PRE2019 3 Group3

General information

Information about the groupmembers and the logbooks each week can be found here.

A full list of all the references used can be found here.

Problem statement

Setting

For years now, new initiatives to colonize Mars kept popping up all over the world. Examples include Mars One [1] and SpaceX [2]. It still seems far away, but when these plans eventually become reality, Mars will likely be covered with multiple colonies within the near future. While some companies and/or countries might try to work together to build one colony, others might end up establishing their own. This behaviour can also be seen in the construction of space stations right now. While the ISS is a collaboration between multiple space agencies, China is building their own space station in the form of the Tiangong program [3]. Because of political distrust, China is not allowed to collaborate on the ISS [4]. This distrust will probably continue when the time of Mars colonies is here. Some companies also might choose to build their own colony, like Bigelow Aerospace is doing with the Genesis program [5] when looking at space stations. When these colonies are established, they will need resources to continue and expand. Delivering these resources from earth through rockets is time consuming and very expensive, so gathering as much of these materials as possible on Mars would be a better option. Ideally, these colonies would be build on locations that offer one or more of these resources, like water, building materials or minerals like copper and iron, at their site. However, these resources will eventually run out at the colony site and there is a possibility that not every resource is available at one location. This also could be a reason for having multiple colonies or a separate mining site. In this situation, trading or transporting resources between other colonies or mining sites becomes a solution. Just like countries here on earth trade with other countries to get their hands on things they can’t get in their own country, like for example oil, colonies on Mars could trade with each other to get easy access to the resources they need. Before going any further, let’s first look at reasons to choose a certain spot for a colony. To look at the different factors that determine what a good place to build a colony is, two different situations will be looked at. Firstly, there should be a good landing spot for the crew to arrive on Mars. Secondly, there should be a good location to actually start the colony. Ideally, these two locations should be on the same sport or really close to each other. For now, let’s assume the colony will be build on or around the landing spot. For a good landing spot, the landing area should be as flat as possible. According to [6] It also needs to be clear of rocks and boulders, since this would make landing dangerous and the landing area should not be too soft. It states that Mars has areas where the dust is several meters high, which is unfitted for landing. For building a colony, this also seems important. Building will be hard on areas that are too soft, since this would require better foundations. Non-flat and rocky areas can be not ideal for building, but can be worked around. [7] States that a good landing spot should be as close as possible to the equater, because this ensures that the solar arrays of the lander can deliver enough power at all times of the year and the temperature is high enough for the lander to stay warm. This factor is situational but can be really helpful when the colony will rely on solar power for generating energy. This will also decrease the power needs for warming the colony. Both previously mentioned articles say that the altitude of the area is also an important aspect. According to these articles, a lower altitude is better for landing. This means that there is more atmosphere above the land to slow down and steer for a good landing. [8] talks about food production which is another imporant aspect. In order to grow crops there needs to be useable soil at the landing site and there needs to be enough water. Water is not only important for food production, but also for drinking or even as a fuel by turning it into hydrogen. Currently, the best way to get water on Mars is by gathering ice that is located underneath the surface on Mars. Ideally, this ice will be located as close to the surface as possible, since this makes it as easy as possible to mine. The image [9] below shows the depth of the ice on the surface of Mars.

As shown on the map, the ideal location for digging up ice according to NASA is noted with the white box. This is fairly close to the north pole however, which contradicts with the earlier mentioned preference of building the colony as close as possible to the equator. This already shows that there is not one ideal location to build a colony. Different countries/companies might choose a different location for their colony. Now, let’s assume some choose to build their colony close to the north pole, in the white boxed area, because they think water is more important than other factors. Now, other countries or companies choose to build their colony close to the equator, because they know other colonies can already easily mine water. They now value the better temperatures and sunlight more because they know they can buy and/or trade with the other colonies for water. This means that the citizens of the colony need a way of transporting water from colony to colony. Another possible option could be that a company chooses to build a colony close to the equator and a seperate mining site for water. This way, they have the better temperatures and sunlight for solar power at their living area, the colony, and have a way to gather water on Mars. However, this again, brings the need for a transportation system between the colony and the mining site.

Problem

In order to trade or transport water from colony to and from another colony/mining site a way of transportation between the colonies is needed. Going out themselves is dangerous for the colony citizens. Radiation, low temperatures, dust storms and a toxic atmosphere [10] [11] [12] are all reasons to search for another solution than letting humans drive from colony to colony in person. Because of this, the colonies are in need of a transport system that does not require the citizens to go out themselves.

