The Executive Officer assigned other tasks not directly concerned with formal training. Matt was appointed the ship's "farmer." As the hydroponics tanks supply both fresh air and green vegetables to a ship he was responsible for the ship's air-conditioning and shared with Lieutenant Brunn (he tasks of the ship's mess.
Theoretically every ration taken aboard a Patrol vessel is pre-cooked and ready for eating as soon as it is taken out of freeze and subjected to the number of seconds, plainly marked on the package, of high-frequency heating quired. Actually many Patrol officers fancy themselves chefs. Mr. Brunn was-one and his results justified his conceit - the Aes Triplex set a good table.
Matt found that Mr. Brunn expected more of the "farm" than that the green plants should scavenge carbon dioxide horn the air and replace it with oxygen; the mess officer
wanted tiny green scallions, fragrant fresh mint, cherry tomatoes, Brussels sprouts, new potatoes. Matt began to wonder whether it wouldn't have been simpler to have stayed in Iowa and grown tall corn.
When he started in as air-conditioning officer Matt was not even sure how to take a carbon-dioxide count, but shortly he was testing his growing solutions and adding capsules of salts with the confidence and speed of a veteran, thanks to Brann and to spool #62A8134 from the ship's files- "Simplified Hydroponics for Spaceships, with Growth Charts and Additives Formulae." He began to enjoy tending his "farm."
Until human beings give up the habit of eating, spaceships on long cruises must carry about seven hundred pounds of food per man per year. The green plants grown in a ship's air-conditioner enable the stores officer to get around this limitation to some extent, as the growing plants will cycle the same raw materials-air, carbon dioxide, and water-over and over again with only the addition of quite small quantities of such salts as potassium nitrate, iron sulphate, and calcium phosphate.
The balanced economy of a spaceship is much like that of a planet; energy is used to make the cycles work but the same raw materials are used over and over again. Since beefsteak and many other foods can't be grown conveniently aboard ship some foods have to be carried and the ship tends to' collect garbage, waste paper, and other trash. Theoretically this could be processed back into the cycles of balanced biological economy, but in practice this is too complicated.
However, all mass in an atomic powered ship can be used, if desired, as reaction mass, mass for the rocket jet. The radioactive materials in the power pile of an atom-powered ship are not themselves used up to any great extent; instead they heat other materials to extreme temperatures and expel them out the rocket tube at very high speeds, as a sort of "steam" jet.
Even though turnip greens and such can be used in the jet, the primary purpose of the "farm" is to take the carbon dioxide out of the air. For this purpose each man in the ship must be balanced by about ten square feet of green plant leaf. Lieutenant Brunn, with his steady demands for variety in fresh foods, usually caused Matt to have too much growing at one time; the air in the ship would get too fresh and the plants would start to fail for lack of carbon dioxide to feed on. Matt had to watch his CO2 count and sometimes build it up by burning waste paper or plant cuttings.
Brunn kept a file of seeds in his room; Matt went there one "day" (ship's time) to draw out Persian melon seeds and set a crop. Bran told him to help himself. Matt rummaged away, then said, "For the love of Pete! Look at this, Mr. Brunn."