Can electric cars on the highway emulate plane-to-plane refueling? | Hacker News Reader

Can electric cars on the highway emulate plane-to-plane refueling?

spectrum.ieee.org

47 pointsjonbaer128 comments

Asking sincerely: Why should we not simply pull over to do this? Planes obviously are a different situation, but cars can easily just stop.

While cool to imagine, it seems unnecessarily complicated and unsafe to do this in motion on the road.

[Edit: The prof and his team are quite serious about it, so I assume there must be a reason and I'm actually curious what it might be.]

This is the correct question. Planes did it because they had to. Highly trained pilots execute in-air refueling. Not kids with their folks teslas.

It seems like a valuable proposition if we threw out the existing paradigms of road transport.

If we throw out concepts such as ownership of vehicles and fuel and treat all road vehicles as one system of controlled individual elements, you could envision is a more efficient solution. Traffic jams would be lessened, trip times would be shortened, total fuel usage would go down, etc. On road-fueling would be one element in a world like this: road based freight delivery could run without stopping by using vehicles expected to have short journies to refuel the trucks along the way.

This is all to define a hypothetical new paradigm in road transport and to quantify its potential consequences (good and bad). I had not thought about on-road refueling before and I think there is good value in pointing it out. We're not at the point where we're seriously charting a course to world like this, but we need to know what the world looks like before we can start to do that.

Many things are valuable if we throw out the constraints of dealing with existing reality. Even then I'm not sure it is valuable; roads suffer from lack of maintenance already. If anything we should be looking at how to make roads less expensive. Having autonomous vehicles disperse their weight to reduce prevalence of potholes, for example.

Right, and that is one thing to weight for when choosing the behavior of the system. While the article in question doesn't explicitly say this, I think these seemingly impractical solutions add to the theoretical toolkit that we can use to shape a road utopia, if society ever agrees on what that would look like. If society does ever agree on a road utopia and then consider it worthwhile to pursue, it will be valuable to have these ideas laid out. Perhaps they are useless today, but they motivate this idea. If they weren't proposed then the possibility of a future road utopia is entirely impossible.

If we are "throwing out the existing paradigms of road transport” then why not throw out roads completely. Rails are way more efficient.

That's true only if they reach all destinations

Yep, they do already! The future is here, just not evenly distributed (to the US :P)

https://www.openrailwaymap.org/?lang=null&lat=48.21003212234...

Can I go from my house to my friends house using only rails? My house to the supermarket?

Not all pairwise points are connected by rails, while they generally are by roads.

The post is about long distance travel.

My point still applies.

An old-new paradigm of road transport, https://en.wikipedia.org/wiki/The_Roads_Must_Roll makes for a good read.

The non-serious answer is that we need to charge while driving to best emulate F-Zero https://youtu.be/BIe4AvKLSa4?t=217

That was a mid-air repair of another flying vehicle.

F-Zero & F-Zero X allowed you to use the shield bar as boost-fuel as well.

Because charging takes much longer than filling up with gas. If someone is willing to pay a premium for charging while driving to reduce total trip time, that's a business opportunity.

This is often said, but I am not so sure. Fast-charging takes somewhat longer than filling with gasoline/petrol, but I usually also want a bathroom and coffee break. I can easily do that while my car is charging. That is not really true while dispensing gasoline. It is not so obvious to me that I am losing out time-wise.

This is not idle speculation. I own an electric car. Furthermore, the vast majority of my charging occurs at home, over night. The total amount time I have saved by not having to visit gas stations for literally months is significant.

> Fast-charging takes somewhat longer than filling with gasoline/petrol, but I usually also want a bathroom and coffee break.

It's more than "somewhat". I can put over 400 highway miles of range into my vehicle in five minutes with a gas pump. It takes 30 minutes to put half that into an EV. I don't want to stop for half an hour every 200 miles.

> This is not idle speculation. I own an electric car. Furthermore, the vast majority of my charging occurs at home, over night. The total amount time I have saved by not having to visit gas stations for literally months is significant.

It sounds like you don't have many days where your driving exceeds the range capacity of your vehicle. The technology in the article, and the post you are responding to, are in the context of long-distance highway travel. It's for cases where a vehicle must be recharged in the middle of a trip, even when it starts with a full battery.

* I don't want to stop for half an hour every 200 miles.*

Ugh, I don't even want to drive 200 miles in a day if I can avoid it.

