SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Jack Crossfire's blog
Posted by Jack Crossfire | Sep 24, 2014 @ 03:23 AM | 3,031 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 | 2,600 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 | 2,665 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 | 2,626 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 | 2,461 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 | 2,184 Views
http://www.livescience.com/47887-noa...hurricane.html

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?

http://defense-update.com/20100123_coyote.html

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.

http://www.suasnews.com/2010/10/2353...ntrol-station/

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 | 2,035 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

findHomography

for detecting homography.

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

estimateGlobalMotionRansac

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 | 2,215 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 | 2,081 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 | 1,886 Views
http://www.kcet.org/about/pressroom/...rtnership.html


http://www.networkworld.com/article/...-stations.html


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 | 1,964 Views
https://www.eventbrite.com/e/nasa-am...ts-12709172477

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.
Posted by Jack Crossfire | Sep 09, 2014 @ 06:19 AM | 1,629 Views
So the Linux derivatives seem to have become stable enough in the last 5 years that something compiled on 2010 era Fedora 13 with just enough of the libraries static actually runs on 2014 era Ubuntu 14.04.1. libc-2.12 is forwards compatible with libc-2.19 but libc-2.19 is not backwards compatible.

With that, the next Cinelerra release reintroduced the concept of a precompiled binary for the 1st time in decades. Cinelerra only works because most of its libraries are static. Libraries as mundane as JPEG & TIFF still undergo constant redesigns, many times per year.

The idea has always been to make as many libraries static as possible. The C library could not be static because of a problem with runtime linking modules. Other libraries seemed stable enough to dynamically link. Even then, it's not as self contained as Firefox.

It's a small miracle that Firefox/Mozilla/Netscape has always worked in binary form. They just put all of its libraries in a self contained directory & tested against every single operating system. Google Earth tries the same thing with less success. It would be a good idea to put the rest of Cinelerra's libraries except the C library in its own directory.

Sadly, this kind of software is not economically viable. Computer science these days is about learning new languages, not using the languages.
Posted by Jack Crossfire | Sep 07, 2014 @ 08:58 PM | 2,365 Views
After some restless nights of ghost problems, it was finally time to nail down the problem. It turned out, only 1.5 miles from the apartment, hidden from view by centuries of real estate development, was a very very old house, the oldest building in Rain Ramon.


It was a true relic of Donner party lore. After giving up on the idea that the Donner party was remotely connected to the valley, it turned out this connection was just around the bend.

Once above the fence, your phone reveals exactly what came out of a mind which drove the 1st wagon train through Hasting's cutoff, hand pulled a wagon down the virgin Weber canyon & drove oxen across the salt lake desert for 80 miles without water.


After arriving in 1846, making a fortune in the gold rush, Joel Harlan built it in 1852 farther south, moved it here in 1856 after property taxes went up, & died here in 1875 at the ripe old age of 46. The ordeal of Hasting's cutoff undoubtedly contributed to that.

...Continue Reading
Posted by Jack Crossfire | Sep 07, 2014 @ 02:15 AM | 1,787 Views
Tried apt-get freeglut3-dev on the mac & it showed the OpenGL shading language extension was there. After a few segmentation faults & another round of hardening bcpbuffer, the mac did the OpenGL business, 60fps with it on & 44fps with it off. There might be a bit somewhere limiting it to 60fps. It was doing 120fps, decades ago. A 60fps limit may have been added to simplify video programming.

It wasn't tried on anything besides NVidia since 2005. Getting it to work on Nvidia required using NVidia's own header files, but at least they complied with the OpenGL spec. ATI was their only competitor at the time & they only supported the OpenGL ARB extension. It would have taken a 2nd branch to support ATI. ATI did nothing to support shading in the standard Linux base.

Decades later, Intel took the laptop market from ATI & got it done. The shading language was finally included in the Ubunt header files, & Intel finally exposed shading in OpenGL.
Posted by Jack Crossfire | Sep 05, 2014 @ 08:41 PM | 1,873 Views



So heroine's hard drive began failing after only 4 years, so it was time to start backing things up on whatever other smaller hard drives were available until funds appeared for buying a new one. Looking through 10 years of files to decide what to keep is a good reminder of how little you've accomplished.




Posted by Jack Crossfire | Sep 05, 2014 @ 12:01 AM | 2,380 Views
http://www.dcrainmaker.com/blog

Being raised by a well connected parent in Washington DC can definitely get you a very high paying career with no college education & a life without financial worries.

