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"Rocket Equation", thank you! I've had a total brain-block on that term as I was literally just trying to answer a question related to this, on a Tesla forum, a

"Rocket Equation", thank you! I've had a total brain-block on that term as I was literally just trying to answer a question related to this, on a Tesla forum, and I couldn't remember the name! The inevitable question of "Why can't they just add more battery for more range?" Like you mentioned it's some variant of this and I'm sure there is a name for it. I'm not a mechanical engineer. But again, dragging more mass requires more energy. In an automobile, you'd need a bigger and stronger car. My Model 3 is one heavy beast. More weight and it would need bigger (perhaps more) tires and a heavier/stronger drivetrain. The new Roadster was must have been planned for "some time in the future" production (not in production yet) because they have some formula that dictated a new battery was coming. A 620 mile range on a car that can do 0-60mph in 1.9 seconds (twice the range of my car) has to have some way of reducing that weight. Who knows. Fascinating problems. I wish I had gotten myself into that sort of engineering when I was young(er).

csours 6y ago
The Rocket Equation is important for rockets because they cannot pause and refuel like cars or even airplanes can. There's no compromise or trade-off in the rocket equation. For cars or airplanes you can have a smaller tank and more refuelling. Obviously for airplanes there is some minimal tank size where you can't actually take off, and some maximal tank size where your airplane doesn't have any usable cargo/passenger space. --- The limit for cars is almost always tires, as it is in this case. Or rather the interface between tires and the road. Weight always deforms the road surface, more weight deforms the road more, and at a certain point the road quickly breaks down. Thus, governments put weight limits on vehicles [0]. In my state, it's 20,000 pounds for a single axle (it assumes you will be using a truck and loading the rear axle). If we take that 20,000 pounds and subtract 2,000 for the cabin and the rest of the drivetrain, you could have 18,000 pounds of batteries. I think 18,000 pounds of batteries could take you a long long way. As a cross reference, a Commercial Drivers License is only required at 26,000 pounds. https://en.wikipedia.org/wiki/Commercial_driver%27s_license https://en.wikipedia.org/wiki/Commercial_driver%27s_license 0: https://www.txdmv.gov/motor-carriers/oversize-overweight-permits/texas-size-weight-limits https://www.txdmv.gov/motor-carriers/oversize-overweight-per...

csours 6y ago

The Rocket Equation is important for rockets because they cannot pause and refuel like cars or even airplanes can. There's no compromise or trade-off in the rocket equation. For cars or airplanes you can have a smaller tank and more refuelling. Obviously for airplanes there is some minimal tank size where you can't actually take off, and some maximal tank size where your airplane doesn't have any usable cargo/passenger space. --- The limit for cars is almost always tires, as it is in this case. Or rather the interface between tires and the road. Weight always deforms the road surface, more weight deforms the road more, and at a certain point the road quickly breaks down. Thus, governments put weight limits on vehicles [0]. In my state, it's 20,000 pounds for a single axle (it assumes you will be using a truck and loading the rear axle). If we take that 20,000 pounds and subtract 2,000 for the cabin and the rest of the drivetrain, you could have 18,000 pounds of batteries. I think 18,000 pounds of batteries could take you a long long way. As a cross reference, a Commercial Drivers License is only required at 26,000 pounds. https://en.wikipedia.org/wiki/Commercial_driver%27s_license https://en.wikipedia.org/wiki/Commercial_driver%27s_license 0: https://www.txdmv.gov/motor-carriers/oversize-overweight-permits/texas-size-weight-limits https://www.txdmv.gov/motor-carriers/oversize-overweight-per...