HSTEd
Veteran Member
- Joined
- 14 Jul 2011
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Honestly I think things like ThyssenKrupp's MULTI are the future - you can make lifts that can act as Personal Rapid Transit!
Honestly I think things like ThyssenKrupp's MULTI are the future - you can make lifts that can act as Personal Rapid Transit!
Going back to this, you're also massively underestimating (justified) NIMBYism. People want to be able to sit out on balconies and roof terraces and enjoy being outside. The laws of aerodynamics mean that EVTOLs are never, ever going to be silent. Moving sufficient air around to keep any meaningful load in the sky will always cause significant noise somewhere, no matter how sophisticated the rest of the technology can be. With EVTOLs filling the skies in dense cities, it would be actively unpleasant to be outside. We would have just got rid of polluting and noisy internal combustion vehicles that affect only the ground, and replaced them with things which affect everything! Indeed, for the bankers and their penthouse balconies and terraces, things would be actively worse than before.
Again, the alternative is underground railways and other guided transportation mechanisms. In tunnels these cause very little noise at all. The only impact on the human environment are the entrances and exits to stations, which are and can be integrated pleasantly into other everyday features of urban areas. Would you have ever known the Victoria line and Crossrail 2 are routed essentially beneath Buckingham Palace? Or the Jubilee Line underneath Big Ben?
HSTE'd you don't seem to be getting the business model.
As a passenger you are effectively getting on public transport, the E-VTOL craft can go from one approved and designated place to another via a route that is approved and evaluated for safety. The passenger will not have a method of adjusting where the craft goes.
Routes can be easily selected so that craft will not be flying over the few places where people stand around outside in any level of density. That may mean that landing pads cannot be that close to certain places but that would not compromise the utility of such a system. The LA system set out by Uber only needed 40 nodes to move millions of people.
You won't be getting on these craft unsupervised, you won't be allowed to carry anything bigger than hand luggage.
This I actually agree with, provided they can get the horizontal speed up to ~15-20mph and come up with some method by which the pod get up to speed off the main route.
Routes can be easily selected so that craft will not be flying over the few places where people stand around outside in any level of density.
The noise profile is somewhat different to ground transport, once these things are up at around 100m or so they cease to be audible over the background noise in most cities. Over 1000m and they won't be audible in the countryside.
It is therefore preferable to ground based transport which is the majority of transport in most cities, an EVTOL in the sky is quieter than being near to a busy road.
In London Uber was suggesting that the river would be a sensible location to use for landing pads, you can ascend and descend over the water you'd have some of the tall buildings with landing pads on the roof, nobody goes outside on the top of canary wharf. Existing large railway stations also have a noise profile and footprint that EVTOL's could operate in.
Don't get me wrong, I don't think such a service would fully obsolete the underground, where density is sufficiently great to support digging tunnels the above ground infrastructure is probably close enough packed to make landing difficult unless there is a handy 50 story building nearby.
It's also worth pointing out that Uber is only estimating that around 10% of journeys in greater LA would be carried out by this method. In all likelihood a new form of transport will really be transformative because it will enable journeys between places that we currently don't think to do because the transport links aren't there.
But but but... an app developer with no IP called Uber says it will work and have done some snazzy renderings to prove it!!Two words - energy density. Assuming the electric power is stored in a battery, the weight of any such batteries is going to put a severe limit on the number of passengers that can be carried. The energy density of fossil fuels is much higher than for a battery, and yet air taxis, light planes and helicopters are only used for short distances or by wealthy individuals, and have not proved competitive with mass surface transportation or with cars. The whole thing is a libertarian fantasy.
Two words - energy density. Assuming the electric power is stored in a battery, the weight of any such batteries is going to put a severe limit on the number of passengers that can be carried. The energy density of fossil fuels is much higher than for a battery, and yet air taxis, light planes and helicopters are only used for short distances or by wealthy individuals, and have not proved competitive with mass surface transportation or with cars. The whole thing is a libertarian fantasy.
But but but... an app developer with no IP called Uber says it will work and have done some snazzy renderings to prove it!!
Capacity is a big issue here, surely.
A worked example would be if we had 20 seat models each FATO would be around 30m square and would have a 60 second interval. Birmingham New Street handles around 15,000 passengers per hour. We would only actually need 12 FATO's to cover this demand.
Pretty easy to work out:
A 20 seat aircraft is likely to weigh in the region of 10-12,000kg and have an L/D of 20-35 depending on configuration chosen and whether or not it is a VTOL aircraft. This results in a per passenger energy usage of 140-295 KJ/km about the same as high speed rail. Or a range of 0.5-1p per km in electricity costs even using 12p/kwh retail electricity.
Depends, for E-VTOL you can keep on stacking landing pads at a vertiport in a vertical direction, as I've alluded to previously that will get the passengers be hour equivalent to a major station with less footprint than an above ground station. In very dense urban areas you will probably still use undergrounds but they might actually be used as a last mile option for journeys fed from an E-VTOL network connecting suburbs.
However the original post was about a 20-50 seat regional aircraft replacing high speed rail. Short answer is high speed rail cannot come close, in the UK context a 20-50 seat "Airbus" can cover pretty much any city pair. The sky has essentially unlimited capacity particularly as we are not concentrating all the take offs and landing into a limited number of airports.
The ground infrastructure isn't that difficult, the aircraft have relatively light weights so Final Approach and Take Off (FATO)'s can be located on roofs of structures. A very high capacity design would have aircraft taking off from multiple levels as well as a ground level usage, for example in Birmingham you could could built it over the top of the wholesale market.
A worked example would be if we had 20 seat models each FATO would be around 30m square and would have a 60 second interval. Birmingham New Street handles around 15,000 passengers per hour. We would only actually need 12 FATO's to cover this demand.
That would in theory be an area 120*90m but lets assume it will actually be around 180*120m and that we will be stacking the aircraft vertically during embarkation. We could quite easily fit such a structure on to the the Curzon Street Station area.
Do we really want our skies full of aircraft though?
Meaning more wasted power than trains.The aerial traffic jams in the Star Wars prequel trilogy spring to mind.