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Archive for March, 2009
Posted by Jack Crossfire | Mar 31, 2009 @ 12:12 PM | 2,775 Views
He rambled a lot about management styles & project planning. That's what software is for nowadays.

The SSME was tested to destruction. That's why it's never failed, so far. No other part of the shuttle was tested to destruction, so the rest of it has had problems as managers speculate on the lethal conditions.

The turbine blades & the bearings crack in every flight & R reused after cracking. They couldn't get them to stop cracking, so instead of fixing the problem, they tested to destruction to know when the cracks were lethal & told the astronauts they were riding cracked blades.

Unfortunately, it's real expensive to test to destruction. U ever blow up a bag of LiPo's to figure out what their true C rating is?

The A1 test stand has no roof. They can't fix an engine if it's raining. The 1 time they put a roof on it, it trapped pure O2 from a leaky valve & made all the wires on the test stand burst into flames when the engine started.

He thinks NASA should have continued improving & testing the shuttle after 2003 as if it wasn't being phased out. Now there R no more improvements, the experts have left the program, & you're flying extension after extension on a vehicle which is no longer tested.

He thinks NASA emphasized pushing the limit of technology too much & should have derated the performance to increase margin. The shuttle was no more dangerous than any other system, if its performance was reduced.

NASA can keep making new vehicles all it wants & they'll be just as dangerous as the shuttle. By pushing the limits of performance & not testing components to destruction, they'll make Ares-1 just as problematic & expensive.
Posted by Jack Crossfire | Mar 30, 2009 @ 01:48 PM | 2,623 Views
Dreamed Russian Heroine became a rich banker & formed her own olympic swimming program. She hired some coaches & athletes. She was much older, sitting in a chair next to the pool, & her athlete lover swam over.

We figured the program was just a way of providing a constant supply of men to make love with. She still recognised us but was much more interested in her athlete.

In another dream, we joined a startup full of Russian programmers & she came in, yelled & screamed about stalking her. It was on some university in a classroom.

Vacuum tubes forever

Hopefully U all saw this Gizmodo revelation about vacuum tubes.

Electrons on Parade pt 1 - RCA (9 min 31 sec)


U can't blog about sonar without bringing up vacuum tubes. The answer is yes, BYU used vacuum tubes in its recording studio in 1997. More specifically, a pair of tube leveling amplifiers. Vacuum tubes still are the only way to get certain sounds just like a Steinway is the only way to get certain sounds.

So U want to simulate vacuum tubes in software, eh.

The truth about digital audio

Sampled audio at 48khz can't reproduce a 440Hz sound. It can alternate between 440.366972Hz & 436.363636Hz to try to fake it, but it can't do the 440Hz your great great grandparents heard on their LP's. To make discretely sampled audio do every frequency that analog did, it would have to sample millions of Hz at 24 bits. It literally amounts to digitizing the molecular structure of the complete physical tape.

Wouldn't be surprised if no-one in the current generation ever heard true A440.


Kinetic energy busters

The kinetic energy credit card had some more problems. It took -2v to rewind the first mass, so the second mass needed 3v. The 3v mass would finish its movement before the -2v mass rewound. Since each mass movement took less time to complete than the previous one, a new mass would be required for every movement. There was no way to defer kinetic energy repayment.
Posted by Jack Crossfire | Mar 29, 2009 @ 05:32 PM | 2,804 Views
3 years ago, U envisioned the kinetic energy credit card. It accelerated payloads to 17,500mph while deferring the equal & opposite reaction for later. At 17,500mph, it released the payload & then repayed the equal & opposite reaction by returning to Earth & discharging the rest of the debt into the ground.

It used 2 moving masses in real long tubes. 1 moving mass shot aft to accelerate the payload forward. When it reached the end, it reversed direction & another moving mass shot aft with enough velocity to pay back the direction reversal of the first mass + additional payload acceleration. They kept alternating & accelerating exponentially to build up payload velocity.

In reality, it would have used millions of oscillating masses, they would have exceeded the speed of light real fast, & the tubes would have been really really long vacuums, maybe several miles long.

