highaltitude.log.20080524

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[10:42] <jcoxon> morning edmoore
[10:42] <edmoore> hi jcoxon !
[10:42] <edmoore> how's it going?
[10:48] <jcoxon> good thanks
[10:48] <jcoxon> am attempting to add a CPAN module to my perl build on teh gumstix
[10:48] <jcoxon> horrible config files to sort out to get it to cross compile
[10:50] <edmoore> what's cpan?
[10:51] <edmoore> much better azziz
[10:51] <jcoxon> its very cool
[10:51] <jcoxon> you need a module for perl, you run cpan 'module' or something like that
[10:51] <jcoxon> it downloads and installs it
[10:51] <jcoxon> great apart from when working on an embedded system with out net access
[10:53] <edmoore> lol
[10:53] <edmoore> sounds about right
[10:53] <edmoore> life with macbook still good?
[10:53] <jcoxon> yup
[10:54] <jcoxon> can get quite hot sometimes
[10:54] <jcoxon> but tis all good
[10:54] <edmoore> Can't wait to fly badger! As soon as exams are over we'll test it in every way we can on the ground, then try and break it.
[10:54] <edmoore> Yeah, that's the one thing that annoys me muchly
[10:54] <edmoore> the heat
[10:54] <jcoxon> ooooh well my HAPS-1 nav system is nearly finished
[10:55] <jcoxon> fancy a joint flight
[10:55] <jcoxon> one of them will work i reckon
[10:55] <jcoxon> :-p
[10:55] <edmoore> oh yeah actually
[10:55] <edmoore> that'd be great
[10:56] <edmoore> fergus keeps talking about flying every week
[10:56] <edmoore> so this could be a good way of doing that a bit more feasably!
[10:56] <jcoxon> as in a flight a week?
[10:59] <edmoore> yeah
[10:59] <jcoxon> :-)
[11:00] <edmoore> work on stuff during the week, test it on the ground, fly it
[11:00] <edmoore> continue until bomb-proof (tm)
[11:00] <jcoxon> not sure i'll be able to come up everyweek :-)
[11:00] <edmoore> lol
[11:00] <edmoore> well it could get a bit routine
[11:00] <edmoore> but that's no bad thing
[11:01] <jcoxon> oh it would be great to be able launch a week
[11:01] <jcoxon> but costs + time
[11:02] <jcoxon> urgh this is beginning to drive me crazy
[11:05] <edmoore> what's that?
[11:05] <jcoxon> this module stuff
[11:05] Action: jcoxon heads over to the openembedded irc channel
[11:09] <edmoore> good call ;)
[11:19] <jcoxon> haha no response
[11:31] <edmoore> bbiab brunch!
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[16:28] <Hiena> Good evening!
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[19:02] <edmoore> Good eveing Hiena
[19:02] <edmoore> how's it going?
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[19:10] <edmoore> hi Laurw
[19:10] <Laurenceb> hi
[19:10] <edmoore> by which i mean Laurenceb
[19:10] <edmoore> how's it going?
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[19:10] <edmoore> forthcomign exams are strictly forbidden as a conversation topic
[19:11] <Laurenceb> ok thanx
[19:11] <Laurenceb> :P
[19:11] <Laurenceb> That sparkfun order got charged at customs :(
[19:11] <edmoore> it's at times like this I kind of prefer the american system
[19:11] <edmoore> which is a bit more constant asessment
[19:11] <Laurenceb> can I ask you for £5 extra for your board?
[19:11] <Laurenceb> sorry
[19:12] <edmoore> yeah of course
[19:12] <edmoore> no probs
[19:12] <Laurenceb> cool
[19:12] <Laurenceb> its £40 overall
[19:12] <edmoore> we have some MIT excahnge students over there atm who have been saying all year how easy it all is and you don't really get worked nearly as hard
[19:12] <edmoore> but no exam term comes along and they're crying blood and committing suicide
[19:12] <Laurenceb> in the us ?
[19:12] <edmoore> yeah
[19:13] <Laurenceb> I see
[19:13] <edmoore> I do think their way of doing it is better
[19:13] <Laurenceb> it does seem a bit odd over there, more like an extended 6th form
[19:14] <Laurenceb> how is the badger board progressing then?
[19:14] <Hiena> Guess, i'm kind of depressed. I found a new way to cooking a rocket candy...
