Science writer Mary Roach has explored some unexpected corners of the scientific world, from Elvis’s constipation issues to a sheep rancher determined to test the weight of the soul. In her latest book, Grunt, she dives into the world of military science. Roach learns just how much research goes into every aspect of preparing for war, from figuring out how to deal with diarrhea in the field to designing a camouflage pattern that doesn’t get men killed to finding ways for service members on submarines to get some shut-eye. Here are just a few of the quirky, unexpected things we learned about the science of war and the U.S. military from the book.

1. ZIPPERS CAN POSE A MAJOR PROBLEM.

By nature of his occupation, a sniper spends a lot of time laying on the ground. If he’s wearing a jacket that closes in the front with a zipper, sand, dirt, and other rubble will end up grinding its way into the zipper's teeth, and it will get stuck. It will also probably stab him uncomfortably in the stomach. Nor is Velcro an option. “I have heard stories of Special Operations guys whose Velcro put them in danger by revealing their position,” Roach writes. As a result of these complicated considerations, the Army has a Hook and Loop Task Group to figure out how to fasten clothing for soldiers in a safe, comfortable way. The latest sniper suits close on the side, rather than in the front, with a flap to protect the buttons, which are themselves tested for durability in the face of weapons like steel blocks, hot irons, and boiling water.

2. MILITARY FASHION CAN BE ARBITRARY.

While Army uniforms are rigorously tested and thoroughly regulated—button regulations alone require 22 pages of specifications—there are aspects of military dress that are less about function and more about the fashion decisions of certain high-ranking officials. In 2005, for instance, a high-ranking general picked an untested camouflage pattern to be used to hide troops in all terrains, whether it be deserts, cities, or the woods, eschewing all of the 13 patterns developed and tested by a committee created just for this purpose. It didn’t work out so well. “The new camouflage performed so poorly in Afghanistan that in 2009, the Army spent $3.4 million developing a new and safer pattern for troops deployed there,” Roach explains.

That’s not the only military fashion decision that seems arbitrary. The blue camouflage worn by Navy personnel doesn’t actually serve a useful function, according to one commander, since it just makes it harder to see people who fall overboard. And those fancy black berets Army soldiers wear? They may be less useful than a cap with a brim, but man, they look cool. In 2011, responding to soldiers’ complaints, the Army began providing its soldiers with patrol caps again.

3. EARPLUGS ARE CONTROVERSIAL.

War is loud, whether you’re on the battlefield or just training. A Black Hawk helicopter emits a din of 106 decibels, and the sound of firing an ATT4 anti-tank weapon clocks in at 187 decibels. For reference, you can only be exposed to 115 decibels for 30 seconds before incurring hearing damage. But just how to protect soldiers’ ear drums is complicated. Earplugs cut sound by about 30 decibels, but they dampen noise indiscriminately, meaning that just as explosions get quieter, so do the your commander’s orders and the sound of enemy fire. Furthermore, it’s almost impossible to shove an earplug far enough into the ear when you’re wearing a combat helmet. As a result, the Veterans Administration spends $1 billion a year treating hearing loss and tinnitus.

4. STUDYING IEDS REQUIRES MORE THAN YOUR TYPICAL CRASH DUMMY.

Right now, there’s no good way to study how improvised explosive devices affect the human body, or how different military equipment could protect against them. The crash dummies currently available are made for testing the physics of car crashes on the human body. Car crashes come from the front, back, or side, but explosive devices impact the body from below, exploding beneath someone’s feet or under their vehicle. So the Army is building its own, IED-specific dummy called the Warrior Injury Assessment Manikin, or WIAMan. The device won’t be ready until 2021, and in the meantime, the Army has to use cadavers if it wants to understand the ways that IEDs affect the human body realistically.

