Author Topic: Elon The Boring Company  (Read 85023 times)

Offline go4mars

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Re: Elon The Boring Company
« Reply #260 on: 04/19/2017 06:15 AM »
Now, of course, there could be "hotspots" where it comes closer to the surface, but still, Mars is the last place I'd want to focus on geothermal power...

Heck, now that I think about it, how would you even work with drilling fluids on Mars?  They're going to be constantly trying to boil off and freeze your well.  And as they boil off they'll be depositing the suspended slurry - on everything that they touch.
If you believe hot spots are likely to be found by satellite, that geysir's can happen with CO2 phase change from solid to gas installed in areas appropriate for expansion captured through turbines in modest depth wells, that the same process will bring an easier supply of hydrogen and hydrosilicons and possibly metals from within the porosity than electrolysis at surface (additional resources), that cascading low temperature organic rankine including fluids that freeze well below zero is underappreciated, and that the operation doesn't necessitate huge casing anything like a typical high temp Iceland geothermal well, that drilling fluid is mostly CO2 and argon or atmospherically centrifuged argon run through a hammer drill, then it is probably more feasible than many other energy ideas for Mars.  In my opinion.

Also, if the least expensive way to store fluids and gases is underground in porosity rather than tanks at surface, then some drilling equipment will be needed anyway.


Another thought for this thread - pressure at the bottom of Hellas basin is insufficient for growing crops. 
I would rather invest in a deep tunnel where a thick air column, perhaps 10-15 km below Hellas can grow crops without needing to pressurize mechanically or warm them, than only surface greenhouses.  Alternatively, make it shallower for logistical reasons but deep enough to easily pressure seal sufficient for crop production. Multi-purpose tunnels.
« Last Edit: 04/19/2017 06:24 AM by go4mars »
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Offline wes_wilson

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Re: Elon The Boring Company
« Reply #261 on: 04/19/2017 01:37 PM »
[...] I would rather invest in a deep tunnel where a thick air column, perhaps 10-15 km below Hellas can grow crops without needing to pressurize mechanically or warm them, than only surface greenhouses.  [...]

This.  If you're going to take a tunnel boring machine to Mars and live in tunnels, then drive two shafts down deep enough and build the entire colony at a depth sufficient to maintain pressure.  Eliminates all the airlock issues, decompression issues, pressure is passively stable, temperature is better, etc... 

If you're going to tunnel, there are so many benefits to going deep. 
@SpaceX "When can I buy my ticket to Mars?"

Online kenny008

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Re: Elon The Boring Company
« Reply #262 on: 04/19/2017 02:26 PM »
Are you guys discussing things that can be accomplished this century, or just in some distant future?
Sorry for the hyperbole, but 15 km deep shafts are not something I think we'd be looking at in the near future, and certainly not in a near-term colony plan. 
The deepest borehole on earth, with all of our local resources, is a little over 12 km deep, and about 20 cm across.  I like reading KSR as much as the next sci-fi fanatic, but we are probably not quite ready to start boring man- or -vehicle sized boreholes on another planet to 15 km.  YMMV

Offline wes_wilson

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Re: Elon The Boring Company
« Reply #263 on: 04/19/2017 10:56 PM »
Are you guys discussing things that can be accomplished this century, or just in some distant future?
Sorry for the hyperbole, but 15 km deep shafts are not something I think we'd be looking at in the near future, and certainly not in a near-term colony plan. 
The deepest borehole on earth, with all of our local resources, is a little over 12 km deep, and about 20 cm across.  I like reading KSR as much as the next sci-fi fanatic, but we are probably not quite ready to start boring man- or -vehicle sized boreholes on another planet to 15 km.  YMMV

You're mixing boreholes with tunnels or mines which are very different things.  +15Km long tunnels and mines are absolutely everywhere but we don't slant them deep.  In fact there are mines with well over 500Km of tunnels so running one down 15Km is a simple choice.  Here, we choose not to slant deep because of rapidly increasing temperature with depth making them uninhabitable at depths of 2km or less. 

