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Posted by Jack Crossfire | Oct 06, 2014 @ 12:33 AM | 3,734 Views

Never build 1 when you can build 2 for twice the price. Everyone knows about Stennis space center, the A-1 test stand where the SSME & F-1 were tested. Lesser known is the even bigger B-1/B-2 test stand where the complete S-IC & shuttle core were test fired.

Little did you know an identical set of test stands was built in Huntsville, in an age long before Stennis. The mighty S1C test stand was built from 1960 - 1964 for $30 million & would test the 1st 4 S-IC stages. You can't even buy a house for $30 million, anymore.

...Continue Reading
Posted by Jack Crossfire | Oct 04, 2014 @ 03:16 AM | 3,587 Views
Had granola cerial with no pepto bismol, since it might interfere with nutrient absorption. At 9V, it did the actual 13.1 segment in 1h58m2s including red lights. Red lights took 30s. The fastest mile was 8m7s on the uphill. Speed was highly erratic, with some quarter mile segments going extremely fast. Any benefit from PWM regulation was lost to flips & spinouts. Steering was non functional. Ate a caffeine free powergel at 11.5mi, which went everywhere. Couldn't drive while eating. The 1Ah battery had no problem. Got a bowel movement at 13.72mi.
Posted by Jack Crossfire | Sep 30, 2014 @ 10:14 PM | 3,191 Views

The answer is still no. You can't make your own private router with 2 mile range out of a pair of LTE phones. As far as what can be deciphered from the hindi accents, it's not a point to point version of LTE but a way for devices to discover nearby devices. They broadcast a very brief 128 bit ID on the LTE physical layer which is directly received by devices within 500m, to allow device discovery, but the data communication is still over a paid, bandwidth capped, tower based LTE plan.

Of course, the hype is just as insane as the Intel Edison 2 weeks ago & the Google Tango before that. Does anyone remember what Google Tango was?
Posted by Jack Crossfire | Sep 29, 2014 @ 09:39 PM | 3,073 Views
Make It Wearable Finalists | Meet Team Nixie (1 min 52 sec)

Couldn't believe how many people actually thought it was real. It's another example of how millennials believe absolutely everything they're told, while we would always ask questions, 20 years ago. They're just as believing on the economy & politicians. Not sure why this is. Maybe they know a lot less about physics than us.

Besides the industrial design which obviously won't work & has nothing to do with the stated purpose of making it small, if it was something which actually flew, wind resistance still wouldn't be there. It still requires a pink marker or an image processing ASIC. It's actually smaller than the Edison board he's trying to base it on.

The problem with prototyping an optically guided follow cam, using a laptop for image processing, was the antenna on the transmitter always falling off. Those Chinese never gave any thought to how fragile a postage stamp was for soldering an antenna to. Once it breaks off, the trace is gone.

It really needs a breakout board with the voltage regulators & a surface mount antenna, which is not the optimum weight.
Posted by Jack Crossfire | Sep 27, 2014 @ 08:51 PM | 3,352 Views

Interesting nuggets from a long past coworker who went to Google 12 years ago & never looked back. After the winning the 2 largest IPO's of their time, he now works 20 hours/week, buys supercars, flies a Cessna for fun, has enough wealth to own a house. For all the bad parts of big corporations & the stories of Google eternally hanging its employees 1 foot out the door, a long term stint in that place creates possibilities you can't believe.

To be sure, his job seems dry. It's the same task people did 20 years ago: installing Linux distributions on servers. He made a go at physical computing in 2011, like everyone else, but it never became a replacement for the old job. For all the talk about robotics, Andy Rubin, & Sebastian Thrun, Google is still foremost a web application company & you will never encounter a robotics expert in your daily routine.

There's some novelty in photos taken by the generation which took the 1st digital camera photos. Because they're still a technological wonder to the guy taking them, they seem more significant.

It's another look at a parallel world where just installing Linux, going to Linux conferences, & taking digital photos are still big deals. If you can stay enthusiastic about 1 thing for 20 years, the rewards are huge, but it may be our generation is becoming the new generation of grandpas stuck in its own point in time, always seeing newness in what youngins see as obsolete.
Posted by Jack Crossfire | Sep 27, 2014 @ 12:20 AM | 2,675 Views

The 1st rover test was crazy fast. Visor was dripping sweat for the 1st time. Used new rover firmware which uses a linear PWM scale based on battery voltage. Set it to 9.5V. It was in the 7m50s range going downhill for 2 miles & the 8m range going uphill for 2 miles. The target pace is 8m20s going downhill, 8m40s going uphill. Might have to lowball the downhill speed to make the uphill speed accessible. The scaled PWM definitely pulled in the gap between starting & ending speed even though it's not the most accurate power regulation.

