highaltitude.log.20090807

[00:13] <Laurenceb> you can get OS maps off getamap
[00:14] <Laurenceb> itd just take an automated reader...
[00:14] <Laurenceb> ideally convert them to digital elevation ect
[00:14] <Laurenceb> read off the contours
[00:16] <SpeedEvil> ASTER and SRTM data is already available with global elevations.
[00:16] <SpeedEvil> (well - not quite global for SRTM)
[00:29] Nick change: KingJ -> kingj
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[09:17] <Laurenceb> hi
[09:30] <Laurenceb> edmoore: ping
[09:30] <edmoore> morning Laurenceb
[09:30] <Laurenceb> hi
[09:30] <Laurenceb> could hobble launch a rocket?
[09:31] <edmoore> well, in so far as it's a gondola hanging under a balloon...
[09:31] <Laurenceb> just a crazy idea I was thinking of :P
[09:32] <Laurenceb> thing is youd want to use a launch tube
[09:32] <Laurenceb> and thatd want to be rifled
[09:32] <Laurenceb> the torque could screw things up as the rocket fired
[09:32] <Laurenceb> probably better to spin up the rocket with a motor
[09:32] <Laurenceb> then it would be gyroscopically stable anyway
[09:33] <edmoore> where does hobble come into this?
[09:33] <Laurenceb> it doesnt
[09:34] <Laurenceb> yeah its probably not actually useful for this
[09:35] <edmoore> :)
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[09:37] <Laurenceb> I think I've worked out a way to launch a two stage spin stabilised rocket - no thrust vectoring
[09:38] <Laurenceb> if this horrible geometery works then you can reaim the second stages spin axis using a small momentum wheel and a couple of photodiodes as sun sensors
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[11:13] <SpeedEvil> :)
[11:15] <Laurenceb> hi SpeedEvil
[11:16] <Laurenceb> looks like this latest idea works
[11:16] <Laurenceb> got the cost down to £400
[11:18] <Laurenceb> basically spiun launch from a HAB platform, then the second stage and a momentum wheel deploys from the first
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[11:18] <SpeedEvil> the momentum wheel is used to precess the spinning second stage or something?
[11:18] <Laurenceb> if I've got this right you can spin up the wheel then chuck it off ther side to precess the second onto target
[11:19] <Laurenceb> yeah
[11:19] <Laurenceb> you could use a photodiode to check the alignment
[11:21] <Laurenceb> you can get the total mass down to 2.2Kg or so
[11:21] <SpeedEvil> interesting.
[11:22] <SpeedEvil> what's the laucher platform - 3 axis stablised, with spinner and launch tube?
[11:22] <Laurenceb> not sure
[11:22] <Laurenceb> I was thinking maybe a passively stabilised
[11:22] <rjharrison> Laurenceb, Hi
[11:22] <Laurenceb> using polythene film - like hallams floater
[11:22] <Laurenceb> hi
[11:23] <rjharrison> I have been reading alot on SPI and ISP and AVR's
[11:23] <rjharrison> And I have found this app note http://www.atmel.com/dyn/resources/prod_documents/doc0943.pdf
[11:23] <Laurenceb> SpeeDevil: then the elevation set by rigging and the azimuth set using a magnetometer and small prop on a CF pole
[11:24] <rjharrison> Page 3 suggests no R's on the ISP
[11:24] <Laurenceb> use a brushless motor to spin up the rocket
[11:24] <SpeedEvil> Laurenceb: hmm
[11:24] <SpeedEvil> rjharrison: SPI is open-collector isn't it?
[11:25] <rjharrison> I'm open to further input as there seems to be alot of conflicting info regarding ISP SPI and AVR's
[11:25] Action: SpeedEvil just woke up.
[11:25] <Laurenceb> ah the isp keeps reset low
[11:25] <rjharrison> SpeedEvil, Your asking the wrong person here
[11:25] <Laurenceb> yeah in theory - depenmds if all programmers follow that rule
[11:25] <Laurenceb> SpeedEvil: once the rocket is spun up, the platform should be more stable
[11:26] <rjharrison> Ok guys im going to get the prototyping kit out and knock up a test
[11:27] Action: Laurenceb smells buring chips
[11:27] <Laurenceb> *burning
[11:27] <SpeedEvil> Ah - I'm thinking of I2C
[11:27] <SpeedEvil> rjharrison: what's your question?
