Futuristic Spacesuit
Introduction
The space suit, arguably one of the most recognized equipment for space travel helped lead various different accomplishments such as Mercury (first American in space), Gemini (first American spacewalk), Apollo (first Moon landing), and Skylab (first American space station). The development and manufacturing of space suits has existed for as long as the US program has and it continues to advance more and more owing to the rapid scientific and technological progression.
Harsh conditions of space
The following passage consists of the type of environment and the harsh conditions of space, it also illustrates the various hazards that could be faced due to exposure. As expected, space has one of the most extreme environmental conditions imaginable, from the extreme temperatures to the increased threat of radiation damage; even the tiniest bit of exposure could lead to some irreversible impairment. So how exactly are humans allowed to travel to space? The advancement of the science and technology sector of the world has been so structured and systematic that humans have now found a way to travel to space without any threat, let’s now look at the main source of this need for particular scientific equipment.
The conditions of space vary due to variaous conditions.
- The inconsistent temperature changes
- Thermal cycling
- Ultra-vacuum
- Atomic oxygen
- Ultraviolet radiation
- Particulate radiation
- Plasma
- Orbital debris
The Low earth Orbit (LEO) is particularly harsh for nonmetallic materials due to the single atom oxygen.
Here is an example of Atomic oxygen erosion and radiation induced embrittlement.
VACUUM
Vacuum is the complete opposite of the traditional vacuum cleaner so we can not consider a vacuum cleaner as an analogy to the vacuum in space, the main function of a vacuum cleaner essentially is to use differential pressure to create suction however the vacuum in space is devoid of matter, it is nearly empty. This results in extremely low pressure, there is no atmosphere and no pressure exerted by air molecules. The atmospheric pressure outside liquids determines the temperature at which the liquid boils and turns into a gaseous state, but since virtually there is no atmospheric pressure in space, the boiling point of the liquid decreases. “As you can imagine, given that 60% of the human body is made up of water, this is a serious problem," Dr. Kris Lehnhardt, a NASA operational space medicine physician explained. Since there is no pressure, the water in our bodies would start boiling, changing from liquid to gas; "In essence, all of your body tissues that contain water will start to expand," there is a transition of liquid water in the bloodstream and soft tissues into water vapor.This change is commonly known as ebullism. According to NASA's bioastronautics data book, the vacuum in space pulls the air out of your lungs, which will cause suffocation. The evaporation of water from your body and the slow loss of heat through radiation also causes freezing. The hard vacuum of space (10-6 to 10-9 torr) also causes outgassing, which is a process in which a non metal will release a gas, this gas condenses on other materials eventually rendering them inoperable.
ATOMIC OXYGEN
Atomic Oxygen is produced when short-wavelength UV radiation reacts with molecular oxygen in the upper atmosphere. Atomic Oxygen (O) is a single atom molecule that is highly reactive. Due to its reactive properties, atomic oxygen does not exist naturally on earth for long. The Low Earth Orbit is made of 96% Atomic Oxygen, "In the first few shuttle flights, materials looked frosty because they were actually being eroded and textured," says Bruce Banks, a senior physicist with Alphaport, supporting the Space Environment and Experiments branch at Glenn. "Atomic oxygen reacts with organic materials on spacecraft exteriors, gradually damaging them." . AO oxidizes many metals, especially silver, copper, and osmium. AO reacts strongly with any material containing carbon, nitrogen, sulfur and hydrogen bonds, meaning that many polymers react and erode. Polymers containing fluorine, such as Teflon, react synergistically, meaning that the reactivity to AO increases with longer exposure to UV radiation (Pippin et al., 2004). When breathed in, the Atomic Oxygen reacts on contact with your body, it will react with your nasal passages and the surface of your lungs producing very irritating chemicals (like hydrogen peroxide) and an enormous amount of heat. Furthermore, Atomic oxygen reacts to itself to form molecular oxygen and liberate even more heat. Also to be considered are the mission duration and the specific mission environment, including orbital parameters for the mission, the solar cycle and solar events, view angle of spacecraft surfaces to the sun and orientation of spacecraft surfaces with respect to the spacecraft velocity vector in LEO.
