Construction

As shared in a prior post, Kai Staats and Nathan Schmit were successful in cutting free one of the original pressure doors from the basement of Biosphere 2. This door had not been used for some twenty years and is a perfect fit for SAM, where it will serve as an emergency exit from the Crew Quarters space and provide a small but vital natural lighting portal.

It was the original intent to retain nearly the full steel plate into which the door was mounted such that it would fit neatly into the opening of the 40 foot shipping container without additional framing. However, upon inspection prior to cutting, Nathan and Kai discovered that that heavy 1/8″ thick sheet was heavily warped and would have been very difficult to weld without a great deal of bending and fill. Therefore a small frame was cut around the door. While the total mass was reduced to ~150kg (330lbs), some rigging and planning was required to safely maneuver the door into position in its new frame.

As with the end of the 20 foot container, the original doors were removed and 1″x3″ steel tubing was installed as frame and studs. The tubing is bolted to the thick steel frame of the shipping container, with temporary brackets holding the studs until welded. Nathan welded the studs to the frame, then the door, and finally the 12g sheet metal which forms an air-tight seem around the entire frame and to the door.

During the SIMOC-SAM Team Summit the first full SAM pressure test was conducted with the 40 foot container end in place. While the welds themselves held strong, leaks between the layers of the original floor were detected and then mitigated over the subsequent three days, before the holiday break.

The SAM Workshop will house a power panel, mini-split heating and cooling, 3D printer, sewing machine, and repair bench with a variety of tools for in-hab repair and fabrication. This room has a five layer sealed floor topped with steel sheets and Insofast brand, closed-cell foam panels with built-in plastic studs. On these panels we have added fiberglass reinforced panels (FRP) to protect the insulation, provide a strong structure on which to mount electrical conduit, shelving, and lights; and provide a readily cleanable surface.

The south end of the 40′ shipping container, soon to be completed as the crew quarters at SAM, will include an emergency exit for visiting crew. We are proud to have been gifted yet another pressure door assembly from the original Biosphere 2. Kai and SAM team member Nathan cut and with the help of Tim move the mass from the ‘technosphere’ to SAM. Nathan spent the better part of a day preparing the door frame for welding. On Tuesday, December 13 it will be attached to the new steel stud wall, and soon thereafter put into function for the first time in some twenty years.

Patching the 40 foot shipping container has proved to be significant challenge, setting us back two weeks from our intended schedule. Yet, each day we make progress toward a functional pressure vessel, each test demonstrating that our efforts are worth while—the audible space grows more quiet and the rise in pressure more rapid.

In parallel Luna and Kai applied paint to the workshop floor, bridges, and exterior roof of the airlock while Ezio (visiting from Italy) and Grant (visiting from Vietnam) worked on SIMOC Live, a new version of the Mars habitat simulator that will function as the live data capture system for SAM, collecting data in real-time from dozens of in-hab sensors.

This week we welcome volunteer Bindhu Oommen, a general surgeon from Dallas, Texas. Bindhu learned of SAM during the 2022 Analog Astronaut Conference and will be returning one week each month for the foreseeable future. We appreciate her attention to detail, surgical precision (sorry, it has to be said), and willingness to travel a great distance to assist our team. While she is gaining skills in fabrication, our team is entertaining conversations about the challenges of space medicine.

As noted in a prior post, we discovered that the silicone rubber patches applied to the lung in 2021 had failed. On Wednesday we carefully measured and cut the recently obtained EPDM rubber and on Thursday John Z., Bindhu, and Kai applied the rubber patches to the lung using the same procedure as that used to repair inflatable river rafts (rubber obtained from Discount Rubber Direct and glue from NRS).

On October 20 and 21, October 25 and (after applying the new patches) on November 11 (this essay) we conducted pressure tests of the expanded vessel at SAM. These tests are a means to locate leaks, fix those we can immediate address, and improve our methods for the continued sealing of the SAM habitat analog.

It is important to note that the various dips (graph a top) are the opening and closing of valves or temporarily patching holes during the test (Mark Watney—PVC tape is far more effective than duct tape). Ultimately, we are shooting for a smooth, steep rise from the start of the blower (~4.5 minutes on graph) to the maximum pressure when the lung is free from the ground (~10 minutes). The total duration of the test is not indicative of the leaks, rather when we terminated the blower, opened valves and/or doors, and allowed the lung pan to settle again to the floor.

Once again, we engaged simple auditory inspection to detect the leaks, and the application of incense smoke to visually see leaks we could not hear or to confirm the exact location of those we could hear. Ezio returned as our super sleuth outside of the SAM pressure vessel and to operate the blower. He located an additional three leaks, two by listening and one by smell, which was unexpected by highly fortunate.

Project management is a complex endeavor. Finding the right balance of give and take, guidance and learning is imperative for the long-term health and success of a team as diligently involved as that which is constructing SAM.

When Luna ventured to the cafe in Oracle before departing for an early weekend, John, Bindhu, and Kai found themselves in the challenging situation of having an extra pastry. This is one of those moments in which a team could be catapulted into the kind of grievance and mistrust from which it may never recover, or move through the situation with grace, stronger than ever.

We approached this with the same engineering precision applied to the fabrication of SAM, and the outcome was completely satisfactory.