I don't want to stop for half an hour every 200 miles.

You might be able to do a gas stop in 5 minutes. I'm willing to bet that you can't do a gas stop and pee in that time. Two hundred miles is probably 3 hours of driving, so I am also willing to bet you want at least a coffee. Add five minutes (or more if you have to move your car). If you add in a snack, your total time will probably be around half an hour. A meal, make it an hour.

When I drive long distance, particularly by myself, I typically get on the highway with a full tank and pull off when my low fuel light comes on. Depending on traffic conditions, this is typically between five and six hours. At the end of that I don't mind stopping for half an hour or more, but that requires far more than 200 miles of range.

When I do stop in the middle for coffee and a leak, it's rarely more than 15 minutes total off the highway (unless the service is slow).

Back when I did more road trips with friends I measured how long stops take. Stops take a lot longer than people think. People think a gas and pee stop is 5-10 minutes tops. Really 15 minutes to half an hour. Fast food place, half an hour. Sit down meals take more than an hour.

Yeah certainly by myself, I could do a gas stop in 5 minutes. With other people never works out like that.

Commercial planes don’t even do midair refueling, because it’s expensive and dangerous.

Why bother? With top line EV ranges reaching close to 400 miles, after that amount of time I need to get out of the car. If you want people to be able travel huge distances cleanly without stopping, then what you’re actually looking for is a train.

What about an autonomous semitruck that could run 24 hours a day except for unloading/reloading cargo, refueling, and maintenance?

Trains. The fact that long haul semi trucks are a thing is a failure of infrastructure.

Edit: as some have pointed out, it’s more a failure of policy.

Trains are large and inflexible. Short of having a city-block resolution freight train network at every population center, you'll need something flexible for the last mile of delivery.

You’re misunderstanding.

The only reason why you’d need on-road recharging for hypothetical autonomous semi trucks is if they’re regularly traveling outside the range of their batteries, which is probably in the 400-500mi range.

In a well designed infrastructure system, that shouldn’t happen often. Instead the hops of hundreds of miles should be handled by trains, leaving semi trucks for the last dozens of miles from train hub to area of need.

Some long haul trucking will happen, but it should be a slim minority of cases.

Adding an extra step (rail hub to short haul truck transition, potentially at both ends of the trip) adds cost. This cost is (and will be for the foreseeable future) less than having the less efficient semi-truck do the entire trip at least for the kinds of loads that are currently carried by semi-truck. JIT inventory systems also don't play nice with rail.

Semi trucks are cheaper because they receive a $125B+ yearly subsidy in the form of road maintenance. Semi trucks do 99% of the damage to our public roads, but only pay 35% of the cost.

I suspect that rail would be much more price competitive if we took that subsidy away.

You’re right about JIT, but we’re also seeing the downsides of JIT infrastructure during this pandemic. I suspect that we’ll see a push for more redundancy in our supply chain for reasons completely unrelated to trucks vs. trains.

Assuming we're resurfacing our roads once every 5 years, if we banned trucks it would take 100x longer to accumulate the same amount of damage, so we'd be able to resurface only once every 500 years?

I would expect there to be a significant amount of damage done just by the elements, independent of usage.

There’s also the fact that roads are built up to trucking standards. Without trucks the roads would be thinner, reducing cost and pollution (concrete is a major source of CO2).

Roads are mostly made from asphalt and mother nature would still destroy them in well under 100yr in most places.

Highways are much more relevant when we’re talking about trucking, and highways are largely concrete.

This is utterly false and in a trivially verifiable way in this age of street view.

Raised highways sometimes have concrete decks because the strength can be attractive but the overwhelming majority of highways are asphalt. At or below grade highways are almost always asphalt. Tunnels are often concrete but those are a vanishingly small minority of miles.

If you’re going to call something “utterly and trivially verifiable (sic) false” you should actually check. Interstate highways use more cement than asphalt.

“The analysis shows that a total of approximately 1.5 billion metric tons (Gt) of aggregates, 35 million metric tons (Mt) of asphalt, 48 Mt of cement, and 6 Mt of steel is in place in interstate highways.”

https://pubs.usgs.gov/fs/2006/3127/2006-3127.pdf

AFAIU, the original Interstate Highway System was all concrete. These days states usually resurface heavily trafficked segments with asphalt (of various varieties) atop the old concrete. Apparently, at least as of 2006 60% of the system was still concrete pavement: https://pubs.usgs.gov/fs/2006/3127/2006-3127.pdf Which is not surprising as IME long segments of the IHS are often still concrete pavement, especially in the South and West; it's only in urban areas where asphalt surfacing seems ubiquitous.

