highaltitude.log.20090203

[00:00] <hallam> Hi edmoore
[00:00] <hallam> how's the cold?
[00:00] <edmoore> hi
[00:00] <edmoore> still here
[00:00] <edmoore> annoying
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[00:00] <hallam> sorry to hear it
[00:00] <edmoore> just trying to finish an examples paper then will get as much sleep as I can
[00:01] <hallam> blackfin is running GPS tracker code
[00:01] <edmoore> really want a clear nose in time for this wine society dinner on sat. payed decent money for a ticket, so i want to have a sense of taste!
[00:01] <edmoore> ok that's *awesome*
[00:01] <hallam> not finished yet by any means
[00:01] <hallam> but the speed works out fine
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[00:07] <hallam> how peculiar
[00:07] <hallam> blackfin agrees with laptop for first 1000ms of data, then diverges
[00:08] <Laurenceb> odd
[00:08] <Laurenceb> is in it loses lock?
[00:10] <hallam> yeah
[00:10] <hallam> but the first 1000ms seem to be identical
[00:10] Action: hallam investigates
[00:10] Action: Laurenceb goes off to make some coffeee
[00:10] <Laurenceb> I've still got a headache... its not good
[00:12] <hallam> oh, pebkac
[00:12] <hallam> you should probably not drink coffee then?
[00:15] <Laurenceb> maybe not
[00:15] <hallam> sweeeet
[00:15] <Laurenceb> I got attacked by about 4 chavs earlier
[00:15] <hallam> seriously?
[00:15] <Laurenceb> spent the morning in A&E
[00:15] <hallam> god damn
[00:15] <Laurenceb> yeah they were throwing stuff at cars
[00:16] <hallam> that really sucks Laurence
[00:16] <Laurenceb> I told them to stop and they went crazy
[00:16] <hallam> christ
[00:16] <Laurenceb> yeah got kicked several times in the head
[00:16] <hallam> did you call the police?
[00:16] <Laurenceb> yeah, they said they'll look at cctv
[00:16] <hallam> :/
[00:17] <hallam> hope you're not permanently damaged
[00:17] <Laurenceb> black eye and some cuts
[00:17] <Laurenceb> thought I'd get checked out as my vision wnet funny
[00:17] <hallam> if anyone asks what happened you should just say "pirates."
[00:18] <Laurenceb> lol
[00:18] <hallam> fergusnoble, edmoore: Actual tracking loop running on actual data now, with identical results to the PC
[00:18] <Laurenceb> yeah i dont look too good atm
[00:18] <edmoore> awesome
[00:18] <Laurenceb> nice
[00:18] <fergusnoble> hallam: cool, with straight c?
[00:18] <hallam> yeah
[00:19] <fergusnoble> cool
[00:19] <Laurenceb> gcc?
[00:19] <hallam> yes
[00:19] <hallam> now I want to merge the codebase so it's actually compiling from the same source, just with a #define for blackfin or pc
[00:19] <Laurenceb> would be neat
[00:19] <Laurenceb> then you could have some inline asm
[00:20] <hallam> yeah I've already written the asm, just haven't actually assembled it yet
[00:20] <hallam> atm it's about 40MHz/channel minus logging overhead
[00:20] <hallam> with asm it should be around 6
[00:20] <Laurenceb> slower than pc?
[00:21] <Laurenceb> guess thats the superscalar stuff ?
[00:21] <hallam> PC does about 30
[00:21] <Laurenceb> ok, I though you said 14 before
[00:21] <hallam> it'll probably be the floating point stuff in the loop filters, or maybe the logging
[00:21] <edmoore> UML is so boring. shouldn't have bothered with this module
[00:21] <hallam> oh god yes
[00:22] <hallam> it's catatonic
[00:22] <edmoore> 'draw a class diagram for the following code'. no, how about you fuck off.
[00:22] <hallam> PC does 30 seconds of data in 0.4 seconds at 2.2GHz, that's 30MHz/ channel, right?
[00:22] <edmoore> I don't think that's the answer they put in the crib though
[00:23] <edmoore> apolologies for my launguage to all new people
[00:23] <Laurenceb> yeah
[00:23] <Laurenceb> I am highly offended
[00:23] <Laurenceb> I must complain about this
[00:24] <edmoore> you are not new
[00:24] <Laurenceb> hallam: did you get position working properly with the matlab code?
[00:25] <hallam> define properly
[00:25] <hallam> I got it to what I think is probably better than 20m in the general case
[00:26] <Laurenceb> nice
[00:26] <hallam> figure I need iono to do better than that
[00:26] <hallam> I do want to put a better nav filter on than just least squares
[00:26] <hallam> but it's not a priority
[00:26] <Laurenceb> were you getting continuous lines?
[00:26] <Laurenceb> yeah, i dont like least squares
[00:27] <Laurenceb> as in all points scattered within 20cm of some line that drifts about in 3D ?
[00:27] <hallam> I think so
[00:27] <hallam> haven't looked into the time distribution too much, but the plot looks like that was the case
[00:28] <hallam> might not have been as close as 20cm
[00:28] <Laurenceb> yeah, depends on the dll filter
[00:28] <Laurenceb> I'm not quite sure what causes the drift
[00:29] <Laurenceb> most of it is the dll settling in, but theres other drifts of a few m over timescales of around 10 seconds
[00:29] <Laurenceb> guess its ionospheric fluctuations
[00:37] <Laurenceb> my supervisor sends emails in leet
[00:37] <Laurenceb> its just not right
[00:37] <hallam> fire him
[00:38] <Laurenceb> "omfg w3 got pwned by snow"
[00:48] <Laurenceb> whats with the latest post on hackaday
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[01:04] <SpeedEvil> http://www.yr.no/place/United_Kingdom/Scotland/Glenrothes/hour_by_hour.html - insane the best weather forcast I've found is from norway.