It could work with a ground based vehicle. It would allow the vehicle to travel a short distance without requiring traction.
Posted by Jack Crossfire | Mar 29, 2009 @ 05:06 PM | 2,652 Views
There is no direct servo control via IR on the Heroinesapien. The 1 kid who went through all the trouble of uploading a teardown to the internet didn't label the fricking chips.

U would have to splice 3 wires for each servo to control them manually. U would have to bias the potentiometers without turning on the H-bridge driver. All the leg wires R hard soldered to the board, so U couldn't just make a board with connectors & plug it in.

Walking requires changing the center of gravity by moving the arms & body motor, then moving the leg motors....Continue Reading
Posted by Jack Crossfire | Mar 29, 2009 @ 12:18 AM | 2,803 Views


Automatically add someone famous to the subscribers list of every account. You'll have them falling over themselves with glee, taking their comments seriously, & referring your social network to the world. Gizmodo originally did that.

Make a fake IQ test which always gives rediculously high numbers.

Most importantly, use a strange font that no-one's seen in years.

Sonar busters

Phased array sonar is busted. The ping is too repetitive & the waveforms aren't similar enough for absolute differences or correlations of the waveforms to work. Was hoping correlation could get a hedge from multiple distance readings. It would work if the frequency was super low & the microphones real close together.

It detects phase in a single period nicely. That could be applied to velocity or error correction.

All U can get are independant distance readings from the microphones.


Posted by Jack Crossfire | Mar 28, 2009 @ 03:47 AM | 3,656 Views
Fuggedaboutit it using GPS. If sonar panned out & we could get it up to 20Hz, a VikaCopter swarm would definitely happen someday. It would take precise alternating of pings from 2 separate computers. It would use 1 ground station & a lot of new software.

A swarm can do a lot of things a single vehicle can't. 3 GPS guided vehicles can surround a building & provide UWB positioning for a vehicle inside. 1 vehicle can fly a light while the other one flies a camera. They can refuel each other. They can hand off payloads to eliminate refueling. Most of the money these days goes to mapping obstacles using swarms. They can do other things which R too crazy to mention.

Sonar hell

Aligning 3 channel audio is hard. You're better off sending 3 channels + 1 empty channel & eating the clockcycles. Also not sure of exactly the best way to determine the phase of 3 audio channels.

More shuttle 4 U

Loading up your portable media player with

http://ocw.mit.edu/OcwWeb/Aeronautic...otes/index.htm

& listening to it during 10 hours of traffic every week, U realize the purpose of universities isn't what it was 15 years ago. People R learning everything they need from the internet. They're getting brand recognition from universities.

The MIT degree means they physically sat in a room, were lectured to by the best, & waited on a lot of stupid questions. That's the kind of thing big companies value. So MIT doesn't spend money on calculus &...Continue Reading
Posted by Jack Crossfire | Mar 27, 2009 @ 12:09 PM | 3,707 Views
Yes, when the original Robosapien first came out, we too were blown away by the hype & wanted one. This really was the gadget that put Gizmodo on the map. It was invented by a Los Alamos engineer & he had all these videos of spagetti prototypes & the video was freakish & it was only $100, wow!

Would never buy a male robot or a barbie doll, but we always wanted replicas of Heroine Statues & Russian Heroine left us, so it's time for the Heroinesapien.

Heroinesapien 4 U (0 min 50 sec)


Sadly, she can't do much without PC control. The posing feature is really worthless. There's no position accuracy. The waist servo is too highly geared to pose. She forgets all the poses when power cycled. She can't walk on carpet at all. She has husky african voice sounds. She can't be posed like an action figure. The 11 joints are mechanically coupled to just 5 degrees of freedom. She can't bend over.

Some ideas 4 U Heroinesapien hackers:

Give Heroinesapien the learning & intelligence of an AIBO with PC control.

Recharge the batteries with a head mounted solar panel & intelligent sleep modes.
Posted by Jack Crossfire | Mar 26, 2009 @ 12:43 PM | 3,210 Views
http://ocw.mit.edu/OcwWeb/Aeronautic...otes/index.htm

via a comment on $parkfun .

The shuttle runs at 1Hz during liftoff & 6Hz in orbit. Most electronics R manually shut down in orbit to save fuel. The gyros were originally sampled to only 4 bits because they didn't have enough clockcycles. Full scale range was based on liftoff oscillations, not orbit.

