5 ms·

> For metal-air batteries, one of the more promising areas of research, the problem is actually worse: the cells gain mass as oxygen is reacted with the metal a

> For metal-air batteries, one of the more promising areas of research, the problem is actually worse: the cells gain mass as oxygen is reacted with the metal anode, discharging the battery. That's interesting, thank you for the info. Having a different characteristic from the usual one might lead to interesting applications. For instance, airplanes use a lot of fuel for takeoff, as they pay double the price for the weight of their fuel: they need to carry it up, when they have the most. This could actually be a game-changer, I think. That could also be exploited: raise the battery when it is charged, have it gain weight, generate electricity while lowering it. Perpetual motion doesn't exist, of course. But gaining a bit of extra mileage is theoretically possible here :)

dredmorbius 6y ago
More likely, rethinking flight-segment dynamics and design. The bulk of energy expenditure is on takeoff and climb segments of flight. Cruise is relatively low energy, and during approach and landing, aircraft are frequently effectively gliding. Pilots and aviation engineers speak of the amount of energy in the aircraft, exclusive of fuel, represented by its mass, altitude, and velocity. Ideas I've seen suggested include catapult or towed launch, ejectable or jettisonable batteries, and/or hybrid fuel/electric designs, exploiting these factors. The general problems are: - These all increase complexity and failure risks. - They are novel (and hence risky) concepts. - Virtually all have scaling issues, being possibly feasible for smaller (drone, single-passenger, or few-passenger craft), but not heavy or superheavy jumbo jets. (Square-cube relations mean, generally, small aircraft are easier than large ones). - The typical power requirements are violated in emergencies. Fuel-driven aircraft can apply TOGO (take-off/go-around) power on demand, whilst a hybrid or compound design likely could not. And final flight-phase aircraft typically have half their takeoff weight, having burnt the difference in fuel, further expanding performance options. As for "lowering the battery", you'd do better to fly the entire aircraft at a gradually descending flight path, trading lower-drag high altitude for higher-drag lift as the battery gains mass. Current long-haul aircraft (sometimes) practice this in reverse, reching higher flight levels as fuel is consumed, lift requirements reduced, and lower-drag high-elevation flight being possible.

dredmorbius 6y ago

More likely, rethinking flight-segment dynamics and design. The bulk of energy expenditure is on takeoff and climb segments of flight. Cruise is relatively low energy, and during approach and landing, aircraft are frequently effectively gliding. Pilots and aviation engineers speak of the amount of energy in the aircraft, exclusive of fuel, represented by its mass, altitude, and velocity. Ideas I've seen suggested include catapult or towed launch, ejectable or jettisonable batteries, and/or hybrid fuel/electric designs, exploiting these factors. The general problems are: - These all increase complexity and failure risks. - They are novel (and hence risky) concepts. - Virtually all have scaling issues, being possibly feasible for smaller (drone, single-passenger, or few-passenger craft), but not heavy or superheavy jumbo jets. (Square-cube relations mean, generally, small aircraft are easier than large ones). - The typical power requirements are violated in emergencies. Fuel-driven aircraft can apply TOGO (take-off/go-around) power on demand, whilst a hybrid or compound design likely could not. And final flight-phase aircraft typically have half their takeoff weight, having burnt the difference in fuel, further expanding performance options. As for "lowering the battery", you'd do better to fly the entire aircraft at a gradually descending flight path, trading lower-drag high altitude for higher-drag lift as the battery gains mass. Current long-haul aircraft (sometimes) practice this in reverse, reching higher flight levels as fuel is consumed, lift requirements reduced, and lower-drag high-elevation flight being possible.