highaltitude.log.20081031

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[00:09] <Laurenceb> hi fnoble
[00:12] <fnoble> hi Laurenceb
[00:15] <Laurenceb> fnoble: do you have a reliable technique for plastic welding?
[00:15] <Laurenceb> I got one of the bag sealers off ebay, but it tears thin polythene
[00:16] <SpeedEvil> :/
[00:16] <SpeedEvil> sacrificial layer of slightly thicker?
[00:16] <Laurenceb> hmm
[00:16] <Laurenceb> interesting idea
[00:16] <Laurenceb> maybe some kapton
[00:16] <SpeedEvil> Though of course much more annoying.
[00:16] <SpeedEvil> Oh - that'd work
[00:17] <SpeedEvil> I was meaning a layer that'd end up joined
[00:18] <Laurenceb> blurg... this code is getting very tedious
[00:19] <Laurenceb> I've shrunk the mini rogallo down to 15.01KB
[00:19] <SpeedEvil> How much you have?
[00:19] <Laurenceb> 15.5
[00:20] <Laurenceb> theres a 0.5K bootloader
[00:21] <Laurenceb> one thing I'm stuck on - I'm using eeprom to store data, it has an internal address pointer
[00:21] <Laurenceb> so when the user presses the "dead man switch" the address pointer is reset to zero
[00:22] <Laurenceb> but if there is a reset for any reason during the flight, the eeprom could get overwritten
[00:22] <SpeedEvil> what's the dead-man switch?
[00:23] <Laurenceb> a button you have to press when you power up
[00:23] <Laurenceb> or the code will assume something whent wrong, and attempt to recover the previous flight state
[00:24] <Laurenceb> I call it that as I heard the concept refurred to as that somewhere...
[00:24] <SpeedEvil> dead man switch would typically be opposite sense to that.
[00:24] <SpeedEvil> something is wrong if the switch is inactivated during flight
[00:25] <Laurenceb> I guess i could "paint" the eeprom with a null record
[00:25] <SpeedEvil> Why would you press the switch on the ground?
[00:25] <Laurenceb> then use a sucessive approximation technique to find the top of the data
[00:26] <SpeedEvil> Make the switch a toggle?
[00:26] <Laurenceb> i.e. so number of eeprom reads = log(number of records)
[00:26] <Laurenceb> you have to press the button or it will load the last stored state from the eeprom
[00:27] <Laurenceb> rather than going into the mission setup routines
[00:27] <SpeedEvil> log yes/no?
[00:27] <SpeedEvil> Laurenceb: overthinking
[00:27] <SpeedEvil> Laurenceb: read it sequentially, it'll only take a few milliseconds
[00:27] <SpeedEvil> If you're using the size of eeprom I think you are.
[00:27] <SpeedEvil> ah - right
[00:27] <Laurenceb> nah I2C is a bit slow
[00:27] <Laurenceb> I can probe halfway
[00:28] <Laurenceb> then go up or down ect
[00:28] <Laurenceb> like an ADC
[00:28] <SpeedEvil> A bit slow - sure - but that's maybe 60K/second, and you've got a 64K RAM
[00:28] <SpeedEvil> Just to save space over successive approximation.
[00:28] <Laurenceb> I think the algorythm is more groovy :P
[00:28] <SpeedEvil> And it's clearly right, with no possibility of fencepost errors.
[00:29] <Laurenceb> my other problem is there are two sizes of data record
[00:29] <fnoble> Laurenceb, sorry someone came to the door, the reliable way to weld plastic usjust to get it uniformly hot in a repeatable way - you need to be able to vary the temperature
[00:29] <fnoble> there is a certain point at which it forms a good joint
[00:29] <Laurenceb> one is 12 bytes, one 24
[00:29] <SpeedEvil> groovy is cool! Till it's groovy and crashing on a stadium, killing thousands!
[00:29] <fnoble> too hot and it gets holes and bubbles
[00:29] <Laurenceb> 24 for during the descent
[00:30] <SpeedEvil> Well - slightly annoying one.
[00:30] <fnoble> to cold and it can look joined but just peels appart
[00:30] <Laurenceb> fnoble: is your setup working well enough to make a tetroon?
[00:30] <SpeedEvil> Laurenceb: how many log events do you have?
[00:30] <SpeedEvil> Laurenceb: log entries I mean in RAM?
[00:30] <fnoble> we just have a steel strip element and a high current power supply driving it and vary the amount of time its on for
[00:30] <SpeedEvil> Laurenceb: log entries I mean in ROM?
[00:31] <Laurenceb> as many as possible
[00:31] <Laurenceb> I'm going to try and log at 1Hz
[00:31] <fnoble> Laurenceb, yeah weve already made lots of small balloons and experiments with out hand welders
[00:31] <fnoble> they work really well
[00:31] <Laurenceb> cool
[00:31] <Laurenceb> I'm thinking of putting a farnell order in
[00:31] <SpeedEvil> Laurenceb: probably best to work out the worst-case time if your cutdown fails.