The shuttle doesn't use PID loops because there's not enough fuel to constantly hunt for equilibrium. It uses XY plane feedback. Given a start & end state, the computer looks up the exact required burn time in a table.

The pilot has to manually select lookup tables based on payload, robotic arm position, & docking.

The standalone shuttle is a rigid body while a docked space station & extended robot arm turn it into a flexing body.

They calibrate the tables using very accurate mission simulations in software which accurately predict the center of gravity, moments of inertia, flexing modes, aerodynamics, & noise. On STS-1 they had an unpredicted oscillation during tank separation which almost killed the crew.

Also, most of the computers failed on STS-1 because of floating solder balls.

You're never done optimising a system even after U start flying it.

The space shuttle computers have 100x more memory than VicaCopter's airborn computer.

Everyone taking courses in aerospace is an Israeli or a Russian & they constantly ask stupid questions too. Look. The worst part about college was waiting for the endless stupid questions to get answered & they all were stupid.

Hubble is high maintenance because it flies in the "south atlantic anomaly" which exposes it to severe radiation. The Anomaly is caused by the Earth’s magnetic field, but Americans R going to fix it by raising carbon taxes.

Entire careers were built on guidance, navigation & control in the 70's. Today U buy the systems from China for 5 cents.
Posted by Jack Crossfire | Mar 25, 2009 @ 02:59 AM | 2,801 Views
The answer is no. U don't need a 157khz samplerate to capture 40khz sonar. Through the magic of aliasing, U can sample at 50khz. On a 50khz ADC, the 40khz waveform shows up at 10khz. That's good enough for 2" of accuracy. This trick won't work on a soundcard because those have lowpass filters to reject everything above 20khz. Only bare ADC's.

157khz would be better, but we have to pay your mortgages off.

Libusb does indeed support queueing multiple URB's, so U don't need the dual endpoint trick from 7 blogs ago. Getting a 48Mhz PIC to do 3 transducers at 50khz is not easy. Probably not enough room for the radios.

Now page 2.

Most of our memory of Russian Heroine was from just the first 7 months in 2007. Have very sparse memories of her in 2008. Only saw her 4 times in 2009. On the inside, didn't notice the first 7 months receeding into history. They always felt just around the corner, but on the outside the times were getting rarer & we were missing her a lot more.

Having a car & a big salary let her join a lot more activities & keep busy. Before that point, she was pretty idle & unhappy. Those 2 things basically ended the 7 month honeymoon.

The $50,000,000,000,000 man strikes again.

After astronauts installed the final solar arrays on the space station, Osama made up a great line,

"This is really exciting because we're investing back here on the ground (in) a whole array of solar and other renewable energy projects. And so, to find out you're doing this up at the space station is particularly exciting."

Solar panels powering satellites. What a great renewable energy project.
Posted by Jack Crossfire | Mar 24, 2009 @ 01:11 PM | 2,779 Views
So Russian Heroine left us a month ago, 2 weeks before the 2 year point after she arrived. Don't expect to fall in love anymore. Our heroine worshipping trait began at age 10 & never dematerialized. Never was attracted to winning the bread & thus never had a successful love affair, never dated, & never got emotional support before Russian Heroine.

Thought we'd naturally adjust to patriarchy by age 25 but it never happened. Used to think it was fatal, but times have changed. Nature weeds out all non hackers. If it wasn't possible for humans to survive without emotional support, heroine worshippers wouldn't be born.

The DNA sequence would have been thrown out by a repair protien. Neurons would have evolved to not make the connections. Evolution would have weeded out our capacity to worship heroines if it was really fatal. Heroine worshipping can never perpetuate itself, yet humans can still do it, so it's probably survivable.

Humans forget bad experiences & remember good experiences. Humans follow leaders blindly & enslave themselves. The traits that perpetuated the species survived. If evolution didn't shut down certain brain functions, U humans would tend to absorb all the pain in the world & die. The "feeling all the pain in the world" function got thrown out.

The answer is no. The USB prototype can't get the 471000 samples/sec required by software sonar. It was intended for audible sonar instead of ultrasonic.

