shield. The idea is to put an
electron well in the center of the space station. Inside this well about 10
C of electrons spiral along the lines of magnetic force will hold the metallic
habitat at positive potential of 15 billion volts. This enormous electrostatic
potential repels the protons and other cosmic ray nuclei from the habitat, and
will cast off the cosmic ray spectrum for energies below 7.5 GeV/ nucleon (15 GeV
for protons). The plasma core is new an it has some difficulties in some
areas of it. Until extensive work is done to study all of these problems, the
plasma core shield cannot be claimed as a practical solution to the radiation
problem in space. In Picture 2 we can see an intersection of a space station
wall, with detail of the passive and active shielding.
Meteoroids and meteor showers pose a great risk to the space station as well. If
the space station is in orbit on some planet then the planets atmosphere can be
used as a shield against meteors, but if the space station is in space, well
that is another thing. Tiny and small meteors can be harmful because they can
only bend the wall on the space station or make small holes that can be fixed.
Large meteors can cause serious damage or in some cases destruction to the
space station. Bumpers can provide protection. They will absorb most of the
meteoroid impact. In Picture 3 we can see the bumpers and how will they react
if a meteor strikes them.
When a meteoroid strikes, the bumper will absorb the impact and nothing
happens to the station. It will be better to have a double skin of meteoroid
bumpers. When a particle strikes the station, the other shield takes the force
of the blow.
Even on a space station, waste will be produced. If we don�t find a suitable
solution, waste can be a big problem for the colonist. We will have to find a
way to remove or to reuse the waste that will be produced. The waste generated on
the space station are of four general types:
For long duration missions the best method for dealing with the waste is to
recover and transform the waste to useable products as much as possible. Some methods are specific for the type of waste while others can process waste of virtually any
type. The question that prevails is why the waste should be recovered not
simply vented in to space. Venting it to space on longer duration missions is
prohibitive, because that way we will get rid of the waste but in the same
time we will lose mass and pollute space with waste.
Metabolic waste
Other solid waste
Liquid waste
Gaseous waste
Fires on space stations can be disastrous and the potential for fires must be
minimized. Using materials, which are resistant, and designing a habitat and
its systems to not propagate fire reduces the likelihood of a major fire. Even
so, the possibility of a fire cannot be totally eliminated. It therefore
becomes important to detect a fire as early as possible.
Detection of incipient fires
The sense of smell is a sensitive and reliable method of detecting a fire,
which is available on all human space missions. However, fires may occur
during sleep periods, and as space habitats become larger not every module
will be continually occupied. Therefore, reliable automatic methods are
needed. Those methods include flame detectors based on visible, infrared and
ultraviolet emissions and smoke detectors based on detecting the particles
emitted by burning materials. Due to spurious alarms by the fire detectors,
there have been missions where the sense of smell was the only reliable
method. Because of this, improvements are needed in discriminating between
smoke particles and other particles. Some of the newer technologies developed
to detect fires are ionization detectors and photoelectric flame detectors.
Another promising method being developed uses an expansion chamber to detect
condensation nuclei produced by particles given off by heated materials prior
to combustion.
Suppression of fires
Fires can be suppressed by removing the oxidizer (by suffocation) or the
fuel (by shutting off the flow) and/or by removing the heat required for
combustion to occur. The methods that are used on Earth (including water,
foam, CO2 and Halon) cannot be used on the space station because of the
consequences after use.
For example, if we suppress fires using water, electrical failures may result and likewise, using foam creates a cleanup problem.
.The best fire suppression for the space
station will be usage of CO2. This is the best solution because CO2
can effectualLY suppress a fire and makes the cleanup process a relatively simple task. Other methods of
fire suppression include N2 and depressurization of the habitat.
Cleanup after a fire
Any fire will create byproducts, which may be hazardous. The degree of hazard
depends upon the types of materials burned, the temperature of the fire and the type of suppressant used to extinguish the fire. Removing those
byproducts from the atmosphere is essential. The best method for
cleaning up after a fire depends in part upon the severity of the fire and the
amount of byproducts produced. For a severe fire which produces a lot of smoke
particles the best method may be to depressurize the affected area of the
space station by venting the contaminated atmosphere out to space. If this is not
possible other solutions must be used. If the fire is in an area where
decompression or suffocation of the fire with CO2 is not possible then the
method using water will be used, and the contaminated atmosphere will be
cleaned from the contamination system that will be onboard. For a smaller
localized fire some type of portable contamination system device may be able
to remove most of the contaminants from the atmosphere so that the trace
contaminant system can safely remove the remaining contaminants.
Surface contamination by potential corrosive combustion byproducts may also
result, depending on the material burned and the suppressant used. Those
byproducts will have to be removed without causing additional contamination by
wiping the surfaces with a solvent or a neutralizing agent to prevent
corrosion.
Other methods and systems will be designed by the colonists on the space
station or settlement. They will be designed by their specific needs.
Author: Vladimir Simonovski
This site was hosted by the NASA Ames Research Center from 1994-2018 and is now hosted by:SHIELDING
WASTE
For long duration missions metabolic waste (liquid and solid) can be
recovered. Water can be recovered by dehydration but this process leaves the
solid portion of the feces. Ideally this would be converted to fertilizer for
plants which would provide a significant portion of minerals and food
requirements. Metabolic waste also can be recovered in to CO2 and H2O, but
this recovery is not good because large amounts of O2 and energy will be
consumed for this process.
Other solid wastes (paper, disposable dishes, paper cups etc.) consist
primarily of paper and plastic, so if they are made from recycled materials
(recycled paper or recycled plastics) they can be recycled in special plant on
the space station so the same paper or plastic will be �going around in a
circle�. For the dishes Japanese scientists invented a very practical item,
edible dishes. The dishes are made from rice that is pressed in large
pressing machines under significant pressure. After this you have an ordinary dish, like
any other dish but this one you can eat. For other solid waste we will have to
find alternatives how to reduce the amount.
Sources of liquid waste include urine and brine residues from some of the
water processors. Converting the liquid wastes we can make very useable
products. One of those products is to reclaim water from urine as a feed to the
electrolysis cells. Electrical energy must be consumed for the reaction to
proceed. The Oxygen Generation Assembly (OGA) consists of 18 electrolysis
cells constructed using ion exchange membranes and a conducting polymer termed
a Solid Polymer Electrolyte. Oxygen is produced at ambient pressure and vented
to the cabin. Hydrogen is produced at slightly elevated pressure as a
potential supply source for a carbon dioxide reduction system (Sabatier
Reactor). With this we are able to reuse the liquid waste, make oxygen and at
the same time make hydrogen for the Sabatier Reactor from which we can make
water.
Sources of gas waste include metabolic gaseous wastes (CH4, H2S, H2, CO, CO2)
and byproducts from various chemical processes. The gaseous wastes may be
removed or transformed to H2O and CO2 by the atmospheric trace contaminants control assembly.Fire Protection
Curator: Al Globus
If you find any errors on this page contact Al Globus.