[00:31] <Laurenceb> for ALDIST
[00:31] <Laurenceb> SpeedEvil: yeah
[00:31] <SpeedEvil> Laurenceb: and you get a bit of an updraft.
[00:32] <Laurenceb> I guess I can store a u16 pointer to the start for the 24 byte records
[00:32] <Laurenceb> when the code makes the transition to 24 byte mode
[00:33] Action: SpeedEvil tries to work out a way to do guidance of a remote from a balloon without GPS.
[00:33] <SpeedEvil> A 'flight mode' byte at 0?
[00:33] <fnoble> the weld-o-tron though isnt quite ready yet, but the heating element that it uses is working fine and can make long continuous welds rather than only being able to do sections
[00:33] <Laurenceb> SpeedEvil: or on the uC eeprom
[00:33] <Laurenceb> would simplify things
[00:34] <SpeedEvil> 'weight on wheels' switch'd be nice.
[00:34] <SpeedEvil> If it had wheels.
[00:34] <SpeedEvil> And would often land upright.
[00:34] <Laurenceb> I turn everything off on landing
[00:34] <Laurenceb> and go into low power recovery mode that lasts 24 hours or so
[00:34] <SpeedEvil> How do you tell landing?
[00:34] <Laurenceb> velocity ==0
[00:34] <Laurenceb> and altitude <200meters
[00:34] <SpeedEvil> Do you just die if the GPS fails?
[00:34] <Laurenceb> for 8 seconds continuously
[00:35] <SpeedEvil> Or is there a limp mode.
[00:35] <Laurenceb> if the gps dies it goes into a reset loop
[00:35] <Laurenceb> but there isnt much else you can do
[00:35] <SpeedEvil> Is 200m sane for the topography?
[00:35] <Laurenceb> yep
[00:35] <Laurenceb> for east anglia
[00:35] <SpeedEvil> Well - the gyro is quite low drift, and you could do reasonable ballparking couldn't you?
[00:36] <Laurenceb> nah
[00:36] <fnoble> Laurenceb, ive seen some gps' give altitudes above 200m whilse on the ground when they dont have many sats
[00:36] <SpeedEvil> Actually - center the stick, and it'll prolly be not insane.
[00:36] <Laurenceb> fnoble: yeah but as its coming down it will have a good signal
[00:36] <Laurenceb> if(Gps.altitude<200.0 && !Gps.veast && !Gps.vnorth)
[00:36] <Laurenceb> is the condition
[00:37] <Laurenceb> it has to be valid for 8 seconds
[00:37] <SpeedEvil> Just hope for no headwind
[00:37] <fnoble> and the velocity goes to exactly zero when its sitting still?
[00:37] <SpeedEvil> Does your GPS report actually 0 sitting still?
[00:37] <Laurenceb> yep
[00:37] <SpeedEvil> Many don't.
[00:37] <Laurenceb> I've tried it
[00:38] <Laurenceb> hmm yeah maybe I'll switch it to <0.1 or something
[00:38] <SpeedEvil> I'd be tempted to add a 'or flighttime >2h (or whatever)
[00:38] <Laurenceb> but when I've played with it thats what happened
[00:38] <Laurenceb> http://wiki.ukhas.org.uk/code:parafoil_tests
[00:39] <Laurenceb> you can see the heading goes to zero when I stop moving
[00:39] <fnoble> SpeedEvil, we came unstuck with a time based limit on our flights - our cutdowns were set to go after a certain amount of time if none of the other conditions had been met
[00:39] <fnoble> but twice that would have cut us down too early
[00:40] <fnoble> as the payload was on for a while on the ground, ascent rate want on spec etc
[00:40] <SpeedEvil> That's a good point.
[00:40] <fnoble> luckily the cutdowns failed and we went on to get some good altitudes, would have cut down at like 20km otherwise though
[00:40] <SpeedEvil> A nice bright 'I've just reset' light might be nice
[00:40] <fnoble> yeah thats a very good idea
[00:40] <Laurenceb> I have a 1Hz flashing light
[00:41] <Laurenceb> so you know eveythings running
[00:41] <SpeedEvil> No - a light indicating that you've reset and started a new flight within the last 10s
[00:41] <SpeedEvil> to make sure that button-push took.
[00:41] <Laurenceb> yeah
[00:41] <Laurenceb> just use RS232
[00:42] <SpeedEvil> Been looking at some of the braided fishing line on ebay.
[00:42] <Laurenceb> when I was doing some tests with rogallos I added some code to stop logging if there was a very large gyro transient
[00:42] <SpeedEvil> Seems to claim ~3GPa on some of the best stuff, and about 10 quid/Km.
