- Status Report
- Feb 1, 2023
Deep/Underwater Cave Environments: Comments by William Stone at the First NASA Risk and Exploration Symposium
I’ve come from a rather unusual background in that I came up through engineering school wanting to be an astronaut, but had the good fortune of discovering that there were remaining places to be explored here on Earth in the meantime. As a teenager, I watched a couple of these guys who talked here this morning walk on the Moon. They were my heroes, and it was the U.S. space program that was directly responsible for my going out and getting a Ph.D. in engineering and wanting to work in space. In the process of trying to get into the Astronaut Corps at various times, I have also had the privilege of being involved with a large number of expeditionary projects dealing with things that go down into the Earth as opposed to things that go up. I added it up a little while ago. Over the last 26 years, I’ve spent 7 1/2 years in the field on expeditions, of which 353 days were below 1,000 meters deep underground, based from subterranean camps. So, I’m either a troglodyte or somebody who’s looking for planetary exploration and hasn’t been able to get off this pile of rock yet.
What I am going to do here this afternoon is to rapidly take you to three of the most remote places that humans have ever reached inside this planet. This is serious business. It is more serious, in my opinion, than high altitude mountaineering, because of the multidisciplinary nature and the remoteness. I don’t consider expeditionary deep caving as something you do for excitement. You do it because it’s an opportunity to explore one of the last true frontiers on this planet. The classic distinction on this subject came from arctic explorer Vilhjalmar Steffanson, who once spent five years working solo north of the Arctic Circle. Interviewed about this one time, the reporter asked [Steffanson], “Well, you’re an adventurer, aren’t you?” He said, “Son, adventure is what happens when exploration goes wrong.”
I have had that motto emblazoned upon my heart in letters of gold ever since. You do not get Brownie points for having your name on a tombstone. You have to come back. With that in mind, I have actually taken a lot of cues from how NASA trains its astronauts when preparing for, and staffing, expeditions. In the subterranean world, where we are about to go, it is a gloves-off environment. The exploration front is now getting to the stage where it is so remote and so difficult to reach that no matter what technology we have at our disposal, and no matter how Olympically-trained and fit the people are who are involved with it, we still get stopped. Every time you go for four or five months in the field, if you’re lucky, you’re a kilometer or two deeper into the planet. I am going to try to give you an idea here just what this world is like. I’m going to show here what would be the equivalent of summitting Everest and K2, but it’s all going to be in one continuous trip proceeding down, in order to give you a sequential feel for the logistics and remoteness.
Rising out of the southeastern area of southern Mexico is the Huautla plateau. It jumps straight up about 2,100 meters. The top of it is cratered with gigantic sinkholes. The water that rains on this area for 500 square kilometers all goes internally and, in the process of doing that, it creates some pretty substantially-sized voids.
About 50 kilometers away to the south and a kilometer higher in elevation is Cueva Cheve. This was only discovered in 1986. This underscores the still unknown extent of this last frontier: Cueva Cheve was not even known to the modern world until 1986–just 18 years ago. The endeavors we’re talking about require a lot of technology, starting off with the fact that you’re going down. You don’t just walk down that depth. There are three kilometers of specialized rope that are used to rig over 107 drops and traverses going down into this cave.
