Mars Crater Village

[Ionmars]

To fill the interlude between now and first Starship orbital launch, we can update our speculations about the first stages of Mars colonization. This thread  will address (1) how we could exploit natural features of the surface (craters), and (2) how we could employ Starship sections in upright position to quickly set up an initial village in a crater. I will post a series of sketches to illustrate the proposed process.

Background thread: Modular Mars
https://forum.nasaspaceflight.com/index.php?topic=51406.0

[Ionmars]

Craters pockmark Mars surface in a wide variety of shapes and sizes, from kilometers in diameter to just a few centimeters. Early pioneers could exploit some of the smaller craters in several ways , two of which are (a) landing and launch sites and (b) a small initial village. The example crater shown below is circumscribed by a circular ridge, caused by the impact of a meteor in the  distant past. Note that sunlight strikes directly on the north (right) slope suggesting a good location for solar panels. A shadow falls over the south (left) slope, suggesting a good place to locate tanks to store cryogenic liquids.

[Ionmars]

A Starship launch from Mars surface will generate a blast wave that hurls rocks and sand at supersonic speeds. It could potentially damage unprotected equipment, structures, or other landed spaceships in the vicinity. To protect these resources Mars settlers will need to build walls around the launch site and possibly around nearby structures.  They will also want to locate structures a safe distance from the launch blast. However, if the launch pad were located inside a crater, its ridge could serve as a natural barrier against flying debris. This approach would avoid the time and expense of building a wall around the launch site. A second advantage is that it would contain the blast debris within a limited circumference, thus allowing  structures be located closer to the launch pad (but not in the same crater).

When SpaceX planners look for a settlement site, they might note whether there are craters suitable for a launch pad. Useful criteria might include diameter and depth of the depression. A potential launch site should be deep enough to contain or deflect most flying debris, but shallow enough to allow mobile equipment to navigate into and out of the crater. Larger craters may have steep canyon walls, which should be avoided. A desirable shape may have at least one side with a modest slope leading up to the rim, such as the example crater shown below in cross section. This drawing is from Reddit, originally posted by Bart Caldwell (Twitter@Neopork85) 06/11/2020.

[Ionmars]

A minimum size crater for a launch site might look like the first image below. This one  is about 80 m in diameter and abut 10 m deep, about the same depth as an SS launch mount is high. At launch much of the flying detritus would be caught inside the crater. Some debris is likely to ricochet out of the basin, but at reduced velocity. The gentle slope up the sides should allow fairly easy transit in and out of the crater.

[Ionmars]

A larger but still small crater (by Mars standards) might be as wide as 250 m, as suggested in the sketch below.  A depth of 40 m would allow more blast debris to be caught within the crater and a gentle slope would enable easy access, but with a longer pathway from rim to crater bottom.

This sketch suggests cutting a road through the rim to expedite movement of equipment.  However,  initial use of the crater might just mean clearing large rocks off a 10 m wide path up the slope and employing a sled to slide equipment and ships up and down the embankment.

[Ionmars]

The second concept addressed in this update is to employ standard Starships that have two main sections that can be separated. The sketch below shows a standard SS crew section composed of a nosecone and a barrel subcomponent. The second (tank)  section is composed of CH4 and LOX tanks. When landed on Mars, crew would presumably cut around the circumference of the inter-sectional fairing space without cutting into propellant tanks or the pressurized crew section.  This would result in two pressurized units, one crew section that is already designed for human occupancy  and a second (tank) section that could be outfitted with a life support system (LSS) and occupied by humans. The top crew section of SS would be employed on Mars as sleeping/privacy quarters and the second (tank) section would be employed as a workplace.

In this scenario, village personnel are engineers and technicians that service SS launch operations in a nearby crater. Workplaces could include Starship repair and parts recycling, a repair shop for large surface equipment (cranes, trucks and cars), or an LSS maintenance shop. All work could take place inside human-rated vessels with a  shirt-sleeve environment .

[Ionmars]

Before SS sections can be employed as livable units, they must be prepared for use on Mars. Raptor engines would be removed and set aside for reuse or return to Earth. Flaps, external plumbing, and COPVs should be removed. Any thrusters, plumbing, or other openings that could compromise the integrity of a pressurized vessel must be solidly closed off. Some heat shield tiles may be removed if they would interfere with equipment to be attached to the surface (explained later).

