Evacuated tube transport the end of Airlines?
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Originally Posted By: CT8
I was just thinking an airliner is a pressurized tube.
As a mechanical engineer, it scares me a little.
Aircraft don't have the full 101kPa differential pressure across them, maybe 60, so a tube in a full vacuum will have to be nearly twice as strong. No biggie, as you don't have to support it on wings, and raise it's mass.
Sealing vacuums is really tricky...power station we try to run 3kPa absolute in the condensers (which themselves end up being 2" thick steel plate WITH cross bracing)...and that's really hard to maintain...I can't imagine evacuating the types of volumes being proposed, let alone having sufficient strength economically to support the pressures from outside the transport tube trying to crush it...reinforced concrete most cost effective, but how to seal it ?
Then the logistics of breathable air inside the cell, and sealing that with no access to make-up air (aircraft have access, and when you are using the oxygen, you still aren't in full vacuum.
Then in the event of an emergency stoppage, time taken to reflood the tubes with air would require compartmentalisation...
Not saying any or all of it is impossible...everything is doable, but the engineering (and costs) will be massive.
I was just thinking an airliner is a pressurized tube.
As a mechanical engineer, it scares me a little.
Aircraft don't have the full 101kPa differential pressure across them, maybe 60, so a tube in a full vacuum will have to be nearly twice as strong. No biggie, as you don't have to support it on wings, and raise it's mass.
Sealing vacuums is really tricky...power station we try to run 3kPa absolute in the condensers (which themselves end up being 2" thick steel plate WITH cross bracing)...and that's really hard to maintain...I can't imagine evacuating the types of volumes being proposed, let alone having sufficient strength economically to support the pressures from outside the transport tube trying to crush it...reinforced concrete most cost effective, but how to seal it ?
Then the logistics of breathable air inside the cell, and sealing that with no access to make-up air (aircraft have access, and when you are using the oxygen, you still aren't in full vacuum.
Then in the event of an emergency stoppage, time taken to reflood the tubes with air would require compartmentalisation...
Not saying any or all of it is impossible...everything is doable, but the engineering (and costs) will be massive.
Part of me wonders what would happen if the vacuum was suddenly lost with a vehicle in the tube going at a tremendous velocity.
PV=nRT
PV=nRT
Originally Posted By: Rick in PA
Part of me wonders what would happen if the vacuum was suddenly lost with a vehicle in the tube going at a tremendous velocity.
PV=nRT
I once was witness to an emergency stop of one of the Wallerawang 500MW turbines...the LP turbines (4 flows) have 33.5" last stage blades, operated in a 5 kPa steam environment.
Normally takes 45minutes to roll down from 3,000RPM.
Operator opened the vacuum break valve, and the turbine started sounding just like the blades on a turbofan when they pitch them to stop...scary...and stopped 14 minutes later, with about a 40C rise in temperature locally.
Eraring power station with different design blades started breaking root attachments back in the '90s letting air in to trip turbines.
It's harsh...
Part of me wonders what would happen if the vacuum was suddenly lost with a vehicle in the tube going at a tremendous velocity.
PV=nRT
I once was witness to an emergency stop of one of the Wallerawang 500MW turbines...the LP turbines (4 flows) have 33.5" last stage blades, operated in a 5 kPa steam environment.
Normally takes 45minutes to roll down from 3,000RPM.
Operator opened the vacuum break valve, and the turbine started sounding just like the blades on a turbofan when they pitch them to stop...scary...and stopped 14 minutes later, with about a 40C rise in temperature locally.
Eraring power station with different design blades started breaking root attachments back in the '90s letting air in to trip turbines.
It's harsh...
Originally Posted By: Astro14
Otherwise, you'll have to settle for what the public demands: cheap and crowded.
The market has spoken.
So, unlike many other industries, the airlines have not been able to improve their product for a given cost.
They continue to hate their customers, and their customers continue to hate them. Airlines continue to vary costs wildly depending on ticket purchase date. Maybe we should have a variable rate for gasoline costs. Purchase it ahead of time, and save 500%. Need it now? Pay up.
But, I am not complaining. The airline experience is so universally awful, some will pay nearly anything to avoid the airlines. This keeps us corporate jet guys in business. Heck, I'm looking forward to when United starts making passengers stand up in those new seats...
Otherwise, you'll have to settle for what the public demands: cheap and crowded.
The market has spoken.