ULTRAVIOLET RADIATION and IONISING RADIATION
Space Radiation differs from the radiation on Earth, Space radiation is composed of atoms in which electrons have been stripped away as the atom accelerated in interstellar space to speeds approaching the speed of light in which eventually only the nucleus remains. While AO bleaches materials, UV radiation essentially darkens these materials, particularly in the presence of contamination, this color change is caused due to oxygen vacancies being created in oxides by UV under high vacuum. UV radiation also damages polymers by either cross-linking (hardening) or chain scission (weakening). As space has no atmosphere to protect astronauts from UV rays, they face an increased risk of exposure to these rays. Exposure can include risks of getting cancer, radiation sickness, central nervous system effects, and degenerative diseases. “Research studies of exposure in various doses and strengths of radiation provide strong evidence that cancer and degenerative diseases are to be expected from exposures to galactic cosmic rays (GCR) or solar particle events (SPE).” states NASA. Radiation however is of two types, non ionising and ionising, Ultraviolet radiation is a form of non ionising radiation. Non ionising refers to low energy while ionising is high energy. Ionizing radiation consists of particles that have enough energy to completely remove an electron from its orbit, thus creating a more positively charged atom, examples of these types of radiation include alpha particles, beta particles, gamma rays, x-rays, and galactic cosmic radiation (GCR) from space. Ionising Radiation is very difficult to avoid. Ionizing radiation has the ability to move through substances and alter them as it passes through. When this happens, the atoms are ionised in surrounding materials. The three main sources of charged particle radiation naturally occurring in space are galactic cosmic rays, solar proton events, and the trapped radiation belts. Ionising Radiation can affect the tissue and DNA in genes. Direct tissue damage happens when enough molecules are broken apart that the cells simply can no longer function. This can lead to radiation burns, radiation sickness, organ failure, and even death.
PLASMA
The universe is made of space Plasma which is also the fourth state of matter. Plasma essentially is a gas whose temperature is so high that constituent atoms are split up into ions and electrons. The plasma environment is composed of approximately equal amounts of positively charged oxygen ions (O+) and free electrons and varies with solar activity and altitude. Because of the differences in spacecraft velocities, ion thermal energy and electron thermal energy, electrons can impact any spacecraft surface, while ions can only impact ram (leading edge) surfaces. This can lead to a negative charge buildup, which can lead to ion sputtering, arcing and parasitic currents in solar arrays, as well as reattraction of contamination (James et al., 1994). Plasma may be harmful to humans as it may emit radiation.
TEMPERATURE
A misconception about space is the fact that its cold when in reality space has no definitive temperature. In thermodynamic terms, temperature is a function of heat energy in a given amount of matter, and space by definition has no mass. Furthermore, heat transfer cannot occur in space as conduction and convection require matter. The degree to which a material experiences thermal cycling temperature extremes depends on its thermo-optical properties (solar absorptance and thermal emittance), its view of the sun, its view of Earth, its view of other surfaces of the spacecraft, durations of time in sunlight and in shadow, its thermal mass and the influence of equipment or components that produce heat ( Dever et al., 2005). Essentially, these cyclic temperature variations are -120 °C to +120 °C, but high solar absorptance with low infrared emittance can cause greater temperature swings. Furthermore, floating objects have a base temperature of -455 degrees Fahrenheit (-270 degrees celsius), but a person would not freeze as heat cannot be transferred at a fast pace through radiation alone.
ORBITAL DEBRIS IMPACT
Spacecrafts may be impacted by micrometeoroids traveling as fast as 60 km/s. Surfaces facing the ram direction are more likely than those in the wake direction to be hit with space debris, traveling at an average velocity of 10 km/s. Space Debris essentially depends on the solar cycle and varies accordingly, to put this into perspective, as the Sun’s activity increases, the atmosphere heats up, increasing the drag on space debris in orbit.Large space debris is tracked so that the spacecraft can perform the correct maneuvers in order to avoid being impacted. An impact caused by a micrometeoroid or debris may crater the vessel, spall off a coating or short out a solar cell. Space Debris however imposes quite a catastrophic threat to astronauts if they ever come in contact with it which is highly unlikely.
Development of a Space Suit
Space suits were developed to protect astronauts from the potential threats of space. A space suit is essentially designed to recreate the atmospheric conditions of Earth, providing the basic necessities to support life involving an oxygen supply, temperature control system, pressurized enclosure, carbon dioxide removal, and protection from sunlight, solar radiation and tiny micrometeoroids. It provides astronauts with survivable conditions to be able to go on spacewalks. Spacewalks can also be called EVA, which stands for Extravehicular Activity. Spacewalks are a way for astronauts to work outside the spacecraft and can last between 5 to 10 hours maximum. It allows them to conduct experiments to understand more about space, repair the spacecraft from outside, aid in payload deployment, external inspection, etc. An independent anthropomorphic spacesuit or The Extravehicular Mobility Unit (EMU) is used for performing EVA. Now, how exactly are these space suits developed? A space suit can have as many as 16 layers, each one performing a different task to provide suitable and comfortable conditions for the astronaut.
