Automotive Blog

Flying high - not just Rudolph!


We have recently seen a number of press announcements about the research and development ongoing in the area of, for want of a better term, ‘flying cars’, some of it involving major names from the automotive and aerospace industries.  Whether it is taking drone technology and adding passenger- or payload-carrying capability, or taking cars and adding the ability to fly, both approaches are increasingly mentioned in the same breath as ‘autonomy’ and ‘robot taxis’ as being part of our future transport mix, ready to whisk us over the jams and safely to our destination.  But, a time of year when we are all preparing to look skywards in the hope of glimpsing a certain gravity-defying parcel-delivery vessel, is what we are being told about ‘flying cars’ even vaguely realistic?

Firstly, we need to remember that, unlike (current) road space, air space is, and will need to remain, a managed environment.  Maintaining separation of independently controlled flying cars (whether autonomous or not), parcel-delivery drones and other conventional aircraft, plus aerial pedestrians (otherwise known as birds of all shapes, sizes, and speeds) would be a massive undertaking.  Air traffic today is managed by one to one communication between each aircraft and the ground-based controller.  It is still a manual process with aids limited to proximity warning rather than executing any avoiding action.  Even partial automation of this process would be dependent on a big step forwards in the ‘internet of things’ where all flying objects were interconnected and could ‘agree’, instantaneously, mutually compatible avoiding action.  In a busy environment, this would require the projection of the flightpaths of multiple objects in order to ensure that there was not an unacceptable knock-on effect from one action.

Secondly, what happens when things go wrong?  An accident involving ground-based autonomous vehicles will typically involve a few people in the vehicles directly affected, plus potentially some pedestrians.  This is more likely to result in injuries rather than fatalities.  An aerial accident will almost always result in fatalities, not only of all passengers on board, but also of any people unfortunate enough to be underneath the falling debris.

Thirdly, whilst social acceptance of the risk of accidents would be unlikely to come easily, the same is true of the regular environmental impact of filling our lower skies with ‘flying cars’.  Aircraft noise travels a considerable distance, and as all concepts shown to date are rotorcraft in order to allow vertical take-off operations, this means that rotor noise dominates.  In order to achieve lift, the advancing blade reaches close to supersonic speed, and this creates a lot of noise.  Putting the rotor in a duct helps, but in order to avoid issues with yaw control and provide redundancy, all the concepts that have been shown so far use multiple ducted fans, so have multiple noise sources (albeit each one would be individually quieter).  Today, road noise blights the lives of those who live near roads, but would we really want to add to this with continuous airborne noise spreading over a wide area?  Because it is not as if the roads would suddenly fall silent ...

Finally, the concepts we have seen appear to assume electric motors as the drive source.  The batteries are made from ‘unobtainium’, a material we look forward to seeing; either that, or all flights would be just a few minutes long followed by several hours of recharging?  As a comparison, a battery pack on a Tesla currently weighs 600kg, and gives a range of around 3-4 hours drive time carrying up to 5 passengers at say 400kg total plus luggage, plus the weight of the vehicle itself.  A typical current helicopter offering a similar journey range and payload has a maximum take-off weight of 1500kg, within which the energy source to offer that range weighs a maximum of 360kg, reducing towards zero (therefore reducing the energy requirement to propel the vehicle) as you travel.  The Tesla battery still weighs 600kg when flat.  Is this the reason why, in the announcements we have seen, details of the energy sources to be used are pretty sketchy at best …

So, just a few small challenges to overcome then – a huge development of the internet of things, a battery technology breakthrough, and complete consensus on what role such ‘vehicles’ should play.  Alternatively, we could look to hitch up some reindeer, but for the next few weeks at least, they are going to be otherwise engaged …

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