My idea for electric planes instead of high speed rail

Discussion in 'Other Public Transport' started by Technologist, 29 May 2018.

  1. Technologist

    Technologist Member

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    Here is where it falls down: No creativity in terms of looking at broader developments, it simply assumes that high speed rail is needed, not entirely surprising given who wrote it.

    Here is the actual answer:

    [​IMG]

    This is a 5 seat variant but enlarge such a thing to 20 seats and ranges of 600-1000km are achievable with current batteries. Short haul airlines are generally cheaper than railways per mile at the moment, electric aircraft are going to be transformative to the cost of flying as the parts such as motors, controllers and batteries are all commodity items and people like McLaren have got the cost per kg of carbon fibre structures down to levels acceptable for medium volume production. Operational costs are low as these vehicles have very few moving parts.

    Why would anyone want to build a piece of expensive fixed infrastructure when you can fly point to point?

    This one is being developed by a Boeing subsidiary, this is just electric without attempting VTOL too.

    [​IMG]

    Air traffic control issues are being solved by IP based systems and are being tested on drone deliveries right now. These things are much quieter than helicopters and rapidly move to forward flight on the wings where they are very quiet due to not having an engine. Also most helicopter "noise" is actually annoyance at the people using them, once people are able to actually fly in these things expect public acceptance to go up greatly.

    I imagine some will be saying "but it will never happen", here is a prototype flying earlier this year, the rate of progress is high and the regulator is on board.

    [​IMG]
    [​IMG]
     
    Last edited: 29 May 2018
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  3. The Planner

    The Planner Established Member

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    So how many of those would you need to carry the equivalent of a HS2 train? By my reckoning you will need a good 25 to cover an 11 car Pendo.
     
  4. NSEFAN

    NSEFAN Established Member

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    I dare say that even with the best power electronics, the basic physics of rail and air travel will mean that a high speed train uses less energy per passenger to make that journey compared to the aircraft shown. As electricity becomes more and more precious this is a serious consideration!
     
  5. Technologist

    Technologist Member

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    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.
     
  6. NSEFAN

    NSEFAN Established Member

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    Is that including the gains to be had with regenerative braking?
     
  7. Technologist

    Technologist Member

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    But there is no requirement for them to fly in formation or go to the same place or fly half empty!

    Most likely an extension to an Uber like app would aggregate demand and schedule flights dependant on how flexible people are on their timings and how much they are prepared to pay. Uber used their ride data to calculate that around 25% of Los Angles passenger miles could be by air and actually pathed this.

    Given this was with 4 person vehicles covering the UK's rail journey's longer than 50 miles with 20 seat vehicles will be pretty easy.

    As far as station capacity goes Uber got some architects to design skyports for the smaller 4-5 seat E-VTOL craft. They managed to design a 5000 passenger per hour structure that fits onto a 3 acre site, that includes a 5 minute quick charge per vehicle, the key element is that landing and take-off pads can be stacked.

    This one was by ARUP:

    [​IMG]

    Key element is that they can start the service off flying from existing heliports and the roofs of car parks before they need to build the big ports shown above.
     
  8. Technologist

    Technologist Member

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    Nope that's just a pure at cruise number, take-off and landing are more energy intensive as is climb however both a pretty brief.

    E-VTOL's are likely to fly at around 500-1500m, regional electric aircraft are more likely to fly at 1500-4000m. That Zunum aircraft will likely fly more like 5000-10000m.

    I think the key point is that energy costs of electric flying are likely to be very small!
     
  9. NotATrainspott

    NotATrainspott Established Member

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    Technologist, 5000 passengers an hour is pitiful. An Elizabeth line train will carry 1500 people in total and you can run them at two minute intervals. HS2 will be up to 1100 people on a 400m double set just about every three minutes. To support a tiny fraction of the number of people an hour, you need three acres of ground space and significant restrictions on building heights and plans nearby. For rail, you can bury the whole thing underground and leave essentially no impact on the urban or natural environment.