[11:28] <rjharrison> Yep my finger has healed from my last solder bridge
[11:28] <rjharrison> Shorted the Linear eg
[11:28] <rjharrison> Reg
[11:28] <SpeedEvil> My finger still has a bump where it got bitten by a NiCd cell + hot wire some years ago
[11:29] <rjharrison> SpeedEvil, I'm trying to find the right circuit to interface SD card, ISP connector and AVR
[11:29] <SpeedEvil> ah right.
[11:30] <Laurenceb> you at least want a resistor on MISO
[11:30] <rjharrison> MISO ISP or MISO SD
[11:30] <Laurenceb> http://www.micronradiocontrol.co.uk/micro_brushless.html#hx-2g-7700 <- speed
[11:30] <Laurenceb> SD
[11:30] <SpeedEvil> The point of hte resistors above is to let the SPI programmer force the peripheral - 'SD card' in this case -lines high or low
[11:31] <SpeedEvil> Without damaging currents flowing.
[11:31] <rjharrison> IS that R to Vcc or GND
[11:31] <SpeedEvil> If you have a SPI socket - you could remove the SD card insted
[11:31] <SpeedEvil> if you have a SD socket
[11:32] <rjharrison> I think it's more to do with the AVR becomming a master when the ISP programmer is in there
[11:32] <rjharrison> I maybe wrong
[11:32] <SpeedEvil> It's not - the programmer knows what the AVR will do.
[11:32] <SpeedEvil> It's designed to do it in lock-step.
[11:32] <SpeedEvil> However.
[11:33] <SpeedEvil> If there is another random thing - the SD card - on the SPI bus too - odd things happen.
[11:33] <rjharrison> Ok cool well I'll get a fettling tonight and see what happend
[11:33] <rjharrison> s
[11:33] <SpeedEvil> So the SD card effectively just is disconnected by the resistors.
[11:33] <Laurenceb> yeah from a app note looks like the programmer _should_ always force reset low
[11:34] <SpeedEvil> microSD have no reset IIRC
[11:34] <rjharrison> Cool so put 1k rs in series with the SD lines
[11:34] <SpeedEvil> Or is that CS
[11:34] Action: Laurenceb wonders how small you can go iff all the electronics weighs a few grams
[11:34] <SpeedEvil> rjharrison: yes - that's nice safe.
[11:34] <Laurenceb> reset on the uC
[11:35] <rjharrison> MISO MOSI and SCK
[11:35] <SpeedEvil> Laurenceb: if you total up the electronics mass using BGAs and a thin multilayer PCB you can get to really quite low masses.
[11:35] <Laurenceb> I was looking at the model plane kit
[11:35] <rjharrison> I assume the 1KR's are not going to affect data comms to bad
[11:35] <Laurenceb> 2gram brushless motors :P
[11:35] <SpeedEvil> rjharrison: not at normal speeds - no
[11:36] <rjharrison> I'll leave you in peace now
[11:36] <SpeedEvil> Laurenceb: yeah - that sort of stuff is insane
[11:36] <rjharrison> Thanks guys for your time
[11:36] <SpeedEvil> np
[11:36] <rjharrison> I'll write this up for the wiki
[11:36] <SpeedEvil> good luck
[11:37] <rjharrison> DanielRshman or whatever his name is has written some code to log to SD
[11:37] <rjharrison> But he's using an premade board so I hope to put in a schematic to go with the code
[11:37] <rjharrison> ttfn
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[11:39] <SpeedEvil> ilalauHow critica; is pointing
[11:40] <Laurenceb> hey?
[11:42] <SpeedEvil> how critical is pointing?
[11:44] <Laurenceb> +-0.5 degrees or so
[11:47] <Laurenceb> http://en.wikipedia.org/wiki/Red_mercury <- the answer to our problems?
[11:51] <SpeedEvil> :)
[11:52] <Laurenceb> Believers in the rumor claimed that the presence of red mercury in the sewing machines' needles could be detected using a mobile telephone; if the line cut off when the telephone was placed near to the needle
[11:53] <Laurenceb> ^ lol lol lol
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[12:44] <Hiena> Laurenceb, aaaaaaauuuughhh...
[12:51] <Laurenceb> what?
[12:58] <Hiena> The wikipedia entry.