The fastest mile was 7m46s going downhill, which was way beyond any previous mile. GPS reported a 7m44s mile going uphill, but it must have been a glitch. Had a diarrhea break after 3 miles. After that, the phone measured a heart rate of 143 which quickly dropped to 115. There were many stops for flips & traffic, steeper hills where it dropped to 10m/mile.
Posted by Jack Crossfire | Sep 25, 2014 @ 09:02 PM | 2,919 Views

Did anyone know Gopro had its IPO last year? The story of the day during their IPO was world cup. Did anyone care about the world cup?

Interviewed there, years before the IPO. The manager was a jerk, had thousands of applicants, wanted a known quantity. Experience was no longer enough.

Their product is the best in a bad neighborhood, but still a POS. SD card failures need to be built into the recording pipeline. Rather than shutting down, it needs to try opening a new file. It also needs downloading recordings over Wifi.

Helas, stock traders have redirected the company's focus from improving the camera to creating a social network which is to be sold to Google. Gopro tube is the next Twitch. The buyout is going to be well over $10 billion, many times more than Twitch or the 'tube. Another batch of people aren't going to have to work anymore.
Posted by Jack Crossfire | Sep 25, 2014 @ 07:21 AM | 3,007 Views

document.getElementById("button").checked = false;


$(button).prop("checked", false);

It's not about common sense. It's about knowing the secret handshake.
Posted by Jack Crossfire | Sep 24, 2014 @ 03:23 AM | 3,105 Views

Though SpaceX never revealed any detailed diagrams of Falcon 9, they did reveal 1 low resolution diagram which was captured in a blog in 2008.

So the video was the LOX tank. The spheres in frame were carbon fiber helium tanks used to pressurize the LOX tank. The temperature in there was −297.33F. Helium liquifies at -452F, so the spheres would still work when submerged. The fuel is presumably pressurized with exhaust.

All of the stages use common bulkheads between fuel & oxidizer. There's nothing on the 1st stage, no public displays where you can see the plumbing up close, no diagrams.
Posted by Jack Crossfire | Sep 21, 2014 @ 10:33 PM | 2,672 Views
It seems like it shouldn't be a big deal to design a constant power supply for a rover. It just needs the same standard current sensor that every RC plane has. 3D Robotics actually donated a current sensor with integrated 5V regulator. The problem is the rover is too small to fit it anywhere.

Sadly, regulating power by making PWM proportional to voltage didn't work. The idea was higher voltage at lower duty cycle would be equal to lower voltage at higher duty cycle, but power still increased with increasing voltage. The motors aren't constant resistance for all voltage & there's an unknown power usage from automated steering. It wasn't as effective as a linear regulator, which was still not true power regulation.

3DR uses an INA169 current sensor, which is an op-amp calibrated to convert the voltage difference across a 0.0005R resistor into a known voltage range. Their current range is 90A, while the rover needs 2A.

That leaves building something out of a 1R resistor with an op-amp. The maximum voltage drop should be 2V with a maximum current at 2A, but it's actually PWM with the maximum current an unknown higher amount for a shorter duty cycle. Then the PWM result needs to be smoothed.

They limit the bandwidth with a .1uF & 110k described in the datasheet. Using 1/(2piRC) gives 14Hz. Your best bet is to probe the resistor output & smooth it as much as possible with a big cap.

Constant power remanes a bridge too far for something which also needs a suspension system. Some waveforms showed nothing abnormal.

Deriving PWM purely from voltage, no load, at 12.5V we have .19A 2.38W

At 10V, we have .20A 2W

At 9V, we have .24A 2.16W

As usual, the frequency response of the probe makes suspect voltage ranges.

With constant PWM for all voltage, we have

12.5V .43A 5.3W
10V .37A 3.7W
9V .33A 2.97W

So voltage derived PWM is better than nothing, in the normal voltage range.
Posted by Jack Crossfire | Sep 21, 2014 @ 03:25 AM | 2,742 Views
There were some intriguing views inside the Falcon 9 2nd stage fuel tank, during the CRS-4 launch. They showed brief segments as the depletion rate got faster & faster. Right before exhaustion, the blob stopped dropping & floated up in weightlessness, like a goo. There's no reserve in those launches. Kind of scary to see a giant webbed blob of fluid slowly floating towards you through the air, as if commanded by a mind of its own to drown you.