Typical vertical drops on some of these things can reach distances of 160 meters straight down. That would be about one and a half times the height of the Vehicle Assembly Building, for those who are here from Kennedy Space Center. A lot of times they’re a little bit shorter, but they almost always have water accompanying them. The deeper you go, the more water you collect. The tributaries each add a little bit in until, finally, you’re dealing with quite a serious flow. You’re rigging lines on the walls to keep out of that, usually. This is life on rope. You’re usually carrying around a 25-kilogram pack, which has the supplies that you’re bringing. This is very much an inverse variant to the siege tactics that you see used on high altitude mountains where you’re building Camp 1, Camp 2, Camp 3, and you start off with a pyramid of 50 people. Sometimes, we’ve had as many as 150, but 50 is a typical number for a trip for four to five months. That works out to be a good number to work with–you have depth of personnel to handle emergencies in situ. We’ve generally considered that a team of 12 to 18 is about the minimum you would want for safety and skill redundancy. And the further down you go, you’re adding more tributaries until, finally, you’re into rivers by the time you get to about the 800-meter level. This would be a little over a half a mile deep in English units. I know nobody around here works in English units . . . except when you’re designing planetary craft going to Mars. [Laughter]
One of the things that we’ve had to deal with is the fact that we are constantly running up against the limits of human endurance. Typically, if you go on a marathon exploration trip, you can stay up for 24, 28, maybe 30 hours, and, after that, if you come back to base camp on the surface, you’re out of commission for two to three days while you’re recovering. You can’t do that underground, because even when you are resting–say at an underground camp–you are consuming supplies, which are finite and paid for at great price of effort. If you want to move efficiently, your people have to be roughly 16 hours from anywhere that they have to go. And, so, we begin to establish a series of camps. I want to dispel the notion that a lot of people have that these places are claustrophobic. In reality, many chambers and tunnels in southern Mexico–owing to the significant tropical yearly rainfall–are so big you can’t even see the ceilings or the walls. It really is like being on the dark side of the Moon. These are team endeavors. None of your specialized personnel– divers, climbers, surveyors–get to the “front” without riding on the sweat of a substantial support team. Like high altitude mountaineers, cavers frequently refer to such support crew staff as “sherpas.”
Again, when I think of an expedition–and this is a sticking point with me and it may be with others–there are a couple of holy words in the vocabulary of true explorers. And one of those is the term “expedition.” To me, this is an endeavor of 20 or more people being out in the field for four-plus months. That’s a serious distinction. Anything short of that is what I would refer to as a recon mission. And, so, in the case I’m discussing here, you’re on site for four or five months, and people are working daily. It is not uncommon during the early stages of an expedition for the lead rigging team to get caught between known camps, and, so, setting a bivouac is something you plan for as you move in. Generally, it is for logistics reasons that you don’t get as far as you would like–for example, you might not have been able to carry enough rope to continue rigging.
Well, the reinforcement crew comes in the next day with another kilometer of rope and off you go. And then that support crew retreats to the previous camp behind them and the rigging team presses onward. And so it goes on down, until you are now roughly four days traveling distance from the nearest entrance. So, when you get to a place like this, you begin to think about the fact that you’re pretty remote, and there really isn’t going to be any rescue, except from the people who are with you, particularly if it’s something that requires urgent response. If you can get a person back to a camp and stabilize a broken leg or something like that, you can always send out for assistance. But there are places where even that is not possible, particularly when working beyond flooded, underwater tunnels.
The most remote place that we’ve been so far is at the current limit of exploration in Cueva Cheve. When you get down to a distance of approximately 8 1/2 kilometers inside and at a depth of 1,360 meters, you’re moving through river canyons, and you keep thinking that, well, this is just going to keep going down like this. But the problem is that caves are always quirky in terms of geology. All it takes is a slight counterfold in the limestone strata, and that river that was boiling is now static, placid, and leading you into tunnels that are completely waterfilled to the roof for substantial distances, before they usually rise back up into air-filled sections of cave. They used to refer to these places as terminal siphons. In fact, that’s the name of a rock band I’m in, so you’ll hear us touring someday.
So, you get down to a place like this and here you are, you’re roughly 1,360 meters vertically down and 8 kilometers in. Everything down here is paid for preciously by the people who transported this down. You’re living on ropes for days to get this here, so you have to be very careful about what you bring. At this point, those in the lead–in this case, trained cave divers–have this enormous pressure on them to perform. And I’m sure that everybody who’s flown on a rocket knows this same feeling. Here’s 50 or 100 people who have given of their time, of their lives, of their sweat for four months. That’s not counting, by the way, in the case of many of these, that we have spent two to four months rehearsing with those same teams over the preceding one or two years. When you get to these places where the tunnels are full of water, now you’re into another level of discipline where you have to be aware of the fact that, number one, you’re going to be using portable life equipment–what astronauts refer to as PLSS [Portable Life Support System] units for EVA [extravehicular activity]. And that’s the way I think of this. I think of this as EVA. And when you do that, you have to be thinking a couple of things. Number one is that anything can go wrong at any time, and so the best way to deal with this is to believe that this place is actively out to get you. When you think that way, you start making checklists ahead of time. In fact, we have them all laminated on waterproof paper. Not only before you go in, but after you come back out. It’s the equivalent of pre-flight and post flight checklists.
