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Archive for September, 2016
Posted by Jack Crossfire | Sep 27, 2016 @ 09:29 PM | 10,473 Views
Must concede, the 1st time the BFR appeared on the monitor was a bit of a letdown. It seemed too unreal to ever achieve. It went against everything in the Andy Weir book. The size was completely nonsensical. Just when the ship was supposed to stop at an orbiting outpost, the ship kept going, all the way from the launch pad to Mars. Was this nonsense what Musk worked on for the last 2 years?


The internet expected something more realistic, a 3 cored rocket of incrementally more power than the Saturn V, but not 4x more powerful. Things went downhill when the 42 engines all randomly stuffed under the booster appeared. It looked more like throwing the kitchen sink at a problem than rational calculations.


Then Iron Man showed up with a moustache resembling Howard Hughes. He assuaged some fears by stating the video was based on CAD models & there was enough room for BFR facilities to coexist with the current Falcon 9 facilities on LC-39. He already built a full size oxygen tank for the 2nd stage, in addition to firing an engine which seemed to be the full size engine. We all hope today's speech goes down as a Kennedy moment, where we all remember where we were when it happened & quote the lines for all eternity.


The spartan black & white graphics brought back memories of the Saturn V diagrams from the good old days. That made it look a little more legit. Nothing that detailed was released for the Falcon 9. Delta IV & Atlas V diagrams were always...Continue Reading
Posted by Jack Crossfire | Sep 26, 2016 @ 10:38 PM | 9,146 Views
Predictions for Musk night 2016: The BFR will be a single core equivalent of the Falcon heavy, with 9 Raptors. It'll be the same size as New Bezos, but have a reusable 2nd stage. It'll have a 3 core version outputting 15 million lbs of thrust. The raptor engine will produce 600,000lbs of thrust in the same size as the Merlin & a fraction of the size of the RS-25 which made 400,000lbs of thrust.


It'll put an object 75% as large as the shuttle in LEO. It'll use multiple launches for the MCT, fuel, & the permanently space based component.


The rest of the architecture will be equivalent to Andy Weir's vision. The mane focus will be the unveiling of the big rocket, since Andy Weir's vision is familiar to everyone.


It's the largest methane engine ever tested. That alone should have made more headlines than year 50 of race riots. As usual, the engine was heavily obscured in the test photos. It looked much smaller than past 600,000lb thrust engines, but Musk has a history of getting more thrust from the least weight than anyone else.


There's no obvious gas generator exhaust like there was on the Merlin, confirming it's the staged combustion cycle promised earlier.


Musk said it's the same size as the Merlin, but making 3x more thrust from a tripled chamber pressure. Based on photos of the Merlin next to construction workers, the engine under test is indeed the full size version. They're both slightly smaller in diameter than a handrail. The nozzle diameter...Continue Reading
Posted by Jack Crossfire | Sep 24, 2016 @ 11:47 PM | 6,952 Views
The guy who made a timelapse movie of traffic by writing a javascript program to load the data from the Goog developer API makes you wonder why he didn't just screen capture a browser window all day.


It brought to mind the 1+1 problem. The way modern developers add 1+1 is by creating several objects. There's a starting event broadcasted by the user. It causes a 1 object to broadcast an event. A + object waits for the 1 event. Then another 1 object broadcasts an event. The + object waits for that event. When the + object gets 2 1 events, it adds them & broadcasts an = event. There's an = object which waits for = events before broadcasting a display answer event. All the objects reside in their own threads.


Adding 1 + 1 can be done in a single line of code, but it's 1 of many more realistic examples in the mobile app boom where what could be done in a few lines of C code is done using thousands of objects & horrendously complex event passing sequences. Deciphering the simplest workflow requires much worshiping of the IDE's search tools & swapping between many files.


But a single line adding 1+1 is not a dogmatic solution & won't get you a job. The availability of plenty of money to enforce any software architecture dogma, no matter how inefficient, is a key facet of the mobile app boom. Many an interview has been failed by giving direct answers instead of dogmatic answers or worse, looking up the answer like you would do in the actual job instead of trying to recite it from memory like you're supposed to do in an interview.