I'm not sure how new segments are built today, but they may very well still use concrete underlayment, or at least something more substantial than loose aggregate. Road tech these days is way more complicated than just concrete v. asphalt. I would guess that for remote segments, and given the load requirements, it may still be cost effective to keep using concrete surfacing.

Sure. I don't necessarily disagree with your conclusion that trucks undercontribute to road maintenance costs. I just don't think those numbers are sufficient to prove it.

You might still want want "in flight" charging even for shorter trips just to keep trucks moving but I guess the world where load/unload times aren't enough is pretty unrealistic.

The inflexibility of trains can be a feature in some cases. People like to live near subway and commuter rail stations partly because they know the route and service level are much less likely to abruptly change on them than a bus route would.

They’re also more immune to congestion. Back when I lived in Chicago and used public transit, one would strongly prefer the rail over buses when possible, except in cases where the bus was an express route.

100 trucks running right up next to each other is a train. I could imagine train operators converting their right of ways to a system where each train car can be autonomous and can leave the train and track without disruption. As the train comes by an exit location (station), the cars that need to get off just come out of the train and leave while the train tightens up again for aerodynamic efficiency and continues on without even slowing down.

These single tracks could even allow individuals to run their own single/double cars on them if the track was not to crowded and premium price was paid. With automatic vehicles, a reality on such controlled tracks today, our current infrastructure for transportation is definitely a failure compared to what it could be.

I don't see that happening. Train cars are incredibly simple things that have barely changed in many decades, probably because it's hard to introduce changes when all the cars need to be compatible with one another. Train cars don't even have electrical hook-ups, just air brake lines.

True for freight, but not true across for all rail. High speed rail in particular is usually a different gauge and has electric hookups for all cars, because every wheel needs to be driven to hit those speeds.

Trains are far more efficient, less subsidized, safer, less polluting...

https://grist.org/article/freight-trains-19th-century-techno...

Even if you electrify trucks the tire and brake wear and road degradation contribute an enormous amount of PM 2.5.

Sure you'll need trucks for the last mile but every ton of freight we can move to rails or waterways is a victory for humanity.

I used to think that too, but

- economically trains are a monopoly. This point dwarfs all others.

- we don't have two-directional rails everywhere

- electric trucks can change the economics and mitigate the pollution of trucking

Electric trucks will still emit a rather large amount of pm2.5, and are still heavily dependent on both direct and indirect federal subsidies.

The thing that really feels possible to me is long haul autonomous trucks only on the highway. They can transport themselves between depots and then an actual driver does the tricky in-city transit and delivery/pickup.

I would be extremely opposed to this on efficiency grounds.

Semi trucks are awful. They’re horrible polluters, and they represent 99% of the road damage being done, despite only kicking in 35% of road upkeep cost. This is a drain on the public purse in exchange for more pollution and more accidents.

A far more sane policy would be to shift as much freight over to rail as possible, and reserve semi trucks for the last miles between rail head and customer.

Also, rail exists today. Self driving trucks don’t.

A diesel electric duorail truck would be great for large freight loads.

Maybe you’re onto something here; what if we just rebrand trains to appease the car centric average American?

400 miles is possible but there isn't a 100% EV that achieves a 400 mile range under typical circumstances. Realistically you get about half that if you're doing highway driving and live in a place where you need to have the HVAC running all the time. Though, I think it'll probably get there within the next 10 years.

Not everyone wants to take an hour long break every 400 miles.

On a 2000 mile trip, that's an extra 5 hours of travel time. I'd much rather be at the beach than at Rest Stop X in the middle of nowhere for an hour.

Are you gonna drive 2000 miles straight through or get a hotel?

I did 1800 miles straight through twice, once with three drivers and once with five and both were pretty rough. Would not repeat. Almost had a driver fall asleep at the wheel the second time and I didn’t get to nap after my last turn at the wheel because of it.

If you’re doing it alone, subtract an hour a day for hotels. If you are with a group, then I think some of the other people are right: you’re going to stop more often and for longer than you think you are. Half an hour every three hours will keep you at above half your range and wouldn’t be so bad.

The longest you can drive without stopping is proportional to the smallest bladder in your group.

