Quote from: lamontagne on 12/06/2018 03:57 pmTe actual strength of the liners would come from external hoops of carbon fiber wires, post tensionned, eventually replaced by locally produced steel. Longitudinal strength would be from rods set between the blocks.Why not extruded basalt? (And not just basalt fibre in a matrix. Extruded basalt rods and mesh are already used in building to reinforce concrete. Well, technically the concrete is the matrix, but you get what I mean. Half inch rods are not "fibre".)Quote from: lamontagne on 12/06/2018 03:57 pmthat is basically what National Geographic proposed in a recent issue.And that god-awful series they made.Quote from: Oersted on 12/06/2018 03:15 pmhow will you expand? With prefab habs? Building habs on the surface? Both methods are mass prohibitive. Even if you pile regolith on surface structures you still need to bring those structures in the first place.If you can't build an airtight shell, IMO you're not capable of settling Mars.A basic airtight shell is the equivalent of building a lean-to in a forest. It's the absolute technological minimum cost of entry if you expect to do more than short exploration-and-return.Quote from: Oersted on 12/06/2018 03:15 pmWhen tunnelling you only need machinery and energy (and the energy is there). The rest, i.e. the MASS LIMITED raw materials, are already there.Plus the consumables of the machines.If you want to build an airtight chamber in raw rock, the walls have to be non-permeable, that rules out soft rock, if you want it to self-support over fairly large areas, that also rules out soft-rock. So you're looking at hard granites. You are going to be consuming a surprising amount of parts to keep the, for example, road-headers running. If that mass is greater than the mass of a shell equivalent to that volume, you haven't saved anything.Likewise, is the mass of digging equipment necessary for cutting underground structures higher than the mass of equipment for making ISRU airtight shells?(This argument holds for my suggestion of cut'n'cover. You do need machines to work regolith anyway, but if you bury every hab, the rate of wear on those machines is much higher than if you're just levelling roads and landing-pads.)Quote from: Oersted on 12/06/2018 03:15 pmIt is pretty clear to me that it is the reason why Musk is actively exploring exponential improvements in tunneling technology.Perhaps, but it's worth noting that the savings he suggests came from reducing the diameter of the tunnel, by using electric "skateboards" instead of having to have full lanes for running cars and full height for trucks. Halve the diameter, quarter the volume dug. He hasn't actually changed tunnel boring the way he has launch costs, distributed power storage, and electric cars.
Te actual strength of the liners would come from external hoops of carbon fiber wires, post tensionned, eventually replaced by locally produced steel. Longitudinal strength would be from rods set between the blocks.
that is basically what National Geographic proposed in a recent issue.
how will you expand? With prefab habs? Building habs on the surface? Both methods are mass prohibitive. Even if you pile regolith on surface structures you still need to bring those structures in the first place.
When tunnelling you only need machinery and energy (and the energy is there). The rest, i.e. the MASS LIMITED raw materials, are already there.
It is pretty clear to me that it is the reason why Musk is actively exploring exponential improvements in tunneling technology.
Then there are the steep, smooth cliffs of the North Pole region. These are about two km tall (but I suspect actually 800m), slope is ~80 degrees:
Quote from: MickQ on 12/07/2018 08:55 amI'm wondering if a good place to tunnel would be the base of a five or six kilometre high cliff in Valles Marineris.It would mostly be loose rocks and soil for several hundred metres. The deeper you tunnel towards the actual base of the cliff, the higher the pressure over your head. By the time you are directly underneath the top of the cliff, you have the equivalent of two kilometres of Earth rock bearing down on you. At those depths, rock is basically plastic and tunnels are eventually squeezed shut.But Valles Marineris is not actually a cliff, more like a medium slope (20 or so degrees) in most places. The vertical scale is heavily exaggerated in the 3D flyarounds you see.
I'm wondering if a good place to tunnel would be the base of a five or six kilometre high cliff in Valles Marineris.
Only question: will the lava tube be in the right spot?