[13:23] <Laurenceb> SpeedEvil: yeah I think a single reaction wheel and two photodiodes would work
[13:24] <Laurenceb> you can detect the sun and the scattered light from the earth
[13:26] <SpeedEvil> hmm
[13:26] <SpeedEvil> sounds reasonable
[13:26] <Laurenceb> _very_ cheap
[13:26] <Laurenceb> http://www.vishay.com/docs/81317/temt6200.pdf
[13:28] <Laurenceb> http://www.rocketstore.co.uk/shop/product.asp?numRecordPosition=3&P_ID=962&strPageHistory=cat&strKeywords=&SearchFor=&PT_ID=181 <- you could use that motor for the first stage
[13:41] Action: Laurenceb is pondering an exploding foil cutdown
[13:54] <Laurenceb> not quite sure how you release the reaction wheel
[13:54] <Laurenceb> really need a <1ms release mechanism
[13:57] <SpeedEvil> magnetic?
[13:58] <Laurenceb> http://twitter.com/ukhas oh god no I've lost all faith now
[13:58] <Laurenceb> hmm maybe
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[14:00] <rjharrison> Laurenceb, you still sround
[14:00] <Laurenceb> yes
[14:01] <rjharrison> I was contemplating a visit to the field
[14:01] <rjharrison> You have any options open?
[14:02] <Laurenceb> yeah I may be around next week
[14:02] <rjharrison> w/e an optin ?
[14:02] <rjharrison> option
[14:06] <Laurenceb> probably not, sorry
[14:07] <rjharrison> np
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[14:11] <rjharrison> edmoore apparently 30 caps are going to be dispatched to you
[14:12] <edmoore> ok cool
[14:14] <edmoore> rjharrison http://www.flickr.com/photos/cuspaceflight/
[14:14] <edmoore> a couple of new photos, checking out these incredibly fiddly awkward parts on badgercub
[14:16] <rjharrison> wow is that like an xray or something
[14:16] <Laurenceb> how are you programming it?
[14:16] <edmoore> exactly that
[14:16] <edmoore> with the TI programmer
[14:16] <rjharrison> Nice to have a lab like that to hand
[14:17] <rjharrison> Keep your bollox out of the way :)
[14:17] <Laurenceb> interesting to see the dies inside
[14:18] <edmoore> agreed - you can see the rf section and the processing section on the venus
[14:18] <Laurenceb> and a crystal?
[14:18] <Laurenceb> or two? or is that sheilding?
[14:19] <edmoore> it's internal to the chip, whatever it is
[14:19] <Laurenceb> solder paste and oven?
[14:19] <edmoore> yep
[14:19] <Laurenceb> nice job
[14:19] <edmoore> 19.99 from argos
[14:19] <Laurenceb> heh
[14:20] <Laurenceb> but... cant you check from the sides with a magnifying glass?
[14:20] <rjharrison> toaster?
[14:20] <edmoore> yeah he technician was saying a suprising number of places have these xray machines. you just have to wander in and ask nicely if you can waste some of the technician's time with your pcb
[14:21] <edmoore> Laurenceb: not if it's an LGA package
[14:21] <Laurenceb> or use a multimeter - if your worried about frying, build something with a few mv and limited current
[14:22] <Laurenceb> I used the same technique to fix a ublox5
[14:24] <SpeedEvil> LGA can be doable
[14:24] <SpeedEvil> you can see it with very bright insulation
[14:24] <SpeedEvil> err
[14:24] <SpeedEvil> where the hell did that come from
[14:25] <SpeedEvil> I think I was thinking of DIY again - and insolation
[14:25] <SpeedEvil> anyway
[14:25] <SpeedEvil> especially if the pads extend to or beyond the edge of the chip outline - you can easily see the difference
[14:25] <edmoore> rjharrison: in this case they don't
[14:25] <edmoore> whoops, that wasn't meant for rjharrison
[14:26] <Laurenceb> what happened to the cutdown page on the wiki?
[14:26] <edmoore> the wiki is being re-ordered I think
[14:26] <Laurenceb> what compiler are you using for the chipcon?
[14:26] <Laurenceb> any idea what size cap the pyros use?