You're missing the point.

For the MOST EXPENSIVE electric vehicle, that probably will not actually get the rated 400 mile range, I have to spend an hour+ to get a full charge to go the full capacity. Now, we need to split up long road trips even more. Better hope that hotel has a recharging spot. If not, more wasted time.

Or I could just buy a corolla for 20-50% the price, get insanely good gas mileage, fill up when needed in under 5 minutes (enough for a bathroom break).

Electric cars don't ever come close to paying for themselves. That's why you only hear about these cars on HN or in SV - only rich people can afford them and their inconveniences.

Maybe special powerful cars that are constantly charged could drag others along a fixed line in a kind of "train".

Can anyone explain what happened to battery swapping. A few years ago there was this Tesla show where they swapped three cars in the time it took to refuel a normal ICE automotive. But after that nothing happened.

I know it is difficult to handle when you do not own the battery but I would guess 90% of private long distance trips are return trips, so you could swap batteries at your trusted former gas station every 200 miles and then on the way back home do the same and get your old battery back at your last stop and keep that pack for all your short day to day trips. But somehow, this idea seems to be 100% abandoned.

Edit: Follow up conspiracy: Could it actually be because the battery is the one component of an EV that degrades the fastest and thus cars would last much longer (and no manufacturer would want that) if you could just swap the main battery every 100.000 miles or so?

That's because it's not "cool". We wanted our flying cars, so if we aren't getting those, we at least want our cars to do wild and unbelievable things like flock together and fuel each other like jet planes. Who's going to invest in battery swapping technology? It's effectively a solved problem and not exciting.

Probably the same reason why smartphone battery is not swappable. For various reason we don't have swappable smartphone battery even though it is technically much easier problem to solve.

What reason would that be? I always assumed that was because of the pursuit of slimmer phones and to discourage repair.

It’s also a more complex and expensive. Swapping cellphone batteries means you need to own another battery which few people did once capacity increased. With cellphones people that want a swappable battery can just get an external battery pack but most people can simply recharge daily.

Hmmm... is this not also an option with an electric car? A "long distance" battery pack trailer of some sort? Lose some sleekness, but gain a ton in utility, and storage space for those long trips.

> Swapping cellphone batteries means you need to own another battery which few people did once capacity increased.

That doesn't make sense to me. Sure, maybe you can't get an OEM battery, but I've owned cell phones in the last 5 years that I easily swapped out the old battery with an aftermarket battery for about $12. I think people have the ability to buy batteries.

> With cellphones people that want a swappable battery can just get an external battery pack but most people can simply recharge daily.

My OG Pixel phone is on its last legs in terms of battery capacity, which means it will probably get scrapped(even if I trade it in somehow or get it "recycled"). I would have swapped the battery with a new one, but I don't have that option. At least without risking damaging the phone on disassembly. Recharging daily isn't a solution because it runs out of power in about 5 hours without even using it.

Have you considered a battery case like: “Google Pixel 2 Battery Case, 4700mAh“ https://www.amazon.com/Rechargeable-External-Protective-Port...

From reviews that product is likely terrible, but I know people that are happy with their iPhone battery cases.

In theory we should be able to have external battery packs for electric cars, but I think the power density would have to about double before that happens. How many miles can you fit in a 30 lbs battery right now? Not very many.

I think that gets you about 10 miles in a Tesla. If it got you 20 miles it might be worth building a few slots into the trunk for extended range.

Discouraging isn't something that affects next quarter's earnings. Reducing the cost of water-related repairs, warranty replacements etc., though.

even those two reason still make sense for car.

It depends on the smartphone, there are still (very few) around that have one.

Beside the possible "planned obsolescence", I believe that the change was mostly because of waterproof or almost waterproof design, and (IMHO senseless) "let's make it thinner".

Immediate concern for me would be safety. My impression is the battery pack provides a lot of the rigidity necessary to keep the car in one piece, and swapping the battery out introduces new hazards.

There's also the concern about liability, whether the battery pack you're getting is as good as the one you're trading in (what if it's older and has a lower overall capacity), and how that might impact resale value.

Third would be logistics, keeping the flow of batteries through the stations and having enough batteries on hand to swap on demand, and keeping compatibility with different makes and models, is a challenge.

That's why you would only use those for long distance trips and for everything else you would own that one old pack.

