When a Navy submarine goes to sea on a month-long voyage, the lettuce, tomatoes and other fresh fruits and vegetables on board run out in a week or two, forcing the crew to rely on canned, frozen or dehydrated products.
But what if subs had their own gardens where food could be grown under lights?
The U.S. military is testing out the idea by growing plants hydroponically - that is, with nutrient solution instead of soil - inside a 40-foot shipping container on dry land at a laboratory outside Boston.
Engineering technician Don Holman, who grew up on a farm in Michigan before serving 30 years in the Navy, is running the $100,000 project at the Army's Natick Soldier Research, Development and Engineering Center. He said sailors have been asking for more produce.
"When you give someone something they want, it improves their morale. And they perform better when morale is up,'' said Holman, who will present a technical report in September so the Navy can decide whether to attempt gardening beneath the sea.
This is the second phase of the testing. Holman first tried to grow 83 varieties of fruits and vegetables to see which ones did best. The leafy greens and green onions thrived. Root vegetables did fairly well. Strawberries and rhubarb grew but probably wouldn't produce enough to make it worthwhile, Holman said.
The cucumbers, on the other hand, were a mess. The vines climbed everywhere. And the large leaves on the zucchini plants blocked the lights. The tomato plants grew but didn't produce fruit because the lighting wasn't bright enough and the temperature was too low.
Holman replanted the varieties that did well. He is now tending to those seedlings to see how much they produce.
On the dirt- and insect-free "farm,'' as Holman calls it, the plants are growing in trays of peat moss plugs and will be transferred this week to more than 250 towers suspended from overhead tracks and filled with growing material made of recycled plastic. Strands of red and blue LED lights dangle from the ceiling.
He said vegetables could be planted before a vessel went to sea so that they would be ready for harvesting during the mission.
Retired Navy Capt. Ronald Steed, a former sub skipper, said it would be a real challenge to fit a garden on a submarine, where space is extremely tight, "but if they could do it, that would be awesome.''
The newest fast-attack submarines are nearly 400 feet long and carry a crew of about 130, while ballistic-missile subs stretch about 560 feet and can have a crew of 170.
"I doubt that every meal could have fresh fruits and vegetables,'' Steed said, "but if you could do it from time to time, it takes something that's really essential to crew morale and makes it better.''
The idea originated at the Naval Undersea Warfare Center, a research and development lab in Newport, Rhode Island.
A fast-attack sub has enough food on board for at least 90 days when it leaves for a deployment from the Navy base at Groton, Connecticut, said Lt. Cmdr. Christopher Shutt, supply officer for the waterfront.
After about a week, the lettuce in the salad bar becomes slightly translucent, then runs out, and the fresh tomatoes, carrots and celery are gone, too. Thawed fruit, bean or pasta salad, and soups take their place at the salad bar. Pudding occasionally shows up when the fruit is gone.
It's not this way the entire time - a submarine will get fresh food when it stops at a port or another ship delivers it.
Chief Culinary Specialist Brian Pearson, who serves on the submarine USS Missouri, admitted that nothing beats fresh ingredients but said the crew still really likes his spaghetti or lasagna, made with canned tomatoes, dehydrated onions and extra spices. For mashed potatoes, he said, he can transform dehydrated potato flakes with butter, garlic and sour cream.
For his part, Steed allowed that the food aboard submarines is pretty good, considering what the cooks have to work with.
"It's just kind of one of those things where you accept that you're not going to have fresh fruits, vegetables, eggs,'' he said, "and given that, they do a great job.''