The big thing now is ultrarunning. Everyone's running 100 miles. All the fitness gadgets are marketed towards these guys. They now make more money from people running 100 miles than people running 5 miles. Onward & upward human biology goes.

Compared to 30 years ago, technology is everywhere. Take your pick from traditional networking equipment jobs to now fitness tracking/telematics/telemedicine/smart homes/smart workspaces/smart toys/wearable computing/quantum computing/near field computing/cloud computing/3D printing/3D scanning/speech recognition/gesture recognition/virtual reality/augmented reality/big data/cryptography/cryptocurrency/computer security/drones/internet of things jobs.

It's just a case of your side of the mountain getting discovered by the cool kids. Technology is no longer a niche for geeks. It's the new football. All the cool kids write hashing algorithms while the loners play ball, & it's harder than hell to make money at it.
Posted by Jack Crossfire | Sep 01, 2014 @ 09:24 PM | 1,705 Views
Once stuck to cvs as long as possible before surrendering to svn. Stuck to svn during the bitkeeper & perforce craze, but after 2 years of employers demanding 50 years of git experience, the mac migration was finally a good time to migrate to git. Having now lived through cvs, svn, bitkeeper, perforce, & git, git is the current summer blockbuster, an entertaining step forwards in some ways & backwards in other ways until next season. Now the cheat sheet.

svn: configure svnserve, create fake user, create mane repository, look up how to fix broken configuration files & broken permissions

git: every checkout is a repository accessed through ssh. Create & copy .ssh/id_rsa.pub to .ssh/authorized_keys to allow a user to check out.

It's 1 less copy of the source code to worry about. A checkout is not bound to a single repository. If the repository goes away, the checkout can use another one.

svn: import spagetti commands
git: init spagetti commands, then git add .

svn: ci
git: commit

svn: co
git: clone

svn: up
git: pull

The killer with git is of course

cvs: can't add symbolic links
git: can't add empty directories
svn: what you got out was exactly what you put in

so we're back to fudging build systems & spending hours tracking down what the revision system left out.

cvs: always corrupted
svn: constant berkeley DB & version incompatibility errors
git: seems stable


svn: obscure G, C, U flags when merging
git: nifty +- progress bar when merging


The usual workflow with SVN:

svn ci -mx guicast cinelerra plugins
svn up guicast cinelerra plugins

The workflow with GIT appears to be:


git status -> shows what files changed
git add -> stages changed files
git commit -mx guicast cinelerra plugins
doesn't do anything unless files are added

git fetch
git checkout FETCH_HEAD

It's a bit more laborious. Working on individual directories requires specifying just those files to git add & specifying just those directories to git checkout. Replacing something with the repository version:

svn up filename
git checkout HEAD filename
Posted by Jack Crossfire | Aug 31, 2014 @ 08:55 PM | 1,676 Views

The Asus batteries each lasted only 8 months. Then it was time for the final laptop: the macbook. After much debate, it was decided to dual boot it instead of erasing MacOS completely. Still remember walking out of Stonehenge mall one night, with that thing neatly packaged in its pristine cardboard box, the perfect packaging, the new mac smell. It's a very strange laptop, more like a stone tablet.

An SD card Ubuntu installation failed with MMC driver crashes. Trying to burn the DVD on the mac would always wrap the iso file in another iso file. Finally got it to install from a DVD burned on a Linux box. The installer couldn't initialize the network at all, but it ended up not necessary.

Booting from the DVD requires holding down option to get into the firmer bootloader. Not sure those refit or refind bootloaders are required, since they just go into grub. Once installed, any of the EFI options seems to go into grub, which can then go into bunt.

With a terminal program finally installed, it was possible to load the b43 wifi driver, see the error message, load the required firmware from an SD card, & configure the network manually.

The macbook's audio, suspend mode, & 2D graphics seemed to work, a rarity for Linux. Wifi was intermittent. The keyboard & single button mouse are a buster. The current commands which create alternate mouse buttons:

xev
xmodmap -e "keycode 108 = Pointer_Button3"
xmodmap -e "keycode 134 =...Continue Reading
Posted by Jack Crossfire | Aug 29, 2014 @ 04:12 AM | 1,979 Views
Disney

Google

Sony

Facebook

Amazon

It's finally gone beyond the traditional 2 man startup industry, even if it's still just hope. Also gone are jobs for hobbyists & self taught engineers. Masters degrees are required to have any shot at these places. Whether useful products emerge, at least for now, designing autonomous systems for a living is as typical as designing routers once was. The average engineer of today is judged by how long his quad copter stays aloft as much as someone 30 years ago was judged by how long his router stayed online.