Solutions

There are a few solutions for this:

Option 1: Building a transportation conveyor tube.

Option 2: Building a protected manned transportation vehicle. This vehicle must be protecting the people inside from radiation and temperatures.

Option 3: Building a remote-controlled unmanned transport vehicle with cameras attached which will be controlled by someone in the colony. There must be someone controlling the vehicle.

Option 4: Building a transport robot that would be able to autonomously deliver water from the one colony to the other.

Comparing solutions

We are going to dismiss options by comparing the most important properties needed to solve the problem:

Option 1 can only transport from two static locations, while option 2, 3 & 4 are more dynamic in this aspect. Because of uncertainty of the location of the colonies in the current development it might be best to leave this one out. Also, with the big distance between colonies this could be an extremely big project that is way too expensive and would still need human help in the dangerous environment to build.

The difference between option 2 versus 3 & 4 is that if we are sending a human on the transportation vehicle or not. As stated before sending a human on the vehicle would be dangerous and would require the vehicle to be of much higher quality to ensure safety of the human inside, which is most likely much more expensive solution than option 3 & 4.

Now we are left with a remote-controlled transportation vehicle versus an autonomous transportation vehicle. The remote-controlled vehicle will be controlled by a human. This means that the human is always aware of its position and situation allowing to help with overcoming obstacles. This means that decision making will be in human hands which the users might prefer over handing the driving over to an AI. However, the remote-controlled vehicle requires a driver. Since distances could be pretty far in between the colonies/mining sites it would be a better option for the users since they don’t have to spend that much time driving and/or routing.

Because the user will most likely prefer a transportation system that does not require a driver, we have decided to go for solution option 4: Building a transport robot that would be able to autonomously deliver goods from the one colony to the other. This robot will autonomously drive to a colony or mining site and will bring back the resources for the colony. This solution can only be realised if the following objective questions have been answered.

Knowns & Unknowns

Knowns

- Location of colonies relative to each other

- Terrain

Unknowns

- Unexpected obstacles (rocks, duststorms etc)

Users

The users of a device that can navigate itself across a planet, in this case Mars, are the people that live on Mars. At the moment, there are no people living on Mars yet. This means we should look at the probability for a Mars-colony to be formed in the near future. People have always dreamed about relocating the human race to another planet, in case something would happen to planet earth. This idea generates even more interest nowadays, than it did, say, 50 years ago, with the current problem of climate change affecting the earth. Now, more than ever, people are looking for another place to live in the galaxy. One of the most prominent candidates for this migration would be Mars, because it is ‘close’ to earth in comparison to other planets. Furthermore, it is believed to have water, which is a major life source, in its soil. But are we ready to move there in the near future?

Mars One

Mars One is an organization, that certainly believes this is possible. Mars One handles the selection procedure for astronauts that want to settle on Mars in the yet to be formed space colony. It is also responsible for raising funds in order to make the mission happen. In [13] they state that the formation of a space colony, instead of a visiting mission that has to return to earth, excludes most technological and cost-intensive problems. Namely, if people want to settle on mars, no return vehicle, return propellant or the systems to produce the propellant locally are required. This decreases technological challenges and reduces costs dramatically. Furthermore, they mention that all the technologies to send people to Mars and make them survive there are already present. This means that a Mars colony is certainly feasible within the next 50 years. However, in [14] they mention that the funds to actually develop a Mars settlement mission are not present right now (1 million USD of the 1 billion USD required). On the other hand, donations and investments might rapidly increase when more research is conducted in this field, and people would get convinced that a Mars colony is feasible. Also, if the situation on earth gets worse, people might have no choice but to invest in these kinds of missions.

Technological Difficulties

Aside from the financial aspect, there are some other difficulties in conducting a journey to Mars. The most prominent ones will be elaborated here.

Distance

Mars is the planet that is closest to earth in our solar system. However, the distance that would have to be covered if we launch a manned vessel to Mars is still significantly large. On average Mars is around 225 million km from earth, with 55 million km at its closest, occurring every 26 months. This journey would take around 150-300 days, according to [15]. This is a reasonable amount of time, but the trouble lies in fuel consumption, as a manned vessel would be larger than a unmanned vessel, due to supplies that a manned mission needs. This would lead to a large fuel consumption. However, technologies are present to cover this distance in space with a manned vessel [16].