If you're already signed up to ship a tunnel boring machine to mars (as this thread has done) there's nothing futuristic about running your tunnels deep instead of horizontal.  It's merely a planning decision.



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Offline guckyfan

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Re: Elon The Boring Company
« Reply #264 on: 04/20/2017 06:48 AM »
If you're already signed up to ship a tunnel boring machine to mars (as this thread has done) there's nothing futuristic about running your tunnels deep instead of horizontal.  It's merely a planning decision.

I fully agree. Though going vertical will need a different machine. Tunnel boring machines go mostly horizontal.

Offline DanielW

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Re: Elon The Boring Company
« Reply #265 on: 04/20/2017 03:39 PM »
I don't think you are going to be able to build a 15km elevator even in Mars gravity, so you have to do a gradient. You would not want much beyond a 10% grade. Now you have a 150km tunnel. Not impossible, but not fun or easy either. That is a long way to remove rock.

But I think the radiation protection would be sufficient. If Mars is not susceptible to Radon leaks anyway.

Offline RoboGoofers

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Re: Elon The Boring Company
« Reply #266 on: 04/20/2017 03:53 PM »
I don't think you are going to be able to build a 15km elevator even in Mars gravity, so you have to do a gradient. You would not want much beyond a 10% grade. Now you have a 150km tunnel. Not impossible, but not fun or easy either. That is a long way to remove rock.

But I think the radiation protection would be sufficient. If Mars is not susceptible to Radon leaks anyway.
It could be done in flights, so each is only 10 km long. It's still a lot of rock to remove. you have to move all of it to the outside, after all. So you'll need a lot of dump trucks so you don't have to constantly stop the boring to wait for the trucks to drive out and back. or you'd need tens of km of conveyor belts.

If I was going, I'd gladly deal with airlocks and radiation so I didn't have to live in a hole 15 km down.
« Last Edit: 04/20/2017 03:54 PM by RoboGoofers »

Offline go4mars

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Re: Elon The Boring Company
« Reply #267 on: 04/21/2017 04:47 AM »
Are you guys discussing things that can be accomplished this century, or just in some distant future? 
The deepest borehole on earth, with all of our local resources, is a little over 12 km deep, and about 20 cm across.
This century. 
Drilling to 12 km on Mars is only equivalent to a lithostatic gradient of roughly a 4 km deep situation Earth (less gravity is helpful).  I also very strongly believe that myself, or someone else will begin drilling much deeper wells on Earth than 12 km within the next 10 years.  There is absurdly quaint technology drilling todays wells.  Absurd.  The deep liquid spun hammer drilling at Espoo is a very small beginning.  The next will be combustion (plasma) drilling.  For those about to scoff, yes I have calculated the required energy and no I am not daunted.
Next, the main difference between extreme high speed drilling and extreme tunnelling is diameter and direction.
I think Elon will figure it out with a free body diagram mindset and a few billion dollars. 

Better tunnelling will be proven out on Earth first at significant scale - like aluminum chassis satellite controlled vehicle fleets and smart grids + solar.  I haven't heard what their submarine car program is doing lately as it works toward Mar capable seals. 
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Offline JamesH65

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Re: Elon The Boring Company
« Reply #268 on: 04/21/2017 10:45 AM »
I don't think you are going to be able to build a 15km elevator even in Mars gravity, so you have to do a gradient. You would not want much beyond a 10% grade. Now you have a 150km tunnel. Not impossible, but not fun or easy either. That is a long way to remove rock.

But I think the radiation protection would be sufficient. If Mars is not susceptible to Radon leaks anyway.

Use a helical pattern (like a coil spring), then cross tunnels between coils for removing spoil. Just keep digging deeper and deeper. Would need a TBM designed to do a particular curve, plus smaller ones for the cross tunnels.

Offline Oersted

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Re: Elon The Boring Company
« Reply #269 on: 04/21/2017 12:37 PM »
I'd like to see some calculations on how deep it would be necessary to go on Mars to achieve an Earth-like atmospheric pressure. Also, what would the temperature be down there?