In this approach, SS internal equipment and structures, such as Inter-tank domes and transfer tubes, would be left intact to simplify and expedite reuse of these sections on Mars. Only the lower (LOX) tank would be converted to human occupancy. The CH4 (upper) tank would be used to store water that is mined from Mars subsurface and warmed to liquid state. The water storage tank  would serve as intermediate  protection from galactic cosmic radiation (GCR) for a workplace in the lower tank, as well as for water storage for human usage. Water will also be utilized in a Sabatier reactor to produce CH4 rocket propellant.  Over time, regolith will be dug up and placed atop living units so that  radiation protective layers will accumulate until all living units are be covered by a 3m or more regolith shield.

Separating sections and converting LOX tanks to workplaces will (approximately) double the human living volume in an initial Mars village, as compared to only using SS crew sections as living units.

[Ionmars]

The principal reason for choosing a crater for the site of an initial village would be the additional protection from blast debris. This is especially desirable if the village is located near a launch or landing crater. In addition to launching of Starships, landing ships may also require additional protection for structures and equipment. Each ship could have its own landing site inside a crater, but It seems unlikely that enough suitable craters could be found in any one vicinity to accommodate several dozen or more ships arriving within a short window. Additional flying debris due to landings outside of craters may require extra protection that is provided by locating a settlement inside a crater.

In the following example, SpaceX planners choose a crater near a launch site for an initial Mars village. This crew village would provide technical support for launches, so proximity between launch site and village is highly desirable, much like the relationship between launch site and production area at Starbase, Texas.  The village crater, at 400m diameter, is larger than the launch crater and comfortably accommodates 26 human-rated units derived from 13 Starships.

[Ionmars]

Before Starship crew and tank sections can be installed, the crater will require some initial preparation. First to arrive would be components of a crane that could be lowered into the crater and assembled there. Alternatively, a whole crane could be lowered if deemed feasible. Next would be backhoes, front end loaders or graders needed to prepare flat compressed ground in the center of the crater where initial units would be set up. A slide down one side of the crater would be prepared for better movement of construction equipment and crew in and out. Future development of the crater would occur simultaneously with construction of the village. Eventually there would be an improved road into the crater and a series of ledges along the slopes where crew sections, tank sections, solar panels, and storage tanks could be set up.

After the first few tanks have been stripped down for use in a settlement, they would be transported to the crater site. The sketch below shows the first tank sections  sliding down the side of the crater using a crane on the rim and a crane in the crater below.

[Ionmars]

Crew would set up the first living unit in the center of the crater using the same crane already employed to prepare the ground. The photo below is a reminder that a large crane (LR 11000) is employed at Starbase to lift and place a whole starship onto a launch mount. The SS sections in this post are much smaller and lighter than a whole ship. Therefore, a much smaller and lighter crane can be employed, which would be much easier to dismantle on Earth and ship to Mars.

The first (tank) section of the village would hang from a crane cable while it is set up. First step would be to immobilize the bottom of the tank in position by shoving mars mud around the lowest point of the aft dome and allowing it to solidify, quickly followed by covering the solid mud with a thin layer of sandy regolith. Then coarse regolith, consisting of rough sand and small rocks, would continue to be piled up around the bottom of the tank to stabilize it in place. Before the cable is removed, four guy-lines would be installed to maintain the section in vertical position during further work.

More information about the use of mars mud can be found here:
Building with mars mud
https://forum.nasaspaceflight.com/index.php?topic=51932.0

[Ionmars]

A second tank would be connected to the first one by means of an inter-tank connector. It would consist of a short square tube with a door frame installed within it, as shown in the sketch below. Its outer edges would be curved to match the curves of two SS tank sections, to which it would be attached. 

To install the connector onto tank section #1, space-suited crew would cut an entry  hole in the side of the tank from the outside (because I presume there will be no other entry into the tank). The hole would be located where the connector is to be attached and then they would enter into the tank through the hole. A crane would hold the connector over the hole and crew  would weld it to the tank wall from the inside. Then the crane would hold tank section #2 against the connector while crew welded the second tank to the connector. They would cut a second hole in the second tank and polish up cut edges to complete the connection. Now two tank sections would be combined into one unit and pressurized as such. Two floors inside the two tank sections should meet at the connector at the same height, so personnel could walk between tanks on the same floor level. Optionally, an airtight door could  be installed in the door frame.

The village could incorporate  a centralized facility to serve the whole community, such as a water treatment plant, a wastewater treatment facility, or a centralized life support (air treatment and recycling) facility. This would entail distribution pipes or ducts that pass between units and would require special duct or pipe joints at inter-tank connectors. 