Housing

Three other factors to take in consideration are the atmosphere, the temperatures and the storms on Mars. As for the atmosphere, oxygen could be produced using the carbon-dioxide that is present in the Martian atmosphere [17]. For example, greenhouses could be built with plants that convert CO2 into O2 or a device for converting carbon-dioxide into oxygen could be developed. The temperatures range anywhere from -125°C to +20°C [18]. These kinds of temperatures are acceptable in the building of a space colony, with good isolation and air-conditioning systems. There are also severe dust storms on Mars from time to time. This means that a rigid structure needs to be built to withstand such storms.

Supplies

Once a group of people is settled on Mars, a huge challenge will be to supply them in their needs. First of all, food is needed to keep the population alive. This could be realized by both transportation of food from earth and, ultimately, growing food on Mars. Also building materials must be transported through space. This requires new rockets that can carry heavy loads. NASA is developing these spacecrafts [19]. This means that this issue, although very cost-intensive, can be technologically overcome.

In conclusion, we can say that a colony on Mars is possible in the future, because all the technologies to realize it is there. It is only a matter of further development and major investments to make this happen. This means that there will be a need for Mars-exploring robot technologies in the future.

The main users of the robots will be a Martian space colony. This colony is non-existent today. However, the idea of a Mars-colony is widely researched right now. NASA, for example, has launched several Mars-exploration-robots in the past [20] and still does extensive research on the planet today. There is also an organization that focuses solely on the development of a human colony on Mars. This organization is called Mars One and it focuses on the selection of astronauts and the raise of funding [21]. Mars One claims that all technologies to get to Mars and to begin a colony there, are already present. Only a return mission is impossible right now, but that will not be needed if the crew of the mission will settle on Mars. This means that, in theory, a Mars colony is feasible within the coming 50 years [22]. This means that the navigation technology, that we will design, is certainly of use for this yet to be founded colony.

Other parties of interest for this technology would be organizations like NASA, ESA, Space-X, Mars One, and other space-oriented companies, as they will be the organizations that will put people on Mars.

Objectives

The main goal is to give a proposal for a robot that can navigate and move on Mars from one colony on Mars to another colony on mars through known land with possible alterations autonomously in order to exchange goods and/or materials between colonies. In order to let the robot navigate autonomously, it needs to be able to do a couple of things.

- Coördinate system: Firstly, the robot needs to have a proper coördinate system to use on Mars for specifying its initial position, its goal position and possibly map obstacles on the way.

- Sense its environment and gather information: Secondly, the robot needs to be able to gather data about its surroundings to determine its world view and come up with a path. It also needs to be able to determine its location in the chosen coördinate system.

- Determine a path: When the robot has gathered its data from its surroundings it needs to be able to calculate the best path to take in order to reach its goal.

- Move from point to point: When the robot has calculated its path it needs a way of actually moving to the goal point. For this we need to research the best way to move forward on Mars. In other words, what are the best kind of tires to use for the environment or should it use tires at all?

Another objective is to create a virtual simulation demonstrating mostly the path-finding capability of the found solution. This simulation should feature a random generated terrain that is similar to that of Mars, the robot being able to sense what it would be able to in the real world, the same driving capabilities as in the real world (things like how steep of a slope the robot can overcome) and simulate the path-finding capabilities of the robot in this situation.

Milestones

- Create a coordinate system for Mars that can be used by the robot.

- Relevant specifics of Mars environment that influences the navigation are known.

- Being able to create a virtual ground environment in a simulation that is similar to Mars.

- Determining the optimal specifics of the robot and it's sensors.

Deliverables

- Research on all relevant topics/objectives.

- Suggestions for a (best) solution for each objective.

- Virtual simulation

- Presentation

Who will do what?

For the beginning of the project each groupmember will focus his studies on a certain area. The work division is as follows:

- Finn will focus on determining how the environment of Mars looks like and how this can be recreated in the virtual simulation.

- Nick will focus in getting a coördinate system usable for location on Mars & look at its planetary properties.

- Rik will focus on the (potential) user studies of this topic.

- Stefan will focus on how the robot will travel on Mars and determining how the robot will see its environment, in other words, which sensors does it needs and how does it create an image of its surroundings.

- Zeph will focus on the virtual simulation and thinking about how the robot will determine its path.

Planning

Week 1: Decided on a subject for the project.

Week 2: Work on plan and finish research.