Closest to the astronaut's skin, the cooling garment makes up the first three layers. This piece of clothing covers their entire body leaving the head, hands and feet. They have several tubes woven into them with water flowing through to cool the body. As the process of convection does not work in space this eliminates the chance of any evaporative cooling from sweating from happening, it is important that the body remains cool without having to rely on the body to produce sweat. A liquid cooling and ventilation garment (LCVG) has additional crush-resistant ventilation ducts which draws out the moist air from the wearer’s body, keeping them dry. Once circulated, the water returns to the Primary Life Support System where it is cooled in a heat exchanger before being recirculated. The PLSS uses the idea of sublimation cooling. Where the heat is ultimately transferred to a thin sheet of ice. Due to low pressure, the heat sublimates to water vapor and is then vented away from the suit. The ice sublimator consists of sintered nickel plates with microscopic pores which are sized to permit the water to freeze in the plate without damaging it. When heat needs to be removed, the ice in the pores melts and the water passes through them to form a thin sheet which then sublimates. Rate of sublimation is directly proportional to the amount of heat needing to be removed. The LCVG is primarily constructed of Spandex, Lycra or elastane with a nylon tricot liner. The tubes are made of Polyvinyl Chloride. A front zipper is then attached as well as connectors for attachment to the life support system. The next layer is the bladder layer, essentially one of the most important layers of the space suit.
The bladder layer contains gas to maintain the proper pressure dynamic and contains oxygen for the wearer to breathe in. The layer immediately above the bladder layer ensures that the bladder layer retains proper form for the astronaut; it is made from Dacron. The inflatable bladders fill the space suit with oxygen. The bladders will inflate automatically with low cabin pressure, they also can be manually inflated during entry to prevent the crew member from blacking out. Lack of pressure results in bodily fluids turning into gas. However a pressurised or inflated suit makes it hard to bend and complete tasks effectively. Oxygen is delivered from pressurized oxygen tanks in the backpack. But as pressure builds, the space suit stiffens resulting in the allowance of zero movement. To overcome this, developers have created breaking points at appropriate locations outside the bladder which makes the suits more bendable. The breaking points act as joints. Space suits are restricted by Neoprene-coated fibers. Most space suits operate at pressures below normal atmospheric pressure (14.7 lb/in2, or 1 atm). The bladder layer consists of thermally bonded, impermeable polyurethane-coated nylon to contain the pressurized oxygen in the space suit and prevent moisture transmission to the vacuum-exposed side of the suit, where it would cause uncontrollable cooling via evaporation. The materials are used to withstand the constant flexing while being pressurised, and abrasion from the relative motion of the layers of the suit. The restraint layer also withstands the stress of pressurization and helps maintain human form and keep the bladder from ‘ballooning’. The ripstop liner is a tear-resistant layer. The carbon dioxide exhaled by the astronaut is removed from the space suit by lithium hydroxide canisters in the suit’s life support backpack.
The next several layers are insulation and act like a thermos to help maintain the temperature inside the suit. Seven layers of aluminized Mylar materials provide insulation, followed by the outer layer made of fabric blends of Gortex, Kevlar, and Nomex materials and covered in reflective outer layers of Mylar or some other white fabric to reflect the sunlight. The thermal and micrometeoroid layer protects the astronaut from small, hypervelocity particle impacts and the thermal effects of solar radiation. This layer is made of ortho fabric which is woven to have white Gore-tex on the exterior and fire-retarding fibers with a ballistic-rated polymer ripstop on the interior. The Gore-Tex being slippery prevents friction build up between parts during excessive movement inside the space suit, its color helps limit absorption of solar energy. Aluminized polymer insulation layers maintain a comfortable thermal environment for the astronaut by reflecting the Sun’s energy out when in sunlight and the astronaut’s body heat in the suit when in shade. The Ortho fabric helps break up any incoming projectiles/ debris/ hypervelocity particles. These hypervelocity particles are turned into gas jets that are absorbed by a coating on the nylon layer.
Various components to aid mobility are also installed in a space suit such as bearings located at the arm, shoulder, wrist, and waist. Metal rings called disconnects are also used at the neck to attach the helmet, the wrist to attach the gloves, and at the waist to allow the astronaut to get in and out of the suit.
There are several other raw materials being used besides Spandex, Nylon Tricot, Urethane Coated Nylon, Dacron, Mylar, Gortex, Kevlar, and Nomex, Fiberglass is the primary material for the hard upper torso segment. Lithium hydroxide is used in making the filter which removes carbon dioxide and water vapor during a spacewalk. A silver zinc blend comprises the battery that powers the suit. Plastic tubing is woven into the fabric to transport cooling water throughout the suit. A polycarbonate material is used for constructing the shell of the helmet. Various other components are used to make up the electronic circuitry and suit controls.
