Implications of Nuclear Powered Space Systems, Capstone Project Example
Words: 14088Capstone Project
The use of nuclear energy in space travel, while evolving rapidly, has been a mute point of discussion in the media and among the public, overshadowed by fears of nuclear holocaust, fallout and other destructive themes. The current consensus among space travel epistemologists is that in order for man to take the next step in space exploration, nuclear energy will have to play an integral part of the process. The following research delves into the technological, social, environmental, and political aspects of space exploration. Appropriate statistical analysis methods are assessed including all techniques in data collection, review, critique, interpretation and inference in the aviation and aerospace industry. In addition human factors influencing the development and design of nuclear power systems used in space exploration are reviewed in all aspects of the aviation and aerospace industry, including unsafe acts, attitudes, errors, human behavior, and human limitations as they relate to the aviator’s adaption to the space environment. The purpose of this research is to assess the current state of nuclear energy and its place in space exploration as well as the projected future of nuclear energy and the aerospace industry.
Keywords: nuclear energy, space exploration, technological, social, environmental, political
This proposal examines the current implications that are associated with Spacecraft nuclear power systems. Since the beginning of the Space Race, the United States has led the scientific community in the exploration of space. Spacecraft launched from the U.S. have orbited the Earth, traveled to, and landed on the Moon, Mars, and even traveled beyond the orbit of Pluto. A key factor in continuing the vast exploration to distant worlds is the ability to safely harness and control the use of radioisotope power systems (RPS’s). I propose that nuclear systems are safer more reliable and will be the only current technology capable of reliable deep space out of sunlit area exploration. Spacecraft designed for long duration exploration to distant locations cannot rely on solar or chemical fuel sources for electrical power.
The initial development and testing of nuclear powered space systems dates back to the early 1950’s. It is paramount that the studies and research completed in the past be continued in order to develop spacecraft power systems for the future. The way that RPSs work is by converting heat generated by the natural decay of radioactive material, Specifically, Pu-238 to electrical energy (National Research Council, 2009). RPSs are designed to be rugged compact systems that provide reliable long lasting electrical power in the harshest of environments making them ideal for many space missions. Contrary to initial thought these systems are not nuclear reactors and they do not use nuclear fission of fusion to produce energy. These systems use the heat produced from the decay of plutonium.
Since the initial launch of Transit 4A, the world’s first nuclear powered satellite designed to serve as a navigational system for ships and aircraft, a total of 26 spacecraft have launched and operated using RPSs. A new nuclear power system called the Advanced Stirling Radioisotope Generator (ASRG), is currently being studied and developed in order to provide increased power production efficiency. Plutonium-238 (Pu-238) production ceased in the United States in the late 1980’s due to the shutdown of production facilities by the Department of Energy (DOE) (National Research Council, 2009). Pu-238 is not suitable like Pu-239 for use in nuclear weapons. Currently the U.S. remaining supply came from a purchase in 1994 from the government of Russia to be used specifically for the development of RPSs. This limited supply has put a large problem into the development of future systems. One option is to reestablish production facilities however this will likely be a very expensive venture and could have the potential to ignite another arms race.
Implications of Nuclear Powered Space Systems
Statement of the Project
Over the past six decades, nuclear powered space exploration has developed exponentially in both aspects of technical and scientific epistemology. Since the first man-made satellite was launched in 1957 by Russian Scientists, which inevitably triggered the 1960’s U.S. and Russian “Race to the Moon,” monumental progressions have taken place in nuclear energy. Some of these expansions were not met with open arms by the public, as the U.S. Department of Energy documented in their publication “Atomic Power in Space; A History,” “growing concerns about ever more destructive bombs and fears of fallout contamination led to concerted efforts to control testing and find peaceful uses for nuclear energy (U.S. Department of Energy, 1987).” The authors note that the response to this growing concern was the establishment of the Atomic Energy Commission (AEC), successor to the greatest weapon development project of all time.
The AEC’s work resulted in the bulk of the funding for many of the projects that would be the ground floor for space exploration and the utilization of nuclear power to enhance these projects. The radioisotopic program was designed specifically to develop peaceful use of nuclear energy as a form of nuclear auxiliary power missions into space. This program was able to benefit from the many nuclear weapons designed under the AEC, specifically as it relates to the resource of plutonium, which the AEC had made available in mass quantities (National Aeronautics and Space Administration, 2012). In recent years advancements have been made to the point that astrophysicists and space epistemologists have developed a deeper understanding of the workings of space and space travel. Based on decades of experimentation and data gathered from numerous missions, popular consensus among these experts is that if the U.S. is to take the next step into space exploration, nuclear energy will have to be a part of that equation.
Students will be able to apply the fundamentals of air transportation as part of a global, multimodal transportation system, including the technological, social, environmental, and political aspects of the system to examine, compare, analyze and recommend conclusion.
Based off of research conducted, all aspects of aeronautics and fundamental air travel will be assessed as they relate to the implication of nuclear powered space systems. Propulsion is a fundamental aspect of space launch and aviation. Improvements made within aviation and space travel, as well as gains made in aviation research can be utilized throughout the greater multimodal transportation system. This project will demonstrate the benefits of implementing nuclear power in space travel. This project will address the technological aspects of implementing nuclear energy in aeronautical systems in its search for potential areas for improvement and future development. The social implications of nuclear space power systems will be addressed by this project in its examination of how the systems are currently being integrated into space exploration missions. The environmental implications will be addressed by assessing the safety ramifications of nuclear energy use. space travel using nuclear power systems will need to use advanced technological systems that are designed to be solid, rugged, reliable source of electrical power, specifically power that is, sufficient enough to withstand the extremes in “temperature, radiation, Pressure, and dust that would quickly disable or destroy most hardware and software systems on earth (National Aeronautics and Space Administration, 2012).” The social effects of reinstating production of Plutonium 238 will be examined as a part of determining the solution to the world’s limited supply of this material. This project will address the technological aspects associated with ASRG’s that are currently showing a much higher efficiency output as compared to MMRTG legacy systems. The environmental implications will be examined by studying mission that carried RTGs, failed and have the potential to cause extreme environmental damage, however due to design construction these catastrophes can be overcome by using rugged encasing designs. The political aspect will be examined based on current presidential space policies. Conclusions as to what will potentially be the likely future design of nuclear powered space systems will be recommended based off of detailed examinations of currently proposed designs from NASA and selected design corporations.
The student will be able to identify and apply appropriate statistical analysis, to include techniques in data collection, review, critique, interpretation and inference in the aviation and aerospace industry.To address all concerns proposed by this project and arrive at a conclusion will require significant data analysis. Statistical analysis as it pertains to the study of nuclear powered space systems and chemical powered space travel will be thoroughly evaluated. I hypothesize that the use of nuclear energy results in a higher propensity for electric propulsion verses chemical, solar, or solid fuel energy systems. If this is true and proved correct then nuclear energy based systems will be able to provide the energy required to propel and further advance the exploration of deep space. I also propose that using nuclear energy power systems will allow for a larger payload and longer sustained life given the lightweight construction of nuclear propulsion systems. This project will be using information gathered from research and development projects and peer review articles, to evaluate current trends in nuclear power epistemology and help to prove nuclear powered propulsion systems outperform conventional chemical or solar powered systems. This project will use data collected in initial design and testing phases of nuclear power systems to statistically compare and contrast systems in order to show the efficiency of these systems compared to solar and chemical alternative systems. Ultimately the interpretation of the data will prove or disprove that nuclear powered systems are superior to all other current power systems being used, especially as it relates to the difference between nuclear powered propulsion and chemical powered propulsion.
The student will be able across all subjects to use the fundamentals of human factors in all aspects of the aviation and aerospace industry, including unsafe acts, attitudes, errors, human behavior, and human limitations as they relate to the aviators adaption to the aviation environment to reach conclusions.
