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Comment by jcheng | Hacker News Reader

Reading https://www.tesla.com/roadster, it seems like both variants only use cold gas thrusters, and the difference is that the "normal" (lol) one only has them pointed rearwards while the flying one has them pointed in all different directions as well.

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There are three versions talked about

1) Base model with a fan for downforce - no gas thrusters at all. This is the one that may actually ship (but bear in mind the last Roadster prototype he announced was 10 years ago, and that one never did ship)

2) One with a smaller compressed air tank in the trunk and rear facing thrusters that would give you a 0-60 < 1 sec launch mode. This will obviously never be street legal (you can't lay down a "smoke" screen on a public road), but conceivably he may build it if there is enough demand (but read the fine print - it says no guarantee it will ever ship)

3) The on-stage stunt version that can hover and flip, which consumes the entire passenger area with another much larger compressed air tank, and adds bottom and side thrusters to give you ~3 seconds of "flight". "Invite only". Maybe he'll sell one to SpaceX - unmanned operation only - just to say that he did.

Yes, the thruster versions both operate on compressed air, which is why you only get a few seconds of operation.

I'm sure having a cold gas thruster is going to be no problem at all for road approval. /s

Best guess is that it's disabled for anything but track/trick stuff. There will be some cool videos eventually showing up with tricks people pull with this. I don't know what else it's for.

I can imagine the lateral thrusters helping it turn faster on the track. Although I wonder if the extra weight is going to net out positive for lap times.

But really, a few very rich people will buy the full-rocket version to impress their friends. They'll play with them on private property.

Solo track use at that. I can't imagine that other drivers are going to be all that happy if they get hit by the exhaust from one of the thrusters in a corner.

Gases dissipate very rapidly, even moreso if doing pulsing or whatever. Probably very unsafe for a human standing literally right behind it, but it'd likely have 0 effect on another car at typical driving distance.

Except for the bit where you can't see a thing.

Great idea to use something like that in a tunnel or a garage. Suffocation - no breathing ... and probably some blown doors/walls from the pressure

Car tunnels should be able to handle that level of bad gasses.

What bad gases? It is literally air. Do you see a lot of mechanics passing out in garages with all that compressed air being let loose?

They said "something like that" and I could easily see other outputs, especially nitrogen or some kind of combustion.

It looks like they are actually using nitrogen: https://youtube.com/watch?v=22rvpUecLts&t=1134s

Air is mostly nitrogen, about 80%. Pure oxygen as you might be thinking, would be quite dangerous - not only for long-term consumption but also in terms of its effects. Oxygen is fuel for fire so a 100% oxygen environment would quite create the pyrotechnic show! The 'white' you see from the exhaust isn't the exhaust itself - nitrogen is obviously colorless, but the moisture in the surrounding air freezing. It's going to be coming out quite chilly to keep the nitrogen liquified ( boiling temp of something like -196F).

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Whoa, was just watching the video (great link btw). People have been debating the specs, but they're shown unambiguously right here. [1] It has 95 kn peak thrust, 6g peak acceleration, pressure of 5500 PSI, and a min operating temp of -200F.

[1] - https://youtu.be/22rvpUecLts?t=1339

Of course air is mostly nitrogen. But if you replace 10% of the air with pure nitrogen you go into OSHA-angering levels of oxygen depletion, and if you replace 25-30% you get into serious danger.

Not easily achieved in a tunnel, but much more easily achieved in a garage.

10% of the air replaced with pure nitrogen would be 0.8 * 0.9 + 1.0 * 0.1 = 82% nitrogen, 18% oxygen. That's perfectly safe for brief exposure, which is all it would be before you return to ambient levels.

To create a dangerous scenario you've gotta do something like somehow gas out your entire tank in a garage and then just stand around for a while breathing it in. Kind of an improbable scenario unless somebody is trying a really weird suicide attempt.

The bigger tank apparently holds 250kg of air. That's about 200 cubic meters. A two car garage is likely less than 100 cubic meters.

You wouldn't need to dump nearly an entire tank of nitrogen to reach levels that are immediately dangerous. And oxygen deprivation makes you stupid well before it makes you pass out, with no "lack of air" panic since that is based on CO2 levels, so even when it would be survivable for a couple minutes you might not even think to escape.

How are you going to suffocate when the thrusters are sending out compressed air?

Nitrogen, actually.

The crash photos are going to be Darwin-award-worthy

I think every buyer should receive a complimentary nomination for the award.

The award is reserved for people who actually died, you can only be nominated posthumously.

It’s just a matter of time before they win.

I could see a safety feature where it launches itself into the air to avoid an imminent crash (providing the area above is free)

I suppose I can see this also. It sounds horrifying. A head on collision is a pretty terrible thing but having one of the cars suddenly fly 30 feet in the air and crashing into on coming traffic does not sound like a great option. Reminds me of the cybertruck "this would make the perfect post apocalyptic vehicle."

you might have a better chance of surviving that 30 foot launch than a head on collision with a pole or a semi truck. don't get me wrong it seems wildly impractical but there may be rare situations where it's useful. ejection seats on fighters frequently injured their pilot but that is better than being dead.