The helmet is a large plastic, pressurized bubble that has a neck ring and a ventilation distribution pad. It also has a purge valve, which is used with a secondary oxygen pack. The vent pad directs oxygen from the Primary Life Support Subsystem and Hard Upper Torso to the front of the helmet. The helmet consists of a straw attached to a drinking bag. The visor shields the astronaut from the rays of the sun. As well as a camera that records the extravehicular activities. The MSOR assembly attaches to the outside of the helmet. This device is snapped into place with a chin strap consisting of a microphone and headphones for two way communications. It also has four small "head lamps" which shine extra light where needed. Helmets contain a small foam block used if astronauts feel the need to scratch their noses. The protective visor prevents the pressure bubble from being damaged. The sun visor has a special gold coating that works like the astronaut's sunglasses. Helmets and visors are constructed using traditional blow molding techniques. Pellets of polycarbonate are loaded into an injection-molding machine. They are melted and forced into a cavity which has the approximate size and shape of the helmet. When the cavity is opened, the primary piece of the helmet is constructed. A connecting device is added at the open end so the helmet can be fastened to the hard upper torso. The ventilation distribution pad is added along with purge valves before the helmet is packaged and shipped. The visor assembly is similarly fitted with "head lamps" and communication equipment.
The control module of the space suit is attached to the chest and lets the astronaut monitor the suit's status and connect to external sources of fluids and electricity. It consists of all the operating controls as well as a visual display panel. A silver zinc, rechargeable battery which operates at 17 volts is used to power the suit. The control module is integrated to the warning system found in the upper hard torso to ensure the astronaut is aware of the status of their space suit’s environment. The suit is connected to the orbitor via an umbilical line. The key components of the control module are built in separate units and then assembled. In addition to that, since an astronaut cannot see the contents displayed on the control module, they strap a mirror around their wrist to be able to view the control module.
The lower torso assembly is made up of the pants, boots, brief unit, knee and ankle joints and the waist connection. It is composed of a pressure bladder of urethane-coated nylon. A restraining layer of Dacron and an outer thermal garment composed of Neoprene-coated nylon. It also has five layers of aluminized Mylar and a fabric surface layer composed of Teflon, Kevlar, and Nomex. This can be made shorter or longer by adjusting the sizing rings in the thigh and leg section. The boots consist of an insulated toe cap to improve heat retention. The arm assembly is also adjustable like the lower torso assembly. The gloves of the space suit contain miniature battery-powered heaters in each finger. The rest is covered in padding and an additional protective outer layer. The hard upper torso is made of fiberglass and metal. This is where mostly all the components of a space suit attach to, the gloves, helmet, control module, life support system display, and the lower torso. It includes oxygen bottles, water storage tanks, a sublimator, a contaminant control cartridge, regulators, sensors, valves, and a communications system. The ventilation garment is near the astronaut’s feet and elbows to vent out oxygen, carbon dioxide and water vapour. The various layers of synthetic fibers in the lower torso are woven together and then cut into the appropriate shape. Connection rings are attached at the ends and the various segments are attached. The gloves are fitted with miniature heaters in every finger and covered with insulation padding. The hard upper torso has four openings where the lower torso assembly, the two arms, and the helmet attach. Additionally, adapters are added where the life support pack and the control module can be attached.
The life support backpack is what provides the astronaut with livable conditions. It supplies oxygen for breathing, and refrigerated water for cooling. It also pressurises the suit and removes contaminants. It also has a communication-telemetry set, controls to operate it, and devices to monitor its functions. The life support pack, with its controls, weighs 104 pounds; it is 26 inches high, 20.5 inches wide and 10.5 inches deep. It is powered by a 16.8-volt silver-zinc battery. A fiberglass cover protects the pack against micrometeoroids. The life support system consists of five subsystems, the primary oxygen supply, oxygen ventilating circuit, water transport loop, feedwater loop, and space suit communication system. A thermal insulator made of fire-resistant Beta cloth and aluminized Kapton covers the pack to restrict heat leakage in and out. A similar insulator is used to cover the oxygen purge system. The control module has switches for the life support pack's water pump and oxygen fan, four-position communication selector switch, a radio volume control, an oxygen quantity gauge, and warning indicators. The primary oxygen supply supplies oxygen to the wearer for breathing and pressurises the space suit. The oxygen ventilating circuit circulates oxygen throughout the space suit and purifies recirculating oxygen. It also cools the astronaut by evaporating the moisture accumulating on their skin. The oxygen entering the backpack passes through a lithium hydroxide cartridge, where the chemicals trap the exhaled carbon dioxide. It then goes through a charcoal bed that removes trace contaminants including body odour. The oxygen flow is cooled by a porous-plate sublimator, a self-regulating heat rejection device. The excess water produced by the astronaut through respiration and perspiration is removed by a water separator which is stored outside the bladder layer. A fan in the backpack recirculates oxygen to the space suit.The water transport loop is used to cool the astronaut by removing metabolic heat or any heat that leaks into the suit. A battery-operated pump continuously circulates chilled water through a network of plastic tubes woven in the cooling garment. To control the cooling, the astronaut can use a valve on the pack and select any water temperature range, from 45° to 50°, 60° to 65°, or 75° to 80°. This valve diverts water past the sublimator. The feedwater loop supplies expendable water, stored in a rubber bladder reservoir, to the heat-rejecting porous-plate sublimator. Most of this is held in the main reservoir, while the rest is held in an auxiliary tank. Suit pressure against the bladder forces water into passages between the sublimator's heat transport fluid passages and its metal plates, which are exposed to space vacuum. The ice layer formed on the porous plates prevents pressurised water from flowing through the metal pores.
