Quote from: lamontagne on 10/20/2016 01:24 ambuild a tunnel boring machine on MarsI think on Earth these are limited to fairly shallow grades; can't really dig straight down. But with Mars (or Moon) gravity? I wonder how quickly you could get well below the surface?And how sharply can they turn?
build a tunnel boring machine on Mars
Quote from: sdsds on 10/20/2016 05:39 amQuote from: lamontagne on 10/20/2016 01:24 ambuild a tunnel boring machine on Mars... how sharply can they turn?The're used for cars and trains, so very low angles. I expect they wouldn't turn. They would dig into a wide trench, be dragged sideways, and then start again in the opposite direction, making a whole series of parallel tunnels.
Quote from: lamontagne on 10/20/2016 01:24 ambuild a tunnel boring machine on Mars... how sharply can they turn?
TBMs can make turns, but they're not exactly the hairpin variety. By carefully applying more pressure on one side of the cutting head, the machines can change course by about 0.125 in./ft. "A typical radius for a turn is between 300 and 400 ft," says Turner. "But we build special TBMs if jobs call for tighter turns. The tightest radius we ever dug was a 90 turn in 75 ft in a South African gold mine.
Set one off and have it dig in a spiral of increasing radius; then cut across the spiral for linking passageways etc.
As far as stairs are concerned, would it be possible with 8 foot ceiling heights to just jump from one floor to the next?Matthew
Spiral cityfrom 200 to 500 m in radius, 20m dia tube. About 8 km long. At 500 m per month, less than 2 year to bore.about 160 000 m2.
Quote from: lamontagne on 10/21/2016 12:04 amSpiral cityfrom 200 to 500 m in radius, 20m dia tube. About 8 km long. At 500 m per month, less than 2 year to bore.about 160 000 m2.It would be nice and simple. Tunnel boring machines that size don't have the ability to do such narrow turns I believe but maybe they can design them.
Well since we're talking about tunnel boring machines again, it's time to go back to my favorite topic!!! https://forum.nasaspaceflight.com/index.php?topic=34667.msg1362562#msg1362562
Spiral city
Cross section of a 15m diameter tunnel showing a possible arrangement.There would need to be staircases every few length as well.
I like the large tunnel idea. It might be easier to implement initially by building large corrugated steel tubes in shallow trenches on the surface, then partially burying them for radiation protection. I'd add some Lexan skylights/windows/portholes for natural light.I prefer steel for this concept because:1) High strength to weight ratio2) Easy to prefabricate, ship, and weld together panels on site3) Can eventually be manufactured in very large quantities on Mars using byproducts of propellant manufacture and local iron oxide.4) High density can fully load out the volume-constrained ITS design and ship via slow transfer.A single 300t ITS cargo delivery would deliver 1100 prefabricated panels (2x6m and 275 kg each) to weld together a 300m length of 15m diameter tube, plus domed ends for some 60,000 m3 of pressurized interior space. 3mm thick corrugated panels could take more than 1 full atmosphere in tension at 15m and would be strong enough to support a fairly thick regolith covering even if depressurized. Interior panels could be welded directly to the skin and to each other to create additional structure with a wall-and-deck system.
Quote from: lamontagne on 10/21/2016 12:04 amSpiral cityI'd have another radial tunnel at 90 degrees to the first. Possibly others at intermediate angles; they don't all have to come right to the centre.Quote from: lamontagne on 10/21/2016 03:43 pmCross section of a 15m diameter tunnel showing a possible arrangement.There would need to be staircases every few length as well.Seems a lot of wasted volume. Why do you need three walkways?