    A lot of these radical new technologies come out of Silicon Valley, which is an incredibly low-density part of the world for how economically powerful it is. Some of the ideas that engineers have there when sitting in traffic jams on the interstate network simply don't apply in world cities, because the urban environment and style of living is so incredibly different. You don't need to schedule an Uber when you are travelling on a route so well travelled that there's a train running every two minutes. You don't need drones to deliver goods to apartments in tower blocks so large they can almost justify having a distribution centre underneath them or next to them.

    The other factor to consider is that not every journey actually needs to be as fast as possible. Sure, average journeys have got faster over time as we've moved from horse and cart to internal combustion and motorways, but we're finding that lots of people don't mind going slower if it means things are cheaper. There's a thriving market for low-cost but slow coach travel between towns and cities which have fast rail links between them. Not everyone is in a hurry to get places. If they're not in a hurry, they won't pay any premium for going faster than they need to.
     
  10. Technologist

    Technologist Member

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    5000 passengers per hour is around 15.6 million passengers per year, (assuming 20 hour operation, a peak to average ratio of 50% and 50% capacity at the weekend) this would put such as station in the top 20% of London underground stations. There is no reason why such a Skyport could not be vertically stacked in which case it would have a capacity about equal to Baker street on the underground. In practice most such stations would be built on the roofs of existing buildings.

    This presentation shows how they planned out a system at scale for LA

    My point wasn't that Uber Elevate will kill underground systems, it might reshape them significantly though and will probably significantly reshape suburban and rural settings.

    My point was that electric regional aircraft will murder high speed rail, it's faster, point to point, works at lower volumes and for smaller towns and as it doesn't need massive infrastructure planning much faster to implement. Since it's electric you take out the environmental arguments and if its VTOL you loose rails advantage of being down town.

    Re: Cost; the assumption that flying is expensive is generally down to the fact that helicopters and general aviation are expensive. When you look at scheduled flying you find that its often cheaper than unsubsidised costs per mile for trains and that as planes go so much faster their purchase price per seat/km per day is lower than that for trains.

    Uber's plans are that initially the 4 seat E-VTOLs will be around $1 million but dropping to around $250,000 once the volumes get up to 5,000 per year. My fag packet calculation is that a typical E-VTOL will fly around 3.5 million miles per year, so that is only ~7-29p per mile assuming it lasts 10 years. The most expensive cost will be the pilot, which means that initially the cost per mile will be similar to a taxi as you will have to pay for the pilot's wages however it is split between 4 people and as it moves faster his higher pay is spread over more flights per hour. The eventual cost target once automated is the marginal cost of using a private car around 45 cents per mile. The same economic argument applies when the vehicle is scaled up and the flight is Birmingham to Newcastle.
     
  11. The Ham

    The Ham Established Member

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    There's two problems with such a "service" by electric aircraft:
    - where they need to move about in densely populated areas either due to the amount of airspace that they need or due to the rules associated with flying (for instance any aircraft that flies within London needs two engines)
    - where someone is going away from where travel would likely result in a return journey or beyond the range of the aircraft

    It could work well in somewhere like a small city or large town, but it almost certainly wouldn't work well within London and almost certainly not within Central London.

    Likewise, if I were wanting to go somewhere that was an hour away that's well outside of the 10,000m (10km) range that was started upthread. If I've got to fly for 5 minutes, charge for 5 minutes the flight speed would be to be double that of a car.

    What happens if I want to take one from an urban area at say 8am for an hour out to a rural area? The cost is going to be high as during that two hour window it could have done a lot of short hops, whilst I've taken it to somewhere where it may not be able to recharge and is very unlike to find anyone to use it going somewhere else. As such I'll be charged a lot for the privilege making it not viable.

    The problem that you forget is that one hub building wouldn't be in isolation, they would need to be located about 400-1,000m apart (ideal walk distance to a bus stop or train station) otherwise people would need to use another mode of travel to get to the hub (in which case they may week be better off using that mode to get to where they are going), as such the maximum capacity of each hub drops as there's going to aircraft needing to fly past.

