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Comment: Re:15 minutes buffer ? (Score 3, Interesting) 442

by brambus (#49364851) Attached to: Why the Final Moments Inside a Cockpit Are Heard But Not Seen
Agreed, and this is already how the cockpit voice recorder (CVR) works, but it records for a lot longer (around 24 hours, IIRC). Personally, as a pilot I wouldn't mind a 24-hour circular video buffer that's stored on the airplane and not automatically archived unless there's an incident - in that situation, I'd wanna have as much data available as possible, as that improves the chance of preventing a future occurrence. Preferably not just a wide-angle lens inside of the cockpit, but also perhaps a closeup of the instrument panel so that indications displayed to pilots are clearly visible.
ATC operators are already being filmed left and right (in addition to voice recorded) when they're at their stations and the footage is archived as well, so why should pilots not be similarly scrutinized is beyond me.

Comment: Re:Photosynthesis thumbs up! (Score 1) 65

by brambus (#49224735) Attached to: Solar Impulse Plane Begins Epic Global Flight
Fully agree here, a solar-powered blimp might actually not be such a bad idea, especially when your goal is primarily loitering for hours on end over something like a race track, or conducting traffic surveillance. However, for transport, especially mid- to long-distance transport, it's a horrible idea. It's akin to placing solar panels on roofs of cars and expecting to be able to use it practically, except much worse due to the much higher drag and power requirements of airplanes.

Comment: Re:Five months? (Score 1) 65

by brambus (#49219539) Attached to: Solar Impulse Plane Begins Epic Global Flight

Just as well not everyone is as limited in their imagination as you.

Please do give me a call when your imagination figures out a way to break the laws of physics. There's no problem with having your head in the clouds, as long as your feet are firmly on the ground. No amount of inventive imagination is going to let you circumvent things like conservation of energy.

Comment: Re:Photosynthesis thumbs up! (Score 1) 65

by brambus (#49219451) Attached to: Solar Impulse Plane Begins Epic Global Flight

A Boeing 777 is designed for speed. If you're not in a hurry, solar power might just be a reasonable option very soon.

No, a Boeing 777 is built for efficiency and "good enough" speed. High speed rail is already killing short-haul aviation in many places around the world.
Anyway, let's play this game. How slow is slow enough? The Solar Impulse cruises at 35 knots true airspeed - given upper altitude winds, your actual ground speed might in fact be negative on many days. Just to give you a taster of the energy requirements of "slow" flight (I have the actual manufacturer perf tables): at the lightest loadout (10000 lbs) and lowest and most economical cruise power setting, a 19-passenger Beechcraft 1900D airliner cruises at 25000 feet at 209 KTAS and requires 502 kW of power to do so (2 x 1400 rpm x 1266 lbft). It's surface area is probably less than 1/10 of that of the Solar Impulse. So even assuming 100% efficient power conversion, you're more than an order of magnitude removed. And that's assuming huge concessions to the lightness of the airplane (~3t empty airplane to carry 19 passengers - totally unrealistic), which given current electrical component & battery weight is just pure science fiction.

Comment: Re:Five months? (Score 1) 65

by brambus (#49218971) Attached to: Solar Impulse Plane Begins Epic Global Flight
Oh yeah, the safety is a whole other matter :) The reason I took it from a physics angle is that if the basic physics isn't there, we don't even need to consider the question of safety and risks (which are, to a much larger degree, qualitative). It'd be like discussing the safety implications of intergalactic wormhole transportation technology.

Comment: Re:Five months? (Score 1) 65

by brambus (#49217057) Attached to: Solar Impulse Plane Begins Epic Global Flight
I know they charge during the day and use that to run during the night, however, that's not really addressing the basic power requirement problem.
I'm glad to see you acknowledge that this is probably not realistic to power an airliner and I'm sorry to put a dampening on your hopes for this being used to power on-board systems. The electrical draw in an airplane is minuscule compared to the mechanical load of just moving the airplane through the air. As I've calculated, the 777 requires about 100 MW of power to cruise. I'd be surprised if the electrical load was anything more than 1/1000 of that (100 kW) - pretty much a drop in a bucket when it comes to the engines. A much higher load, in fact, are things like bleed air (used to pressurize the cabin, among other things) and anti-ice systems. The electrical load is in fact so small, that modern commercial airliners have a thing called a RAT (Ram Air Turbine), a miniature windmill electrical generator, that serves as a backup should all on-board power generation fail (which is triple-redundant in the 777) and is capable of providing several kW worth of last-resort backup power for things like avionics, electrical hydraulic pumps and emergency lighting.

