Just thinking out loud here.... suppose you could create a standing wave within the tube using sound waves to move the air instead of a fan? ....and somehow the 'vehicles' acted like a repeater/conduit, meaning that if they were stationary within the tube it would mean that they were "matched" with the standing wave present within the tube from nose to tail of the vehicle. <-depending on the length of the vehicle this would vary, In order for the vehicle to move forward or backwards, all it would need to do is create a small phase lead or lag of the standing wave. Still quite a bit of power required, but perhaps less than a fan. This could be analogous to AC (standing wave) vs. DC (fan) in electronics. AC might prove to be a better energy carrier over distance.
The speed of sound is a function of temperature, and not pressure. This tube thing works by circulating the entire column of air by 600 MPH. It's basically a 700 mile long wind tunnel. It's seems like the air resistance along the skin of 700 miles of tube would require a lot of power to overcome, but maybe it's not that bad. It depends on how smooth the inner surface is.
'smooth' is going to cost more money, and the Energy budget numbers simply fail to stack up.
A rough calc, which a school kid could do, gives around 50,000~150,000 tonnes of moving air, half going north at 600MPH, and half going south at 600MPH.
That change of direction is a lot of momentum to transfer, and a large number of pumping/fan stations will also be needed due to the high elasticity of air.
>That change of direction is a lot of momentum to transfer
I expect the air loop to take a rather large radius half circle at the end, the car tubes could travel a more straight line to the station.
>but could your morning breakfast decelerate at that speed
1G is not much, though lasting a whole minute (at 600mph) could make for a little discomfort but probably not barfing.
1G is 22 MPH/second. Basically, it's "0 to 60" in 2.7 seconds, or 0 to 600 MPH in 27 seconds. According to zeroto60times.com, you would need the acceleration of something like a Lamborghini to do 0 to 60 in 2.7 seconds.
If you want to accelerate to 600 MPH in one minute, that would be 0.45G of acceleration. Now we're talking about 0 to 60 in 6 seconds, which is more like the acceleration of a Chevy Impala LT.
Wouldn't it be more energy efficient to pressurize the cars and evacuate the tunnel? With such short travel times providing air would not be that difficult.
Who exactly has the tens or hundreds of billions needed for this boondogle? CA is broke, I won't even bother to deal with litigating the right of ways which is a nightmare even with the proposed bullet train.
Wouldn't it be more energy efficient to pressurize the cars and evacuate the tunnel? With such short travel times providing air would not be that difficult.
That's not a bad idea, except the cost of building a 700 mile long tube that could hold a vacuum would be quite expensive. However, instead of building a tube, the tracks could be elevated to an altitude where the air density is lower, and there would be less air resistance. And the car could use air foils to push against the remaining air to elevate itself instead of requiring air jets or magnetic elevation. If fact, we could dispense with the tracks and tube entirely. Now we just need a way to propel the car at high altitude. Once again, the residual air at high altitude could be combined with some form of fuel, and then expelled backwards at a high speed. Now we just need a way to levitate the car when it's at low speed and near the ground. Maybe a set of wheels could be used that would retract into the car once it is moving fast enough to be levitated by the air.
That's not a bad idea, except the cost of building a 700 mile long tube that could hold a vacuum would be quite expensive. However, instead of building a tube, the tracks could be elevated to an altitude where the air density is lower, and there would be less air resistance. And the car could use air foils to push against the remaining air to elevate itself instead of requiring air jets or magnetic elevation. If fact, we could dispense with the tracks and tube entirely. Now we just need a way to propel the car at high altitude. Once again, the residual air at high altitude could be combined with some form of fuel, and then expelled backwards at a high speed. Now we just need a way to levitate the car when it's at low speed and near the ground. Maybe a set of wheels could be used that would retract into the car once it is moving fast enough to be levitated by the air.
So it turns out to be a low pressure (not complete vacuum) with a turbine sucking any air in front to the down/back like a hover craft.
Friction is so low that linear motors are only needed for 1% of the length of track to give the pod a boost now and then.
Comments
Reference? No Googling!
'smooth' is going to cost more money, and the Energy budget numbers simply fail to stack up.
A rough calc, which a school kid could do, gives around 50,000~150,000 tonnes of moving air, half going north at 600MPH, and half going south at 600MPH.
That change of direction is a lot of momentum to transfer, and a large number of pumping/fan stations will also be needed due to the high elasticity of air.
Has someone spent real money on this ?
I expect the air loop to take a rather large radius half circle at the end, the car tubes could travel a more straight line to the station.
>but could your morning breakfast decelerate at that speed
1G is not much, though lasting a whole minute (at 600mph) could make for a little discomfort but probably not barfing.
If you want to accelerate to 600 MPH in one minute, that would be 0.45G of acceleration. Now we're talking about 0 to 60 in 6 seconds, which is more like the acceleration of a Chevy Impala LT.
Made ME laugh out loud!
http://en.wikipedia.org/wiki/Gravity_train
Friction is so low that linear motors are only needed for 1% of the length of track to give the pod a boost now and then.
http://www.teslamotors.com/sites/default/files/blog_images/hyperloop-alpha.pdf