This is a paper on life support and engines that can take people to mars. Limit 2500 words
| The National Aeronautics and Space Administration-NASA, has been handed a lofty goal. President Obama and even president-elect Donald Trump have encouraged the recently floundering organization to reach Mars. NASA has many challenges facing it to reach this ambitious goal, including the ability to support the crew for the long trip through deep space. The crew will face many challenges including the psychological strain of being in isolation as they travel through deep space, radiation exposure, and the day-to-day challenges of staying alive in space. NASA will need an engine to take their spacecraft, and the life support to sustain the crew inside. There are many engines available or on the near-horizon, and each have advantages and disadvantages. Each engine type can contribute to solutions for the different challenges NASA faces.
There are many different types of engines being explored by NASA, from near-horizon technology to technology that has already taken people to Mars. NASA started with the Hall thruster. This was created by Aerojet Rocketdyne, and used the same technology the Dawn Spacecraft used. However, this ion propulsion, unlike the Dawn Spacecraft, was rated to up to 13kW, a vast improvement over the Dawn Spacecraft's 2.6kW. The most likely, most well-researched near-horizon engine is the Variable Specific Impulse Magnetoplasma Rocket (VASIMR). This engine would take crews and cargo to Mars in a short 39 day span. The implications for this are incredibly promising for fuel and the resulting weight and life support savings.
The VASIMR engine is classified as an Ion propulsion engine, although its parent company classifies it as an electric thruster. Ad Astra, the company that designed the rocket engine, explains how it works: “gas such as argon, xenon, or hydrogen is injected into a tube surrounded by a magnet and a series of two radio wave...couplers[.] The couplers turn cold gas into superheated plasma and the rocket’s magnetic nozzle converts the plasma thermal motion into a directed jet.” There are two couplers. In the first, the gas is turned into plasma by ionization-that is, an electron is removed from the atoms of gas. When this process is complete, the gas is called “cold plasma”, although, as Ad Astra points out, it is hotter than the surface of the sun, 5800 Kelvin. In the second coupler, the plasma is superheated to over 10 million Kelvin. The ions are then pushed through the nozzle, resulting in thrust.
The VASIMR has several advantages over other engines. The first is that the engine could reduce our time to Mars to just 39 days. This would drastically reduce the needs for the spacecraft and crew for their travel time through deep space. The longer astronauts spend traveling in a spacecraft, the more supplies that are are needed. This means the craft would be carrying more food, more fuel, and more life support. To get to Mars that much faster would mean less weight would have to be packed into the spacecraft for the trip-less life support is needed, less food has to be packed, and all this allows NASA to concern themselves more with the long-term stay on Mars once the crew get there. The VASIMR engine can also handle large power inputs, which means it can then output large amounts of thrust. More thrust means the VASIMR engine can used in the future for “moving large payloads around low Earth orbit, transferring payloads from the Earth to the Moon, and transferring payloads from...Earth to the outer solar system.” (Ad Astra, n.d.) This means VASIMR can handle the kind of weight it would take to get to Mars and can be inserted into various needed transfer orbits. This would be the most likely strategy to get to Mars.
The VASIMR engine has not yet been tested due to certain drawbacks. One of these concerns is how it will be powered. The VASIMR engine is rated to 200kW. (Ad Astra, 2008) This is significantly higher than other ion propulsion engines currently being used, such as the Dawn Spacecraft, which draws a comparatively small 2.6kW. (Fecht, 2016) The more high-powered the electric thruster, the more power they draw. Generating that much electricity may require new innovation that hasn’t yet been designed. Two options Ad Astra are discussing includes Solar and Nuclear Power. Nuclear Thermal Power has a low specific impulse, however, when paired with the VASIMR technology, travel times could be drastically reduced, and payload mass could concurrently be increased. NASA is hoping to test the VASIMR by 2020.
Chemical engines, however, have been the most used on past trips to Mars. Mariner siz and seven were on chemical engines and have taken in excess of 200 days to arrive. Chemical engines got the Mariner and Mars Rover missions to mars in eight to nine months.
