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Comments

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Russia Prepares For Internet War Over Malaysian Jet

the_other_chewey Re:Black box data streaming (503 comments)

My guess is cost. Sending data via satellite is very expensive, and there's a lot of data recorded. As for ground stations, I'm not aware of any plane-to-ground data communications currently in use (other than radio for voice) so that would need a completely new infrastructure built.

ACARS. Already built.
It's rather low-bandwidth though.

about a week ago
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Scotland Could Become Home To Britain's First Spaceport

the_other_chewey Re:Rather far north. (151 comments)

Nah mate, Ascension is closer to the equator and already has ESA facilities.

...and pretty much the coolest name ever for a place being used for space operations.

about two weeks ago
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SpaceX Falcon 9 Rocket Blasts Off From Florida

the_other_chewey Re:So was the landing successful? (112 comments)

trying for a soft touch down with enough rocket fuel ant oxidiser to do a soft touch down is always potentially exciting.

I knew Spacex has done some new and inventive things in propulsion systems.
But oxidising rocket fuel ants? That's just plain weird...
I guess the new facility in Texas will include their own ant farm to keep down cost.

about two weeks ago
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Walter Munk's Astonishing Wave-Tracking Experiment

the_other_chewey Re:Cheap documentary? (55 comments)

Just simple geometry:

Imagine a planet completely covered with water. Now throw in a big stone at one of the poles:
This results in a circular wave expanding from the pole, parallel to the latitudes.
As soon as it crosses the equator, it starts converging again, until it arrives as a peak at the
opposite pole.

Distance from pole to equator: circumference/4.

This works with a stone drop at any other point on the globe as well, I just used poles and
equator because it's easier to imagine. In reality, land masses complicate things a bit of course.

about two weeks ago
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Germany's Glut of Electricity Causing Prices To Plummet

the_other_chewey Re:WTF? (365 comments)

The prices per kW/h have risen year after year in Germany.

kWh, dammit. Go learn some very basic physics, or you won't even understand what you are being billed for.

about a month ago
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Half of Germany's Power Supplied By Solar, Briefly

the_other_chewey Re:Thanks for pointing out the "briefly" part. (461 comments)

So, yeah...in short: Germany's done a great job leading the way. But their power grid is 1/20th the size of ours in terms of power generation/usage, and their nation is also a fraction of ours in size. So what they did can't just be copied and pasted into the US to get us to the same proportion of renewable generation.

There is no German power grid: A huge part of Europe is part of a single, phase-synchronous
grid larger than any of the ones in the US. Germany is part of that grid.

Yes, storage of electricity from uncontrolled sources to always be able to match supply to demand on a
large scale is still pretty much an unsolved problem. It's being worked on.

But I'm sick of the "of course it works for them, but it can never work for us, because we're oh so totally
different!" argument. That's just not true, and you have no point.

If anything, the vast amount of empty space makes large-scale facilities of any kind easier. I'm not sure
large-scale anything is the solution though, distributed generation and storage seem the sensible thing to do.
And doing it is just a question of (political) will.

about a month ago
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Astronomers Solve Puzzle of Mysterious Streaks In Radio Images of the Sky

the_other_chewey Re:Cyclotron Radiation? (66 comments)

From the paper: "If a magnetic eld of 10 to 15 G were present within the trail, it follows that cyclotron radiation would be emitted at the observed frequencies by the electrons in the plasma. However, the surface geomagnetic eld is only 0.5 G, so this would require the generation of a strong magnetic eld by a reball, an eect that has never been observed."

Hey, you! Your ligatures aren't showing!

about a month and a half ago
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SpaceX Shows Off 7-Man Dragon V2 Capsule

the_other_chewey Re:What else is needed... Rocket engines (140 comments)

Maybe the small matter of getting the thing into space using a rocket engine is why they still need the Russians.

Uh? SpaceX build all their engines in-house.

Consider, for instance, that the Soyuz TMA-M can hang around the space station for 6 months, and be ready for use to return astronauts safely back to Earth, without a maintenance crew having to go and check every nut and bolt - a feat that even the Space Shuttle could never muster (for the record, the Space Shuttle had a mission duration of about 12 days - a few Columbia missions went up to 16/17 days).

That's a human consumables issue. Nobody is living in those Soyuz during that time.
They never tried something like this with the Shuttle, but just docking an empty one for
a couple of months would probably have worked too. A Shuttle landing never required
a maintenance crew (although, in hindsight, this would've been nice. The known problems
were still all launch issues though).

Another example is that it takes the Soyuz just 6 hours to go from launch to docking with the space station (for comparison, it took the space shuttle almost 3 days to reach the space station after launch).

That's a very recent development. It has been used how often now, three, four times?
And of those times, it failed once, falling back to the traditional 3-4 day approach.
Also, it only works because the ISS's orbit has been altered to accomodate this approach mode.
And there's no reason precluding Dragon from doing the same.

