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Posted by Jack Crossfire | Dec 10, 2016 @ 10:40 PM | 2,094 Views
So the mane computer, the one which does 4k video, had always dropped connections with the Zoom 5345. The easiest way to reproduce the failure was trying to access 192.168.100.1, which always failed. After months of sporadic experiments, finally tried different kernel versions. It was the only computer still using 2.6, which it had used since 2010. On anything above 3.2.9, the network was perfect. The Zoom 5345 had a problem with Linux 2.6.


Tried Linux 4.8.9, but the NVidia driver for this kernel wasn't compatible with the obsolete graphics card. The graphics card is now 10 years old, but still plays 4k video in a 2.5k window. Downgraded the NVidia driver to the lowest version which could work with Linux 4.8.9 & the highest version which could work with the obsolete graphics card: NVidia 304, which required commenting out the MTRR functions to work with the new kernel. The driver compiled, but wasn't compatible with the X server. Downgraded the kernel to the lowest version which would work with the Zoom, the highest version which would work with the X server, & the lowest version which would work with the NVidia driver: Linux 3.2.9. The NVidia driver had to be downgraded to 295.


It worked, but finding components which overlap enough to keep Linux going on the current system is a lot harder than it used to be. Linux 3.2.9 came out in 2012. Eventually, routers won't support it either. Very cheap cable modems can't handle subtle changes in packet...Continue Reading
Posted by Jack Crossfire | Dec 10, 2016 @ 09:10 PM | 1,973 Views
Replaced a burned out LED & pointed the headlights forward.
Posted by Jack Crossfire | Dec 09, 2016 @ 11:49 PM | 2,108 Views
Iron Man released a video of a Merlin 1 nozzle being fabricated. It made sense for it to be formed around a plug on a lathe. The intriguing part was how everything else was jerryrigged. A bank of acetylene torches heat the work piece. The torch placement doesn't have to be very precise. The pressure from the flames pushes the metal down onto the plug. The torches have to be manually repositioned as the nozzle bends down & the torch fuel tanks have to be refilled. It seems to take many hours of painstaking manual labor, but launching 12 times per year only takes 120 engines, leaving 3 days to make each engine nozzle. It's far faster than braze welding thousands of tubes.



Judging from the thickness, the work piece already contains the cooling channels. It would have originally been a disk. 2 metal disks with radiating patterns of grooves would have been fused by a very large hydraulic press & heat. Then the bending of the fused disk around the nozzle plug would have retained the cooling channels. The method was probably 1st devised by the Russians.
Posted by Jack Crossfire | Dec 08, 2016 @ 12:43 AM | 1,668 Views
It's rarely covered anymore, but there were some nuggets about launches resuming on Dec 16.

http://spaceflightnow.com/2016/12/02...pad-explosion/

Then a few days later, it was delayed until 2017.

Although they will never release complete details on the last explosion, they did reveal supercooled oxygen froze solid & caused the helium tank to burst. That could mean a lot of things. It could be oxygen got into the carbon fiber laminations before freezing & expanding, ripping apart the laminations.

The real bummer for space fans was delivered in Dec 2015, months before the troubles with supercooled oxygen emerged. It was Tom Stafford's letter complaining about the need to fuel the rockets with astronauts aboard & the lack of recirculation pumps to prevent temperature fluctuations at the engine inlets.

http://spaceref.com/news/viewsr.html?pid=49548

If they don't take off immediately after fueling, the oxygen will heat up, but the last explosion confirmed fueling is too dangerous to do with astronauts on board. Tom was prescient, indeed.

The only thing that's going to happen is the simplest solution: for flying humans, they're going to drop supercooled oxygen & board the rocket after fueling is completed. They'll have to give up reusability for human missions. They never released any performance figures for supercooled oxygen, but it was probably more than they could gain by shedding weight. There's a chance the falcon heavy...Continue Reading
Posted by Jack Crossfire | Dec 07, 2016 @ 12:54 AM | 1,847 Views
ALL IN | ZACH MILLER at THE NORTH FACE EC San Francisco 2016 (3 min 20 sec)


That was a lot more stable than the Feiyu with home made firmware. That was narrow focal length, yet still spot on. The home made gimbal from 2013 was nowhere close to the Feiyu, either. Even this nugget on another Feiyu

A Run Up To Lion Lake! (11,000'/3353m) | Sage Canaday & Sandi Nypaver (2 min 19 sec)
...Continue Reading
Posted by Jack Crossfire | Nov 30, 2016 @ 08:39 PM | 2,430 Views
It took 45 years to develop LEDs which ran cool enough to equal incandescent lights. They finally did it. For someone who lived when their dim ancestors 1st appeared, it represents an extraordinary achievement. Something which takes 45 years is really hard. 10 years ago, early adopters of the 1st LED replacements for incandescent bulbs faced ungainly heatsinks which could barely light anything for $25. Another 10 years & they're finally practical.