All subjects related to the fundamentals of human factors in all aspects of the aeronautical industry will be assessed. This includes the unsafe acts, attitudes, errors, human behavior, and human limitations as they relate to the aviator’s adaption to the aviation environment to reach conclusions. This outcome will be addressed by looking for the fundamental human factors involved in the implication of nuclear powered space systems. I will address the influence human factors have made on the development of nuclear power space systems. I will also address the way designs and safety protocols have developed throughout the years based on afore mentioned influences. Authentic archived documentation, as well as contemporary research and published journals pertaining to this topic will be assessed through peer review process to ascertain the true answer to the true motive of the issue. System design will be an integral part of the human factor process when dealing with nuclear powered spacecraft. The human factor in space exploration plays a major part in the expansions and developments of nuclear powered space systems. “To support the manned exploration and utilization of space envisioned in the Space Exploration Initiative (SEI), nuclear systems, for both propulsion and power applications, may be required (Sanders, 1991)”
The student will be able to develop and/or apply current aviation and industry related research methods, including problem identification, hypothesis formulation, and interpretation of findings to present as solutions in the investigation of an aviation/aerospace related topic.
Aviation and aerospace related projects as they relate to the implementation of nuclear power systems will be evaluated from their initial theory of how propulsion occurs by describing exactly how they produce force in order to propel spacecraft. Problems identified stem from a decreasing supply of Pu-238, in order to develop, to test, and to sustain nuclear power space systems. One of the main factors when dealing with nuclear systems is the concern the population will be exposed to radioactive material should there be a disaster. Politics and world opinion play a large role in the development and testing of nuclear space systems. Due to our populations critical view, the current political atmosphere, and world opinion development of space systems using nuclear technology has largely been put on hold. This allows for systems using chemical, Solar, and solid fuel propulsion systems to have a greater research and development advantage as opposed to nuclear powered systems. I hypothesize that if as many funds were focused on nuclear powered systems as were focused on solar and chemical systems we would be exponentially more advanced in our nuclear powered propulsion systems. To support this hypothesis I will research rapid developments made in the field of nuclear powered systems during the 1950’s compared to the current delayed development of the Advanced Stirling Radioisotope Generator. The ultimate solution to the continued development of nuclear space powered systems is to reinstate the production of Pu-238, and to also continue the research and development of future nuclear powered space systems. Findings and results will be documented as well as future plans for new projects and their methodologies. Related research methods will come from a content analysis method of analysis of peer-reviewed articles.
The student will investigate, compare, contrast, analyze and form conclusions to current aviation, aerospace, and industry related topics in space studies, including earth observation and remote sensing, mission and launch operations, habitation and life support systems, and applications in space commerce, defense, and exploration.
This project will examine earth observation and remote sensing by investigating current systems such as the Defense Support Program utilized to deter potential nuclear launched missiles, I will also investigate the follow on system called space based Infrared System (SBIRS) in order to compare, contrast, analyze and form conclusions as to where the constellation will be headed for use in the future. I will investigate mission and launch operations by studying historical missions that involved the use of RPS that initially caused much controversy during launch. With such high risks involved upgraded launch precautions had to be taken. I will be exploring the habitation and life support systems as they will relate to nuclear powered manned missions such as the SNAP X project used to power the Apollo Lunar Surface Experimentation Package (ASLEP). I will be relating to the applications in space commerce by researching the fuel production requirements needed to supply RPS’s used in space exploration missions. Defense policy regarding the use of nuclear systems in space will be thoroughly researched in order to explain how current systems are being used. Finally I will highlight the Implications of Nuclear Powered Space System and explain the current status of development and testing the nation is currently in with regards to exploration of the deep-space environment. I will investigate the systems that have been developed and highlight the advances made and mission that many of the RPS’s are currently operating on. My main focus will be on the exploration of space in areas that are inaccessible to normal power systems. I will be researching the advancements NASA is making in the development of a synchronized system using the ASRG capable of producing electricity on a more efficient level.
Multimodal transportation System
Social and Political
The projects and missions that have resulted from the dawn of the nuclear age have had a significant impact on both social and political aspects of society. From policy changes and regulations implemented to the way the world views space travel, the influence of space exploration as a culture can be seen as a core part of society. In a statement issued by the American Association for the Advancement of Science, they touch on this concept:
In terms of numbers of dollars or of men, NASA has not been our largest national undertaking, but in terms of complexity, rate of growth, and technological sophistication it has been unique….It may turn out that [the space program’s] most valuable spin-off of all will be human rather than technological: better knowledge of how to plan, coordinate, and monitor the multitudinous and varied activities of the organizations required to accomplish great social undertakings. Launius, 2008).
Acknowledging the social implications the space program has had on society is not fully comprehensible, especially since some of the best innovations and explorations that have expanded the imaginations and ingenuity of Americans and individuals worldwide have only touched the surface of what NASA has been planning. Every mission and operation from its inception has culminated into further knowledge about the field of space exploration. This can be seen from the most recent Mars landing all the way back to the Project Orion operations.
Project Orion was a secret project that was passed on by NASA due to its secrecy, but ultimately picked up for funding and managed by the U.S. Air force. It started with the destination of the world’s first atomic bomb in 1945 (Bruno, 2008). While the military devised a plan to use this bomb on Hiroshima, others began research to utilize atomic bombs to power propulsion to the stars, specifically Mars. As Wright notes, Von Braun was one of the first to endorse the possibilities of nuclear power in space travel, “Von Braun was more optimistic about the long-term future for nuclear propulsion. He addressed the subject in Tulsa, Oklahoma, on May 26, 1961, at the First National Conference on Peaceful Uses of Outer Space. “With a nuclear third stage. a Nova vehicle could be placed into orbit around Mars and returned to Earth later on Wright, 2003).” Theoretical physicist Freeman Dysan had calculated the number of atoms in the sun at the age of 5 and since established himself as a credible mind in the fields of space exploration science. He organized what would become known as Project Orion. Designing and certifying a space exploration system specifically for the purpose of use in manned missions is called “Manrating” a system (Sanders,1991). As Sanders notes, “A man-rated system is one for which all elements are designed with the highest possible reliability (Sanders,1991).” This means that the system is functional for a manned mission specifically within certain safety specifications. “Use of nuclear power systems in space requires approval which is preceded by extensive safety analysis and evaluation (Sholtis &Winchester, 1992).” Since 1961, more than twenty either civilian or military spacecraft using nuclear power as a source of energy have been launched by the U.S. (Sholtis & Winchester, 1992). All of the need for approval and red tape, is in response to political fears, but also due to actual safety risks the handling of nuclear materials can have on the public.
The same political opposition to use of nuclear energy that resulted in the formation of the AEC might argue that space exploration has been accomplished without the use of nuclear energy, but the authors note, for certain missions to the moon and destinations beyond that offer sufficient sunlight and natural heat, solar power is an excellent choice. However, several proposed NASA missions given top priority by the scientific community would visit some of the harshest, darkest and coldest locations in the solar system; many of these missions would not be possible or would be extremely limited without the use of RPS’s (National Aeronautics and Space Administration, 2012)). The Radioisotope Power Systems Committee (RPS) is devoted to making sure the U.S. does nto fall behind in the race for nuclear power innovations and progressive use. All experiments and studies involving radioisotope power systems have culminated to prove one conclusion, that the U.S. will need to establish a way to produce it’s on plutonium. The RPS committee notes that, “it has long been recognized that the United States would need to restart domestic production of Pu-238 in order to continue producing RPSs and maintain U.S. Leadership in the exploration of the Solar System (National Reseaarch Council, 2009).” One major issue that has stemmed from the limited amount of Pu-238 available in the market can be seen in the fact that, NASA is deliberately prolonging the duration of RPS-powered missions by removing RPSs as an option for some missions and putting other missions on hold that require RPSs until more Pu-238 becomes available (National Research Council, 2009).
