Author Topic: Episode #725  (Read 3179 times)

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Offline MikeHz

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Re: Episode #725
« Reply #15 on: June 03, 2019, 11:50:34 AM »
I had to work out of town for a year, and so lived in an apartment away from home during that time. I came home on weekends, but was alone the rest of the time. I found that life alone sucked, and after a year gave up the job. Much less stressful living with my wife, but then, we live pretty stress-free lives anyway.
"It's easier to fool people than to convince them they have been fooled." Mark Twain

Offline Darb

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Re: Episode #725
« Reply #16 on: June 03, 2019, 05:12:07 PM »
The Boring company's tunnel that the car drove through is NOT a hyperloop and never was intended to be a hyperloop. 


Whenever I hear the word "carapace" I hear it the way Carl Sagan said it on the original Cosmos..... caraPACE... :)



Online daniel1948

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Re: Episode #725
« Reply #17 on: June 03, 2019, 06:05:11 PM »
If Musk never comes up with another good idea or successful company, he will have accomplished more than 99.999% of people ever have, and will go down in history as a genius. He could spend the rest of his life inventing crackpot ideas and investing his personal fortune in them, and he'd still be a hero in my book for single-handedly creating the modern electric car industry. Solar City, now owned by Tesla, is another company dedicated to saving the world. And SpaceX is extremely impressive.

I wouldn't count him out yet, even if he comes out with a few duds before his next good idea.
Daniel
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Offline arthwollipot

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Re: Episode #725
« Reply #18 on: June 03, 2019, 07:58:59 PM »
The Boring company's tunnel that the car drove through is NOT a hyperloop and never was intended to be a hyperloop.

What it is however is a proof-of-concept for a technology that might in the future be used to build tunnels for a hyperloop.
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Offline brilligtove

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Re: Episode #725
« Reply #19 on: June 03, 2019, 08:49:21 PM »
If we ever make monofilament blades that work in the real-world the implications for mining are insane. Tunnelling that takes vast amounts of power and time now? You'd be limited by how fast you can cart the rubble away and shore up the structure. Maybe he's making a long bet on tunnelling tech that depends on materials that don't exist yet.
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Offline mabell_yah

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Re: Episode #725
« Reply #20 on: June 03, 2019, 11:09:58 PM »
I would sign up at whatever Patreon level it takes to get access to Cara's Carpool Karaoke.

Offline mabell_yah

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Re: Episode #725
« Reply #21 on: June 03, 2019, 11:22:37 PM »
I'm more optimistic about Hyperloop, though still cautious. I feel like the rogues were overly critical without a lot of substantiation.  I can see suspending the tubes between buildings in town. Futurama anyone? Out of town you can hang them from towers. This seems way smarter than 19th century road bed grading. It also gets you over the dreaded Grapevine in southern California.

The costs are completely unknown at this point, yet Steve confidently proclaims maglev to be cheaper. Really? Maglev requires liquid freaking helium. I wouldn't brag about how cheap it is.

The bottom line that should be emphasized is air resistance - energy thrown away by every alternative, be it train, plane or automobile. I remember seeing on Top Gear the amazing amount of horsepower that had to be pumped into the Bugatti Veyron to push the top speed from 250 to 260 MPH.

I would love to see the rogues revisit this issue in a less cavalier treatment. There's no rush though. Give it some time to flesh out some critical details.

Online The Latinist

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Re: Episode #725
« Reply #22 on: June 03, 2019, 11:46:28 PM »
I still think everyone is missing the point with Musk and his ventures. I think he's been trying to build a set of sustainable businesses that can produce the critical components of a moon base (solar power, battery storage, airtight pod-style transportation, rockets, efficient tunnelling...). Assuming he doesn't completely mess up his whole portfolio, I expect him to start a company or consortium working on sealed undersea habitats or similar - something to do with long term terrarium-style life support - in the next couple years.

