 In the mid-1960s, before anything had soft-landed on the moon, but well into Apollo's development towards the lunar landing, NASA engineers started figuring out what a roving vehicle for extended surface exploration might look like. As engineers are wont to do, a team looked to nature for inspiration and found an unlikely muse in the mighty worm and the mighty centipede. Yep. Hello everyone, I'm Amy. This is The Vintage Space, my little corner of the internet where we look at all things mid-century that interest me. Obscure, unrealized elements of the space program is high on that list, and the lunar worm definitely fits that bill. But first, we need a little context. We don't think about it much from a modern standpoint, but in the early days of the space age no one knew what the lunar environment was like, and that was a problem when it came to planning for astronauts to land on and explore the surface. Planners only knew the basics, that the moon's environment included reduced gravity, a vacuum, extreme temperatures, and hazards like radiation and meteorites. But the surface itself was a mystery. No one knew whether the regolith was a thin layer or so thick it would be impossible to land without being buried in dust, or whether the surface would be strong enough to bear the weight of a rover, or even just the lander itself. The texture of the regolith was another potential problem it might be too hard to walk on. Some even wondered if the surface would be too uneven and pockmarked for any traditional vehicle to traverse the surface. This last point became important when planning for extended surface operations. If a crew was able to land on the moon, NASA would eventually want those astronauts to cover more ground to visit an array of locations on the surface, which would mean they would need a method of travel. I've looked into a few early proposals for one-man flyers and pressurized ATV type vehicles, but there was at the time the potential that no roving vehicle would actually work on the surface. Considering the array of unknowns, guidelines soon emerged to shape a round of studies into surface vehicles. The safest bet was for a vehicle to have no external moving parts, removing the risks of regolith or rocks affecting the system. A low footprint pressure was ideal, spreading as much of the vehicle's weight over as large a surface area as possible so it didn't risk sinking into or breaking through the lunar surface. There was also interest in a vehicle that could bridge crevices in case it turned out the surface was too cratered for anything else to move. NASA also needed something that could be folded up for easy transport to the lunar surface and unloaded without the need of ground support. The crew would have to do it all on their own and as a final wishlist item, NASA wanted something that could be beefed up to provide emergency radiation protection. NASA contracted Aeronutronic to explore vehicles that might work for extended surface exploration. In considering the wants and needs, namely the low pressure footprint and ability to scale terrain, Aeronutronic engineers found three things in nature that demonstrate all these principles. Worms inching along, centipedes using their length to bridge gaps, and snakes distributing their weight to cross a variety of different surfaces, including water. A series of vehicle concepts inspired by these animals formed the basis of the lunar worm study. The lunar worm Aeronutronic explored a focused on the bellows concept, specifically metal bellows. These elastic vessels can be compressed or expanded from internal or external pressures, and when that pressure is released, they return to their original shape. Managing or mimicking this extension contraction mode and coupling it with friction from the vehicle lying on the surface, engineers realized they could have a variety of vehicles move like worms, snakes or centipedes. The basic idea was to take a long, tubular, pressurized habitat and make it move across the surface mimicking these motions. The report identified a few ways the lunar worm could move across the surface, extension contraction, rib walking and traveling wave, each of which were explored for mobility, structural limitations and propulsive energy. The extension contraction bellows concept is one wherein the vehicle shortens and lengthens, propelling itself forward from the resulting asymmetry. The actual propulsion comes from the difference in friction between the advancing and retreating portions of the vehicle. Think of it like an inchworm. The rear part of the vehicle contracts towards the centerline, shortening the structure. Then the front end extends, pushing against the anchored back portion. Repeating these two motions allows the vehicle to inch forward one contraction expansion at a time. Anchoring the aft section of the vehicle during that extension phase was one challenge, especially if the vehicle was going up or down slope. It would need something to stop it from sliding out of control. The report suggested adding slanted cleats to the bottom of the vehicle that could dig into the soil. But this depended on the kind of soil. If it was too powdery, they might not get a good grip. A solution there was to use a hinged cleat set at the correct angle to dig into the surface with the right force. But perfecting the angle could mean the