napkins, and envelopes at least kind of make sense.
Who was ever writing on the back of cigarette packs?
British officers planning trench raids in the front lines during WWI. Or, at least, that's where I've been told the expression originates.
Really, though, is it impossible to imagine no one, ever, using a cigarette pack to jot something down? It's a colloquialism. It doesn't even have to be taken literally to make sense. What is gained by questioning it on that level?
Wouldn't the back have printing on it? I could imagine someone ripping the pack open and writing on the insides, which are blank.
https://britishmilitarybadges.co.uk/products/princess-mary-1...
That Christmas box itself, by the way, is beautiful. Brass, with an embossed portrait of Princess Mary, and scrollwork on the cover. My former father-in-law had one, that had been brought back by his father from France - missing, ironically enough in the context of this conversation, only the cigarettes, which he didn't smoke, but used in trade.
I took the OP's question to really be a question about the origin of that phrase, and with your answer, I learned something I didn't know before. So I, for one, am happy the question was asked.
The OP's question was clearly skeptical though:
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napkins, and envelopes at least kind of make sense.
Who was ever writing on the back of cigarette packs?
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Implication being that writing on the back of cig packs does not make sense. I'd agree with your reading if not for the "at least kind of make sense" bit.
in india.
I'm imagining this in two phases: phase one - you drive around, and excess energy goes to compressing air. Phase two - you use that compressed air which takes very little additional power, so you get to double up on force. I guess likely a 'running mode' where it's using some power to keep suction on.
I'm curious how much time you get at full blast vs 'just' enough to keep the car pinned to a wall, e.g. 1 vs 2 g.
It still doesn’t make much sense to me. And that’s before considering what happens when you get rocket stream hitting a tarmac road. Never mind public roads, this sounds like a major hazard anywhere. Plus the quantity of compressed gas son board (if that’s how it works)… not a pretty crash. At these numbers, imagine 10MJ released all of a sudden - apparently that’s about 2.5kg of TNT.
Surely I’m missing something… as I say, I can’t make sense of it.
ETA: this is a horrifying amount of energy to be sitting on top of.
Ok. 0.5% of all cars exploding still doesn't sound reassuring.
> the last 2 years over more than 250 launches is at 100%.
Sure, if we tune the statistics such that we only look at those that didn't fail, then nothing failed. I love magic tricks!
In the US alone, people make some 600m trips a day, so that "reliability" would result in about 2.5m to 1m failures a day.
It's an electric car - unless you've got an incredibly long charging cable, there is no "excess energy" when you're driving around.
So probably the compressor will run all the time.
You’ll have to do a lot of modelling to work out the best time to use the rockets, my instinct is that fast cornering is the best use of the rockets. Maybe with a boost button to get you off the line fast at the beginning.
From the marketing materials it looks like straight line acceleration is being prioritised tho, so you charge the tank during braking and cornering.
(2200lb) Also, that is completely impossible.
Lightest Tesla is ~3600lb, typical Model 3 is over 4000lb.
To get a sense of how light 2200lb would be, a 2026 Miata is heavier than that. A tiny Fiat 500e with limited range is ~3000lb.
It is flat out impossible for this Tesla Roadstar to weight 2200lb if it has any batteries in it.
Back of the fag pack, let’s say it is light for an electric car and weights 1000kg. I’ll also go on a limb and guess the air flow is actually subsonic - 200m/s would make it 0.6 Ma (still insanely fast!). Even then, that requires 50 kg of air every second. Or 40 m^3. Using everyone’s favorite metric, this empties an Olympic swimming pool in 1 minute. It also requires a MW of power. I mean… that’s a lot??? Though admittedly, only about as much as accelerating 0-60 in 1 sec (50% of that in fact). So the flying would draw as much power as accelerating at full throttle.
Power requirements would go down a lot with slower exhaust speed, but then you need to shift more fluid. 40 m^3 already seems like a lot to me.
I get it’s a neat little demo and they have to get SpaceX into the picture somehow, but still I don’t understand how it’s supposed to add up. Also, what do I know - just a humble physicist.