It seemed to start in the 1990's with the idea of plugins & interprocess communication. The modules became smaller & more fundamental until every single thing is now done by a new object. Many a developer is shocked by the idea that a program can actually be written from left to right, top to bottom, stepped through like a book. The current generation never saw anything like that.
Posted by Jack Crossfire | Sep 23, 2016 @ 11:47 PM | 6,244 Views
For the impatient: “a breach in the helium system”


The helium spheres plagued them for a long time, starting with a “bad trends” tweet in 2015. Surprised the failure caused that much fire instead of just spraying liquid oxygen all over the place like the 2015 explosion. Carbon tanks never did the job on the x-33 & ended up killing the program. If carbon fiber can’t do the job again & they switch to solid metal tanks, it would be another blow to reusability.



As usual, millenials will be satisfied just knowing it was ruptured tank & it was fixed by whacking on a little more fabric & she'll be right. Generation X will never be satisfied & assume the tank was ruptured by an external force not to be disclosed until Nov 9.


The internet converged on spontaneous combustion of carbon fiber as it rapidly unraveled in a liquid oxygen environment. It would be a nifty experiment to deliberately rupture a COPV in a tank of liquid oxygen to see if it explodes, but it would be real expensive so it won't be done.

NASA tested COPVs to 7500psi, back when it made spaceships. The SpaceX ones were 5500psi.



Based on the graph, all tanks fail after a certain amount of time under pressure. Decrease the pressure or the time & the failure rate becomes a function of the number of tanks. In 100 launches, there would always be a failure.



When the tanks burst, it looks like a lion mane got abused.
Posted by Jack Crossfire | Sep 18, 2016 @ 04:32 PM | 3,552 Views
The ganged batteries made their debut 18.6 mile drive. Speed was reduced to 9:30 on account of the heat, which translated to 10:00 after PWM errors. The fuse didn't heat up. After the drive, both batteries were cold.

It was quite luxurious to not have to stop the run, squat, & change batteries. You have no idea what a pain that was for 1st 3 years of robotic exercise coaching.

Battery #2 in the low tray took 4545mAh. Battery #1 in the payload bay took 3294mAh. So they discharged as expected, but it was a quite high current draw. They carried water for 7.5 miles with 5 miles uphill. Need to swap battery trays to see if it was cable loss or internal resistance.


The wiring was redone to handle more current & gain a fuse. The fuse in the apartment was a polyfuse which started blowing at 3A. It was delayed proportional to the current. 3A took a long time. 8A blew it almost instantly. It got hot, never cut off, but allowed a current below 1A after blowing & continued heating. It would probably explode if the batteries shorted, but it's better than the wire bursting into flames. An HRC fuse would be nice. The normal cruising current with 2 batteries is 1.2A - 1.7A if they're balanced. It might blow on a hill or if the human goes real fast.

The once dubious LED arrangement turned out pretty respectable in its ability to light a large area.

The attempt to glue the wheels failed. The rubber flexed. They instantly popped out of the glue & spun the same as before.
Posted by Jack Crossfire | Sep 16, 2016 @ 10:11 PM | 3,497 Views
Suspect because it was a terrorist attack, the cause of the last Falcon 9 explosion won't be disclosed until after the election & H-Rod already had the talk with Musk Rod, for his sake. It'll be quite the stir when he finally reveals it right after H-Rod's election, but maybe Americans will just think it was politically correct for ISIS to blow it up. More of a stir would be if Emirates, Quatar, & Etihad airlines immediately got into the space tourism business, just like how the Islamic airlines took over the industry after 9/11.


In other news, I was intrigued by the fact that the fictional New Bezos would be larger than the fictional Musk Heavy, yet would make 1.5 million lbs less thrust. Musk's strategy was always to clear the tower as fast as possible. Every second of the liftoff burns enough fuel for 9 seconds of the landing. So he puts out 2 million more lbs of thrust than the weight of the rocket.

The liftoff mass of New Bezos was never given, but it would be comparable to Musk Heavy. A lot more propellant would be burned to clear the tower, so all that size would probably end up giving the same payload capacity as Musk Heavy.

7 Bezos-4 engines would make 3,850,000 lbs of thrust. The Musk Heavy would make 5,200,000 lbs of thrust to hurl 3,200,000 lbs.

