In the year 2038, after 18 months of life and work on the surface of Mars, a team of six researchers sits back in the spacecraft and returns to Earth. Not a single soul remains on the planet, but the work does not stop here for a minute. Autonomous robots continue mining operations on Martian Soil and deliver them for processing to the chemical synthesis factory, which was built several years before the human set foot on Mars. The factory produces water, oxygen and rocket fuel from local resources, routinely preparing reserves for the next expedition, which will arrive here in two years.
This robotic factory is not science fiction. This is a project which several scientific teams of the NASA aerospace agency are currently working on. One of them, Swamp Works, works at the Kennedy Space Center in Florida. The installation they officially develop is called the “In situ resource utilization system” (ISRU), but the people who work on it are accustomed to calling it a dust collecting factory, because it converts ordinary dust into rocket fuel. This system will allow people to live and work on Mars, and also to return back to Earth if necessary.
Many research and engineering teams at NASA are working on solving various aspects of this problem. For example, the Swamp Works team from the Kennedy Space Center has recently began assembling all the individual modules of a mining system. The installation is an early prototype, but it combines all the details that will be necessary for the operation of a dust removal plant.
NASA’s long-term plan is aimed at the colonization of Mars, but now the agency has concentrated all its strength and attention on the Moon. Thus, most of the developed equipment will be tested first on the lunar surface, which in turn will allow solving all possible problems in order to avoid them in the future when using the installation on Mars.
Dust and dirt on an extraterrestrial space body are called regolith. In general terms, it is a volcanic rock, which for several million years under the influence of various weather conditions turned into a fine powder. On Mars, under a layer of corrosive iron minerals, which give the planet its famous reddish tint, lies a thick layer of silicon and oxygen structures connected to iron, aluminum, and magnesium.
On Earth, for mining, we usually use large machines. Their size and weight allow people to make enough effort to “bite” into the ground. Carrying on Mars will be absolutely unallowable. Remember the cost issue? With every gram that will be sent to Mars, the price of the entire launch will constantly increase. Therefore, NASA is working on the way to produce minerals on the Red Planet using the lightweight equipment.The RASSOR (Regolith Advanced Surface Systems Operations Robot) is a standalone earner designed for the sole purpose of digging regolith under low gravity conditions. When developing the RASSOR, NASA engineers paid special attention to its power drive system. The latter consists of motors, gears and other mechanisms that make up the bulk of the entire installation. It uses frameless engines, electromagnetic brakes, and, among other things, 3D-printed titanium cases to minimize the overall weight and volume of the structure. As a result, the system has about half the weight, compared to other machines that have similar technical characteristics.
For digging, the RASSOR uses two opposition drum buckets, each with several teeth to grip material. When moving, the machine drum buckets rotate. The drives that hold them down, and the drums, hollow inside, literally cut off the upper layer of the surface regolith. Another key feature of the RASSOR is the boxer design – the drums rotate in different directions. It allows not to apply great effort to the soil in the conditions of low gravity.
You may be wondering: “Isn’t the Martian regolith originally dry?” Dry, but not everywhere. It all depends on where and how deeply you dig. In some areas of the planet, just a few centimeters below the surface, there are whole layers of water ice. Even lower may be lime sulfate and sandstones, which may contain up to about 8 percent of the water of the total mass of the massif.
After condensation, the spent regolith is thrown back to the surface, where the RASSOR can pick it up and take it to a place more distant from the factory. This “waste” is actually a very valuable material, because from it, using 3D printing technologies, which are currently also being developed at NASA, it will be possible to create shelters for the settlement, as well as roads and landing sites.
Steps of mining on Martian soil in pictures:
- Development: The wheeled robot produces a regolith fence by rotating buckets with fence holes
- Transportation: Reverse buckets-drums unload the regolith into the robotic arm of the factory.
- Recycling: To extract water from the regolith, it is heated in a furnace where electrolysis of hydrogen and oxygen occurs.
- Transfer: After receiving a certain volume of a substance, another robotic arm, equipped with a special protective closed system, loads it onto a mobile robotic tanker.
- Delivery: A tanker delivers water, oxygen, and methane to people’s homes and unloads them into long-term storage tanks.
- Use and storage: Astronauts will use water and oxygen for breathing and growing plants; fuel will be stored as cryogenic liquids for future use.
All the water that will be extracted from the regolith will be thoroughly cleaned. The cleaning module will consist of a multiphase filtration system, as well as several deionizing substrates.The liquid will be used not only for drinking. It will become an essential component for the production of rocket fuel. By splitting H2O molecules using electrolysis into hydrogen (H2) and oxygen (O2) molecules, and then compressing and converting to liquid, it will be possible to synthesize fuel and oxidant that is most commonly used in liquid rocket engines.
The difficulty lies in the fact that liquid hydrogen must be stored at extremely low temperatures. For this, NASA wants to convert hydrogen into the kind of fuel that will be the easiest to store: methane (CH4). This substance can be obtained by combining hydrogen and carbon. Where to extract carbon on Mars?