[01:08] <Laurenceb> yeah met office sucks
[01:09] <Laurenceb> <-- current state ofhttp://pastebin.com/m4fcc79a1 my MFSK16 coder
[01:09] <Laurenceb> http://pastebin.com/m4fcc79a1
[01:09] <Laurenceb> oops
[01:09] <Laurenceb> hopefully it'll be ready soon
[01:12] <Laurenceb> be interesting to see if the performance lives up to the claimed
[01:14] <Laurenceb> is <<(n-6) valid in n<6 ?
[01:16] <shellevil> Actually - the met office data is quite good - not that expensive and nice and high resolution.
[01:16] <shellevil> But.
[01:16] <shellevil> With a minimum purchase of 5000 licenses :/
[01:18] <Laurenceb> daft
[01:19] <shellevil> It makes sense - in 1988.
[01:19] <Laurenceb> I really dont get the labout parties obsesion with privatising everything
[01:19] <shellevil> In 2008 - not so much
[01:19] <Laurenceb> even in the US they have NOAA
[01:19] <shellevil> 'money now++'
[01:20] <shellevil> OS annoys me too.
[01:20] <shellevil> IIRC the licensing fees paid by government departments to OS is about 1/2 its total commercial income.
[01:21] <Laurenceb> yeah, most of the data was collected by tax funded work
[01:21] <shellevil> That too.
[01:21] <Laurenceb> it should be free
[01:23] <shellevil> I don't know if I've gone on about this before here - but the lack of a sovereign wealth fund from oil moneys - and Thatcher is as much to blame as anyone - is another bugbear.
[01:24] <shellevil> Also the lack of major investment in nuclear, which means that massive amounts of money flow out of the economy to buy oil, meaning we have to work harder, not just local jobs in power stations.
[01:25] Action: shellevil votes for 20* more nuclear, and switching _all_ fixed loads to electricity.
[01:26] <Laurenceb> he
[01:27] <Laurenceb> dounreay was a massive waste of money
[01:27] <Laurenceb> I mean it has been
[01:27] <Laurenceb> it wouldnt have been if it had been used effectively
[01:28] <shellevil> I like some of the newer designs that are coming outl
[01:28] <shellevil> http://ap1000.westinghousenuclear.com/index.html
[01:28] <shellevil> rely on gravity as much as possible.
[01:28] <shellevil> Simplify, simplify, simplify.
[01:35] Action: Laurenceb likes the greenwashing
[01:36] <natrium42> lol, wtf --> http://www.theglobeandmail.com/servlet/story/RTGAM.20090202.wcollegeradio0202/CommentStory/Technology/
[01:36] <natrium42> university students contact ISS get into national paper, lul
[01:36] <shellevil> greenwash in what sense?
[01:37] <shellevil> nat: yes, because no student ever has made a radio.
[01:37] Action: shellevil sighs.
[01:38] <Laurenceb> the background image
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[01:38] <natrium42> shellevil: srsly, afaik they didn't even make it from scratch
[01:39] <shellevil> You mean it's got some sky and a tree?
[01:39] <fergusnoble> and they are in their 20s and 30s, hardly young students
[01:39] <Laurenceb> the leaf image
[01:40] <shellevil> Damn.
[01:40] <shellevil> What does that remind me of.
[01:40] <shellevil> Aha!
[01:40] <shellevil> http://upload.wikimedia.org/wikipedia/commons/thumb/b/bb/City.of.london.st.pauls.arp.500pix.jpg/250px-City.of.london.st.pauls.arp.500pix.jpg
[01:40] <natrium42> "he truth is that these students didn't build their own radio; they used an Icom Ic-V8000 that they bought at Radioworld, and a Yaesu G-5500 rotator. Basically, they put together a station from commercially available parts and used that to make the contact. (See their blog at http://www.operationfirstcontact.com/blog/ for verification of these facts.)"
[01:40] <fergusnoble> natrium42: perimeter want an 80% uni mark, do you know what that would be in UK money?
[01:40] <natrium42> looool
[01:41] <natrium42> fergusnoble: you can just calculate it
[01:41] <shellevil> That's damn near identical in aspect ratio.
[01:41] <natrium42> yourmark/topmark * 100
[01:41] <Laurenceb> haha
[01:41] <shellevil> I suppose you could actually put a copy of the dome and tower over the main reactor, with very little effort.
[01:42] <fergusnoble> natrium42: well 70% in an exam paper is a 1st class which is very difficult to get, nobody ever averages 80%
[01:42] <fergusnoble> nobody
[01:42] <shellevil> Who could object then? I mean - the real objection has been that they are ugly :)
[01:42] <fergusnoble> i was hoping they arent equivalent otherwise i have no chance :)
[01:42] <Laurenceb> fergusnoble: 72% here
[01:43] <fergusnoble> Laurenceb: well done
[01:43] <natrium42> hmm
[01:43] <Laurenceb> :P
[01:43] <natrium42> could always email and ask...
[01:43] <natrium42> or call
[01:43] <Laurenceb> I think some people got as high as 80
[01:43] <Laurenceb> I was 38th out of about 140
[01:44] <fergusnoble> ok, so maybe a top few do... i hope they arent to fixed about that
[01:44] <Laurenceb> yeah I dont know anyone who got above 76%
[01:45] <natrium42> so your university doesn't bellcurve?