This slows down technological advancements in U.S. Space exploration and leads the country to be vulnerable to falling behind other countries with potential political or ideological alternatives, specifically Russia. Reseachers note that it will take the DOE about 8 years to fund and reestablish production of Pu-238 to get to the point of producing 5Kg/year (National Research Council, 2009).” All statistics show that there is a clear race for Pu and that it’s not just in high demand but scarsly produced, and not all produced within the U.S. Pu-238 production is the key to the future of space travel, and currently the U.S. can only buy theirs from Russia. Calling this a political irony is an understatement, but it ultimately will fall on the U.S. government to see the light and secure funding for Pu-238 production. The odd fact is the path to funding Pu-238 production might not be through emphasizing space program needs; it may come in the political benefit of supplying the growing needs of the U.S. Navy.
House Representative Roscoe G. Bartlett, member of the subcommittee on Projection Forces for the United States Accountability Office, wrote a letter to the chairman in 2006 requesting funding for propulsion systems for navy ships. In the letter he argued that the Navy had implemented the use of nuclear propulsion as an energy source in prior years, and they found that it provided a cost effective alternative to the use of fossil fuels. In response to the increased prices in fossil fuels, despite more efficient technology, the report was a follow-up on the Chairman’s request to find alternative methods of generating power for the Navy. The table below shows the current breakdown structure of the cost of traditional methods utilized for propulsion by the Navy. This table clearly shows that more money is being spent on alternative power technologies that could be more effectively invested in nuclear power propulsion methods.
Bartlett is keen to point out that while these methods have their cost, advancements in nuclear propulsion have made it a much more affordable option. He states, “According to Navy officials, nuclear power plants are now simpler in design and smaller; have reduced maintenance requirements; and require half the manpower of older plants, as demonstrated by the design of the CVN 21 class aircraft carrier. Officials also stated that the life of nuclear reactor cores has been extended (Bartlett, 2006).” Bartlett distinguishes the difference between nuclear reactor core lifespan verses traditional fossil fuel use. Here is an image of a nuclear reactor core shown below:
(Myrabo & Powell, 1983)
In his letter to congress, Bartlett identified the benefit the Navy would have in utilizing nuclear reactor cores to fuel ships. He says that the Navy would be able to go without refueling their submarines which have a life span of 33 years, compared to those powered through fossil fuels which need to be refueled every 18-20 years.
This report supports the claim that nuclear systems are more cost effective and ideal for transportation systems, regardless of whether the method is by space or by sea. All of the research and development hours invested by the Navy, as well as other resources, on gathering data on the enhanced use of fossil fuels Navy talk a lot about using fossil fuels for propulsion. The article talks about the R&D time and money spent on development of fossil fuel engines. The methodology used here is to assess alternative methods, of propulsion. Bartlett points out that the Navy is not fully utilizing current data on nuclear power some point there is discussion of new technologies.
These new technologies could be powered by of nuclear propulsion systems. If as much money was spent on nuclear propulsion systems as on fossil fuels, data suggests the Navy would be much further ahead in capability and cost efficiency than they are today. It’s true that this report focuses on Navy marine travel space systems but it talks about the research and development of propulsion systems. This dialogue ultimately leads to innovations in the market of study across all transportation methods and utilization forms. This is the standard method through which deeper understanding of nuclear power use is attained. The data retrieved through studies carried out during Project Orion can largely be attributed to the current understanding for project cost safety as well as the potential threat nuclear power use has on human lives, specifically in regards to the use of Pu-238, compared to traditional chemical methods.
Environmental Aspects of Nuclear Powered Space Travel
The environmental risks involved with employing nuclear power in space are very similar to those on Earth. The difference is the level of threats imposed by environmental changes, such as differing radiation levels between planets, asteroids, or nearby space debris. Radiation safety is attained through moving spacecraft into long term stable orbits (Campbell, King , Wise & Handley, 2009). There is also a backup emergency method of reducing nuclear radiation in space travel, which entails the dispersion of fuel into the atmosphere that are sufficiently small enough to pose no real threat to human life or the environment. This environmental safety precaution was put into practice after the failure of the Soviet Cosmos-954 spacecraft in 1978 resulted in a massive quantities of radioactive wreckage (Campbell, King, Wise & Handley, 2009).
Campbell and authors note that while there have been environmental concerns regarding any use of nuclear power, a wide range of innovative methods to enhance environmental safeguards through the use of nuclear power have been developed. Some of these innovations include a ‘space elevator’ to deliver materials from space, to the surface of the Earth, or equipment’s and personnel from Earth into space. Another innovation is the creation of a ‘space gravity tractor’ this is a device that would utilize nuclear energy to push asteroids and other objects out of orbits set to collide with Earth. Campbell and authors notes that, “nuclear systems will enable humankind to expand beyond the boundaries of Earth, provide new frontiers for exploration, protect the Earth, and renew critical natural resources (Campbell, King, Wise & Handley, 2009).” The authors are clearly major proponents of the use of nuclear power as environmental safeguards. What this demonstrates more than anything is the diverse uses nuclear power has beyond basic propulsion. It is another factor supporting the use of nuclear energy over controlled traditional chemical reactions.
Plutonium has been found to be a valuable resource to satisfy this dual need for sustainable power in space travel in congruence with environmental safety. As noted National Aeronautics and Space Administration (NASA), “The natural nuclear decay process of plutonium-238 causes it to emit alpha particles, a type of ionizing radiation. These alpha particles, emitted in the form of helium nuclei, travel only about three inches in the air, and can be blocked by clothing, skin or even a sheet of paper (National Aeronautics and Space Administration, 2012). This means that plutonium-238, unlike other levels of Pu is environmentally safe.
Advancements in space studies have been evolving rapidly, but now in regards to the use of nuclear energy to power spacecraft, it appears the U.S. has hit a brick wall. While NASA still continues to experiment with the use of chemical energy, RPSs are the only energy sources capable of producing unlimited power for extended periods of time for deep-space missions. The use of Pu-238 will usher space exploration into a new age of being able to travel further and deeper into space than once was ever concieved. Currently NASA has in the works plans for pioneering space missions, none of which would be possible without the support of RPS’s. One political benfit of Pu-238 is that it is not capable of being used in nuclear powered weapons. A major complication intervening with the expansion of U.S. nuclear space travel and the implementation of pu-238 as a viable power source is that, there has beenno Pu-238 productionin the U.S. since the (DOE) shutdown production facilities in the late 1980’s.
A fundamental requirement for space travel is a reliable source of electrical power, specifically power that is sufficient to withstand extremes in “temperature, radiation, pressure and dust that would quickly disable or destroy most hardware and software on earth.. Spacecraft are usually subjected to these extreme conditions continuously for extended periods of time, in some cases for years at a time. Technology development in the field of space craft, specifically in regards to the involvement of nuclear energy was taken head on by NASA and the Department of Defense in 1989. As Bennett, Graham and Harer note, NASA has held discussions with DOE and the Department of Defense (DoD) on establishing a broadly based program of technology development in nuclear propulsion (Bennett, Graham & Harer 1991).” The authors point out that this joint initiative was launched following a speech given by President Bush in 1989 commemorating the 1989 Apollo 11 lunar landing and the resulting public framework for future exploration implemented by the President, inclusive with a $7 million budget entirely devoted to nuclear propulsion technology development. From this joint partnerships many technological innovations developed in the field, specifically the use of radioisotope power systems.
(National Aeronautics Space Administration,2012)
A partnership between NASA and the Department of Energy (DOE) established radioisotope power systems to use heat as an energy source. The heat is generated from the decay of the radioisotope plutonium-238, which occurs naturally. This energy source is so powerful it can produce enough energy to power a spacecraft. Radioisotopes are also used as heating sources for spacecraft internal temperature control to make the spacecraft inhabitable in deeps pace manned missions under the coldest conditions. This technology accelerated the progress of nuclear electronic (NEP) and nuclear thermal (NTP) propulsion technology development.
The above image is an example of one of the first schematics of a nuclear electric vehicle drawn up for a July 1990 NASA sponsored workshop, following President Bush’s 1989 speech on expansions in nuclear energy use. In the image of a nuclear electric vehicle, the
Reactor is represented by an (R) and the shield by an (S) on the left. The payload and thrusters are represented on the right. The radiators, power conversion, and power conditioning equipment are all located in the middle of the vessel. The main concept here is that the power generation subsystems and the propulsion thruster subsystems would produce the electrical power used “to accelerate ions or other subatomic particles, resulting in continuous low thrust (Clark, 1991).” Development of concepts like these with the goal to utilize nuclear energy in space travel saw the most political and social support during this time period right after the President’s speech, and also as a result of influx spending on NEP and NTP projects.
