Postcards from Mars

Where in a home remodel you might make decisions based on aesthetics, energy efficiency, historic context, quality, an HOA, or price, in building a Mars habitat analog you are asking a different set of questions:

• What will maintain a hermetic seal?
• What will not invoke condensation given the temperature extremes in the high desert winters of southern Arizona?
• Does this immediately give off heavy VOCs? Will it subside over time? Stabilize completely?
• How will we maintain the pressure vessel when connecting these two structures?
• Given that our funds are limited, what off-the-shelf products will get us as close as possible to what might actually be used in a real, other-world habitat?
• What would NASA say to this selection of construction material, sealant, or paint?
• What will hold up to the variety of visiting teams?

While the 40 foot shipping container came to us fully insulated (refrigerated) and essentially sealed (save a few openings at the front which will be easy to fill), we searched for more than three months to locate an insulated 20 foot container, to no avail. The 40 foot unit will be the living space for the crew while the 20 foot will serve as a corridor from the airlock to the crew quarters and Test Module. To facilitate a reduced thermal load and associated electrical consumption (with our intent to eventually go off-grid), we are manually insulating the 20 foot container, from the floor to walls to ceiling.

Starting from the ground up, we are designing a system by which the floor is insulated using standard building materials (plywood, foam board, adhesives) that will remain outside (below) the hermetic seal such that the inhabitants will not be breathing the space that contains the resins and glues associated with these products.

Our first (bottom) layer is a tight steel mesh to keep the rodents from chewing their way in (we hope that pack rats do not yet inhabit Mars). Then a layer of plywood to provide support for the insulating foam board, the foam board, and then another layer of plywood to protect the foam from the top and to provide a solid surface for the fifth and final layer—sheets of carbon steel.

Continued with Installing the steel floor …

One year ago today Trent and Kai stood in front of the historic Test Module at Biosphere 2 and while smiling for the camera thought, “What the hell are we getting ourselves into?!”

It feels like a lifetime ago, far more than just nine months in one year (the summer spent in cooler climes). We have dug, cut, scraped, cleaned, welded, primed, wired, and assembled as only these photos essays can provide detail.

It’s been an incredible journey, a tremendous learning process, and we’re still going strong!

We have been waiting for this moment for more than a year—the placement of the shipping containers to serve as the workshop and crew living quarters. The concrete footings were poured in early December, the doors for the 20 foot unit removed and the hatch plate installed just last week.

Mark Scheicher (Crane Operator), Frank Campa (Oiler/Rigger), and Steven Carnahan (Rigger) from Marco Crane arrived 20 minutes early at 7:10 am. I ran from the Casita where Trent, Colleen, and I live on campus to the Service gate to meet the crane and support truck that carries the weights used to counter-balance the crane. On-foot I ran ahead of the convoy from gate to SAM, a quarter mile downhill.

John, Kevin, and Jason were already on-site. Given the tight move between the old botanical gardens and restaurant the truck driver chose to back his rig to enable an easier departure. About thirty minutes transpired as the crane assembled itself, stabilization arms extended and set on large pads, leveling the crane before its operation, weights moved to key locations, load straps connected.

Mark, the crane operator asked if the containers were full.

I responded “No, they are empty.”

He laughed, “Oh! This will be easy!”

Easy? Glad I am not operating the crane or running rigging on the ground. One false move, one nudge left or right of center and the Test Module could be bent beyond repair, windows cracked, fingers smashed, or worse! This is why we hired the experts.

The 20 foot unit was lifted into place first. In coordination with Frank’s hand signals, Mark hovered it just above the four concrete pads, perfectly level. He then lowered it bit by bit until it skimmed just above the surface, providing some friction with the concrete but not nearly its full weight. I was able to maneuver the entire unit with one hand, placing it within an eighth of an inch of my desire location. I checked the placement with the tape measure, making certain the container was parallel to the west wall of the Test Module, then called it good. The operator allowed the full weight to rest on the footings and the straps were disconnected.

The 40 foot unit was a bit tricky due to its size and our realization that one of the concrete footings had been incorrectly placed, off by an inch. Once this was noticed, it made sense why we could not nail our center points as accurately as the 20′. No worries, the unit is parallel to the 20′ and perfectly supported on the oversized 18″ circular pads. To see the crane operator and crew in action is a testament to the technology and skill employed. While I can explain the physics of hydraulics, it does not reduce my appreciation for the ability to move thousands of pounds within a fraction of an inch of a desired location, or to reduce the apparent weight from something that would turn a human into a pancake to something that can be maneuvered with ease.

With the containers in place, SAM became something more than a refurbished building. Nearly one year to the date of our first day in this project, the dream of our analog was given new form.

The original Test Module (TM) was constructed in 1987 and operated into 1990 as a prototype for the much larger Biosphere 2. Where a single occupant of the 440 square foot TM shared an intimate space with the plants that recycled the air and water and produced all food, the 3.1 acre Biosphere was divided into five biomes, a technical understory, and living space for its eight occupants. SAM falls somewhere in between with the TM serving as the controlled environment (greenhouse) for food cultivars and plant growth experiments, two added shipping containers (20′ x 8′ and 40′ x 8′) to serve as the workshop, storage, kitchen, common area, sleeping compartments, and toilet-bathroom.