Week 3: Implement findings of research into wiki.

Carnaval

Week 4: Potentially Choose experiment and execute experiment.

Week 5: Potentially Implement findings of experiment.

Week 6: Work on wiki.

Week 7: Work on wiki.

Week 8: Finish presentation. STILL HAS TO BE CHANGED

State of the art

Navigation

[23] This paper describes multi createria dicision making methods for autonomous navigation for ground robots. According to the paper, this method should be able to let the robot make more precise alternative evaluations and minimize the probability the robot will be stuck or collide with objects.

[24] This paper is focused on underground mining. Uses four-wheel vehicles that minimizes curvature variation in the path it takes and stays in a certain safety margin from the mine walls. It presents a study that uses a B-spline for path determination. A B-spline (or basis spline) is a spline function. This means that the function can be reconstructed by connecting different polynomials. All possible spline functions can be reconstructed by connecting different B-spline functions.

[25] The focus of this paper lies on aerial robots in an underground mine. These aerial drones use both visual and thermal cameras to ensure a good understanding of the surroundings in order to map in these dark, dust-filled areas.

[26] This paper describes a framework for terrain characterization and indentification. This framework is composed of vision-based classification of upcoming terrain, terrain parameter identification via wheel-terrain interaction analysis and acoustic wheel-terrain contact signatures based terrain classification.

[27] This paper provides a new solution to the simultaneous localization and mapping problem with six degrees of freedom. he additional three degrees of freedom are yaw, pitch and roll angles. A robot on a natural surface has to cope with all of these degrees of freedom. With this solution an autonomous mobile robot can create a 3D map of a scene such as a mine or a cave.

[28] This article shows the parts of planet Mars that the robot is most likely to be on in case of harvesting missions.

[29] Mars orbital data explorer

Mars Terrain

[30] This paper investigates the slope distribution in the northern hemisphere of Mars from topographic profiles collected by the Mars Orbiter Laser Altimeter.

[31] This paper describes the calculation of slopes and the characterization of surface roughness using profiles obtained by the Mars Orbiter Laser Altimete.

OLD STATE OF THE ART:

General

[32] NASA plans to use multiple mining robots together in order to supply a colony with materials. These robots should work together in a "swarm". They will work individual first, but when one robot finds something interesting it will call the other robots in order to help it with extraction.

[33] Competition for students to build mining robots. Maybe a good place for inspiration.

[34] Maybe interesting. Not looked at yet.

[35] NASA page including all kinds of information sources about space colonies.

[36] Space Settlements: A Design Study. Includes information about all aspects of a space settlement including resources needed to maintain and expand.

[37] What do we need to know to mine an asteroid? States that science is nearly able to develop a space mining technology, only further knowledge of asteroid contents is needed.

Locating and mining materials

[38] While not about robots, this paper presents the method of using a detailed world model of the geological structure of the ground in order to locate different ores in the ground. It uses different sensors across the mining area, which could be placed on a robot which moves around, in combination with a supervised learning algorithm to build this world model. ~Might be interesting. No access to full paper yet however.

[39] This paper describes methods to build the spectral library to map geology on minefaces. The library includes multiple environmental conditions such as the inclusion of shade and moisture. Such a spectral library can be used by autonomous mining robots to identify different materials.

[40] In this paper an automated technique that allows a robot to classify the shape and other geological characterics of material from a 2D photographic images and stereographic data. This technique first seperates the material from the background after which various metrics are used to classify the materials sphericity, roundness, and other geometric properties.

[41] In this paper a new automated geological perception system is presented. It detects and classifies geological structures by using hyperspectral imaging sensors and a learning algorithm. Ultimately the system builds a rich model of the operating environment which can be used in autonomous mining.

[42] This paper gives information about an economically favourable mining technique called Optical mining. This method of mining will provide affordable mission consumables and radiation shielding.

[43] Asteroid Mining. Explores possibilities for space mining on asteroids. This paper comes to the conclusion that a solar powered mining vehicle, that runs on water and that mines water and platinum group metals, would be potentially feasible in the near future.

[44] Asteroid Mining. States how far we are on developing space mining technology. This might happen within a decade, once a cost-effective method is found. Also addresses financial, environmental and legal issues.