There are many other little things like these that are not cool or sexy, but make the ruthless efficiency and effectiveness with which the Soyuz executes and fulfils its purpose is second to none.

It has a very, very impressive track record. Matching this will - by definition - take time and many flights.
But I don't see any capability making Soyuz inherently superior to the alternatives in development.
However, it is about to lose big on price, which is a big one.

about 2 months ago
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How LEDs Are Made

the_other_chewey Re:left out the most important steps (93 comments)

Two factors:

- size doesn't matter (that much): For CPUs, you are creating large (relatively speaking) rectangular
objects on a circle. Thus, the closer your circle outline approaches a straight line (i.e., the larger the circle is),
the less waste silicon you have to cut away. For tiny LED dies, you can basically use the full circle even on
smaller wafers.

- For CPUs, the price is in the processing; for LEDs, it's the materials: LED structures are gigantic compared
to those found on a CPU. They are built using a handful of low precision (again, relatively speaking) production
steps. CPU production is as close to magic as we can nowadays get and uses dozens to hundreds of processing
steps (a wafer for a modern CPU spends about a month inside the fab), where a machine for a single step costs
millions. The cost for the raw wafer itself really doesn't matter.


So:

LEDs are cheap and fast to manufacture, and basically fit on arbitrary wafer shapes:
Raw material prices matter, wafer waste is minimal and doesn't. --> cheap, small wafers.

CPUs are damn hard and slow to manufacture, really only fit on rectangles:
Who cares about wafer prices, but we want optimal yield per processed wafer, so as to have
as little waste as possible --> wafers as large as possible, damn the cost of the wafer.


And lastly: There is no structure size progress in LEDs as there is with CPUs: Once you have a
factory for LEDs, you can use it for a while without upgrading to the newest and smallest process
all the time. So why buy new equipment if the old is perfectly competitive?

about 2 months ago
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Ford's Bringing Adaptive Steering To the Masses

the_other_chewey Re:Ghost in the machine (128 comments)

I remember reading about a vehicle made in Europe that was completely drive-by-wire with no mechanical linkages whatsoever.

This might have been the Mercedes-Benz F200 concept car -
driven by completely electronic sidesticks.

This allowed for some cool features, e.g. completely vibration-free controls on
cobblestones while the electronic steering made continuous tiny adjustments to
the front wheels.

It also means it had no chance to be certified for public roads.

about 2 months ago
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Happy 95th Anniversary, Relativity

the_other_chewey Re:95 years but (120 comments)

Exactly my point. The light in Cherenkov radiation isn't travelling faster than c, it's just going faster than the "c" for that medium.

The particle triggering the radiation is, the Cherenkov photons themselves are not -
that's what makes those nice Mach-like Cherenkov cones.

about 2 months ago
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SpaceX To Present Manned Dragon Capsule

the_other_chewey Re:Seven crew? (128 comments)

Seven crew means it can be used as an escape capsule for the ISS.

Well, for seven of them, anyway. There have been times when there have been a dozen people aboard the ISS.

Not as ISS crew. This was only temporarily, while the Shuttle was visiting (record number
of people on board the ISS is 13, but just for a couple of days: 6 ISS + 7 Shuttle).

ISS design crew initially was 7 - but that has been reduced to 6 for the time being,
due to the unavailability of full crew rescue vehicles.

At the moment, 2x Soyuz are used as escape pods. A parked Dragon would help to get
back to the initial crew size and free up a docking port. Very cool.

about 2 months ago
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Google Unveils Self-Driving Car With No Steering Wheel

the_other_chewey Re:No steering wheel? No deal. (583 comments)

CAT III landing require autopilot, as per guidelines.

Correct.

CAT III weather minima do not provide sufficient visual references to allow a manual landing to be made. CAT III minima depend on roll-out control and redundancy of the autopilot. because they give only enough time for the pilot to decide whether the aircraft will land in the touchdown zone (basically CAT IIIa) and to ensure safety during rollout (basically CAT IIIb). Therefore an automatic landing system is mandatory to perform Category III operations.

Yeah. What's your point? Nothing prevents you from performing a CAT III landing
under cloudless skies in bright sunshine. You wouldn't normally do that though, because
it's a lot of work to set up and monitor, and just visually landing your aircraft is much easier.

The grandparent however claims CAT III autolands to be happening most of the time,
regardless of weather conditions.

I doubt that.

about 2 months ago
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Google Unveils Self-Driving Car With No Steering Wheel

the_other_chewey Re:No steering wheel? No deal. (583 comments)

I'm afraid your assertion is quite false - about 90% of all landings done daily by large civil aircraft (737 upward) is done by the autoland system, with the only requirement for a manual landing being to retain certification for the pilot.