[14:29] <Laurenceb> http://8051help.mcselec.com/index.html <- aha
[14:29] <Laurenceb> :P
[14:30] <Laurenceb> j/k
[14:30] <edmoore> i think anything sort of 220uF-470uF is fine
[14:30] <Laurenceb> interesting
[14:30] <Laurenceb> thats pretty small
[14:30] <Laurenceb> guess the bridgewire must be very small
[14:31] <Laurenceb> that should work with SMD tantalums then
[14:31] <Laurenceb> edmoore: ceramic 434MHz ant?
[14:34] <edmoore> no, just co-ax like usual
[14:34] <Laurenceb> fairdoos
[14:34] <Laurenceb> btw my chipcon test hab is ready to fly
[14:34] <Laurenceb> so we'll see how they fair
[14:35] <Laurenceb> but the firmware seems to be pretty datf, IMO your losing at least 10dB equivalent
[14:37] <Laurenceb> I plan to have a go at reflashing them with my own firmware at some point
[14:42] <RocketBoy> 220uF is well at the low end IMO - N28Bs are one of the most sensative ignitors - their nominal spec is 1A for 2ms into 1.6 ohm = 3.2mJ, a 220uF at 5V is 2.7mJ
[14:43] <Laurenceb> interesting
[14:43] <Laurenceb> for reaction wheel release you need a ms or so
[14:44] <Laurenceb> so that looks pretty nice
[14:44] <RocketBoy> 2ms is just the time they take to initiate - the actual flare is someway behind that
[14:45] <Laurenceb> but youd be able to rely on the timing quite well?
[14:46] <RocketBoy> I don't know - one of the things it would be worth testing on the CUSf high speed camera
[14:46] <Laurenceb> yeah :P
[14:46] <RocketBoy> I think fergaus was going to test some of my cutdowns on it - I gave him some to try.
[14:47] <Laurenceb> need an led in frame to show the applied power
[14:47] <RocketBoy> yeah
[14:48] <RocketBoy> bbl
[14:50] <rjharrison> here here for slow-mo pyros. I have some if anyone wants some for test
[14:51] Action: Laurenceb sticks some on a n prize rocket instead
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[15:04] <Laurenceb> http://www.flickr.com/photos/cuspaceflight/3741842127/sizes/l/in/photostream/
[15:04] <Laurenceb> heh I'm holding the yagi
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[16:23] <jcoxon> afternoon all
[16:27] Nick change: kingj -> KingJ
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[16:44] <jcoxon> hey natrium42
[16:44] <natrium42> ohi
[16:44] <natrium42> how are you?
[16:45] <jcoxon> good thanks
[16:45] <jcoxon> you?
[16:45] <natrium42> also
[16:45] <jcoxon> excellent
[16:47] <edmoore> fergus's electronics killing score-card so far today stands at about £25
[16:47] <jcoxon> just re-organsing the wiki
[16:47] <jcoxon> edmoore, oh dear
[16:48] <edmoore> managed to internally kill a venus gps
[16:48] Action: natrium42 is finishing firmware/library for his usb stepper controller
[16:48] <edmoore> this is what a venus gps looks like in a dead state internally http://www.flickr.com/photos/cuspaceflight/3798212556/sizes/o/
[16:48] <jcoxon> i'm not sure what it should look like!
[16:48] <natrium42> edmoore, whoa, nice
[16:49] <edmoore> well we took that thinking it was alive, just to check the soldering, but it turns out it's dead
[16:49] <natrium42> how did you kill it?
[16:49] <edmoore> i don't know if it looks any different to how it does alive, i just like to image those black blobs are little craters from a violent internal popcorning death
[16:50] <edmoore> probably one too many cycles in the oven
[16:50] <jcoxon> what do you guys think about: http://wiki.ukhas.org.uk/start
[16:50] <jcoxon> too simple?
[16:51] <SpeedEvil> Needs more pictures
[16:51] <edmoore> yeah just plonk some piccies up - they'll know they've come to the right place
[16:51] <edmoore> feel free to steal any of ours
[16:51] <SpeedEvil> I would also lose the 'with fldigi' on the end of tracking
[16:51] <jcoxon> i was thinking of using the panoramic as the title background
[16:52] <SpeedEvil> I would also retitle 'getting started' 'beginners guides' - then nuke the beginners guides off the front of the topics.
