Rail road on the moon aka massdriver, encompassing the whole moon along the equator. How high are the bridges? How deep are the tunnels?

Question

Mr. X strikes again with another moon plan and he was thinking - okay, it possible for a rover, on the Luna (earth's moon), to run on solar energy being permanently on the bright side with just 10mph speeds. Good but not that useful.

A railroad which is a future massdriver that circles the moon can be used to drive around the moon at a faster speed, so as it can be built into a massdriver to launch payloads from the moon, or to transfer energy from a bright side to a dark side by almost orbiting payload, a fast-moving (1.6km/s) one, a bit faster than a hyperloop one.

At any rate, that thing, which moves 1.6 km/s, for it to avoid some unrealistic forces acting on construction and the craft and the interface between the craft and railroad - it needs to move at an almost circular path, so the road has to be almost circular.

well, a known problem is that there are craters everywhere on the moon. So, the road has to go over some of those craters. Depth of craters vary, 500m - 4500m, so as the diameter of those is 5-60km big. Here is the wiki list of craters, with coordinates - list

So it needs to make bridges over these craters. Solutions may look like old timber railroad bridges, how it may look like there are examples link - build-out of local materials, no timber on the moon clearly.

The question is for those who have better skills, or tools, or brains.

How high those bridges will be? assuming Latitude is 0.

How high bridges will also depend on the decision to make - those craters have nasty rims/ridges, which may be a bit elevated above ground(no sure about that) rim/ridge thing - so if we build the road ring at some point ground 0 elevations it means we have to make tunnels and it may be a bit problematic - that drilling, rock breaking - hard tools required, not possible to speed up the process by breaking it in the small work areas(one can dig basically only from two sides), tunnel size affecting shuttle, etc. So it may make sense to dig less.

There were some elevation maps in form of pictures from NASA - https://svs.gsfc.nasa.gov/4720 , https://www.nasa.gov/feature/goddard/2019/cgi-moon-kit-as-a-form-of-visual-storytelling but I have no idea how to make it into numbers. But it feels the road has to have some average height over the ground from the get-go. Big moon wall timber-like bridge pier, as it looks like there is a significant height difference west-east - some bulge - and digging a 1000km is much worse than building 10000 km long, 1km height timber bridge pier.

the q

what is the average height and height from the top of the road to the bottom of craters it has to go through?

The question asked in a sense - how much to build, how much materials are needed, and all that and not in a sense - will it be possible to build a tall structure will it hold and such - if it is 10 km height - no problem at all, best scientists work for us.

• if there are reasons to adjust latitude it can be done.
• if I forgot something ask it or point out

Hm, reading this one https://pgda.gsfc.nasa.gov/products/50 seems I'm looking for something someting(substraction?) between geoid and elevation map, maybe. Hm, is it then just plain space.se question, hm.

Answer 1

The word you are looking for is: "topographic profile". As far as I'm aware no one did a study of this kind regarding the Moon equator. But you can see a small scale study about the Buys-Ballot crater here: http://lroc.sese.asu.edu/news/uploads/buys-ballot.png

On Google Moon you can roughly see an elevation map, but there's no height data (https://www.google.com/moon/) luckily right here we can see to which height each color correspond (https://moon.nasa.gov/resources/87/high-resolution-topographic-map-of-the-moon/)

So, with some photoshop magic, we can create a very rough height profile map for Luna's equator. It should not be very hard.

Answer 2

https://en.wikipedia.org/wiki/Mass_driver is a rail track with a specific purpose: to accelerate masses up to escape velocity.

The Moon's escape velocity is 2.38 km/s.

When one builds a railway track, one builds it where it's needed, not in some random place.

Now when the builders of the mass driver start building, they'll build a track long enough to accelerate things to 2.38 km/s, and no longer (maybe like 10% longer for wiggle-room). They won't build it wrapping the Equator because that's not what a mass driver is or does.

Now if you want a railroad just to transport things and people around, that's a different thing...