    Also a lot of people live/work near ground level, so you need to factor in journey time for getting from the top of the hub to ground level to get to where you are going (or from the 4th floor upto the roof where there's a landing point on the 12th floor).

    I'm not convinced that flying taxis are likely to be cheap enough to compete with rail for a long time (bearing in mind that none exist now, not even at some crazy £20 a mile charge. Which some people would pay in somewhere like London where there's a lot of traffic congestion and there's a lot of fairly wealthy people who would think that using such a status symbol would look good).

    There maybe a future, but I would think that it's 50 years away before it's something that starts to be viable, let alone affordable for a lot of people.

    If for no other reason that you would need to have quite a good network of landing points before the public start to use it (a few individuals could use it once there's about 20 locations), but to get 5,000 people using one hub in an hour you'd need a network of 1,000 other hubs with an average number of users of 100 per hour. That's a lot of building of hubs before you start seeing significant returns.

    Even if you are using other people's roof space that's going to come at a cost, and not all flat roofs would be suitable.

    Then there's the rules about air traffic control, low down these aircraft would be needing to dodge drones, buildings, kites, etc. Some will be easy to avoid, others could pop up almost out of nowhere without warning.

    Given that you couldn't use them (at least when being manually controlled) near to runways, you're going to struggle to serve airports.

    Given travel hasn't moved forwards much in the last 50 years (a bit faster, able to move more people at once, able to do so more efficiently, but generally broadly the same) and even electric cars are still fairly uncommon, whilst automated cars are still almost non existent, I would expect that HS2 doesn't have anything to worry about for quite some time.
     
  12. HSTEd

    HSTEd Established Member

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    You are going to build 4 seat night-flight capable, instrument flight rules rated, aircraft, complying with all aircraft safety regulations, for $250,000?

    ..... yeah


    So they are going to be flying at an average speed of 400 miles per hour, every hour of the year? Including service time, charging time and time taken for passengers to embark and disembark?

    This seems somewhat challenging.... and where will all the landing capacity to deal with these things come from?
    What with this do to ATC resources?
     
  13. Shaw S Hunter

    Shaw S Hunter Established Member

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    It won't work in Central London at all. Helicopters are effectively banned from the heart of the city and all such traffic is confined to following the Thames with helipads all being close to the river. As for using existing rooftops, there is so much variety in building heights with a good deal of very high skyscrapers (and this is true of other cities too) that there will be somewhat reduced scope for "free flying": airways would inevitably be used to regulate traffic. The memory of 9/11 might also lead to a complete rejection of aircraft in such areas anyway.

    Government is also now looking to regulate the use of airspace by drones with a ceiling of 400-500m and a complete ban within 1km of existing airfields as well as a form of licensing for operators. Since commercial exploitation of drone technology is likely to happen rather more quickly than the development of passenger carrying electric aircraft it's almost inevitable that the latter will be confined to operating between airfields, at least within metropolitan areas. However such airfields would not necessarily have to be as large as a typical airport. As such the potential market for these vehicles is going to be limited.
     
  14. edwin_m

    edwin_m Veteran Member

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    What about security? Given that an electric drone would be much slower than a jet and probably little faster than a high speed train, even 30min extra for screening prior to boarding an aircraft would cancel out the speed benefit on most shorter journeys.
     
  15. Technologist

    Technologist Member

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    I copied the wrong number 3.5 million was for 10 years which is a conservative vehicles life. 350,000 miles a year was a more accurate and fairly conservative number. The vehicle cost contribution of 7-28p/m is still accurate.

    As for the $250,000 cost, think about this from first principles. The E-VTOL's weigh in the region of 800kg, they have around 200-300kg of lithium ion batteries (around $10,000 at current prices), some motors and a carbon fibre airframe.

