Mars

Within this chapter, the power systems developed and applied in Mars surface exploration applications are discussed in four different time domains:

At first, an overview of the Mars missions conducted within the different time domains is given. All Mars missions launched within the investigated time domains will be presented; this includes fly-by probes, orbiters, and landers.

The design of both photovoltaic and photothermal systems operating on Mars requires detailed information on the solar radiation flux incident on the surface of the planet as a function of latitude, longitude, time of day and year. The atmospheric (vertical) optical depth τ is an indicator of solar radiation attenuation in the atmosphere. One can concisely define the optical depth as follows. Let us assume that the sun is at zenith and denote by I ₀ and I _ground the direct solar irradiance at the top of the atmosphere and at ground level, respectively. Then, usage of τ allows to write the Beer’s law as \({I_{ground}/I_{0}=e^{-\tau}}_{-}\) Suspended dust absorbs solar radiation and emits (and absorbs) longer-wavelength radiation. Mars may be considered ”clear” when the dust content in the atmosphere is low, but when local or global storms occur the optical depth increases and the direct beam solar radiation decreases drastically.

Among the different solar space power systems to be used on Mars a leading position is played by the photovoltaic (shortly, PV) solar cells. Due to their relatively low cost power, high reliability and the lack of moving parts they powered the space program from the very beginning (Landis and Appelbaum 1991). As a result the array manufacturing technology is now well developed, and the technology is well characterized for vibration, thermal-cycling, and other environmental loads of the space environment. A number of studies concerning the usage of PV cells on the Mars surface have been performed during the years and we quote here some of them. A rover powered by a PV array was designed in Hibbs (1989). To add robustness, a fixed array rather than one which tracks the sun was envisaged, because of the modest power requirements (275 Watt average power and peak power capability of up to 2000 W during climbing over large boulders). The array surface was as large as 7 m². Another study refers to a long-endurance, remotely piloted aircraft capable of flight within the Martian environment (Colozza 1990). There is a variety of mission scenarios which would be possible with this aircraft ranging from magnetic and gravity field mapping to surveillance / reconnaissance missions. The flight duration would be on the order of one year. The power and propulsion systems consist of solar PV array panels, a regenerative fuel cell and an electric motor. Depending on the solar cell type the required PV array surface could be quite large (from 336 to 405 m² in case of silicon-based solar cells or from 118 to 166 m² when gallium arsenide PV arrays are used). A solar power system for a 40 day manned Mars surface scientific expedition was studied in McKissock et al. (1990). The electrical power requirements were assumed to be 40 kW for life support and experiment power during the Martian day and 20 kW for life support during the Martian night. The solar energy system consisted of roll out amorphous silicon arrays and a hydrogen - oxygen regenerative fuel cell energy storage system. The total array covers 2822 m² when deployed and has a blanket mass of 177.6 kg.

Solar energy is one of the most promising clean energy sources. For Earth applications, numerous technologies utilizing the photovoltaic effect, ranging from cellular phones to geostationary satellites, have been developed. The solar radiation reaches the Earth’s upper atmosphere at a rate of 1,366 W/m² (NREL 2006, 2009). While traveling through the atmosphere, 6% of the incoming solar radiation (insolation) is reflected and 16% is absorbed, resulting in a peak irradiance at the equator of 1,020 W/m² (NASA 2006). Average atmospheric conditions (clouds, dust, pollution) reduce insolation by 20% through reflection and 3% through absorption. In North America the average insolation lies between 125 and 375 W/m² (3 to 9 kWh/m²/day).

For many years space researchers realized that in some specific situations solar dynamic power systems can provide significant savings in life cycle costs when compared with conventional photovoltaic power systems with battery storage (Menetrey 1963; Secunde et al. 1989; Prisnjakov 1991; Prisnjakov et al. 1991). A standard solar dynamic power system uses a mirror to concentrate solar radiation onto an absorber structure. By conduction through a solid material or circulation of a working fluid, the absorber heat is transferred to a thermal engine (i.e. a turbogenerator, Stirling engine, termocouple or thermionic-emitter). Alternators coupled to these thermal engines may generate electrical energy. Previous practice proved that three different cycles can be used for thermodynamic conversion of solar radiation: Brayton, Rankine and Stirling (Menetrey 1963; Prisnjakov 1991; Prisnjakov et al. 1991). For continuos operation during dark periods the use of melted materials to store thermal energy is being considered. Among the advantages of dynamic power systems one could quote their ability to provide electrical energy and heat simultaneously, the fact that the power plant may be unified by using either solar or nuclear energy or their relative invulnerability to corpuscular particles and to electromagnetic radiation and the possibility of power control according to a given power consumption schedule (Prisnjakov 1991).

