Heidi Elmendorf, a biologist at Georgetown University, studies the parasite giardia, and to do so has to re-create our gut environment in the lab.
During spring break I discovered rock climbing, thanks to Georgetown’s Outdoor Education and a few extremely dedicated guides. At one point during one of my first ventures, I was about 30 feet in the air, suspended by a climbing rope that was tied into my harness and anchored by karabiners clipped into bolted hangers in the side of Pilot Mountain in North Carolina. My adventure probably sounds tame to any experienced climber, but as a newbie I have to say I was pretty nervous. How on earth was a mere rope supposed to keep me from plummeting to my death?
Fortunately, I made it back to Georgetown alive, and I spent the week researching just what makes climbing rope and other strong fabrics so reliable.
Climbing ropes have a tough job: They have to be light enough to carry and pliable enough to be knotted securely — no slippage — but you want to make sure you can untie yourself easily at the end of your adventure. More importantly, they need to support climbers while they hang in their harnesses, but they also have to be able to absorb the force of falling without injuring the climber. It’s a delicate balance of elasticity and durability.
There are two types of rope material used to make climbing gear, depending on the activity. Top-rope, a rope at the top of the climb between the climber and the belayer; lead climbing, in which the climber hooks into various pre-established points along the wall; and “trad” climbing, in which the climber hooks herself into various points that she creates herself along the wall. Each of these methods requires dynamic rope, which has that elastic property. Conversely, the material used to construct harnesses is static: They can hold a lot more, but won’t absorb any of the falling force. Static ropes are used in other contexts for operations that need a consistent rope strength, like pulling materials for ships.
A lot of rope strength comes down to how it’s arranged. A German company called Edelrid was the first to recognize the potential for super-strong synthetic rope. In 1953, Edelrid scientists coined the term “kernmantle rope,” which literally translates to “core jacket.” Kermantle ropes consist of a braided core that provides strength and an external covering which protects the core from abrasion. They consist of six or seven three- and four-stranded ropes braided together again to reinforce strengths. Additionally, kernmantle ropes have high ultimate tensile strengths, meaning the force it takes to break them greatly exceeds their weight. Typically, a dynamic, 11-millimeter, kernmantle nylon rope at 78 grams per meter can withstand forces of up to 2,000 pounds; static ropes of the same size can take up to 7,650 pounds.
And what is it that makes these ropes so reliable? Nylon.
You’ve probably heard of nylon in the context of panty hose, and it’s true: When the synthetic amide polymer was first put on the market in the late 1930s, it was marketed toward women. Wallace Carothers, a DuPont scientist, invented the first nylon in the early 1930s; it went to market in 1938. Nylon actually refers to any long chain molecule of a compound with at least one double-bonded oxygen atom and a nitrogen atom; if you’ve taken a general chemistry course, you’ve probably made it in a lab. Climbing rope uses a nylon called nylon 6,6, which refers to the places along the polymer chain where these notable bonds occur.
Nylon isn’t the only chemical used for climbing safety. There’s also an ultra-high molecular weight polyurethe, more commonly known by the leading commercial brand name Dyneema. It’s basically another type of polymer with an extremely high molecular weight between 2 and 6 million atomic mass units; this long molecule is heavy in atomic terms, which means it can take a serious weight load. In fact, Dyneema rope has the highest impact strength of any malleable plastic, and it is 15 times more resistant to abrasions than steel. Since the 1950s, climbers have taken advantage of Dyneema to construct harnesses and other static force absorbing climbing gear.
What have we learned from this? Despite my paralyzing fear I faced on my first day, climbing rope is probably one of the safest things out there, thanks to a little chemistry and physics. Of course, there are many other factors at play when it comes to any activity (say, the intelligence of others with you), but if you’re going to get into climbing with Outdoor Ed — which I highly recommend — you definitely don’t have to be afraid of falling.
This column originally appeared in The Hoya