Kai Staats, Colleen Cooley, and Trent Tresch with assistance from Tim Mcmullen and Jason Deleeuw of the Biosphere 2 staff removed two of the original TM sealed windows and frames, then bolted in place a single 133.5″ x 66.5″ sheet of 3/16″ steel with a welded frame. This new construct was prepared by James Parker and his crew at the University of Arizona Facilities Metal Shop (Thank you!) and forms the passage between the Test Module and the 20 foot shipping container. The hatch itself will include a pressure fitting such that the TM can again maintain a hermetic seal independent of the Crew Quarters, or be run open for a fully pass-through airflow.

By design, the hatch is 40″ wide and 48″ inches tall, and will include a few steps up to either side. This is intended to serve three purposes: to provide a single, clean interface for the pressure sealed hatch, to maintain the integrity of the historic Test Module, and to provide a space-ship like interface between these two major components of the SAM construct.

On Tuesday, January 18, the two shipping containers will be placed on their concrete footings and the transition from restoration to construction will be well underway!

On December 8, 2021 we completed the concrete work required to place the shipping containers adjacent to the Test Module. They will serve as the crew quarters for SAM. Today Director of Research at SAM Kai Staats and Colleen Cooley, GSD Specialist removed the two doors from the 20′ shipping container. They then removed the silicone caulk (which remains fully flexible after 30+ years) and backer bead used to form the air-tight seal around the windows. This same system will be used to again seal the steel plate that will replace the two windows, and hold the hatch at the entry point to the Test Module from the 20′ shipping container.

As we have worked to simulate the interior light conditions of a habitat on Mars, covering the upward facing glass panels of the Test Module with optically opaque silicone elastomeric, and the horizontal window panes with 50% optical transmission film, it is important to understand how the light falls inside of this greenhouse space. While we will rely upon synthetic lights for most growing operations, the additional, natural light will affect grow patterns.

Tullio Dellaquila is a light specialist who was on-site working with John Adams at the Biosphere 2 ocean. He stopped by SAM to conduct a spectral analysis of the light, from four key positions:

a) Outside of SAM, unfiltered by glass or any overhead structure.
b) Inside SAM, through the mid-level, unfiltered glass.
c) Inside SAM, through the lower, filtered glass.
d) Inside SAM, in the shadow of the silicone covered, top glass panels.

The data is currently under review, and will be published at this entry, soon.

SAM volunteer Colleen Cooley and Kai Staats worked on the design of the portal between the Test Module and the Crew Quarters, determining how crew members will move between the two distinct section of the SAM habitat. While it was the original intent to cut down into the knee-wall of the Test Module to create a walk-through, it was determined that by instead keeping the hatch at a higher level, it could be contained entirely in the space defined by the current window frame which is being replaced by a single sheet of steel. As such, the hatch can be closed to return the Test Module to a fully pressurized, hermetic seal and operate as such with or without the adjacent crew quarters sealed. This gives SAM a greater degree of flexibility and maintains the integrity of the historic Test Module while giving visiting teams a true sense of moving from one module into the other much as one does in the International Space Station.

Heating and cooling the SAM Test Module (greenhouse) is paramount to the success of plant biology and food cultivar studies. Maintaining a relatively constant, controlled temperature and humidity is not easy in the context of the drastic changes in weather and conditions of the Arizona desert.

When the Test Module was first built, a separate room was required to produce hot or cold water which when pumped through a heat exchanger suspended from the interior space frame provided warm or cool air. That unit weighed a few thousand pounds and was removed piece by piece in the first few weeks of SAM effort, February 2021.

That system consumed massive amounts of electricity, likely more than 100 amps at full draw. The modern replacement, a mini-split heat pump, is far more energy efficient at just 15 amps maximum draw per condenser. What’s more, the interior air handler (sometimes referred to as the “head”) is not unlike that which could be used in an isolated, off-world habitat for it does not exchange air inside to out, rather, it recirculates air entirely internal to the controlled environment. Only the pressurized gas that exchanges the thermal energy from the condenser to the air handler moves through the wall, and in this case through a manifold that maintains the hermetic seal.

As the condenser at SAM does use a convective thermal exchange process (fan), it would not work as such on Mars for the atmosphere is too thin to conduct the heat away from the external unit. Instead, the condenser would pass the pressurized gas through a radiator likely composed of hair-like aluminum or copper filaments for maximum surface area and passive radiant thermal exchange.

The first unit was installed on June 26, 2021. This was operational for the 5-person, 4-hour test run. The second unit was installed on December 16, 2021 by the same team from AirQuest, based in Tucson, Arizona. Owner and president Aaron worked with Kai Staats for a few months prior to the first installation to calculate the required cooling and best placement of the units. As the software provided by the mini-split manufacturers does not anticipate an all glass construction at 24 feet tall, the upper reaches coated with a silicone elastomeric, a good bit of intuition and experience dictated the final design. Kai and Aaron co-designed the manifold which was then fabricated by Kai Staats and Heracio of the AirQuest team. The final product is air tight and highly efficient.

The SAM lung was designed as a prototype, something to perform a few seasons, not much more. As such, it was not sealed from the rain which over time resulted in substantial rust to the interior surface of the upper shell.

Starting in the spring of 2021 Trent Tresch scraped and sanded the loose paint. In December Kai returned to this effort, preparing the surface for primer. Volunteer Colleen Cooley and Kai Staats applied a coat of direct-to-rust primer, which both stabilizes the rust and prepares the surface for the final, enamel top coat.