Starting with the angle grinder (a beast of a machine!), its function is based on (a) a high coefficient of friction between a rotating surface which is harder than the surface to which it is being applied; which causes (b) abrasion between the two surfaces, and subsequent (c) removal of material as the disc rotates at a high velocity with strong angular momentum (torque). As greater pressure is applied more material is removed, to a degree.
The challenge is to find the balance between the applied pressure and potential overheating. If the material becomes semi-molten, it is moving toward a liquid state which reduces the speed of material transfer due to reduction in friction. Hot enough to toss off small bits, but cool enough to remain solid. What baffles me is the structural integrity of those grinding discs. You can lean hard on them, directly or at an angle and they do not suffer divots nor shatter. Incredible!
Removal of the second, large gas analysis box was quite the challenge. Two times larger than the one on the east side of the north exterior wall of the Test Module, this one was equally wedged in place, the information panels clearly added at a later date. We attempted to remove all of the white “7” shaped supports but could not remove the middle two as there was simply not enough play with the box in beneath to force them loose (After thirty years of steel posts in steel sleeves in concrete, it is a miracle we got them out at all!)
Trent and Cameron used a makeshift lever to raise the box and insert threaded rod roller beneath, Egyptian pyramid style. We then attached load straps to the box, with Cameron on one and Trent and myself on the other.
“On the count of three! One … two … three—pull!”
Nothing. We tried again and again, but no go.
Then it occurred to me that my Subaru Crosstrek offers a great deal more horsepower. I backed my car. Trent attached one end of the load strap to my trailer hitch and with almost no fuel applied it came right out. What made this interesting to me is that when the box came off the rollers, my car hesitated for a moment. I had barely pressed the pedal to that point, and added a little more fuel. I could feel the power automatically transfer from one drive wheel to another, back and forth in fractions of seconds. The car was sensing slippage and correcting its power transfer accordingly. Not a mote of dust was raised other than that which was pushed by the box as it came off the rollers and into the dirt.
With the box gone the middle posts that held the information panels remained. The others came free with an application of a rust-breaking lubricant and repeated, swift kicks followed by jiggling and lifting. But the middle two were quite a bit more stubborn. As an archaeologist who best understands tool use by our ancestors, Cameron resorted to a calculated application of caveman physics—beat the [crap] out of it! It worked!
The removal of the dry, aged grow beds two weeks ago threw a tremendous amount of dust into the air, coating the entire interior of the Test Module. To clean the space frame and windows, Trent climbed up into the higher reaches of the Test Module using the safety harness provided by Biosphere 2. He is a former climbing instructor and as such felt right at home far above the floor. Throughout this project we have been reminded of the physics of static electricity when working with the shop vacuum. Any time we are pulling a large volume of fine dust into the plastic nozzle and corrugated tube, the acceleration of those particles in a volume of dry air causes a rapid, massive build-up of free electrons at a very high voltage (likely tens of thousands of volts, at a relatively low amperage). This presents such a challenge that if one does not maintain a hand on the metal frame at all times, the resultant shock can be quite painful. Wearing gloves only further insulates the body such that the pressure increases to make the jump. As such, Trent was hanging on for more than the obvious reason.