[01:45] <Laurenceb> oxford does
[01:45] <Laurenceb> but its limited in shift
[01:45] <Laurenceb> very odd
[01:45] <fergusnoble> it does but the mean is something like 55%
[01:46] <Laurenceb> its also based on about 10 years results
[01:46] <fergusnoble> hehe, i guess it should be 50%
[01:46] <fergusnoble> and the variance is quite small
[01:46] <Laurenceb> they released the code under the GPL :P
[01:50] <Laurenceb> I'd get the code but its only on the internal network
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[11:53] <rjharrison> Is everyone playing in the snow?
[11:53] <gordonjcp> no snow here
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[12:12] <SpeedEvil> It's all melted here.
[12:12] <SpeedEvil> Well - I lie.
[12:12] <SpeedEvil> there are scattered bits.
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[12:14] <SpeedEvil> -4 scheduled for tonight - but rain before then
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[13:30] <Laurenceb> hello
[13:30] <shellevil> Hello!
[13:31] Action: Laurenceb has a massive black eye
[13:31] <shellevil> Have the police tracked down your assailants, and consigned them to a forced labour camp where they break rocks?
[13:31] <shellevil> :(
[13:32] Action: shellevil ponders the camp next door where they have to glue the rocks back together into their original shape.
[13:33] <Laurenceb> nope
[13:33] <Laurenceb> but they got back in touch so maybe something will happen
[13:34] <rjharrison> Laurenceb: what happend
[13:34] <rjharrison> is it in the logs
[13:34] <Laurenceb> yeah
[13:34] <Laurenceb> I got attacked by some chavs
[13:34] <rjharrison> Wankers
[13:35] <rjharrison> Excuse my French
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[13:36] <hallam> hey
[13:36] <hallam> how's the face?
[13:37] <hallam> Anybody know anything about linker scripts?
[13:42] <rjharrison> Launching this w/e doesn't look likely
[13:42] <rjharrison> :(
[13:45] Action: shellevil ponders assymetric balloons.
[13:45] <shellevil> If you could get some sort of aerodynamic stuff going on, steering to 1/2 the ascent rate seems plausible.
[13:45] <shellevil> though that
[13:46] <shellevil> s not really much
[13:59] <shellevil> Can't think of a way to do it without - forex - a rigid structure with seperate air and He bladders that vents air on way up
[14:42] <rjharrison> how embarrasing
[14:42] <rjharrison> I was going to suggest an inflated structure but without a valve it would pop
[14:43] <rjharrison> aah I see that is what you mena
[14:43] <rjharrison> Ignore me
[14:43] <rjharrison> I'm having a bad day :)
[14:43] <Laurenceb> you can do inflated structures
[14:43] <SpeedEvil> You could in principle glue up a latex balloon
[14:43] <Laurenceb> then vent them as you ascend
[14:44] <SpeedEvil> with latex glue.
[14:44] <SpeedEvil> so it's a non-sphere
[14:44] <SpeedEvil> something like a bananna
[14:44] <Laurenceb> of a latex balloon inside an aerodynam,ic body
[14:46] <SpeedEvil> Oh - have I mentioned I found a source for micro HAB attempts?
[14:46] <SpeedEvil> http://www.dealextreme.com/details.dx/sku.18886
[14:47] <Laurenceb> grrr
[14:52] <hallam> SpeedEvil: did you hear about the giant space condom that we built to assist the rocket layup?
[14:52] <SpeedEvil> ?
[14:52] <SpeedEvil> Hmm. Servos for 3 quid.
[14:52] <hallam> building a rocket out of carbon fibre
[14:52] <SpeedEvil> Yes, I know. A release layer?
[14:52] <hallam> got an external mold
[14:52] <Laurenceb> release agent eh
[14:52] <SpeedEvil> no bleed layer?
[14:53] <hallam> well you coat the mold in freekote
[14:53] <Laurenceb> guess no condom cleaning was needed
[14:53] <hallam> then lay up the prepreg inside it
[14:53] <SpeedEvil> Ah. prepreg.
[14:53] <hallam> then put space condom inside the prepreg
[14:53] <SpeedEvil> That reduces the need for bleed layer I spose.
[14:53] <hallam> close up the mold, put it in an autoclave, inflate the condom to ~6 bar
[14:53] Action: SpeedEvil wishes prepreg was easy to get.
[14:53] <Laurenceb> whats the mold made from?
[14:54] <hallam> machined out of solid Al
[14:54] <hallam> it's hefty
[14:54] Action: hallam admits to not knowing what a bleed layer is
[14:54] <SpeedEvil> Overkill!
[14:54] <Laurenceb> cnc milled?
[14:54] <SpeedEvil> Bleed layer is a way of removing excess resin
[14:54] <SpeedEvil> in the above situation
[14:54] <hallam> somewhat, but it does have to take the pressure, and it's quite adaptable
[14:54] <hallam> okay
[14:55] <hallam> a sacrificial layer on the outside that absorbs resin?
[14:55] <Laurenceb> what diameter rocket?
[14:55] <SpeedEvil> you put a layer of perforated plastic over the prepreg, then a layer of absorbant, then the condom.
[14:55] <hallam> 58mm
[14:55] <Laurenceb> and what part of the rocket?
[14:55] <hallam> all of it, except the fins
[14:55] <Laurenceb> ok, thought you were going for 80mm ?
[14:55] <hallam> no
[14:55] <Laurenceb> or is this a first test?
[14:55] <SpeedEvil> The condom pushes the resin through the perforated plastic layer, and into the bleed layer.
[14:55] <hallam> plan atm is 58mm all the way
[14:55] <Laurenceb> oh wow ok
[14:55] <Laurenceb> 2 stage?