5. WOUNDED SOLDIERS ARE VERY WORRIED ABOUT THEIR JUNK.

The widespread use of IEDs in combat zones has invigorated military research in another unexpected direction. An Iraq vet who works as a surgeon at D.C.’s Walter Reed Army Medical Center told Roach that wounded men usually have the same two questions after an explosion. “The first thing they ask is, ‘Where’s my buddy? Is he O.K.? … The second thing they say is, ‘Is my penis there?’”

Thanks to advanced technology and medical science, soldiers are surviving traumas that would have left them dead on the battlefield in past wars. And some of the injuries these men have to live with are very intimate.

While it may sound superficial to be concerned with your manhood over more deadly losses, losing your genitals can be more traumatic than losing a limb in some ways. You can get a prosthetic leg. You can get a wheelchair. But making up for the loss of that most personal of organs, the penis, is a bit more complicated. Luckily, the science is making big strides. The first U.S. penis transplant was performed in May 2016, and the patient, a cancer survivor, was released from the hospital less than a month later.

6. THE ARMY WOULD REALLY LIKE BOMB-PROOF UNDERWEAR.

Because of what one study called the “unprecedented” rate of genital injuries experienced by soldiers serving in Iraq and Afghanistan, the U.S. Army has been trying to develop underwear that could protect its soldiers’ crotches from harm. In 2010, a company called BCB debuted “Blast Boxers,” a product marketed as “bomb-proof underwear.” Unfortunately, no underwear is really bomb-proof. Even the Blast Boxers’s Kevlar can’t stop shards of metal blasting out of an IED. But it can stop dirt that blasts out of the ground when the bomb goes off, helping stave off infections in the resulting wounds. However, the Army has been researching the protective qualities of silk, which despite its reputation for delicacy, might be useful in the event of a bomb from below—it’s strong enough that bits of fiber won’t get embedded in the wound. However, the effort has run into some sourcing and development issues, and soldiers still don’t have their protective undies.

7. MARCHING IS EVEN WORSE THAN YOU’D THINK.

When in combat, soldiers typically carry around 95 pounds of body armor, batteries, weapons, and ammunition. As a result, soldiers sweat a ton, and researchers have quantified exactly how much. In the 1940s, military experiments found that carrying a 68-pound pack increased soldiers’ sweating by more than 20 fluid ounces per hour. Even when not in immediate combat, soldiers have a lot of weight on their soldiers. On a two-day loaded march, a soldier in Afghanistan would be expected to carry around 30 pounds. The weight modern soldiers have to bear on a regular basis can lead to abdominal strain and pelvic organ prolapse, according to a 2010 report of new medical challenges facing military hospitals.

8. DIGESTIVE ISSUES ARE ALMOST UNIVERSAL.

Poop is no joke on active duty. If you think traveler’s diarrhea is bad when you’re a tourist, imagine being in a combat zone. In one military survey of service members serving in Iraq and Afghanistan between 2003 and 2004, 32 percent of respondents had been hit with a violent case of diarrhea in a situation where they couldn’t get to a toilet. More than three-quarters of soldiers in Iraq and 54 percent in Afghanistan came down with diarrhea at some point, and 40 percent of those cases were so severe they required medical attention. As one Special Operator told Roach, “I have many stories where I’ve soiled my pants on missions. In Iraq, I’ve soiled my pants. In Afghanistan, I’ve soiled my pants.”

Obviously, military researchers are hard at work figuring out how to toughen up soldiers' stomachs for when they inevitably eat questionably sanitary meals in remote locations. In the meantime, soldiers improvise. For those who expect to be stuck in one spot for a long time—like in a hole surveilling a specific intersection—one air strike controller told Roach that a double layer of gallon Ziploc bags and kitty litter have to do the trick if a digestive emergency arises.

9. ON SUBMARINES, MISSILES ARE BUNKMATES.

On some submarines, space is at such a premium that crew members have to sleep with the missiles. That’s the case on the USS Tennessee, a sub that needed to add some bed space when technology upgrades required an increase in people on board. So people sleep in the missile compartment, wedged between Trident II nuclear missiles. Apparently, it’s a pretty peaceful place to get some shut-eye, as far as submarine sleeping quarters go. And that's particularly important, because ...

