Science Hyperloop! - featuring Elon Musk (TM)

[RGClark]

So, why bother with the relatively strong inside? If someone wanted to cause damage, the better target is the structure itself from the outside. Do you really think they can seal off 700+ miles of tube? If something goes catastrophically wrong with a vehicle, at worst you'll have to shut down, pound the dents out of the tube while sweeping up the debris and mourn 28 people. An attack on the outside could shut it down for months while they have to rebuild, and could easily affect more than one vehicle. Any real security expert (anyone not affiliated with the tsa) would agree. City buses go without a checkpoint and carry far more people. Trains run around hundreds of thousands of miles of unguarded track carrying far more people without incident every day also without checkpoints. There is nothing novel about fixed-guideway transport. The technology is cool and new, but it's just like a railway, or monorail and those have been around for a hundred and fifty years.

For safety reasons I'd prefer it to be underground. The cost though might be prohibitive for a tunnel this long based on costs of subway systems, already at the billion dollar range at lengths in the 20 km range.

Bob Clark

 

[Urwumpe]

Well, talk about a Large Human Collider. I still can't see how a high speed object containing humans inside a loop can be safer than the current railroad system, I mean yes it significantly reduce the risk of derailing to close to 0%, but it is also very easy to put a nut and bolt and hope it will do much damage given the speed the thing's going.

How could you get inside the tube? Unless you mean sabotage?

 

[Kendo]

Just curious here, if a passenger had, say, a pen for instance, and dropped it, what would happen with the pen. Would it drop to the floor or would shoot backwards at 800 mph.

 

[Hielor]

Just curious here, if a passenger had, say, a pen for instance, and dropped it, what would happen with the pen. Would it drop to the floor or would shoot backwards at 800 mph.

:facepalm:

The exact same thing that happens if you're in a car travelling at 60mph and you drop a pen. Does it shoot backwards at 60mph?

 

[Thunder Chicken]

Also, about the lack of windows: Only few complain about having to spend 20 minutes in the 50 km long Channel tunnel.

Even if this were an issue, an easy fix would to simply install screens that showed an animated/CGI artificial landscape that accelerated and decelerated with the train. Cheap fix to keep folks with motion sickness issues happy, and potentially entertaining.

http://www.youtube.com/watch?feature=player_embedded&v=Vqu9NuINKbc

About 1:45 shows the general idea.

 

[sorindafabico]

http://jalopnik.com/a-physicist-explains-the-three-biggest-challenges-for-t-1123562141

 

[Unstung]

The "TSA security theater" works. There hasn't been a terrorist attack on a US airplane since it all started, so obviously it's working.

Correlation does not imply causation. This is also known as false cause, it's a fallacy. The reasoning for why the TSA may not have prevented any "terrorist attack" is Basement stuff. Zatnikitelman already made some points that I didn't notice before posting this.

I've made a thread for the TSA discussion: http://orbiter-forum.com/showthread.php?t=32007

 

[Pipcard]

This reminds me of something:

except it's in California, not underwater, and not a vacuum.

 

[RGClark]

http://jalopnik.com/a-physicist-explains-the-three-biggest-challenges-for-t-1123562141

Since the vehicles are to have a fan in the front I wonder if it would be cheaper just to give each of them a turbofan and dispense with the expensive maglev propulsion system.
The vehicles are about the size of a small business jet. They could be based on that without wings. You would make the engines be electrically powered rather than burning jet fuel.
Since the engines are electrically powered they don't need a combustion chamber or turbine, so they would be cheaper and lighter.
Also, since jet planes typically fly at 30,000 feet at air pressure 1/3rd atm the requirements of evacuating the tunnel would be cheaper.

Bob Clark

 

[Urwumpe]

The vehicles are about the size of a small business jet. They could be based on that without wings. You would make the engines be electrically powered rather than burning jet fuel.

If you make an "electrically powered turbofan" you have simply the same compressor left that the hyperloop already has. :facepalm:

And a linear electric motor is simply by orders of magnitude more efficient than a compressor with a nozzle to accelerate it. Also you can't use the turbofan then for slowing down, while a linear electric motor has quite a high force for stopping.

