5 ms·

The environmental issue with air travel is not high fuel consumption per passenger mile, but the number of miles per passenger. A coast to coast trip by car mig

by usrusr 2y ago

The environmental issue with air travel is not high fuel consumption per passenger mile, but the number of miles per passenger. A coast to coast trip by car might burn just as much fuel as coast to coast by plane, but people simply wouldn't to that all that often in a lifetime. That's for medium and long distance travel, short distance fuel consumption per passenger mile goes up dramatically. OT: this is actually a point where I see a big, unserved gap in the market of climate-aware air travel. A feeder plane (from regional to intercontinental airport) dedicated to the market segment of "going by road or train might be roughly as fast, but I need to go to the airport and I can't risk missing my connection due to the unpredictable nature of ground travel". So you'd want a something the size of a CRJ or even just a dash-8, but ruthlessly optimized for fuel consumption. That would imply going slower (no issue at all when the time for bording etc greatly outweighs the time spent in the air!) which would imply moving the deep point in that induced vs parasitic drag diagram as far left as possible, which would imply going wild with wingspan, something sleek, carbon, like a performance glider, as wide as a 737 or beyond. One reason I've heard suggested for why this doesn't yet exist is that on those short hops (little time spent in the air), fuel cost is actually outweighed by crew cost so much that all the cost saving from lower fuel consumption would be eaten by getting less trips per crew-day. So it's an automaton problem in disguise? Or a regulatory problem?

notahacker 2y ago
For that sort of range hydrogen electric is also starting to look viable
- usrusr 2y ago
  Hydrogen electric is little more than greenwashing before we have anything resembling a hydrogen surplus on the horizon. Energy density is always an issue in flying applications and it's well possible that a boring old turboprop burning efuels (made from that very same hydrogen surplus) would be the clear winner. Losses of the transformation pipeline vs losses from carrying the most impractical fuel type ever tried. Minimizing the energy requirement at the final conversion step is an important thing all too often missed in the frenzy of converting the path to get there.
Swenrekcah 2y ago
I want the world to move to a system of very large and spacious and cool aircraft for major hub-to-hub travel, and then nice and comfortable high speed rail from hub to destination. I’m tired of cramming into a narrowbody with no service. Let me fly on an engineering marvel like the A380 or 747 and then relax or work in a comfortable train seat.
- aghastnj 2y ago
  We've got that, already. They're called "trains." We just need to make them faster.
- ramses0 2y ago
  The real answer is "wings clipped to tubes". Load the cheap tube at your leisure, drag it by semi under the waiting "wing". Clip, clip, vroom... There was a great concept video of a train/bus station that did something similar, divorcing the loading of people into the tube from the attaching the tube to the train. It allowed the train to keep going nearly 100% full speed, "magically" grabbing the tube loaded with passengers, and letting them pass into the moving portion (below) without stopping the train. The passenger pickup capsule was then dropped off at the next station for the process to repeat. See dead links here: https://www.smithsonianmag.com/innovation/this-high-speed-train-picks-up-passengers-without-having-to-stop-180948281/ https://www.smithsonianmag.com/innovation/this-high-speed-tr... Saves kinetic energy (no stopping and starting), and time because you're not incurring +5min per each stop/station.
  - usrusr 2y ago
    That's an age-old fantasy technology. Today you'd do it with electric buses(/trucks) that run on dedicated highways, or at least on dedicated lanes that are not only electrified (bus operates from a pair of pantigraphs except for that "last mile" part of the trip in regular roads or when there is some maintenance situation), but also exclusively run computer controlled in paceline formations. No physical connection (or perhaps physical connection for power crossfeed, to share pantograph wear, but no physical connection for push/pull), just a low latency, ack-heavy data link so that they would all accelerate and brake perfectly synchronized. Those buses (or trucks) would benefit from slipstream just like train cars do, but still be able to independently branch away or join at any exit. Of course the power bill would have to be shared by the whole formation, no need to rotate the lead (like a bicycle paceline would do) except perhaps in an unelectrified segment or during a power outage. This would offer point to point connections, have all the efficiency benefits of trains except for the energy cost of rubber-on-tarmac relative to steel-on-steel, and would also offer greatly increased throughout compared to trains because a formation like that would retain almost all of the emergency breaking capability of trucks (and realistically speaking, have better capability than a queue of human-operated trucks that keep almost but not quite enough safety distance for human reaction). The only reason I see why this is not the obvious future is that it requires enormous critical mass to pick up. It probably needs electric trucks first, then electric trucks with pantograph on some main lines, and only then pantograph electric trucks joining into robotic pacelines at some even later point. (the absolute end game state of course would be dedicated rights of way with a rail option useable to dual mode vehicles that could quickly drop on their road wheels not only for exiting formation but also for braking - note that breaking should not even exist in a formation like that, outside emergencies.