Multimodal Transportation System
The Multi Mission Radioisotopes Thermoelectric Generator (MMRTG), similar to the one used by the Curiosity Mars rover allows for long rover life regardless of surface conditions. The concept uses the heat to produce electricity using thermocouples. In addtion the heat is piped throughout the rover in order to keep scientific instruments operating in a controled temperature environment. Prior to the Mars rover construction, RTGs had been used in more than 26 flown U.S. space explorations, specifcially the Pioneer, Voyager, Gailileo, Cassini, Viking, Ulysses, six of the Applollo missions and the New Horizon missions (“Science Mission Directorate,” 2006).
A new design Of RPS’s are currently under development, this system is called the Advanced Stirling Radioisotope Generator, the radioisotope heat is used to drive a piston that moves back and forth. Currently the Multi-Mission radioisotope Thermoelectric Generator (MMRTG) is the only RPS available (National Research Council, 2009). These systems use thermocouples to convert the heat to electricity, they have no moving parts and have very high reliability and long life, however the efficiency is low.
Statistical analysis concerning the difference between nuclear powered propulsion and propulsion formed through chemical methods points to the assessment that nuclear power is a cheaper and more efficient energy source. The concept of using nuclear energy for propulsion can be traced back to Robert Goddaard in 1906, he entertained the concept of using radium as a source of energy but realized very quickly that the level of power it produced was insufficient (Bruno,2008). The analysis of propulsion stems from the understanding of the particles that produce force. This understanding is based on numerous equations astrophysicist use to calculate what they call force potential.
What is often recognized as the third force potential, or nuclear potential, relates to the “strong” nuclear force among nucleons. This force that binds them together, and prevents the nucleus from disintegrating spontaneously as a result of overstimulation or external variables. The energy that binds the nucleons together is negative compared to the energy stemming from the nuclear force itself, which is why Bruno states, “The larger the binding energy, the deeper the potential will be (Bruno,2008).” When a nuclear reaction occurs, “the original nucleus (i) plus other particles, such as neutrons, are the “reactants.” The total mass of the “products” formed (lighter or heavier nuclei, plus energetic particles) can decrease or increase. If mass decreases, as stated by Eq. (1a), energy is released (Bruno,2008).” This process makes nuclear energy a much more effective method of powering systems, especially due to its execution of nuclear isomers as an alternative energy production method.
In addition to fusion and fission, there is a third type of nuclear energy identified as nuclear isomers. It is available within nuclei of specific isotopes. These isomers have many similarities with standard nuclei, such as mass number, so the same number of protons, electrons and nuetrons, but the nucleons inside the nucleus are arranged differently space wise, so it effects their potential energy (Bruno, 2008). Bruno then takes his analytical details to the topic of propulsion.
The core necessity for propulsion is the use of momentum, but Bruno recognize mass as an alternative impetus for propulsion. He notes that, “Chemical rockets eject matter accelerated by chemical heat release, and collimated by the solid walls of a nozzle, but propulsion by change of momentum of massless particles is also conceivable (Bruno, 2008).” Bruno notes that there is a three stage process that involves the transition of potential energy to exhaust jet energy, or thrust energy (Bruno, 2008). Stage one involves converting potential energy into kinetic energy particles (Bruno, 2008). Stage two involves non-equilibrium microscopic kinetic energy that redistributes the particles. Stage three entails, “equilibrated medium, with high energy density, is exploited in some way to produce thrust. This stage can take different forms, according to the specific propulsion concept chosen (Bruno, 2008). “The key factor here worth mentioning is that most of the energy is trapped potential energy, most of the energy is conserved whole going through each stage (some can be lost by radiation) (Bruno, 2008).” The below equationdemonstrates the binding collaboration between fission and fusion and how it produces energy.
With nuclear energy there are some risks, but the benefits are heavily weighted in favor of implementation in space travel. The statistical analysis of the pure value of nuclear energy as a power source is best understood by this above equation. According to Bruno, this equation “confirms why nuclear power is critical for future space missions.” He points out that the square-root dependence shows that increases of J are what dictate the magnitude of energy produced. In an example where chemical High Energy Density Matter (HEDM) is used instead of plutonium-238, he says, “using chemical HEDM” has a minor effect on Isp. Only by increasing J by orders of magnitude can Isp increase significantly. This means that with nuclear energy, the magnitude of power can increase exponentially, seamlessly without limitation. This is the case of nuclear energy, Bruno explains some basic facts about nuclei and how they are utilized to produce energy. He notes that, “Metastable nuclei can be produced by nuclear processes because most of the time they are formed in an excited state and then decay emitting beta particles (that is, electrons), gammas, or X-rays (Bruno, 2008).
The results and findings of these projects have resulted in a more fundamental understanding of the solar system and the place of human beings in the universe. The concept of harnessing nuclear energy to power space travel garners controversy, because while it’s arguably essential for the advancement of space exploration into its next era, there are many advantages to this 60 year old technology, but also disadvantageous aspects of the science that lead some to doubt its true worth. The human studies implemented during Project Orion resulted in distinct understanding of the difference between chemical power systems and nuclear energy finding nuclear to be significantly more powerful.
Data shows that, “The ultimate form of nuclear energy release occurs when matter and antimatter, for instance, a proton and an antiproton, are “fused.” This is actually called annihilation, both masses disappear, becoming energy according to Einstein’s law, and ‹ = 1 (Bruno, 2008).” This core concept demonstrates how energy is formed through the process of annihilation, but Bruno goes onto point out that there are limitations to this process, as, “No nuclear process can produce ‹ between ‹4 ∙10┐3 and the theoretical 1.00 of annihilation: nuclear reactions transform mass into energy with ‹ “limited” to few tenths of a percent. The reason is also the limited average binding energy (Bruno, 2008)” Binding energy limitations are clearly a significant factor to consider in regards to nuclear space power. The problem with annihilations is that it’s not clearly usable as a continuous source of energy. The energy produced from annihilations cannot be recycled, re-used, or put into any form of a cycle. Bruno points out hat because no nucleon is annihiliated in the process of a fission/fusion reaction, annihilation is most commonly studied solely within particle accelerators. So, even when more energy is being used with nuclear energy as opposed to chemical energy, more energy is also being conserved. He goes onto point out that despite the fact the process if investigated and researched for its use as an energy source, currently it is only viewed as a conceptual source of propulsion (Bruno, 2008). When this process occurs and nucleons are bound, they are bound to other nucleons, each with a slightly different energy depending on A, just as electrons to the nucleus of an atom (Bruno, 2008). The annihilation concept can be traced back to much of the data and research observed during Project Orion.
Advantages of Electric Propulsion
It is common understanding among nuclear physicists and nuclear energy epistemologists alike, that “the achievement of higher SI results in a reduction of the propellant mass required to accomplish a given mission.. This is in comparison to chemical system alternatives. This knowledge is the driving ideology behind the permute to find new propulsion system in aerodynamics. The authors go onto to note that, “It is well established that electric thrusters can provide values of SI an order of magnitude greater than those of chemical engines, so that they are clearly candidates for deep-space missions requiring large velocity increments.. This means that nuclear energy utilized through the decomposistions of plutonium can result in a higher propensity for electric propulsion ultimately leading to spacecraft that can explore further into deep space. The authors link this concept with prior theories of Newton that included in the mission plan to achieve greater economy, EP becomes critical to success. These conclusions follow directly from Newton’s Laws of Motion because it can be shown, by equating the instantaneous rate of change of momentum to the force applied to a spacecraft by its propulsion system. Here we see the law applied:
Contemporary knowledge in this field of study note that the ∆M=Mo – Mf represents the mass of propellant consumed. It is through the increase of mass propellant consumed that the actual exhaust energy is produced in the launch process. When this is done through a chemical launch the force is significantly lower than that of a radioisotope power system.