[14:56] <SpeedEvil> You then remove it, and peel off the plastic film, taking away the excess resin absorbed into the film.
[14:56] <hallam> no
[14:56] <Laurenceb> ok
[14:56] <Laurenceb> what altitude?
[14:56] <hallam> makes sense
[14:56] <SpeedEvil> To reduce weight, and maybe increase strength.
[14:56] <hallam> 100 - 120km
[14:56] <SpeedEvil> (by some measures)
[14:56] <Laurenceb> ok, I diidnt think that was possible
[14:56] <SpeedEvil> This is a balloon launch?
[14:56] <Laurenceb> unguided?
[14:56] <hallam> yes, yes
[14:57] <SpeedEvil> Spun?
[14:57] Action: SpeedEvil thinks he's asked that before.
[14:57] <SpeedEvil> Solid?
[14:57] <hallam> I think you can juuust squeak over 100km from 30km launch with a stock L730, but we're making our own cases, which gives quite a bit of margin
[14:57] <hallam> solid, probably unspun
[14:58] <SpeedEvil> you're just going straight up?
[14:59] <SpeedEvil> servo + graphite tab is quite easy for minimal guidance.
[14:59] <SpeedEvil> Though you need some tests.
[14:59] <Laurenceb> hallam: cases?
[15:00] <hallam> atm we believe fins weigh less than servos and vanes
[15:00] Action: Laurenceb doesnt know much about stock motors
[15:00] <SpeedEvil> Course they do
[15:00] <SpeedEvil> hallam: also useless outside the air.
[15:00] <hallam> even the big fins you have to have for high altitude launch
[15:00] <SpeedEvil> hallam: fair enough
[15:00] <Laurenceb> edmoore said a 5m rail
[15:01] <hallam> I don't know too much about the rail plans
[15:01] <Laurenceb> an IMU is perfectly possible
[15:01] <Laurenceb> but it would bve a lot more work
[15:01] <hallam> Laurenceb: the stock motors consist of an Al pressure vessel that you insert "reloads" into
[15:01] <Laurenceb> right, solid?
[15:01] <hallam> yeah
[15:01] <hallam> reusable
[15:01] <SpeedEvil> IMU is lot more work - but just a preset launch angle vs the magnetic field is rather easier.
[15:02] <Laurenceb> hmm, so your using CF with the existing nozzel?
[15:02] <Laurenceb> SpeedEvil: the maths is very doable
[15:02] <hallam> the Al is both heavy because it's Al, and heavy because it's overspecced to deal with being abused by amateur rocket people and then fired in close proximity to observers
[15:02] <SpeedEvil> You are sure of all the annoying legalities?
[15:02] <Laurenceb> hallam: what happens if the fuel burns through unevenly and the CF is exposed to high temp?
[15:03] <hallam> so yeah, CF, maybe the existing nozzle, maybe a new one because you can get about 5-10% more total impulse with a higher expansion ratio at altitude
[15:03] <Laurenceb> yeah good point
[15:03] <SpeedEvil> CF is quitte resistant.
[15:03] <hallam> SpeedEvil: not totally sure, but we're going to use the stock reloads, and believe it's okay
[15:03] <hallam> there'll be a thermal protection layer
[15:03] <SpeedEvil> But if you want to reuse, you'd want a thermal layer
[15:03] <Laurenceb> ah cool
[15:03] <Laurenceb> firbreglass?
[15:03] <Laurenceb> asbestos :P
[15:03] <SpeedEvil> IIRC soome polymer is commonly used.
[15:03] <hallam> Iain's found some lightweight ceramic stuff
[15:04] <hallam> I was just going to go with butcher paper but I guess he's done his research
[15:04] <Laurenceb> aka asbestos
[15:04] <hallam> UKRA wouldn't cover it for their launches but that doesn't make it illegal
[15:04] <Laurenceb> ceramic as in fluffy stuff?
[15:04] <hallam> don't know
[15:04] <Laurenceb> k
[15:05] <Laurenceb> then a graphite nozzel?
[15:05] <hallam> prolly
[15:05] Action: SpeedEvil votes for platinum-iridium nozzle.
[15:05] <Laurenceb> hehe
[15:05] <hallam> we might just use the stock nozzles to save dev time
[15:05] <Laurenceb> what about re-entery heating?
[15:06] <hallam> not a big deal
[15:06] <SpeedEvil> http://www.nakka-rocketry.net/ablatex1.html may be interesting,.
[15:06] <hallam> paint might get scorched
[15:06] <SpeedEvil> Err
[15:06] <hallam> except there won't be any paint because it's a waste of mass
[15:06] <SpeedEvil> I mean http://www.nakka-rocketry.net/therm.html
[15:06] <hallam> thanks, that's a good site
[15:07] <Laurenceb> hallam: so you have a bulkhead at the top?
[15:07] <Laurenceb> then the tronics sits on top
[15:07] <hallam> yeah, don't ask about recovery, it's not finalised yet
[15:08] <Laurenceb> hehe
[15:08] <Laurenceb> parafoil
[15:08] <Laurenceb> the annoying thing with prarfoils is they are too big
[15:08] <Laurenceb> you cant get <1.5m on ebay
[15:09] <hallam> total recovery system mass has to be < 100g
[15:09] <Laurenceb> yeah
[15:09] <Laurenceb> have to just be a chute
[15:09] <hallam> try finding one of that mass that can open at mach 3
[15:10] <Laurenceb> well two chutes
[15:10] <hallam> and still give a tolerable sea level desc rate
[15:10] <hallam> two = more to go wrong, more mass
[15:10] <Laurenceb> surely its not going that fast
[15:10] <Laurenceb> I'd have though a few hundered
[15:10] <hallam> M=4.4 at burnout, similar on reentry
[15:10] <Laurenceb> only open once its down to a few Km surely
[15:11] <hallam> still >2
[15:11] <Laurenceb> wut
[15:11] <Laurenceb> as its in stable flight?
