Postcards from Mars

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.

Mixing, pouring, and finishing concrete is no small undertaking. While it can be done bag by bag, shovel by shovel for small jobs, the critical nature of a uniform density, physical and chemical consistency demands proper mixing and delivery by a professional concrete company and finish by the experts.

Daniel, Ricardo, and Fernando are experts in their field. They estimated the concrete delivery to within a half wheel barrow and were able to cut and position the sauna tubes for the concrete footings for the shipping containers to a level of perfection. Next, we prepare the shipping containers and west side of the Test Module for extension of the pressure vessel and in January place the containers as the foundation for the new Crew Quarters at SAM.

With the second phase of construction of SAM we are quickly transitioning from refurbish to new construction (which is far more enjoyable). In the spring of 2021 we poured a new concrete slab between the Test Module and its lung to the south in order to provide a foundation for the new mini-split A/C units, and to reduce the amount of debris and dirt that got kicked up when working in that area. The result was clear, we needed to go ahead and pour a slab around the east and west sides of the Test Module when we moved to pour the concrete footings for the 20 and 40 foot shipping containers, our soon-to-be crew quarters.

Daniel, Ricard, and Fernando are a unique team. Highly skilled, extremely knowledgeable, and absolutely a joy to work with (as well as constant comic relief!, they were able to prepare the site from gravel and dirt to line and laser level in two mornings. Kai Staats assisted with validation of the critical measurements and sketches for the precise location of this exciting addition to SAM.

Next week, the concrete will be poured!