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Discussion in 'Roadster 2020+' started by McManX, Jun 9, 2018.
Any guess on price? Or if it’s real?
I honestly don't know if Musk is serious or joking. It sounds crazy but on the other hand, Musk is kinda crazy so....
I guess this is the opposite of Boring! ... approach.
I think it's real. I've read some stuff online about how these cold gas rockets could be used to optimize the aerodynamics.
More speculation here:
Elon Musk says Tesla next-gen Roadster’s ‘SpaceX package’ will include rocket thrusters
Assuming this is not another "bankwupt" type joke, wouldn't the thrusters need fuel? Or does cold thrust mean it would be powered by the compressed air.... like a balloon releasing air and creating thrust?
Musk tweeted that the thrusters would use compressed air, yes. So no need for rocket fuel.
Elon Musk on Twitter
Resistojet rocket - Wikipedia
What comes after plaid mode?
It looks like they have used noble gases in the past for these thrusters in space craft, but for a variety of reasons those gases would not be appropriate for a car. I suppose you could use water if the temperature differential was great enough.
I think it will happen with Cold gas thrusters, and it will be spectacular.
Maybe he is planning on sending another one into orbit as a test payload, but this one will be able to maneuver on its own.
This is not a joke but the rocket thing is a bit misleading.
These are air jets. They take air, they compress it and release it when required.
I hope they focus a lot on where the air intake is and how much downforce it can help create.
They can't go too far either as the g forces would be too much for normal people and the car might damage the road too lol.
Air intake could be more important than the jets at high speeds.
Efficiency will be an issue, some balance is required. They can also use the air to help cool the battery and compress it afterwards but doesn't look like they'll do that.Or use compressed air to cool the battery,, even better i suppose.
The air jets would be cool if they have a directional nozzle so each can direct air in just about any way the car wants. Latency for the nozzle, the sensors and compute would be crucial or things could go wrong, especially if they try to enable flight.
Would be really cool if the car could jump over obstacles in case of an emergency at very high speed but that's gonna be tough if the entire design is not done for it so maybe Roaster 2025 does that.
With autonomy cars could travel at 250mph on highways designed for it - you need long, straight, flat roads to be able to see more than half a mile ahead. But fancy aero and suspension would be helpful to increase safety at such speeds so this is a more rational step than it first appears, all cars might be as crazy in 15-20years.
PS; not quite sure what kind of tires they would need , that might be the toughest part.
If they do it ,this is gonna be so much fun and opens up so many possibilities in the long run.
Edit - They could also use the air jets to enable a virtual airbag for pedestrians.
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I suspected cold gas thrusters using air, but the tweets indicate they are going further. When used extensively for turning, braking and accelerating, cold gas thrusters don't really have the energy efficiency/density required to be used for several laps at the track. I don't think resistojets have sufficient power, either, so I think you are looking at a combustive fuel.
The combustive fuel needs to check some boxes, in my view:
- Energy density
- Easy storage
- Zero emission
At first I was thinking about hydrogen. It does check most of the boxes, and it would just be so deliciously ironic, but safety would be an issue. Hydrogen is difficult to store, and if you have any leaks, you could easily blow a garage sky high. With piping and valves for 10 thrusters, I think the risk of a leak would be way too high.
Then I started thinking about propane. Zero emission is an issue, but other than that it checks the other boxes. And it is possible to get propane from agricultural waste and such. And the Boring Company uses it for the Not-a-flamethrower. So yeah, I think propane is probably the best bet.
A 20 kg tank could store probably 30 kg of propane (408 kWh of energy!), which could provide probably around 10 times more thrust than my previously suggested compressed air solution with 45 kg of air.
I think it is nonsense. These boosters take way too much space in the car. If you miniaturize them, then they would lack power. Another point is safety. Imagine firing these boosters just when a motorcycle is behind you. I wouldn't want to be anywhere near, even in an ordinary car. No way these thinks would be legal...
Accelerating 0-60 in 1.9 seconds is illegal on public roads, most places. Doesn't mean it's illegal to include the ability. The thrusters would likely have several selectable control options. Like:
1. Braking only. This could be used on public roads in addition to ABS, to do emergency braking at say 2 Gs (impossible for other cars).
2. Low power mode. Conserves fuel but still adds some power. Might be sufficiently low power that using it on public roads wouldn't be very problematic.
3. Track mode. Unleashes the beast. (Hopefully no geofence, but it's certainly an option.)
I assume in all modes, the thrusters are controlled by throttle/brake pedal, and steering wheel, and will only engage once the car is at the limits of traction. (It doesn't add anything to the performance of the car before then.) This means that you could drive on public roads, and as long as you never approach breaking traction, the thrusters would never engage.
JATO Rocket Car - Wikipedia
@ Yggdrasill don't focus on propulsion, focus on downforce and center of pressure.
The motor has more than enough power, the issue is grip for acceleration, braking distance and cornering. Grip is the limitation, why they can't accelerate/brake faster.
The tires have a friction coefficient and you can add downforce to improve on that.
A normal car decelerates at 1g, a Formula 1 car does it north of 5g and the bulk of that is due to the downforce.
Sucking air from under the car does quite a lot, a diffser does that and is plenty useful but add fans to suck air and it get crazy.
Aero features can give you downforce while adding minimal drag, Active aero is even cooler as it gives you flexibility and you can even add drag when needed. This is, no idea how to call it, let's say super-active aero.
Downforce scales with the square of speed just like drag so it's very relevant at high speeds but very little at low speeds.
And this is where the jets can help, at low speed more than at high speed. They can help a little at high speed too but at high speed you can create downforce with the air intake and other aero features. At low speeds they are more useful as downforce doesn't help you much at all so it's a neat trick. They likely use them mostly in bursts or they would need to either be able to compress air in real time or have large air "tanks".
For example, a normal car decelerating at 1g needs almost 700m for a full stop from 400km/h. A Bugatti Veyron can decelerate at 1.3g from that speed and stops in under 500m. An F1 car likely does it in towards 100m.
So to recap, the car doesn't need extra propulsion, it has a huge amount as it is, the hard part is how to apply it to the road.
Would you do it if you had a cop car behind you?
Many places have exhibition of speed laws: Exhibitions of Speed Laws | LegalMatch Law Library
Other places would consider it reckless driving.