New Bezos would offer a much bigger payload fairing. The payload volume on a 3 cored rocket is the same as 1 core, limiting the benefit to manely higher orbits of the same payloads or...Continue Reading
Posted by Jack Crossfire | Sep 15, 2016 @ 12:01 PM | 3,747 Views
It was a white knuckle experience to gang the batteries for the 1st time without polarized connectors. The batteries were chilled to reduce the maximum current. There was a brief sensation of heat which went away. 8.9 miles later, battery 2 in the undercarriage took 2220mAh. Battery 1 in the cargo took 1222mAh. They ran for 87 minutes.

Suspect the higher internal resistance of battery 1 prevented it from discharging as much as battery 2. Battery 2 would have eventually run out enough for battery 1 to supply most of the current.

The balancing tab was always the easiest way to gang batteries, but with the risk of reverse polarization. A fuse is highly recommended. The mane problem is the surge current when accelerating. The fuse might go for too long for battery 1 to supply any current at all.

String held battery 1 in quite well.
Posted by Jack Crossfire | Sep 13, 2016 @ 12:23 PM | 3,228 Views
With a pile of LEDs from the Radioshack sale, it was time to upgrade the lighting. The lighting could be doubled without increasing current, by shuffling voltage regulators.

The lighting would now drop 7V across 2 LEDs. The trick was using a different plug to prevent plugging 7V into the status LED & to prevent the glitches which plagued lighting before. LED voltages ended up disappointingly uneven. The white ones varied from 3.4 to 3.6. The red ones varied from 1.9 to 2.2. Any attempt to go higher would put some white ones at 4V. It's tempting to put them all in parallel again. It would double the current from 80mA to 160mA.

There was an unused 3V regulator on the board. That became the mane electronics regulator. The 1st test lasted 3.6 miles before it overheated. The XBee used too much power. The next step was to feed it from the 5V regulator to dissipate the heat better. That got it down to 50C....Continue Reading
Posted by Jack Crossfire | Sep 10, 2016 @ 12:59 AM | 3,189 Views
Given the time he had to review fault trees, that puts the needle strongly at a terrorist attack. Given the cause of almost every single explosion, plane crash, & mass shooting in the last 8 years, it's the simplest answer. This explosion was too energetic from the beginning to be accidental. We already saw a Falcon 9 oxygen tank fail last year. It seemed to be pretty benign & broke apart rather than exploding. The only times they exploded was a range safety detonation in Texas & when the 1st stage fell over after landing.


Someone picked a time when security would be the most relaxed & the high speed cameras weren't rolling. Maybe it was an inside job. They have to inspect for explosive residue.


The sound 5 seconds before the explosion sounded like a someone getting off a tailgate to see what the f*** just happened. The microphone had too much proximity effect for it to be far away.
Posted by Jack Crossfire | Sep 06, 2016 @ 11:29 PM | 3,450 Views
50% off most items. Tried to remember everything will still be available elsewhere, so didn't buy all the stock. The knobs were some of the best things they had & quite a steal. Online shopping is a fortune, in comparison. Wire cutters, perf boards, & 2 channel pots all sold out at higher prices.
Posted by Jack Crossfire | Sep 06, 2016 @ 02:12 AM | 3,799 Views
Since the EQ sounds so much better on the custom amplifier than it did on the HTR-5230, decided the long term should include a bigger front panel with a knob for the bass & enough room for a treble knob. There's enough room to fit 2 more pots by merely making a slightly wider front panel & mounting the pots diagonally. Also, the order from left to right needs to be power switch, LED, EQ, volume. This is the international front panel standard.

The HTR-5230 had 2 25k pots for the EQ & a 100k pot for balance. The 100k pot was specifically for balance & couldn't be reworked as a resistor divider.

The treble is always going to be at full. Sometimes the bass should be at full & sometimes it shouldn't. This was realized by Japanese decades ago, with their famous bass boost knobs. Helas, the age of bass boost is long gone. Steve Jobless didn't include it on the ipods & everyone has since dropped it. Not sure why this is.

