Sunday, April 15, 2012

How to populate the Moon & Mars quickly


"Failure to terraform Mars constitutes failure to live up to our human nature and a betrayal of our responsibility as members of the community of life itself." – Robert Zubrin, The Case for Mars

NASA is currently looking for input from the public on future space missions to Mars. So, since I firmly believe that we’ll eventually solve the problem of “energy production vs. the environment” here on Earth, I think that it’s important to focus ahead on where we can grow life in the future. It’s not enough for us to just grow life on Earth. We need to also grow life on other planets, and a good first step to growing life on planets is to start populating the Moon & Mars with self-replicating solar automatons. A self-replicating solar automaton (i.e. solar auxon) is a robot that converts solar energy into electricity and uses only electricity and the materials on the Moon or Mars to make copies of itself. It’s like a silicon-based version of photosynthetic bacteria.

To make a copy of itself, a solar auxon has to make solar cells as well as computer hardware that controls its movements. Luckily, both solars cells and computer chips can be made from silicon, an abundant element on both the Moon and Mars. The goal of this post is to discuss the steps required to start populating life on other planets or on the Moon. I’ll first quickly list the steps required to populate Mars, and then go into more details through the rest of the post on how to populate Mars or the Moon.

Step#1:  Lower the cost of accessing space through the use of a multi-stage aero-rocket propulsion system.
Step#2:  Send over materials to initiate the growth of self-replicating solar auxons, and then let the solar robots start reproducing.
Step#3: Send over a working lab to generate CFCs and other greenhouse gases from materials on the surface of Mars. The lab will require electricity generated by the solar auxons.
Step#4: Emit the newly formed greenhouse gases so that the temperature on Mars increases. As the temperature increases, CO2 will sublime from the polar caps, adding to the amount of greenhouse gases in the atmosphere.
Step#5: Start transporting photosynthetic bacteria from the Earth to Mars once the temperature near the equator increases above the melting point of water. The bacteria will convert CO2 and H2O into more bacteria and oxygen.
Step#6: Introduce more complex life forms to Mars as the oxygen level increases in the atmosphere and as an ozone layer forms.
Step#7: Wait for photosynthetic life forms to create enough of an atmosphere such humans can live on Mars without fear of a rip in space-suit, i.e. you’d wear a thin space suit, but you could survive for an hour until you go back to camp to get a new space suit if there was a problem with the suit.

 It would take hundreds of years to develop a full atmosphere, so this is why we need to start working on this problem now. Before discussing the steps involved in growing life on other planets, I’ll first discuss how we lower the cost of accessing space.



Step#1: Design a propulsion system that can deliver material to the Moon and Mars as cheaply as possible.
To do this, one would have to design and fabricate a multi-stage aero-rocket propulsion system. The example below is actually a five stage reusable propulsion system that could significantly lower the cost of accessing space.
1. Use electromagnetic propulsion (like a bullet train) in order to get the aero-rocket to speed at which lift begins. Using a gas turbine, the aero-rocket would then lifts off from the electromagnetic drive system and starting gaining altitude and speed.
2. Carry liquid hydrocarbon fuel onboard so that the gas turbine gets you to a few thousand feet of altitude and a speed of roughly Mach 1. The aero-rocket might look like SpaceShip Two by Virgin Galactic. There would be gas turbines on each side of the aircraft. In the middle would be the spacecraft that detaches from the aircraft once the speed reaches just below Mach 1. The aircraft would glide down back to Earth for reuse.
3. The spacecraft that detaches is actually still a multi-stage propulsion system. First, a scramjet will get you to roughly Mach 5 and to an altitude at which the scramjet no longer works. At this point, the scramjet part of the spacecraft separates from the rocket part of the spacecraft, and the scramjet part of the system would glide down back to Earth for reuse.
4. The remaining rocket part of the spacecraft is carrying solid hydrogen and oxygen in order for the system to reach low earth orbital (LEO) velocity. At this point, the remaining part of the spacecraft separates from the rocket part of the spacecraft. The rocket part of the system would fire backwards to slow down, and then glide down back to Earth for reuse.
5. The last propulsion system is a plasma thruster (such as a Hall thruster, a MPD thruster, or a new advanced 4-grid ion thruster) to get the system out of Earth's orbit, to travel to the Moon / Mars and then to help the system to descend down to the Moon or Mars (since energy is required to slow the spacecraft so that it can land on the surface.) Once the spacecraft lands on Mars with the cargo, it stays there. It does not attempt to return back to Earth.