But the tunnels are lined with precast concrete blocks made on the surface and sequentially bolted into place. There's gravel and grouting between the tunnel wall and the blocks.
Here is my first element for my tunnel system: a Mars adapted drill rig, with a extended stay cabin and a large solar array, battery system for power.
(a way station being a solar array with a battery pack, a Supercharger station, in effect).
Quote from: lamontagne on 12/07/2018 01:55 pm(a way station being a solar array with a battery pack, a Supercharger station, in effect).This is clever. I occasionally hear a throw-away mention of "way stations" to extend range, I've yet to see anyone actually flesh out a minimum version of such a thing. Yours lends itself to standardisation.[This also gets back to battery-vs-ICE/fuel-cell question. It is vastly more efficient to have a solar array charge a battery and a battery power an electric drive, compared to having the solar array power a fuel/oxide-maker, then fuel an inefficient chemical-fuel generator. But in the former case, once that small battery is charged... that array is doing nothing. Are you better off having it trickle-generate and store fuel/oxygen over long periods, for use in bursts? The latter also gives you a handy emergency oxygen supply. Not suggesting that for your Mars-contest entry, not futurey enough for judges.]
eh, ICE has the same problem when the methane tanks are full.
Taking into account conversion inefficiencies and the need to carry LOx, and the difference between batteries and ICE is pretty small on Mars. And some kind of batteries actually exceed ICE.
Quote from: Robotbeat on 12/08/2018 01:23 pmTaking into account conversion inefficiencies and the need to carry LOx, and the difference between batteries and ICE is pretty small on Mars. And some kind of batteries actually exceed ICE.They will need to consider battery chemistries that can be produced from ISRU on Mars, which might have lower energy density than Li, but not need to be transported all the way from Earth. Solar energy capture will be a critical path and they need to do as much of it as possible in different modes.
Quote from: rakaydos on 12/08/2018 02:40 ameh, ICE has the same problem when the methane tanks are full.(And LOx tanks.) However, for an equivalent mass, methalox is denser than batteries. Moreso, for the way-station itself, tanks with the same mass as the entire battery-pack when transported empty to the site, can have store vastly, vastly more energy than the batteries. (Hence the solar arrays can work longer to fill those tanks.) And the tanks can be built locally at a much lower technology level of the settlement.
Quote from: Paul451 on 12/08/2018 02:30 amQuote from: lamontagne on 12/07/2018 01:55 pm(a way station being a solar array with a battery pack, a Supercharger station, in effect).This is clever. I occasionally hear a throw-away mention of "way stations" to extend range, I've yet to see anyone actually flesh out a minimum version of such a thing. Yours lends itself to standardisation.[This also gets back to battery-vs-ICE/fuel-cell question. It is vastly more efficient to have a solar array charge a battery and a battery power an electric drive, compared to having the solar array power a fuel/oxide-maker, then fuel an inefficient chemical-fuel generator. But in the former case, once that small battery is charged... that array is doing nothing. Are you better off having it trickle-generate and store fuel/oxygen over long periods, for use in bursts? The latter also gives you a handy emergency oxygen supply. Not suggesting that for your Mars-contest entry, not futurey enough for judges.]eh, ICE has the same problem when the methane tanks are full.On the other hand, though it risks complicating the design and is climate dependant, what about a atmospheric water condensor hooked up to an ice cube mechine and a shadecloth? The idea being to store water outside of a tank, for the next rover to come by and take back to the fuel plant.it'll be lossy as all hell, but since you only run it when the batteries are full, lossy with unlimited storage beats standing around doing nothing.
