He heads a "bed rest" study designed to learn more about how the lack of gravity affects the sense of smell and, in turn, impacts on what one tastes and chooses to eat. In space, because there's no gravity to pull it downwards, fluid rushes to the head. You might not have seen it in the movies or on television, but astronauts develop puffy faces, rather than heroically chiselled jaws, and "chicken legs" because of this redistribution of fluid.
It's believed this increased fluid causes swelling in the nasal tissues, which reduces room in the nasal cavity. This may restrict the amount of air that can be inhaled as well as altering the senses of smell and taste. Unable to enjoy the same food they do on Earth, astronauts experience odd food cravings or, more worryingly, food fatigue.
Bored with food, they reduce consumption and risk not getting the nutrients they need. This can make them vulnerable to the same deficiency diseases that seafaring and polar explorers once battled.
Given this, you could say the study Caldwell is involved with is an extension of the work started in the 18th century by the likes of Captain James Cook who sought ways to stop deficiency diseases like scurvy.
For Nasa's food technologists, the challenges of provisioning a spaceship and its crew are enormous. There are strict budgets - to put just 500g of food in space costs US$10,000 ($12,000) - and a lack of room on rockets for food storage means no pantries laden with tinned or fresh food. There is the added issue that there are no ports at which to dock and restock, as well as the problem of zero gravity - which means, to quote astronaut Sandra Magnus, who has tried cooking in space, "nothing stays put".
So astronauts eat a rigid calorie-controlled diet of lightweight (and therefore cheaper to transport) heat'n' eat or just-add-water dehydrated meals, which are prepared on Earth and usually have a shelf life of nine to 12 months. Meals come in vacuum-sealed packages that can be warmed in a small convection oven or "cooked" by adding hot water, massaging to mix and snipping open with scissors, for eating through a small incision. They tend to be heavily sauced or sticky - think lasagne and hearty casseroles - to give them extra stick-ability, or wrapped in tortillas.
Despite these ingenious solutions, the novelty of eating a meal in a pouch you can Velcro to your spacesuit soon wears off. Former Nasa astronaut Edward Tsang Lu, who spent six months in space in 2003 including time on the International Space Station, told the Cornell Daily Sun newspaper that menu fatigue is like eating three meals a day, seven days a week in the same restaurant: "Even if you like the restaurant, after a few weeks you just want to eat somewhere else."
Fatigue set in despite having a two-week rotation of meals - including dishes such as crawfish etouffe and Russian lamb with vegetables. (The rehydrated shrimp cocktail and apricot cobbler dessert are also said to be good by those who have tried them.)
For someone away from Earth, say on Mars, for three to five years, serious food fatigue could become a big problem. And life on Mars could be very bleak without the daily food rituals of cooking, eating and using food to celebrate special occasions. The sweet taste of being one of the first people to live on another planet could quickly become soured.
So last year, Nasa awarded a US$900,000 grant to a Cornell University team for a three-year series of studies into ways to alleviate food fatigue and cook on a Mars space station, where there would be gravity, using lightweight shelf-stable ingredients and limited cooking equipment.
Caldwell's bed rest study is a pivotal part of the project because it considers the extent to which basic physical changes can affect the desire to eat. It also seeks ways to remedy these alterations, which, he says, could be as simple as astronauts taking nasal decongestants before blast-off and during their missions.
To a sleep-deprived parent of young children, like me, taking part in the bed rest study where you get paid to lie in bed for three months initially sounds like a dream come true. But like most things that seem too good to be true, there's a catch - or two.
For starters, research subjects can't exactly lie flat on their backs. For the purposes of Caldwell's research, their heads have to be six degrees below their feet to replicate the weightless environment of space. This means they experience the same rush of fluid to the head as astronauts and the corresponding congested feeling like they're coming down with or getting over a head cold.
But they can't even think about getting up to blow their noses - or, for that matter, to go to the toilet or take a shower. Subjects are provided with tissues, are brought bedpans and are showered on a waterproof gurney because lying in bed (with the head lower than the feet) means exactly that.
They can watch DVDs and TV, read books and magazines, do crosswords and jigsaw puzzles, trawl the internet or whatever else fills their waking hours but they mustn't raise their heads or get up. Nor must they fold the regulation 5cm-thick pillows over to prop themselves up; any sign of that and those monitoring the subjects 24/7 - call them the pillow police - will be straight in to admonish them.
It's enough to drive a person to drink or eat chocolate, but these stimulants, along with coffee, are banned. Test subjects might, however, get a chance to sniff them to determine how their sense of smell is changing the longer they lie in bed.
Subjects are regularly brought substances to smell and their changing reactions are recorded; similarly, the way their attitudes change to the calorie and portion-controlled, but tasty, food they are served is monitored, too.