Rigidity could indeed be a problem but so has been gasoline safety. There would need to be standards but there are also standards for charging plugs so, it is not like this never happened before.

Or have a built in battery and battery swap bay. Both can happen and no reason not do have both.

unless manufacturers implement some sort of standardized battery pack, it seems like this would be a logistical headache. simple enough to store and charge your original battery for when you return, but how do they have the correct battery for you to pick up on the outgoing leg? is the "gas" station supposed to keep a stock of charged batteries for every type of EV?

Increased capacity and high speed charging have made it not worth the cost/complexity.

I've read the Rivian truck can have an additional battery dropped in the truck bed but I don't think it is something you can buy yet.

Correct-ish. Rivian has a patent for such an ability, but no announcement even of planned availability.

Continued battery improvements pretty much obviate any more complicated range extending efforts, IMO, other than perhaps road embedded magnetic chargers, which are fairly simple.

It was abandoned because fast charging stations keep improving, and are much simpler and cheaper to operate than battery swap stations. It's already at the point where you can take a 400-500 mile road trip in a Model 3 with maybe a single twenty minute charging stop, which is just not that much extra time, and most people like to take a short break every few hours anyway.

I suspect Tesla knew this would probably happen, but IIRC there was a rule for a while with the California ZEV credit program where manufacturers qualified for extra credits if a vehicle could be "refueled" in under five minutes. Tesla set up a single swapping station to prove it could be done and therefore qualify for the extra credits, but it was always kind of inconvenient and expensive and very few people actually used it.

I see, that actually makes sense. To bad most affordable cars actually operate in much lower ranges.

A car with a 40 mile range would be cheaper to buy, and a lot lighter so also more efficient. You could swap in a 400 mile battery when you actually need it.

The problem I have with the 40 mile range is that is highly dependent on

1. temperature. Extreme cold lowers range 2. topography. Inclines can drain a battery quickly. Declines can add range. 3. driving style. Do you have a lead foot? 4. Driving type. Are you on a highway?

You're nitpicking here. 60 mile range. 100 mile range. Whatever customer needs daily is far different from their outlier use cases. Most people with home/work charging never go below 40 miles from full.

fair enough. It is an innovative idea.

I’d still like to be able to tow a battery behind me for extended trips.

I don’t know how running the AC impacts range, I would like to know. Places with extreme weather and major population centers can make an otherwise short drive really taxing on resources through ac use or just being stuck in place for extended periods of time. Like how peak LV traffic can turn a 15 min drive into a 50 minute drive in 120f+ heat.

Tow-able batteries would make wide use cases like apartments more viable too.

Edit-typo

That seems like a fantastic idea. This way, the car's internal battery can be smaller and lighter for day-to-day use (and therefore more efficient), and whenever longer range is needed you can just rent a fully-charged tow-a-battery, which you can swap out like propane tanks, or recharge yourself at home. These tow-a-batteries would work with any electric car with standard secure hook-ups.

Since these batteries would be rather expensive, I imagine that you would have to pay a refundable deposit to the tow-a-battery network (Shell, Esso, etc.) that covers the full cost of the tow-a-battery in order to rent one.

The biggest down-side is that a rear-end crash could be rather dangerous. I don't see a way around that without making the tow-a-battery a vehicle in itself.

by the time you've added enough protection (ie, extra mass and drag) to the towed battery, it seems like you would be pretty deep into diminishing returns. a large amount of the extra energy would be spent on moving the trailer itself.

Not really. Yes batteries add lots of weight. But electric motors have lots of torque and are known to climb hills easily. Like how Tesla’s forthcoming truck can tow up to 14000 pounds. I’m not doing the calculus, but I suspect the power characteristics of electric motors more than make up for a towable battery.

Edit-here’s an article about a company doing this

https://electrek.co/2020/02/19/french-startup-proposes-batte...

energy, not power. I'm sure the motors have enough torque to tow the battery, what I'm doubting is how efficiently that extra battery capacity gets converted to range.

as an aside, the cybertruck is (probably) pretty bad at towing. see this video for an interesting argument: https://www.youtube.com/watch?v=S4W-P5aCWJs

Very slow video. Wish it were transcripted.

It also allows for faster retrofitting of old vehicles with new battery tech.

It does sound like a very intriguing idea, and one that I believe requires some research.