by usrusr 2y ago

notahacker 2y ago

For that sort of range hydrogen electric is also starting to look viable

usrusr 2y ago
Hydrogen electric is little more than greenwashing before we have anything resembling a hydrogen surplus on the horizon. Energy density is always an issue in flying applications and it's well possible that a boring old turboprop burning efuels (made from that very same hydrogen surplus) would be the clear winner. Losses of the transformation pipeline vs losses from carrying the most impractical fuel type ever tried. Minimizing the energy requirement at the final conversion step is an important thing all too often missed in the frenzy of converting the path to get there.

Swenrekcah 2y ago

I want the world to move to a system of very large and spacious and cool aircraft for major hub-to-hub travel, and then nice and comfortable high speed rail from hub to destination. I’m tired of cramming into a narrowbody with no service. Let me fly on an engineering marvel like the A380 or 747 and then relax or work in a comfortable train seat.

aghastnj 2y ago
We've got that, already. They're called "trains." We just need to make them faster.
ramses0 2y ago
The real answer is "wings clipped to tubes". Load the cheap tube at your leisure, drag it by semi under the waiting "wing". Clip, clip, vroom... There was a great concept video of a train/bus station that did something similar, divorcing the loading of people into the tube from the attaching the tube to the train. It allowed the train to keep going nearly 100% full speed, "magically" grabbing the tube loaded with passengers, and letting them pass into the moving portion (below) without stopping the train. The passenger pickup capsule was then dropped off at the next station for the process to repeat. See dead links here: https://www.smithsonianmag.com/innovation/this-high-speed-train-picks-up-passengers-without-having-to-stop-180948281/ https://www.smithsonianmag.com/innovation/this-high-speed-tr... Saves kinetic energy (no stopping and starting), and time because you're not incurring +5min per each stop/station.
- usrusr 2y ago
  That's an age-old fantasy technology. Today you'd do it with electric buses(/trucks) that run on dedicated highways, or at least on dedicated lanes that are not only electrified (bus operates from a pair of pantigraphs except for that "last mile" part of the trip in regular roads or when there is some maintenance situation), but also exclusively run computer controlled in paceline formations. No physical connection (or perhaps physical connection for power crossfeed, to share pantograph wear, but no physical connection for push/pull), just a low latency, ack-heavy data link so that they would all accelerate and brake perfectly synchronized. Those buses (or trucks) would benefit from slipstream just like train cars do, but still be able to independently branch away or join at any exit. Of course the power bill would have to be shared by the whole formation, no need to rotate the lead (like a bicycle paceline would do) except perhaps in an unelectrified segment or during a power outage. This would offer point to point connections, have all the efficiency benefits of trains except for the energy cost of rubber-on-tarmac relative to steel-on-steel, and would also offer greatly increased throughout compared to trains because a formation like that would retain almost all of the emergency breaking capability of trucks (and realistically speaking, have better capability than a queue of human-operated trucks that keep almost but not quite enough safety distance for human reaction). The only reason I see why this is not the obvious future is that it requires enormous critical mass to pick up. It probably needs electric trucks first, then electric trucks with pantograph on some main lines, and only then pantograph electric trucks joining into robotic pacelines at some even later point. (the absolute end game state of course would be dedicated rights of way with a rail option useable to dual mode vehicles that could quickly drop on their road wheels not only for exiting formation but also for braking - note that breaking should not even exist in a formation like that, outside emergencies.