[00:42] <Laurenceb> seemed to detect landing well
[00:43] <SpeedEvil> I really have no idea what the dynamics of a 30Km string'd be.
[00:43] <fnoble> Laurenceb, so what is your worry about your eeprom?
[00:44] <SpeedEvil> Laurenceb: or a birdstrike
[00:44] <fnoble> that data will be overwritten?
[00:44] <Laurenceb> yep
[00:44] <fnoble> upon reset
[00:44] <Laurenceb> yeah
[00:44] <Laurenceb> if theres a watchdog reset or something
[00:45] <Laurenceb> I've tried to make the rest of my code stand up to anything like that happening
[00:45] <fnoble> so just store a byte which says where in eeprom to start writing
[00:45] <fnoble> and reset it to zero if you prsee the switch on startup
[00:45] <Laurenceb> as theres a few hundered bytes spare I thought I'd take care of the eeprom properly
[00:45] <Laurenceb> fnoble: you cant go overwriting eeprom all the time like that
[00:46] <Laurenceb> it would have to be written each time a record was written
[00:46] <fnoble> ohsorry, yeah your doing 1hz just read
[00:46] <Laurenceb> so I was thinking of painting the eeprom
[00:47] <Laurenceb> then finding the top by sucessive approximation
[00:48] <fnoble> dont bother with that, just check the first byte isnt the magic number that was painted and if so the nskip forwards 12 bytes
[00:48] <Laurenceb> I guess really I should learn how to do it properly and use SD cards
[00:48] <Laurenceb> but that involves sharing the SPI between two tasks
[00:48] <fnoble> SD cards are good
[00:49] <fnoble> but they have been giving me hassle for a long time
[00:49] <Laurenceb> yeah I remember
[00:49] <fnoble> i think its worth it though
[00:49] <Laurenceb> I have the gyro on the spi as well
[00:49] <fnoble> sharing SPI isnt so hard, just use a mutex
[00:50] <Laurenceb> hardware?
[00:50] <fnoble> oh, on the cardware side you just assert the appropriate CS line
[00:50] <fnoble> SPI is designed for multi-slave
[00:50] <Laurenceb> my problem is say my sd card write routine is in the middle of an exchange
[00:50] <SpeedEvil> MicroSD doesn't have a CS line - but SD I think does.
[00:51] <Laurenceb> then the gyro task comes along
[00:51] <SpeedEvil> Log the gyro data to RAM
[00:51] <Laurenceb> how do I control things?
[00:51] <fnoble> so you have a multitasking system?
[00:51] <Laurenceb> yes
[00:51] <SpeedEvil> and then the write task notes it's got stuff to do, and does it
[00:51] <fnoble> then you use a mutex and a data queue
[00:52] <SpeedEvil> Or blocking interrupts if you're lazy and that's good enough
[00:52] <fnoble> the way i do it is to have the task block if the SPI isnt free
[00:52] <fnoble> and that task is put back into the runnable state when the SPI becomes free
[00:53] <fnoble> it is possible in theory to get deadlock, but in such a simple system its ok
[00:53] <Laurenceb> yeah
[00:53] <fnoble> did you roll your own multitasking code?
[00:53] <Laurenceb> not really
[00:53] <fnoble> what are you using?
[00:53] <Laurenceb> its just interrupts with a bit of asm
[00:53] <Laurenceb> avr
[00:53] <fnoble> ok cool
[00:54] <Laurenceb> I mucked about with the existing avr libc interrupt code so I could nest them, but its all already documented
[00:54] <fnoble> it was a lot easier for me because with tnkernel you get a library of functions to implement mutexes etc that integrates with the task scheduler
[00:55] <Laurenceb> yeah I've had to create flags for everything
[00:56] <fnoble> im sure if your careful its possible
[00:56] <Laurenceb> I could probably simplify the code by just sticking on an RTOS, but I'm sure it would be bigger
[00:56] <fnoble> yeah, would be bigger i would imagine
[00:57] <Laurenceb> theres only effectively two tasks and two ISR
[00:57] <fnoble> ok, im off to bed
[00:57] <Laurenceb> cya
[00:57] <fnoble> night
[00:57] Nick change: fnoble -> fnoble|away
[01:44] <Laurenceb> http://www.directlauncher.com/
[01:48] <SpeedEvil> Laurenceb: does it list a price?
[01:49] <SpeedEvil> I don't see a 'buy now' button.
[01:49] Action: SpeedEvil has a spare 15 quid.
[01:49] <Laurenceb> lol
[01:49] <Laurenceb> ~12G$
[01:49] <SpeedEvil> DOING IT WRONG.