The cheapest solution is the PIC24FJ64GB106 or an AT91SAM7S with the whole autopilot on the microprocessor. It's a question of throwing huge amounts of money into a potential disaster or throwing huge amounts of time into proving theories with uneconomical parts.

We prefer using the same parts for everything & most theories blow up, so guess where this is going.
Posted by Jack Crossfire | Mar 23, 2009 @ 12:32 PM | 2,674 Views
Firstly, flying the IDG300's is real hard. They drift too much for any lapse of concentration. Secondly, the software sonar was much better in flight than the Maxbotix reference design. Got 20ft of horizontal range at eye level. They can go up to 30ft at higher altitudes. This is more than the indoor space in the dumpy apartment.

Though the margin can be increased by aiming the receiver at the flight area, we aimed it straight up & the transmitter straight down.

Also, FYI the 3.3Ah super battery went 10min with Ghetto copter.

Finally, the hand soldered uBlox 4 recorded horizontal position in flight but not vertical, so we can't tell if some of the Maxbotix range was vertical or horizontal. It got 5-8 satellites.

With the soldering producing much better results than the breadboard, there R still a few more amplifier tweeks & an increase in the bandwidth before we light up the 2 extra transducers.
Posted by Jack Crossfire | Mar 23, 2009 @ 12:26 AM | 2,600 Views
Make a note of this so U don't forget about it while worshipping your mortgage bailouts.

Ares 1-X has been cancelled. It has a tentative date of July 31 in the unlikely event your government doesn't have to pay out more executive bonuses, but nothing is planned.

nasaspaceflight wrote:
> Orion 4 and the first crew rotation mission to the International
> Space Station (ISS) - is threatening to slip on upcoming PMRs
> (Program Milestone Reviews), with a worst case scenario of 2017.

We originally predicted 2020. Well, given the size of Ken Lewis's bonus requirements, fuggedaboutit. Really Edward Liddy's bonus was the curve ball that downed this turkey.

http://www.nasaspaceflight.com/2009/...al-pad-option/
Posted by Jack Crossfire | Mar 22, 2009 @ 06:49 PM | 2,575 Views
The answer is yes. A USB PIC sampling at 157khz can record a Maxbotix. The factory frequency came in around 38khz.

55khz turned out hopeless. The champion was 40khz. The PIC starts falling over above 40khz, so 55khz time constants really produce 40khz.

The Maxbotixes worked best with shrouds removed, a delay loop of 2 samples, inversion, & fuzzy logic. Higher sample rates R better. All the noise comes from the microphone. Software made it much more omnidirectional but nothing has matched audible sonar with the $200 PC soundcard.

Correlation didn't work with the Maxbotix. One idea is its bandwidth is too narrow, so U get noise of the same frequency correlating with the pings. Another idea is the PIC time constants not working.

AGC for op-amps is dead. The best AGC is the maximum receiver gain while adjusting the transmitter power.
Posted by Jack Crossfire | Mar 20, 2009 @ 09:02 PM | 2,734 Views
The Goo Tube had another nugget 4 U. The latest in indoor position sensing is UWB positioning. UWB position sensors work exactly like VicaCopter's sonar concept, except these pseudo random pulses go from 3-12Ghz & repeat at 10Mhz. They use UWB because it's immune to reflections.

UWB position sensors R already sold commercially. Just take out your home equity line of credit & go to

http://www.timedomain.com/

Now have an indoor copter using UWB position sensing.

JJ Autonomous Flight (1 min 58 sec)


With UWB positioning, the spider drones in Minority Report should be no problem.
Posted by Jack Crossfire | Mar 20, 2009 @ 02:37 PM | 2,485 Views
Look kids, let's get 1 thing perfectly clear. UAV hobbyists posting discoveries on RC Groups don't aid the enemy. If they ever had the brain power to produce military results, they would already be in the business instead of doing it as a hobby. If they R doing the military level as a hobby while the enemy is using it for defense, then the enemy deserves to win.

Who wants to live in a world where the state of the art is RCGroups while the trash is Boeing? That would be a system which punishes the best & rewards the worst. By all means, let the enemy win & give US a system which rewards the best instead of suppressing them.