Falcon 9 fuel tank cam (0 min 46 sec)

Fuel tank cams are useful for showing the amount of actual reserve compared to the predicted reserve, how well it's settled on the bottom for an engine restart, how much it sloshes. Bonus footage: a timelapse of another launch

...Continue Reading
Posted by Jack Crossfire | Sep 19, 2014 @ 09:58 PM | 2,705 Views
Jeff Bezos has a way of showing up everywhere & where you least expect it. It wouldn't be surprising if the 2016 election happened, everyone voted for either Hillary or Biden & the winner was Bezos.

So after introducing the Kindle Voyage on Tuesday, Bezos was selected to produce the replacement for the RD-180 engine on Wednesday, pending a government contract. The BE-4 engine exists only in drawings, would burn liquid methane & liquid oxygen, & produce 550,000 lbs of thrust. 2 would power the Atlas-6 with slightly more than the RD-180's 933,000lbs.

Methane is now the fuel of choice in rocket engines. Now a rough comparison of the efficiency of the current fuels:

RS-25 LH2:
Isp (SL) 366 s

Raptor (conceptual methane engine):
Isp (SL) 321 s

RD-180 kerosine:
Isp (SL) 311 s

Merlin kerosine:
Isp (SL) 282s

Space shuttle booster:
Isp (SL) 242s

There could be a slight advantage in developing a methane 1st stage engine, depending on the cost of handling cryogenic methane, density, & mixture ratio.

Kerosene density: 810kg/m3
Liquid methane density: 422kg/m3
LH2 density: 71kg/m3

It needs twice the fuel tank size to get 10 more seconds of impulse.

Obviously, the change requires a new rocket, not just strapping on the new engine & putting cryogenic methane in the kerosine tank. It's hard to believe the program won't grow into a new Atlas 6, with a new EELV contract. Once again, what started with importing the RD-180 documents intending to replicate the engine becomes designing a new engine, then designing a whole new system because you might as well.

Of course, the voters could decide Russia isn't a problem & stick with the RD-180. It's going to be impossible to finance a methane 1st stage engine without the government.
Posted by Jack Crossfire | Sep 19, 2014 @ 12:05 AM | 2,534 Views

When you need money, strap leftover cells together in any way & sell them on sale. 2008 was a tough year for maxamps.com.

They were ganged in 3's to get 3300mAh. They flew many times, then puffed.

...Continue Reading
Posted by Jack Crossfire | Sep 18, 2014 @ 01:04 AM | 2,262 Views

This story resurfaced again. Pretty sure it has been used since 2010, but the internet has a short memory. More specifically, it's a powered vehicle dropped in the eye of the storm, where there is no wind. It's still impossible to control something that small in the eye wall, but what if someone tried to invent something?


The Coyote UAV was developed in Arizona in 2009 with Navy funding, then was acquired by BAE. It can handle 100mph winds. Pretty sure that's where dmgoedde was hired after his quest to sell attopilots ended & his software is still being used on the current flights.

He all but vanished after 2009. His last sign was in 2011 & he was still working on attopilot.


Making a micro vehicle handle high winds is a big deal. It's probably still a military capability. It would have to be nearly wingless. Don't think Dean disappeared because his work became militarized. He probably just got married, had a family, & moved on to the next step.
Posted by Jack Crossfire | Sep 17, 2014 @ 04:01 AM | 2,126 Views
OpenCV was last used in Cinelerra many years ago in an object replacement experiment. It sucked, so it was never put in the mane build system.

Object replacement with OpenCV & SURF (2 min 42 sec)

Now, it rises again in an attempt to do better at video stabilization. There are some simple stackoverflow examples, in addition to the hideously complex samples/cpp/videostab.cpp. It seems to detect features & optical flow reasonably well.

In modules/calib3d/include/opencv2/calib3d.hpp there's


for detecting homography.

In modules/videostab/include/opencv2/videostab/global_motion.hpp there's


for getting just translation, rotation, & scaling. Both return a matrix for an affine transform. Multiply the homography matrix to accumulate motion, but usually it zeros out the accumulator or crashes.

Thus begins your revelation that every CvMat needs to be manually initialized with a piece of memory allocated on your own. Different languages do it differently, but the C interface needs memory management. It's 1 of those projects where all the energy goes to porting to different languages just enough to get the buzzword on a white paper, but no language besides C++ is finished.