But there’s more to this. I’m going to say one thing here, and then I’ll come back to another side of it. We’ve been talking about issues for reducing risk, one of them being making our equipment “bombproof.” That’s a bit tough when you look at the places that you have to go through to get these items or the equipment that these people have down here. And the other issue is redundancy. But before I get to that, there’s this whole issue of peer pressure that is on you. You have to be ready at any second on one of these things that, if you get 50 feet inside this underwater tunnel and you don’t like how you feel, you abort. That’s a cardinal rule.
Somebody was asking me recently how many people do I know on expeditions that have died? And I really never thought much about it until I started adding it up. Over the last 18 years, I’ve lost 16 good friends. People that I’ve climbed with, worked with on expeditions, people who were very qualified.
The reason they’re not here right now is because they went a little too far–they didn’t abort when they should have, they didn’t stop and say, “Wait a minute. There’s a stack of things that are going wrong here.” Nothing ever happens in one blow. Jim Lovell pointed that out this morning. But a string of little events occurs–you start going down there and you get tired. You get tired and you say, “Ah, I don’t need to have this extra little piece of safety line here.” And, “Oh, well, I don’t need to check this other piece of equipment I have for descending a rope.” Pretty soon, things start to add up, and you don’t have that safety on there and when you sit down, one of those carabiners is unlocked and it comes unclipped, and there you are with 25 kilos hanging below you, and you’re hanging on the rope by one hand. You know, that kind of stuff happens. So, you have to get religious in your discipline about how you deal with the technology. This is high technology exploration that’s going on down here. More serious than a typical EVA mission outside the Shuttle.
The Portable Life Support System we use is all fully-closed-cycle equipment. There is no air in this system. It’s all helium-oxygen running at about 6,000-psi in carbon-carbon tanks. The range on this particular rig is about eight hours and depth-independent. We developed this particular PLSS because we didn’t know how far we were going to have to explore underwater. Sometimes when you get to these locations, there is no dry land, and so you’re living in hammocks strung from rock bolts above the water and hoping that you’re high enough that, in case there’s a flood, you’re not going to get washed away. That’s the world you live in when you’re down there.
In the bottom of this system you’re doing 600 meters–that’s roughly a half a mile–of diving, starting at the 1360 meter level. When we got to the other side, we established a camp. We were over there for a week and explored another three-and-a-half kilometers beyond the underwater section. These places represent the frontier right now. No one has been able to organize an expedition since to go further. In the case of Huautla, it has been 10 years since anyone visited that location; in Cheve, it was 2003, and it’s unlikely that a return there will be fielded before 2007, although we do have that one in the planning stages already. Neither of these places are finished. They are beckoning. They are wide open. And, yet, we can’t get the tactical logistics together or the team, because those people all have to be not only vertical trained, they have to be comfortable with where they are in a remote environment, and they have to be able to dive at the same time as well as climb. You start putting all these things together, all these various task loadings, and, pretty soon, the filters get pretty serious. There are not many people in the world who have all these skills.
This is the kind of thing that we are going to have to think about. Who are you going to put on the Moon? What kind of expeditionary-qualified people are you going to put on the Moon? Are you going to live together for a year up there? I mean, the psychological aspects are one thing, but the multidisciplinary training is going to be phenomenal.
