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Posted by Jack Crossfire | Apr 16, 2009 @ 12:33 PM | 4,271 Views
Reynolds numbers 4 U

Not that anyone outside N. Korea ever listened to them, but we found the 2 aerodynamics lectures pretty useless. Don't think either the students or the speakers had a clue what the speakers were saying. Sounded like the shuttle didn't have any unique aerodynamic problems.

More sound resonance

Seeing huge drops with the tiniest smidgen of offset from 38khz. Such a sharp bandpass response is a crummy situation in the omnidirectional world.

Fortunately, your mortgage bailouts left us enough money for some Matsushitas. The Matsushitas R enormous 1"x1/3" devices & resonate at 24khz, so definitely more hope for range with the large airframe.

The amplifier degrades the radiated power from a Maxbotix.

The western bloc

In the western bloc, April 15 separates the men from the heroines. After inflation & tax increases, we now have less income than we did after finishing college but our boss made enough home equity since Tuesday to build an island.

The Goog loves to say "but outsourcing is lowering prices" & follow it with a mortgage advertisement, but if the price of labor in China rises 50%, is that deflation?
Posted by Jack Crossfire | Apr 15, 2009 @ 02:07 AM | 2,913 Views
Water rationing ended, so the golf course is back to full soaking during flying time. Fortunately, we know the soaking times better without water rationing. Water prices R going up yet again this month, to fund the wine baths at Goldman Sachs.

YOUR GOVERNMENT

One other thing. The shuttle boosters have thrust vector control because of the slight chance the boosters won't burn out simultaneously. It probably could have flown every mission with main engine gimballing alone & saved 12 tons. The same 6 ton, leaky, flammable, hydrazine actuators from the shuttle R going into Orion.

If the diameter of the SRB's was determined by the width of railroad tracks, which was determined by the ruts from Roman chariots, which was determined by the width of 2 horse's asses, how did your government figure out the price of a house should be $1 million?

In other news, NASA reversed the idiotic votes of the public school kids of the 80's & named Node 3 "Tranquility" instead of Colbert. Calif* supreme court immediately overruled NASA's overruling, stating the LDS church unfairly manipulated NASA's minds & the module should really be named "Proposition 8".

PINGING U

The ping frequency resonates at 38khz instead of 40khz when sampled at 264khz. When sampled at lower rates, it resonated at 40khz. Since 264khz is the raw air pressure, U can assume the transducer resonates at 38khz & 40khz was the matched alias.
Posted by Jack Crossfire | Apr 14, 2009 @ 12:59 PM | 2,752 Views
Clearly from range testing different sample rates, we have good & bad samplerates but no dependance on higher bandwidth. Seems to be the resonant frequencies. Down to a few more commutes of different samplerates.

Next, your beloved 96Khz 24bit soundcard/oscilloscope died. Seems to be bad connections in the PCI slot & no-one makes 3.3V PCI slots for it anymore. Never used it for 6 channel sound after the first month. Never had time between commutes to do the connections & U can't hear anything in a dumpy $500 million apartment anyways.

Indeed, the last audio we did was in a time of 25 minute commutes. Then all U midwesters flooded in after your jobs got outsourced & the commutes went up to hours.

That got us thinking, U could probably make a really good 1Mhz 24 bit USB soundcard. If U wanted to make money on it, U could make it use VACUUM TUBES.

Indeed, people make USB vacuum tube sound cards all the time to convert between the DAC & the line level, but 1Mhz 24 bit is too crazy for the Goog.
Posted by Jack Crossfire | Apr 13, 2009 @ 05:49 PM | 3,198 Views
Hydrolics leak & are unreliable. Hydrolic fluid burns. Hydrolics require a turbine spinning at 82000 RPM & burning hydrazine monopropellant to compress a highly flammable fluid in a piston.