Fortunately, we've never seen anything on RCGroups anywhere near what could aid the armies of the world. Take a look at the AIAA journals & you'll be satisfied the system is still rewarding the best. The armies of the world R all above that & that's just what the Google corporation allows you to see. Google filters out all the crazy research. All those results in turn R above the RCGroups hobbyists.
Posted by Jack Crossfire | Mar 20, 2009 @ 12:55 PM | 2,993 Views
So the optocouplers R the best solution for the given budget. PWM adds a lot of noise. The gain is half wave only. That may be a DC offset problem. It takes a lot of CPU time to correlate 157khz audio. The packets get out of order when using 2 endpoints. Most of all, the gain oscillates.

Someday there is going to be a 157khz sampling test with the Maxbotix's to see if software can get any omnidirection out of them. That sonar system would require 2 discrete A/D converters but would be silent & deadly accurate. They're so directional, we expect nothing except reflections.
Posted by Jack Crossfire | Mar 19, 2009 @ 02:00 PM | 3,071 Views
So U want more bandwidth but U don't have enough memory for ping pong buffers. U need smaller audio buffers but Linux has too much latency. U want to send different streams of data without having to multiplex packets by hand. U need USB endpoints.

The pros don't call blocking read calls on a file handle like U do with UARTs. For USB they allocate many file handles & request simultaneous I/O on all of them in the background. That way the device always has virtual buffers to fill & doesn't overflow waiting for Linux. Also, each endpoint can be a different stream, so U don't need to multiplex anything by hand. It's a great way to stream telemetry.

With that out of the way, VicaCopter shows up like this in /proc/bus/usb/devices.

T: Bus=02 Lev=02 Prnt=20 Port=01 Cnt=02 Dev#= 34 Spd=12 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
P: Vendor=04d8 ProdID=000b Rev= 0.01
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
I: If#= 0 Alt= 0 #EPs= 8 Cls=00(>ifc ) Sub=00 Prot=00 Driver=(none)
E: Ad=01(O) Atr=02(Bulk) MxPS= 32 Ivl=0ms
E: Ad=81(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=02(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=82(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=03(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=83(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=04(O) Atr=02(Bulk) MxPS= 32 Ivl=0ms
E: Ad=84(I) Atr=02(Bulk) MxPS= 32 Ivl=0ms

That's a lot of endpoints. There's 2 for sonar, 1 for the Xbee, 1 for 72Mhz, 1 for commands,...Continue Reading
Posted by Jack Crossfire | Mar 18, 2009 @ 12:55 PM | 2,578 Views
Got the PIC up to 157khz. That's high enough to record raw Maxbotix transducers. The mane limitation is it only has 384 bytes of memory. U need to service USB requests in 1/400s or the buffer overruns. It definitely overruns depending on the Linux load.

Unfortunately, when multiplexed for 3 microphones, it comes down to 52khz. Next, 8 bit audio is pretty worthless without AGC. U can make a voltage controlled variable resistor out of a pair of optoisolators. It's the simplest voltage controlled gain possible. Just 6 optoisolators required.

Now that the Goog was online for a few minutes, U get the sound recording.

Home made soundcard (0 min 33 sec)

Posted by Jack Crossfire | Mar 17, 2009 @ 02:16 PM | 3,130 Views
Luckily 4 U, the Linux kernel can be a software bus analyzer. Go into linux/drivers/usb & use printk's to dump the buffer contents. U need to stop searching the Goog for bus analysers.

5 days of insanely difficult assembly language debugging & the home made soundcard finally started working. The USB driver ended up being under 1000 bytes, quite a bit less than the host we did before. There R no interrupts for USB. U have to use polling, which slows it down.

It can do 150khz before running out of clockcycles. That's 1.2 megabits coming out of a PIC. It can only do 23khz before the sound quality starts deteriorating. U need 150khz for sonar. The Goog is offline, so all U get is a picture of the waveform.

GPS aided heading only works in hovers. It falls over in horizontal movement. Going to acceleration doesn't work. That leaves washing out velocity or forgetting about it when translating.

Must remember to try adapting the sonar ping rate based on velocity. Maybe 1Hz when moving slowly & 10Hz when moving fast. It could either make it more bearable or make it sound radioactive.