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[07:04] <natrium42> edmoore!111
[07:04] <edmoore> yo
[07:07] <natrium42> about to go to bed :S
[07:10] <natrium42> g'nite
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[07:10] <edmoore> lol
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[08:07] <rjharrison> morning all
[08:08] <rjharrison> jcoxon is the weather still behaving
[08:14] <jcoxon> morning rjharrison
[08:14] <jcoxon> yeah it is
[08:16] <jcoxon> it ain't perfect but its pretty good
[08:16] <jcoxon> and as we get closer i'm more confident with the forecasts
[08:16] <jcoxon> cause today is perfect :-p
[08:17] <rjharrison> Haha
[08:17] <rjharrison> Typical, Fridays are always the best
[08:17] <rjharrison> ;-)
[08:18] <jcoxon> yeah
[08:18] <jcoxon> shame
[08:18] <jcoxon> oh well sunday will be good
[08:18] <jcoxon> and its ears
[08:18] <rjharrison> Just inking two weeks ago about now
[08:19] <rjharrison> Ok do you have a coord for EARS?
[08:19] <rjharrison> or postcode
[08:19] <rjharrison> thinking*
[08:20] <jcoxon> http://www.ears.org.uk/launches/site/index.shtml
[08:23] <jcoxon> doubt the ground weather will be amazing - probably quite cold
[08:23] <jcoxon> but th winds are fine
[08:25] <fnoble|away> jcoxon, hello
[08:25] <fnoble|away> jcoxon, get my text?
[08:26] <rjharrison> Just browsing the ears site. Cool. Now I know what EARS is :) I wonder if they have such a thing up here in the north.
[08:28] <jcoxon> fnoble|away, hey yeah
[08:31] <jcoxon> poor phoenix, too cold now :-)
[08:32] <jcoxon> perhaps it'll wake up next year
[08:35] <rjharrison> Will bring a some food and coffee in a flask along with me.
[08:35] <jcoxon> sounds like a plan
[08:37] <fnoble|away> jcoxon, going for ears of churchill?
[08:38] <jcoxon> fnoble|away, your pm doesn't work :-)
[08:38] <jcoxon> ummmm
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[08:58] <jcoxon> rjharrison, i'm thinking of suggesting to meet jsut after 10 at ears
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[13:51] <Laurenceb> hello
[13:51] <Laurenceb> http://maps.google.co.uk/maps?f=q&hl=en&geocode=&q=model+shop&sll=51.254395,-0.595322&sspn=0.152345,0.30899&ie=UTF8&ll=51.380175,-0.784691&spn=0.002294,0.006866&t=h&z=18
[13:51] <Laurenceb> ^ wtf?
[13:56] <jcoxon> Laurenceb, what have you found!
[14:01] <jcoxon> bbiab
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[14:02] <Laurenceb> clearly a secret underground nuclear reactor
[14:03] <gordonjcp> big grey screen
[14:07] <epictetus> it's a race track of some kind
[14:08] <epictetus> in fact it kinda looks like a "Crazy 8s" track, although racing Crazy 8's (a variant on the Demolition Derby where you race in a figure 8 pattern and cars tend to crash at the X in the middle) must be illegal
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[14:35] <rjharrison> jcoxon: Soory being in a meeting. 10am sounds great I'll aim for 9:45 just to be safe. Lanch at 11am aprox?
[14:35] <rjharrison> been
[14:38] <edmoore> is this sunday?
[14:38] <jcoxon> yes
[14:38] <edmoore> cool, I may come up very am
[14:38] <edmoore> AM
[14:38] <jcoxon> :-D
[14:39] <jcoxon> also... my dad is coming to help, he is bring the ultimate ukhas landy
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[14:52] <rjharrison> BTW that map pos from Laurenceb looks like a vehical test track. That looks like the skid pan... An onther ideas?
[14:52] <rjharrison> http://maps.google.co.uk/maps?f=q&hl=en&geocode=&q=model+shop&sll=51.254395,-0.595322&sspn=0.152345,0.30899&ie=UTF8&ll=51.380175,-0.784691&spn=0.002294,0.006866&t=h&z=18
[15:41] <SpeedEvil> test track is pretty obvious.
[15:41] <SpeedEvil> I don't see what else it can be
[15:48] <epictetus> race track!
[15:49] <SpeedEvil> some bits of it, yes.
[15:49] <SpeedEvil> There is a non-intersecting track
[15:56] <Laurenceb> hmm
[15:56] <Laurenceb> http://cgi.ebay.co.uk/10m-60-waterproof-pink-RIP-STOP-nylon-fabric_W0QQitemZ200268494112QQcmdZViewItem?hash=item200268494112&_trksid=p3286.c0.m14&_trkparms=72%3A1432|66%3A2|65%3A12|39%3A1|240%3A1318
[15:56] <Laurenceb> dare I ?
[16:07] Action: SpeedEvil has been looking at http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=260304832473
[16:07] <SpeedEvil> And similar
[16:09] <SpeedEvil> You'd need to oil it to make it airtight, and that's prolly a little small for a balloon :)
[16:09] <Laurenceb> what for?