A load switch to disable the amplifier until after the CS4227 initializes is on the plan. The speakers also need a way to easily pitch up & down.
Posted by Jack Crossfire | Sep 04, 2016 @ 11:54 PM | 3,910 Views
It's rare for anything to work when transferred to the final assembly. In this case, the sound was still perfect, but thermal management was gone. The 5V regulator was pegged at 93C. It took a major rework to add a heatsink to it. It's adequate for normal apartment use. The regulators & STA540 stay in the 50C range. For 20Hz sine waves at high volume, fuggedaboutit. The 12V regulator instantly jumps to 100C & shuts down.

There were definite compromises for cost. It would have more power with a PC power supply, but need a lot of space. A 19V laptop brick with linear regulator was the most compact. A lot of wires & heatsinks are flapping in the breeze. It's unsuitable for a vehicle.

Adjusting treble is a buster. The probe points for R1, R2, R3, R4 are shown. R1, R2 determine the treble. They're both 40k when the pot is centered. R1 or R2 is 62k when the pot is fully deflected. The resistances can be calculated by applying parallel resistor equations to the Baxandall schematic.

Bass can be adjusted visually, but the bass pots turn in opposite directions. Probe points for bass resistors are R3, R4. The EQ could be broken out to a front panel extension, but it isn't changed often enough.

The 12V regulator is adjusted with R5 & its output is measured at the cap terminals. Voltage must not exceed 16V or the caps will explode.

The output of the DAC is attenuated with R6, R7 before going to the front panel volume control. The...Continue Reading
Posted by Jack Crossfire | Sep 04, 2016 @ 01:52 AM | 5,148 Views
It came together manely as expected. The mane difficulty was getting the STA540 to work. For the STBY pin, the datasheet says MAX V for play is 1.5V, MIN V for standby is 3.5V. In reality, STBY needs to be pulled up for play & grounded for standby. Trap for young players.

The CS4227 needed a substitute microcontroller to initialize it, as expected. Quite a few more registers had to be set in a certain order to initialize it, which weren't sniffed by the oscilloscope. The YM3436 needed a few pins biased, as expected. Traces had to be cut. The mane challenge was both chips needed reset to be low for a certain time after powering up. The YM3436 wouldn't initialize if reset started out high.

The complete DAC took a lot of power. The +25V rail wouldn't initialize when connected to the 10V regulator. The 10V came from a 5V regulator with a 5V virtual ground, but the +25V rail started below 5V. The regulator seemed to detect the +25V rail starting below its virtual ground of 5V & shut down by some kind of SCR latchup. +25V ended up connected to the raw 12V. The 5V virtual ground initialized properly.

The total quiescent current with the power amplifier & DAC was an insane 0.35A. The 2 5V regulators got quite hot. The STA540 needed a large heatsink. The mane problem when playing sound was the DAC needed its ground connected directly to the ground on the STA540. Connecting it anywhere else on either the signal or power ground caused distortion....Continue Reading
Posted by Jack Crossfire | Sep 02, 2016 @ 12:03 PM | 3,245 Views
In the blog's opinion, it was an electrical fire in the avionics package. The 2nd stage wasn't firing its engines. There's no umbilical where the explosion started. The explosion started where the avionics are. It would have been burning for some time before getting into the LOX tank.

The mane effect is redesigning & certifying the avionics package will take a year. There's no PC board manufacturing capability in US. Every revision has to be made in China, which takes months. There won't be any astronaut capability until the next decade. Fortunately, NASA bought Soyuz flights into the next decade. Pad 40 will be abandoned in place. They'll have to wait for pad 39 to be finished.

The money flow will be affected. Of NASA's 2 commercial ventures, the commercial cargo venture was executed as well as can be. It got a few flights off before becoming dominated by failure. As consumer prices rose, the failure rate also rose until the last 2 years weren't adequate to supply the ISS. The commercial astronaut venture was never fully funded at all. In its 7 year history, nothing flew.

H-Rod will continue the 2 commercial ventures, but there won't be another one of the same magnitude. The commercial crew venture will be funded a lot more slowly, to be sure. The SLS won't be replaced by a commercial vehicle where it might have been last week. There won't be any NASA money for the raptor engine. Military contracts will go back to ULA.