The shuttle used them because they had too many hydrolics experts on the payroll to switch to electric & electric actuators were unproven. Any cheap brushless motor from Align is more reliable than the hydrolic actuators on the shuttle, but like we said, it wasn't supposed to fly after 2010, before the extension.

They faced the same problem as any UAV hobbyist going for FAA approval. Mainly, how to get redundancy in case an actuator fails. Tandem pushrods didn't work because the broken one would act like a sponge. So the only redundancy is the 3 APU's.

That's like having a spare battery to power servos & why we minimized servos to just 1 of the most reliable ever made, the mighty Futaba S3102.

The APUs R the hydrolic compressors that were originally used on airplanes to control the pushrods in case of engine failure. They are not auxillary on the shuttle & a war was fought & lost to rename them.

They originally blew up like main engines because their airplane derived valves got too hot in a vacuum & ignited their hydrazine fuel. Their airplane derived sump pumps & oil pans didn't work in 0g. They rely on very tight tolerances between the gearing & the enclosure to scavenge oil.

test pilot notes

So the space shuttle has no redundant cooling system. It has 2 cooling systems & both R required to keep it from melting down. In space, it radiates heat from the payload bay doors. During takeoff & landing it boils off water. Sounds a lot like Hillary Clinton.

They used simulations for orbiter mode but had a test stand just like U for airplane mode. The shuttle was mounted on airbags that simulated the angular movements just like your apartment test stand. They spent a long time tuning feedback constants even after orbital flights started.
Posted by Jack Crossfire | Apr 13, 2009 @ 04:12 AM | 2,942 Views
Seems U need a lot more than 16 MIPS to get 450khz sampling so those $5 parts wouldn't fly. Fortunately, got it up to 260khz with a lot of assembly language tricks. Basically, accounting for every single clockcycle, unrolling the main loop, stripping the USB stack to the minimum, polling instead of interrupts, replacing subroutines with a big loop. The USB stack is down to 850 bytes.

Got analog crosstalk at 260khz, so it ended up taking nops to slow it down to 200khz. Some say it's worth building 2 USB devices at 260khz to see if sonar is feasable at all.

So with the nyquist now 50khz, the Maxbotix EZ-1 replaced with a bare transducer, only 2 dimensions being measured, the result was yet another incremental improvement but still worthless.

The next step would be repeating basic range tests at different sample rates.

Can't get good results unless your nyquist is several multiples of the ping frequency & we're only at a 50khz nyquist. Like a 44100 CD trying to generate a 14khz tone, sometimes the samples line up, sometimes they beat, & the beats make it sound grainy.
Posted by Jack Crossfire | Apr 11, 2009 @ 08:28 PM | 2,788 Views
Another set of batteries & sonar is definitely busted. Even with all the progress in omnidirectional sensing without propellers, with propellers & a large array, range was still a narrow cone directly above the array. The large airframe & the lack of accelerometers & magnetometers made positioning too sloppy to stay in the small cone. Altitude was nowhere close.

What happened with the array if single sensors had great range? Suspect the spacing in the array made every sensor have to look farther sideways. Another possibility is peripherals in the recycled Maxbotix EZ-1 interfering with the tone generation. Finally, there's the 30khz sampling creating aliases of propeller noise & destructive interference between aliases that wasn't there in 150khz sampling. A tone at 40 & 20 that didn't self destruct at 150khz would interfere at 30khz.

The best results were a pair of 13 second hovers directly over the array. Used really high gains & no altitude feedback. Almost had to flip it over to get feedback tight enough.

Your best chance with sonar is the smallest airframe possible or a blimp. Maybe an E-sky with SMT board. It would be a great replacement for an Evolution Robotics sensor if it was a ground vehicle or a blimp.