"The meals are nice, definitely better than hospital food. I'd liken them to home-cooked comfort foods. There's apple pie and icecream, roast dinners, corn chowder, barbecued pork chops and, being Texas, quite bit of Tex-Mex food," says Caldwell.
He will study up to 24 people who meet strict criteria willing to undergo the bed rest study. But would he do it himself?
"If it meant I could be an astronaut and go into space, then sure I would but ordinarily, no. I tried it for a few hours and definitely experienced the start of that congested feeling. I can't say it was pleasant. We've had a couple of PhD students do it and use the time to finish their thesis, so it can work well for some people."
Ask if anyone has ever decided enough is enough and jumped out of bed to walk away, Caldwell laughs. As he explains, you can't walk out with your head held high if it all becomes too much - after just a few weeks in bed you'll likely experience muscle wastage, so you'll jump out and collapse on the floor. It means bed rest subjects spend a couple of weeks after they "get up" undergoing intensive physiotherapy to get them back on their feet.
There's no shortage of volunteers who want to take part in space-related research. Groups like Astronauts For Hire, a non-profit organisation started in 2010 to "recruit and train qualified scientists and engineers for the rigours of spaceflight", and Nasa hopefuls are always keen to sign up for such studies.
If Caldwell's name rings a bell, that's because he featured in Canvas a year ago in a story about people with double lives. Back then, the former theatre lighting and event designer was living in upstate New York and doing post-doctoral research at the State University of New York's Upstate Medical University into the electrical properties of the heart, while still dabbling in his old career.
He moved there to be closer to Nasa networks after spending 10 years of juggling work and study to gain a PhD in bioengineering to qualify him as a space physiologist. Originally, he wanted to be an astronaut but, realising he may have left that too late, helping ready astronauts for space travel or rehabilitate them when they returned to Earth became his new goal.
At SUNY, he met a graduate student who had worked with the head of the Cornell study, Dr Jean Hunter, who has spent 15 years studying space life support engineering - namely the best ways to feed people in space - and co-leads the ongoing Mars Desert Research Station (MDRS) Food Study. This uses the MDRS in Utah to test the acceptability of a food system based on shelf-stable stored foods and ingredients. So Caldwell called Hunter and asked if he could work for her.
"The reason I'm here and doing this work is because, as a New Zealander, I wasn't afraid to ring up high-level people and ask for a job. I know some of my American colleagues were shocked by this because they have a prescribed way of doing things but New Zealand is a more egalitarian country where we don't believe we shouldn't do something. We're happy to give something a go, to try something new and see what happens."
What happened was Hunter asked Caldwell to send his details and she'd contact him if something came up. He didn't hear back so accepted a highly competitive American Heart Association Fellowship grant to continue his research at SUNY. That's when Hunter called, said she had a position and could he move to Texas within six weeks?
While Caldwell is occupied in Texas for up to two years on the bed rest study, his colleague, associate professor Kim Binsted from the University of Hawaii, will head a project where eight volunteers, selected from 700 applicants, will spend four months in a Mars Research Station to be constructed on the lava fields of Hawaii Island.
Like the Utah desert, the stark environment of a Hawaiian lava field is similar to the surface of Mars, Binsted says, and there is very little in the way of flora and fauna to stimulate the senses or tempt anyone into trying to cook with.
"It's definitely not the palm-fringed beach that you might think of when you imagine Hawaii."
The research station, possibly to be constructed from shipping containers, will be small - around 244sq m - leaving limited space for food storage and cooking equipment like a hot-plate, small convection warmer, a breadmaker and basic utensils. Back in New York, Hunter is working with Professor Rupert Spies, a chef and senior lecturer at Cornell's School of Administration, to devise meals using ingredients like flour, sugar, oil, shortening, powdered egg and milk, dried beans and fruit, and textured vegetable protein (TVP) which are shelf-stable for three to five years.
Binsted says the aim is to see if it's worthwhile having a crew on Mars cook their own food; the trade-off is that the more time they spend cooking, the less time they have for other duties.
She got involved with the Cornell study after serving as a crew member in another long-term food study in the Canadian High Arctic in 2007. It means she has first-hand experience of cooking in confined conditions with limited ingredients.
"I made sweet'n' sour TVP [textured vegetable protein] balls and they were especially popular, probably because of the flavour. We learned to make mozzarella cheese out of powdered milk and it works as a pizza topping."
Having a small aero-garden where they grew lettuces and herbs was important, too. Binsted acknowledges not enough grew to make a difference to their nutritional intake but having something green and crisp on the plate was a morale booster.
"We know food, its preparation and the associated rituals are an important part of daily life that go beyond fuelling the body.
"Food is social and on a long-term mission it means a lot to crew members if they can, for example, bake someone a cake on their birthday or mark other special occasions and events by sitting down and sharing a meal."