[15:11] <hallam> by the time M gets low enough, Q is too high to open a chute
[15:11] <Laurenceb> i.e. nose first
[15:11] <Laurenceb> oh ok
[15:11] <hallam> we
[15:12] <hallam> we'll work something out
[15:12] <hallam> have some ideas
[15:12] <Laurenceb> cant you destabilise it?
[15:12] <Laurenceb> e.g. fins break off
[15:12] <Laurenceb> so its flying sideways
[15:13] <SpeedEvil> Controllable fins, fly it into a net.
[15:13] <Laurenceb> haha
[15:15] <Laurenceb> independant manoverable nose unit
[15:16] <Laurenceb> I'd wait till you get low
[15:16] <Laurenceb> then theres less drift due to wind
[15:17] <SpeedEvil> I wonder about canting a couple of fins 45 degrees on the long axis
[15:17] <Laurenceb> yeah
[15:17] <SpeedEvil> (on reentry)
[15:17] <Laurenceb> but if you deploy a large chute just after apogee... what happens
[15:17] <SpeedEvil> actually - that'll make parachute deployment really annoying
[15:18] <Laurenceb> when the dynamic pressure is just enough to open the chute...
[15:18] <SpeedEvil> Or a semi-rigid chute even.
[15:18] <Laurenceb> I guess its going to get hot
[15:20] <Laurenceb> not sure how hot
[15:20] <SpeedEvil> Roton!
[15:20] <SpeedEvil> http://www.dealextreme.com/details.dx/sku.18875
[15:20] <Laurenceb> lol
[15:22] <Laurenceb> I wonder if you could stall a rocket
[15:22] <SpeedEvil> Aerodynamically, yes
[15:22] <Laurenceb> come down ballistically to a few km
[15:22] <Laurenceb> then steer the fins to get sideways flight
[15:23] <Laurenceb> then stall it and deploy the chute
[15:23] <Laurenceb> large fins should make that easier
[15:24] <SpeedEvil> It's stalled - in that sense - once you get a few degrees out of the wind direction
[15:24] <SpeedEvil> AIUI
[15:24] <Laurenceb> well you''l be going almost straight down at a few hundered mph
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[15:24] <SpeedEvil> Damn.
[15:25] <Laurenceb> if you can turn it round so thats horizontal with some body andgle of attack
[15:25] <SpeedEvil> On one of these DVDs around here, I've got numbers for drag on rods at transonic speeds
[15:25] <Laurenceb> you may be able to sustain a few second horizontal flight
[15:25] <SpeedEvil> angle of attack is only applicable to the fins
[15:25] <Laurenceb> then if you can make a transition to going up slightly, you should be able to stall
[15:26] <Laurenceb> then start falling again
[15:26] <SpeedEvil> Oh yes.
[15:26] <SpeedEvil> http://naca.central.cranfield.ac.uk/
[15:26] <SpeedEvil> _vital_ site for anyone playing with this sort of shit. IMO.
[15:27] <Laurenceb> neat
[15:27] <SpeedEvil> http://naca.central.cranfield.ac.uk/report.php?NID=6206
[15:27] <SpeedEvil> no, that's the wrong one
[15:28] <Laurenceb> well I was thincking of doing this at a few hundered mph
[15:28] <Laurenceb> but its still tricky for 100 grams
[15:28] <SpeedEvil> http://naca.central.cranfield.ac.uk/report.php?NID=5530 looks more relevant
[15:29] <Laurenceb> thanks
[15:29] <Laurenceb> maybe a pyro device for causing the nose to bend round
[15:29] <Laurenceb> no...
[15:29] <Laurenceb> it wants to be quite subtle
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[15:30] <Laurenceb> a heavy duty servo would be tooheavy
[15:30] <SpeedEvil> Spring/catch pulled off with servo
[15:30] <hallam> http://uploads.mibbit.com/up/P8tPajU7.png
[15:30] <Laurenceb> better with pyro for struff like that
[15:31] <SpeedEvil> The NASA website used to be awesome.
[15:31] <Laurenceb> hallam cool
[15:31] <SpeedEvil> But they pulled a lot of stuff post 9/11
[15:31] <Laurenceb> yeah 220mph looks sensible
[15:31] <SpeedEvil> This assumes it's going nose-first I assume?
[15:31] <Laurenceb> theres got to be enough momentum there to stall it
[15:32] <Laurenceb> but its a very tricky manover to pull off
[15:32] <hallam> actuated fins are really annoying / heavy to build
[15:32] <Laurenceb> yeah
[15:32] <SpeedEvil> hallam: no they're not!
[15:32] <Laurenceb> I was thinking some nose squewing
[15:33] <SpeedEvil> hallam: only if you don't want them to fall off with flutter loads.
[15:33] <Laurenceb> with [pyros
[15:33] <Laurenceb> SpeedEvil: 100grams
[15:33] <SpeedEvil> Hmm.
[15:33] <SpeedEvil> Hot-melt glued fins.
[15:33] <Laurenceb> oh god
[15:33] <SpeedEvil> Teeny servo.
[15:33] <hallam> heh
[15:33] <SpeedEvil> heat pulse from motor frees them.
