Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
Get HideMyAss! VPN, PC Mag's Top 10 VPNs of 2016 for 55% off for a Limited Time ×

Comment Just one fatality (Score 4, Interesting) 297

two of which resulted in fatalities.

Sigh. One of the crashes resulted in one fatality. The other two crashes, no fatalities. (And it is not yet known whether Autopilot was engaged at the time of those two incidents.)

Getting distracted with Autopilot engaged is like removing your seatbelt because you have airbags. You may be able to occasionally get away with it, but it's still an incredibly dumb thing to do. (And the former endangers other drivers, not just yourself.) The silver lining of these incidents is that maybe more drivers will start paying more attention while using AP, though it should have been up to Tesla to properly instill this sense of caution to begin with.

And side skirts/guards should really be mandated for trailers nationwide. (They're already mandated in California.) It may not physically prevent an underride at high speed, but it doesn't have to; the radar is much more likely to detect them and trigger collision-avoidance braking. It's only a small patch for a small part of the problem, but better than not patching it at all.

Comment Re:Awesome! (Score 1) 136

As a Tesla owner myself (albeit a pre-Autopilot version), I am as shocked and saddened as anyone else by this incident. Obviously we don't know for sure that he was watching a movie, or even that he wasn't paying attention. For all we know he might have been paying full attention, but fully assumed the autopilot would brake, "froze" when it didn't, and failed to brake himself. Possible but unlikely. (Especially for a Navy Seal.) I'm sure we'll learn more as the investigation continues.

Why People Freeze

In the more likely scenario that the driver was distracted, my line above was just a way of emphasizing that even with autopilot, it's critically important to watch the road at all times. (Just as it's important to wear a seatbelt at all times, even though removing it usually has no consequences.) I meant the line in a somber, wry way, not in a fozzie-bear laugh-out-loud way. (if that helps.)

Comment Re:That came in at a pretty steep angle (Score 4, Informative) 206

There are two reasons that I've seen.

Third reason: Wind. In the post-launch press conference, Elon mentioned that the wind was significant during landing. (And may reach up to 50mph tomorrow on the way back to port.) So the rocket had to tilt somewhat into the wind to avoid being blown sideways relative to the landing pad, and only went vertical at the last moment. It also explains why the droneship maintains a slight tilt in some of the post-landing footage; this is to cancel out the considerable force of the prevailing wind.

Comment Re:"mass market affordable car" (Score 4, Informative) 430

And after these five years, I'd expect the range of the car to have dropped 20% or so.

Um, no. I own a vintage 2008 Tesla Roadster, and its range has dropped only about 10% over nearly 8 years. The battery chemistry and durability used by Tesla has only increased since then, so I the Model 3 will do substantially better even than that. Over five years, it might drop 5%. Possibly 10% at the outside, but not anywhere close to 20%.

Comment Re:A few potential issues (Score 3, Informative) 218

Now here's a huge issue I haven't seen anyone talking about that gets progressively worse as the track/tube length increases, subsidence and ground movement.

The subsidence / ground movement effect is dwarfed by the simple thermal expansion of the tube over the day/night cycle, which can grow/shrink up to hundreds of meters over the length of the tube. This effect can be compensated for by allowing the tube to slide smoothly across the pylons to achieve tensile equilibrium. (Perhaps with motorized assist to overcome friction.) The "slack" is taken up at the endpoint stations, through a telescoping system. Each pylon can allow for perhaps a meter of lateral flex to account for local ground shifting, and the pylons themselves can be easily repositioned if they start to get close to their tolerances in a local area.

By the way, how much material would such a full sized tube use up, and whats the current national production of said materials?

The complete Alpha-design hyperloop from LA to SF would use about 1 million tons of steel, or about 0.02% of the world's current annual steelmaking output. For scale, this is about 10x more steel than the Birds Nest stadium in Beijing, or about 100 Eiffel Towers' worth.

Comment Re:hyperloop without the hyper or loop (Score 1) 218

Presumably every Hyperloop capsule would be instrumented to gather data along its journey to immediately reveal any imperfections or problems. Since the travel surface is a completely controlled environment (no birds pooping on the tracks, etc.), it ought to be far easier to maintain than open highways or exposed railroad tracks. The Hyperloop system will directly generate revenue for its own maintenance and upkeep, whereas bridges really don't. (Toll bridges, maybe.)

Comment Re: Weather of Climate? (Score 1) 273

And how much gets bled off into space?

Much less than would be if there weren't so much CO2 in the atmosphere trapping the heat. As we inject more CO2 into the atmosphere, less heat escapes to space, and the equilibrium surface temperature rises quickly. This is why the human-caused rise to its current value of >400ppm is so alarming, and where the ultimate 350ppm "safe" limit calculation (to avoid catastrophic temperature increases) comes from.

Comment Re: Weather of Climate? (Score 0) 273

You are wildly off. A Cat-5 hurricane sustains about 1 petawatt of power output, or ~50x the rate of humanity's fossil fuel consumption. A year's worth of human output could power this hurricane at full strength for about a week. These storms typically last at peak intensity for a couple days. In other words, humans are adding about two or three Cat-5 hurricanes' worth of energy per year to the global environment.

Comment Re:Enlighten me please (Score 1) 450

The MacBook product page, in the Graphics and Video Support section, states: "Simultaneously supports full native resolution on the built-in display and up to 3840 by 2160 pixels on an external display, both at millions of colors". However, it looks like this will require either 4k displays with USB-C inputs (passing DisplayPort 1.2), or else USB-C to DisplayPort adapters, neither of which seem to be currently available. The USB-C to HDMI adapters sold by Apple seem to be limited to 1080p.

Comment Re:It's almost like the Concord verses the 747 aga (Score 1) 157

A person needs at least 20kPa *from the mask to breathe*. Not 20kPa *ambient pressure*. Please learn to read.

The mask pressure must match the ambient pressure, or else the wearer's lungs will rupture (unless they're wearing an enclosed pressure suit). Please learn physics. Again, this is the reason for the 40,000ft flight ceiling for commercial aircraft; oxygen masks rapidly lose their effectiveness with an ambient pressure below 0.2atm, which is why pressure suits are required for pilots flying at higher altitudes. The absolute physical limit for unpressurized flight is known as the Armstrong Limit, which occurs at about 62,000 ft; even wearing an oxygen mask, your bodily fluids will start to boil above that altitude.

The "problematic loading on the capsules" is from the high speed aerodynamics, not the ambient pressure

Aerodynamic loading = pressure. If you have high loadings, you have high pressures. Period.

The high loadings are from high _variations_ in pressure. The average pressure around the capsule is still equal to the ambient pressure. Leaks in the passenger compartment are almost certainly side-facing, so the capsule will equalize to the pressure of the air on the sides of the capsule (which will be close to ambient or likely below, due to the Bernoulli principle), not the higher pressure in front. And note that the variations in pressure don't have to be very high to cause serious buffeting. The Hyperloop capsule masses 15000kg, with a frontal cross-section of about 2 m^2. Applying an extra 1atm to the front of the capsule will decelerate it faster than 1g. If the air beneath the capsule transiently becomes about 0.03atm higher density than the air above (due to turbulence or ground effect), it will lift the entire capsule off the track. This is the worrisome high-speed aerodynamics I was talking about.

Slashdot Top Deals

No hardware designer should be allowed to produce any piece of hardware until three software guys have signed off for it. -- Andy Tanenbaum

Working...