[16:10] <SpeedEvil> Just wondering about jetstream kites.
[16:17] <Laurenceb> cool
[16:22] <SpeedEvil> Though of course not ones shipping power to the ground.
[16:22] <SpeedEvil> That's rather high budget.
[16:22] Action: SpeedEvil wants room temperature superconductors.
[16:22] <Laurenceb> http://www.reactionengines.co.uk/
[16:35] <Laurenceb> http://www.reactionengines.co.uk/sabre.html
[16:45] <SpeedEvil> Fun - but...
[16:45] <SpeedEvil> There is one horrid thing about airbreathing engines.
[16:46] <SpeedEvil> They breathe air.
[16:46] <SpeedEvil> This means that you need to fly in air dense enough to feed the engine, with all the drag and thermal heating implications that has.
[16:47] <Laurenceb> well if its a plane you need enough lift
[16:47] <SpeedEvil> Sure.
[16:47] <SpeedEvil> Mach 5.5 is also a teeny amount of the energy needed to get to orbit.
[16:48] <SpeedEvil> A lot of the time if you optimise the system you've added onto the rocket to save fuel for size, you end up deleting it.
[16:49] <SpeedEvil> Not to mention that a powerplant like that is a horrible risk until you've actually got it flying.
[16:49] <Laurenceb> mmm
[16:50] <Laurenceb> I'd say they were crazy but they seem to have proved the convepts
[16:50] <Laurenceb> ooh http://uk.farnell.com/osram/splpl90/laser-diode-pulsed-905nm/dp/1226448
[16:50] <SpeedEvil> 'proved the concepts' doesn't mean much until you've actually done tests.
[16:51] <SpeedEvil> Many hundreds of millions have been spent on scramjet and other hypersonic engine research.
[16:51] <SpeedEvil> And in many ways, you don't actually care about the weight of the fuel - as it drops out of the equation as other than a structural load.
[16:52] <SpeedEvil> You care about the volume - and liquid oxygen is great that way, it's nice and dense.
[16:52] <SpeedEvil> >1Kg/l
[16:53] <SpeedEvil> On the other hand the skylon needs LH2.
[16:53] <SpeedEvil> This is 70g/l
[16:54] <Laurenceb> I see
[16:54] <Laurenceb> I'm considering a laser diode for plastic welding...
[16:56] <Laurenceb> they are acceptable prices
[16:57] <Laurenceb> problem is I need a database of polymer absorption cross sections
[16:58] <Laurenceb> aha http://journals.royalsociety.org/content/p7w5406854237k00/
[16:58] <Laurenceb> right we just need a reactor for speedly plastic welding
[17:01] <Laurenceb> maybe http://henryhallam.cjb.net/~henry/fusor/Copy%20of%20index.htm would suffice :P
[17:02] <SpeedEvil> IIRC PE is quite transparent even into mid-IR
[17:02] <SpeedEvil> It's used for PIR lenses after all
[17:02] <SpeedEvil> Oh - and look at average power on that
[17:03] <SpeedEvil> It's something like 1us max pulse.
[17:03] <SpeedEvil> so 25uJ/pulse
[17:03] <SpeedEvil> and 1Khz max rep rate
[17:08] <SpeedEvil> Oooh - silk blimp envelopes!
[17:08] <SpeedEvil> http://cgi.ebay.co.uk/100-silk-floaty-NEW-LOOK-INSPIRE-party-dress-bnwt-22_W0QQitemZ260307263562QQcmdZViewItem?hash=item260307263562&_trksid=p3286.c0.m14&_trkparms=72%3A1431|66%3A2|65%3A12|39%3A1|240%3A1318
[17:10] Action: SpeedEvil shouldn't point fingers.
[17:10] <Laurenceb> lol
[17:21] <SpeedEvil> Does it work to seal cheap thin binbags?
[17:21] <SpeedEvil> The thing you bought
[17:22] <Laurenceb> not very well
[17:22] <Laurenceb> it seals most thicker bags very well
[17:28] <SpeedEvil> You can't move it faster?
[17:28] <SpeedEvil> On thin stuff, or does it just tear?
[17:29] <Laurenceb> yep
[17:30] <Laurenceb> the polythene adheres to the ptfe
[17:30] <Laurenceb> heating element
[17:31] Action: SpeedEvil suggests something silly.
[17:31] <SpeedEvil> Have you tried a smear of cooking oil on the outside?
[17:31] <Laurenceb> hey
[17:31] <Laurenceb> good idea
[17:31] <Laurenceb> hmf
[17:31] <Laurenceb> I can tbe bothered to walk home its cold
[17:32] Action: SpeedEvil passes Laurenceb an inflatable bed.
[17:35] <Laurenceb> I want to make this http://wiki.ukhas.org.uk/ideas:rc_antenna_cutdown
[17:35] <Laurenceb> but I'm having trouble finding something for the choke
[17:36] <Laurenceb> if the resonant frequency of my inductor is around the frequency of the rf or below, will the parasitic capacitance form an RF leak?