In his study on “Advanced Nuclear Space Propulsion Systems,” Liviu Popa-Simil notes that the limitations of chemicals propulsion actually make it very complicated to work with and that, chemical propulsion is also dangerous because stacking together two highly reactant materials like liquid hydrogen (LH) and liquid Oxygen (LO) requires a very high level of technologic performance, while some other fuels exhibit a high level of toxicity, increasing the technological challenge even more (Popa-Simil, 2011)” He goes on to talk about the benefits of nuclear propulsion as an alternative to chemical reactions. He uses the diagram below to propose how a ship can travel to Alpha Centuri by manipulating mass, a method that ultimately propel a ship further into space.
He says, “without going further in the analysis of the errors committed in such an approach, or how well it matches the reality, one may look for the qualitative results (Popa-Simil, 2011).” He goes on to point out that, “power determines the acceleration, but not the speed increase, when the total available energy is finite. To transform energy into thrust, by using the reaction principles we need to accelerate mass (Popa-Simil, 2001).” The summary of Popa-Simil’s argument in the most basic terms is that nuclear power provides greater acceleration than chemical reactions and when one is landing on a planet and then taking off from that same planet they are starting from a neutral point of propulsion. The level of acceleration put into their thrust will ultimately increase their speed through manipulating their mass as they leave from LEO to GEO. Nuclear power by Popa-SImil’s analysis has greater capability of breaking from orbitals. This puts nuclear power in the position of being a more efficient power source when it comes to longevity and adaptability in space travel.
Think of Advanced Stirling Radioisotope generators as a super charged battery that can last over a decade. ASRGs have much higher efficiency, (~27%), which greatly reduces the amount of PU-238 needed to support future missions. An ASRG has the capacity to power a mass of 32Kg and launch the projectile into deep space and sustain it within the environment for up to 14 operating years. Despite the fact that this is a proven method of PU-238 reduction and human exposure, it is still estimated that over 150 million dollars will be required in order for the U.S. to return to the internal production of peaceful plutonium. In the stirling engine converter used by ASRG’s, helium gas oscillates in a regenerator, one end of which is heated by radioactive decay of PU-238, while the other end is cooled by a heat sink (National Research Council, 2009).The ASRG will eventually have an opportunity have an exhibition of its performance levels. Anticipation for this project is building astro physicists. Researcehrs note that, “The discovery 12 mission is the earliest potential opportunity to fly an ASRG, and the mission is not scheduled for launch until 2014. NASA plans to make the final decision on whether to use MMRTGs or ASRGs for OPF 1 no later than 2012 (National Research Council, 2009).”
(National Research Council, 2009).
Here we see the ASRG and MMRTG levels in association with their Pu usage, but also funding is mentioned. It is clear that Pu is high in demand compared to the supply.
(National Research Council, 2009).
The ASRG is projected to have an exact power of 7 We/Kg, relative to only 2.8 We/Kg for the MMRTG and 5.1 We/Kg for the best previous RPS. This improvement in specific power is a significant consideration for deep-space missions for which mass and launch-vehicle capability are typically significant system drivers (Radioisotope Power System Committee, 2009). The above chart shows that Pu production plays a role its usage. NASA’s plan for Pu production in the U.S. in the near future requires a certain balance between diplomacy with Russian and proper funding.
The most logical interpretation, based on the sum of all the data available on this topic points to the clear fact that chemical rockets have limitation in regards to generated thrust per unit mass of fuel, that nuclear powered rockets just don’t encounter. In the simplest terms, in addition to being more powerful than the chemical alternative, nuclear power energy systems are also more affordable as they are capable of varying twice the workload, with half of the needed mass to perform the task. Data shows that the bulk of funding or space exploration focuses on chemical use or how to reduce nuclear powered energy system.
Fundamentals of Human Factors
The human factor in space exploration plays a major part in expansions and development in 1989 on the 20th anniversary of Apollo 11’s moon landing President Goerge H. W. Bush announced plans for he Space Exploration Innitiative (SEI). In the speech he mentioned the development of Space Station Freedom, A NASA project for building a space station that would orbit the Earth’s atmosphere. Space station Freedom was originally approved by Ronald Reagan and announced by Ronald Reagan in his State of the Union Address, but the project evolved into what became known as the International Space Station Program (ISS). The ISS was initially launched in 1998 and known as the only satellite stations orbiting the Earth visible by the naked eye. The station currently has three astronauts onboard but can be manned by up to six people. Many scientist note that in order to power a manned space exploration to the capacity of that planned for by the Space Exploration Initiative (SEI), “Nuclear Systems, for both propulsion and power applications may be required (Sanders, 1991).” SEI has led NASA and other astrophysicist worldwide to speculate on many concepts involving nuclear power apsce stations in outer-space that could be used as living quarters by humans.
This was a major concept because it meant the missions involved in the use of nuclear power would be isolated to space, but also that man would be closer to migrating away from Earth.. A space station of this magnitude in Outer-space in many ways is already in the works and can be seen wit the concepts like project, Systems for Nuclear Auxillary Power X (SNAP-X). SNAP-X is a new and basic idea that involves a system where a breeder reactor is placed on Earth and the Moon. This will serve as a sort of gas station, as well as a drop off point for “nuclear fuels.” As this is an innovative concept there are numerous safety aspects that must be accounted for. Many of which cannot be foreseen. Dodd and Thangevela note that only one single launch from earth is necessary to get the reactor started, but safety of the program can’t be ensured beyond that first mission (Dodd & Thangavelu, 2012). They say “We can reasonably ensure the safety of the single, first and only fissle fuel delivery. For the Cassini mission to Saturn (Which utilized an RTG), NASA estimated an overall mission probability of 0.28% for an accident that would result in radioactive contamination (Dodd & Thangavelu, 2012).” This suggest that the project has potential safety rishs that cannot be estimated accurately. It is also certain that one single launch will bot be adequate enough to sustain the operation of the reactor. Dodd and Thangavelu point out that, “As the reactor operates, it will need occasional resupplies of fertile materials. Fertile materials are far more benign that fissile fuels (Dodd & Thangavelu, 2012).” The authors are clear to point out that these would be routine resupply missions, because the fertile materials require minimal special handling, and because the resupply missions would have a short duration, the requirements for the delivery system are not strenuous by spacecraft standards (Dodd & Thangavelu, 2012).
The concept itself is very basic, but what it will mean for expanding the reach beyond current human limitations in space travel is priceless. Man has already traveled to the moon numerous times now and while the implementation of nuclear power in this type of conditions could be asking for trouble, Pu-238 is documented as not capable of being converted into nuclear weapon form. It’s also the only stable form of radioisotope electricity producer that can actually powered a spacecraft. This shows how the use of nuclear power in space even in respect to manned space stations will mean a new frontier for the human race.
The real influence that can be seen humans have on the design and functionality of spacecraft as well as the extent to which it utilizes nuclear energy, all stem from limitations which outer space travel pose to the human body (Myrabo., & Powell, 1983). Key developments that have resulted from this understanding have also lead to more indepth research in regards to the benefit of nuclear power propulsion systems verses chemicals methods; and while cost effectiveness and efficiency have always been a core part of this conversation, first the dialogue had to begin with the essentials for safety and human design.
As Alexis Madrigal notes in his Atlantic article “The limits of the Human Body in Space: An Illustrated Guide,” the possibility of space travel brought up the discussion of human resilience in space. He says, “as soon as we saw outer space as a frontier to be visited, all of the things our bodies took for granted had to be considered problems.” Madrigal points out that there is no one thing that has reminded human beings of their vulnerability to the elements more than the concept of traveling into outer space. He notes that all the things humans take for granted on Earth such as the perfect level of oxygen, gravity and water for a living environment work against us. He says, NASA Scientists approached the human body like engineers. They look at the body like it was a machine, which meant its materials and processes could be examined through a Q&A process. Testing human exposure to heat and radiation, understanding what level of vibration causes debilitating testicular pain, or the level of acceleration that makes the human brain go unconscious, these were all concepts that had to be thoroughly assessed. How long could they operate under stress? What would weightlessness do to the human body over prolonged periods of time? Estimates were drawn an evaluated based on the probability of survival under certain conditions, and aspects of the human bodies functionality and limitations were assessed in ways that had never before been done. Space explorations and the science of the process extended far beyond contemporary scientific knowledge. Everything seems very official and thought-out, but in a couple of years after Yuri Gargarin’s milestone flight into outer space, very little was actually known about how humans would respond to the extraterrestrial environment or what kinds of spacecraft they might need to stay alive..