More likely you'll get another electronics upgrade. Sonar is that important 4 U.
Posted by Jack Crossfire | Apr 11, 2009 @ 12:58 AM | 3,016 Views
ADC SECRETS

It takes a lot of current to feed an ADC because they need to recharge a sample hold capacitor. This makes direct IMU or thermopile connections noisy & op-amps a good idea. Vref's for ADC's need a lot of current too, so you're better off stockpiling quad op-amps. No surprise that the cheap, crummy, obsolete Picopilot has an op-amp buffering the ADC inputs but we don't because we're too poor.

FILTERING SECRETS

Also, for any conversion from an analog value to a geometric solution, we found it better to smooth the raw analog values than the geometric solution.

SONAR FLIGHT 1

What a freakshow that was. Another subfreezing La Ninia April. The first dead laptop battery in flight. Uncalibrated feedback gains. Massively underestimated propeller noise in the derivative. Only a tiny box in which sonar position was valid. Not enough control to stay in the tiny box.

50% bandwidth is required on position & 25% bandwidth is required on velocity.
Posted by Jack Crossfire | Apr 10, 2009 @ 12:52 AM | 2,804 Views
1) U can make more thrust by crumpling dollar bills & throwing them from the back of a spaceship than U can by burning them in a combustion chamber.

2) Unless U plan on flying them into orbit for less than the cost of throwing away crumbled dollar bills, they're a lot of work with no gain 4 U.

3) We glaze over when hearing mixture ratio, molar mass, fractional dilution, distillation ratio, & freezing point depression.

But, Henry Pohl's lecture had a lot more basic engine theory than J. R. Thompson because he was an engineer while J. R. Thompson was a manager.

Did U know the OMS fuel injector was made by UV lithography? They burned photo resist patterns onto extremely thin sheets of metal to etch away thousands of holes. Then they stacked thousands of those sheets to create a 3D manifold. Drill bits weren't accurate enough.

The minimum pulse of the vacuum started engines was 60ms because residual fluid would evaporate & freeze after firing in a vacuum. Eventually the freezing would overcome the amount of heating required to ignite the fuel & the engine would be dead. So they needed 60ms of firing to reverse the amount of freezing in shutdown.

The OMS engines need 20s of firing to reach optimum efficiency. They can't be used for shorter burns because they would waste too much fuel. Also, the 0.61m/s/s created by the OMS engines prevents anyone from sleeping or using the toilet.

The RCS engines R film cooled. They inject a lot of...Continue Reading
Posted by Jack Crossfire | Apr 09, 2009 @ 02:39 AM | 3,082 Views
We've gotten so much mileage out of empty plastic bottles, Calif* is probably going to outlaw recycling to keep the landfill union in business.

Definitely more accurate at 10Hz because we have fewer echos, but also a lower threshold is calculated because there R fewer echos. A bit more accurate if U play with the threshold calculation. Suspect an adaptive threshold based on position noise would be beneficial. Maybe a neural network.

Got it to where it would fly if the propellers were totally silent & it didn't bank too much, but we know the propellers make a lot of noise & change the threshold.
Posted by Jack Crossfire | Apr 08, 2009 @ 01:33 PM | 2,603 Views
U once had a boss who spent forever & everyone else's time building a corny rack & pinion machine to show how a touch pad could be used to control camera zoom & how the touch pad could be used in 3 different zoom modes. Touch pad position either controlled absolute zoom, relative zoom, or constant zoom rate.

Guess in his mind, showing the mechanical mechanism of a lens somehow conveyed these zooming modes & this would somehow make Japanese investors invest in a touch pad instead of a rocker switch. This was long before the iPhone, when no-one ever heard of such a concept.

No-one ever suggested he just write a simple piece of software to actually magnify a photo because they'd get fired for making him look like an idiot & also because of the top rules of the white collar world:

#1 Don't suggest anything that makes the boss's idea look completely idiodic.

#2 If U suggest it, it'll get thrown out because the boss didn't think of it. If U don't suggest it & the boss thinks of it, it'll get accepted. So the best way to get something accepted is to not suggest it & wait for the boss to think of it.

