Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?
Trust the World's Fastest VPN with Your Internet Security & Freedom - A Lifetime Subscription of PureVPN at 88% off. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. ×

Comment Re:I don't like the EHang 184 design (Score 1) 47

Are you making a joke, or are you not familiar with multicopters?

If one motor dies or its prop breaks or something, the computer detects that and turns that motor off, and the motor on the opposite side of the craft (which will be spinning in the opposite direction.) This will keep the forces balanced.

Then you speed up the remaining motors to make up for the lost lift. Given that you've only lost/turned off 25% of your motors, the thing would almost certainly still be able to maneuver normally. Performance would be reduced, yes -- but it would be designed to be able to lose some number of its motors and still maintain altitude and fly around.

And even if you were to lose all four bottom motors/props -- even if that doesn't leave it with enough power to maintain altitude (which is uncertain -- it might still be able to fly with only four motors), it would still be able to make a controlled descent at a reasonable rate of speed. (It might not be able to pick its landing spot, however.)

That said, given that human life would be on the line here -- I'd expect these things to also be equipped with a ballistic parachute. You probably wouldn't need it if one motor or prop failed, but if more things went south (or the computer or power source failed) -- you might.

Comment Re:I don't like the EHang 184 design (Score 1) 47

I didn't do the work to figure out if these guys are using four motors for their eight props, or if they have eight motors, but I'd want to use eight motors, at least two redundant control systems, independent motor controllers...

Motors are small and cheap -- there's little advantage to one big one per boom driving two props over two smaller ones, one for each prop ... and some big disadvantages.

I'm pretty sure they'd design it exactly as you said, including a ballistic chute in case everything goes wrong. Anything less for a human carrying craft would bankrupt the company the first time one crashed.

Comment Re:I don't like the EHang 184 design (Score 1) 47

Even with just four rotors you can lose one rotor and go into a slow descent with the rotor opposite the failed one dedicated to maintaining balance and the other two remaining rotors at near-maximum thrust.

Unless the rotor opposite the failed one can *reverse* ... that's not going to work, and even if it can, the odds are pretty good that it can't switch between going forward and backwards quickly enough to overcome the instability on the axis between the two working props that this mode would have.

*Maybe* this could be made to work better (and without reversing) if the center of gravity was shifted towards the motor/prop dedicated to maintaining balance. (Tell the passengers to lean to the front right!)

Also, with only three props it probably won't be able to do much to control yaw. That said, a smart computer might still be able to have it go somewhere, even if the thing keeps rotating. But even if not -- a controlled descent even while spinning is still better than falling like a brick.

That said, the Ehang solves this problem by being an octocopter. I would not expect any human carrying craft to only have four props, though I'd probably also expect them to give them a ballistic chute in case everything goes wrong.

Comment Re:I don't like the EHang 184 design (Score 1) 47

The Ehang is an octocopter -- so it can lose somewhere between 1 and 4 motors/props and still fly properly. (Exactly how many can be lost depends on which ones are lost and how much thrust it needs to maintain altitude.)

That said, if it loses power completely, or the computer crashes or something ... it might as well be a brick for how well it'll fly. There will be no autorotation.

That said, I see no reason why they couldn't equip it with a ballistic parachute in case something does go horribly wrong.

Comment Re:I don't like the EHang 184 design (Score 1) 47

Quadcopters are *not stable at all*. Without the flight controller and its gyro sensors they would immediately crash. This goes way beyond the computer turning a human's movements of the two sticks into throttle inputs for four or more motors -- it also makes sure that when the human isn't telling it to do something that it doesn't do anything. Turn this off and the craft would flip over and crash in a few instants.

That said, these flight controllers can be used on traditional helicopters too, making them as stable as quadcopters. I don't think this has been done much with manned helicopters yet, but R/C helicopters? Sure.

The nice thing about quadcopters is that they replace the considerable mechanical complexity of a helicopter with extremely simple mechanics and a computer with some sensors. This makes them cheaper to design, build and repair.

Comment Re:It's the only reason (Score 1) 143

Nope, it's not done right.

For example, suppose you have an iPad and an iPhone. Somebody sends you a message -- and it goes to your iPad, but not your iPhone. But your iPad is at home, so you don't get it for hours. Or maybe your iPad has been dead for a week, but it was still logged into iMessage when it died, so it's still getting the messages rather than your phone.

Yes, there are ways to make it work, but you've got to be aware of the problem and stay on top of it, being careful of what you let into iMessage. (And yes, that iPad will keep trying to do it!)