[16:52] <SpeedEvil> with a seperate topic - 'current events' - for lauches
[16:56] <natrium42> edmoore, use electrical skillet :P
[16:56] <natrium42> it's easier to see what's going on
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[16:57] <edmoore> natrium42: with xray you can see the whole world in see-through :)
[16:57] <edmoore> i want to start x-raying shit now
[16:57] <Laurenceb> I've heard the venus can be a bit dodgy
[16:57] <jcoxon> edmoore, become a radiologist
[16:58] <SpeedEvil> If they've not been in a controlled humidity environement, I'd bake
[16:58] <Laurenceb> halfbake
[16:59] <edmoore> jcoxon: 7 years of med school just to extray shit?
[16:59] <edmoore> I was thinking more like taking random things to the technician
[17:01] <jcoxon> edmoore, hehe
[17:01] <jcoxon> you could be a radiographer
[17:01] <jcoxon> they ain't doctors
[17:07] Action: SpeedEvil wishes MRI was cheap.
[17:08] <Laurenceb> have you seen that mri experiment using basic coils
[17:08] Action: Laurenceb tries to remember
[17:08] <SpeedEvil> yeah - one or two pixel is easy
[17:08] <Laurenceb> capacitance tomography
[17:08] <SpeedEvil> Though I wonder about the possibility of relatively inexpensive units for arms or knees.
[17:09] <SpeedEvil> Snes fusion will be the next big thing.
[17:09] <SpeedEvil> sensor fusion.
[17:09] <Laurenceb> lol
[17:09] <SpeedEvil> Ultrasound + capacitance + IR + ...
[17:09] <Laurenceb> super nintendo fusion system
[17:10] <SpeedEvil> A fusion of comparatively crappy sensors to make one actually not crappy sensor.
[17:10] <Laurenceb> dont you mean a synergy :P
[17:10] <SpeedEvil> Umm.
[17:10] <SpeedEvil> I don't think so.
[17:10] <SpeedEvil> Not quite anyway.
[17:10] Action: Laurenceb sends speedevil to corporate bs class
[17:11] <SpeedEvil> As the sensors aren't so much as compensating for each others weaknesses - more used to enhance the whole model.
[17:11] <SpeedEvil> Maybe.
[17:11] <jcoxon> http://wiki.ukhas.org.uk/start
[17:11] <Laurenceb> http://wiki.ukhas.org.uk/stop
[17:11] <jcoxon> thanks Laurenceb
[17:11] <Laurenceb> np
[17:11] <SpeedEvil> Looking good.
[17:12] <Laurenceb> nice banner
[17:12] <SpeedEvil> you're going to link the picture to something I assume?
[17:13] <jcoxon> SpeedEvil, i was thinking to the source really
[17:13] <jcoxon> i could make hte banner bigger but am worried about peoples resolution
[17:13] <Laurenceb> jcoxon: we seem to be missing the info on cutdowns
[17:14] <Laurenceb> I was looking for it earlier
[17:14] <SpeedEvil> jcoxon: yeah - and maybe a short description of it.
[17:14] <jcoxon> http://wiki.ukhas.org.uk/ideas:flight_support#pyrotechnic_cutdown_device ?
[17:14] <jcoxon> i could tooltip it
[17:15] <Laurenceb> doh
[17:15] <Laurenceb> ok sorry
[17:15] <jcoxon> Laurenceb, but perhaps a cutdown page would be more appropriate
[17:15] <SpeedEvil> I think the banner is about as large as you want to go
[17:15] <jcoxon> SpeedEvil, yeah
[17:16] <SpeedEvil> An argument could even be made for smaller - it's a fairly low-res image - there aren't many pixels that justify 1024 wide even
[17:16] <SpeedEvil> Actually no - you'd lose some of the fine texture - which is nice
[17:17] <jcoxon> oh i've had to resize it massively already
[17:19] <edmoore> the original is about 14mB!
[17:20] <edmoore> MB*
[17:22] <jcoxon> okay how about that
[17:22] <jcoxon> added a link + tooltip about hte photo
[17:24] <Laurenceb> SpeedEvil: you could make a cool capacitance scanner with one of the AD capdacs
[17:25] <Laurenceb> use one or two of them then a manipulator arm to scan the target
[17:25] <SpeedEvil> Laurenceb: yeah
[17:25] <SpeedEvil> Laurenceb: naah
[17:25] <Laurenceb> image reconstruction is the hard bit
[17:25] <SpeedEvil> Laurenceb: couple of optical mice heads
[17:26] <Laurenceb> how does that work?