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[17:39] <SpeedEvil> not loading
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[17:47] <Laurenceb> http://uk.farnell.com/ferroperm/1582-10uh-0-75a/inductor-axial-10uh-0-75a/dp/1186789
[17:47] <Laurenceb> think that will do it
[17:47] <SpeedEvil> the original page won't load
[17:47] <Laurenceb> dunno, it works for me
[17:48] <Laurenceb> http://wiki.ukhas.org.uk/_detail/ideas:rf_cutdown.png
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[17:49] <SpeedEvil> The chokes need to have an impedence of well over the antenna impedence or they will short it somewhat.
[17:49] <Laurenceb> yeah
[17:49] <mc-> Hi Laurenceb, that google map is the vehicle testing place in Crowthorne.
[17:50] <Laurenceb> Hi mc-
[17:53] <mc-> I think it's called MIRAS
[17:53] <mc-> how's Guildford?
[17:53] <Laurenceb> gues its ok
[17:54] <Laurenceb> but to be honest I'm thinking of quitting
[17:54] <Laurenceb> going to leave it until christmas
[17:54] <Laurenceb> see how it goes
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[17:55] <Laurenceb> I feel I'm wasting my time to a certain extent
[17:55] <mc-> oh
[17:56] <Laurenceb> anyway, we should meet up some time :P
[17:56] <mc-> Galileo is more complicated than GPS?
[17:56] <SpeedEvil> mc-: well...
[17:57] <mc-> yes, are you at the university?
[17:57] <SpeedEvil> The RF protocol is more advanced.
[17:57] <SpeedEvil> GPS is damn simple.
[17:58] <mc-> yes, GPS is a good standard.
[17:59] <Laurenceb> mc-: yeah I've got a room on campus
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[18:02] <mc-> I'm a bit busy this weekend, but sometime later next week would be good.
[18:03] <Laurenceb> cool
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[18:07] <mc-> SpeedEvil, did you say you are designing a rocket?
[18:12] <SpeedEvil> mc-: only in the sense that I have scribblings on paper and thoughts on design, and a few bits of hardware.
[18:13] <SpeedEvil> Realistically, I'd need ~50K to make a serious stab at developing it.
[18:13] <mc-> a few bits of hardware is better than me, I just have a Rattworks hybrid
[18:13] <mc-> what sort of motor, biprop?
[18:13] <SpeedEvil> It being a 1Kg orbital launcher with a GLOW of maybe a ton.
[18:14] <SpeedEvil> Yes.
[18:14] <SpeedEvil> Probably LOX/kero, maybe H2O2/alcohol.
[18:14] <SpeedEvil> Stage early and often and use cheap materials is the basic idea.
[18:14] <mc-> ground launch? how about LOX/Alcohol?
[18:15] <mc-> did you know you can order H202 from Sweden?
[18:15] <SpeedEvil> HTP?
[18:15] <SpeedEvil> Availability of HTP is a problem.
[18:15] <mc-> think it's 85%
[18:15] <mc-> forgotten the company name
[18:15] <SpeedEvil> Which pushes somewhat towards LOX.
[18:16] <mc-> cryo has its downsides
[18:16] <SpeedEvil> As you need to get it to 95% or better, which means your own little vacuum distilling plant.
[18:16] <SpeedEvil> Sure.
[18:16] <SpeedEvil> Everything has its downsides.
[18:16] <SpeedEvil> At least H2 is right out for small rockets.
[18:16] <mc-> have you seen the microlaunchers.com site? Charles talk about LOX preburners
[18:17] <SpeedEvil> No.
[18:18] <SpeedEvil> I've got too many projects that need to be done to get in money :/
[18:18] <SpeedEvil> So the rocket has rather been shelved.
[18:18] <mc-> a preburner makes combustion stability much better
[18:18] <SpeedEvil> And adds complexity.
[18:18] <SpeedEvil> Nothing free.
[18:18] <SpeedEvil> :/
[18:19] <mc-> I know the feeling, earn the money first
[18:19] <mc-> A preburner is quite simple, just a small injector in a pipe.
[18:19] <mc-> no cooling needed
[18:21] <SpeedEvil> My vague prototypes were regeneratively cooled electroformed engines made largely of copper, with 'proper' injectors.
[18:21] <mc-> wow, regens are difficult
[18:21] <SpeedEvil> And have benefits.
[18:22] <SpeedEvil> Largely that you can actually test them lots.
[18:22] <SpeedEvil> That was my other basic idea.
[18:23] <SpeedEvil> Each stage would actually be tested on the bench several times, and then flown in a ballistic shot and recovered a couple of times.
[18:23] <SpeedEvil> Before being stacked and flown.
[18:23] <mc-> pressure fed?