Fuel cells have played a key role in manned space exploration since the 1960s. Alkaline fuel cells have powered the Apollo spacecraft, safely taking men to the Moon and back, and still provide electrical energy to the Space Shuttle Orbiter today. Recent advances in fuel cell research have provided promising new cell materials and technologies. It will only be a question of funding and time until these scientific advances can be successfully turned into durable and reliable systems designed for even the most challenging applications in space exploration.

Among the available energy alternatives nuclear power offers important advantages and in many cases is the only viable alternative given actual operation conditions on Mars. We know that nuclear is the most compact form of energy available. Nuclear power is required at every step of space exploration as a backup form of energy ready to be delivered when all other energy sources cease to deliver. Unfortunately, it also has a number of drawbacks.

One of the fundamental needs for Mars colonization is an abundant source of energy (Shaban and Miley 2003). The total energy system will probably use a mixture of sources based on solar energy, fuel cells and nuclear energy. Here we concentrate on the possibility of developing a distributed system employing advanced nuclear energy, specifically a mixture of small fusion devices and low energy nuclear reaction (LENR) cells (Miley 1997; Miley et al. 2002a). The fusion devices would provide small central units in the 500 kWe - 1 MWe level. The LENR units would serve as small portable sources ranging from Watts up to kiloWatts. All units would be designed to minimize radiation emission and radioactive waste.

Mars represents the first big extraterrestrial step of mankind. This is a very important historic moment representing the beginning of the cosmic age. This step and the steps that follow cannot be done without strong, compact reliable power sources. Nuclear power is the strongest contender for life support systems on Mars. The importance and advantages of nuclear power sources is shown in Fig. 9.1.

The very rarefied Mars atmosphere and the low gravitation allow implementation of various technologies difficult to accomplish on Earth. Two projects based on such technologies are described in this chapter, related to energy delivery and transportation.

This contribution will concentrate on the implications of data from new studies of Mars during the past decade or so in terms of martian geothermal resources, and the potential differences in exploiting geothermal resources on Mars from our terrestrial experiences. An excellent discussion of the utility of geothermal energy on Mars was given by Fogg (1996), who makes strong arguments for the practicality of using geothermal energy on Mars with respect to other potential energy sources: these arguments will not be repeated here.

Human missions to the surface of Mars have inspired engineers, scientists, and the wider public for generations. The 20^th century has seen these dreams become attainable, with numerous realistic missions proposed, starting with the architecture proposed by Wernher von Braun in his 1953 book “The Mars Project” (von Braun 1961). Many architectures and concepts for carrying out surface missions have since been proposed, culminating in the Mars design reference missions developed by NASA in the 1990s (Hoffman 1997, Drake 1998, Hoffman 2001, Portree 2001, Drake 2007) and associated follow-on studies as part of the US Vision for Space Exploration (NASA 2005, Drake 2007). Two main motivations for carrying out Mars surface missions have been described in these architecture studies: (1) the scientific exploration of Mars, in particular with regard to extraterrestrial life, and (2) the investigation of the habitability of Mars in the context of establishing a long-term human presence there someday in the future.

On Mars, as it has been on Earth throughout recorded history, the prosperity and freedom of action of human population will be dependent, necessarily, on the availability of energy. As such, it is of central importance that the methods by which such energy is collected, generated, stored, converted, transmitted, and ultimately utilized, be thoroughly examined. This book has been written with the intention of beginning such an examination.