So, unlike many other industries, the airlines have not been able to improve their product for a given cost.
They continue to hate their customers, and their customers continue to hate them. Airlines continue to vary costs wildly depending on ticket purchase date. Maybe we should have a variable rate for gasoline costs. Purchase it ahead of time, and save 500%. Need it now? Pay up.
But, I am not complaining. The airline experience is so universally awful, some will pay nearly anything to avoid the airlines. This keeps us corporate jet guys in business. Heck, I'm looking forward to when United starts making passengers stand up in those new seats...
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Sure, a few trillions in investment, which ole Elon and all of his buddies combined can neither come up with nor borrow and this could be a reality some day.
Like never.
Musk seems to like sounding brilliant and cutting edge by pitching what sound like smart and cutting edge concepts that are technically and economically impossible.
The airlines survive because they offer rapid transport at a reasonable cost. We are pretty fond of air travel even while we may not be fond of sitting in the last couple of rows of a Mad Dog.
You want a better air travel experience?
Pay to sit up front. The difference in cost, especially considering bag fees is sometimes not all that much but the overall experience is so much more pleasant from check-in to debarkation.
An international config aircraft up front is really blissful.
Like never.
Musk seems to like sounding brilliant and cutting edge by pitching what sound like smart and cutting edge concepts that are technically and economically impossible.
The airlines survive because they offer rapid transport at a reasonable cost. We are pretty fond of air travel even while we may not be fond of sitting in the last couple of rows of a Mad Dog.
You want a better air travel experience?
Pay to sit up front. The difference in cost, especially considering bag fees is sometimes not all that much but the overall experience is so much more pleasant from check-in to debarkation.
An international config aircraft up front is really blissful.
Originally Posted By: fdcg27
You want a better air travel experience?
Pay to sit up front. The difference in cost, especially considering bag fees is sometimes not all that much but the overall experience is so much more pleasant
Certainly, first class is more pleasant once on the airplane. But the TSA, the long lines, the bag-drag, the check in clerk's nasty attitude, the poor treatment and utter lack of information during delays and cancellations remain.
Good God, the wait for TSA screening in Atlanta was epic, with the line snaking back through the cafeteria. Not a good experience regardless of ticket price.
You want a better air travel experience?
Pay to sit up front. The difference in cost, especially considering bag fees is sometimes not all that much but the overall experience is so much more pleasant
Certainly, first class is more pleasant once on the airplane. But the TSA, the long lines, the bag-drag, the check in clerk's nasty attitude, the poor treatment and utter lack of information during delays and cancellations remain.
Good God, the wait for TSA screening in Atlanta was epic, with the line snaking back through the cafeteria. Not a good experience regardless of ticket price.
That's what pre-check is for. It's absolutely worth the small effort and cost.
Had we not had this on our most recent departure from MSY I doubt that we'd have made our flight. The TSA line was that long.
I've heard that ATL is also really bad, but as many times as we've been at that airport, we've never been outside of it since we've only connected through it.
You're right in that departing from the GA terminal would be a whole lot more pleasant but it would also be a whole lot more expensive.
Had we not had this on our most recent departure from MSY I doubt that we'd have made our flight. The TSA line was that long.
I've heard that ATL is also really bad, but as many times as we've been at that airport, we've never been outside of it since we've only connected through it.
You're right in that departing from the GA terminal would be a whole lot more pleasant but it would also be a whole lot more expensive.
I fly a few times a year, I always book an early bird flight to avoid the crowds, idiots, nasty passengers and delays with TSA.
Originally Posted By: Mr Nice
I fly a few times a year, I always book an early bird flight to avoid the crowds, idiots, nasty passengers and delays with TSA.
...unless everybody is doing that (ORD to SFO...)
I fly a few times a year, I always book an early bird flight to avoid the crowds, idiots, nasty passengers and delays with TSA.
...unless everybody is doing that (ORD to SFO...)
I'm thinking,
If the pressurized tube loses vacuum, it won't be catastrophic to the occupants of the capsule as the capsule would have a failsafe mode for that; it would merely traverse the tube in a backup mode that doesn't enjoy the frictionless vacuum efficiency or speed.
What about if the capsule's hull was breached, and the occupants were then exposed to vacuum? Ugly!!! Wouldn't that be like a space suit failing during a spacewalk?