If you get away from this logistical problem that we have of getting stuff down to 1,500 meters underground, and you can bring things in on tractor trailers, the whole ball game changes. One of the great natural wonders of the world, just south of Tallahassee, Florida, is a place called Wakulla Springs. Up until 1987, it was basically unexplored. You could look at the entrance from glass-bottomed boats, but nobody had seen much more than 100 meters inside on scuba. And we had an opportunity to go there with National Geographic in ’87. But it was in ’99 that things really got high tech. This project was a good example of how exploration need drove equipment development. Many pieces of technology we used did not exist prior to 1999. We built all this-a floating, saturation diving, recovery system; 20-kilometer-range propulsion vehicles; dual-redundant, closed-cycle PLSS backpacks; and 3-D, automated mapping systems–on a two year schedule, once we got the go-ahead from National Geographic and corporate patrons. We had a dual closed-cycle PLSS; six onboard computers running this thing; twin head-up displays; 18-hours range. There is no EVA system in use by NASA that would meet this standard, and I’ll tell you why. When we get down there, we’re going to be doing missions to distances of about 4 1/2 kilometers from the entrance at 100 meters underwater depth. When you’re out there, you are two and a half hours one-way travel time from the nearest egress point. By comparison, if you’re on a Shuttle mission or a station mission right now, and you have a problem with your suit, whether it’s an Orlan or an ILC Dover suit, you’ve got roughly 10 to 15 minutes, maybe 30 minutes in open circuit mode at best, to get back to the hatch. Here you don’t have that luxury. You are two and a half hours out, and you’ve got to figure out how you can do it.
It’s important to point out that everybody here was in a situation where, no matter where they were on that trajectory, they had an abort scenario. The maximum mission duration by pre-agreement among the teams was 10 kilometers penetration. And you had a factor of four to one safety margin to get yourself back. Everybody who was doing these would rehearse each mission beforehand for upwards of 12 hours (in the spring basin), and have people come in and tell them, for example, that all of their vehicles were dead, they had to transfer and get towed out by one of their partners. And then you’d tell them, for example, that half of their life support system was gone and they’d have to continue out on that. So you’re continuously rehearsing all the various abort scenarios. In that sense, it’s no different than training for a space mission. But here, we explicitly included abort capability for every phase of the mission. That isn’t true of space flight currently.
A typical mission is all about collection of information about what the frontier is. If you’re an explorer, you should be out there trying to collect that data, just like Steffanson said, and get back safely with it.
We built for this project a gadget–known as the “Digital Wall Mapper”– with a very high-grade, inertial guidance unit, phased array sonar, and about eight computers. And it’s imaging the wall as you drive through, to build a three-dimensional map of the aquifer. The person in back is the safety diver. Their job is to make sure that when this person is driving this monstrosity, that if they do something wrong, they’re going to come up and help them out.
Typically, we would have a support crew follow people in to a depth of about 80 meters. Perhaps 150 meters into the cave the crew is running on helium oxygen, and they’ll have 18 hours supply down there. The people on top have got the biggest sport diving cylinders in the business, and they’re dumping out about a thousand dollars worth of helium-oxygen on that support mission just because of the fact that they’re wasting it away, breathing it into the water column.
And then off you go for approximately the next five and a half hours, with a typical run down here to 100 meters depth, and then you’re back. Now you can’t come straight out, as somebody like Mike Gernhardt or anybody will tell you who has done EVA. You have a decompression issue, a very serious one. In fact when you’re five hours down at 100 meters, you’re almost saturated. At 60 meters down, we had a string of closed circuit cameras following people out. They had flashcards so they could tell if everything was OK, or they needed supplies from down there.
When they reached a certain stage–the completion of their 30-meter decompression stop–six support divers would drop out of the sky, like something out of a James Bond movie, and come down and take away their closed-cycle unit, give them a regulator, and let them switch up into a pressurized, personnel transfer capsule. They would then be transferred up to the top and into what we call a mini-saturation system, where they would spend the next 12 hours. Total mission duration, about 22 to 24 hours. We did this everyday for three days, took a day off for maintenance, and then did it again, for three months while we were down there. No issues with safety on that entire project with any of the mission crews. Ten million data points were gathered on this trip to build the world’s first three-dimensional cave map. So, in our case it’s not only a desire to be out on the frontier, but it’s also about bringing the data back home.