Would the eventual breathable atmosphere in a deep habitat need to be enclosed so as not to escape?

If a deep habitat could be expanded it would perhaps be interesting for farming.     

Offline Dao Angkan

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Re: Elon The Boring Company
« Reply #270 on: 04/21/2017 01:00 PM »
http://www.mide.com/pages/interplanetary-air-pressure-at-altitude-calculator

0m = 610 Pa (Datum)
-8,200m = 1,203 Pa (~Bottom Hellas)
-38,000m = 6,308 Pa (~Armstrong limit)
-90,500m = 33,695 Pa (~Everest Summit)
-111,000m = 53,578 Pa (~La Rinconada, Peru)

Online FutureSpaceTourist

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Re: Elon The Boring Company
« Reply #271 on: 04/21/2017 03:01 PM »
Some interesting info and speculation on SpaceX's tunnelling ambitions:

Quote
Will Harriet the tunnel-boring machine go to SpaceX now that her work on Crenshaw/LAX Metro line is done?

Quote
SpaceX submitted tunnel-digging plans to Hawthorne city officials just a few days after Harriets work on the LAX/Crenshaw Line finished on April 6.

The vertical tunnel shaft is complete. The next step is to dig the 500-foot-long horizontal pedestrian tunnel.

This tunneling will be conducted by excavating a large bore pit almost 20 feet by 150 feet and 13.5-foot diameter, said Arnie Shadbehr, Hawthornes interim city manager. Currently, plans are being reviewed by the city as well as the Fire Department.

http://www.dailybreeze.com/business/20170420/will-harriet-the-tunnel-boring-machine-go-to-spacex-now-that-her-work-on-crenshawlax-metro-line-is-done

Offline Dao Angkan

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Re: Elon The Boring Company
« Reply #272 on: 04/21/2017 03:36 PM »
http://www.lpi.usra.edu/meetings/geomars2001/pdf/7044.pdf

Quote
Geothermal  Gradients:  For  a  given  heat  flux,  geothermal  gradients  depend  on  thermal  conductivity.  On Earth, typical geotherms are around 30-35 K/km. Everything  on  Earth  is  water  saturated,  and  water  is  actually  a  relatively  poor  conductor  of  heat  (although  in convecting  systems  it  is  an  excellent  advector).  In  the upper  layers,  at  least,  of  Mars  we  expect  water  to  be frozen.  Ice  is  a  much  better  conductor  of  heat,  especially  at  lower  temperatures,  so  for  ice-filled  porosity on  Mars  we  expect  conductivity  ~  25%  better  than  on Earth. For dry but compacted regolith, we expect conductivities ~25% worse than on Earth. Consequently in dry  regions  of  Mars  we  might  find  geothermal  gradients  of    ~  10.6  K/km,  while  in  ice-saturated  zones  we would expect values of a mere 6.4 K/km.

...

Equator: For equatorial mean surface temperatures of  ~  220K

...

Temperate  Mars: A  typical  mean  annual  temperature of 200-210 K

...

Polar regions: below the permanent polecaps, year-round temperatures are buffered to ~150 K by subliming CO2 ice.

It should stay cooler deepest below the Polar caps;

[Polar Ice]
 0km  150.0K   
-1km  156.4K
-2km  162.8K
-3km  169.2K
-4km  175.6K
-5km  182.0K
-6km  188.4K
-7km  194.8K
-8km  201.2K
-9km  207.6K
-10km 214.0K
-11km 220.4K
-12km 226.8K
-13km 233.2K
-14km 239.6K
-15km 246.0K
-16km 252.4K
-17km 258.8K
-18km 265.2K
-19km 271.6K
-20km 278.0K (5C)
-21km 284.4K (11C)
-22km 290.8K (18C)
-23km 297.2K (24C)
-24km 303.6K (30C)
-25km 310.0K (37C)

https://en.wikipedia.org/wiki/Martian_polar_ice_caps#North_polar_cap

Quote
The ice cap in the north is of a lower altitude (base at -5000 m, top at -2000 m) than the one in the south (base at 1000 m, top at 3500 m)