    At scale they will need to produce 5-8000 vehicles a year, about the same output at McLaren or Aston Martin. If you look at the mass, complexity and materials they are very similar. Certification and QA processes become routine and low cost at high volumes. For reference $250,000 will buy you a GA aircraft today that weighs ~800kg. The first aircraft will still cost around $1 million but even at that cost E-VTOL flights will be affordable for most people as a one off and for many on a daily basis.

    ATC is currently being worked on in partnership with NASA, the system will be two fold, routes are plotted using similar methods to data in a server then once in flight the craft use sense and avoid systems. The key element is that the FAA is already running commercial trials with UAV's in urban aerospace, all the technology and standards will be directly transferable. The regulators are on board with this whole concept.
     
  16. Technologist

    Technologist Member

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    Current rules already permit much reduced security scanning for aircraft less than 20 seats flying internal routes, there is no need to search people flying on light aircraft. In the case of E-VTOL or electric regional aircraft there is no chance that the passengers will be able to take control of the aircraft and blowing it up is technically difficult and there are much easier ways of killing a small number of people.
     
  17. Technologist

    Technologist Member

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    You make lots of points, these are all addressed by Uber in their white paper or in much greater detail at either of their conferences. Their proceedings are worth watching.

    What is notable is that this isn't just Uber established people like Boeing, Airbus and Embraer are developing these things at pace. This isn't some silicon valley hype, the people running the Uber activities are all ex NASA senior leaders and the aviation technical press hasn't found any holes in their proposals.

    https://www.uber.com/info/elevate/summit/#elevate-summit-agenda

    Prototypes are flying today, experimental services by 2020 and fare paying customers by 2023, even if they are off by 100% they still beat HS2 to service and some time around 2020 the penny will probably drop for policy makers.

    My point is that even if the Uber E-VTOL doesn't take off as a suburban transport system the technology is applicable 20 seat VTOL aircraft which can duplicate high speed rail in terms of flying from urban areas, is at least 50% quicker and needs a tiny fraction of the infrastructure and can fly less popular routes.
     
  18. Technologist

    Technologist Member

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    Helicopters are banned for two reasons, one they look and occasionally are dangerous. Secondly they tend to have poor public perception (they are for example perceived to be much nosier than they actually are), as most people have never flown in one. E-VTOL will need to demonstrate significant safety advantages vs. a helicopter which is possible as their systems are redundant and more reliable (multiple electric fixed pitch propellers). They will also be substantially quieter and the dramatically lower costs than helicopters mean that most people can afford to experience them, once they are a normal everyday thing to do expect the public perception to change substantially.

    Don't get me wrong I think there will be substantial restrictions on usage and limitations on capacity to take-off and land in very densely populated areas or in low rise residential areas. The modelling is coming out that a standard mission would be around 15 miles so it probably isn't going to kill the tube, may well kill Southern Rail though.

    As for drones getting in the way 1: Flying cars are likely to trump commercial drones. 2: Commercial drones will be geo-tagged and there is also no reason why they can't use the same sense and avoid technology and be integrated into the ATC system. 3: Manual drones can either be regulated, geo-fenced or attacked by "peregrine falcon drones" which live at the Skyports. 4 The E-VTOL only fly at up to 300kmph they will be designed to shrug off the impact of an RC drone like they do bird strikes. For reference the E-VTOL system that was design to move 2.3 million people per day in greater Los Angles only had 40 nodes, so from a land use perspective that isn't that much infrastructure.
     
  19. Shaw S Hunter

    Shaw S Hunter Established Member

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    I won't respond in detail as we are in danger of getting too far off topic. What I will say is that your promotion about the possibilities of small electric aircraft is very obviously coming from an American perspective, that's to say from a place that has become inherently anti-rail and anti-regulation. Europe is very different. Railway networks are much better developed and enjoy a good deal of public support. Environmental sensitivities are also much stronger, just look at how many major airports work with night-time restrictions or curfews. It is telling you continually compare these aircraft to helicopters and then try to convince us that helicopters aren't noisy: I'm sorry but they most definitely are, not perhaps in absolute terms but in more general terms as they cruise at much lower altitudes than airliners. Even drones weighing only a few kilos can be quite intrusive at lower altitudes. I don't doubt that electric power will eventually be seen on aircraft but I don't believe the technology will be used in the way you suggest, at least not in Europe. In the meantime I also have no doubt that there will still be many more miles of high-speed rail route built in the next 2 or 3 decades both in the UK and on the continental mainland.
     
