7 ms·
It's also hard because batteries don't get lighter as they deplete, so you're landing a plane with the exact same weight as what you took off with, meaning you
by mikepurvis 7y ago
It's also hard because batteries don't get lighter as they deplete, so you're landing a plane with the exact same weight as what you took off with, meaning you need much more rugged (and heavy) landing gear. This is extremely significant when you consider that a fully loaded 747-8 is 970,000 lb, of which up to 326,000 lb is fuel (per Wikipedia's numbers).
It's a hard problem, and most proposed solutions are extremely novel and risky, like having an all-battery tugboat that tows the plane up to cruising speed/altitude before returning to the airport to charge or get a battery swap— obviously bad because risky, also adds 50% to runway capacity to land all the tow planes.
- chrisseaton 7y agoApparently they do actually get lighter, but not usefully so.
- w0utert 7y agoWhy is that? I’m not a battery expert but it would seem all that charging a battery does is move electrons in the cells around, no?
- chrisseaton 7y agoe=mc2 I think - there’s a Tesla forum thread about it, and Quora articles and things if you look. I’m not a physicist.
- rubatuga 7y agoThe mass depletion is less than a milligram...
- chrisseaton 7y agoYeah I read the same threads - that’s what I was referring to.
- im3w1l 7y agoChemical bonds have (often negative) mass. A chemical reaction will break and/or form bonds. Thus it slightly changes the mass. In a battery there will be chemical reactions happening at the anode and cathode. One reaction produces electrons and another absorbs them.
- ShorsHammer 7y agohttps://physics.stackexchange.com/questions/34421/does-the-mass-of-a-battery-change-when-charged-discharged https://physics.stackexchange.com/questions/34421/does-the-m...
- kuu 7y agoJust drop them before landing... There could be a batteries landing place where they'd be collected. Is it too crazy?
- mikepurvis 7y agoSince a big chunk of the power is expended on takeoff, the ideal would be to drop part of your battery then rather then waiting until after landing. But either way, you're stuck with the significant complexity and expense of having to prepare a parachute and landing gear specifically for the battery on each flight, plus having to collect and charge those batteries.
- tonyedgecombe 7y agoPerhaps you could trail a long unwinding power cable behind you which disconnects when fully extended.
- Alupis 7y agoWhat happens when it mechanically fails and doesn't disconnect? Have a 2 mile long cable being drug behind a 200mph flying machine? That seems quite dangerous - to both the aircraft and everyone onboard, as well as to anyone on the ground in the path of this cable.
- tonyedgecombe 7y agoWhat happens when the plane mechanically fails? Having 600 tons of metal raining down on a population sounds quite dangerous.
- Alupis 7y ago> What happens when the plane mechanically fails? Having 600 tons of metal raining down on a population sounds quite dangerous Simply put, that's just not how aviation works. Mechanical failures aren't uncommon in aviation, but for an aircraft to not be able to divert and return to the ground, a lot has to go wrong all at once. It's infinitesimally rare for all systems to fail at once on an airliner. There simply isn't a problem of airliners dropping out of the sky, ever. They're incredibly robust machines. However, with your idea, we'd be relying on a single system to prevent catastrophic failure. That's a massive step backwards for aviation. That doesn't even begin covering the problems with delivering enough electricity over this cable to power an airliner at takeoff... That cable would need to be a very thick gauge of wire and very heavy - causing all sorts of it's own problems.
- tomerico 7y agoAren’t planes already designed for landing at full weight for cases where the plane needs to turn around and land where it departed?
- jandrese 7y agoYes, but they are only intended to use it in rare emergencies. It stresses the airframe components and reduces the life of the aircraft. To build an aircraft that lands heavy every time you need a much stronger undercarriage and frame.
- user5994461 7y agoand how often are planes fully loaded with fuel? A plane only needs enough fuel to reach the next destination. Saves the weight and money.
- QuotedForTruth 7y agoSome planes are capable of that and some aren't. Some have fuel dumping systems to get weight down. https://en.wikipedia.org/wiki/Fuel_dumping https://en.wikipedia.org/wiki/Fuel_dumping
- AWildC182 7y agoYour car can run past redline, it just shouldn't all the time.
- sokoloff 7y agoMany are equipped with fuel dumps. Others have mandatory “overweight landing inspections” prior to further revenue flight.
- selectionbias 7y agoWhy wouldn't you just ride on the tugboat?
- comicjk 7y agoIt doesn't have the range for useful travel. It's designed to get the vehicle up to speed, using almost all its energy, and then drop away. Think of the first stage of a rocket.