Is it possible to emit a small plasma field to eliminate air in front of the vehicle? How much power is needed?
Will we ever fly supersonically over land?
181–190 of 220 posts
Re: Will we ever fly supersonically over land?
#182Earlier quoted context omitted.
Do you have a citation for that? Quick Googling doesn't reveal any obvious authoritative answers (but a ton of guessing and unsubstantiated claims). The most authoritative/unbiased source seems to be this Wikipedia article: https://en.wikipedia.org/wiki/Energy_efficiency_in_transport But the head-to-head comparisons are mostly gaps when it comes to trains, and the sections on trains and planes are in completely diffe…
It was covered in a sustainable engineering class I took. There's not much generic into about it because every rail route proposal is different, even between the same destinations. Depends a lot on geography and what's already there. You basically need to do a full Life Cycle Analysis (LCA) for each route. Sometimes they're included in the EIS for a proposed project. That's prob the best place to start. But there's a…
Thanks. Is there at least some kind of super-elementary comparison?
E.g. energy consumption per-passenger-mile for a fully occupied Japanese bullet train while moving at maximum speed, versus for a fully occupied Boeing 737 at cruising altitude?
Obviously there are a million other factors, like takeoffs and landings, and trains stopping, as well as fuel vs electric, but wondering about even just the most basic operation.
Re: Will we ever fly supersonically over land?
#183Earlier quoted context omitted.
> I live in Southern California, with family in Kansas, Wisconsin, and New York. The closest one is 2500kms away. The longest is almost 5000kms A train would take a lot longer than a plane. Perhaps people/families have spread themselves all over the continent because in the past energy has been 'too cheap' (i.e., didn't price in externalities). With carbon pricing people may make different decisions in how far they w…
Travel is extremely economically important, especially for the poor. Living in a poor, rural county with poor schools and few jobs can really mess things up. Someone I know is getting divorced. She was a very high earner who moved to a low-cost of living, low wage area to be with her husbands family. She had previously earned very high wages, but took a significant pay cut to live with in-laws. As the divorce is conc…
> Travel is extremely economically important, especially for the poor.
"Travel" or "movement"?
I am the first generation to be born in the country I live in. When my (grand)parents left, they left under the assumption that there would be no, or maybe very little, chance of going back to the Old Country. They took a boat over the course of many weeks to traverse an ocean; an era before cheap air travel.
When people move in the future, to hopefully have a better life than where they current are, it may be that they may not be able to go back (as easily) to where they came from.
The fact that we can now travel back and forth cheaply over great distances could simply be a temporary blip in human history, and we should perhaps consider this era could be ending. You can still move, but it will be more 'permanent' going forward, and travel is will be less frequent/easy/cheap/etc.
Re: Will we ever fly supersonically over land?
#184Earlier quoted context omitted.
Military supersonic flight over land in the US is supposed to only happen over unpopulated areas. Having lived near a coastline (~1 mile from the shoreline) along a military flight path, I know they occasionally went a little early.
How loud was it and how often did you experience it?
F-104 going supersonic at something like 500ft or slightly lower within less than a mile feels like a full body slap which makes the parts of your clothing which are not tight flutter. Anything a few thousands feet up is still very loud but doesn't do the slapping and fluttering anymore. Anything a few 10.000 feet can still be very loud. Though it varies. Don't know on what it depends exactly. Had 4 in row making nice contrails high up, rather soft. Had single ones, also high up, making a contrail, banging loud and sharp, thinking why was that? Those are all memories from the 80ies. Can't remember when I heard the last supersonic boom anymore. Has to be early 90ies. Today I laugh when I read about people calling the emergency services when they heard one ;-)
Re: Will we ever fly supersonically over land?
#185Earlier quoted context omitted.
But are they that much worse than private jets and helicopters on a per person level?
Flying, in-general, is inefficient unless it's a large, lifting body in ground effect.
Maybe one time we manage to use something similar while flying supersonic with https://en.wikipedia.org/wiki/Compression_lift
Re: Will we ever fly supersonically over land?