cleats wouldn't work well on all terrains, and because they would have to be external, they risked getting messy with regolith in the gears. Another challenge came from the whole of the vehicle's underside being on the surface. This brought a lot of drag. A simple solution with some kind of low friction coating on the underside, but any such solution would need more research into the actual surface environment. Rib walking got away from some of the issues of extension contraction. This vehicle used a series of ribs as the vehicle structure and a double acting bellows operated by a central crank to move those ribs 180 degrees out of phase with one another. The ribs essentially took steps across the surface. This method promised much faster movement. The speed of the ribs could speed up the ride, and the ribs meant fewer contact points with the surface, so less drag. It could even cross over small obstacles because the steps meant clearance from the surface. The downside was that fast ride was going to be a lot rougher. The last kind of movement was traveling wave. With either intermittent motion or a continual motion, the basic idea was to have sequential segments of the vehicle be in contact with the ground, generating propulsion in the process. It would be like a wave passing through the length of the vehicle with several wavelengths, making for a slow but smooth ride. The bellows creating the wave would be moved by a series of cranks rotating synchronously with a 15 degree phase difference, creating undulations. Research suggested this was actually the most versatile of the lunar warm concepts. This vehicle could move at higher speeds and over a variety of terrains, while still providing occupants with a smooth, comfortable ride. With the addition of some kind of feet on the vehicle, it could be more stable, more maneuverable, and better able to climb obstacles or bridge gaps. Without any external elements, it maintained NASA's desirable low pressure footprint. This vehicle even opened the doors for use on other planets or moons in the future. Aeronutronic considered a few applications for these lunar warm variants. It could be a lunar shelter that didn't move, a small unmanned vehicle, or a larger vehicle that could carry a crew for extended surface operations. Each kind was equally viable, though rib-walking promised the least comfort, so Aeronutronic identified it as best for unmanned vehicles, delivering cargo or supplies to some site ahead of a crew. Regardless of type, each vehicle could easily have a steering control system with the ability to turn, climb, and bridge gaps. In terms of habitats, Aeronutronic looked at a few possibilities. The first was a small habitat five feet across and seven feet long, able to keep a two-man crew alive for up to 30 days. Aeronutronic envisioned this as the vehicle that would transport astronauts from their landing site to a main shelter, making it a short-range, low-speed, low maneuverability vehicle, moving at about one-tenth of a mile per hour. The main benefit of this small iteration was it was actually small enough to be launched to the moon with Apollo hardware. It could also be powered by solar energy. Longer-term missions would need more support, something to cover longer distances and move faster. A robotic vehicle three feet in diameter and nine feet long would be an excellent support system for crews, carrying supplies at about one mile per hour for a range of about 10 miles. To really support crews, Aeronutronic looked at an extended-range roving habitat. This was the largest vehicle the contractor looked at, weighing up to 1,000 pounds and traveling at an average speed of about five miles per hour over a total range of about 100 miles. With a diameter of between six and 10 feet, it also offered the crew ample living and working quarters for the duration of a mission. The company determined the traveling wave was the most versatile method. Rib walking was problematic for humans and expansion contraction came with a very severe drag penalty. Of course, the study was limited because of how little was known about the lunar surface at the time. And this report reached NASA and was published in May of 1966, the same month Surveyor 1 made the first successful soft landing on the lunar surface. It revealed the moon was not coated in a prohibitively thick layer of dust. It could support the weight of a lander, and at least in the ocean of storms, the terrain was not unlike the deserts on Earth. The lunar worm concept never went further than studies. When it came time for astronauts to extend surface operations on later flights, they did it with the very Earth-like lunar rover. I hope you guys enjoyed this look into the extremely obscure lunar worm concept. That's gonna do it for me today, but before I go, I wanna remind you guys that both my books, Fighting for Space and Breaking the Chains of Gravity are available however you like to consume books. I've got links to both in the description below. I also want to give a very special thank you to my Patreon supporters and YouTube members. You guys honestly make it so that I'm able to continue making this content, so thank you so much. I would really not be able to do this without your support. I wanna thank each and every one of you for spending a little bit of your day with me today and I'll see you next time.