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Comment by vessenes

1 day ago

In the video they claim the air is supersonic at exit, and point out the mach diamonds -- and I think they said 60 kilonewtons of thrust max, which is really a lot. So I think the volume of air would decrease roughly 60% from your estimate? I'm not a physicist.

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.

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vessenes

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rich_sasha  1 day ago

So let’s double the speed - 1.2 Ma. You need half the mass now - 25kg/sec. If you want to have 10 seconds worth of hover - that’s 250kg of gas. Plus the weight of the storage tank. Plus - this is the amounts for hover. Not for any extra force on top of that.

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.

  • sobellian  1 day ago

    Your math is pretty good, Tesla actually gave the storage tank capacity as 250kg

    ETA: this is a horrifying amount of energy to be sitting on top of.

  • phillmv  1 day ago

    what's there to miss? if these ever make it to market their only purpose will be conspicuous consumption for vice-signalling ding dongs

Ajedi32  1 day ago

The "pin to a wall" part uses fans, not the cold gas thrusters. It can probably stay there until the battery runs out. The gas thrusters are only needed if you want to go 0-60 in .8s (with the Thrust version), or if you want to fly (with the Rocket version). Probably those only last a few seconds before the air tanks need to recharge.

bell-cot  1 day ago

> phase one - you drive around, and excess energy goes to compressing air.

It's an electric car - unless you've got an incredibly long charging cable, there is no "excess energy" when you're driving around.

  • sjducb  5 hours ago

    The question of when to compress the air in the tank is an interesting one. Ideally you’d use the rockets for acceleration, breaking and cornering; which is all the time.

    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.