We were actually in the room when the VP proudly explained how the clunky rack & pinion demo would bring touch pad zoom to the cameras of the world, wondering why the fools didn't magnify a photo in software.

Well not only a huge waste of everyone's time, but the Japanese eventually canceled that project. Fortunately for the world, a manager at Apple did magnify a photo instead of build a rack & pinion machine.
Posted by Jack Crossfire | Apr 08, 2009 @ 12:17 PM | 2,645 Views
Clock synchronization with USB is a real buster. There's a lot more jitter than RS232. Some say it's the audio capture load. Some say it's bugs. Fortunately, no danger of the dry weather for 2 weeks.

To get clock drift, U need long histories of clock readings from the 2 computers to take the readings which R most similar, but the longer the history, the slower the drift update. U need to replace the history as fast as possible to get good gaussian drift results.

Also tried waveform derivatives & there was a small improvement at longer distances.

Angling the sonar array 45' didn't work. Too many reflections from the floor.

Everything's moving towards 1 flight with the array, then a move towards reflected sonar altitude & a dipole. It's a 4 wire connection to an op-amp board, assembly language implementation of the DSP, reconfiguration for higher samplerates, UART interface to the sonar board.

Of mane concern is transporting the sonar array, so we'll probably use a bigger array on pods & dump the aluminum.

Component testing has gotten really anal with the last few airframes. It takes too long to set up, we don't officially have any time off anymore, & you're now experts on what is required to fly, so the systems have to work the first time & U don't need as much flight time as U used to.
Posted by Jack Crossfire | Apr 07, 2009 @ 02:31 AM | 3,329 Views
So how do U plug sonar positioning into a GPS autopilot? Convert the sonar results to fake latitude & longitude of course. & for all U GOOG shareholders, add offsets so they can be plotted in Goog Earth.

Unfortunately, 20Hz is real problematic. The indoor reflections bleed into the next frame. Fortunately, got the CPU usage back to 1%. The ping rate isn't exactly what's configured, so U get 25Hz & multiple pings in the same frame. Measurements are starting at random offsets.

Also, try derivatives instead of peak levels.

OOBS MEETS THE PENTAGON

Now as much of the Obooobu stamp of defense cuts as U can make out from the AP coverage:

F-22: GONE
Italian Marine 1: GONE
Missile Defense: GONE
Airborne laser: GONE
Predator & Reaper: increased by $2 billion
F-35: 16 more planes
Mortgage bailouts: 80,000,000 more mcmansions

Fortunately, there R plenty of jobs 4 U unemployed laser gun experts in N. Korea. FYI, we own a small number of United Technologies shares, so buy buy buy.
Posted by Jack Crossfire | Apr 06, 2009 @ 12:00 PM | 3,217 Views
Finally got a 3D position out of sonar. All those small errors really add up. It's 1ft off in the air. On the ground, it's hopeless. It is 20Hz at least, it's better than GPS, & it's indoors. It would definitely improve with a larger array & 5x faster sampling. What do U expect for $20?

So it's taking 42% of an 800Mhz CPU to do sonar navigation. Sometimes clock drift works & sometimes it doesn't. The triangulation algorithm is the least efficient possible. If the copter clock is ahead of the ground clock, fuggedaboutit. As Kris Kraft would say, U need to start flying it regardless of the imperfections, to know if sonar is completely nuts.

There was once a large book of software anomalies for the space shuttle. The risk & cost of software changes was too high to bother fixing it.

So, in a 10 minute flight, Vika 2 needs to process 55 megabytes of telemetry to stay in the air. In comparison, your GPS vehicle with 14 satellites crunches 1 gigabyte in a 10 minute flight.
Posted by Jack Crossfire | Apr 05, 2009 @ 08:27 PM | 2,930 Views
HEROINESAPIEN

Can't believe Heroinesapien fizzled out right after release the way she did. U people forgot about her within a month of 2008 CES. At least we know she could walk on carpet if properly hacked.