In 1959, there was no documented account of a human being travelling beyond the limitations of gravity, so there was plenty of speculation as to how space travel would influence the human body. Some believed organs might cease to function inexplicably, or that muscular control and motor skills would falter or fail all together. There was speculation that food might resist the act of being swallowed and eyeballs would lose their shape, change in consistency, or even simply drift out of their sockets. In response to all of these questions, thorough studies had to be run to prepare man for space travel. As the authors note, “the doctors at Lovelace had no idea, and so they did every test they could think of. They tried to shake the men’s bones with blasts of sound, sat them under pulsing strobe lights, induced vertigo, plunged them from light to dark and counted how long it took to focus their eyes again. Space travel challenges mankind not only technologically but spiritially, in that it invites man to take an active part in his own biological evolution, “Manfred Clynes and Coauther Nathan S. Kline wrote in their Cyborg paper on Astronautics. “Scientific advances of the future may thus be utilized to permit man’s existence in environments which differ radically from those provided by nature as we know it (Bruno, 2008).” This is the core goal of pushing space science and technology to its limits. Man can evolve to live on another planet, or simply live in outer space. This initially is a concept that seems to come right out of science fiction novels, but it is actually very present.
Unsafe Acts, Attitudes, Errors
Due to human limitations, there must be exceptional precautions taken to secure the safety of human passengers, “Stringent design and operational flight safety measures aer required to protect the public and the environment under normal and accident conditions (Sholtis & Winchester, 1992). This is obviously due to a wide range of potential unsafe acts, dangerous attitudes, or errors that could be fatal but also could be attributed to natural human behavior. An example could be as simple as not completely sealing the space craft for air ventilation purposes, or mismanaging valued resources, to not following proper protocol for maintenance issues. As the authors note, “All launch sign-offs are made based on risk benefit assessment carried out by the office of the President (Sholtis & Winchester, 1992).” Below is a summary of the safety policies designed by the Nuclear Safety Policy Working Group (NSPWG):
Based on all of these safety considerations, a group of independent experts who all stem from academia, Industry National Laboratories and Government compose five Interagency Nuclear Safety Review Panel INSRP subpanels. These subpanels provide technical and analytical support to the INSRP (Sholtis & Winchester, 1992). All of these safety precautions have been established based on accidents that have occurred through NASA testing, or operations. The accidents were then evaluated and analyzed to assess the precautions that could have been taken to avert the incident.
NASA in collaboration with the Russian Aviation and Space Agency MINATOM, the ESA, and others applied their collective knowledge of the current state of space exploration technology and they have identified a set of long-term problems in regards to space exploration (Campbell, King, Wise & Handley, 2009). They identify the solution to these problems as higher power levels. The problems are identified as the following:
- The task of developing next generation international communication systems for remote sensing, television broadcasting, forecasting of earth’s geological activity, navigation, and exploring for resources.
- The ability to produce special needed materials in space.
- The construction of a manned space station on the moon, as well as the creation of a lunar NPS, industry-scale mining of lunar resources;
- The ability to execute routine manned missions to the Moon and Mars and eventually other planets and their satellites.
- The ability, if need be, to transport the Earth thermonuclear fuel — thorium, 3He isotope, etc.
- The removal of radioactive waste to store in space.
- Clearing of space satellite fragments from space to avoid the ensuing orbital hazards.
- The need to protect the Earth from potentially dangerous asteroids.
- The need to restore the Earth’s ozone layer through the adjustment of CO2 levels and other methods.
As previously mentioned, I hypothesize that if as many funds were focused on nuclear powered systems as were focused on solar and chemical systems the U.S. would be exponentially more advanced in our nuclear powered propulsion systems.
The solution to the bulk of limitations mentioned in the problems section all point to a required need for nuclear powered systems in space exploration. In the research article on Nuclear Electric Propulsion conducted by the NASA Research Center, the researchers identify nuclear electric propulsion as a better, safer and cheaper method for human exploration of Mars. In Ruchit Nagar’s presentation TED talk, he makes the connector between nuclear weapons and space travel. He points out that nuclear weapons pose a threat through terrorism, accidents or miscalculations (Nagar¸ 2011). He identifies the real issue as a need to focus on how nuclear weapons can shape public policy. His conclusions is that nuclear spacecraft propulsion is actually a solution for the problem of human extinction. He says NASA lacks the funding necessary to implement reactors necessary to convert nuclear weapons into fuel. He says this method can led to having a working exit strategy from Earth into space for the furtherance of human life.
The type of propulsion necessary to create an artificial environment in order sustain life in outer space for a prolonged seemingly infinite period of time. “Up to this point, the nuclear safety and design philosophy has primarily been devoted to unmanned system operations, except during the ROVEW NERVA engine program (Sanders, 1991).” These specific guidelines need to entail manned design based concerns for virtually all nuclear propulsion and power systems (Sanders,1991).
Prior data, suggests it would take nearly two or three years just to negotiate and finalize an agreement with Russia before work could begin. This prolonged period would also entail not using nuclear energy in space travel.. In addition, the U.S. has their hands tied as Pu-238 obtained from Russia can be used for civil applications and cannot be used to satisfy U.S. national security applications, should they arise (National Research Council, 2009).” Russia agreed to sell Pu-238 to the U.S., but only under a limitation that it’s used for peaceful purposes. And this same stipulation presumably applies to future purchases (National Reseaarch Council, 2009).
Related research methods
The level of human planning and research methodology that aeronautical engineers put into studying space travel and the solar system in programs like Project orion, and Ulysses, leads to further development of concepts and ideas, on which contemporary understanding of space travel research and methodology can build all space travel research pertains to expansion of the epistemology come from projects and experimentation. For example, the method through which new knowledge and technological advancements are attained within the field of space science, especially as it relates to the evolution of space travel and nuclear energy use happens through a system of project launches. It’s easy for a physicist to theorize, but without physical application in the form of numerous experiments, those theories never gain merit, and with space exploration experimentation requires massive funding. For Example, without the U.S. Air Force picking up and funding certain secret projects like project Orion, which pioneered the use of nuclear energy in space exploration, the U.S. would be far behind Russia in regards to space travel. Also these early experiments involved the use of Pu-238 in order to provide an in-depth understanding of its use and .
There have been several ideas that have been considered in regards to enhancing nuclear thermal engine capabilities and methodological developments within this project. As Kozdron and Tieman note, “one key idea is to run the engine at low power after the burn,” which would permit the space craft to generate electric power and sustain it as a source over the duration of a trip. The second concept that is currently being entertained in regards to thermal nuclear engines is to o insert high temperature plumbing into the core after the initial act of propulsion. The energy gathered by this plumbing could is estimated to produce enough electricity to run an electrical engine. This will allow for drastically reduced transient times because of the additional thrust (F=ma)  (Kozdron & Tieman, 1999).” This basically means the spacecraft have a power source for longer lasting durations, due to recycled energy from initial the initial propulsion. It demonstrates the conservatory nature of nuclear energy in transportations as a whole, but also it serves as an additional cost that can be limited through the minimal use of energy.