Mars missions to date have interrogated the planet at very large scales using orbital platforms or at very small scales intensively studying relatively small patches of terrain. In order to facilitate discovery and eventual utilization of Martian resources for future missions, a strategy that will bridge these scales and allow assessment of large areas of Mars in pursuit of a resource base will be essential. Long-range surveys of in-situ resources on the surface of Mars could be readily accomplished with a fleet of Tumbleweeds - vehicles capable of using the readily available Martian wind to traverse the surface of Mars with minimal power, while optimizing their capabilities to perform a variety of measurements over relatively large swaths of terrain. These low-cost vehicles fill the niche between orbital reconnaissance and landed rovers, which are capable of much more localized study. Fleets of Tumbleweed vehicles could be used to conduct long-range, randomized surveys with simple, low-cost instrumentation functionally equivalent to conventional coordinate grid sampling. Gradients of many potential volatile resources (e.g. H₂O, CH₄, etc.) will also tend to follow wind-borne trajectories thus making the mobility mode of the vehicles well matched to the possible target resources. These vehicles can be suitably instrumented for surface and near-surface interrogation and released to roam for the duration of a season or longer, possibly on the residual ice cap or anywhere orbital surveillance indicates that usable resources may exist. Specific instrument selections can service the exact exploration goals of particular survey missions. Many of the desired instruments for resource discovery are currently under development for in-situ applications, but have not yet been miniaturized to the point where they can be integrated into Tumbleweeds. It is anticipated that within a few years, instruments such as gas chromatograph mass spectrometers (GC-MS) and ground-penetrating radar (GPR) will be deployable on Tumbleweed vehicles. The wind-driven strategy conforms to potential natural gradients of moisture and potentially relevant resource gases that also respond to wind vectors. This approach is also useful for characterizing other resources and performing a variety of basic science missions. Inflatable and deployable structure Tumbleweeds are wind-propelled long-range vehicles based on well-developed and field tested technology (Antol et al., 2005; Behar et al., 2004; Carsey et al., 2004; Jones and Yavrouian, 1997; Wilson et al., 2008). Different Tumbleweed configurations can provide the capability to operate in varying terrains and accommodate a wide range of instrument packages making them suitable for autonomous surveys for in-situ natural resources. Tumbleweeds are lightweight and relatively inexpensive, making them very attractive for multiple deployments or piggybacking on larger missions.

As the exploration of the solar system by the international space agencies (NASA, ESA, JAXA and others) continues to expand there are increasing considerations to include humans as part of the future missions. These missions may consist of short term site visits as was done during the landing on the Moon or for extended stay as part of permanent human habitation. At the present time, the planetary body that is considered for a permanent habitation is the Earth’s Moon. However, human presence on the Moon is also sought as part of a broader plan where it would serve as a stepping stone to colonizing other bodies in our solar system, the most intriguing one being Mars. Such a presence is quite challenging and will require the establishment of the critical infrastructure to support the essential capabilities that are often taken for granted on Earth. The tasks enabling human settlement will be quite complex due to the harsh conditions on Mars such as low temperature, atmospheric pressure, and the radiation environment. In addition, long communication delays will significantly impact the ability for any system to be teleoperated from Earth. The cost and associated challenges will require cooperation of the international space agencies and this may follow some of the approaches and procedures that were used in the development and operation of the International Space Station (ISS).

The surface of the planet Mars exhibits a world of reddish rock, soil, and dust as revealed by Mars landers (Fig. 17.1). Such an environment is quite distinct from the earth except for the desert areas and the big question is whether we are able to find or produce soils suitable for agriculture on Mars. If we send astronauts to Mars, they will have to stay for 18-24 months.

Mars is the second target of our manned space flight next to the Moon, and possibly the most distant extraterrestrial body to which we could travel, land and explore within the next half century. The requirements and design of life support for a Mars mission are quite different from those being operated on near Earth orbit or prepared for a lunar mission, because of the long mission duration. A Mars mission must include at least 2.5 years for round trip travel, and a restricted opening of the launch window, both for forward and return flights once every two years. Precursor manned mission to Mars might be conducted with a small number of crew and a conservative life support system on the space ship. Once the scale of the manned mission is enlarged, an advanced bio-regenerative life support system provides an “economical” advantage over the open loop life support, based on cost comparison between the cumulative sum of consumables with the open loop system versus the initial investment for a recycling system. We further propose use of on-site resources to supplement loss of component materials in the recycling process. Reproducing recycling materials on an expanded scale is another advantage of the use of on-site resources for space agriculture.