So, below the base of the northern cap (-5km altitude);

Altitude  Temp.  Pressure  Triple Point
-25km      5C   3413 Pa    26C
-26km    11C   3595 Pa    27C
-27km    18C   3783 Pa    28C
-28km    24C   3978 Pa    29C
-29km    30C   4180 Pa    30C
-30km    37C   4388 Pa    31C

It should be quite pleasant, and able to support liquid water between 20km and 24km below the base of the northern cap. Still below the Armstrong limit, but might be close enough that terraforming could bring it above within human lifespans.
« Last Edit: 04/21/2017 04:14 PM by Dao Angkan »

Offline Dao Angkan

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Re: Elon The Boring Company
« Reply #273 on: 04/22/2017 07:09 AM »
http://nopr.niscair.res.in/bitstream/123456789/2506/1/IJRSP%2037%281%29%2064-67.pdf

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According to theory and observation, the temperature, pressure  and  density  of  undisturbed  air  at  3.5  km depth  in  the  Western  Deep  should  be  330  K,  1.48 P0and 1.3 ρ0, respectively. It is understood that after the introduction  of  refrigerated  air,  the  temperature  is brought down to 28C or 301 K and the pressure rises to  2P0  as a  result.  One can verify that0.52 moles of refrigerated  air  at  220  K  and  1.48  moles  of  ambient air  at  330  K  can  account  for  the  working  condition temperature   and   pressure   of   301   K   and   2P0, respectively. 

  One  should  point  out  that  atmospheric  pressure  at the  surface  of  the  mine  (elevation  1740  m)  is  only about  82%  that  at  sea  level 17.  However  that  does  not affect  the  results,  which  are  expressed  in  terms  of surface pressure and density.

On deep mines on Earth, the temperature is regulated by pumping in refrigerated air from the surface. In this example it brings down the temperature from 330K (57C) to 301K (28C). That also has the result of increasing air pressure by a further 35%, in addition to the air pressure increase due to depth.

Altitude  Temp. Pressure    Triple Point
-30km    37C   4388 Pa    31C
-31km    43C   4603 Pa    31C
-32km    50C   4824 Pa    32C
-33km    56C   5054 Pa    33C

With air conditioning, decreasing temperature by ~29, increasing pressure by ~35%;

Altitude Temp.  Pressure    Triple Point
-30km      8C   5930 Pa    36C
-31km    14C   6220 Pa    37C
-32km    21C   6519 Pa    38C
-33km    27C   6830 Pa    39C

An air conditioned tunnel 28km below the base of the northern cap (-5km) would be above the Armstrong limit (according to the models used above).

http://www.maintworld.com/Applications/A-Tunnel-Boring-Machine-Makes-Mining-History-in-Australia

This 8m diameter mining TBM did a 1:6 grade decline tunnel at up to 25m/day.

Quote
To meet schedule requirements, the mine opted for the use of a Tunnel Boring Machine (TBM), marking the first use of TBM technology in a mine on the continent. Due to the geological and mine conditions, the TBM was highly customized. The Robbins Company, the worlds first and foremost TBM manufacturer, supplied the Dual Mode Crossover TBM that could excavate in both hard rock and mixed ground, and in the presence of potentially hazardous methane gas.

Presumably a Mars specific TBM could achieve a steeper grade and faster rates.

http://www.therobbinscompany.com/en/news-events/world-records/

TBM records;

7.01 8.00m diameter
Best Day  Best Week  Best Month  Monthly Average
115.7m    428m         1482m        770m/mo

200m/wk might be a realistic average to aim for, or 10km/yr. Theoretically you could go 4x faster if you could repeat the "best day" rate continuously.