Transporting materials

[45] June 26, 1951 R. w. GAUSMANN APPARATUS FOR TRANSPORTING MATERIALS 5 Sheets-Sheet 1. Is about a technique for for transporting materials without changing the compounds temperature which may be necessary to prevent chemical changes in the material being transported, or to prevent it from solidifying within the car whereupon it would have to be heated to be removed therefrom.

[46] Describes a bag with means for vacuuming an internal space of the bag. This can extend the lifetime of organic matter.

[47] Extraterrestrial construction materials by M.Z.Naser. This review explores the suitability of construction materials derived from lunar and Martian regolith along with concrete derivatives, space-native metals and composites, as well as advanced and non-traditional materials for interplanetary construction.

[48] Space-native construction materials for earth-independent and sustainable infrastructure. This review covers feasibility of exploiting in-situ lunar and Martian resources as well as harvesting of elements and compounds, from near Earth objects (NEOs), to produce extraterrestrial materials suitable for construction of space-based infrastructure.

[49] Materials and design concepts for space-resilient structures. This paper presents a state-of-the-art literature review on recent developments of “space-native” construction materials, and highlights evolutionary design concepts for “space-resilient” structures.

Society

[50] Societal challenges in sustainable space mining. This article focuses on sustainable space mining and the issues it brings up. Potential issues are: 1) Legal issues 2) Issues in investment 3) International disputes 4) Environmental protection.

[51] Space Law in Asteroid Mining. In order to ensure legitimate space mining, countries need to update their own legislation and cooperate internationally in this area.

Research

Relevant information about Mars

General

Mars is a relatively small planet in the Solar system with a surface area of 144.798.500 squared kilometres. The highest point on Mars, the summit of Olympus Mons, is at 21.229 meters above the Mars areoid, and the lowest point on Mars, the bottom of the Hellas impact basin, is at 8,200 meters below the Mars areoid. This makes the topographic range of Mars 29.43 km while Earth has a topographic range of 19.7 km, meaning Mars is much 'rougher' in comparison with Earth. The Mars areoid is defined at a radius of 3.396.000 metres from the centre of mass. It is an useful measurement to define elevation. Mars has a equatorial radius of 3.396km and a polar radius of 3.376km.

An easy way to map coordinates is by using longitude and latitude coordinates.

On this map you see we can divide positions in x & y coordinates using a Cartesian coordinate system. 1 degree longitude = 59.27 km (x-axis), 1 degree latitude = 58.923 km (y-axis) The difference between the two numbers is caused between the difference in polar radius and equatorial radius.

Slope distribution

Median Slope

The median slope differs based on the based on the baseline length, the length over which the height difference is measured, which is used while calculating the median slope. The graph shown below shows the median slope of different geological formations based on the baseline length which ranges from 0.1 to 100 km [52]. The graph shows that the median slope decreases the higher the baseline length.

Steep Slopes

For kilometer-scale baselines, slopes steeper than the angle of repose, the steepest angle of descent relative to the horizontal plane to which a material can be piled without slumping, are scarce. In the complete MOLA (Mars Orbiter Laser Altimeter) data set there are a total of 105 point-to-point segments have slopes steeper than 35 degrees. 9 of these are probably data errors. The slopes of steep segments are sorted according to some feature classes in the table shown below [53].

Virtual simulation

Which software?

The goal of the simulation is to simulate the path-finding behaviour of a robot in a three dimensional environment. As seen in the objectives, this simulation should feature a random generated terrain that is similar to that of Mars, the robot being able to sense what it would be able to in the real world, the same driving capabilities as in the real world and simulate the path-finding capabilities of the robot in this situation. The first thing that should be established is the software that will be used for the simulation. While there are many programs for simulation the two main options that jumped out were NetLogo and Unity. Both these programs are easy to use and can be used for three dimensional simulation. First lets look at NetLogo. NetLogo offers the basic tools to build a single- or multi-agent simulation. While mainly made for two dimensional simulations it has a three dimensional option that allows for simulation in a three dimensional environment. However, according to the developers themselves, this three dimensional version is not up to the standards of the main two dimensional software [54]. Even though NetLogo allows for quick setup of a simple simulation of agents, it seems very limited in building environments for the agents to exist in. For this reason, its simplicity is both its strong point and its weakness. The other option is Unity. While Unity is made for game development it could also serve as a great platform to build a simulation. It offers great tools to generate a three dimensional environment and has very little limits in what can achieved. While it is more work to have a simulation up and running in Unity as compared to NetLogo, Unity seems like the better option. There will be almost no constraints while making the simulation.