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| The Hyperloop: BUSTED |
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| technogeeky:
--- Quote from: TerraHertz on July 25, 2016, 05:55:32 am --- --- Quote from: EEVblog on July 25, 2016, 05:08:09 am --- --- Quote from: TerraHertz on July 25, 2016, 04:15:35 am ---My only question is, why is Musk involved in this? --- End quote --- He's not, finacially. http://www.spacex.com/hyperloop "Neither SpaceX nor Elon Musk is affiliated with any Hyperloop companies" --- End quote --- Ah ha, interesting. And yet: "To support this competition, SpaceX will construct a one-mile test track..." So he does have dollars in it. I was mostly joking about the 'idiot filter' idea, but given Musk's involvement in 'Hyperloop concept support', including his personally coining the name, maybe it's not such a crazy thought after all. He may not be an engineer, but he is smart and employs a lot of good engineers. Surely some of them would have explained Hyperloop's fundamental flaws to him, if he didn't see them himself? As a name, "Hyperloop(y)" is a pretty cool joke. It's almost a stand-alone sanity check in itself. --- End quote --- He is an very good engineer, and he had some very good engineers on the design document that he released the document Hyperloop Alpha |
| mtdoc:
--- Quote from: technogeeky on July 25, 2016, 06:06:52 am --- He is an very good engineer, and he had some very good engineers on the design document that he released the document Hyperloop Alpha --- End quote --- Nah. That's just the paper he used to introduce the concept. It is not intended to be any sort of engineering or comprehensive design document. --- Quote ---Hyperloop is considered an open source transportation concept (emphasis mine). --- End quote --- |
| HP-ILnerd:
Clearly, I haven't thought about this as hard as you guys or Thunderf00t, so I have a couple questions: 1)If the air pressure from a catastrophic fail up-tube is a problem, why wouldn't you make the tube capable of sensing that it has failed up-tube? 2)If you have done so and it has sensed this, why wouldn't you deliberately start venting air into the tube in a controlled fashion all along the tube? Air in the tube would help any transiting hyperloop cars stop, right? 3)Since you need expansion joints, why wouldn't you take advantage of the non-standard section to add a door that drops down to block the tube in the event of a catastrophic fail? It need not even be air-tight, it just has to make the air passage a lot smaller. Could be made of cement with a steel top held up by permanent magnets. In case of emergency, just disrupt the magnetic field of the permanent magnet (just like fire doors) and gravity does the rest. Maybe every 5 km or so? However far the maximum stopping time of a car in the tube is. These expansion joints also seem like a good spot to put the re pressurization valves noted above? 4)I'm just a programmer, not a thermal guy, but since he pointed out the temperature differential of the top of the tube in sunlight vs the bottom. Is the top of tube being in shade (solar panels!) all along its length not going to make any difference? 5)How can "the power go out" if it is locally powered by all those solar panels? Was the power all supposed to be sent back to some centralized bank 600km away? Since Thunderf00t didn't even suggest any solutions of the sort, I assume they can't work? |
| optoisolated:
--- Quote from: HP-ILnerd on July 25, 2016, 06:47:20 am ---1)If the air pressure from a catastrophic fail up-tube is a problem, why wouldn't you make the tube capable of sensing that it has failed up-tube? --- End quote --- To a limited extent, you could. The issue comes down to the practicality of such a safety mechanism. It would require a complex array of sensors and mechanisms in order to adequately seal and safely repressurise the system. The issue is there are too many single-points-of-failure. --- Quote from: HP-ILnerd on July 25, 2016, 06:47:20 am ---2)If you have done so and it has sensed this, why wouldn't you deliberately start venting air into the tube in a controlled fashion all along the tube? Air in the tube would help any transiting hyperloop cars stop, right? --- End quote --- The key here is 'controlled fashion'. It requires many complex systems all working correctly to acheive this. It's not impossible, but grossly impractical. Remember: these safety mechanisms would need to be replicated the entire length of the hyperloop. --- Quote from: HP-ILnerd on July 25, 2016, 06:47:20 am ---3)Since you need expansion joints, why wouldn't you take advantage of the non-standard section to add a door that drops down to block the tube in the event of a catastrophic fail? It need not even be air-tight, it just has to make the air passage a lot