Comment: Re:Solar constant is 1kW/m^2. No way around that. (Score 1) 65

by brambus (#49215491) Attached to: Solar Impulse Plane Begins Epic Global Flight
If the Solar Impulse project is anything to go by, it's hopelessly dependent on good weather to be able to sustain flight. For example, if you were dealing with aviation on a regular basis, you'd know that there are these things called "upper altitude winds" which regularly reach speeds in excess of 100kts even at fairly low altitudes (~10000-15000 ft) and given that the Solar Impulse's cruise speed is around 35 kts, it'd simply get blown all around the place, almost like a balloon. At that point, you might as well just junk the idea of heavier than air flight and just stick your comms antennas on a solar-powered blimp. And given the atrocious coverage such a system would provide vs. space satellites, means you'd need probably like tens of thousands of those in constant upkeep, just to give you decent coverage. For global "satcom" phone coverage, it's much easier to just launch 20-30 small polar orbit satellites, which are on stable orbits and give you global coverage at the same time - and we've already done that. For internet access and broadcasting, just build radio masts, which are cheap as heck and require almost no maintenance, or a couple of high-power GEO satellites to cover a whole continent - and we've already done that too. And as for NGOs and high-altitude surveillance, what you want is a blimp, not an airplane.
Put simply, solar-powered airplanes are a solution in search of a problem.

Comment: Re:Five months? (Score 2) 65

by brambus (#49215213) Attached to: Solar Impulse Plane Begins Epic Global Flight

Whether we'll be seeing solar air transport on a commercial level in my lifetime or not, they're definitely attacking various engineering, scientific and social problems in a high-profile way.

I love the forward thinking and positive view of technology including solar power, but there's no way there are ever going to be purely *directly* solar powered commercial airplanes in the future. The power requirements are just so far removed from being able to fly at anywhere near the speeds you may want to travel at to make it a viable mode of transport. Just to give you a taste of the energy requirements needed for air travel, let's have a look at a modern airliner, .e.g a Boeing 777-200LR. From experience, I can tell you that its engines run at about 40-45% of maximum rated sea level thrust in cruise at a speed of about M0.84, which at 35000 ft pressure altitude comes to around 480 knots true air speed or about 250m/s. Max sea level thrust on the GE90-115B is ~500 kN, so at say 40% thrust those engines are producing about 400 kN total. As you know, work = force x distance and since power = work / time, the power consumption required, just to keep the airplane in cruise is 400000 x 250, or about 100MW. Now assuming even a 100% efficient solar panel (about 1kW/m^2), you'd need about 100000 square meters of panel, or about a third of a kilometer on a side. Meanwhile, the actual top-down looking surface area of a 777 is approximately 2 orders of magnitude less than that. And any increase in surface area beyond that dramatically increases drag and the resulting energy requirements. And that's with a hypothetical 100% efficient solar panel (in actual fact, best lab results are about 35-40% efficient). Put simply, even from first principles, the idea of a solar-powered commercial airplane is just a non-starter.

Comment: Re:c++? (Score 1) 407

As far as the example you give, this is because C++ always adheres to the "zero-cost principle"

Also describable as the "zero-flexibility principle". In Objective-C extending existing code is super trivial. In C++, unless the author of your library *expected* what you're about to do, you're pretty much SOL. For example implementing a native RPC mechanism in Objective-C is about as complicated as implementing -forwardInvocation: and ferrying the serialized NSInvocation object between sockets. In C++, it just can't be done (well, unless you're willing to write some sort of custom VM!). Also, in practice, the overhead of Objective-C's dynamism is pretty much negligible (speaking from experience having written some pretty heavily real-time code for video streaming in Objective-C that's running the server-facing portion of a few dozen thousand STBs in the field right now). 90% of the time you're running 10% of your code. Write that portion in highly optimized pure C and the rest in objects and you'll get the best of both worlds.

