Saturday, May 11, 2019

Atmosphere Control and Monitoring Equipment

Of the parallels that spacecraft have with submarines, the most analogous to me is atmosphere control. Generally, heat dispersal is less of a problem as seawater is an excellent heat sink, and submerged maneuvering is more intuitive than orbital mechanics. Both the monitoring systems and the control systems are going to have both primary, fixed to the ship, and secondary systems, portable, that can be useful for details. The monitoring systems are those providing information about composition and  pressure, while control systems allow the crew to manipulate the gas mix. There is a simple atmosphere analyzer, giving the users breathablity and general class of the atmosphere in the game, costing Cr 150 and weighing 1 kg. However, exploration and mystery oriented campaigns and adventures may desire more detail than a simple system.

The primary monitoring system would be a computerized combination carbon dioxide detector and mass spectrometer that is built into the ship. The current CAMS Mark II system is about the height of a man, and can take samples from a variety of shipboard locations. A system like this would be part of the ship's engineering section, and repaired during annual maintenance. This could also be used to test samples captured from an unknown or poorly described atmosphere, giving the partial pressures of the component gasses. Future versions would be smaller and more reliable of course.

Draeger bellows and tube package
Secondary portable systems are available, but have to split up the monitoring functions. For oxygen content, I used an aging Servomex tester where the user had a bulb to bring in air to the sensor, and it gave a percentage readout of oxygen content. For detecting the more unusual gasses, the standard issue was a Draeger hand pump kit. This gadget consists of a hand pump kit, and a glass tube with a reagent that indicates the concentration of a chemical using a color. One end of the tube is broken off, the tube inserted into the pump, the pump is used the requisite number of times, and it shows the concentration of  a gas where the sample was taken. To check for another gas, the system must be removed to a clean atmosphere area, purged, and a new tube inserted. Also, a single purpose hydrogen tester was in use, showing atmospheric hydrogen percentage.

Electrolytic Oxygen Generator.
Atmosphere control is provided by two processes. Oxygen partial pressure is maintained by the use of an Electrolytic Oxygen Generator. Pure water is distilled, mixed with potassium hydroxide, and subjected to a high voltage, splitting off the oxygen and hydrogen into 'pure' gasses. The oxygen could either be stored at pressure, or dispersed through the ventilation system. This machine was considered to be one of the more dangerous pieces of equipment on board, because nobody wants an undersea hydrogen explosion. Carbon dioxide is removed by an amine based scrubber system, that leaves a peculiar odor in the air, and it sticks to the clothes. Carbon monoxide along with hydrogen, are removed through a burner that runs hot air across a hopcalite catalyst bed.

Again, there are secondary systems for oxygen and carbon dioxide level maintenance. Carbon monoxide is just not seen as an immediate item for emergency removal. Oxygen levels can be maintained by using the stored banks, or oxygen candles. The banks just release oxygen at a bleed point, but the air must be circulated to ensure there is no harmful build up of oxygen to dangerous levels. Candles provide oxygen to directly to the internal atmosphere using a thermal reaction. Carbon dioxide is removed by using lithium hydroxide in two fashions. There is an active hopper system that moves air through lithium hydroxide canisters using a fan, and a passive curtain system where air passes over a hanging sheet with small amounts of lithium hydroxide. One of the problems with these systems is that it is possible to over-pressurize the atmosphere. In one case, we could not open the water-tight door to the engine room because of the pressure differential. More serious problems from over-pressurized areas can include decompression sickness. Pressure build up can be mitigated by compressed air systems taking in excess, venting to space, or storage as part of a reaction control system.

The major equipment is expected to be aboard a spacecraft. Notably, the ISS uses chemically similar systems, and recycles waste products for extra water. I would expect that part of a berthing cost would be refreshing some consumables as well as the actual landing. Starships operating off in the wilds with few resources will place more space in cargo for consumables, and gas giant refueling may make the atmosphere go stale a little faster. Given the smaller ships that players have access to, backups may be limited. Most ships should have a gas tester kit as part of damage control, and the basic atmosphere analyzer was noted as being in the ship's locker for two short adventures. Oxygen candles are a disaster risk, as they almost destroyed Mir in the 1997, and killed two sailors aboard HMS Tireless (S88) in 2007.

As a way to encourage action, this gives the referee different ways to encourage play and see how players react. This is also a way to include some chrome on how systems operate. The atmosphere plant gets a bit more detail, and here are a couple more tools to use in a variety of situations.

New Equipment

Hand Gas Detector Kit, Cr 500 for kit with one pump and 18 gas tube sets in a hard case. Cr 100 for the pump, Cr 25 for set of five tubes each detecting one gas. The kit weighs 1.5 kg, while the bellows weigh 250 grams and tubes weigh 50 grams per set of five.  TL7. Kits include CBR detection, and toxic leak, as well as a standard kit used on most ships. 

Oxygen detector. Gives a current atmospheric oxygen percentage and carbon dioxide percentage. Runs off a rechargeable battery good for six hours. Cr 500, 2 kg at TL8, TL 10, half cost and weight.

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