Ion propulsion engines are already being used-though none so powerful as the VASIMR engine. NASA’s Dawn Spacecraft uses Ion Propulsion. However, this spacecraft draws considerably less power than VASIMR. While VASIMR is rated for about 200kW, NASA’s Dawn Spacecraft’s thrusters are rated to about 2.6kW. The higher power would mean that VASIMR travels much faster than the Dawn mission could be.
Every engine has advantages and disadvantages. A disadvantage to VASIMR is that it’s not ready to be used yet. The chemical propulsion example, of course, has the longest time to travel. 200 or more days would be a long time for a crew to be exposed to deep space and the associated dangers; radiation, the need for life support, and the incumbent psychological challenges of being in space. Naturally, there are advantages as well. The VASIMR would save time, and would therefore require less life support, which is weight that can be given to other resources including those that would be needed to establish long-term habitation on Mars.
The hardest challenge to meet would be life support. Boen, (2013) defines life support as "a group of devices that allow people to survive in outer space." Life support for the International Space Station currently includes systems like the wastewater recovery system and the oxygen generation system. Traveling through deep space to Mars for 200 days or more, there would need to be enough water, food, oxygen, and carbon dioxide (CO2) filtering to provide for the entire crew. This could entail five to seven people, or Elon Musk’s ambitious one hundred. VASIMR would vastly improve on this requirement, with a travel time of only 39 days. This would limit the isolation factors astronauts would be exposed to, as well as their time in the radioactive environment in deep space. VASIMR's short travel time also reduces how much life support would be required on the trip, since it would have to support the crew for only about 39 days, with some extra as a contingency.
Marshall Spaceflight Center is currently working on this problem. Marshall designed the life support that is currently used on the ISS. In their development and testing research, Marshall Spaceflight engineers are testing a "waste water processor that uses some of the technologies used on the International Space Station." (Boen, 2013) The difference with this kind of processor is that it would be used in a habitat on another planet. It would be designed to recover more water from the atmosphere, as humans would obviously be further away from emergency re-supply missions and would most likely be on the planet longer. Some technologies that will carry over, however, would include the ability to process urine and atmospheric humidity. The improvements would include the ability to also process "Waste water from taking showers, washing clothes, and other hygienic activities." (Boen, 2013)
NASA Ames discusses the fact that Advanced Life Support technology must be developed to ensure successful long-term habitation on Mars. Ames' Advanced Life Support technology has set the following objectives: "Develop technologies that will significantly reduce the resupply of consumables and increase self-sufficiency. [And] Develop advanced life support subsystems to sufficient Technology Readiness Levels (TRL) for inclusion in integrated system tests in ground testbeds and in flight." The ultimate goal for Ames is to limit re-supply missions, since a Mars crew will be incredibly far from home. They will also be developing subsystems that must be ready for NASA to deem the mission technologically advanced enough to be included on the next integrated system, or spacecraft. Ames researchers reach this objective by proving their technology in testing on the ground, and then in space. Some technologies these teams are working on include new and "improved physico-chemical technologies for atmosphere revitalization, water recovery, and waste processing/resource recovery; biological processors for food production; and systems modeling, analysis, and controls associated with integrated subsystems operations." (Dino, 2008) In other words, Ames Research Center is improving the way oxygen and carbon dioxide are processed in and out of the atmosphere in a long-term spacecraft, and in a habitat on Mars.