[17:26] <SpeedEvil> The mice heads scan the motion of the scanner bar
[17:26] <Laurenceb> guess so
[17:26] <Laurenceb> or just a couple of servos
[17:26] <SpeedEvil> I was thinking Cheeeeep!
[17:26] <Laurenceb> I was working on image reconstruction a while back
[17:26] <Laurenceb> servos are cheap
[17:27] <SpeedEvil> A wand - pretty much - with nothing else other than a USB lead
[17:27] <Laurenceb> thinking of something monte carlo based
[17:27] <Laurenceb> very computationally intensive, but should be capable of producing good results with enough data
[17:27] Action: SpeedEvil imagines a roulette wheel - with diseases round the outside.
[17:27] <SpeedEvil> 'very'
[17:28] <SpeedEvil> A lot of the current scanners came in when mobile phones weren't supercomputers :)
[17:28] <Laurenceb> exisitng attempts use ~20 electrode compinations
[17:28] <Laurenceb> and linear image reconstruction techniques
[17:29] <Laurenceb> I've yet to see anything decent with capacitance tomography
[17:29] <Laurenceb> but you should be able to do some cool stuff with enough data
[17:30] <SpeedEvil> yeah
[17:32] <Laurenceb> I saw an experiment where they scanned a carrot in a pot at about 50 pixel resolution
[17:32] <Laurenceb> it was good enough to see the water takeup and things
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[17:32] <SpeedEvil> neat
[17:33] <jcoxon> ping RocketBoy
[17:34] <RocketBoy> I saw a real time electrical resistance tomography working onece - really simple - quite cool
[17:34] <RocketBoy> yo
[17:34] <jcoxon> is your bbc thingy majig next week or the week after
[17:34] <Laurenceb> yeah, but the inversion problem is similar in resistivity tomography
[17:34] <RocketBoy> week after
[17:34] <jcoxon> oh damn, will miss it by a few hours then
[17:34] <jcoxon> am flying out on that monday
[17:35] <RocketBoy> it'll be on iplayer
[17:35] <Laurenceb> RocketBoy: it touches on a problem BT have - finding faults in underground cable
[17:35] <SpeedEvil> Laurenceb: how?
[17:35] <jcoxon> RocketBoy, hopefully will still be there when i get back in october :-p
[17:35] <SpeedEvil> Laurenceb: surely TDR does that
[17:35] <SpeedEvil> I'll record it off iplayer
[17:35] <Laurenceb> I built a device to solve the problem using 100KHz ground currents
[17:35] <SpeedEvil> what is the thing on?
[17:36] <Laurenceb> SpeedEvil: you dont have enough bandwidth
[17:36] <SpeedEvil> I mean - if the cable is internally faulty
[17:36] <Laurenceb> for TDR
[17:36] <jcoxon> Bang goes the theory on mondays at 7.30pm
[17:36] <Laurenceb> headphone smashing
[17:36] <SpeedEvil> Laurenceb: The BT man with his TDR thingy would seem to disagree with you
[17:36] <Laurenceb> not for earth leakes on twisted pair
[17:36] <SpeedEvil> jcoxon: ah - I have the previous one
[17:36] <SpeedEvil> Laurenceb: true
[17:37] <Laurenceb> you can sometimes get to within a hundered m or so like that
[17:37] Action: SpeedEvil is wondering why my line is currently faulty
[17:37] <Laurenceb> but its a problem with no off the shelf solutions - or was a couple of years ago when I built my detector
[17:37] <SpeedEvil> Though it seems to have gotten better after they 'switched interleave on' - it was already on.
[17:37] <Laurenceb> SpeedEvil: ~100KHz PRN code down the line
[17:38] <Laurenceb> leakes out of the fault and induces ground currents
[17:38] <Laurenceb> then you have a directional antenna
[17:38] <RocketBoy> normally BT use measurement of the timing of the relection from an impedance change to locate faults - down to a few feet
[17:38] <SpeedEvil> eyah - they implied it was lots better than 100m
[17:38] <SpeedEvil> of course.
[17:39] <Laurenceb> the guys I spoke to said it was an unsolved problem
[17:39] <SpeedEvil> You may not get good results at 4000m.