Quote from: lamontagne on 12/07/2018 01:55 pmHere is my first element for my tunnel system: a Mars adapted drill rig, with a extended stay cabin and a large solar array, battery system for power.On Mars I'd expect the wheels to be more spread out and with greater ground clearance.And particularly with independent-wheel electric drives, it's mechanically simpler than trying to run a single power-source through multiple axles, even allowing independent all-wheel steering. You might end up with a modular chassis-drive-steer components, like the EFT-truck concept. (Although with more clearance, you need to travel over raw terrain. Unless the very first vehicle is a tracked dozer-grader. [edit: Turns out they have adjustable lift, tons of clearance.]) Connect two drive modules and it's a 4x4 rover chassis, two and a cabin and it's a manned rover. A third and it's a general-purpose 6x6 utility chassis. Five and it's a loader. 10-15 and it's a multi-articulated long distance transport. Oops, did your truck break? Just grab three modules off the long-hauler and swap over your cabin and service units and go back to working while we salvage what we can off the old parts.[It's the lots-of-standard-units-because-it's-electric concept I'm interested in. (Or hybrid-electric in EFT's case.)]Quote from: lamontagne on 12/07/2018 01:55 pm(a way station being a solar array with a battery pack, a Supercharger station, in effect).This is clever. I occasionally hear a throw-away mention of "way stations" to extend range, I've yet to see anyone actually flesh out a minimum version of such a thing. Yours lends itself to standardisation.[This also gets back to battery-vs-ICE/fuel-cell question. It is vastly more efficient to have a solar array charge a battery and a battery power an electric drive, compared to having the solar array power a fuel/oxide-maker, then fuel an inefficient chemical-fuel generator. But in the former case, once that small battery is charged... that array is doing nothing. Are you better off having it trickle-generate and store fuel/oxygen over long periods, for use in bursts? The latter also gives you a handy emergency oxygen supply. Not suggesting that for your Mars-contest entry, not futurey enough for judges.]
>These vehicles are concepts?>
Quote from: Paul451 on 12/08/2018 02:30 amQuote from: lamontagne on 12/07/2018 01:55 pmHere is my first element for my tunnel system: a Mars adapted drill rig, with a extended stay cabin and a large solar array, battery system for power.On Mars I'd expect the wheels to be more spread out and with greater ground clearance.And particularly with independent-wheel electric drives, it's mechanically simpler than trying to run a single power-source through multiple axles, even allowing independent all-wheel steering. You might end up with a modular chassis-drive-steer components, like the EFT-truck concept. (Although with more clearance, you need to travel over raw terrain. Unless the very first vehicle is a tracked dozer-grader. [edit: Turns out they have adjustable lift, tons of clearance.]) Connect two drive modules and it's a 4x4 rover chassis, two and a cabin and it's a manned rover. A third and it's a general-purpose 6x6 utility chassis. Five and it's a loader. 10-15 and it's a multi-articulated long distance transport. Oops, did your truck break? Just grab three modules off the long-hauler and swap over your cabin and service units and go back to working while we salvage what we can off the old parts.[It's the lots-of-standard-units-because-it's-electric concept I'm interested in. (Or hybrid-electric in EFT's case.)]Quote from: lamontagne on 12/07/2018 01:55 pm(a way station being a solar array with a battery pack, a Supercharger station, in effect).This is clever. I occasionally hear a throw-away mention of "way stations" to extend range, I've yet to see anyone actually flesh out a minimum version of such a thing. Yours lends itself to standardisation.[This also gets back to battery-vs-ICE/fuel-cell question. It is vastly more efficient to have a solar array charge a battery and a battery power an electric drive, compared to having the solar array power a fuel/oxide-maker, then fuel an inefficient chemical-fuel generator. But in the former case, once that small battery is charged... that array is doing nothing. Are you better off having it trickle-generate and store fuel/oxygen over long periods, for use in bursts? The latter also gives you a handy emergency oxygen supply. Not suggesting that for your Mars-contest entry, not futurey enough for judges.]These vehicles are concepts?I think it would be great to have the way stations as storage places for water and oxygen. Perhaps if they can be arranged in a loop it might make sense to have 'harvesters' move from one way station to the next. Then the way stations would serve a dual purpose. There may not be a specific advantage to having all of the production equipment in a single spot, if we have distributed solar, might as well spread it over a wide are.