smaller. Could be made of cement with a steel top held up by permanent magnets. In case of emergency, just disrupt the magnetic field of the permanent magnet (just like fire doors) and gravity does the rest. Maybe every 5 km or so? However far the maximum stopping time of a car in the tube is. These expansion joints also seem like a good spot to put the re pressurization valves noted above? --- End quote --- Again, such safety mechanisms are possible, but impractical, and would be expensive. They would add to the cost of maintenance and upkeep of the system and should any part of the system be offline for maintenance or malfunctioning, the entire system would be potentially unsafe to a catastrophic failure. From what I've seen of the projected construction costs, it seems unlikely these sort of safety mechanisms have been taken into consideration. I can't speak to points 4 and 5. One thing worth noting (and where I foresee a massive obstacle to such a system) is what would happen in the event of a turbine blade failure. It seems from the animations that there isn't much margin for movement within the carriage within the tunnel. In a turbine failure, the outer containment shell will warp to absorb the impact of the massive amount of kinetic energy stored in those blades. If that distortion happened at speed, the carriage would likely disintegrate, and if it didn't it would likely deform to the point where it would make contact with the outer walls of the tunnel. The same outcome would likely occur in that scenario. By comparison, turbine blade failures occur occasionally during an an aircraft flight, for instance, and often result in the loss of an engines power, but no significant impact to the safe operation of the aircraft. Even in the event of significant damage (See QF32: ) the aircraft isn't in a tube where it could potentially impact the fuselage. Multiple redundant control systems meant the aircraft was still flyable and able to be safely landed. The pilots had room to maneuver and react. The turbine blade containment failure in this incident resulted in the kinetic energy in the blades being directed away from the aircraft for the most part. In a tunnel, this would be bad news, likely resulting in localised tunnel failure and worse yet, ricochet of debris within the cabin. While I love the innovative effort of this project, it's just a non starter from a safety and cost perspective. It's ultimately cheaper and safer, to use other proven technologies like Maglev trains and Aircraft. |
| Brutte:
I am watching the linked YT. I do not like the part that describes thermal expansion. The deduction is flawed. It assumes no longitudinal strain is acceptable in the design while we know the strain is not a problem today - take a look at continuous (welded) railroads. Thermal expansion is a design parameter. Besides, there are other materials available, like concrete, composites, elastomers, etc. As for steel, the 50mm expansion of 100m tube over [0:40]DegC seems like impossible to overcome. Otoh, that is a strain of only 100MPa (G=210GPa) or +-50MPa if you weld it at 20DegC. Any steel is capable of 50MPa. The one used for industrial piping goes up to 500MPa. Mind this is only the expansion part and the construction is subjected to other factors (vacuum, rust, terrorists, thieves, etc). I would NOT use steel for members at compression, especially where the mass plays no role. I believe the steel is a temporary solution and the precast reinforced concrete + elastomeric joints are more likely to be a viable solution because of the cost and durability. The idea that if the tube gets ruptured at any place and people inside die instantly because of the vacuum is also flawed. The capsules are pressurized and if the tube is punctured and filled with atmospheric air (gradually, via size-limited hole) then the drag would increase gradually and the capsule would eventually slow down. For God's sake that is not 600km of single piece of pipe and some locks are needed |O You can die there when you derail or exceed G, but OTOH slowing down 900km/h (250m/s) at 5G (50m/s2, at emergency) takes lousy 5 seconds. Just let some air into a tube in a controllable manner. Ok, that is 625m to a standstill but dude, I would not exaggerate, at least you cannot hit the moose on the road. Hitting a coke can with a ball :-DD Where is the BUT? As of the emergency exiting, I think it should be presented in relation to emergency exiting when KLM + Pan AM meet on one runway. How about then? The weakest part of the project is its capital cost and technological challenges of the scale. It competes with airplanes so it is not hard to calculate the borderline cost of the trip of the hyperloop. Make it more expensive and people won't buy it. |
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