[Ionmars]

*
In this thread I borrowed the concept of employing a vertical Starship as an intersection between pressurized units. As far as I know, TheRadicalModerate first posted this idea in the “Modular Mars” thread:

Re: Modular Mars
« Reply #206 on: 07/20/2020 05:56 am »
https://forum.nasaspaceflight.com/index.php?topic=51406.msg2108965#msg2108965

The original idea was to employ a vertical crew section as an intersection of four hallways comprised of Starship sections lying in horizontal position. In the present update there are no hallways between units; units in vertical position are joined directly with one another, and the density of living in the proposed village is greatly increased over the previous concept.

“The best part is no part.” 

[Ionmars]

The sketch below presents a “quin-tanks” arrangement with the first tank section in the center and four other tank sections joined directly to it. Tanks are joined using inter-tank connectors, as shown. This group of tank sections could be the nucleus of an initial crater village that expands over several synods  to fill up the crater.

Note 1: A connector (with a leak-proof door installed) attached to just one tank could serve as a portal to the outside, as suggested in the sketch.

[Ionmars]

Sizes of inter-tank connectors may vary according to how they will be used. The sketch below shows a small connector used for crew and small equipment to enter the village through a pressure chamber and to pass between units. To enter the village from outdoors involves the pressure chamber  equipment to operate the chamber, including press and depress pumps, spacesuit and equipment cleaning equipment, and a storage area for cleaned spacesuits (not shown).


A large connector could be employed for a repair shop for large equipment, such as cranes, trucks, and ship components. A large pressure chamber and associated equipment dominates the shop area, so a second workplace unit may be attached to the first one. A suitably large connector joins the two units into one shop volume, so a large crane could pass through depress and repress, then proceed directly through the entrance workplaceto the second shop area. Crew would work in both areas in a shirtsleeve environment unless going through the pressure chamber.

[Ionmars]

The village would grow outward by sequentially attaching new tank and crew sections to the original quin-tanks. Eventually the original cleared and flattened area in the center of the crater would be used up and new tanks would be installed up the side slopes of the crater. This growth should be planned in advance by constructing ledges on the slopes.

When regolith is cut away from the side slope to create a ledge, debris would tumble down the slope. If any structures were located directly downslope they could be damaged, so the first ledge should be built on the highest feasible location inside the crater. The next level should be built just below the first one, and so on, to allow debris ti fall sown-slope without hitting other ledges or installed structures. Ledges should also be constructed for solar panels to be installed on the north side of the crater (for best sun exposure). Loose sand and small rock debris should be piled over the already installed living units so as to build up radiation protection layers.

[Ionmars]

Inter-tank connectors can be applied to construction on a slope. As shown in the sketch, a connector would be installed at the lowest floor level of the first tank. The second tank section would be higher than the first one, so the connector would attach onto the second tank at a higher level. It would be necessary to install a stairway in the first section such that a person in the second section would step down stairs into the first section.

[Ionmars]

The sketch below shows an initial Mars village inside a crater. This example settlement contains 13 crew sections used as sleeping quarters and 13 tank sections employed as workplaces. If  these crew quarters could accommodate 20 to 40 persons, then the population of the village could be 260 to 520 people. If the payload compartments of crew sections were converted to  additional sleeping facilities, then a larger group could be housed.

Note that the north (sunlit) side of the crater could be set up as a solar panel field. Presumably, ledges would be cut into the side of the crater for this purpose, but the ledges would be more narrow than ledges for tank sections. They only need to be wide enough to allow panels to sit upright facing the sun and for maintenance personnel or robots to pass in front of them.

The south (shadow) side of the crater contains special ledges that support tank sections that are used as … storage tanks. Some cryogens, such as liquid oxygen, liquid nitrogen, and liquid air (mixture of O2, N2 and Ar), will be required from time to time in workplaces or crew quarters. Storing cryogenic liquids in the shade would help to prevent warming to sublimation point during daylight hours.

End of initial posts on this thread by the author.

[rakaydos]

Given the other criteria for a landing site, how many good crater landing sites also have nearby glacial pack and good angles for solar emplacement?

[Ionmars]

Given the other criteria for a landing site, how many good crater landing sites also have nearby glacial pack and good angles for solar emplacement?

Good question. I expect it can be answered by a detailed scrutiny of the large library of satellite photography of Mars surface.

[edzieba]

Lava tubes would be more attractive for habitation purposes (radiation protection, thermal stability, opportunity for large pressurised volumes with minimal construction, possible water ice reservoirs). Pit craters associated with lava tubes could be used as natural blast pits, or impact craters near by to a lava tube.
With the assumption of heavy machinery available (used for moving and manipulating disassembled Starships and piling up surface material for supports) that same machinery could be applied to create blast pits - or direction blast barriers - from surface material, obviating the need to locate near natural craters.