And it's worse if you have an iPad and an Android phone, because the Android can't log into iMessage at all, so anybody who sends you a message via iMessage will have it go to your iPad.

If you want people to reliably get your messages and to reliably get theirs ... you're better off turning iMessage entirely, on all devices, and just sticking to SMS. They won't be able to message you via iMessage, but at least they won't *think* they can message you via iMessage but really the message gets lost for a long time because its going to a device you rarely use ...

Facebook Messenger is more of an example of it done right -- messages go to every device.

Comment Re:i.e. I think I can ignore the law if I want to (Score 3, Insightful) 176

How is this different?

Only the FCC can regulate the airwaves, much like only the FAA can regulate the navigable skies.

Now, this idea of it being physical trespassing if somebody doesn't comply is interesting, but this has come up before, such as what happened here.

Comment This reminds me this Napster article ... (Score 1) 394

This development reminds me of the things predicted this article from 2001. The article itself was written about Napster, but it's written in the vein of all the bad things that could happen *in the future* after Napster is gotten rid of, and the banning of analog inputs/outputs was a large part of it.

Now, his timeline was obviously way too fast, but moving analog headphone jacks would fit into his vision -- he does talk about the "hoarding of analog speakers", after all. (Which is kind of ridiculous, as ultimately, even a set of speakers with a digital interface ultimately has an analog speaker making the actual sound, but whatever.) If analog sound outputs do go the way of the dodo (Apple's move certainly doesn't take us there, but it could be the first step in a several decade process that does) ... then a complete DRM path like we're seeing with a lot of HD video now might actually happen.

In a similar vein, RMS The Right to Read dystopian short story (written about software and reading freedom rather than sound countent, but still similar) may actually be coming closer to reality, though he set his time frame further ahead -- 2096, 100 years in the future -- so we can't really say he predicted it or not yet.

Comment Re:Try it (Score 1) 91

Odd. I put coordinates into google maps all the time and it works fine if I just put "lat,lon".

And if I put "0,0" -- it takes me to a point in the Atlantic ocean where latitude and longitude are zero, what I'd expect.

Looks like google didn't add a fake island there, however -- but though the ocean does seem to be either less deep or more deep in the general area than the area around it.

Comment Re:18650 is a form factor (Score 2) 138

250 watts is a lot of power.

100 watts is enough to get a typical cyclist to around 15 mph on level ground. (Assuming 100% efficiency, which is overly optimistic, but not too far off for an electric motor.) Going up to 250 watts wouldn't increase your speed by that much -- maybe 23 mph? Mostly the extra power would be useful for hills.

If you keep your speed down to 15 mph (treat it like a bicycle rather than a moped) it would last a good deal longer, and of course by pedalling you can get a lot more distance.

Comment Want to be sure they got it? No iMessage. (Score 1) 157

iMessage *could* be fixed. If Apple would make messages go to every device that's signed on under that account and send it via SMS (and have the system throw out duplicates if needed), it could be decent.

But instead ... it only goes to one device, which may or may not be the one they're using. (Or maybe it won't even go to that one device.)

So ... ultimately, if you want to make sure that they get your message, you need to turn off iMessage, or at least not use anything that uses it.

Personally, I'm surprised that Apple screwed this up so badly and left it that way -- but yet, here we are.

Comment Re:And what's our suggestion to friends and family (Score 1) 79

I'm scared of my mother calling me one day telling me "I've lost every picture from all my life and a guy is asking me $10K to recover them".

Yup, this is a real, justified fear.

It's wise to not attempt to switch her to Linux -- she'd probably fight that (it's too different for most people without any real benefits for what they do), and it's not really a solution to the problem anyways.

Probably the best answer to this is to buy her a big USB hard drive and set up some sort of backup that she can run just by clicking on something, and drill into her head how important it is to 1) do the backup occasionally. and 2) leave the drive off when you're not doing backups.

Ransomware isn't the only concern. Hard drive failure and software crashes that erase the disk are others.

Alas, often it's only an actual loss of files that convinces people to take backups seriously -- and it's unethical at best to *fake* a loss of files (and then recover them all because you got "really lucky") so that's not really an option unless you're dishonest.

If you see her often and she doesn't mind, you could do the backups yourself and keep the drive yourself -- that way, when she calls you, you just say "That sucks! Fortunately, I backed up all your stuff last week ..."

Slashdot Top Deals

Competence, like truth, beauty, and contact lenses, is in the eye of the beholder. -- Dr. Laurence J. Peter