[18:23] <SpeedEvil> Pumped.
[18:23] <SpeedEvil> :/
[18:24] Action: SpeedEvil has a diagram of A4 somewhere with a diaphramless pressure-fed pump.
[18:24] <SpeedEvil> basically a hybrid rocket engine optimised as a gas generator to act as a pump.
[18:24] <mc-> pistonless pump? Lots of complexity
[18:25] <SpeedEvil> Pressure fed was very possible.
[18:25] <mc-> I think a pressure fed can get into space, wasn't the British rocket pressure fed with H202?
[18:25] <SpeedEvil> However, some bastard patented it after I designed it.
[18:25] <SpeedEvil> mc-: I don't care what 'can' get into space. I care about what is the cheapest way.
[18:26] <mc-> pressure fed should be cheaper than pumped
[18:26] <SpeedEvil> If that means using a rhenium/iridium radiation cooled teeny engine, then that's fine.
[18:26] <SpeedEvil> I had a really quite simple design.
[18:27] Action: SpeedEvil wonders if anyone has any spare 3" Rh/Ir bar.
[18:27] <Laurenceb> rhenium?!
[18:27] <Laurenceb> never even heard of it
[18:27] <Laurenceb> :P
[18:27] <SpeedEvil> It's like platinum.
[18:28] <SpeedEvil> But more expensive.
[18:28] <mc-> Armadillo/Carmack's multistaged design looks cheap to build
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[18:28] <SpeedEvil> The nice thing is that you can make an engine that operates with a wall temperature of ~3000K, and is completely radiation cooled.
[18:29] <SpeedEvil> The nasty thing is... Well - it's >$1K/gm
[18:29] <SpeedEvil> The nasty thing is... Well - it's >$1K/oz
[18:29] <SpeedEvil> not _quite_ that bad
[18:30] <mc-> I think regens are the simplest way to cool, copper is cheap
[18:30] <SpeedEvil> Oh - and you need to deposite it with CVD
[18:30] <SpeedEvil> Well - not
[18:31] <SpeedEvil> the simplest form of cooling is to just throw away the coolant
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[18:31] <SpeedEvil> rather than try to regenerate it
[18:31] <mc-> I've seen a regen design that just wound a helix around a copper tube, and put the outer tube over the top.
[18:32] <SpeedEvil> Fabrication is an issue.
[18:32] <SpeedEvil> As is cavitation.
[18:32] <Laurenceb> armadillo have loads of problems with ablation
[18:32] <Laurenceb> inside the chamber
[18:32] <mc-> I helped him fabricate it...
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[18:39] <jcoxon> evening edmoore
[18:40] <Laurenceb> SpeedEvil: http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V1N-4D1CMR2-D&_user=121707&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_version=1&_urlVersion=0&_userid=121707&md5=bc8726d33ca2c2b00c5de800ff092a89
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[18:41] <edmoore> yo
[18:41] <natrium42> hi
[18:43] <jcoxon> hey na
[18:43] <jcoxon> natrium42, *
[18:43] <natrium42> wht's up?
[18:43] <SpeedEvil> Laurenceb: yeah - that sort of thing.
[18:43] <SpeedEvil> Laurenceb: annoyingly NASA pulled a lot of interesting stuff after 11/9
[18:44] <Laurenceb> thats just daft
[18:45] <jcoxon> natrium42, not much, finished teh payload
[18:45] <SpeedEvil> Well... yes.
[18:45] <natrium42> cool, so tomorrow is the day?
[18:45] <jcoxon> sunday
[18:45] <jcoxon> that said the weather isn't as good as i had hoped - its still oaky though
[18:45] <jcoxon> okay*
[18:46] <Laurenceb> well I'm off, cya all
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[19:48] Action: SpeedEvil wonders if you can cold-weld polythene under pressure.
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[20:00] <SpeedEvil> Aha! Explosive welding!
[20:01] Action: SpeedEvil gets out the C4.
[20:01] <Laurenceb> lol
[20:01] Action: Laurenceb is converting his bagsealer to use a power supply
[20:08] <Laurenceb> hmm annoyingly it seems my power supply hasnt got enough juice
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[20:14] <natrium42> Laurenceb, how well does it work?
[20:16] <Laurenceb> I'm just trying with spray polish
[20:16] <Laurenceb> seems to work extremely well if you get it right
[20:16] <Laurenceb> I've done a 20cm weld in 9.5um polythene
[20:17] <Laurenceb> problem is it looks like the best technique is to go slow, and it ends up cutting through in the weld center
[20:19] <natrium42> is it possible to be consistent by hand
[20:19] <natrium42> ?
[20:22] <Laurenceb> I think so
[20:24] <Laurenceb> but I dontthink this is good enough for a balloon envelope
[20:24] <Laurenceb> however its clearly possible with a better design of heated ptfe
[20:26] <natrium42> maybe some kind of CNC setup?