  20. Domh245

    Domh245 Established Member

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    Aerospace industry in "developing and backing future aerospace technologies" shocker - more at 11. Shouldn't really come as a surprise that the big hitters in the industry are backing their vision of the future, it's the same in the Automotive sector, and rail.

    I would argue that it is deserved. When I'm in London I'm right under the H7 Helicopter Route from Redhill to Barnes, and they're pretty loud, and even in Nottingham, the occasional air ambulance is a rude disturbance when I'm inside.


    In response to the general idea of mini drones, it depends if you are looking to provide a transport system that does near enough point to point rapid transit, or if you are looking to provide a system that gets people between certain locations quickly before they then go to their final destination. If it is the latter - the capacity of rail is unmatched, if it is the former, then space inefficient flying drones all around.
     
  21. NotATrainspott

    NotATrainspott Established Member

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    Not being able to put EVTOL systems underground is really a big problem. The drones themselves might not end up costing all that much but the ground infrastructure would cost a huge amount. Sure, rail infrastructure also costs a lot, but when it's underground, it doesn't actually block the land from being used for other productive purposes. Indeed, as is demonstrated well by major cities, bigger development on top often happens as a direct result of transport infrastructure being built underneath. Any EVTOL base is going to prevent other development from happening on that land, and land use is a zero-sum game. The cost of the system would have to take into account the opportunity cost of using that land for other, more productive purposes.

    Again, it's stinking like one of those US West Coast ideas unburdened by any realistic notion of urban planning. The Boring Company car skate idea is another one - it just doesn't make sense to carry cars around in tunnels in any city more dense than Los Angeles. The basic technological innovations involved are still pretty neat and have plenty of applications (these EVTOLs will make it easier to have air ambulances, and better tunnelling technology can be used for any transportation purpose) but the specific ideas aren't going to pan out.
     
  22. edwin_m

    edwin_m Veteran Member

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    That wouldn't apply if the craft were bigger as probably necessary. And I think if it was a significant mode of transport, whatever the size, then security would be a major issue for something that flies in large numbers at low altitude over cities.
     
  23. HSTEd

    HSTEd Established Member

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    A $250,000 GA aircraft is unlikely to have the plethora of sensors that are required in an all weather aircraft, including all the equipment necessary to make a landing in the dark (which will be required or you will be out of action for all but a handful of hours during the winter.

    Maybe the FAA is on board, but what the FAA thinks does not really matter that much in the UK, the CAA is historically much more restrictive of general aviation and technologies like this.
    And the Government will do it's nut about thousands of computer controlled aircraft flying in and out of major cities.

    What happens when one flies into the city filled with a couple hundred kilos of ANFO.
     
  24. The Ham

    The Ham Established Member

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    Blowing it up would be harder than a conventional aircraft as it would be pressurised and or wouldn't be carrying fuel.

    However if you could carry on board a large enough amount of explosives detonating that when in an area of lots of them could down quite a few and that in turn could cause damage to things on the ground or in buildings, especially if done so from height.

    There's the possibility of quite a lot of harm being done to quite a few people in such a scenario.

    Even going down a level of complexity, getting a gun (or guns) on board could allow someone to do something similar to a drive by shooting, but by doing damage to the propellers of other craft could lead to then crashing. Probably less of a problem in the UK, but certainly a problem in the USA.
     