Didn't measure the voltage of the LEDs, but based on the gootube videos, any LED replacement can be hacked to run on batteries as a set of headlights.
Posted by Jack Crossfire | Nov 30, 2016 @ 02:51 AM | 1,932 Views
Sam Cobb's Amazing Automata Sculptures! (6 min 25 sec)


A rare glimpse of how a single motor can control multiple limbs via a cam shaft. That's about all of the inner workings of an automaton you'll find on the goog. Making a self propelled quadruped by having a single powerful motor turn all the limbs was appealing but much more complex than multiple motors. Then, fully exploiting the ability of legs to overcome obstacles would require a full elevation map of the terrain & the logic to avoid the obstacles. It would be as complicated as building a Falcon 9, taking multiple lifetimes.


The good news is the DJI Mavic appears to be the 1st quad copter suitable for replacing ground based exercise robots. It would only work for 1 mile at a time, but it's finally stable enough to be controlled by the same single handed controller that the ground based robots use.
Posted by Jack Crossfire | Nov 27, 2016 @ 08:50 PM | 2,004 Views
Posted by Jack Crossfire | Nov 24, 2016 @ 11:26 PM | 1,892 Views
Managed to reconfigure it so the camera mounts the right way. That got it an inch higher & eliminated the need to rotate the video. Requiring any kind of processing just to preview the video was a disaster.

Optimized the UARTs so the feedback now goes at 1960Hz instead of 1830Hz. The trick was not doing anything else until the packet was transmitted. More speed came from setting the IMU sample rate divider to 0. It doesn't cause aliasing. It just reads the sample with lower latency. This might have reduced the bobbing slightly.

Another attempt to handle the UART transmitter using interrupts failed. It didn't matter since context switching would count as doing something else while the packet was transmitted. Tried delaying the feedback commands by 1 packet so the next IMU reading could be read before the previous readout's feedback calculations were done. While it would have increased the rate, it would have added latency. The increased latency was a failure.

Finally, extended the motor mixing to allow it to be used for selfies & near the ground. This took a bit of geometry.

Discovered the P & D feedback terms in their only working configuration don't fight each other. D actually adds to P, so fighting terms aren't the reason it undershoots. Tried maximizing P & D with no obvious improvement. Did confirm it slightly undershoots the feedback, leading to bobbing when running.

Tried replacing the traditional IMU blending algorithm, which...Continue Reading
Posted by Jack Crossfire | Nov 21, 2016 @ 10:22 PM | 1,958 Views
The last 18.6 mile drive was a long long time ago:

https://www.rcgroups.com/forums/show....php?t=2742360

For today's 18.5 mile drive, put battery 1 on the bottom & battery 2 on top. Battery 1 still gave 3.4Ah & battery 2 gave 4.5Ah, so the cable was not the limiting factor & hauling around drinks didn't make any difference. It was the internal resistance of the batteries. Battery 2 was dead by the end.


In other news, a rare teardown of the DJI Mavic rounded the blogs.

DJI Mavic detailed Teardown (19 min 22 sec)


It was another frustrating experience watching a millenial struggle through simple concepts & have no idea how things worked the way previous generations did.


The mane nugget was how the IMU has evolved from being randomly scattered on the mane board to being encapsulated in a very large, weighted, shock dampered enclosure, connected by a very long ribbon cable to reduce coupling. It matches what lions discovered years ago.


It was enlightening to discover lions were on the right track in their treatment of the IMU with a lot more packaging than the main processor, while everyone else was putting everything on a single board.
Posted by Jack Crossfire | Nov 19, 2016 @ 02:50 PM | 2,163 Views
The answer is yes. Cinelerra can play 3840x2160 in a 2560x1600 window at 30fps without any hardware acceleration, on the 7 year old AMD. For all those years, it seemed hopeless, but it had the power long before 4k cameras were around. It doesn't work so well in a 3840x2160 window, but the lion kingdom can't afford a 4k monitor. It requires some diabolical hacks, without which it only did 15fps for all those years.


XMovie used a file -> BGR8888 bitmap -> window pipeline back when computers could barely play 720x480. The only way to watch a movie was on XMovie. When computers got fast enough, XMovie went away & Cinelerra got away with using file -> YUV888 intermediate -> BGR8888 bitmap -> window to play everything up to 1920x1080. Once again, the limit of computing power has been reached & the intermediate copy needs to be skipped again.


It was surprising that file -> YUV888 intermediate -> OpenGL was slower than file -> BGR8888 bitmap -> window. OpenGL was always slower than software on this system, but it used a 10 year old graphics card.


