[HN Gopher] Crashing rockets and recovering data from damaged fl...
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       Crashing rockets and recovering data from damaged flash chips
        
       Author : xyx0826
       Score  : 40 points
       Date   : 2024-12-16 19:20 UTC (2 days ago)
        
 (HTM) web link (dontvacuum.me)
 (TXT) w3m dump (dontvacuum.me)
        
       | polishdude20 wrote:
       | Might be worth it to pot the flash chip in some epoxy or
       | something. Heck, add another one and double it up for redundancy.
        
       | russdill wrote:
       | They should have first attempted going without VCC and GND. Just
       | make sure CS# is hooked to ground and WP is hooked to VCC.
       | 
       | Both pads would have protection diodes to VCC/GND providing
       | phantom power when tied to the appropriate rail. Plenty of chips
       | work fine with phantom power.
        
         | 0_____0 wrote:
         | That's a cool idea. Going to file that away for another time. I
         | imagine you'd maybe run your phantom voltage a little higher to
         | overcome the ESD diode drop?
        
           | russdill wrote:
           | The voltage drop is probably already accounted for in the
           | allowable range unless it's a very low voltage chip. The main
           | concern is you can't get away with anything high current. An
           | SPI flash chip should be ok though, it's only driving one pin
           | and you can choose whatever rate you want.
        
       | jandrese wrote:
       | Interesting use of a salt solution to weep into the broken parts
       | to make contact. I personally would be shitting diamonds if I was
       | reduced to this, it seems like it would be way too easy to short
       | out the board with this method, especially when the packaging is
       | so badly mangled.
       | 
       | I probably would have tried slowly and carefully whittling away
       | the plastic near where the bond wires used to be to try to expose
       | some metal first before using this salt water bath idea, but if
       | it works it works.
        
         | 0_____0 wrote:
         | This is a big enough package that it has a lead frame, and
         | same, I would have been using mechanical removal processes to
         | gain access to it.
        
       | PittleyDunkin wrote:
       | > the rocket dropped unchecked and burried [sic] itself 3 meters
       | underground.
       | 
       | Very impressive! I wonder at what speed it impacted. I tried
       | reading the chart at the bottom but I'm not sure what "axial"
       | velocity is--probably not vertical speed given it drops over time
       | rather than rises as the rocket dropped.
       | 
       | I suppose you could take the derivative of the height at impact
       | point but I'm too lazy.
        
         | mgsouth wrote:
         | The red line is axial acceleration. The rocket rapidly slows to
         | terminal velocity, reaching it at about 25 sec., then continues
         | to slowly decelerate as t.v. decreases as the air gets thicker.
         | [edit: *] The black line is estimated velocity, as integration
         | of the acceleration. It gives up trying to calculate that at
         | about 45 sec. Based on the barometer readings, it looks like it
         | was going about 650 fps at impact.
         | 
         | What I find interesting is the 4-second delay before igniting
         | the second stage. This is very inefficient compared to
         | immediately igniting it when the first stage burns out. Max-Q
         | (airspeed pressure) issues? 30,000 ft permit ceiling?
         | 
         | Edit: * At 25 sec. it's still going up, so the velocity is
         | decreasing due mainly to gravity, but the rocket is ballistic
         | so the accelerometer is slightly negative due to air friction
         | adding to the gravity deceleration. At about 40 sec. it has
         | reached max altitude and velocity is zero. Accelerometer is
         | still close to zero. Velocity picks up, as shown by barometric
         | altitude curve. Eyeballing it, at about 65 sec. its reached
         | terminal velocity, as shown by barometer curve being pretty
         | flat. Decrease after that is due to decreasing t.v.
        
           | Marthinwurer wrote:
           | With solid motors lower in the atmosphere with high velocity
           | it's often optimal to delay second stage ignition so that
           | your sustainer motor isn't working against as much
           | atmosphere. So, kinda Max-Q issues, but for performance
           | reasons.
        
       | wildekek wrote:
       | Dennis is also one of the (if not THE) leading vacuum robot
       | hacker and makes https://github.com/dgiese/dustcloud. Amazing
       | work.
        
       | racked wrote:
       | What is that circular kit with the stands and pins that he's
       | using here?
       | https://dontvacuum.me/rocketflashrecovery/needles-1.jpg
       | 
       | Reminds me of PCBite
        
         | russdill wrote:
         | https://www.aliexpress.us/item/3256807898318737.html
        
       | two_handfuls wrote:
       | Great writeup, cool photos, no ads. Thank you!
        
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       (page generated 2024-12-18 23:01 UTC)