  25. Royston Vasey

    Royston Vasey Established Member

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    A bit too much time spent on YouTube I think. Some nice ideas. Trying to cost and model such concepts on the back of a fag packet with vast implied assumptions about commodity pricing, volume manufacturing and scalability is fine but not very meaningful. Real world technology moves sursprisingly slowly. The railway is 200 years old and has changed little in concept in that time. It'll still be here in another 200. Flight journey times haven't changed since the Boeing 707 entered service 60 years ago and supersonic travel is an unaffordable pipe dream more now than when Concorde was actually flying.

    We can't even get a family car with an electric range further than 250 miles right now.

    It's so far in the future that we may as well cost up teleportation as an alternative to rail.

    Think about the source you rely on so heavily. Uber exists only to promote Uber. All the noise and presentation of themselves as tech pioneers is slick, the self driving cars eye-catching (though not remotely pioneering), but their purpose is to provide an app to allow people to get cars to drive them places as cheaply as possible and with the minimum safeguarding and employment standards they can get away with. They have an app and they promote that app. That's the be all and end all of what they do. No infrastructure, no vehicles, no property, no knowhow, no patents, no need to. This is all brand building.

    As far as authorities trusting Uber as custodians of any such infrastructure, it simply wouldn't happen. Aside from the lack of substance, IP, expertise and ethical practice in the company itself, they wouldn't have a clue how to deliver hard technology projects. They are still a massive loss making company ($4.6 bn last year) and to them sustainability means making it into the next financial year.
     
  26. Technologist

    Technologist Member

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    Sense and avoid principally relies on GPS and off board radar, the principal sensor on the actual aircraft is simply a few cameras. Even Lidar/radar scanners are down at the 10k cost level before economies of scale kick in.

    Again I refer you back to the first principles argument, a 4-5 seat E-VTOL will have an unloaded weight of around 1 tonne, it does not contain vast quantities of exotic/rare alloys everything in it will respond in the same way as every other product to economies of volume and these items will reach volume on other devices such as consumer electronics, drones or autonomous cars. If you described everything in a smart phone in 2000 you would come to the conclusion that such a device would cost £10k's but inherently the device is cheap because it is small.

    The UK is in practice regulated by EASA who have very similar views to FAA, the key element is that planes fly so standards are pretty global (I worked in aero for a good few years). The only local restriction likely to curb the adoption will be 1: Weather, E-VTOLs will initially be tested in places with good weather (LA/Dallas/New Zealand) expansion to more difficult environments taking place confidence improves and 2: Planning (obviously).

    Re. ANFO; the reason you don't see bombs going off isn't because delivery mechanisms are lacking. It's because explosives are made difficult to get a hold of and people with the proclivity to detonate them are monitored. E-VTOL's will only be allowed to fly between designated places, the pilots will effectively be systems monitors, it won't let them fly into the houses of parliament. Need I remind you that the most deadly terrorist attacks in the EU in the last 20 years were train bombings.
     
  27. Technologist

    Technologist Member

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    20 seats is probably more people than board the average train at any given station outside the top 10 rail stations in the UK. In fact lets do the maths:

    Liverpool Lime Street is number 10 at 15 million per year:

    Assume weekend is 50% capacity 1,500,000/(52*6.5)=44,500 per day
    Assume 18 hour day: 3,700 per hour
    9 Platforms: 205 per hour per platform
    I'm sure the peaks are much higher.......

    For reference 1 landing pad can have around 30 landings and take offs per hour so with 20 people per aircraft that is 600 people per hour per pad. The pad would be around 30 m square and we'd have somewhere between 5-10 aircraft charging/boarding stands per pad. So we are in similar orders of magnitude to railway stations for space vs. capacity.

    We could have regional VTOL stations on the roof of existing railway stations for example, however as we aren't connected to tracks there is no requirement for landing pads to be connected to each other, a regional city could just have 10 pads plus their associated stands distributed around a 1km square in the centre of town or wherever the modelling suggests they go.