Heroinesapien walking on carpet (2 min 15 sec)


Another note on Heroinesapien: The servos are timed so if they don't reach their desired position in a certain time, they just stop. A little smarter than RC servos which just burn out.


THE LATENCY OF GROUND BASED AUTOPILOT IS

Got the latency figure for ground based autopilot & it's 60ms. It takes 60ms to transmit an event from the copter, to the ground station, & get the response back. So really the feedback is 16Hz & the other 34Hz R redundancy for interference. Got that by comparing transmitted packet numbers with returned packet numbers.

SONAR 4 U

Also, with the increased workload on the groundstation, we're now aligning the sonar clocks to within 21 useconds or 0.27" of distace error. Pretty horrible.

Remember using the Maxbotix to sense altitude? It was killed because the Maxbotix didn't have an accurate enough trigger, was too expensive, the shrouds defeated XY sensing, & U thought U could synthesize pings on the flight computer to save a few milligrams.

Well, the answer is no. Your flight computer doesn't have enough clockcycles to synthesize pings. It can only reach 8khz. It turns out, when 8khz pulses are applied to the transducer leads, current...Continue Reading
Posted by Jack Crossfire | Apr 04, 2009 @ 10:04 PM | 2,895 Views
At least all those laid off Boeing employees have jobs in N. Korea.

Now the headline on CNN:
> The NCAA men's basketball Final Four couldn't come at a better
> time for the city of Detroit.

With a budget of $654.1 billion, your defense department is going to pay most of the cost of new mortgage, SUV programs & that oh so precious NCAA men's basketball final. The prime cuts will be:

airborne laser: gone
Air Force refueling tanker: gone

Our gut reaction is most of the 1 man UAV startups will be gone & the budget is going to focus on increasing the number of tried & true predators & global hawks to replace manned planes. Hummingbird A160, MQ-8B firescout, X-45 UCAV, X-51 waverider: fuggedaboutit.
Posted by Jack Crossfire | Apr 04, 2009 @ 06:06 PM | 2,852 Views
The only thing we need from Canadia is Motor-7mm 1.7Ohm. Can't believe no-one besides Canadia sells a stupid motor. If there was any other place to get it from, or humans were more creative, this story would already be over.

Kris Kraft notes

Kris Kraft thinks like most of the world exept US. Mainly, the rest of the world thinks about doing while US thinks about politics. He wished China landed on the moon tomorrow because it would make U think about something besides Michelle Obama's dress.

He didn't say anything U don't already know from watching the many TV reruns of Apollo footage. He thinks the space shuttle could be economically viable if it wasn't for politics, job losses, constituents, lobbyists, unions, & basically the USA. The shuttle program was required to buy components from every state. Sheesh.

The only reason the shuttle happened was because it was the only reason the Soviets were willing to negotiate in 1 meeting in 1979. It was really Peanut Head's call, but don't bother searching for Jimmy Carter names on the Goog.

Thinks the shuttle should fly with less of the redundant systems functioning, because that's what redundant systems R for. The main engines could be run at lower power, the TPS could be more robust, & the hydrolics could be made electronic. It could have 100 redundant computers with today's technology. Mainly, it should continue evolving like the 60 year old B-52.

Thinks a lunar vehicle should go between low Earth orbit & the moon, & rely on the shuttle to move people between orbit & the ground. The space station should be moved to a 28' inclination with many incremental propellant burns & become the docking station for the lunar vehicle.

Like J. R. Thompson, said the Orion would be just as problematic & expensive as the shuttle, with a fraction of the capability, because it's the management, not the vehicle. But doesn't think Orion is ever going to happen because of the cost of mortgage programs.
Posted by Jack Crossfire | Apr 03, 2009 @ 03:59 AM | 3,020 Views
Vika 3

Deriving position from realtime digital audio processing is really hard, so lets start thinking about actuators & motor mounts for Vika 3.