Immediately upon arrival to the Martian surface, Martian travelers or settlers require some type of habitat on the Martian surface. First of all habitat is necessary for respiration with air pressure maintained inside, for shielding against cosmic radiation, and in case of emergency, for reserve as a safe heaven.

The idea of colonizing Mars has long intrigued both scientists and laymen as reflected in fiction and in non-fiction writings, in books, in magazine articles, in scientific journal articles, in movies, and in popular websites. The author’s purpose in this chapter is not to review in detail the extensive, extant literature, but rather, from the perspective of a multi-disciplinary scientist with commercial mining experience, to share some thoughts pertaining to the utilization of two of the major Martian natural resources, iron and carbon dioxide, each of which has been discussed in the literature (Hepp et al. 1991; Landis 2009).

Space colonization makes sense if we humans will be able to renew life and humanity beyond the Earth. We can foresee the possibility of human growth on the Martian surface since this planet has an environment that could be suitable to host humans and some other organic organisms (Bennett et al. 2003, Tokano 2005). The relative similarities from Earth - including the availability of ground ice on Mars, a Martian rotational period of only 37 minutes longer than 24 hours, and the presence of Mars seasons much like those on Earth (though about twice longer because the Martian orbital period is 1.88 Earth years), can make Mars arguably an ideal hospitable planet. There are also important differences to consider in any future Mars colonization. A low average surface temperature of -53°C due to the Mars eccentric orbit, the reduced atmospheric pressure of 0.005 bar, and a surface gravity of a little more than one third that of the Earth, namely g_Mars=3.7 m/s² (or 38% of the mean gravitational acceleration on Earth).

This chapter has two independent sections, important to Mars resource utilization. Section 23.2 refers to inflatable domes for Mars as well as for Mars satellites. Section 23.3 is devoted to the proposed AB method of agriculture on Mars without added water (based on a closed-loop water cycle). Both sections are based on a common idea, i.e. the isolation of a limited area by a cheap transparent inflatable dome and creating more suitable conditions (in other words, micro-terraforming) inside this dome for humans and agriculture.

Introduction The history of Polar exploration on Earth provides two important lessons for future manned missions to Mars:

1. Use the best technology available

2. Live off the land

Sadly, British Polar expeditions tended to ignore both rules. Scott’s South Pole expedition violated Rule #1. They man hauled their sleds because they considered it more noble technology than using dogs. When their supplies ran out, they froze to death. Meanwhile, Amundsen’s party raced to the Pole by dog sled, throwing away surplus food on their way back. Sir John Franklin’s expedition to find the Northwest Passage perished when they violated Rule #2. They lived on the tinned food they had brought from England, ignoring the nearby healthy Eskimos who lived off the land. Eventually they starved to death helped along by lead poisoning from their tinned containers.

Terrestrial geo-engineering is currently being explored as a large-scale venture to mitigate against rapid terrestrial climate change due to anthropogenic carbon emissions. A range of schemes have been proposed, including the use of orbiting solar reflectors to reduce solar insolation to compensate for increased radiative forcing of the climate (Early 1989; Angel 2006). While the scale of endeavour required to deploy geo-engineering schemes is impressive, on an even more ambitious scale the same technologies which can be envisaged to engineer the Earth’s climate can be scaled to engineer the climate of Mars. Such terraforming schemes (engineering an Earth-like climate) have long been discussed, although the concept became somewhat more mainstream with the work of Sagan and others (Sagan 1961, 1973). Bioengineering schemes have been proposed, including the delivery of customized organisms to convert carbon dioxide to oxygen in the atmosphere of Mars, and darkening the Martian polar caps to reduce their albedo, again using customized organisms. Halocarbons synthesised on Mars have also been considered as a tool to quickly raise the surface temperature and so liberate trapped carbon dioxide (Gerstell et al. 2001; Badescu 2005). For other details see Chap. 26.

As the means of safe transportation between Earth and Mars is technically developed, one of the outcomes will likely be assisted colonization of Mars. In this chapter we shall exemplify potential actions under a suite of possible future Mars settlement scenarios. The focus is on the means of providing human colonies with a vital resource: water.