Posted on June 27, 2022
Some of my friends, supporters like me of the exploration of Mars by manned flights, do not share my opinion on the indispensable and almost inevitable character of a permanent and autonomous establishment on the red planet (at least as much as it will be technically possible). I answer them.
There are several reasons for wanting to send humans to Mars. The first, or rather the most immediate, is its scientific exploration. It is clear that with the time lag resulting from the finiteness of the speed of light, robotic exploration is difficult since the distance of 56 to 400 million km between the two planets coupled with the 300,000 km/s of the light, imposes a minimum time of 5 to 45 minutes between the sending of an order and the return of information to Earth giving an account of its consequences.
As a result, no action can be taken live on Mars, unlike what can be done on the Moon. Since we can almost send men to Mars today and especially since we should be able to do so tomorrow, in particular thanks to Elon Musk’s Starship, a human presence would therefore represent an advantage that would be difficult to contest compared to the present situation, in less in this area.
The difficulties of settling on Mars
But if we go to Mars, I am convinced that we will have more interest in settling there and here is why.
1) The first trip will be risky and in any case dangerous because there will be no welcoming committee on arrival. This will pose a problem in particular for helping passengers to carry out the most basic tasks in the context of newfound gravity. A team remaining after this first will be more than welcome so that the arrival of the second mission takes place in better conditions.
2) Mission “n” will have to leave Mars before mission “n+1” gets there. Indeed, departures to Mars from Earth can only take place within a window of one month every 26 months, the journey lasts 8 to 9 months in an ideal ratio mass transported/energy expended (transfer orbit of Hohmann) but it can be reduced to 6 months by consuming more energy and transporting less mass, while maintaining a free-return trajectory.
Then the stay on Mars cannot last less than 18 months (unless you leave after only two or three weeks but at the cost of a stay in space much longer than on the outward journey, of a perilous passage through the environment of Venus and a higher, dangerous speed when approaching the Earth). And again the return to Earth will take six months. We will therefore have a mission of 6 + 18 + 6 months = 30 months. Clearly the “n” mission will leave Mars 24 months after its launch but above all the “n+1” mission will only be able to arrive on Mars after 32 months (26 + 6). So, do not dream, there will be a significant time gap between the departure from Mars and the arrival of the next mission on Mars. This implies, in addition to the absence of the reception committee already mentioned, the absence of a presence to maintain the equipment left behind (and the Martian environmental conditions are very harsh, according to terrestrial criteria).
3) Any import from Earth will be impossible between two launch windows. It will therefore be necessary to have stocks but above all to do the maximum with local resources to produce the resources that we will need. In fact, in addition to the constraint of windows, and the need for certain products not to be too old to be consumed, the transport of mass and volume from Earth will always pose a problem because the payload capacity of our rockets does not is not unlimited and never will be.
I remind you that the Starship will only be able to transport one hundred tons to the surface of Mars; it is both a lot compared to today and very little compared to the needs of a community settled there. It will therefore be necessary to develop ISRU (In Situ Resources Utilization) as much as possible, including ISPP (In Situ Propellent Production), two principles highlighted by Robert Zubrin in the early 1990s and then taken up by NASA which remain essential.
Establish a colony
The ISRU will be used to produce from Martian materials, the maximum number of semi-finished products that we will need, such as metal beams and beams, glass plates, silicon plate (for solar panels) but also plastic materials, fabrics, food, powders for 3D printers (various objects and spare parts) and, as far as possible, the machines to obtain these products or at least the most massive elements that will be needed to frame, support or protect them .
The ISPP will be the production from the carbon dioxide of the Martian atmosphere, and the storage, of methane and oxygen which will be the propellants used by the interplanetary rockets (the return to Earth!) or planetary ones (to go anywhere on Mars). Methane burns very well in oxygen (good Isp) and the production of the two gases uses a proven and easy-to-implement technique (Sabatier reaction) with a little hydrogen (one part for eighteen) that the found in Martian water ice (electrolysis).
4) But it will not only be the products that we cannot bring from Earth when we want to, it will also be the people. Indeed it will be necessary to control the robots, to operate the machines, to monitor the cultures (algae, fish, plants), to organize the constructions, to control their viability and their healthiness. Besides, the people living on Mars will obviously be the institution’s most valuable asset.
To keep them in good health, it will be necessary not only to have medicines and various medical instruments but also doctors in all possible specialties. It will be first of all surgeons because it is still delicate to entrust one’s body to machines not controlled directly by man, but also nurses to apply the directives of doctors examining from Earth the various biological data collected on the spot.
Finally, scientists coming to Mars will need all kinds of technical services, including in particular those of telecommunications specialists or computer scientists. And “everyone” will need “do-it-yourselfers”, i.e. engineers/mechanics/chemists capable of solving an apparently insoluble problem that we will not have foreseen, because they will have the intellectual and manual capacities to do so.
Finally, it will take services to take care of all these people: conditioners for food products (pasteurization, appertization, freezing, inventory management), cooks-restaurateurs, administrators, financial advisers, insurers, people capable of to take care of the education of children…or of the deceased.
In fact, we had calculated with Richard Heidmann (in a study published in 2018 in the Journal of the British Interplanetary Society), that an operational Martian base should have some 1000 people (including about 500 visitors renewed at each cycle and income providers for the colony). This is probably what should be considered to shoot in acceptable security conditions while generating sufficient profitability to continue.
All these people necessary for the maintenance of men and equipment, that is to say the operation of the base, will not be able to come at the same time as the customers and leave with them. This would not be rational given what was said above (maintenance of equipment and reception of new arrivals) and would require too many ships which could not transport anything else (the search for autonomy does not mean that we will reach it immediately nor that exchanges will not take place).
5) A final factor to take into consideration, related to distance, space and Mars, is the fact that the men who will go to Mars will have to undergo the constraints of a long journey (in any case several months) , a non-negligible exposure to space radiation (we can bear the dose without any problem for a single trip or two, but certainly not for five or six), and the consequences of becoming accustomed to a gravity much weaker than on Earth.
There will therefore be people who are specialists in Martian sciences, economically interested in living on Mars because they will have their activity and their social ties there (the baker!) or simply in love with Mars, who, after a first stay, decide to come back and to stay there. These people will want maximum comfort and convenience and they will strive, in their own interest, to have all the necessary facilities.
Mars will be neither the International Space Station from which it is possible to return in less than 30 hours, nor Antarctica which, of course, can be isolated but whose isolation will only last a few weeks or, at worst, a few small winter months. It is for this isolation that naturally more and more autonomy will be desirable or even essential for human settlement on Mars.
Reading: Robert Zubrin, The Case for Marsat Free Press, last edition, 2011 (Robert Zubrin, creator of the Mars Society in the United States, marssociety.org)
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