10. SUBMARINE-BASED SOLDIERS DON’T GET TO SLEEP MUCH.

For better or worse, the crew of subs like the USS Tennessee don’t get to spend much time napping between the missiles. On average, they get about four hours sleep a day. When they are scheduled to have some down time, their sleep is more often than not disrupted by fire drills, training, maintenance, and more. Junior crew members sleep even less than most, because they have to study for qualification, an extensive test of all the major systems across a submarine that every submariner has to pass. And as we all know, a lack of sleep can impair your judgment just as much as a few drinks would, making the military very, very interested in sleep research.

11. SUBS CARRY MORE PAPER THAN PEOPLE.

In 1987, Vice Admiral Joseph Metcalf III calculated just how much paperwork is involved with working on a submarine. According to his figures, a smaller warship has to carry 20 tons of technical manuals, forms, crew logs, and shelves. He campaigned for paperless ships, but subs still carry more pounds of paperwork than crew, according to Roach.

12. SAILBOATS ARE PRETTY DANGEROUS TO A SUBMARINE.

When submarines surface, it’s hazardous to anything else around, despite the use of technology like sonar. In 2001, a U.S. submarine came up right under a 191-foot-long, 499-ton Japanese trawler, ripping the ship in half and sinking it in just minutes. Subs navigate by sonar, but there are limits to what sonar can detect, which is why periscopes exist. If a ship’s engines are off or if it’s pointed right at the sub’s sonar array, it might go undetected. Furthermore, it doesn’t reflect distance quickly enough to let crew members know whether they should immediately dive or if the ship they’re trying to avoid is miles away. These limits to visibility and object detection might explain how in 2005, a $1 billion U.S. sub crashed into an underwater mountain at 40 miles per hour.

13. SOLDIERS REQUIRE LONGER NEEDLES THAN THE AVERAGE PERSON.

Soldiers tend to be weight-lifting, muscular fitness buffs, with an emphasis on the “buff.” Over the course of the 6000 autopsies on service members since 2004, doctors found that in about half of cases where men were treated in the field for a collapsed lung—involving a needle inserted into the chest to relieve pressure—the soldier’s pecs were so immense that the needle wasn’t long enough to reach past the layer of muscle into the lung. In response, the military began issuing longer needles for buff patients.

14. EVERY DECEASED SOLDIER GETS AN AUTOPSY, EVEN DOGS.

Currently, everyone in the military who dies while on duty gets an autopsy. The rule applies to service men and women, but it also applies to military dogs. While this wasn’t the case before the War on Terror, in 2004, the military decided to examine every service member in order to find new treatments and technologies for wartime injuries. These autopsies allow military doctors to see if the medical devices and techniques they’ve been using worked the way they were supposed to, and to determine if anything could have been done to save the fallen soldier.

15. MILITARY TECHNOLOGISTS HAVE SOME PRETTY OUT-THERE IDEAS.

“They think a lot of harebrained things are good ideas,” sleep researcher Greg Belenky, a retired colonel, told Roach of the Defense Advanced Research Projects Agency (DARPA), a military research arm perhaps best known among civilians for its annual robotics competition, where futuristic, top-of-the-line robots go head-to-head in tough tasks like walking on soft dirt without falling over. Besides all-terrain robots, DARPA hopes to create technology that would allow soldiers to stay awake for up to seven days without showing any adverse side effects, allowing those sleep-deprived submariners, for one, to work more efficiently to avoid deadly mistakes.

Roach tracked down a NATO symposium list of far-off, hypothetical technologies the military would love to develop to help its soldiers be at their best, including prosthetic limbs that would provide superhuman strength and eye implants that would allow soldiers to see in infrared and ultraviolet frequencies. “The wish list also included ‘surgically provided gills,’” Roach notes.