[19:15] <Laurenceb> rocket candy ? sounds cool
[19:15] <Laurenceb> sugar and potassium permanganate ?
[19:15] <Hiena> Sugar and ammonium-nitrate.
[19:15] <Laurenceb> ah interesting
[19:16] <Hiena> But it's kind of hard, because the melting point of the sugar and the flashpoint aof the ammonium-nitrate is too close.
[19:16] <Laurenceb> hehe
[19:17] <Hiena> I had a several "burn-out" at the past, so i decided to choose a different burning material.
[19:18] <Hiena> Melted some stearin, and added the nitrate to it. The stearin melting point around 60 degree, so i have 120 degree safety zone.
[19:19] <edmoore> Laurenceb: it's more or less on hold till after exams
[19:19] <edmoore> tho I might do some with fergus tomorrow and watch the phoenix landings
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[19:19] <edmoore> it's just dull stuff like getting the usb working nicely
[19:20] <Hiena> I set the burner "just above the" melting point, but it's enough to crack and evaporate the chrystal water from the nitrate.
[19:20] <edmoore> it's a bit of a shock coding something like that when I'm not very experienced and used to just writing drivers for SPI of I2C
[19:20] <Hiena> Now waiting for the cooling of the first batch.
[19:20] <Laurenceb> hmmm
[19:21] <Laurenceb> yes usb looks pretty hard
[19:21] <Laurenceb> halfway through my last problem sheet ever :D
[19:21] <Hiena> edmoore, do you have code for the sdcard reading?
[19:21] <edmoore> Hiena: we have what we did a few weeks ago
[19:22] <edmoore> which we haven't touched since
[19:22] <edmoore> it still has some bugs
[19:22] <Hiena> Is it in C?
[19:22] <edmoore> but we want to get usb useful first as it'll be useful for debugging
[19:22] <edmoore> Hiena: yes
[19:22] <Laurenceb> Hiena: SD isnt *that* bad, theres lots of axamples out on the web
[19:22] <edmoore> FatFS is what ours is based on
[19:22] <Hiena> i'll dig for it.
[19:22] <edmoore> you just provide drivers for writing spi
[19:23] <edmoore> it all works... in theory. We have some gremlins
[19:23] <Laurenceb> I tried to run FatFS on AVR over christmas
[19:23] <edmoore> but we'll get there
[19:23] <Laurenceb> and failed miserably :(
[19:23] <Laurenceb> but its certainly possible, just need a bigger processor, then you dont have to optimise it like craxy
[19:24] <edmoore> yeah it's about 20k if mem serves
[19:24] <Laurenceb> I got it down to about 12KB, but the RAM was the problem
[19:24] <Laurenceb> is can work with 1K I'm told
[19:24] <Laurenceb> but I couldnt do it
[19:24] <Laurenceb> *it can
[19:25] <edmoore> it's probably not worth all the ffort
[19:25] <edmoore> there are slimer, less fully features libraries around
[19:25] <Laurenceb> my conclusion as well
[19:26] <edmoore> henry has just emailed about the rocket flight computer
[19:26] <edmoore> he's succumbed to the blackfin
[19:27] <edmoore> he's recording 24fps HD vid using it, which takes about 25% of the cpu, and everything else takes about another 1%
[19:27] <edmoore> but plenty of room for active guidance at some future point, basically
[19:28] <Hiena> Ehem...
[19:28] <edmoore> wha?
[19:29] <Laurenceb> nice
[19:29] <Laurenceb> what camera is he using?
[19:29] <Hiena> Just funny, how powerfull the blackfin core.
[19:29] <edmoore> yeah it's really quite a beast
[19:29] <Laurenceb> or is it VGA/HDMI capture ?
[19:29] <edmoore> takes about 150mA all up inc camera and gps
[19:29] <edmoore> it's a hel of a core
[19:29] <edmoore> Laurenceb: no direct interface to the camera
[19:29] <edmoore> not sure which one he's ysing
[19:30] <edmoore> similar to that 1.3MP one spark recently started selling
[19:30] <Laurenceb> I see
[19:30] <Laurenceb> guess HDMI wouldnt be too hard
[19:31] <Laurenceb> is he using a demo board?