[15:33] <Laurenceb> you could squew the nose over with pyros for a few tens iof grams
[15:33] <SpeedEvil> servo moves them.
[15:34] <SpeedEvil> they then freeze again in the lower atmosphere
[15:34] <Laurenceb> but thats a try it once and hope it works technique
[15:34] <SpeedEvil> Lots of this stuff is easy on your 50th test.
[15:34] <Laurenceb> if the body is spinning your screwed
[15:35] Action: hallam goes back to blackfin
[15:35] <Laurenceb> well maybe not...
[15:35] <Laurenceb> but it would probably end up spinning out of control when you try the stall manover
[15:38] <Laurenceb> I would say a heat resistant chute at about mac 3.3
[15:38] <Laurenceb> but its going to lead to loads of drift on the way down
[15:39] <Laurenceb> you're going to be exceeding mac 3.5 probably
[15:42] <Laurenceb> ptfe firbeglass maybe
[15:46] <Laurenceb> hmm I dont think the stall idea will work too well
[15:47] <Laurenceb> the CofG is too far towards the front of the rocket
[15:49] <Laurenceb> unless the fins suddenly move up the the body center
[15:51] <SpeedEvil> Yeah - you need body lift to stall
[15:51] <SpeedEvil> or rather - some other lift source than the fins
[15:52] <Laurenceb> annoying
[15:52] <SpeedEvil> And to be able to stall, you need to be flying.
[15:52] <Laurenceb> yeah
[15:52] <SpeedEvil> Which means that you're unstalled.
[15:52] <Laurenceb> only for a couple of seconds
[15:52] <SpeedEvil> Which means that you're flying with the nose within a few degrees of the wind
[15:52] <Laurenceb> yeah
[15:53] <SpeedEvil> Which also means that you need to support the entire weight on the body lift.
[15:53] <Laurenceb> basically you want to trace out a u shape
[15:53] <Laurenceb> thats very possible
[15:53] <Laurenceb> you are at terminal velocity to start with
[15:54] <Laurenceb> terminal v for forward flight
[15:54] <Laurenceb> or balliastic fall even
[15:54] <SpeedEvil> Big question of course is control authority to avoid having to greatly increase structural strength for the cumulo-granitus portion of the flight.
[15:55] <SpeedEvil> You're falling at mach 1 to 5Km, you don't have many seconds to cancel vertical velocity.
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[15:57] <mc-> Hi Laurenceb, hope you're ok. Were you attacked in Guildford?
[16:00] <Laurenceb> yeah, I'm ok now thanks
[16:01] <Laurenceb> I've thought of one idea - a line of nylon kit line with lots of small polythene chutes on
[16:01] <Laurenceb> unroll it
[16:09] <Laurenceb> hallam: what do you think?
[16:12] <Laurenceb> guess its overcomplicated
[16:21] <Laurenceb> guess you could have an ejectable nosecopne, then a ring of individual chutes of differing size
[16:24] <hallam> hey
[16:24] <hallam> main issue is that chutes behave weirdly at M>1, even if Q is low
[16:25] <hallam> they can tear themselves apart from flutter
[16:25] <Laurenceb> sure
[16:25] <Laurenceb> deploy near the ground
[16:25] <Laurenceb> nose off at say 6Km
[16:25] <Laurenceb> then fire off the min chutes one at a timne
[16:25] <hallam> so it's pretty much a streamer that pulls a chute out?
[16:26] <Laurenceb> hmm
[16:26] <Laurenceb> I was thinking independant min chutes
[16:26] <Laurenceb> more reliable
[16:26] <Laurenceb> if one fails you can skip it
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[16:26] <hallam> if it fails it'll probably foul the rest of them
[16:26] <hallam> hi rjharrison
[16:26] <Laurenceb> well it might not fire
[16:28] <Laurenceb> if you have a string you need pyro string releasers
[16:29] <hallam> you could actually use your resistors again :P
[16:29] <Laurenceb> hehe
[16:29] <Laurenceb> actually it might be the lightest
[16:29] <Laurenceb> they wont be very jerk tolerant
[16:30] <hallam> if the chutes are small the loads won't be high
[16:30] <Laurenceb> true
[16:30] <Laurenceb> you could use polythene chutes
[16:30] <Laurenceb> ~2 to 8 ''
[16:31] <rjharrison> Hi hallam
[16:31] <Laurenceb> maybe you could have one resistor/heater device that stops them unwinding
[16:32] <rjharrison> I'v been thinking about rx on 169
[16:32] <rjharrison> I need an antenna
[16:32] <rjharrison> This looks sort of interesting http://www.bloomington.in.us/~wh2t/Jpole.htm
[16:32] <rjharrison> Anyone had any experience
[16:33] <Laurenceb> nope
[16:35] <Laurenceb> hallam: two lines of streamers/minchutes connected by meltasble ties
[16:35] <Laurenceb> then a heated alu rod that cuts through one or so per second
[16:37] <hallam> rjharrison: that looks pretty neat
[16:37] <hallam> cheap and portable
[16:37] <rjharrison> Yep light and cheap
[16:38] <rjharrison> Will have a play and see how well it works
[16:44] <Laurenceb> hallam: do you have a flange on top of the CF rocket body?
[16:48] <hallam> at the moment the nosecone is a push-fit
[16:48] <hallam> no flange
[16:48] <Laurenceb> right
[16:48] <Laurenceb> hmm hard to mount chutes
[16:53] Action: SpeedEvil ponders SS foil balloons.
[16:53] <Laurenceb> hehe
[16:53] <SpeedEvil> Weld a couple of circles of foil together, teeny bit of pyrogen inside.