It's not about the Moon, but Mars. He's has been open for years about all of his ventures being targeted at his ultimate aim of colonizing Mars. He isn't joking when he says he wants to die on Mars.
I would like to propose...that...it is undesirable to believe in a proposition when there is no ground whatever for supposing it true. — Bertrand Russell

Offline DamoET

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Re: Episode #725
« Reply #23 on: June 04, 2019, 09:22:38 AM »
Naturally aspired engines (i.e. not electric or turbo) will get a decrease in power and efficiently correlating with air pressure drop, just like driving at altitude. Also, removing air resistance won't on its own won't allow normal cars to go that much faster efficiently.

Keep in mind I haven't yet listened to the podcast for context, but on flat terrain, air drag is by far the largest resistance factor (>90%), and so anything that reduces aerodynamic drag will result in an increase in speed for same power, or reduced power demand for the same speed. If you remove air resistance (while not hampering ability to generate power), a vehicle will be able to travel a huge amount faster for the same power output.

One thing to point out is that the numbers Jay gave (speed vs economy) are averages. The more aerodynamic the vehicle, and the smaller the frontal area, the faster you can go before aerodynamic drag starts to increase quadraritically or worse with speed. (Boxier shapes have a worse-than-quadratic ramp-up in drag.) It is an "empirical law" meaning most aerodynamic stuff that we makes experiences approximately quadratic increased in drag at the speeds we typically use them.

Putting aside any funkiness with the relationship between CdA* and Reynolds number**, then the function of drag with air velocity is a quadratic equation no matter the speed of the car and wind, nor the shape of the vehicle. There is no speed it cuts in or cuts out (unless and until the relationship between CdA and Reynolds number changes - which is the sort of thing that occurs over orders of magnitude changes in velocity).

All that happens with vehicles with a less streamlined shaped is they have a higher CdA. As a result at the same air velocity (ceteris paribus) they present a greater drag, and hence require more power to sustain such a velocity. Since the drag is a quadratic relationship with velocity (and linear with CdA), then there is a cubic relationship between power and velocity (and it's still linear with CdA).

IOW, a doubling of the velocity requires 2³ = 8 times the power to overcome the additional aerodynamic drag.
A doubling of CdA requires a doubling of power to overcome the additional aerodynamic drag. The CdA change can be as a result of changes in size and/or shape.


* Cd = Coefficient of Drag (dimensionless)
A = Effective Frontal Area (SI units m²)
CdA = Cd x A (SI units m²)

** assuming CdA is constant over the range of Reynolds numbers in consideration for vehicles - which is a reasonable assumption for most motor vehicles and speeds.

  To add to the above, an increase in engine speed requires the square increase of the fuel consumed to sustain that speed.  So, if an engine requires 1ltr of fuel per hour to sustain 2000rpm, it will require 4ltrs per hour of fuel to sustain 4000rpm.  Therefor, a car traveling at 100kmh using 5ltr/hr (4lt/hr to over come wind resistance and 1lt/hr to maintain engine speed), would require 36ltr/hr (32ltr/hr to overcome wind resistance and 4ltr/hr to maintain engine speed)  @200kmh.  Having that 'car' operating in a vacuum would drop the 36ltr/hr to 4lt/hr.  This would be a similar thing for electric cars too, moving parts would represent low teens of the power consumed compared to air resistance.


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Offline 2397

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Re: Episode #725
« Reply #24 on: June 04, 2019, 09:30:35 AM »
Presumably they have to be electric cars. How do combustion engines work in low pressure environments?

Online Ah.hell

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Re: Episode #725
« Reply #25 on: June 04, 2019, 09:59:31 AM »
Presumably they have to be electric cars. How do combustion engines work in low pressure environments?
I think it could be done but they would need to be supplied with oxygen.

I am always amazed at the Musk fan boys.  He's had one successful venture which he used to see several very optimistic ventures that have mostly been funded by the irrational exuberance of folks with money. 