Building a micro copter out of Canadia parts would cost over $100, so you're going to be building parts from scratch. Canadia charges $15 for a crummy coil of wire. People R mounting the motors with rubber bands on sticks. Aft thrust vectoring is the hard part.

Ground based autopilot then

Originally, no-one knew if ground based autopilot would work. The latency, full duplex bitrate, & interference effects were unknown. Today we know the maximum feedback rate is 55Hz, & there is enough bandwidth. The latency is 1 calculation U need a day off from your boss to do.

https://www.rcgroups.com/forums/showthread.php?t=912482

Ground based autopilot now

When the timing software was added, it brought the maximum sampling rate from 47khz to 40khz per channel. Since no alias frequencies show up at 40khz, U need to run it at 30khz per channel. Now the ground station is only 739kbit. Really U expected it to go to 30khz anyways.
Posted by Jack Crossfire | Apr 02, 2009 @ 01:04 PM | 6,330 Views
He sounds skinnier & more serious than he looks. Says "umm kay" a lot & is very beaurocratic. Probably doesn't trust anything that bleeds for 5 days & doesn't die.

Clean pads don't save money. The time required to move a rocket back to the hanger & fix it costs more than fixing it on the pad. U need to do as much on the pad as possible.

U need the largest mission control possible. U need as many people on the ground as possible to do what doesn't have to be done in space. This may be more important for manned missions.

The space shuttle IMU has to be reset from the ground once a day. It doesn't have star trackers, accelerometers, or magnetometers. If the update has an error, as happened many times, it'll burn up all its fuel & lose radio contact. IMU's have been replaced by GPS everywhere except the shuttle because it wasn't supposed to fly after 2010.

U need a functioning IMU to align the antennas & U need aligned antennas to keep the IMU functioning. The shuttle can't land without ground communication either. Ground communication is a huge failure point.

Now our highlights video of STS-119, since all the other copies of these highlights were blurry, improperly exposed, jerky & unedited.

best of STS 119 (2 min 25 sec)


The modern consumer electronics industry is basically a space program. The gadgets U read about in the news aren't made by single companies anymore. They're just too complicated,...Continue Reading
Posted by Jack Crossfire | Apr 01, 2009 @ 03:29 AM | 2,837 Views
So U want to easily swap between USB & UARTs for easy conversion between a ground based autopilot & an embedded autopilot eh. Well, fuggedaboutit. All the FIFOs, single byte reads, blocking, timed waits, & polling that UARTs did 4 U have to be written manually for USB.

At least U finally got the XBee, 72Mhz, & audio all crammed into a single cable. Try doing 1.1Mbits over an Ardu nacho taco dilla. Feedback frequency is also a bit more stable over USB instead of serial dongles.

To make it fit in the available clockcycles, U ended up with 6 endpoints, with all the IO except the audio directly between the peripherals & the endpoint DMA area. There's no way to do the audio without memcopies.

E: Ad=01(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=81(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms (audio)
E: Ad=02(O) Atr=02(Bulk) MxPS= 32 Ivl=0ms (to xbee)
E: Ad=82(I) Atr=02(Bulk) MxPS= 32 Ivl=0ms (from xbee)
E: Ad=03(O) Atr=02(Bulk) MxPS= 16 Ivl=0ms
E: Ad=83(I) Atr=02(Bulk) MxPS= 16 Ivl=0ms (from 72Mhz)

To Xbee had to be big enough for a complete uplink packet, to keep the XBee from splitting it into 2 802.15.4 frames & destroying the full duplex rate. U could have done all this on the latest $1 ARM chip without any optimizations at all of course.

Unfortunately, not enough clockcycles to do 50khz audio & radio on the same chip. It's stuck at 47khz. Theoretically, sonar is optimum at 50 & 30 because these are 10khz away from...Continue Reading
Posted by Jack Crossfire | Mar 31, 2009 @ 12:12 PM | 3,569 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.