[16:54] <SpeedEvil> roll up, deploy, ignite, and you've got a nice stainless ball chute.
[16:54] <Laurenceb> until it rips
[16:55] <SpeedEvil> yes, it won't be a good sphere.
[16:55] <SpeedEvil> It'll be wrinkled somewhat.
[16:56] <Laurenceb> I think a flange with plastic cylinders mounter in would be best
[16:56] Action: SpeedEvil passes Laurenceb a stack of plastic cups.
[16:56] <Laurenceb> 4 or so individula quite small chutes made from polythene
[16:57] <Laurenceb> yeah, light as poss
[16:57] <Laurenceb> whilst being able to hold the chute and withstand the pyro fiting it
[16:57] <Laurenceb> have say a 6'', 10'', and two 36'' or something
[16:58] <Laurenceb> hmm or lighter - plastic holders above the flange
[16:58] <SpeedEvil> Hmm.
[16:58] <Laurenceb> then rivets in the flange to hold the lines
[16:58] <SpeedEvil> What about deploying the chute on the way out?
[16:58] <SpeedEvil> oops
[16:58] <Laurenceb> from each chute
[16:58] Action: SpeedEvil forgot why this was happening.
[16:58] <Laurenceb> lol
[16:58] <Laurenceb> yeah, deploy very low
[16:59] <Laurenceb> < 10Km altitude
[16:59] <Laurenceb> without guidance you want to have a radio wondow to find the rocket
[17:00] <Laurenceb> but you dont want to open too soon or you'll rip/melt the chutes
[17:00] <Laurenceb> once its below a few hundered meters you lose radio
[17:02] <SpeedEvil> What's the CEP?
[17:02] <Laurenceb> dunno
[17:02] <Laurenceb> but its going to be swaying around on the balloon
[17:02] <Laurenceb> its got to be 10s of Km
[17:04] <Laurenceb> but I think with multiple polythene chutes opened low during re-entery its not too hard for <100grams
[17:04] <SpeedEvil> Where's the launch?
[17:04] <Laurenceb> erm...
[17:06] <Laurenceb> maybe at some point in the future is the plan I think
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[17:08] <hallam> esrange or black rock
[17:08] <Laurenceb> black rock would be awsome
[17:08] <SpeedEvil> Are they far enough from the coast?
[17:08] <Laurenceb> do it at burning man :P
[17:09] <Laurenceb> yeah it would just have to be at burning man
[17:11] <SpeedEvil> -6 tonight.
[17:34] <natrium42> iran launches satellite
[17:34] <natrium42> pretty cool
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[17:41] <Laurenceb> does it have a speaker on?
[17:41] <Laurenceb> to broadcast the call to prayer
[17:41] <SpeedEvil> 'This board has been hand worked and hand distressed to make it look very old if it has worn away in places, just like a reclaimed antique board prefinished with 8 coats of aluminium oxide with a UV top coat for 20 years of easy maintained clean floors.'
[17:41] <SpeedEvil> Cunning.
[17:42] <SpeedEvil> I diddn't know they were vacuum coating floorboards now :)
[17:42] Action: SpeedEvil suspects someone is confused.
[17:42] <Laurenceb> I dont follow
[17:43] <SpeedEvil> It's a floorboard.
[17:43] <SpeedEvil> You can't coat with aluminium oxide - it's a solid.
[17:43] <SpeedEvil> you could only do that if you vacuum deposited it onto the wood.
[17:43] <SpeedEvil> (which'd probably be impossible due to outgassing and stuff)
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[17:46] Action: Laurenceb is reading the wiki article on burning man
[17:47] <SpeedEvil> Baste often, to avoid that.
[17:47] <Laurenceb> hehe
[17:47] <Laurenceb> was thinking CUSF could launch from there
[17:47] Action: SpeedEvil sighs.
[17:48] <Laurenceb> "Burning your own art must be done on an approved burn platform."
[17:48] <SpeedEvil> 'Do you have anything to declare?'
[17:48] <SpeedEvil> '123Kg of rocket-fuel'
[17:55] <Laurenceb> IIRC it comes from the states anyway
[17:55] <SpeedEvil> Dunno any legalities on foreigners launching stuff to 100Km
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[18:14] <jcoxon> evening all
[18:21] <shellevil> 'o
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[18:26] <jcoxon> hey shellevil
[18:26] <jcoxon> just got my cable to connect my ft817 to my computer
[18:26] <jcoxon> can finally set up my auto tracking station
[18:34] <Laurenceb> I'm off, cya
[18:35] <shellevil> neat!
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[20:00] <hallam> shit, the Iranian thing has a 3rd stage
[20:00] <hallam> chap in Edinburgh saw it
[20:01] <hallam> ah no, 2nd stage
[20:04] <shellevil> umm. ed... that'd make it what - retrograde high inclination?
[20:04] <shellevil> Or am I confused.
[20:05] <hallam> I don't think it tells you anything about whether it's retrograde or prograde
[20:05] <hallam> nah it's def. prograde
[20:06] <shellevil> If it's second stage, surely it does?
[20:07] <shellevil> oops
[20:07] <shellevil> yes, I was confused.
[20:07] <hallam> 1 33506U 09004A 09034.19387999 .00095226 13865-4 25133-3 0 80
[20:07] <hallam> 2 33506 55.5083 313.4501 0099270 151.1927 209.4657 15.86589494 74
[20:08] <hallam> 55.5 degree inclination
[20:08] <hallam> not sure why the launched so far north, range constraints I guess
[20:08] <shellevil> from russia I see
[20:09] <hallam> ?
[20:09] <fergusnoble> hallam: lets see if we can take a look!