In AstroDigital’s online journal on space exploration when speaking on Space Mission Analysis Blair P. Bromley points out that four of the key concerns in space travel as being the projected destination, trip time, the question of whether the trip is one way or two way, and the projected mass load to be sent on the spacecraft or brought back. He notes that the main limitation between the two deals with the actual capability to move mass, “…there is a limited energy release in chemical reactions and because a thermodynamic nozzle is being used to accelerate the combustion gases that do not have the minimum possible molecular weight, there is a limit on the exhaust velocity that can be achieved (Bromley, 2001).” The value of molecular weight is an essential part of how efficiently an object can achieve propulsion. Here Bromely is pointing out that the limitations in force or energy caused by chemical reactions is even more suppressed by the fact that a ‘thermodynamic nozzle’ must be used to achieve chemically induced propulsion. The weight affects the velocity and requires an additional energy . The actual propellant equation used to measure propulsion is displayed in the image below:
Mpropellant = Minitial – Mfinal
The above equation can be used to make a clear cut distinction between nuclear and chemical powered propulsion in space travel.
Earth Observation and Remote Sensing
Remote sensing in the most basic terms is defined as the art or science of telling something about an object without touching it. In John G. Cloud and Keith C. Clarke’s article on the relationship between civilian and military intelligence and remote sensing early on during the start of the U.S. Space Program. Earth observation specifically entails the act of taking photographs from outer space, but has the data shows, The Defense Department is already in the works to make infrared laser tracking technology and remote sensing is just another aspect for appreciation.
The Mars Science Laboratory Mission utilized something known as a ChemCam, which is a laser-induced remote sensing camera used for chemistry and micro-imaging (“Science Mission Directorate,”2006). This remote sensing tool came in handy during the Mars probe Mission, specifically in regards to chemical sample and ecological data retrieval, as well as imaging of the rover landing site upon the initial landing. See the image below for more detail:
As noted in the proposed Mars Science Laboratory rover illustrations, the rover was designed to support a remote sensing mast, also known as a Chemcam, that “provide an elevated platform for critical engineering and scientific assets such as navigation imaging cameras, science imagine cameras, remote sensing instruments, and a meteorology instrument (“Science Mission Directorate,” 2006).” The mars rover is an example of how advancements in remote sensing are exponentially enhancing man’s reach into space.
Mission and Launch Operations
The Apollo Lunar Surface Experiment Package (ALSEP), was a set of instruments used by astronauts during all of the Apollo missions after Apollo 11. Apollo 12, 14, 15, 16, and 17. The packages were left behind on the moon to assist in experiments ran autonomously to measure long term studies of the environment of the moon. The process these operations was to setup the packages within a reasonable distance from a power station which powered all of the packages through the use of a radioisotope thermoelectric generator (RTG). In regards to the durability of RTGs, thermal controls, and other functioning aspects of the ALSEPs, Bennett, Hemler and Shock note that, “All of the RTGs exceeded their mission requirements in both power and lifetime. This performance was achieved by the RTGs despite the variable duty cycle and the temperature extremes of the lunar day-night cycle. All five RTG-powered ALSEPs were operating when NASA shut down the stations on Sept. 30, 1977 for budgetary reasons (Bennett, Hemler, & Shock, 1996) It is through missions like these that scientists are able to better retrieve data on the environmental climate of space, the moon and its molecular structure. Most of the vital knowledge that has evolved out of mission and launch operations makes of the basis on which space exploration technology and knowledge exists today. As influential as the Apollo missions were much of the knowledge utilized to effectively complete those missions were attains during Project Orion operations.
During the Project Orion studies, it was found that the substance was only dangerous if ingested or inhaled in large quantities once broken down. The authors note, “ingestion is only plausible through the food chain, where foods contaminated with Pu-238 are consumed. This requires that the Pu-238 be released and vaporized or pulverized into small particles (less that ~100 microns in diameter) and then transported through the atmosphere so that can deposit on or within food stuffs (National Research Council,2009).” It is through these experiments and operations that Pu-238 has been clearly identified through scientific testing as, “the only isoptope suitable as an RPS fule for long-duration missions because of its minimal half-life, emissions, power density, specific power, fuel form, availability, and cost (National Research Council, 2009).” The methodology process works as follows, administrators for NASA writes a letter requesting that the Department of Energy Provide and sustain the capability for NASA to have fueled RPS assemblies. The letter is approved, and when missions are structured and launched, the knowledge attained during preparation for the missions and an analysis of their mistakes, results in further data for study. The current plan for NASA over the next 20 years is to have 12 missions during the 20-year period from 2009-2028. All of these missions have electrical power requirements from 100-2,000 watts (National Research Council, 2009).” The culmination of all launch operations and missions data to date has resulted in a common understanding among astrophysicists and nuclear power aficionados alike that nuclear power is the only viable energy source for space exploration beyond the sun. This is why the ASRG or some other type of Stirling Radioisotope regenerator is the baseline for all other missions listed in the administrator’s letter, and will be used as a main power source on the mission as well.
As Bennet notes “Nuclear power is the only available alternative to solar power for spacecraft which must operate for a long period of time. Moreover, nuclear power is the only practical option for spacecraft which must operate far from the Sun (Bennett, 2003).”In order for NASA’s proposed missions to become a reality, a all 12 missions will require a total of 105 to 110 Kg of Pu-238, which is equivalent to an average production rate of 5.3 to 5.5 Kg per year for 20 years (National Research Council, 2009). Ultimately, the sum of Pu-238 that the U.S. can easily produce is limited by the availability of 237Np (National Reseaarch Council, 2009). This means either U.S. policy in regards to the production of Pu-238 will have to loosen unorder to progress the future of mission and launch operations or the U.S. States will have to continue to purchase Pu-238 from Russia.
The process of burning plutonium-238 and utilizing it as a radioisotope fuel is costly under the context that it has to be purchased from other nations for the U.S. space program to continue. There are other costs as well. Costs to be considered include technology development costs in collaboration with the projected total life cycle cost of a mission. Within these cost considerations are the concerns of mission aborting methods, the cost of potential safety concerns as well as unexpected costs.
This research has to do with Nuclear Electric Propulsion systems but the article also has information on the cost of a trip to Mars. In their technical process description of nuclear verses chemical propulsion article, authors Kozdron and Tieman notes that the act of a chemical launch to Mars involves 46 mini, or additional, launches for necessary propulsion (Kozdron & Tieman, 1999). The result of this as the authors note is that there are significant savings that can be retained through implementing nuclear propulsion systems.
One core benefit nuclear thermal energy use has over “…$6.8 billion is saved using nuclear.” With over $6.8 billion in savings, this makes one wonder why nuclear powered propulsion system haven’t been implemented as a standard of the industry. Project Orion Scientists were able to find the exact percentage of lives that could be lost through the use of Pu-238 in a launch that failed. It’s test like these that extend beyond the cost effectiveness of nuclear just as a power source but analyze nuclear powered propulsion system costs and efficiency based on what researchers call safety costs, unexpected costs, and lifecycle costs.
Bromley’s studies reveal some very telling data that supports the position of this research thesis that nuclear energy is more cost efficient than chemical when it comes to transportation. The specific data Bromley refers to involves the limitation in the physical act of propulsion as it relates to Specific impulse (IS) Isp. Specific impulse (Isp) is the metric of measurement to estimate the performance level of rocket engines. Data shows that chemical rockets have an Isp limit of 500 seconds and an exhaust velocity of 4,900 meters per second (m/s). As the author states, “the maximum Isp that can be achieved with chemical engines is in the range of 400 to 500 s…a high T/W (50-75) is necessary for a rocket vehicle to overcome the force of gravity on Earth and accelerate into space (Bromely, 2001).” What this basically means is that the lighter the rocket the easier it is to launch into space and with nuclear powered systems the rocket will not have to compensate for engines, and propellant weight. In fact the advantage of using a nuclear propulsion system is that through nuclear propulsion, the Isp can actually be overcome to attain levels of up to 1000s. By this data comparing nuclear propulsion to chemically powered space craft, it’s clear that nuclear propulsion can produce twice the outcome with less weight obligation.