#186Earlier quoted context omitted.
Flying on a full or almost-full plane is more carbon efficient than driving solo. And that's not taking into account the cost of the road networks we build and maintain to allow high volumes of vehicular traffic. https://yaleclimateconnections.org/2015/09/evolving-climate-...
> Flying on a full or almost-full plane is more carbon efficient than driving solo. … in a fossil-fuel burning automobile. Do things changes with the rise of EVs?
Depends on where the electricity is coming from, and debatable if you account for all the externalities in producing the batteries, solar cells for photovoltaics, rare earth mining for magnets, and countless other stuff for way more silicon needed to regulate all that stuff to work efficiently together. Be it for in vehicle control, or smart grid.
Re: Will we ever fly supersonically over land?
#187They will still use an enormous amount of fuel, carry fewer passengers, and heavily pollute the environment. I'm not too excited about the prospects.
All overland passenger transport should be rail. Over the oceans I suppose we should strive for ships and dirigibles. That said, I find it hard to believe that plane travel can be eradicated for e.g. diplomacy. And frankly, if frequent contract between the powerful different countries is needed to avoid e.g. world wars, it's is worth it. In the short term, any carbon we can capture needs to go in back in ground and s…
One could imagine submerged floating rail tunnels for going over the oceans by rail. Say about 30 to 50 meters deep to be isolated from the weather, not disturbing the remaining shipping. Also usable as sensor platform, carrier for fiber optics. And enabler for floating cities, resorts, aqua-, wind-, and wave-farms out there.
Re: Will we ever fly supersonically over land?
#188Earlier quoted context omitted.
Travel is extremely economically important, especially for the poor. Living in a poor, rural county with poor schools and few jobs can really mess things up. Someone I know is getting divorced. She was a very high earner who moved to a low-cost of living, low wage area to be with her husbands family. She had previously earned very high wages, but took a significant pay cut to live with in-laws. As the divorce is conc…
> Travel is extremely economically important, especially for the poor. "Travel" or "movement"? I am the first generation to be born in the country I live in. When my (grand)parents left, they left under the assumption that there would be no, or maybe very little, chance of going back to the Old Country. They took a boat over the course of many weeks to traverse an ocean; an era before cheap air travel. When people mo…
Unless you can move your entire family, then movement implies travel at least twice a year in the US.
Re: Will we ever fly supersonically over land?
#189Earlier quoted context omitted.
Train costs are sensitive to sparsely populated regions. As long as there is a sufficiently large city every hour or so, distances don't really matter. Multi-track railways are common near major cities. They are not that expensive, because adding another set of tracks increases the width of the corridor only marginally. The airline equivalent of a new set of tracks is building a new runway. Because that's often impos…
"Multi-track railways are common near major cities. They are not that expensive, because adding another set of tracks increases the width of the corridor only marginally." About a quarter of all railway passengers in Czechia take the suburban trains around Prague. We sorely need extra sets of tracks from all directions, because the current tracks are overloaded. Especially the faster trains from other regions do not…
Do it as subways in a way like the new lines in Barcelona did.
edit: By that I mean something like illustrated here https://ca.wikipedia.org/wiki/L%C3%ADnia_9_del_metro_de_Barc...
Make them 15 to 16 meters in diameter to be usable by any train, or use 2 of them side by side. Problem mostly solved.
Re: Will we ever fly supersonically over land?
#190Earlier quoted context omitted.
Air travel has a big PR problem, because somehow a lot of people think it's the absolute worst for the environment. While on many routes a car is worse in terms of CO2 emission per trip than a small to mid sized airliner if there are less than 3 people in the car. Similar for your suggestion that we should take ships over the ocean, because cruise ships are much more polluting per passenger mile than modern airliners…
On the the other hand commercial air travel is one of the safest means of travel. If you wanted to optimize for safety you would take a scheduled flight to your destination than go by road.
Ah, well. You think so. But would that hold up if traveling by air so much more, for so many shorter trips? What could go wrong?