[17:39] <SpeedEvil> But if you've got it hooked onto a cable - you get good results in short distances.
[17:39] <Laurenceb> ok for shorts and some damage
[17:39] <SpeedEvil> but that doesn't work for earth
[17:39] <Laurenceb> but often there was earth leaks that screwed up the analogue phone service
[17:39] <Laurenceb> partly due to the higher voltage
[17:40] <SpeedEvil> I'm getting random interference I think at 11PM-2AM or so
[17:40] <Laurenceb> I used about 30V - boosted with a transformer
[17:40] <SpeedEvil> sometimes it's out for 1/2 hour or more
[17:40] <Laurenceb> I got it working really well, ~15cm error
[17:40] <SpeedEvil> you apply the PRN differentially across the pair - centre tapped at earth?
[17:40] <Laurenceb> yes
[17:41] <Laurenceb> actually different PRN codes
[17:41] <jcoxon> SpeedEvil, any HAM radio people around?
[17:41] <Laurenceb> one applied equally, one differentially
[17:41] <SpeedEvil> jcoxon: hmm
[17:41] <Laurenceb> so you can track the cable and monitor it for faults
[17:41] <jcoxon> i've heard stories of it interfereing
[17:41] <SpeedEvil> jcoxon: The one I would have said yes to has died I think.
[17:42] <Laurenceb> my test rig just had some rows of leds, but ideally youd have a graphic lcd
[17:42] <SpeedEvil> jcoxon: Also - it's on 100% of the time when it's faulty
[17:42] <SpeedEvil> jcoxon: which would rule out at least voice
[17:42] <SpeedEvil> For most people anyway.
[17:43] <SpeedEvil> Annoying - as (with the right tweaks) - the line will go over 2M
[17:44] <jcoxon> wonder what else could interefere at those times of day
[17:44] <SpeedEvil> I've had no time really to dig into this sort of stuff.
[17:47] <Laurenceb> RocketBoy: apparently there was a test rig called the "c-frame?" built at BT to experiment with this idea?
[17:51] <Laurenceb> I think they tried it with about 15KHz and viewing the signals on a scope
[17:51] <Laurenceb> with higher frequency and PRN you can go to a much smaller antenna
[17:52] <Laurenceb> the tricky bit is filtering out mains ect without it saturating the front end
[17:53] <SpeedEvil> 16 bit 1MHz ADCs
[17:53] <SpeedEvil> make it lots easier
[17:54] <Laurenceb> fraid not
[17:54] <Laurenceb> mains is up to 140dB stronger than the signal
[17:55] <SpeedEvil> I mean - easier.
[17:55] <Laurenceb> true
[17:55] <Laurenceb> mains is the big problem
[17:55] <SpeedEvil> 90dB SNR from the ADC help oodles
[17:55] <SpeedEvil> A nice sharp few hundred Hz filter to drop it by 60dB isn't implausible
[17:55] <Laurenceb> you have to have very good filtering right at the front end
[17:56] <Laurenceb> yeah
[17:56] <Laurenceb> and making it stable was a pain
[17:56] <Laurenceb> I'll have to go back and have another attempt with the thing
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[17:57] <Laurenceb> but I got minor earth faults trackable from 30m or so
[17:57] <Laurenceb> and it didnt mind concrete/tarmac
[18:04] <Laurenceb> mainly due to the fact you have a constant moisture layer starting less than 30cm down
[18:05] <Laurenceb> gtg, cya
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[18:50] <Laurenceb> hi again
[18:50] Action: Laurenceb had an idea
[18:50] <Laurenceb> spin stabilised martlet
[18:51] <Laurenceb> HAB with an unmodified motor in a basic finless rocket
[18:51] <Laurenceb> then a brushless spinup motor
[18:51] <Laurenceb> and rigged to launch at 15 degrees of vertical or so to miss the balloon
[18:51] <Laurenceb> nice and easy 100Km :P
[19:18] <Laurenceb> http://digitalurban.blogspot.com/2009/08/iphone-3d-texture-mapped-city-paris.html <- how did they get the data?
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[19:41] <Laurenceb> hi edmoore
[19:41] <edmoore> hi Laurenceb
[19:41] <Laurenceb> I found a book for you http://hackadaycom.files.wordpress.com/2009/08/title.jpg?w=382&h=500
[19:42] <edmoore> perfect, how did you know?