However, in practice I think this would be equivilent to towing a small tanker trailer full of chemicals or gasoline. It would require plaques indicating the contents, special insurance, and all kinds of BS at the RMV. Imaging if one decoupled on the highway and drove into oncoming traffic at 60mph? It would essentially be a rolling bomb. This happens quite often with camper trailers.

I think engineers would need to emphasize redundancy, failsafe measures, and automated attachment/detachment capability that does not require human interaction to safely accomplish. Then you will convince CA that it doesn't need a ream of paperwork to register and then the rest of the country will adopt it.

So here’s a company doing it for fleet vehicles in China. Granted, it’s not a guarantee it can get through the US regulatory system, but there are definitely more dangerous factors on the road.

Personally I see this as completely new tech from the ICE. That means it really ought to open up new usage and user experiences than the outgoing tech. And those changes should be perceived as better in some way to really take off.

Edit-forgot the link: https://electrek.co/2020/05/06/mobile-ev-chargers-and-vans-g...

Towing would annoying but dropping a block into the Cybertruck bed or the Y back cargo area would be pretty neat.

Most drivers aren't competent to tow a trailer, especially not at high speed or reversing.

Most apartment sized AC units top out at a few kW - that's the peak power, just maintaining the already cooled apartment is going to be consuming much less power.

A car cruising at highway speed is lconsuming something on order of 10x as much power. Given how much smaller cars are than apartments, it's an even greater difference.

So to answer your question: not much. Heating in cold weather is much worse on range, as it's not just the cabin but also the battery that needs to be maintained at an adequate operational temperature.

I am imagining a scenario where an autonomous vehicle zooms toward the car at high speed and then from underneath the car swaps out the batteries then zooms away.

Well if you want to see one way the battery swapping model can fail work, check out the book Totaled, which is about the Israeli EV startup Better Place that tried battery swapping before Tesla was a thing. Granted there were a lot of complicating factors that may not apply in the Tesla case (securing battery swapping locations in Israel came with specific challenges), but it may provide some insight.

Nobody who actually owns a car wanted to swap batteries.

There are many reasons: ownership of the battery, logistics of the swap and swap back, required payment for convenience, need to stop anyway, range of vehicle, etc.

Why not just have overhead lines that you can attach to when you need a charge? Do it like the street cars. Or have something like a railroad you can drive up onto and then it charges you while you're traveling over it.

This seems like it would only work if you're able to stay bumper to bumper with the charging car for 30+ minutes. You'd have to be traveling a very long distance along the same route (and, the charging car's destination MUST be before it runs out of power after transferring its power). What are the odds of that happening, on a reliable basis? At that scenario, it seems more sensible to install overhead wires (or underground) along freeways for long distance travel.

This reminds me of old Popular Science magazines promising a future of unrealized technology.

I do not think this is the future. But it’s something I’d like to see in a sci-fi movie.

Replacing highways with trains for most trips is more sustainable.

I think it's called a train...

The only good options are:

1. Make much more rapid charging possible on the cars much closer to the interstate. 2. Add a electrified metal rail to the road so that the cars can charge like a subway car.

Emulating plane-to-plane refueling entails all sorts of system dynamics problems because of the untrained human driver in the mix.

Wouldn't it be a lot easier (and likely cheaper in the long run) to emulate overhead line-to-train power transfer?

Seems like "transfer of electricity into an (ideally) land-bound vehicle from its infrastructure" would be a more closely related problem than "transfer of fluid from one airborne aircraft to another."

I think http://eptender.com/en/battery-tender-2-2 (renting a battery in a small trailer to extend a car’s range, potentially dropping it off at a different place from the one you picked it up) has more chance of succeeding In the market.

I've been thinking for years that fully-automated platooning / drafting should be a good option for self-driving cars. Run it via an app, cars make themselves available for drafting, others nearby sign up, they all line up and save energy. Could be a nice feature for Tesla, or a competitor, to augment the value of being in their network.

Obviously, this would rely on both self-driving and car-to-car communications to ensure simultaneous braking, acceleration, etc. to avoid accordion effect and chain-reaction collisions.

Charge-sharing as in this article could be a nice addition too. Also seems most plausible to automatically pay for shared charge in credits of some sort, or cash through the app. My biggest question is whether the shared charge would be sufficiently useful in comparison to the cost/maintenance of the extra moving parts. Seems like induction power&charging in sections of road could be more effective.

One of the next obvious steps for self-driving vehicles is “flocking” or drafting; this is an almost trivial problem once two or more vehicles are autonomously locked within a few inches of each other.