[19:33] <edmoore> no, diy pcb
[19:33] <edmoore> 4-layer if he can get away with it, he tells me. 6 if not
[19:33] <Laurenceb> nice, its BGA isnt it?
[19:33] <edmoore> it's both
[19:34] <Laurenceb> ok
[19:34] <edmoore> but basically the rocket is incredibly demanding in terms of size and weight, so compactness is the design driver. soa custom board with bga parts
[19:34] <Laurenceb> sounds pretty insane
[19:34] <edmoore> sd card holders glued on top of the ram chips- that sort of thing
[19:34] <Laurenceb> will bga be ok with the sort of vibrations its going to experience?
[19:35] <edmoore> why shouldn't it be?
[19:35] <Laurenceb> say your pcb is vibrating
[19:35] <Laurenceb> e.g. its bending slightly
[19:36] <Laurenceb> theres going to be much more stress on BGA parts as opposed to surface mount
[19:40] <Laurenceb> and it may be prone to failure, especially if its BGA thats not been soldered too well
[19:40] <edmoore> oh it'll be x-rayed
[19:41] <edmoore> but I've not convinved it'd be that much more prone to failure
[19:41] <edmoore> and BGA is surface mount
[19:43] <Laurenceb> ok sorry
[19:43] <Laurenceb> "leaded packages"
[19:44] <edmoore> well remember it'll be smaller so whilst it's stiffer it wont be exposed to as much differential deflection
[19:44] <Laurenceb> sounds good, do you have an X-ray machine at CUED?
[19:44] <edmoore> but I mean the pcb isn't structural - it'll be well damped
[19:44] <edmoore> it should be ok
[19:45] <edmoore> yep
[19:45] <Laurenceb> nice stuff
[19:45] <Laurenceb> so have you decided on guidance technique yet?
[19:45] <edmoore> no, will save that till after martlet
[19:45] <Laurenceb> martlet?
[19:45] <Laurenceb> I thought this was martlet
[19:46] <edmoore> martlet will be flying with only passive guidance
[19:46] <Laurenceb> from a balloon?
[19:47] <edmoore> yep
[19:47] <Laurenceb> ok.... not sure what will happen
[19:47] <Laurenceb> :P
[19:48] <edmoore> it'll fly up!
[19:48] <Laurenceb> maybe
[19:48] <Laurenceb> 50% chance
[19:49] <edmoore> well are success rate probability is based on several months of sims and iteration. So well go with that rather than the one derived from your arse
[19:49] <Laurenceb> hehe
[19:50] <edmoore> it of course could go very wrong
[19:50] <Laurenceb> you have sim code? how sophisticated?
[19:50] <edmoore> but there's still anough pressure up there to make it fly safely
[19:50] <edmoore> i.e. it has the same chance of flying straight as a standard ground-launch hpr
[19:51] <Laurenceb> hmm
[19:51] <Laurenceb> it has to accellerate first
[19:51] <Laurenceb> guess its all a fine balance... might work
[19:51] <edmoore> Laurence if we're going to have a basic physics conversation then i'm going to go
[19:51] <Laurenceb> :P
[19:51] <Laurenceb> so Henry is building a camera for it?
[19:52] <edmoore> Iain came top of his year and is a thermodynamics specialist currently in the fourth year. I trust his sums, and his ability to stick error bounds on them
[19:52] <edmoore> it'll be doing a good proportion of mac by the time it leaves the (very long) launch rail
[19:52] <edmoore> it'll have about twice the dynamic pressure that a typical HPR rocket have when it leaves a launch rail at ears
[19:53] <Laurenceb> ok, sounds good
[19:53] <edmoore> Henry is doing rocket flight computer yeah
[19:53] <Laurenceb> how long is the launch rail?
[19:53] <edmoore> 6m
[19:53] <edmoore> rocket is 1m
[19:53] <edmoore> well, 1.5
[19:53] <Laurenceb> hehe crazy
[19:54] <edmoore> it's a big old truss basically
[19:54] <Laurenceb> as long as it doesnt hit the balloon
[19:55] <edmoore> ha, well...
[19:55] <edmoore> it will
[19:55] <Laurenceb> lol
[19:56] <edmoore> it's the easiest way to deal with the balloon problem
[19:57] <Laurenceb> the impulse from the balloon will be small
[19:57] <edmoore> it's only 5 micron polythene
[19:58] <Laurenceb> what altitude are you predicting?