The condensed water from the oxygen ventilating system is accumulated and collected outside the reservoir bladder. This expendable water or feedwater is then replenished from the lunar module supply. Refiling the bladder will force the condensed water to the LM waste management system. The oxygen purge system is connected to the suit with a separate umbilical and is essentially designed for backup used in the event of any emergencies such as loss of suit pressure and oxygen depletion. The OPS can supply either an open-loop purge flow or makeup flow directly to the suit. In full purge mode it provides a 30-minute flow at a rate of 8.3 pounds of oxygen an hour, this helps fulfil the breathing and cooling requirements, vacuuming out the carbon dioxide build up as well as defogging the helmet. When used in conjunction with the Buddy Secondary Life Support System (BSLSS), the OPS flow is reduced to 4.2 pounds per hour, which permits emergency operation for up to 75 minutes. The OPS is mounted separately on top of the backpack and it is operated by a lever, which is attached to the pack’s remote control unit. A battery powered, temperature- controlled heater warms the rapidly expanding oxygen to prevent subzero oxygen temperatures at the space-suit flow inlet. The buddy secondary life support system, BSLSS for short, consists of two flexible hoses which are used to feed cooling water from one astronaut’s life support system to another’s. However due to the buddy system taking over the cooling system, emergency oxygen flow from the oxygen purge system can be slowed down from 30 minutes to 60 - 90 minutes. One hose carries water into the suit and the other out of it. A tether snaps onto the space suits preventing the hoses from reaching their full length. Water and tether lines are stowed in a pouch which is carried on the PLSS. The space suit communication system provides primary and backup dual voice transmission and reception, telemetry transmission of physiological and backpack performance data, and an audible warning signal. The operation of the communication system in dual mode provides astronauts with duplex communication privileges with other astronauts. A dual volume control permits adjustment of receiver sound level. Any telemetry information is transmitted without interrupting or interfering with voice communication. Nine telemetry channels transmitted to the LM carry suit operational and environmental data, oxygen supply pressure, suit water inlet temperature, sublimator oxygen outlet temperature, suit pressure, feedwater pressure, suit water temperature rise, CO2 partial pressure, and backpack battery current and voltage. The tenth channel transmits an electrocardiogram. Indicators on the remote control unit provide astronauts with a visual warning of high oxygen usage rate, low suit pressure, low ventilation flow and low feed water pressure. An audible tone sounds to alert the astronaut that an abnormal condition exists. Flags trip into view in the indicator windows, identifying the problem so that the astronaut can take corrective action.
Due to weightlessness in space it is difficult to move around. Newton’s third law of motion states that when an object exerts force on another object, that object will exert a force of the same magnitude in opposite direction. Meaning astronauts have to push themselves against an object to be able to move forwards. Science.howstuffworks states that “Gemini spacewalking astronauts reported great problems with just maintaining their positions; when they tried to turn a wrench, they spun in the opposite direction.” To solve this issue, spacecraft are now being equipped with footholds and hand restraints. Moreover, NASA has developed some gas-powered rocket maneuvering devices to allow astronauts to move freely in space without being tethered to the spacecraft. A nitrogen - gas propelled unit has been fitted on the backpack, called the Simplified Aid for Extravehicular Activity Rescue (SAFER). Astronauts may control SAFER with a joystick.
Astronauts are required to wear their space suits hours before a spacewalk. This is because astronauts have to breathe in pure oxygen to get rid of Nitrogen. If the nitrogen wasn’t removed beforehand the astronauts would feel pain in their shoulders, elbows, wrists and knees due to the formation of gas bubbles in their body. This pain is called “bends” because it mainly affects joints or parts where a person is required to bend.