[20:09] <hallam> no, it was a homegrown launcher, that's why it's so important
[20:09] <hallam> yeah fergusnoble I'm keen
[20:09] <shellevil> Iran launched its first satellite into space from Plesetsk in northern Russia on Thursday, joining a select club of countries.
[20:09] <fergusnoble> will it be quite difficult?
[20:09] <shellevil> doh
[20:09] <fergusnoble> when does it pass over?
[20:09] Action: shellevil should check the dates.
[20:10] Action: natrium42_ slaps shellevil around a bit with a zeusbot
[20:10] <hallam> fergusnoble: you can only see it shortly before dawn and after dusk
[20:10] <hallam> I'll find out about passes
[20:10] <fergusnoble> ok cool
[20:10] <hallam> http://www.n2yo.com/?s=33506
[20:11] <hallam> there's one in 12 minutes
[20:11] <hallam> but I don't think we can get the scope set up in time
[20:11] <hallam> after that, tomorrow evening
[20:12] <shellevil> what's the designator?
[20:12] <hallam> it probably will be pretty tricky as a first attempt
[20:12] <fergusnoble> how long is it in the sky?
[20:12] <hallam> 33506
[20:12] <hallam> about 8 minutes
[20:14] <hallam> the satellite itself will be about +7 but the 2nd stage should be +4
[20:15] <hallam> so maybe not as tricky as all that
[20:15] <hallam> almost naked-eye
[20:15] <shellevil> sat is almost binocs tho
[20:15] <shellevil> actuall no
[20:16] <shellevil> sky won't be that dark
[20:16] <hallam> the sat is less interesting than the rocket stage
[20:16] <hallam> size of the rocket stage can tell us about their launch capabilities
[20:17] <hallam> fergusnoble, I'm plugging away at the asm correlator
[20:17] Action: shellevil suspects the poor thing is getting pinged to death by every active radar/lidar in the world.
[20:17] <shellevil> The blackfin one?
[20:17] <hallam> yeah
[20:18] <hallam> first thing I've written in blackfin asm, so it's a little slow going at first
[20:19] <shellevil> what performance you getting in C?
[20:19] <hallam> 40MHz/channel
[20:19] <shellevil> what's the freq?
[20:19] <hallam> eh, actually about 45
[20:19] <hallam> 500
[20:19] <shellevil> that's quite adequate.
[20:19] <shellevil> more'd be nicer of course
[20:20] <shellevil> less'd
[20:20] <hallam> I'd like to have some CPU spare for JPEG
[20:20] <shellevil> jpeg in hardware on camera
[20:20] <shellevil> ?
[20:20] <hallam> of the 45, 35 is the correlator and the rest is mostly floating point for the loop discriminators
[20:20] <hallam> not with this camera
[20:20] <shellevil> what's it?
[20:20] <hallam> OV9655
[20:21] <hallam> I should be able to get the correlator down to 6 and get rid of the floating point, pretty sure I can get the lot under 10
[20:22] <shellevil> Or refactor it in C for more speed?
[20:22] <shellevil> oh - C won't grok countones
[20:25] <hallam> I don't understand what you're suggesting
[20:26] <shellevil> I mean rewrite it in C to convince your compiler to emit more optimal code.
[20:26] <hallam> oh
[20:26] <shellevil> sometimes it can be quite easy.
[20:26] <hallam> eh, the important part is only about 15 lines of C
[20:26] <shellevil> And yes, of course, doing that is stupid - but...
[20:26] <shellevil> uppose so
[20:33] <fergusnoble> hallam: if you havnt eaten ive cooked a big soup
[20:34] <hallam> oh cool, I'd love some
[20:34] <hallam> shall i come over now?
[20:35] <fergusnoble> yeah
[20:35] <hallam> ok great
[20:35] Nick change: hallam -> hallam|souper
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[21:29] Nick change: hallam|souper -> hallam
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[22:30] <jcoxon> hmmm anyone around?
[22:36] Action: gordonjcp is
[22:36] <gordonjcp> briefly
[22:37] <SpeedEvil> slightly
[22:38] <jcoxon> hmmmm
[22:38] <jcoxon> rtty on an arduino with pwm and a low pass filter
[22:39] <gordonjcp> yup
[22:39] <jcoxon> its a bit of a blur, not well defined
[22:39] <jcoxon> could the analogwrite function be too slow
[22:43] <jcoxon> ?
[22:44] <SpeedEvil> You do have several times the pwm freq of your output filter?
[22:44] <SpeedEvil> I don't know the specific code
[22:45] <jcoxon> hmmmm, i was fiddling around
[22:46] <jcoxon> so the filter should be several times the pwm freq?
[22:46] <gordonjcp> no
[22:46] <gordonjcp> the PWM frequency should be higher than the lowpass filter critical frequency
[22:46] <SpeedEvil> yeah - that's what I mean
[22:47] <gordonjcp> yes, but the other way round from what jcoxon said ;-)
[22:47] <jcoxon> okay
[22:47] <jcoxon> right well i didn't calculate anything
[22:47] <jcoxon> will do that now
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[22:49] <jcoxon> gordonjcp, what happens if its a lot higher?
[22:50] <SpeedEvil> the PWM frequency needs to be higher than the filter cutoff or you get lots of ripple in the output
[22:50] <SpeedEvil> lots higher is good
[22:50] <gordonjcp> yup
[22:50] <SpeedEvil> as long as you don't run out of bits
[22:50] <gordonjcp> jcoxon: same idea as sampling theory
[22:50] <gordonjcp> well, that's what it is, after all
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[00:00] --- Wed Feb 4 2009