A 1:6 grade decline tunnel to 28km depth would be 168km long. About 17 years at 200m/wk (about the same length of time as the Gotthard Base Tunnel took).
A 1:5 grade decline tunnel to 28km depth would be 140km long. About 14 years at 200m/wk, down to less than 4 years at theoretical maximum of 800m/wk.
« Last Edit: 04/22/2017 07:46 AM by Dao Angkan »

Offline guckyfan

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Re: Elon The Boring Company
« Reply #274 on: 04/22/2017 08:23 AM »
A 1:6 grade decline tunnel to 28km depth would be 168km long. About 17 years at 200m/wk (about the same length of time as the Gotthard Base Tunnel took).
A 1:5 grade decline tunnel to 28km depth would be 140km long. About 14 years at 200m/wk, down to less than 4 years at theoretical maximum of 800m/wk.

Living 28km down is one thing. A drive of 140km or 200km to get out is another. Doesn't sound good to me. If this is done it needs a vertical shaft. Building climbing elevators instead of elevators hanging on a rope should not be the issue. But then you may want to balance two elevators, one going up, one going down.

Offline Dao Angkan

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Re: Elon The Boring Company
« Reply #275 on: 04/22/2017 08:35 AM »
I imagine that most people would live close to the surface, commuting to the fish farms or whatever it is that requires the higher pressure. The main tunnel could be a high speed rail line, with very little drag. 280kph train would take 30 minutes from surface to bottom.

Edit: Maybe a Hyperloop inside of the main tunnel would be better. Potentially a less than 10 minute journey.

Edit 2: Once the main tunnel is completed it would also be a lot quicker to excavate parallel tunnels with multiple smaller TBMs starting simultaneously from different depths and meeting up. It would probably be best to excavate a separate parallel Hyperloop tunnel.
« Last Edit: 04/22/2017 09:08 AM by Dao Angkan »

Offline MickQ

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Re: Elon The Boring Company
« Reply #276 on: 04/22/2017 09:23 AM »
If the tunnel diameter was big enough you could have both a high speed passenger train and a slower and heavier cargo version together.  Both could use gravity and aerobraking assistance on the way down along with electromagnetic braking to generate power that is used on the next ascent.

Offline wes_wilson

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Re: Elon The Boring Company
« Reply #277 on: 04/22/2017 02:38 PM »
A 1:6 grade decline tunnel to 28km depth would be 168km long. About 17 years at 200m/wk (about the same length of time as the Gotthard Base Tunnel took).
A 1:5 grade decline tunnel to 28km depth would be 140km long. About 14 years at 200m/wk, down to less than 4 years at theoretical maximum of 800m/wk.

Living 28km down is one thing. A drive of 140km or 200km to get out is another. Doesn't sound good to me. If this is done it needs a vertical shaft. Building climbing elevators instead of elevators hanging on a rope should not be the issue. But then you may want to balance two elevators, one going up, one going down.

If you look at many typical mining operations, they have both.  There are multiple vertical shafts with varying and sometimes multiple purposes of ventilation, escape, rapid ingress/egress of people, etc.  There are also horizontal shafts for moving very large equipment, conveyor belts to remove debris/ore, etc

These aren't mutually exclusive.

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Online RonM

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Re: Elon The Boring Company
« Reply #278 on: 04/22/2017 03:51 PM »
So, why is drilling down dozens of kilometers better than an airlock? The airlock would be a lot cheaper. A base consisting of tunnels only needs to be about 10 meters deep to reduce radiation. Might want to be a little deeper to insure a stable tunnel, but you don't have to go orders of magnitude deeper.

Offline Dao Angkan

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Re: Elon The Boring Company
« Reply #279 on: 04/22/2017 04:18 PM »
You'd still need to live behind an airlock anyway, as even with an air conditioned tunnel at 28km below the northern cap you still only get 7 kpa pressure*.

You do get a nice temperature, and liquid water, so it could be a low energy method of obtaining water (just transport blocks of polar ice and leave to melt). You can continuously expand without needing to pressurise, lots of land for aquaculture. Crops such as wheat can be grown at 7 kpa, so you would just need unpressurised tents with the right atmospheric mix. As it's above the Armstrong limit you wouldn't need a pressure suit, just breathing apparatus.

* Assuming that those models are accurate.
« Last Edit: 04/22/2017 04:27 PM by Dao Angkan »

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