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> Yes and no. If you add a refueling stop to a long-haul flight, it can save enough fuel to make up for the rerouting. (Long-haul flying is really inefficient b
by messe 5y ago
> Yes and no. If you add a refueling stop to a long-haul flight, it can save enough fuel to make up for the rerouting. (Long-haul flying is really inefficient because you have to take-off/carry all the fuel needed to make it to your destination).
It seems obvious, but I always forget that the rocket equation applies in aviation as well. The massive difference in fuel efficiencies when you get your oxidizer for free tends to overshadow it.
- Scoundreller 5y agoAnd using smaller airframes (because you can run smaller/lighter fuel tanks, along with lower drag) can add to those efficiency gains: > the total fuel consumption of a 7,200 NM flight can be reduced by up to 15% by making an intermediate stop half way, while using conventional existing long-haul aircraft. When the aircraft is specifically designed for medium-range operations (such as e.g. the Airbus A300), the total fuel savings could increase to 27%. From: "Evaluation of intermediate stop operations in long-haul flights" NYC to Delhi is at 6400 NM.
- sigmoid10 5y agoThe rocket equation doesn't apply here, because planes don't just get their oxidizer for free, they get the whole reaction mass as well. So they generate forward momentum in a different way. Additionally, once a plane reaches cruising altitude, the only energy losses are due to air resistance, because the lift vector from the wings and the gravitational pull are antiparallel to each other and perpendicular to the direction of motion. The commenter above is still correct though, because the energy needed during ascent is proportional to mass times height. So if you can cut the fuel in half by limiting the total range, you can save a huge amount of energy (i.e. fuel) during ascent.
- newaccount74 5y agoA plane is not a satellite. You need to constantly expend energy to keep it in the air. The more weight is on the plane, the more lift you need. To get a bigger lift, you need to angle the control surfaces steeper, which increases drag. Therefore transporting heavy things by air (like fuel) is extremely inefficient.
- tehjoker 5y agoDoes this apply to cars? I always wonder if there's a mileage bonus for riding with a half empty tank.
- ac29 5y agoSure, it takes less fuel to move a car that moves less, but fuel is an nearly irrelevant fraction of total weight in most cars. A gallon of petrol weighs about 6 lbs.
- gruez 5y agoA heavy car takes more energy to get up to speed. The extra weight also "stores" more energy once you get up to speed, but that's useless when you don't have regenerative braking. Also I'd imagine that rolling resistance would be higher when the car is heavier.
- deleted 5y ago[deleted]
- roelschroeven 5y agoAs gruez says, a heavier car needs more fuel to accelerate and has more rolling resistance. It also needs more fuel to drive up a slope. Some of these can be regained in a car with regenerative braking, but even than only partially because there are always losses. But the difference is not nearly as large as it is for airplanes. Having your fuel tank only half full means more trips to the gas station, which might even negate all gains you try to make. It seems a good idea though not to drive around with things live heavy tools all the time when you don't need them.
- Rebelgecko 5y agoI think that's part of why Anchorage is one of the busiest airports in the world
- Scoundreller 5y agoIt really helps for the cargo airlines operating 'old' inefficient aircraft. E.g. 747s And you can load them up more when you only have to half-fill the fuel tanks.