For programmers like me who value C++ primarily for it's runtime efficiency, this is absolutely the correct design decision.

TBH, I've never seen the logic of this statement. Given that most code written in pretty much any app is just high-level scaffolding around a few really core high-perf algorithms, why try and shoehorn the same language into these two completely different usage scenarios. That's IMO asinine and C++'s extreme levels of complexity and sheer volume of features is a testament to that fact.

BTW, you're a bit out of date regarding C++ and allocation. Modern C++ now has several built-in smart pointers (including ref-counted versions) which makes modern C++ feel a lot closer to C# with it's garbage collection than to C-style manual memory management.

I stopped paying attention to C++ by the time the spec document collapsed under its own gravity to form a black hole.

Comment: Re:Objective-C is a lot of work (Score 1) 407

Wait, so you're porting or implementing it anew? One is not the other. Also, runtime != base library. Did you try to port the base library, or the runtime? Porting or even rewriting the runtime is pretty straightforward and I'm aware of at least one project where a single person did it without much trouble. The base library, yeah, a lot less simple, but still simpler than writing a new stdc++. Also share your sentiment on C++. It's way, way too big for my tastes. For the kinds of work I do (systems stuff, OS stuff, like you), C is plenty expressive enough.

Comment: Re:Objective-C is a lot of work (Score 1) 407

Implementing a new Base Library is hard, I've gotten a tiny subset working on my own to see just what is involved. I wouldn't recommend writing the full thing unless you have a burning desire to do it.

Contrast with implementing the C++ base libraries (such as the STL) and you'll quickly see which is simpler. The real difference is that C++ already has more implementations for more platforms. I agree with your conclusion - availability can make its use for your project a non-starter. However, unless we're talking about pretty weird embedded stuff or some weird OS platform like Haiku or something, GNUstep has been already been ported to lots and lots of platforms (including most of the major *nixes and Windows).

Comment: Re:c++? (Score 1) 407

Dynamic binding and loading is ugly and clunky.

So dynamic binding and loading is ugly and clunky. Remember this boys and girls...

It's much more touchy about types and is geared toward catching as much as it can at compile time.

And the reason for that is because it's statically bound (well, for the most part, apart from "virtual" methods). It has dick-all to do with "correctness" or whatever. It's simply because even if a subclass has its own implementation of a parent's method, it'll still call the parent method - this goes against one of the core principles of OO: polymorphism. This means that even *if* you wanted to override a method from a parent class in your subclass, unless the parent has it marked as virtual, you're SOL. In Objective-C, meanwhile, it'll work exactly as you'd expect - the child method will get called. Also don't assume that simply because Objective-C is dynamically bound that it doesn't watch your fingers. If you aren't a stupid programmer and have warnings turned on, it'll warn you of weird stuff, such as sending a message to an object of a class which is not known to have it declared. I've written a fair amount of Objective-C code and only encountered sending an incorrect message to an object a few times. Now allocation-related stuff, that's the killer! But it's the same in both languages (in fact, one could argue that ObjC is a bit better, as it at least gives you a ref-count garbage collector, whereas in C++ you're on your own).

[C++ is] big and clunky, has a lot of rules to memorize and its error messages are hideous.

And so now C++ is the clunky one? TBH, it really comes down to personal preference. I like dynamically bound languages, because it fits my style of thinking. If you're writing complex interactions between objects, it cuts down on the amount of code needed to write quite a bit and if you follow the suggestions of the compiler, you're very unlikely to shoot yourself in the foot. OTOH, I understand that if you're after 100% valid programs where static analysis gives you a lot of confidence ahead of time, then C++ is probably the way to go (although I'd prefer C in that case). It's really about style and personal preference. Neither is more or less clunky, it depends on what you want to do with and how you want to do it.

"Now this is a totally brain damaged algorithm. Gag me with a smurfette." -- P. Buhr, Computer Science 354

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