We can now identify the different layers of the space suit, the ortho fabric layer, aluminized insulation, micrometeoroid liner, pressure garment restraint, gas retention bladder, liquid cooling ventilation garment, and the comfort liner. The space suit consists of a sublimator, the contamination control cartridge, drinking bag, caution and warning systems, vent flow sensor, backpack life support system, helmet, communication carrier assembly, primary O2 tanks, extravehicular visor assembly, visor, secondary O2 tanks, hard upper torso, Phase VI gloves, mirror, display and control modules, electrical harness, liquid cooling ventilation garment, and the thermal micrometeoroid garment.
Problems and Solutions
Mechanical Counter Pressure Suit
One of the biggest problems faced by astronauts during extravehicular activity is lack of flexibility and mobility. Wearing a 280 pound pressurised suit with a limited amount of movement can be quite exhausting.
Mechanical counterpressure suit was designed as an experimental suit. The basic idea of this is that these
suits provide mechanical pressure rather than air pressure like in conventional space suits.
However in order for it to work the mechanical counterpressure suit must exert a constant and equal amount of
pressure over each part of the body to prevent the bodily fluids from turning into gas. There are many
disadvantages to such a suit, for one it does not ensure that all parts of the body receive the same amount of
pressure as the body moves, with a gas pressurised suit however, the regulator guarantees every inch of the
body receives the same pressure. Being skintight, these space suits lack comfort which in turn decreases
mobility and efficiency.
Electroactive polymers can be used to detect any change in the wearer’s position and translate that to a
regulator to ensure pressure maintenance. Electroactive polymers are a type of polymer that upon stimulation
from an electric field, change size or shape. A device converting motion to an electric signal can be used,
these types of devices work on the basis of triboelectric nanogenerators. “Triboelectric nanogenerators are
effectively small-scale, flexible, and sometimes stretchable, energy generators that convert movements in our
surroundings such as human motion, machine vibrations, vehicle movements, wind and wave energy into
electricity,” said Dr Ishara Dharmasena, of Loughborough’s School of Mechanical, Electrical and Manufacturing
Engineering. “Tengs can be constructed using low cost, lightweight, non-toxic and flexible materials,” said
Dharmasena. Due to their versatile nature they can be shaped into any size and form. This can be implemented
between the layers of the counter pressure suit where the Triboelectric nanogenerator will be able to detect
movement from the wearer. However if the wiring is not properly insulated it may pose a threat to the
astronaut. This method also faces problems due to excessive swelling/edema in parts of the body, however this
issue was resolved by using pads.
These suits also have to be tailored according to the subject’s size which increases costs and becomes a very
time consuming process. The counterpressure suit consists of 6 layers. Each layer needs to be donned in the
correct order starting with the slip layer, immediately over that is the torso pressurizing breathing bladder
assembly. The helmet-bladder restraint garment is used to limit bladder expansion and to prevent the helmet
from rising. The torso section was made to fit individual subjects and was constructed of Nomex, the helmet is
securely put in place by a split ring baseplate. For proper donning, four zippers were required in the front,
back, and the midlines. There were some circumferential size adjustments being implemented at the medial
anterior lace take-ups. A secondary helmet-bladder restraint is also used to assist the primary helmet-bladder
restraint. This layer is a full body garment where the torso section is made of nomex whereas the limb
segments are made of bobbinet. The arm balance layer is used to maintain pressurization on the arms with that
of the legs. Antimicrobial agents are being added to the materials of a space suit to kill any bacteria or
viruses expelled during respiration/ sweating.
| Characteristics | Counter pressure suit | Gas pressurized suits |
|---|---|---|
| Safety | High | Medium |
| Leg and torso flexibility | High | Low |
| Glove and arm flexibility | High | Low |
| Maintainability | High | Low |
| Adaptability | Used for IVA and EVA, Microgravity | EVA – High IVA – Medium |
| Cost | Low | High |
| Donning | 10 minutes | 20 minutes |
| PLSS size | 70% of EMU PLSS | -- |
| Dust resistance | High | Low |
| Contamination control | High | Low |
| Mobility | High | Low |
| Bulk | Low | High |
| Weight location | Distributed | Back (PLSS) |
| Gas Leakage | Low | High |
Pros:
- High mobility, maintainability and flexibility
- Low cost of production
- Reduced weight due to reduced size of PLSS and removal of additional bulk.
- Low donning time
- Low gas leakage
- High adaptability
- High safety
Cons:
- If insulation isn’t proper, the wearer might be affected.