This whole thing is incredibly stupid and yet, people are bending over backwards to defend it. There is not a single traffic situation where the ability of a car to suddenly launch itself into the air doesn't have more downsides than it staying put. This includes overhead wiring, other people nearby, tunnels, bridges, overpasses, lampposts, traffic lights and other street furniture. With a little luck you will survive the impact of your toy when it lands but the party that you land on does not. People have a hard enough time predicting trajectories with everything constrained to 2D, if cars start jumping around like fleas that is not an improvement. From a standstill with other parties around you this is already a serious problem, if it were moving forward at highway speeds in traffic it would be utterly irresponsible to trigger this kind of launch.

What, you don’t think the solution to a situation with too much out-of-control kinetic energy is to inject a whole bunch more semi-randomly-directed kinetic energy?

You see, when you are about to have a crash, and you only have a few milliseconds to react, the best option is to put more energy into the event.

How about rockets towards the front of the vehicle to stop it?

As the saying goes: The more energy the goes into the crash, the better.

They’ll have a special edition with hypergolic propellants.

You are delusional if you think more than one Rocket Roadster will be within miles of another one on a public road.

The image of a chain reaction of RRs popping up like popcorn when another appears to be about to land on it pretty hilarious, though.

That depends on the landing zone being available in a way that's hard for the onboard safety system to predict. But if the car is, say, spinning out you could use these to restore stability or try to recover from the other sorts of disasters that overpowered cars can end up in even on clear roads.

once your wheels leave the road, its hard to slow down. Just getting to zero mph before flipping 100 times and rolling over would be immensely useful.

The Rocket model should never spin out - traction control using thrusters should make it impossible.

The thrusters are primarily pointed rearward and to the ground. It's not capable of doing much at all for a flat spin, the typical scenario of a car spinning out

Incorrect - the Rocket trim (if it ever exists) has four thrusters pointed downward at the wheels for lift and they can rotate 180 degrees and two thrusters at the front pointing outward for use control.

What goes up...

Perfect rich asshole vehicle. Add a ‘safety’ feature that wildly endangers everyone around you.

That sounds like a surefire way to make a bad situation worse.

The car launching itself in the air would also launch anything in the road - debris, rocks, soil - at dangerous speeds in all directions.

it's a show it was not in any way a production car, stop being that gullible people

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The very first cars required to have a person walking in front of it with waving a flag as a warning.

Red flag thing was the UK's Locomotives Act 1865, which dated from before what we call cars were invented. More aimed at traction engines (steam engines that go on the road). Exactly the type of regulation people like to mock the EU for.

Last year I went to a steam show and had to share the street with giant steam tractors for the first time. That law suddenly made sense. The visibility and stopping distance aren't great.

Not like those genius Elon and American minds thinking "oh yeh rocket engines on cars makes a lot of sense", you're saying?

Funnily enough, he was also the first person to get a driver's license IIRC.

>So many things that were invented in Europe couldn’t be invented today

Like leaded gazoline, whose effects can still be seen presently...

That was invented in the US: https://en.wikipedia.org/wiki/Thomas_Midgley_Jr.

I can think of no better person to have been hoisted on his own petard than Midgley. He also gave us the ozone hole. Veritasium has a great hit piece on this utter maniac.

How long is the US going to allow a car able to jump over Hostile Vehicle Mitigation barriers?

Like everything else we regulate.... right up until it becomes cheap enough that "undesirables" might get their hands on them.

No, that's the mind of a person speaking that is thinking of the motorcycle standing at the traffic light just behind this car. Action, reaction, that sort of thing.

> That’s the European mind speaking.

No. That's the road safety mind speaking.

Somehow I feel like "putting highly explosive canisters all around a car" is not the best example for why regulation is bad.

> That’s the European mind speaking.

Swipes are not allowed on HN, and comments that invoke national/regional/cultural stereotypes are particularly out of line here. https://news.ycombinator.com/newsguidelines.html

It's for the ultra rich and a tech showcase, so probably will be classified as off-road use only.

Here's to hoping it will end up with the same reputation as the e-type.

I mean, Leno drives around with a jet engine motorcycle that can melt the guy behind him.

Yes, there are other idiots.

Well he does know a few people in govt now I think? I remember a Tesla showroom on thr white house lawn not too long ago

This is a track car for the uber wealthy. It's only rarely going to be on public roads, and it'll probably have some unlock mechanism for the truly stupid stuff. Honestly, I'm here for it. Automakers have gotten complacent. Between Chinese automakers and stunts like this, we might see the return of outrageous engineering just to prove a point.

It’s a lot cheaper than a Ferrari or Lamborghini or Koenigsegg.

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