This past week has seen tearing things apart more than putting them together, which feels like progress lost even when we know it is the best way forward. In order to weld the perimeter of the end of the 20′ container we had to remove the west-end insulation panels installed this summer—two days of effort undone in a few hours. We learned how well the construction adhesive adhered and the properties of expansion foam in small and large spaces. What’s more, we cut channels in the side walls in order to visually see (and later test) the quality of the weld by exposing the seam on the inside for our auditory and visual inspection during consecutive pressure tests.

Between the Tuesday, November 1 and Friday when UA welders Charlie and Chad were onsite, we filled our days with myriad small projects, the kind otherwise left for when major efforts are complete. It was hard to focus, at first, but in looking back it feels good to have checked-off so many tasks.

• Cleaned the conduit from the TM to the site of the original, external data terminal.
• Removed the 2021 lung patches with heat gun and careful application of pressure.
• Installed the insulating ceiling panels to the SAM Air Intake Room (AIR).
• Chipped the entrance to the TM-to-lung tunnel in prep for primer.
• Removed the TM outer (non-sealed) door and hinges; sanded, primed.
• Scraped, sanded, and primed the final, inner segments of the lung pan.

In a project such as this, there are moments no one will forget. One such moment was when we decided to reverse the flow of air in the shop-vac and blow any debris out of the two PVC conduits we retained that once carried power and data from the TM to the computer terminal and data analysis terminal. We were horrified and at the same time overtaken by laughter when not only did a cloud of dirt, seeds, droppings, sticks and twigs fly into the air, but a mummified rat too!

We realized then we had to clean these pipes well beyond simply blowing air. We repeatedly filled them with water and bleach and using the vacuum in reverse, created a water fountain until it ran clean (banner at top). The words “Disgusting!” and “Oh no! That is really gross” were heard over and over followed by “Let’s do it again!”

With our second full week back at SAM we remain focused on sealing and pressure testing, with some landscaping of the desert immediately surrounding SAM after a summer of intense rain and immense growth. We welcome Ezio Melotti, lead developer of the SIMOC project, and the return of Anastasia Stepanova, former engineer for the SIRIUS analog in Moscow, now PhD student at the Colorado School of Mines and SAM team member.

In preparation for this third pressure test of the expanded SAM vessel, we applied a proper fill of Dow-Corning 795 silicone in the window channels, providing the needed wider, deeper seal. We activated the lung blower in the SAM Air Intake Room (AIR) and as with the prior test the lung rose and the pressure increased.

Using the technique described by William Dempster and Linda Leigh, we lit incense and moved slowly through SAM, module to module, interface to interface and sure enough! —we were able to visually confirm the leaks we could hear, and discover a few more too.

Through this test run it became clear that the plates that cover the end of the 20′ shipping container will need to be welded for the complex assembly of steel stud framing was not something we could satisfy with 795 alone, especially if we desired to apply something more than a finger bead to those critical areas.

Before deflating the lung, Ezio notified Kai (via radio) of a previously unnoticed hissing sound. Kai entered the lung from the TM (through the tunnel) and discovered that roughly half of the patches applied to the holes in the original membrane were compromised—dried and cracked in just a little more than a year. This was completely unexpected, but perhaps a known function of siliconized rubber that was overlooked. Kai, John, and Luna have subsequently, carefully removed the old patches with new EPDM material (similar to the original membrane) on its way to Biosphere 2.

What’s truly incredible is that the lung rose at all given the number of holes in the membrane in addition to the known leaks in the TM, 20′ and 40′ shipping container. This gives us great confidence in our ability to maintain pressure for long periods of time, days, possibly weeks once all leaks are properly managed.

The UA welders will arrive on Tuesday to complete seals of two more interfaces, and then we’ll be back in the running for another pressure test and continued construction. Stay tuned!

In preparation for our first pressure test of the expanded SAM vessel, we applied a thin fill of Dow-Corning 795 silicone to the channels where two original Test Module windows were replaced by a single steel hatch plate in late 2021, just enough to hold a temporary seal. 795 is an incredible product, remaining flexible after 35 years (even in external Arizona applications).

It is our intent to apply the method used by the Biospherians. While 795 provides a flexible, long-lasting seal, it is gas permeable. While a shallow seal will hold pressure immediately, it will leak more gas than a deeper seal, over time. Therefore we will ultimately apply a silicone bead approximately 3/4″ wide and 3/4″ deep for the given pressure differential.

After synchronizing the Vernier barometric pressure sensor and two cell phones with barometric sensors, all three of which register to one one-hundredth of a PSI (0.0n), and set the timer, Ezio and Kai remained outside while John and Luna were sealed within. We activated the lung blower in the SAM Air Intake Room (AIR), the lung rose, and … we could hear all kinds of leaks across the TM, 20′ and 40′ shipping containers! Most of these leaks were anticipated, some new and unexpected. It was an exciting event from start to finish. John and Luna marked leak points with blue painters tape while Kai recorded leak points with a camera on the outside. The test ran roughly one hour and twenty minutes, start to finish, and was a complete success given the function of the lung and what was learned.

We recorded a barometric pressure baseline, the start of the blower, rise in pressure, maximum pressure achieve when the lung plate lifted from the floor, and the gradual drop of the lung plate and pressure when it again sets down. We achieved roughly 50% of the desired 0.1 PSI increase in pressure, as calculated in our June 2021 pressure test.

John and Luna patched a number of holes and ran a second test the following day. The third test was run following the Mars Society conference.