- Needs to be custom designed according to the size of each astronaut.
- Maintaining constant pressurized conditions throughout the suit may be difficult.
- Making each suit according to the needs of each individual can be time consuming and not very cost effective.
- Since the cooling garment is removed, the suit relies on the process of evaporation through sweating to cool down the astronaut eliminating a chance for them to regulate cooling temperature.
- Might causing swelling
- Blood pooling is caused if pressure isn’t maintained.
LED Display
Another thing that can be added is an LED helmet. LED (light emitting diodes) displays contain red, blue and green LEDs, varying the brightness of each of these diodes can jointly form an image. The red, blue and green LEDs combine to form one pixel. Helmets with display peripherals will greatly help astronauts as they can display the contents of the control module, a checklist/ instructions, heart rate, and some crucial and critical information. As more tasks are crossed off the checklist, a count at the bottom of the checklist can decrease by one per task. This can be possible through a controller unit for example a microprocessor, these controller units will interface with the LCD unit, heart rate monitor unit and provide the necessary data or information on the LCD screen. An LCD screen can also be used instead of an LED. A heart rate monitor can be used to detect the pulse or heart rate of the wearer. The count for the beats per minute can be detected from the monitor and displayed on the LED/ LCD display helmet. The transmitter will pick up an electric signal from the detector and send an electromagnetic signal to the LED receiver. Optical sensors are used to detect the blood flow in a person’s veins. This LED display can be placed between the pressurized bubble and the visors, or can be integrated in the helmet itself.
The following is a circuit board of a LED interfacing with a 8051 microcontroller. The Intel 8051 belongs to the MCS-51 family of Intel microcontrollers. AT89S51 is a microcontroller coming from the family of 8051 microcontrollers. The circuit board shows the AT89S51 interfaced with 8 LEDs to Port3 of the microcontroller. All the LEDs are connected to resistors to limit the amount of current.
Block Diagram
Pros:
- Helps display critical information
- Knowing your own heart rate can beneficial
- The instructions for each task can help guide the astronaut and eliminate any chance for human error.
- Easier to read than from a mirror reflecting the contents of the control module.
Cons:
- The instructions for specific activities need to be changed before every activity.
- It can be quite distracting unless the contents can be hidden upon the wearer’s command.
- A lot of precautions need to be taken while cleaning the LED displays.
- Implementing this can be expensive
Trajectory Detection System
Astronauts can use a device to detect any incoming trajectory to prevent themselves from being hurt. The NASA Johnson Space Center (JSC) has developed a trajectory detection system, informing them of the exact coordinates and the time from impact. The system consists of multilayer sensor panels covered with piezoelectric polymer film, this system can be used to cover small or large areas by electronically daisy-chaining and assembling it. This film works by generating an electrical potential at the location and time of the impact. The circuitry placed within the layers detects this potential, in turn detecting the impact itself. The raw data is processed by the system with the help of a time discrimination analysis, this determines the trajectory of an object. The piezoelectric polymer film consists of a characteristic in which when it is impacted, it develops an electrical voltage, this voltage is being detected. A computer is used that communicates with the electronics, processes raw data, and displays this data to the user. This system is a convenient way to safely determine the incoming trajectory of projectiles. It uses a communication and control subsystem. These sensors work well in vacuum conditions, ambient conditions, or under pressure conditions, with that they can also exist passively with the help of the piezoelectric effect. Temperature does not limit the efficiency of the piezo film allowing the sensors to be 100% accurate. Such systems can be very useful when trying to detect projectiles that may not seem obvious immediately in order to prevent any large damage that might take place.
Pros:
- Helps detect trajectory of projectiles to minimize damage.
- Lightweight system and requires low power wattage.
- Almost 100% accurate
- They are sensitive to a wide range of impact energies and velocity.
Cons:
- Might be expensive to implement
- Even if the trajectory of the projectile is detected, they might not be able to take action quickly if the projectile is a hypervelocity particle.
Threat Detection System
In the event of a space suit’s communication system to fail as they are faced with any kind of danger such as a hazardous damage to a circuit board, a system can be implemented where a light on the astronauts arm section turns to red, orange or yellow according to the threat level, these light adjustments can be made in accordance to the heart rate of the wearer or on their own regard. The system’s color can be changed by a simple touch on the device, or when the wearer’s heart rate exceeds a particular range. This device in a way acts as a touch lamp, the basic science behind the touch lamp is pretty simple, they work on the principle of capacitance, this refers to the amount of charge that can be soaked by the device. A component called capacitor is used, these components store varying amounts of charge. When a person comes in contact with a touch lamp, the capacitance is altered. This alteration is detected by the lamp and can be switched on or off accordingly. Now since sound waves do not travel in space, these lamps would be useless if they emitted a large sound for another astronaut to hear. Instead, this problem can be solved by emitting a color change in the other astronauts arm light as well. However the basic medium for this would be connectivity. The basic idea of this is that if one’s space suit’s system’s color is changed, the other’s as well as the crew members inside the spacecraft will receive this signal and the color of the other astronaut on the space walk’s space suit’s system’s color changes as well.