[19:58] <Laurenceb> for rocket apogee
[19:58] <edmoore> what's a nice round number?
[19:59] <Laurenceb> 100km
[19:59] <Laurenceb> but not for martlet surely?
[19:59] <edmoore> yup
[20:00] <Laurenceb> that would be sweet
[20:00] <Laurenceb> sounds crazily easy
[20:00] <edmoore> I mean we've tried to find fault with the numbers, but basically with a big enough rocket it just seems to work out that way
[20:00] <Laurenceb> sure
[20:00] <Laurenceb> hmmm you're really lacking a good radio link ?
[20:01] <edmoore> well the 10mW should be fine I'd have thought
[20:02] <Laurenceb> hmm guess so... for a project like this you want streaming video and everything
[20:02] <Laurenceb> I was looking at an optical data link, you could get 10Mbps with leds
[20:02] <edmoore> nah, it's all going on an sd card
[20:02] <Laurenceb> true
[20:03] <Laurenceb> youd need a small scope and APD
[20:04] <edmoore> don't want to be faffing with scaopes
[20:04] <edmoore> rob is currently building a tracking pan and tilt for the yagi
[20:04] <edmoore> that'll be useful
[20:04] <Laurenceb> if it was one of those small reflectors with automatic pointing (about £1000) it should be possible to add a webcam and automate the tracking
[20:05] <Laurenceb> mad but I like it :D
[20:05] <edmoore> we were talking about that at james' last launch
[20:05] <edmoore> doug's spotting scope was tremendously good value
[20:05] <edmoore> a webcam on one of them should easily be able to track it
[20:05] <Laurenceb> theoretically with a few leds you could get about 100Mbps over 1000Km
[20:06] <Laurenceb> but leds arent that fast
[20:06] <edmoore> then steve suggested modifying a microwave transformer to act as a ranging radar
[20:06] <Laurenceb> an APD will go up to 1Gbps or more
[20:06] <Laurenceb> ok
[20:07] <edmoore> but that would probably hurt to stand infront of
[20:07] <edmoore> or within any distance of
[20:07] <Laurenceb> http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6277543
[20:09] <edmoore> nice
[20:12] <Laurenceb> stick one of those on your scope and your sorted :P
[20:12] <Laurenceb> although youd need good optics and aiming
[20:13] <Laurenceb> if you take them up to 600V or so you can do single photon detection
[20:14] <edmoore> sounds a bit unreliable
[20:15] <Laurenceb> well each databit would be thousands of photons
[20:15] <edmoore> what is the advantage of using that bit of the spectrum, for a given total transmitter power?
[20:16] <edmoore> as opposed to the radio end
[20:16] <Laurenceb> its unregulated
[20:16] <edmoore> and what if there's a cloud
[20:16] <edmoore> or it points away
[20:16] <Laurenceb> well youd have an led cluster
[20:17] <Laurenceb> but yes its no good it there is a cloud
[20:17] <edmoore> it seems a bit of a physics solution rather than an engineering one, if you don't mind me saying. it probably 'would' work but it doesn't stop it being a pain in the arse to actually do
[20:18] <Laurenceb> :P
[20:18] <edmoore> I'm not saying that cos you're a physicist and I'm an engineer - afterall everything they teach engineers is theory anyway
[20:18] <edmoore> but KISS, basically
[20:19] <edmoore> right, eurovision time
[20:19] <edmoore> bbl
[20:19] <Laurenceb> cya
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[21:56] <Laurenceb> whats that edmoore? eurotrash ?
[21:58] <akawaka> eurotrash the tv show?
[21:58] <Laurenceb> I'm joking
[21:58] <Laurenceb> what you have it over there?
[21:59] <akawaka> i lived in ireland until i was 20
[21:59] <Laurenceb> ah
[21:59] <Laurenceb> ireland is a pretty cool place
[22:00] <Laurenceb> so less crowded than the UK
[22:01] <akawaka> i guess, the countryside is the same really
[22:01] <akawaka> cities are smaller
[22:01] <akawaka> but yeah, its cooler than the uk:)
[22:02] <Laurenceb> I like the education system and things
[22:02] <Laurenceb> also no council tax
[22:16] <Laurenceb> yep I'll probably emigrate there soon :P
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[00:00] --- Sun May 25 2008