Another resource that will have to either be brought, saved, or made, will be water. The spacecraft will have to recover water, as it cannot all be packed. Marshall Spaceflight Center is working on this alongside NASA's Ames Research Center. Both groups of research centers realize that water will be critical to long-term travel and life on Mars. The water on the ISS is already recycled. What NASA Ames and Marshall are putting together would recycle more, if not all, of the water that is used. Long-term habitation further away from earth demands more water than any other mission before. For water recovery, Ames Research Center has designed the "Vapor Phase Catalytic Ammonia Removal (VPCAR)." (Dino, 2008) Advantages of the system include the mass savings. The unit, with the weight needed to power it, and how much volume it takes, is "five times better than the current state-of-the-art ISS...water recovery system." (Dino, 2008). For water processing, Ames is leading a group consisting of several agency teams from many locations who are developing "solid waste processing and resource recovery technologies." (Dino, 2008) Ames also developed "the waste oxidation/incineration system" and tested it at Johnson Space Center over 91 days to great success. (Dino, 2008) The gas produced by the incineration was tested for trace contaminants, and the composition of different potentially toxic gasses was "significantly less than the Spacecraft Maximum Allowable Concentration...values" (Dino, 2008). Ames is also researching a way to capture the contaminants found in the gasses and converting them into products that can be used, which would save more weight.
For air revitalization, NASA Ames designed the "Temperature Swing Adsorption CO2 Compressor (TSAC)." (Dino, 2008) This will "close the air loop in [the] spacecraft." (Dino, 2008) This technology could save up to 2000 pounds a year in supplies that would otherwise have to be resupplied. Much like VPCAR, this technology has developed to the point that it is a very likely candidate to be included in the final system for traveling to Mars.
The Apollo missions, which were the last to send astronauts to deep space, only required 14 days of life support, with a small amount of contingency supplies. Per day the average human goes through .84 kilograms of Oxygen and 3.53 kilograms of water. One astronaut would produce about one kilogram of carbon dioxide, and .11 kilograms of solid waste. Assuming an all-male crew of five, the spacecraft would have to provide for 3402 calories per day, per crew member, for the length of the trip.
The VASIMR has obvious advantages. For food for thirty nine days, at 3,402 calories a day, for five crew members, is 663,390calories for the trip. The spacecraft powered by VASIMR would have to provide 163.8 kilograms of oxygen; with the proper air revitalization system, oxygen could be harvested from carbon dioxide and through the hydrolysis of water, and so wouldn't need to be packed onto the craft. There would have to be some oxygen stored on board as a redundancy. This could be cryogenically stored as a liquid in tanks onboard, assuming budget is not a constraint. For a crew of five, on a thirty-nine day mission, there would be about 195 kilograms of CO2 produced by the crew. The spacecraft would also need to accommodate 21.45 kilograms of waste. The daily water requirement would also be a consideration-humans need an average of 3.53 kilograms of water per day. Carrying 688.35 kilograms of water would be a costly weight requirement. This brought about Ames Research Center's improved atmosphere and waste water revitalization system. This allows the spacecraft to recycle water that is used and produced. Unused Water can be captured and recycled by the new Air revitalization system and water recovery system, as can humidity produced by the crew's regular breathing, showering, and daily activities.
On a chemical propulsion rocket, the life support would have to support the same crew, but for significantly longer. At about thirty days in a month, the crew would be in space for 270 days. This would mean at least 1,350 kilograms of Carbon dioxide created by the crew that would then have to be scrubbed or separated into components. The crew would need at least 1,134 kilograms of oxygen, either supplied or processed or some combination. The waste management system would have to handle at least 148.5 kilograms of solid waste. Either onboard or recycled, the spacecraft crew would require 4765.5 kilograms of water. These numbers are significantly higher than the VASIMR engine. This means that's a lot more weight that would need to be on board, and more fuel that would be needed, and more weight in fuel that would have to get off the ground. Chemical propulsion also doesn't offer the savings on fuel that the VASIMR does. This would increase the crew's time in space and the resulting exposure to radiation and psychological strains in space.
Overall, the VASIMR engine promises a quick delivery to Mars with savings on fuel and life support costs. While the chemical propulsion could get humans to Mars in a reasonable amount of time, the crew would still be exposed considerably longer to radiation and psychological strain. However, the chemical propulsion engine is already available. Each engine has advantages and disadvantages that could both help or hurt NASA's ultimate goal of getting people to Mars and establishing a permanent habitat there.
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