Pros:
- Astronauts can communicate even after the event of their communication system failing takes place.
- It is extremely easy to set up.
- Inexpensive
Cons:
- Might be hazardous if not insulated properly.
Model Components
Patch1
Patch2
Heart Rate Monitor System
Arduino Microcontroller Board
Board Topology
Arduino Connector Pinout
Arduino Microcontroller Board Outline and Mounting Holes
Mechanical Counter Pressure Suit Prototype
Recreated from
Heart rate monitor system
This is a prototype of how the heart rate of an astronaut would be displayed on the LCD of a helmet. It was calibrated to display a heart rate of 70 – 100 and is not a functioning model. To get a clear image of the idea refer to the following video of a pulse oximeter, measuring the blood oxygen and heart rate of a person.
LED Light Showcase
As the heart rate of a person exceeds a recorded BPM, the red LED light will begin to illuminate on the astronaut’s forearm. The code was manipulated for the heart rate shown to exceed moderate exercising heart rate. Here is a visual representation of what it might look like:
Code for the Heart Rate Monitor - Arduino Microcontroller Board
#define USE_ARDUINO_INTERRUPTS true // Set-up low-level interrupts for most acurate BPM math.
#include PulseSensorPlayground.h // Includes the PulseSensorPlayground Library.
#include LiquidCrystal.h // Includes LCD Library.
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
// Variables
const int PulseWire = 0; // PulseSensor PURPLE WIRE connected to ANALOG PIN 0
const int LED13 = 13; // The on-board Arduino LED, close to PIN 13.
int Threshold = 534; // Determine which Signal to "count as a beat" and which to ignore.
int btnpin=1; //Set the digital pin 1 to button
unsigned long debounceDuration = 50;
unsigned long lastTimeButtonStateChanged = 0;
byte lastBtnState = HIGH;
bool LEDOn = false;
// Creates an instance of the PulseSensorPlayground object called "pulseSensor"
PulseSensorPlayground pulseSensor;
void setup() {
Serial.begin(115200); // For Serial Monitor
pinMode(btnpin,INPUT); //Set digital 2 port mode, the INPUT for the input
lcd.begin(16, 2);
// Configure the PulseSensor object, by assigning our variables to it.
pulseSensor.analogInput(PulseWire);
pulseSensor.setThreshold(Threshold);
pinMode(LED13, OUTPUT);
// Double-check the "pulseSensor" object was created and "began" seeing a signal.
if (pulseSensor.begin()) {
//This prints one time at Arduino power-up, or on Arduino reset.
lcd.setCursor(0, 0);
lcd.print("Heart Rate");
}
}
void loop() {
// Calls function on our pulseSensor object that returns BPM as an "int".
int myBPM = pulseSensor.getBeatsPerMinute();
// "myBPM" hold this BPM value now.
// Check the button is pressed. If button is pressed turn on/off red led light
unsigned long timeNow = millis();
if (timeNow - lastTimeButtonStateChanged > debounceDuration) {
byte buttonState = digitalRead(btnpin);
if (buttonState != lastBtnState) {
lastTimeButtonStateChanged = timeNow;
lastBtnState = buttonState;
if (buttonState == HIGH) { // button has been released
LEDOn = ! LEDOn;
}
}
}
if (myBPM == 0){
lcd.setCursor(0, 1);
lcd.print("Hold sensor"); // Ask to put finger on sensor
lastBtnState = HIGH;
LEDOn = false;
digitalWrite(LED13, LOW);
}
if (LEDOn) {
if (myBPM > 0)
myBPM = (rand() %
(115 - 101 + 1)) + 101; //Test high pulse and turn on Red led
}
else {
if (myBPM > 0)
myBPM = (rand() %
(90 - 70 + 1)) + 70;
}
if (pulseSensor.sawStartOfBeat()) { // Constantly test to see if "a beat happened".
if (myBPM > 100){
digitalWrite(LED13, HIGH);
}
else{
digitalWrite(LED13, LOW);
}
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Heart Rate");
lcd.setCursor(0, 1);
lcd.print("BPM: "); // Print phrase "BPM: "
lcd.print(myBPM);
}
delay(2000);
}