[20:27] <Laurenceb> edmoore and fnoble have done some work on this
[20:27] <natrium42> or a robot driving precisely with a welding head
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[20:32] <rjharrison> Evening all
[20:32] <rjharrison> Is the weather still behaving master coxon
[20:34] <rjharrison> Anyone who fancys a lift and is up for the chase on Sunday let me know. Depending on numbers I'll either bring the car or the 4x4
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[20:48] <natrium42> rjharrison, jcoxon said that sunday's the day
[21:00] <jcoxon> hey hey
[21:00] <jcoxon> rjharrison, the weather is sort of behaving
[21:01] <jcoxon> its not as good but still fine
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[21:29] <jcoxon> right, permission is through, so we are all go
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[21:29] <Laurenceb> hi
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[21:34] <rjharrison> Awsume, I'm getting excited now that it may actually happen
[21:34] <rjharrison> Have foundation exam at 1.30
[21:34] <jcoxon> haha
[21:35] <jcoxon> ooooo good luck
[21:35] <jcoxon> its pretty damn easy
[21:35] <rjharrison> Yep my thoughts too
[21:35] <jcoxon> took me under 5 mins to do
[21:35] <rjharrison> And probably 99 or 100%
[21:35] <jcoxon> 100
[21:35] <jcoxon> :-d
[21:35] <jcoxon> ops
[21:35] <jcoxon> :-D
[21:36] <rjharrison> There is always that weird question
[21:37] <rjharrison> If you can find someone to track in the car on Sunday that would be cool. Driving and tracking at the same time can be tricky
[21:37] <jcoxon> yeah, we can work out once we are all assembled
[21:37] <rjharrison> We'll see whos up for the chase
[21:37] <jcoxon> i think fergus is coming along
[21:37] <rjharrison> Great
[21:37] <jcoxon> our car can't take any more passengers
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[21:38] <rjharrison> I'll bring the landcruser as last time I ended up driving around fields and wetlands to retrive and you're in the landy
[21:38] <jcoxon> http://www.landrovercentre.com/image/Lightweight.jpg
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[21:38] <rjharrison> Nice
[21:39] <jcoxon> reckon could mount a yagi in the back :-D
[21:39] <natrium42> rjharrison, any luck with the panoramas?
[21:39] <rjharrison> I stood out the sun roof tracking my payload
[21:40] <rjharrison> A pit better. I'm missing the central data but I can do it now
[21:40] <jcoxon> while moving!?!
[21:40] <rjharrison> Pictures are better quality
[21:40] <rjharrison> jcoxon: Yep. Not more than 60 though
[21:40] <rjharrison> 40 actually
[21:40] <natrium42> jaja
[21:40] <natrium42> *haha
[21:40] <rjharrison> I'm not that mad
[21:40] <jcoxon> aarrghgh
[21:41] Action: Laurenceb gets his prius out
[21:41] <rjharrison> We were on private land. More of a huge estate
[21:41] <jcoxon> fair enough
[21:41] <rjharrison> Not hairing it around country lanes
[21:42] <jcoxon> the permission for EARS is now until may next year
[21:42] <natrium42> lol, i should get a flagpole antenna --> http://www.dxengineering.com/pdf/flagpole_antenna.pdf
[21:43] <natrium42> neighbours can't tell me anything then, since that would make them unpatriotic :P
[21:43] <rjharrison> Whicked, it's aonly a bit futher down the road from my potential launch site so I'm going to have to rethink. Infact i think there is probably enough options
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[21:43] <rjharrison> natrium42: i like it. O
[21:44] <jcoxon> hey RocketBoy
[21:44] <rjharrison> Eveing RocketBoy
[21:44] <rjharrison> Just going to get a beer
[21:44] <RocketBoy> hi guys
[21:46] <jcoxon> RocketBoy, i'm all set
[21:46] <jcoxon> for sunday that is
[21:46] <RocketBoy> I now have a shiny new permit for Elsworth round to 3rd May 09
[21:46] <jcoxon> :-D
[21:46] <Laurenceb> nice stuff
[21:46] <Laurenceb> hopefully we can launch the aersol sampler at last over christmas
[21:47] <RocketBoy> sounds fine
[22:12] <RocketBoy> BBL
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[23:27] Action: Laurenceb has just finished modifying the rogallo baord for hopefully the final time
[23:28] <Laurenceb> I've swapped over the servo, added an Rx lead and an Rx led
[23:28] <Laurenceb> just need an rc set now :-/
[23:30] <RocketBoy> night
[23:30] <Laurenceb> cya
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[23:48] <Laurenceb> hmm ebay isnt too good if you want a complete RC set
[23:48] <Laurenceb> I might try a model shop tomorrow
[23:51] <Laurenceb> anyone know a good place to pick up fairly cheap RC kit? ie <£50
[00:00] --- Sat Nov 1 2008