Notice that there are no humans on this 5-stage aero-rocket propulsion system. The only way to keep down the cost of space access is to make sure that there are no humans on-board the propulsion system (as was the case for the Space Shuttle.) {By the way, the Space Shuttle was a horribly expensive way to lift satellites into orbit. Let’s focus on robotic missions to Mars and the Moon before we even think about developing another space shuttle capable of transporting humans to the Moon or Mars.}

So, to reiterate: To do this on the cheap, one could first start with the SpaceShip Two design, and make the needed modifications for bullets 1-5 listed above. There is virtually no cheaper way to transport cargo from the Earth to the Moon/Mars than in the way listed above. And what’s great is that all of the technologies I’ve mentioned above are already developed or are currently being developed. While scramjet technology is relatively new, NASA has tested scramjet technology successfully. Hall thrusters and ion thrusters have been tested successfully on multiple satellites.


Step#2: Send over materials to initiate the growth of self-replicating solar auxons, and then let the solar robots start reproducing.

The cargo of these multi-propulsion spacecrafts could be micro-satellites, but for the purposes of this post, the main cargo of these multi-propulsion spacecrafts would be the starting materials in order to grow solar auxons on the Moon or Mars. So what materials do you need in order to start a solar auxon on its way to building more of themselves?
1)      Battery – without a battery or some equivalent electrical energy storage device, there would be no way to store the energy generated, which would be consumed by the robot factory.  [1-2 shipment]
2)      Solar cells – without the first solar cells, there would be no way to generate the electricity required to make the new equipment. (Though, it should be noted that a small nuclear -thermionic power generator could also be used to initiate self-replication of the solar auxons.)  [2-3 shipments]
3)      Initial computer hardware – the initial equipment to store the blueprints for the robots and factories must be transported from the Earth to the Moon or Mars.  [0 shipments…ship with other cargo]
4)      Initial replication factory – the initial replication factory must be transported as well as the equipment that powers the factory. This factory must be fairly small in order for it to be carried on-board the spacecraft described above. This factory would probably have to be shipped in multiple parts that can connect together without human involvement. Each part of the factory would probably have to be no larger than a small bookcase. This requires the design of a miniature factory.  And this means that the first solar auxons would be the size of shoe boxes. (Luckily, once these solar auxons start growing at exponential rates, they can start generating and storing GigaWatts of electricity.)  [5-7 shipments]

So, to initiate this process of solar self-replication, there would have to be roughly 8-12 shipments. If the destination is the Moon, then this could be done rather quickly, perhaps only a few years. If, on the other hand, the destination is Mars, then this could take a while because cheap access to Mars only comes along every roughly 26 months because orbital periods of the planets. If there were two launch vehicles each launching every 26 months, then it would take on the order of a decade to move over all the equipment required to initiate the production of new solar cells on Mars.

It should be noted that both the Moon and Mars present unique challenges for self-replicating solar robots. Both places have the problem that meteorites will damage the solar panels. This can be solved by making sure that the solar cells on each robots aren’t completely connected in series.  For the Moon, another difficulty is that a lunar day is roughly 30 days. This means that there will be times of intense building of new solar cells when the sun is shining, and then days of down time when the sun is not shining. A Japanese firm wants to solve this problem by encircling the Moon with a ring of solar cells, a Lunar Ring.

For Mars, a major difficulty is the dust storms that can blanket the planet. The self-replicating solar robots will need to be designed with a mechanism for mechanically cleaning off the dust. Most likely, this means that each solar collector will require a wiper blade, but this will add to the already complicated task of designing a self-replicating robot. Since the Martian day (24.5 hr) is roughly the same length as an Earth day, the factories that produce new solar cells will not have to hibernate as was the case on the Moon. At night, the solar factory can operate on battery until sun comes out again on Mars.

For those of you who are interested, the steel required for the robots would be created using hydrogen generated from running a fuel cell backwards or from graphite created by heating carbon dioxide in a plasma.

Fe2O3 + 3 H2(g) <—> 2 Fe + 3 H2O(g)
Fe2O3 + 3C(s)   <—> 2 Fe + 3 CO(g)

The silicon and aluminum required for the robots would be created using graphite and a heat source, such as a plasma torch.

SiO2+2 C <—> Si + 2 CO(g)                 Al2O3 + 3C(s)   <—> 2 Al + 3 CO(g)

The solar auxons must have the blueprints for reproducing the factory, the batteries, the hardware, and the blueprints themselves. Klaus Lackner has estimated the growth rate of solar replicating auxons such that the time to double population of solar cells is on the order of a few months. This means that it will only take roughly a decade in order to generate GigaWatts of electricity.

