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This topic is inspired by recent discussions in the forum (ca October 2025).
GW Johnson wrote a short essay on the subject of how to build a sturdy landing platform with indigenous materials.
If he grants permission I will post it here.
The key concept is to build as the Romans did. The Roman roads are still in use after 2000 years, because the Romans knew how to build things to last.
We non-Roman humans can study their example.
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Post #3: GW Johnson on using Roman road building techniques to build landing platforms on the Moon and other off-Earth locations.
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This post is reserved for a short piece by GW Johnson on how to build sturdy landing platforms off Earth, using Roman methods.
As it happens, GW Johnson has experience building sturdy platforms on Earth, using Roman methods.
I'll post the text when permission arrives.
This email begins with discussion of the video of animation of a proposed landing on the Moon.
If I had to guess, I'd say most of the descent is made using the much-higher Isp Raptors, and they don't fire up those high side-mounted thrusters (and stop the Raptors) until right before touchdown. I think those high-mounted thrusters are Super Draco technology, which is the lower-Isp NTO-MMH technology. Same applies to ascent: get off the surface with the thrusters, then fire up the Raptors, and make the ascent with them.
As for hard pads, the regolith does not have much in the way of surface bearing pressure capability until it is filled by rocks of similar sizes that intimately touch each other. Once you have that, each applied load spreads out conically below the contact point, over ever-increasing areas, averaging ever-decreasing pressures, until it matches the bearing pressure of the non-rock-filled regolith below the excavation. That sets how deep you must excavate. The cones have something like a 30-45 degree half angle. If I was a "dirt work" CE, I'd know that angle by heart. I am not. I'd have to go look it up, in the right references for that kind of work. But it's something like that.
Once excavated, you go back with layers of rocks, with "sand" or "dust" packed really tight around them, but still touching each other. By "packed", I do indeed mean "pounded" to densify the fines. That's both power hammering, and being driven-over by really heavy machinery. You start with larger rocks at the bottom, and decrease the rock size as the layers work upward, back toward the original surface grade.
By the time you reach the surface grade, your last layer is but gravel, packed with fine dust (most of the time today, we use ground-up caliche limestone for that fine dust, it being mostly "slaked lime"). This is the technology that bears large surface pressures, not just spreading some tiles across the surface! You finish it off with your "baked tiles" that resist erosion from the hot rocket plumes, in lieu of reinforced concrete, which you don't have in vacuum conditions, because the water boils out of it before it can set, leaving a porous mess that is not strong at all. Besides, you have no unslaked lime powder on the moon or Mars, which chemistry is what makes the concrete set up. "Slaked lime" cooked in a furnace becomes "unslaked lime", which is very alkaline, and reactive with water. As far as we know, there is no limestone on the moon, and very little on Mars.
This kind of heavy load-bearing technology in soft soils has been known since the Romans. Their roads lasted, ours do not, because we don't excavate deep enough, trying to save money. You simply have to do it right for building foundations, especially in sandy or clay soils without closely adjacent bedrock. Or else your building will sink-in unevenly and eventually fall over. The road just buckles, but that kills no one. Buildings falling over does kill.
Another solution for that building foundation problem is piles deep in the dirt, preferably socketed into the bedrock, upon which you build a reinforced concrete beam grid for your foundation. You won't have that option on the moon or Mars because you have no way to make trustable concrete. You need sieved sand, size-graded gravel, unslaked lime (the so-called "cement"), and lots of water, and the water has to stay in the mix until set. It will not do that in vacuum. You also need the rebar, and the beam-tensioning rods and their end hardware, all steel, necessarily brought from Earth.
The only other solution is to cast-in-place a grid of reinforced concrete beams as your foundation, atop which you can pour a slab, if you like. The beams are larger than is usual for most slab foundations, and there are more to the grid than just the outer ringwall. I have actually successfully designed a couple of these. They are are more expensive, but the house never cracks, no matter how expansive the clay soil is. The foundation rides the expansion waves like a rigid boat hull. Most slab construction rides it like an air mattress. Concrete is NOT stiff, unless you deliberately make it stiff by doing the huge grid beam thing. This is not an option for the moon or Mars, because you have no concrete there.
So your only option for the moon or Mars is the "packed layers-of-rock dirtwork" I described. No concrete required, just whatever erosion-resistant tiles you can come up with for the final surface. The Romans used rock slabs from the right kind of layered limestone deposits for their surface tiles. It resisted all sizes of horses and wagons, until the wagons and chariots had steel-rimmed wheels. Those wore ruts in the limestone slabs. Slowly, but the ruts got worn. You can still see them today. They're about 2 horse-widths apart, which is where we got our 4ft / 8.5-inch railroad gauge width from.To do this kind of excavation and foundational-backfill work on the moon or Mars means that you must have surface mine sources for the right sizes of rocks and gravels, and you might well need a rock crusher (which is an utterly-huge piece of equipment) to make the right sizes of cobbles, pebbles, and gravels out of larger pieces. You need sieve-type size separators. Very-significant-size earth-moving equipment is required to do this work. It might fit inside an LST, but it will not fit in a few "Starships".
You either do this job right, or you don't do it at all. There is no in-between. Not in 2000 years has anybody ever been successful, trying to short-cut what the Romans learned to do with slave labor so long ago. The slave labor is why they could afford to do it "right" no matter what kind of country their roads crossed, and why they have lasted down to this very day.
I'm no "dirt work" CE, but I do understand the how and the why of why things need to be done this way. Few do. And I understand a lot about the histories of multiple technologies. I had to know about a whole lot of things, in order to be a success at new product development in the defense industry.
GW
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