[19:42] <Laurenceb> heh
[19:43] <edmoore> I listened to AO-51 with the handheld at 18:13
[19:43] <edmoore> really quite load, completely broke squelch and was very comprehendible, just with handheld's whip
[19:43] <Laurenceb> I was thinking about martlet, why not just stick a basic finless rocket on a brushless motor based spinup device
[19:44] <Laurenceb> then launch at ~15 degrees off vertical
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[20:12] <RocketBoy> what sort of spin speeds are you thinking you will need - I think shells are circa 15,000RPM?
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[20:30] <Laurenceb> <1000rpm
[20:37] <RocketBoy> cool
[20:38] <Laurenceb> brushless motor
[20:38] <Laurenceb> and a bearing further up to stabilise the body
[20:39] <Laurenceb> it looks pretty easy - the spin up mechanism is the only untried bit
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[20:44] <Laurenceb> just a large sealed bearing unit would work
[20:47] <RocketBoy> three smaller bearings at 120 degrees would be easier IMO.
[20:48] <Laurenceb> maybe
[20:57] <Laurenceb> what like rollers?
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[21:04] <RocketBoy> yeah
[21:05] <RocketBoy> I could ground test it as a rotating tube launcher
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[21:09] <RocketBoy> The August BBC Focus mag with e http://randomsolutions.co.uk/gash/focusmag001.pdf
[21:09] <RocketBoy> the BGTT HAB article
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[21:24] <RocketBoy> factually incorrect in places and i didn't say some of the quotes.
[21:36] <grummund> hmm, that looks so much fun..
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[22:59] <Laurenceb> oh bang goes the theory?!
[22:59] <Laurenceb> when was this?
[23:01] Nick change: kingj -> KingJ
[23:01] <Laurenceb> photos look good, I see EARS
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[23:03] <Laurenceb> RocketBoy: looks good
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[23:12] <RocketBoy> ta - not too shoddy - XABEN7(doll) & XABEN8(main payload)
[23:13] <Laurenceb> when was this launched?
[23:14] <RocketBoy> June 9th
[23:14] <Laurenceb> I never heard, was it a bit secret?
[23:15] <RocketBoy> yep
[23:15] <Laurenceb> heh
[23:15] <Laurenceb> was the camera arm motorized?
[23:15] <RocketBoy> no just a balanced boom
[23:15] <Laurenceb> I see
[23:15] <Laurenceb> what cameras where they using?
[23:16] <RocketBoy> one end of the boom had a camera pointing up the other had a camera pointing at the doll (and horizon)
[23:16] <RocketBoy> flip HD
[23:17] <RocketBoy> (minos not ultras)
[23:17] <RocketBoy> they were a bit oof a pig - heat and RFI problems to solve
[23:18] <Laurenceb> ah
[23:23] <Laurenceb> hmm yeah suitable bearing units are hard to find
[23:31] <Laurenceb> http://simplybearings.co.uk/shop/p170242/6812+Budget+Open+Type+Thin+Section+Deep+Groove+Ball+Bearing+60x78x10mm/product_info.html
[23:31] <Laurenceb> ^ would do
[23:33] <SpeedEvil> I got some much finer ones
[23:33] <SpeedEvil> ebay
[23:33] <SpeedEvil> of the order of 6mm across the toroid - a 50mm gap, and 10mm 'deep'
[23:34] <Laurenceb> that mor elike it
[23:35] <Laurenceb> anyway yeah one of those up near the top
[23:35] <Laurenceb> then a brushless motor with an adaptor to hold the bottom of the motor
[23:36] <Laurenceb> youd have to use some packing to fit the top of the rocket into the bearing unit
[23:36] <Laurenceb> - thatd be pushed out as the motor fired
[23:36] <Laurenceb> prob eaisest to mount everything inside some GRP tube
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[23:38] <Laurenceb> ignition would be fiddly, prob easiest to have a lipo cell fixed to the brushless motor - bottom of rocket adaptor
[23:38] <Laurenceb> so its spins with it
[23:43] <SpeedEvil> what gyro rpm are you considering
[23:45] Nick change: KingJ -> kingj
[23:48] <Laurenceb> a few hundered
[23:49] <SpeedEvil> oh - I was thinking much faster
[23:51] Nick change: kingj -> KingJ
[00:00] --- Sat Aug 8 2009