Using ILS, I totally believe. Full autoland, i.e. flare, touchdown, rollout: I'd like to see a very good source.

Considering that autoland requires that the runway be equipped with ILS CAT III(b), this seems unlikely: China has one FAA approved CAT III runway, Hong Kong 25R.

There are none in Singapore, none in Thailand, there's one in Australia (Melbourne 16), three in India (all the same airport though, Delhi).

Of the 1369 ILS-equipped runways in the US (Excel warning), just 113 have CAT III (no idea whether those are level a or b).

Sure, most of them are at the biggest an busiest airports, but considering that an autolanding
plane severely limits a runway's capacity due to increased spacing requirements, I doubt ATC
would be too happy to accomodate lots of autolands especially on those.

They just don't have the timeslots.

about 2 months ago
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Google Unveils Self-Driving Car With No Steering Wheel

the_other_chewey Re:No steering wheel? No deal. (583 comments)

That is true, the video does not show autoland. But the rest remains, the plane "flys itself" along the programmed heading, speed and altitude.

The pilots fly the plane by programming heading, speed, and altitude.

This system could go haywire anytime and basically not return control to the pilot, since it is all software between the pilot and the hardware.

This is untrue. First, there is no "this system", there are several completely independent systems
that can be individually disabled if something misbehaves. Also, great care is taken to allow the
pilots to easily assume full control: In most cases, it's as simple as "touch the sidestick or throttle
levers".

And then, as the very last fallback, even Airbus aircraft have a "Mechanical Back Up" flight mode.
It is exactly that: No flight control computer involvement at all. No fun to fly either, mind you (can't
use the sidestick), but it is there, and controlling and landing the aircraft in this mode is trained for.

about 2 months ago
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Google Unveils Self-Driving Car With No Steering Wheel

the_other_chewey Re:No steering wheel? No deal. (583 comments)

Just look at this: https://www.youtube.com/watch?... (look ma no hands)

While the A380 is capable of autolands on properly equipped runways (which by the way
takes quite a bit of work by the pilots to set up), this video doesn't show one.

Final approach and landing are in fact flown in full manual mode. It's Lufthansa policy
to land manually whenever possible, as to not lose manual flying proficiency.

Other airlines do have other policies, but I doubt any use autolands routinely -
as I said, they are more work.

about 2 months ago
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Is It Really GPS If It Doesn't Use Satellites?

the_other_chewey Re:depends. (298 comments)

Well, the device in your link does not measure 'gravity fields' or 'gradients of whatever'. It measures the attraction of two masses to each other, which is completely uneffected from earth local gravity field/distortion/gradient or anything.

No it isn't. Where does the attraction come from and how is it transmitted?
What happens if Earth is used as one of the test masses?

And now take the not perfectly radial field of Earth, attraction measurements in multiple
axes, and you get a full tensor gradiometer.
Which by the way is not some fictitious device, but has been deployed on submarines
for decades – and it works pretty well, despite those subs being "in the exact same field"
as their surroundings.

Next try?

No, sorry, two is enough. Learn some physics first.

about 2 months ago
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Is It Really GPS If It Doesn't Use Satellites?

the_other_chewey Re:Does it give you a position on the globe? (298 comments)

Decades ago the US GPS gave wrong coordinates to civilians, a few 10 meters off. That is what I call distortion.

Deliberate distortion, aka "selective availability" was turned off.
There are multiple other sources of distortion.

The ionosphere does not distort or hinder GPS signals, why should it? The signals are in the wrong wavelength for that, and: they come from the outside. Again: easy to google.

Yeah, you should really give this google thing a try:

GPS and Ionosphere
The influence of the ionosphere on GPS Operations (contains a nice "Summary of GPS Errors")
Ionospheric Effects on GPS
There even are pretty pictures.

about 2 months ago
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Is It Really GPS If It Doesn't Use Satellites?

the_other_chewey Re:depends. (298 comments)

And how do you dream up to measure a gravitational field when everything involved is in the exact same field?

With a very sensitive scale. First done over 200 years ago.
Solid-state versions of this do exist today, although none would fit in a phone.
It is not "the exact same field": gradients are everywhere, and measureable.

about 2 months ago

Submissions

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SpaceX successfully test nine-engine-cluster

the_other_chewey the_other_chewey writes  |  more than 5 years ago

the_other_chewey (1119125) writes "On their test facility in Texas,SpaceX, the privately funded space-flight company, have successfully tested their nine-engine-cluster which is planned to provide the heavy lifting capability for their Falcon 9 and Falcon 9 Heavy rockets.

The firing lasted three minutes (a full "mission duty cycle", i.e. a simulated launch) under full power, delivering 3.8MN (or 855,000 lbs.) of thrust. SpaceX have made a video of the test available. The Waco Tribune has a short report about it, with comments by locals."

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