Fortunately, there are a lot of them on the Red Planet. The Martian atmosphere is 96 percent of carbon dioxide molecules. Carbon is the task of a special freezer. In simple terms, it will create dry ice from the air.
Another interesting part of the processing plant is an umbilical robotic arm for transferring liquids to the tank of a mobile tanker. In this system, it is specifically protected from the external environment and in particular dust. The regolith dust is very fine and can penetrate almost everywhere. Since regolith itself consists of crumbled volcanic rock, it is very abrasive (it clings to virtually everything), which can create serious problems for the operation of equipment. NASA’s lunar missions have shown how dangerous this substance is. It violated the testimony of electronics, led to jamming mechanisms, and also became the cause of failures in the temperature controllers. Protection of electrical and liquid transmission channels of a robotic arm, like any very sensitive electronics, is one of the highest priorities for scientists.
On each side of the umbilical chamber, mounted on a robotic arm, there are doors that act as airlocks, protecting all internal channels from dust. To connect the chamber with the tanker mechanism, three steps are required: first, after filling the chamber, it is necessary to securely close the doors on both sides in order to create a protective anti-dust barrier. Secondly, in each of the doors of the umbilical chamber, it is necessary to open small sealing openings, through which access to the resource transfer channels installed on a special moving plate will be provided. Thirdly, it is required to align the position of the transmission channels of the umbilical chamber and the channels of material reception by the tanker mechanism, precisely connecting both electric and liquid connectors to each other.
Recently, engineers have engaged in the development of this project conducting a test demonstration of the installation in Florida. At this stage, scientists had to resort to modeling the processes of electrolysis and the furnace itself to reduce costs and installation complexity. In addition, a simulation of the production of three processed products using water was carried out. But in this case, prototypes of both hardware and software were used for all parts of the installation.
By combining all the parts together, Swamp Works engineers were able to determine the presence of certain problems in the design, as well as identify some important details that would be impossible to determine if such tests were carried out at the last stages of development and integration. According to the developers, rapid prototyping and early integration are a distinctive approach to the work of their team. Due to it, it is possible to quickly find out the performance of a particular idea, as well as identify all the existing shortcomings at an early stage.
The essence of the Martian rocket-fuel factory is that all this equipment will be packed in a small convenient box, delivered to the Red Planet, and then it will be unpacked on its own and begin to perform its task long before the first humans arrive on Mars. The development of manned expeditions to Mars will depend on the effectiveness of this autonomous factory. After all, without it, people will not be able to return back to Earth at the end of their watch. In addition, NASA also has teams that deal with the cultivation of all kinds of food (including potatoes). The new crop is planned to be grown again in an autonomous way while sending the Mars people and their flights back to Earth so that people will always have a fresh crop.
In general, the project is truly gigantic and requires careful preparation. NASA has a large stock of experience with autonomous rovers and landing modules on Mars. For example, the most recent rovers, the Curiosity, which landed on the Red Planet in 2012 and the Mars 2020, which will go there in 2020, possess and will have a high level of autonomy. However, the creation, delivery, and use of the Martian rocket-fuel factory in the long term and with a maximum level of autonomy will require the use of such technologies that will take space engineering to a completely new level.
To begin space colonization, scientists and engineers have to solve many technical problems. For example, it is very important to determine whether each developed subsystem of an installation for extracting natural Martian resources for scaling. It should be able to meet all needs and reach the level of capacity that will be needed in the framework of the manned missions to the Red Planet.
According to recent calculations by NASA, a similar system in about 16 months should produce about 7 tons of liquid methane and about 22 tons of liquid hydrogen. On this basis, for maximum return, it is necessary to very accurately determine the most suitable places for the deployment of a factory for the collection and processing of resources. In addition, it is necessary to calculate how many RASSOR excavators will need to be delivered to Mars, as well as how many hours per day they will need to work in order to reach a given production plan. They should understand how large the carbon freezer and the Sabatier reactor they need, and how much all this energy will consume.
Also, scientists need to anticipate possible additional problems that could interfere with the extraction and processing of resources, potentially delaying the dispatch of the next expedition to the Red Planet. It is necessary to evaluate all possible risks associated with these problems and to develop in advance the correct and fast ways to solve them, possibly equipping the system with duplicate elements for temporary replacement of the failed equipment.
It is necessary to make sure that robotized technologies will be able to support operational activities without stopping and needing maintenance for several years, therefore their development will be carried out in strict accordance with the established standards.
Scientists also have to figure out how and in what proportions the fine and solid regolith is mixed with ice under the surface of Mars. This data will help prepare excavators for resource extraction more efficiently. For example, the current version of the RASSOR bucket is best suited to collect regolith mixed with lump ice. However, this design will be less effective if it is necessary to “bite” into larger layers of solid ice. To develop more suitable equipment, it is necessary to get an accurate idea of the distribution of ice on the Mars. Another option is to develop more durable, more complex, heavier and more versatile equipment that can work with any kind of soil and density of ice layers. But, again, these are extra expenses.
Still, it is necessary to solve the questions connected with long storage of supercooled liquids. The technology for storing substances and materials under high pressure is constantly being improved, but can modern technologies work on the surface of Mars for a long time?