Ideally, everyone would interface OpenCV in C++, but the examples are split between many languages. When given a choice of translating languages or making something work, everyone says they want to port between 15 languages, but without a...Continue Reading
Posted by Jack Crossfire | Sep 15, 2014 @ 12:36 AM | 2,290 Views
So Peter Hollens signed with Sony, joining the growing legion of Gootube musicians who are hitting paydirt. The Piano Guys signed in 2012. Thought Valentina Lisitsa hit paydirt by signing with Decca or Mark Anderson hit paydirt by signing with Hyperion, but Sony is the gold standard. It's bigger than Decca, Hyperion, Deutsche Grammaphon, or Chandos.

Now that Minecraft was bought for $2.5 billion, allowing its founders to finally afford a small doghouse in silicon valley, the founders of Instagram must be hating their measly $1 billion buyout, the founders of Occulus Rift are seeing red over their $2 billion buyout, but all eyes are wondering what 3D Robotics is going to be sold for.

Then of course, there's linkedin. It definitely has a way of revealing how all those years of corner offices, opulent lifestyles, hiring & firing meetings, were the work of guys your own age, much less accomplished than you, but with well connected parents. The 1 singular IPO boom in 1999 secured the rest of their lives. They rode the train to retirement at age 40. Then the window closed, never to reopen again.

Could you have been that guy, done working & settled into a wealthy retirement with no more education than a BS degree by now?
Posted by Jack Crossfire | Sep 14, 2014 @ 02:34 AM | 2,146 Views

Friction stir welding hits mammoth heights in a machine that will spit out the world's largest fuel tanks in a single piece, pending funding. Or the welding tool could become another A3 test stand without funding.

There is a concept drawing of a completed LH2 tank in the machine. The completed core stage would be much taller than the machine. A lot of pieces still have to be built.

The thing is, if the core stage is just a shuttle external tank to minimize the cost of new tooling, how did they end up spending 10 years building new tooling to build exactly the same tank? The internet has said there's no point in reusing existing rocket parts, because there will always be requirements creepage.

The shuttle tank already used friction stir welding. The 1st 6 tanks used TIG welding. Most of the tanks used polarity plasma arc welding. The final tanks were friction stir welded. They never said how the VAC improves upon what was done before, though it seemed it could make the tanks in fewer pieces.
Posted by Jack Crossfire | Sep 12, 2014 @ 09:10 PM | 1,959 Views


After working in the set top box industry from its meteoric rise to its disintegration, these stories had some interest. By the time digital TV was finally mandated in 2009, the idea of towers blasting gigawatts of scheduled programming was already obsolete. Digital TV was amazing when its 1st blips appeared in 2002. Watching HD movies off the airwaves in 2005 was amazing. By 2009, the party was over.

Never actually watched anything on a commercial digital TV. Only watched some olympics by cobbling together mplayer, pcHDTV, or using custom software for day jobs.

5 years after mandating it, the FCC is already phasing out the digital TV spectrum. TV stations are already abandoning the transmitter in favor of the router. The solutions are wider, more packetized, but strictly private.

Radio spectrum is allocated like the 1920's when everything was private & the government decreed which private business got what. Even bridges were private in those days. Not sure it would all be private if radio was invented today. There would be cries for spectrum neutrality.
Posted by Jack Crossfire | Sep 10, 2014 @ 08:55 PM | 2,029 Views

It was sold out in 3 hours, despite being only an outdoor tour of the unrestricted area. They would not get into the giant wind tunnel, though they would get into the cafeteria, see the bench wind tunnels & RC planes. Surprising more hobbyists don't build bench wind tunnels. The cafeteria is probably the mane attraction, because that's where you actually see people who work on spaceships every day, after a very long line.

The dissapointment is of course that the voters fill up the event in 3 hours, yet when asked to fund a space program, the same voters consistently choose expanded mortage programs instead. You always hope the voters finally decide their granite countertops are worth enough, but they never do. There's always more money to be made from 1 more remodelling program, 1 more medicare program & 1 less space program.

Lockheed hopes to finally launch an unmanned test of Orion, after 11 years of program cancellations & budget cuts. It's scheduled for 2014, but probably won't happen until 2016. A 2nd unmanned test was scheduled for 2018, 15 years after the program started, with nothing funded afterwards. SpaceX has no schedule for Dragon 2 unless NASA can restore commercial crew funding, which is still 1/2 of the required amount.

A final downselect of commercial crew to 1 contractor was planned for August. When that was canceled, September became the moment. SpaceX will be the prime contractor, with a starvation ration given to Boeing, & SNC defunded. There's not much guesswork involved.