Luckily, the materials on the Moon and Mars are very similar to the materials found on Earth, so we can practice building solar self-replicating robots here on Earth before we attempt to build self-replicating solar robots on other planets. There are already projects that are attempting to build self-replicating solar cells, such as the Solar Sahara Breeder Project. Although, it should be noted that in this project there will be humans-in-the-loop. What we need is a joint collaboration between NASA and DOE/NREL to build truly autonomous self-replicating solar robots. There’s plenty of land available in California, Arizona, New Mexico and Texas were we could practice building self-replicating solar cells.

For the Moon, it’s unlikely that we can terraform it so that human life can live there without space suits. But Mars is capable of being terraformed back into how it existed billions of years ago when there was an atmosphere and liquid water.


Step#3: Send over a working lab to generate CFCs and other greenhouse gases from materials on the surface of Mars. The lab will require electricity generated by the solar auxons.

In order to transform Mars into a livable planet, we have to increase the temperature and melt the ice so that there is liquid water. To do this cheaply, we will have to emit greenhouse gases into the atmosphere. Adding  greenhouse gases to the atmosphere will over time increase the average temperature of Mars from roughly -55oC at the equator to over 0oC. Below is a table from Zubrin’s The Case for Mars. The table lists the amount of power required to chemically generate CFCs as a function of the amount of required Induced Heating.

Induced Heating         CFC Pressure              CFC Production          Power
[K]                               [microbar]                    [ton/hr]                        (MWe)
5                                    0.012                             260                              1,310
10                                  0.04                              880                               4,490
20                                  0.11                            2,410                            12,070
30                                  0.22                            4,830                            24,150
40                                  0.39                            8,587                            42,933

Since we require over 40 K of induced heating, this means that we will require over 43 GWs of electricity. While this is a lot of power, it will only take a few decades for the solar self-replicating robots to get to the point where they are continuously generating this much power.

Using a value for the climate-averaged solar flux on Mars of 110 Watts per m2 of surface area and assuming a solar energy-to-electricity conversion factor of 10%, then the area of solar cells required to generate 100 GWs of electricity is approximately 100 km by 100 km. This is a large area, but it’s really small compared with the total surface area of Mars. Assuming that we initially have 1 m by 1 m of solar cells and assuming the solar auxons can double in population in 4 months, then it will only take 11 years for the solar cells to grow from 1m by 1 m to 100 km by 100 km. If the doubling time is instead 6 months, then it will take roughly 16 years before the solar cells are generating enough electricity to produce enough CFCs to change Mar’s climate by ~ 50 degrees Celsius. This is not a particularly long time to wait.


Step#4: Emit the newly formed greenhouse gases so that the temperature on Mars increases. As the temperature increases, CO2 will sublime from the polar caps, adding to the amount of greenhouse gases.

One question is: what type of CFCs should we make to warm up the planet? There are a lot of options between then various single carbon CFCs. We would like to choose a CFC rather than a hydrocarbon like methane or ethane because methane and ethane will combust in the presence of oxygen. Methane would be the easiest greenhouse gas to produce because we have already developed the technology to convert carbon dioxide and water into methane and oxygen by running a fuel cell backwards. [Note that the solar robots will be generating oxygen as a by-product of the iron oxide to iron, alumina to aluminum, and silica to silicon processes required to make more solar cells. And eventually, the photosynthetic bacteria will be generating oxygen as a byproduct.] So this means that, while methane would be an easy GHG to produce, we will have to generate CFCs like CF2Cl2 that are stable in an oxygen rich environment.

Once the CFC pressure reaches 0.3 microbars, then there will be roughly enough warming so that the frozen CO2 on the polar caps will sublime into CO2 gas. This means that once we start the process of warming Mars, there will be a positive feedback mechanism so that we don’t have to continuously be pumping more and more CFCs into the atmosphere. It would be preferable to have CO2 rather than CFCs in the Martian atmosphere because CO2 is a known fuel for photosynthetic bacteria.

Step#5: Start transporting photosynthetic bacteria from the Earth to Mars once the temperature near the equator increases above the melting point of water. The bacteria will convert CO2 and H2O into more bacteria and oxygen.