Tesla, has a chance but as far as I know it still hasn't made any money and lately has been beset by delays. 
SpaceX, Not sure, seems successful but still not clear if its going to be sustainable. 
Solar City, not actually that different from other solar stuff but will likely be sustainable.
Boring company, absolutely nonsense of an idea.  Not digging tunnels but the fantasy that he can some how out perform experts in a field by orders of magnitude.
Hyper-loop, absolute fantasy.  An idea that has been on the drawing boards for over a hundred years.   Performs moderately better than existing alternatives, and will cost at least twice what he thinks it will. 

Suspending tubes between buildings?  You'd still need to build entirely new structures to support these tubes.  They have to deal with Earthquakes, Hurricanes, tornadoes, bad soils, etc.   The infrastructure, as noted by Steve, is enormous in comparison to air travel and probably more than twice the cost of conventional high speed rail, which is also about

By the way, the Grapevine in California is a canyon in the Tehachapi mountains through which a road was built to get from LA to the Central Valley.  The ruggedness of the terrain is not biggest problem with running a train or hyper-loop through it. 

Quote
The Tehachapis are largely the result of the movements of the Garlock Fault, located along the southeastern base of the range, a major transform fault which runs from the San Andreas Fault in the west to the Sierra Nevada Fault on the east and some distance beyond. This earthquake fault is unusual in California in that it is a left-lateral fault — meaning that if one stands facing the fault, the land on the opposite side moves to the left — opposite to most of the state's faults which are right-lateral faults.

Offline brilligtove

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Re: Episode #725
« Reply #26 on: June 04, 2019, 10:01:54 AM »
I still think everyone is missing the point with Musk and his ventures. I think he's been trying to build a set of sustainable businesses that can produce the critical components of a moon base (solar power, battery storage, airtight pod-style transportation, rockets, efficient tunnelling...). Assuming he doesn't completely mess up his whole portfolio, I expect him to start a company or consortium working on sealed undersea habitats or similar - something to do with long term terrarium-style life support - in the next couple years.

It's not about the Moon, but Mars. He's has been open for years about all of his ventures being targeted at his ultimate aim of colonizing Mars. He isn't joking when he says he wants to die on Mars.

Fair enough. I think he's going to have to start on the moon, but you're right.
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Online The Latinist

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Re: Episode #725
« Reply #27 on: June 04, 2019, 11:41:46 AM »
I still think everyone is missing the point with Musk and his ventures. I think he's been trying to build a set of sustainable businesses that can produce the critical components of a moon base (solar power, battery storage, airtight pod-style transportation, rockets, efficient tunnelling...). Assuming he doesn't completely mess up his whole portfolio, I expect him to start a company or consortium working on sealed undersea habitats or similar - something to do with long term terrarium-style life support - in the next couple years.

It's not about the Moon, but Mars. He's has been open for years about all of his ventures being targeted at his ultimate aim of colonizing Mars. He isn't joking when he says he wants to die on Mars.

Fair enough. I think he's going to have to start on the moon, but you're right.

He’s never shown any interest in the moon at all.  Everything he does is aimed at Mars.  Will he fail? Probably.  But that’s his goal.

The rest of your analysis is right-on, though; all his ventures are aimed at developing space colonization technology.
I would like to propose...that...it is undesirable to believe in a proposition when there is no ground whatever for supposing it true. — Bertrand Russell

Offline DevoutCatalyst

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Re: Episode #725
« Reply #28 on: June 04, 2019, 12:31:09 PM »
Mars is as good a place as any to be when you're dead. Seems that Musk hasn't any interest in pioneering Mars with his own body.

Offline CarbShark

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Re: Episode #725
« Reply #29 on: June 04, 2019, 01:26:33 PM »
If we ever make monofilament blades that work in the real-world the implications for mining are insane. Tunnelling that takes vast amounts of power and time now? You'd be limited by how fast you can cart the rubble away and shore up the structure. Maybe he's making a long bet on tunnelling tech that depends on materials that don't exist yet.

Or plasma-torch tunneling.


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