The idea of optimizing it occurred while adding a colorspace converter for the new HDR codecs & remembering all the codecs still contain the scaling routines for XMovie to play on low end machines 17 years ago. There's also the fact that virtual machines, faster CPUs, & vanishing interest in PC video has made hardware acceleration in Linux go away & the old software BGR8888 bitmap has...Continue Reading
Posted by Jack Crossfire | Nov 16, 2016 @ 04:25 PM | 2,536 Views
Amusing that after all the money invested in the Antares rocket, having it explode then redesigning it for another engine, it didn't have enough power so they ended up going back to the Atlas V. Atlas V allows 700 more lbs of payload to the space station, bringing it to 8157 lbs. The most the Falcon 9 moved to the space station was 6914 lbs, but it recovered its 1st stage. The Falcon 9 is gone until next year, which means all the money spent on the commercial cargo program led to just 1 new spaceship launching on the same old rocket.


https://www.nasaspaceflight.com/2016...e-antares-rtf/
Posted by Jack Crossfire | Nov 14, 2016 @ 01:10 AM | 2,093 Views
Today's supermoon vs 2014 eclipse. It was only 1 pixel bigger than the 2014 supermoon.
Posted by Jack Crossfire | Nov 13, 2016 @ 09:55 PM | 2,009 Views
During a 10 mile drive,

Berkeley run 2 (3 min 2 sec)



passed the robotics meetup.

https://twitter.com/carlbass/status/797908532360134656

It was intriguing to see another lunchbox in his photos.

The warehouse had been recently renovated. There was a bathroom & desperately needed drinks for the lions running 10 miles with robots. The CEO of Autodesk owned it & might be trying to start a self driving car startup. Of course, all the bigwigs were long gone by the time the lion kingdom drove up & the crowd which much thinner.

There were a few hobbyists working on similar 1/10 vehicles. They were all using webcams & pi cams to try to navigate the indoor track. Documented just the track, in case inspiration struck. It's basically a line following problem, with lines of much less contrast than historic contests.

Started out in robotics by reading http://www.robotroom.com/ That guy was incredibly dedicated to just line following, for many years. Line following remanes a toy problem. The lion kingdom would be ecstatic if he focused just on a segment of pavement with variable shadows, rather than getting distracted by line following.

Speaking of Autodesk, as of 2013 SpaceX was using Siemens NX, not Autodesk Inventor for its CAD. Autodesk needs to buy out Siemens.
Discussion / Posted by Jack Crossfire / Nov 09, 2016 @ 12:36 PM / 2,100 Views / 0 Comments / Reply
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Posted by Jack Crossfire | Nov 06, 2016 @ 10:08 PM | 2,116 Views
Aquatic pier run timelapse 20:1 (4 min 31 sec)


A 3rd attempt to make this one look good. Software stabilization was horrible for most of it. Raw footage only looked stable when accelerated 20:1, but not 10:1 because the gimbal has an oscillating movement. So made the salient feature a software stabilized 5:1 segment with the rest at 20:1.

Then there was the new & improved bridge timelapse with no software stabilization:

Bay bridge bike path (6 min 27 sec)
...Continue Reading
Discussion / Posted by Jack Crossfire / Nov 04, 2016 @ 11:49 PM / 2,094 Views / 0 Comments / Reply
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Posted by Jack Crossfire | Nov 01, 2016 @ 11:14 PM | 2,438 Views
So fired up the video editor & made a spat of brushless gimbal timelapses for the 1st time in 3 years.

Pier 39 run timelapse (5 min 47 sec)


Coit timelapse (5 min 5 sec)
...Continue Reading
Posted by Jack Crossfire | Nov 01, 2016 @ 01:20 AM | 1,823 Views
So the helium bottles on the Falcon 9 are pressurized to 5000psi. A household propane tank is 300psi at most. They're submerged in the LOX to increase the amount of helium they can store & save space. In previous rockets, they sit in the LOX bath long after filling is complete, to equalize the temperature before being pressurized.

The new Falcon 9 has to take off immediately after tanking, in order to keep the LOX supercooled far below its boiling point. The helium bottles have to be filled before the LOX filling is complete & before their temperature equalizes. The trick is getting the helium the right temperature so the interior & exterior of the tank are the same temperature even as the exterior is still cooling down. There's probably a temperature differential they have to be within. If the helium is too cold, the exterior of the tank is shrinking slower than the interior & it sheers. If it's too hot, the interior is shrinking slower than the exterior & it sheers. An easy solution would be to move the helium tanks to the bottom of the LOX tank so they have more time to cool, but this would add weight & SpaceX wants to save money by tweeking the filling procedures.

Now we know the latest explosion happened when the helium bottles were being filled & someone in LA knew immediately what happened. Still not clear how a bursting carbon fiber tank in a pure LOX environment can ignite. Perhaps it damaged something on the service tower which ignited it.
Posted by Jack Crossfire | Oct 31, 2016 @ 10:48 PM | 1,776 Views
It helps to remember the 1st walking animals were 6 legged, 8 legged, or hundreds of legged. It took millions of years of evolution to go from flapping our entire bodies to legs.

Bio-Inspired Recon Robot (Man-Packable, All-Terrain Situational Awareness) (4 min 52 sec)


This one slowly but surely does the business. It took a few million more years to gain enough intelligence to get by on 4 legs.

A Simple 4-Legged Walking Robot (0 min 9 sec)
...Continue Reading