If you have a car only a few inches behind you and you spot a problem and need to emergency brake, you can't actually start braking until the car behind has started braking, otherwise the car behind will crash into the back of you.

If you have 3 cars in a row, and the first car spots a problem, it can't start braking until after the 2nd car has started, but the 2nd car can't start braking until after the 3rd car has started.

It gets linearly more dangerous as more cars are added.

Not saying it can't be done, but the problem is more subtle than just working out how to stop the cars from crashing into each other at speed: they also need to be able to brake in emergencies without crashing into each other.

Possibly the way to do it would be to mechanically couple the cars like a train, so that it is safe for the one in front to start braking earlier than the one behind, albeit with reduced performance.

The idea is predicated on autonomous control and presumably the vehicles communicate in real time...they all brake together at the delta V of the least capable member.

The "real time" control loop between the sensor on one car and the brakes on the same car is much tighter than that between the sensor on this car and the brakes on another car and then feedback from the other car that braking has started.

I don't actually know how long it takes between the computer deciding to brake and the car actually starting to slow down, but I expect you can't just throw out a message saying "I'm braking immediately" and start braking without any kind of confirmation that the message was received, and expect it to be OK.

But maybe you can afford to wait for a confirmation? The speed of light is pretty fast, and you're not transmitting that many bytes.

Especially if you consider that a human could easily take 200 milliseconds to react to something even if it's really paying attention. You could request a braking confirmation from the other side of the Atlantic and still come out ahead!

There could be some leeway to initiative braking on following cars quicker with control loop similar to existing emergency brake assist systems [1]. These currently apply the brakes quicker and more powerfully than a driver’s foot when the car thinks it’s in an emergency situation. The same signal could be sent to following cars by the time the driver sufficiently engages the pedal.

[1] https://en.wikipedia.org/wiki/Emergency_brake_assist

Braking delta V depends on many variables such as mechanical condition, component temperature, road surface friction, etc and is thus difficult to predict to that level of precision. Even with real-time communications, if the vehicle in front slows less than expected due to hitting a pothole or something then the vehicles behind are going to have to react damn fast to avoid a collision. It might be achievable on certain roads but it will be a tremendous engineering challenge. Don't expect to see this in passenger vehicles any time soon.

Yeah all good points, and just to add, there's also the challenge of maintaining perfectly reliable and low-latency communications over any sort of wireless medium in a variety of unpredictable outdoor conditions.

Once we solve autonomous driving. Decades out.

> two or more vehicles are autonomously locked within a few inches of each other.

Never going to happen so long as potholes and poorly patched roads exist.

Just build high speed rail. It’s available today, rather than in some hypothetical future once autonomous cars work.

Too close for comfort I think. Brakes are still hydraulic and they react when they react - with a different delay for each vehicle.

Tesla have talked extensively about "Convoy Mode" for the upcoming Semi Truck where they will do exactly that. Maybe the gap will be more than inches, but the idea is they draft together.

I think the plan for early autonomous driving is the first one in the line will have a human driver, and the others will follow autonomously in convoy.

Or you could just ride on a much less complicated, safer and more efficient railroad.

I see no problems at all with being magnetically coupled via an extended probe to another car transferring high voltage and/or current while driving at highway speeds, none what so ever...

Wouldn't it make more sense to build the charging into the road?

We could make the road out of interlocking hexagonal solar panels

This was done as you probably know [1] but it's not clear that the road surface is a good place for solar panels. They get dirty and damaged. It's certainly orthogonal to charging vehicles on the road, given we know how to transmit power already.

[1] https://www.google.com/amp/s/www.theverge.com/platform/amp/2...

Indeed [2]

BTW when searching on Google it is quite obnoxious that it doesn't navigate to the actual URL but instead prefixes it with Google..

[2] https://www.google.com/amp/s/www.businessinsider.com/first-s...

Are you saying charge vehicles on the road using i.e. inductors underneath the road?

Why do that?

Incorporate a charging loop into the road.

Better still, throw away those heavy and toxic batteries and just collect the car's power directly from the road.

What's the efficiency on something like that?

What's the cost of tearing up every single highway in existence to add a charging loop?

I’m assuming very high power transmission in short period of time. Thus moderate amps and very high voltage or you’ll need thick cables.

Seriously doubt fast charging a battery of running car from battery of another running car.

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