Once we have liquid water on Mars, we can start sending over bacteria from Earth. Experiments suggests that bacteria from Earth could survive and grow on Mars. The bacteria would be kept in hibernation during the trip from the Earth to Mars. Once the bacteria reach Mars, it would likely only take a few decades to a century for photosynthetic bacteria to start populating the planet. The first bacteria will likely be anaerobic bacteria similar to the first bacteria living on earth. In order to ensure that the bacteria replicate, there might need to be a chemical factory shipped from the Earth to Mars that can create amino acids from elements existing on Mars, such as carbon dioxide, water, nitrate, and phosphate. This factory would be powered by the solar cells already on the planet. Eventually, though, the bacteria will have to evolve means of creating amino acids and other cell materials by themselves using only the material available on Mars. Mars has all the required elements for life, but the bacteria will have to adapt to the different conditions of Mars.


Step#6: Introduce more complex life forms to Mars as the oxygen level increases in the atmosphere and as an ozone layer forms.

The bacteria will generate oxygen over time, and this will eventually create an ozone layer in the upper atmosphere. This will be crucial for limiting the amount of UV radiation that reaches the surface of the planet. Since Mars does not have an active magnetic field to deflect charged radiation from the surface, it’s important to block as much UV radiation as possible. As the oxygen level increases, we can start transporting over algae and other complex photosynthetic life forms. Zubrin expects that "The first 100 mbar [of atmosphere] can be [generated] in about 25 years. 200 mbar can be reached in 100 years." So, what we’re are talking about is a process of building up Mar’s atmosphere that could take a few centuries. This means that we should get started now so that people can start voluntarily traveling there once we start reaching limits to growth here on Earth.


Step#7: Wait for photosynthetic life forms to create enough of an atmosphere such humans can live on Mars without fear of a rip in space-suit, i.e. you'd wear a suit, but you could survive for an hour until you go back to camp to get a new space suit if there was a problem.

The ozone layer will be crucial for eventually allowing humans to travel freely on the planet. Also, it will be important to build up enough oxygen so that humans could survive on the planet for short amounts of time even if there is a rip in the space suit. Rather than go into the details of what it would be like to live on Mars, I’m including some links to articles on what it would take for humans to survive on Mars.
http://en.wikipedia.org/wiki/Colonizing_Mars
http://www.aleph.se/Trans/Tech/Space/mars.html
http://www.redcolony.com/features.php?name=whycolonizemars



So, we are left the problem that Robert Zibrin faces when he advocates for colonizing Mars…how do we fund this? My answer is that it must be the major world governments that fund such a project. The reason why we need to colonize Mars is that we need to grow life throughout the universe. Mars is the first step of a continuous process of growing life on other planets. The benefits of colonizing Mars do not fall on any one person, so no one person should have to fund this project by him or herself. This is what governments should be doing…funding those projects that are required for growing life, but which no one person or group is willing to fund because that person or group does not see the benefits.

Let me know what you think we can do to help convince the major world governments to start funding a project (similar to the one listed above) in which we slowly terraform Mars (i.e. in which we build self-replicating solar auxons on Mars to generate the electricity required to create the CFCs required to warm the planet such that water melts, allowing bacteria to thrive and generate the oxygen required for more complex life forms like humans.)

4 comments:

  1. I certainly believe we'll get to Mars within the next 30 years though I doubt many of us around today will ever see the planet colonized. I'm sure it will happen and would like to see it happen but that's in a distant future I'll never be part of.

    http://solarpowerenergy1.com/blog/

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  2. Physics is most fundamental of all sciences and provides other branches of science, basic principles and fundamental laws. The study of physics involves investigating such things as the laws of motion, structure of space and time, the nature and type of force that hold different materials together, the interaction between different particles.

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  3. The question is: what are our priorities for NASA? Here's a list of the things that NASA has done, could do, or should do, in the order of my own opinion on what NASA's priorities should be.

    1) Launch equipment into space to look for life on other planets
    2) Send self-replicating solar robots to the Moon and Mars (after developing the technology here on Earth)
    3) Launch equipment into space to study Big Bang / Dark Matter / other interesting physics
    4) Launch spacecraft to study other planets and their moons (such the the JUpiter ICy moon Explorer...JUICE)
    5) Space Weather, i.e. watching the Sun so that we have a warning on when there are coronal mass ejections that could damage electronic equipment (NASA currently does this along with the Air Force Research Labs and private companies)
    5) Manned missions to the Moon / Mars (this should be a low priority until we have self-replicating solar robots already well established on the Moon / Mars)

    Feel free to rank the NASA missions according to your own opinion on NASA's priorities. I appreciate your feedback.

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  4. I think it is more likely that self replicating intelligent robots will colonize first the Moon and then Mars. It is very anthropomorphic to think humans will be better than machines.

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