If the pressurized tube loses vacuum, it won't be catastrophic to the occupants of the capsule as the capsule would have a failsafe mode for that; it would merely traverse the tube in a backup mode that doesn't enjoy the frictionless vacuum efficiency or speed.
What about if the capsule's hull was breached, and the occupants were then exposed to vacuum? Ugly!!! Wouldn't that be like a space suit failing during a spacewalk?
Originally Posted By: L_Sludger
What about if the capsule's hull was breached, and the occupants were then exposed to vacuum? Ugly!!! Wouldn't that be like a space suit failing during a spacewalk?
The passengers would "merely" suffocate.
What about if the capsule's hull was breached, and the occupants were then exposed to vacuum? Ugly!!! Wouldn't that be like a space suit failing during a spacewalk?
The passengers would "merely" suffocate.
I think that the event would be more dramatic and painful than that.
It would depend upon how quickly pressure was lost.
A major breech would be felt by those onboard while a minor leak would merely cause them to lose consciousness on the way to their demise.
It would depend upon how quickly pressure was lost.
A major breech would be felt by those onboard while a minor leak would merely cause them to lose consciousness on the way to their demise.
Originally Posted By: MinamiKotaro
The passengers would "merely" suffocate.
Like they would inside an airplane. There are mature technologies to deal with that.
Originally Posted By: fdcg27
You want a better air travel experience?
Pay to sit up front. The difference in cost, especially considering bag fees is sometimes not all that much but the overall experience is so much more pleasant from check-in to debarkation.
An international config aircraft up front is really blissful.
Depends on the distance and population density, there are other choices like high speed rail. HSR has replaced many European and Asian airline routes cost effectively, and they are much more comfortable and convenient than economy class flights. Evacuated tube is likely not going to happen on low density routes, and would likely need to have cargo capacity to keep the route occupied all the time to make it cost effective.
The passengers would "merely" suffocate.
Like they would inside an airplane. There are mature technologies to deal with that.
Originally Posted By: fdcg27
You want a better air travel experience?
Pay to sit up front. The difference in cost, especially considering bag fees is sometimes not all that much but the overall experience is so much more pleasant from check-in to debarkation.
An international config aircraft up front is really blissful.
Depends on the distance and population density, there are other choices like high speed rail. HSR has replaced many European and Asian airline routes cost effectively, and they are much more comfortable and convenient than economy class flights. Evacuated tube is likely not going to happen on low density routes, and would likely need to have cargo capacity to keep the route occupied all the time to make it cost effective.
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Originally Posted By: PandaBear
Originally Posted By: MinamiKotaro
The passengers would "merely" suffocate.
Like they would inside an airplane. There are mature technologies to deal with that.
What technologies would those be?
Just curious. When an airplane loses pressurization, the outside pressure is about 25KPa (vs. 100KPa at sea level). Instant vacuum is far, far worse than a depressurization at 35,000 feet.
Further, the airplane is going to descend, rapidly, to an altitude at which breathing is possible.
This isn't possible inside the evacuated tube. It has to maintain vacuum to function.
So, what mature technologies exist to allow people to survive in a vacuum for the length of the trip?
Current O2 masks won't work. Within seconds, our tube passengers will be suffocating, because they can't inhale (there's a vacuum outside their lungs, so inside their lungs won't be lower pressure, as it is ordinarily). They will be continually exhaling, unless they can get a high pressure mask, which isn't commercially available. If they survive those few seconds and don the pressure mask, they might not have their lungs rupture from the internal pressure.
Then, they merely have to deal with the phase transition of the water in their blood and tissues from liquid to gas... At that low a pressure, depending on temperature, a condition called ebullism,will cause tissue swelling and bruising due to the formation of water vapor under the skin; at worst, it can give rise to an embolism, or blood vessel blockage due to gas bubbles in the bloodstream.
So, sure, they could wear pressure suits, like military pilots do above 50,000', which would require some training and careful (read: expensive) fitting, and then they could survive decompression of the "car" in the tube...but it's not exactly viable, or mature, technology...
Originally Posted By: MinamiKotaro
The passengers would "merely" suffocate.
Like they would inside an airplane. There are mature technologies to deal with that.
What technologies would those be?
Just curious. When an airplane loses pressurization, the outside pressure is about 25KPa (vs. 100KPa at sea level). Instant vacuum is far, far worse than a depressurization at 35,000 feet.
Further, the airplane is going to descend, rapidly, to an altitude at which breathing is possible.
