You need the electric equivalent of a glider tug plane to get you up to altitude. It can then return to base taking its drained batteries with it while you continue to your destination with fully charged batteries.

If that sort of complexity were viable for commercial aviation, we’d be air-to-air refueling airliners.

Air-to-air is way more difficult than just a tug, though.

Very much disagree. Air to air refueling is done in a very stable manner at cruise altitude. Takeoff is a much more dynamic flight regime where things can go very wrong very quickly.

If that’s the case, why doesn’t the Air Force tug up its fighters? It’d be a huge advantage.

Why? Energy density way beyond anything battery, and power headroom way beyond anything designed for frugal transport.

Short haul passenger flights are not about speed but about getting directly to the stopover, without the unpredictability of ground transport. A "powered glider" with separating assist for the climbout could be a great match for that task.

And the tug would obviously not really be a tug, but a winged battery directly attached to the aircraft it supports, with barely enough wing for a controlled return. An electric drop tank. Not exactly unheard of in military aviation (except for the "electric", obviously)

Given a range of options for a similar problem, glider pilots generally opt for tugs, which suggests that complexity is within range of a general-aviation pilot class, let alone a commercially-certified one. But let's take your point as given.

Fighter aircraft are generally built for speed and have (even relative to commercial aviation) often fairly low range. The equivalent to "tugging" would be external jettisonable fuel tanks, and we have seen those in military use since at least WWII. Given the general lack of electric propulsion in military use, that seems reasonable. The other model has been JATO packs applied to both fighter and cargo aircraft (Fat Albert, a C-130 Hercules, is often fitted with these for air-show demos). Not electrical power, but an external boost assist.

For drone craft, there are deployment scenarios in which a large cargo plane drops (electrically-powered) drone swarms. I don't know the extent to which this has been deployed, but again it's similar.

If a military were to adopt tugs, I'd expect them to be applied to drone or cargo missions, either with a drone tug (similar to the cargo-plane model above, but possibly with remotely-piloted / autonomous tugs), or with some capability for lofting a battery pack that could be detached and flown back to the take-off site after contributing to initial take-off and climb. That is complicated, but might fit certain mission profiles, and for a relatively slow long-haul cargo mission might make the cut.

Worth also noting that most EV aviation concepts are for relatively modest cargoes and distances. The more viable range from 2--12 passengers for perhaps 100--200 km at low speeds. I've seen some more ambitious proposals, but they strike me as not especially viable.

Drop tanks, well, drop batteries, to get rid of the excessive mass.

Kinda crazy but might actually work for continental flights over cooperative areas. Parachute the empty batteries down with some minimal steering mechanism to land them at regularly spaced depots, then ship them back to airports fully charged.

Turnaround time for planes is short enough that you’d need to do a battery-swap rather than a battery-charge anyway.

I'd like to see what a typical widebody's fuel drain over time is, but suspect a large share is the takeoff-and-climb portion of flight.

A winged battery which could drop away at ~FL20--30 or so and return to either the origin field or some secondary collection point might be all you need, rather than tossing batteries out the cargo bay throughout the flight.

I also suspect that most EV aviation will be shorter haul such that a large set of drops wouldn't be necessary.

You piqued my interest enough to go hunting - this StackExchange[1] question estimates ~19% of fuel is spent on initial climb-out to 30k feet for a 737-800 on a 5-hour LA->JFK flight.

Without doing hard calculations, it intuitively feels pretty marginal potential flight weight savings for the operational complexity it would add

[1] https://aviation.stackexchange.com/questions/47262/how-much-...

Thanks for that!

Worth noting that EV aircraft flight segments are likely far shorter (100--500 km, maybe at a stretch 1,000 km, not the ~5,000 km of JFK->LAX), and cruise much slower (~100--300 knots, say), so climb-out would be a proportionately larger share of the energy budget.

And ditching 20% of your energy storage mass immediately on attaining altitude would still be a considerable savings for the remainder of the flight as that mass doesn't need to be kept aloft.

EV aviation (and aviation itself) is a battle of thin percentages. EV aviation itself has relied strongly on materials advances (advanced fibre composites), and reducing crew (ultimately: autonomous piloting). The need for cabin crew for safety reasons remains, and would be a significant hurdle. The extent to which non-revenue occupants and payload can be minimised likely plays a huge role in any eventual success. A 19% reduction is nothing to be sneezed at, if it can be achieved without significant other compromise.

Thunderbirds are go!

On the other hand, only some fraction of the energy inherent in jetfuel is converted to work. So fuel based airplanes have to carry a lot of "extra" energy that is then just wasted as heat.

Jet engines are pretty good, over 50%, and electric is more lien 75 (not 100)