When there is less weight obligations required for travel, there is also less cost on development. Sample calculations for a Mars Mission show a direct comparison of cost between nuclear systems and chemical systems. This data can be used in two ways. First, it shows nuclear systems are better than chemical from a financial perspective and second it shows that there is a significant amount of money that could have been spent predominantly on the research and the development of nuclear powered propulsion. The cost difference between chemical and nuclear thermal rockets (NTR), according to Bromely, is $3 billion in costs for chemical power verses $1.3 billion in costs for nuclear (NTR) for the Mission to Mars. This is due to the fact that (NTR) relies on heat energy released by a reactor, which can be utilized in the heating of low molecular weight propellants, like hydrogen. Another benefit NTR’s provide over chemical use is that “Although solid NTR’s don’t operate at temperatures as high as some chemical engines (due to material limitations), they can use pure hydrogen propellant which allows higher Isp’s to be achieved (up to 1000 s) (Bromely,2001).
Defense policy regarding nuclear systems
The history the United States has as being the first country to develop nuclear weapons, and the only country to ever use nuclear weapons in warfare, specifically with the bombings of Hiroshima and Nagasaki during World War II, has played a major role in how it mandates policies pertaining to the use of nuclear systems. Currently, in regards to outer space use, The U.S. is working on the SBIRS program. The Infrared Space Systems Directorate mission is a mission designed specifically to develop and sustain a space based infrared surveillance system. This system will be used for tracking and targeting missiles for security purposes and enhancing battle space awareness during times of war. SBIRS, the department running this program consists of two Earth Orbit (GEO) satellites and two Highly Elliptical Orbit (HEO) payloads that ride on host satellites. The essential thing to note here is that these newly developed systems are not traditional tool for exploration, but designed by the Defense department to establish U.S. security from outer space. This is a very controversial topic, and rightfully so as the capabilities of SBIRS are very powerful. As the authors notes, “SBIRS sensors are designed to provide greater flexibility and sensitivity than DSP and can detect short-wave and expanded mid-wave infrared signals allowing the system to perform a broader set of missions. These enhanced capabilities will result in improved prediction accuracy for global strategic and tactical war fighters (“Infrared Space Systems Directorate,” 2012).” At first assessment this information comes across as a science fiction story, it represents the very factors Project Orion sought to avoid with involving nuclear powered space travel with war.
The ulysses mission teamed a space research project established by the European Space Agency and NASA to study the sun as well as its polar regions (Sholtis & Winchester, 1992).” Ulysses entailed flying by jupiter and performing pure exploration during its journey. It was concluded that solar power would not be an adequat source of energy so a nuclear power system was utilized to complete the mission (Sholtis & Wincheter, 1992).” Evaluations made involved the foresight into the potential of accidents that could result in human exposure to Pu-238 oxide. There was also a fear that potential accidents could lead to the fuel being released into the environment during prelaunch operations, “launch ascent, on-orbit deployment, orbit insertion, and the Earth escape trajectory (Sholtis & Winchester, 1992).” The authors go onto note that of all of their research data, there were preliminary reports where accidents were analyzed to access probable causes. They note these studies involved, ‘eleven key accidents that were analyzed in great detail; their probabilities, source terms, and health effect consequences were fully characterized (Sholtis & Winchester, 1992).” In regards to isotopic systems it ws found that the greatest risk of all launches that was viewed as a potential threat was the possible release of radioactive substances, as the researchers state, “the central issue associated with launch and space use of isotopic systems is the potential release of radioactive fuel material into the Earth’s biosphere as a result of an accident (Sholtis & Winchester, 1992).” The U.S. has process for reviewing and approving nuclear-powered space missions,
The core concept backing project Orion, was to create a spacecraft that could be propelled through a series of atomic explosions (Bruno, 2008). The project presented many questions such as, can we withstand the temperatures, the shock of the explosions can the space ships endure the rigors of space? It was conceived that spacecraft would need to be made of steel, and much larger that conventional design, It was found that it would take 1,000 bombs to lift Orion into space, with each one ejecting at 2-4 times per second (papa-Simil, 2011). The research methodology involved submarine engineers being called upon to asist with the construction of Orion as Freeman Dysan likened the process to riding a pogo-stick in the sense that as the ship propelled with each initial nuclear explosion, before the spacecraft is given the chance to fall back down to the ground. It was found that Orion’s use of nuclear energy allowed for such a significantly large amount of propulsion it made chemical energy in space travel obsolete (Bruno, 2008).
Life Support and Habitat
Regenerative environmental control and life support systems on the International Space Station, provide residence with oxygen, and remove carbon dioxide from the atmosphere. In addition, they remove gases that are naturally emitted by humans, specifically acetone and ammonia. As prevsiously mentioned, using SNAP-X nuclear auxillary power method to power these stations is a progressive expansion on contemporary space technology in regards to making a self sustaining space habitat for human beings. These nuclear powered systems like SNAP-X also can be utilized for advanced level life support systems or as a tool to power irrigation in addition to ventilation as Smith notes, “the reactor that produces and pumps gaseous hydrogen and oxygen through hoses to fuel cells on the station. The water produced by the fuel cells is returned to the reactor electrolysis plant for reprocessing. This E2/Q2 fuel cell conversion system also has the advantage of being compatible and synergistic with the platform life support and environmental system (Smith, 1990).” Oncepts like the International Space Station are SNAP-X auxillary powered reactor are both examples of how nuclear power is being utilized to push man’s home further into outer space, even if that location is the Moon. One concern that is rarely considered has to do with radiation caused by the sun, or other elements from space. Space stations are covered with a highly-reflective blanket called Multi-Layer Insulation (or MLI) made of Mylar and Dacron (“chview.nova.org,” 2001). These mesh sheets of Mylar are then aluminized so that solar thermal radiation can’t get through it.
Compare, Contrast, Analyze
In a comparison and contrast study, measuring chemical, nuclear thermal and fusion propulsion to move reusable orbital transfer vehicles (ROTVs), Haloulakos and Miller found supporting data that, if analyzed based on the previous mentioned facts of this paper, show nuclear energy is the ideal method for excessive cargo transportation to and from space. The study measured the ability of ROTVs capable of delivering 36 metric tons of payload through low orbit (LEO) into geosynchronous orbit (GEO). Geosynchronous orbit is most commonly identified as a circular orbit around the Earth for a period of 24 hrs (Haloulakos & Miller, 1990). The study concluded that as the system performance increases the total vehicle mass required in LEO decreases, The fusion system, however, is limited to lower thrust levels (~100kN)because of the size of the power generating equipment (Haloulakos & Miller, 1990). In laymen’s terms the study proves what Bruno had already established, that the vessel capable of producing the highest amount of force is least confined by mass or weight. It also points out that the fusion method is limited in its thrust capacity, making it incompatible with the nuclear thermal method. In summary, nuclear thermal propulsion outperforms all other methods by shear force and thrust power alone. This is also not taking into account the fact that chemical propulsion is also limited by massive power generating equipment that nuclear energy sources don’t need to utilize.
As Bromely notes the data shows, “the performance gain of nuclear propulsion systems over chemical propulsion systems is overwhelming (Bromely, 2001).” The key advantage to using nuclear powered systems is the cost efficiency they offer, as the data demonstrates they can attain significantly challenging space mission objectives for a much cheaper rate. Bromley identifies this lower cost as being due to a reduction in propellant requirements maintained by nuclear powered systems on a level that chemically powered spacecraft can’t attain. Bromley concludes his study by noting that humanity’s will to explore and develop space more ambitiously will arise and when that happens nuclear propulsion will be the most viable method to satisfying those ambitions (Bromley 2001). He cites prominent pioneer Robert H. Goddard, an American pioneer in astronautics and rocketry, made the following prophecy on October 3, 1907:
“In conclusion then, the navigation of interplanetary space depends for its solution on the problem of atomic disintegration… Thus, something impossible will probably be accomplished through something else which has always been held equally impossible, but which remains so no longer (Bromley 2001)“.
The sentiment is a sound and conscious statement about the current state of the nuclear propulsion breakthrough process occurring on a global level in regards to the present and future of space travel. It’s difficult to distinguish whether the concept itself coming to fruition is most profound or the fact that Goddard made this statement in 1907. It just shows that nuclear power in space travel has been a long anticipated event that has met it’s era.
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