    Re. Security, E-VTOL will be okay with zero security other than that the person flying will be recorded, you can't take control of the aircraft and blowing it up would be a waste of a bomb. 20 seat aircraft as per todays requirements would need the persons flying to be recorded
     
  28. HSTEd

    HSTEd Established Member

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    Unfortunately with aircraft it is not necessary to actually make the bulk of the charge out of actual explosives.
    A relatively small and thus easy to fabricate charge would be sufficient to fragment the aircraft in flight, at which point the bulk of the weapon, consisting of ball bearings or nails or hand fabricated flechettes - all of which are unlikely to be controlled materials. Will spill out and fall onto the streets below.

    Flechette attack is far harder to defeat than traditional explosive driven projectiles.
     
    Last edited: 6 Jun 2018
  29. Technologist

    Technologist Member

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    You can hire helicopters today, they are much easier to hijack or blow up.You are vastly underestimating the difficulties of creating a improvised weapon out of an aircraft.

    I don't know what you're picturing as far as a method of use for one of these things, but you aren't going to be able to fly this yourself, if there is pilot they will be behind a glass partition and if you try to do anything the pilot will hit a panic button and the craft will land at the nearest safe location, police in their own E-VTOL will meet you on landing.

    The flight paths will be pre-set and flown with tight precision, you won't be flying over football stadiums or trafalgar square, the chances of you being able to aim your "weapon" or have it make any definable impact on a target when the target is 500 m below you and you are doing 120 mph is minimal, even with bomb sights and predictable precision made bombs it is difficult to hit targets.

    As for flechettes, you aren't going to be able to drive them at high velocity so you are looking at "lazy dog" (see wiki) type designs. For military purposes they were intended to attack personnel in the open the bombs were around 600lb a hand held device would be able to carry around 500 flechettes. These won't penetrate buildings, and 500 randomly scattered on the street is unlikely to hit anyone.

    We know what happens when aircraft are hit by purpose built explosive charges, they tend to come down in one or more large pieces. All of the pieces will come down at their terminal velocity which for most of the smaller pieces of structure will be pretty low meaning that they won't penetrate into builds or vehicles. The chances of being hit by a piece of aircraft randomly blown up is pretty low, since 1939 plenty of aircraft have been blown up above cities and the numbers killed were negligible.

    Some example cases, in Lockerbie a full 350 tonne 747 landed on a housing estate killing 11 people, in Clutha a police helicopter around twice the weight of an E-VTOL landed on a crowded concert venue and killed 7 people. The vast majority of aircraft crashing kill nobody on the ground.

    If you want to have maximum impact with an explosive device the best place to take it would be a crowded train.
     
  30. HSTEd

    HSTEd Established Member

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    You have a place where you can hire an unmanned, automated helicopter with a carrying capacity of several hundred kilograms at the touch of a button with essentially no oversight over you or your intentions?
    But there won't be a pilot ( a trained pilot would make it impossible for it to compete with other forms of transport) and you won't need to fly it yourself, just need to fly over a busy city centre or similar, which is where the flight paths will be because that is where people will want to go..
    If you can't go near places like Trafalgar Square and similar, and such busy areas are common in central london as it is, it is highly unlikely that it can have any substantial impact on the transport system.
    The whole point of an E-VTOL is it can land all over the place.
    Why the hell are they handheld?
    The whole point is you replace the entire payload capacity of the VTOL with flechettes and a relatively small "bursting" charge.
    Considering your carrying capacity for an eight seater is looking like at least 800kg, you will be looking at 40,000 flechettes, not 500.
    Most of those aircraft brought down by explosive charges mass far more than an E-VTOL would, or tended to be brought down by external explosions.
    A couple of kilos of explosive inside the passenger cabin will compromise the aircraft and likely break it at least in half, at which point the piles and piles of flechettes will spill out.
    Were those aircraft filled with payloads deisgned to cause casualties on the ground?
     
    Last edited: 12 Jun 2018
  31. NotATrainspott

    NotATrainspott Established Member

    Messages:
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    Joined:
    2 Feb 2013
    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?
     

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