 

[T.Neo]

Now... what does that remind me of...

Oh, I know! The unobtanium magma-drill Virgil, from The Core!

:shifty:

 

[Capt_hensley]

^ Definately! Without a doubt.

 

[RGClark]

If you make an "electrically powered turbofan" you have simply the same compressor left that the hyperloop already has. :facepalm:
And a linear electric motor is simply by orders of magnitude more efficient than a compressor with a nozzle to accelerate it. Also you can't use the turbofan then for slowing down, while a linear electric motor has quite a high force for stopping.

Orders of magnitude more? That doesn't seem likely considering the vehicles are so small and only have to run for 1/2 hour. The engines in jets also have to have enough power to propel the large mass of fuel which wouldn't be the case here.
I'm not sure even the compressors typical in turbofans would be needed in this case since the greatest proportion of the thrust in turbofans is provided by the bypass air, which as the name implies, bypasses the compressors and the combustion chamber and is accelerated out the back just by the large fan in front. The compressors in usual turbofans are needed because compressed air provides improved efficiency during combustion, which wouldn't be used here.
We can probably estimate how much power it would take based on the fuel usage of jets this small size for only 1/2 hour. Then we would divide this by a half to a third since you don't have the mass of fuel to accelerate. Then you would divide this by an additional fraction since internal combustion engines of this type are typically inefficient of commonly 30% efficiency, while electrical motors, which would be used in this case, commonly have high efficiency of 85% to 90%.
Commercial jets also have thrust reversers that are used to slow down.

Bob Clark

 

[Evil_Onyx]

Humm, Running a Jet inside a sealed tube would:

1. Be more efficient (trust wise) limited amounts of air means it can create a bigger low pressure in front of it, as there is less air rushing in from all directions.

2. Consume far more O2 than a system with out it. so bigger air vents (pumps?)

3. Be a massive safety risk. What would happen if one failed and court fire?

But then in the Proposal they only mention a compressor at the front to reduce drag. in other words they want to use it to compress the air that the capsule is going to pass though and vent it out the back. The reason that i see for it is to reduce the bow wake(not the correct term but i cant think of the correct one now), so there is less stress on the tube.

All in all, I like the concept of this proposal, but I don't see it getting of the ground for 20-30 years. There are so many challenges to the project that it will need allot of effort and will power to get it started.

 

[thepenguin]

Humm, Running a Jet inside a sealed tube would:
3. Be a massive safety risk. What would happen if one failed and court fire?

Fire in a vacuum? doesn't seem likely unless the internal/breathing O2 containers exploded...

 

[Evil_Onyx]

Fire in a vacuum? doesn't seem likely unless the internal/breathing O2 containers exploded...

Im not been that serious, but if you have a air breathing jet you gotta have a supply of O2 nearby.

 

[RGClark]

Humm, Running a Jet inside a sealed tube would:

1. Be more efficient (trust wise) limited amounts of air means it can create a bigger low pressure in front of it, as there is less air rushing in from all directions.
2. Consume far more O2 than a system with out it. so bigger air vents (pumps?)
3. Be a massive safety risk. What would happen if one failed and court fire?
But then in the Proposal they only mention a compressor at the front to reduce drag. in other words they want to use it to compress the air that the capsule is going to pass though and vent it out the back. The reason that i see for it is to reduce the bow wake(not the correct term but i cant think of the correct one now), so there is less stress on the tube.
...

In my alternative proposal, the jet engines would be electrically powered. No jet fuel, no combustion.
In regards to energy efficiency it occurs to me also a big proportion of the power just goes to run the compressors in usual jet engines. So if it is the case they aren't needed for the electrically powered version, then that is a further reduction in the energy requirements in this case.

Bob Clark

 

[Thunder Chicken]

The Probe: "Elon?"

Elon looks up from large play area filled with rocket stages and trains and venture capitalists with kung fu grips.

Elon Musk: "Yes, dearest Probe?"

: "You need to finish playing with the Falcon and Dragon and the Grasshopper first, then put them away BEFORE you start playing with your Hyperloop. OK?"

Elon Musk <sulkily>: "Yes Probe. <sigh>"