This isn't possible inside the evacuated tube. It has to maintain vacuum to function.
So, what mature technologies exist to allow people to survive in a vacuum for the length of the trip?
Current O2 masks won't work. Within seconds, our tube passengers will be suffocating, because they can't inhale (there's a vacuum outside their lungs, so inside their lungs won't be lower pressure, as it is ordinarily). They will be continually exhaling, unless they can get a high pressure mask, which isn't commercially available. If they survive those few seconds and don the pressure mask, they might not have their lungs rupture from the internal pressure.
Then, they merely have to deal with the phase transition of the water in their blood and tissues from liquid to gas... At that low a pressure, depending on temperature, a condition called ebullism,will cause tissue swelling and bruising due to the formation of water vapor under the skin; at worst, it can give rise to an embolism, or blood vessel blockage due to gas bubbles in the bloodstream.
So, sure, they could wear pressure suits, like military pilots do above 50,000', which would require some training and careful (read: expensive) fitting, and then they could survive decompression of the "car" in the tube...but it's not exactly viable, or mature, technology...
Explosively eye-popping technology
Originally Posted By: PeterPolyol
Explosively eye-popping technology
Not likely. Most would just black out within seconds and then suffocate. There was a NASA subject testing out equipment in a near vacuum. He lost his hose that gave him air and he was subjected to the near-vacuum for 30 seconds before the vacuum was broken and someone gave him emergency oxygen. He didn't suffer an long-lasting effects.
http://www.popularmechanics.com/space/a24127/nasa-vacuum-exposure/
There had been one case where someone in space had a hole in his suit.
Explosively eye-popping technology
Not likely. Most would just black out within seconds and then suffocate. There was a NASA subject testing out equipment in a near vacuum. He lost his hose that gave him air and he was subjected to the near-vacuum for 30 seconds before the vacuum was broken and someone gave him emergency oxygen. He didn't suffer an long-lasting effects.
http://www.popularmechanics.com/space/a24127/nasa-vacuum-exposure/
There had been one case where someone in space had a hole in his suit.
Dead in 90 seconds!
Now that you think of it the only things that'll 'blow up' are the gasses in the body. I'd imagine perhaps abdominal bloating or instant tooting/belching depending on the easiest exit... and then the fatal dissociation of dissolved gasses from all cells... a good time all around.
Can you imagine, an entire track of 'vacuum tube' is a heck of a lot of volume to re-pressurize in an emergency. One exploding car would barely affect the total vacuum and the occupants would surely perish in agony, without some type of safety isolation.
Now that you think of it the only things that'll 'blow up' are the gasses in the body. I'd imagine perhaps abdominal bloating or instant tooting/belching depending on the easiest exit... and then the fatal dissociation of dissolved gasses from all cells... a good time all around.
Can you imagine, an entire track of 'vacuum tube' is a heck of a lot of volume to re-pressurize in an emergency. One exploding car would barely affect the total vacuum and the occupants would surely perish in agony, without some type of safety isolation.
Originally Posted By: PeterPolyol
Dead in 90 seconds!
Now that you think of it the only things that'll 'blow up' are the gasses in the body. I'd imagine perhaps abdominal bloating or instant tooting/belching depending on the easiest exit... and then the fatal dissociation of dissolved gasses from all cells... a good time all around.
Can you imagine, an entire track of 'vacuum tube' is a heck of a lot of volume to re-pressurize in an emergency. One exploding car would barely affect the total vacuum and the occupants would surely perish in agony, without some type of safety isolation.
Isn't the concept that it's a relative vacuum in front pushed along by air from behind? A lot of the proposals don't include a system where it's a total vacuum.
Dead in 90 seconds!
Now that you think of it the only things that'll 'blow up' are the gasses in the body. I'd imagine perhaps abdominal bloating or instant tooting/belching depending on the easiest exit... and then the fatal dissociation of dissolved gasses from all cells... a good time all around.
Can you imagine, an entire track of 'vacuum tube' is a heck of a lot of volume to re-pressurize in an emergency. One exploding car would barely affect the total vacuum and the occupants would surely perish in agony, without some type of safety isolation.
Isn't the concept that it's a relative vacuum in front pushed along by air from behind? A lot of the proposals don't include a system where it's a total vacuum.
My guess is that no one alive today will still be alive when this new means of transportation becomes mainstream with travel back and forth between many major cities is on a regular schedule.
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