highaltitude.log.20090703

[00:00] <Laurenceb> I was looking at using T300 CF tube for a pressurised rocket
[00:09] <SpeedEvil> That, and I'm looking at building a big freezer cabinet.
[00:09] <SpeedEvil> Fun.
[00:13] <SpeedEvil> Hmm. Raw tow isn't that much.
[00:13] <SpeedEvil> http://cgi.ebay.co.uk/Pyrofil-Carbon-Fiber-12k-Tow-4kg-Bobbin-TR50S12LA1-Yarn_W0QQitemZ110404435794QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item19b49dff52&_trksid=p3286.m63.l1177&_trkparms=240%3A1318|301%3A1|293%3A1|294%3A50
[00:14] <SpeedEvil> at least on ebay
[00:15] <Laurenceb> I'm not sure how things develop as you move to really thin carbon fibre
[00:15] <Laurenceb> ideally for a pumped rocket youd use ~0.2mm CF instead of aluminium sheet
[00:16] <SpeedEvil> yeah - tey won't work for that
[00:16] <SpeedEvil> oh
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[00:24] <SpeedEvil> hmm. Above is prepeg tow.
[00:24] Action: SpeedEvil ponders.
[00:37] <Laurenceb> getting moulding made up can be a pain
[00:37] <Laurenceb> - wooden
[00:40] <SpeedEvil> Yeah - it's probably easier than trying to DIY though
[00:40] <SpeedEvil> I do have a router-table - but with multiple profile passes on a bit of wood, ...
[00:40] <Laurenceb> sure, floor mounted routers ect are kind of expensive
[00:40] <Laurenceb> nice
[00:41] <Laurenceb> the bunch of 16 year olds at my local timber yard seem to be incapable of doing anything with greater than +-5mm accuracy
[00:42] <SpeedEvil> Yeah - I'd have to actually be there and explain that I'm not paying for stuff outside this spec - can you do it?
[00:43] <Laurenceb> its usually a case of you walk in an everyones smoking or something, then they all stop and stare at you... then they say they might do it after lunch or something
[00:43] <Laurenceb> which means 2 days
[00:43] <Laurenceb> come back and they screwed up
[00:44] <Laurenceb> thats my experience of timber merchants
[00:44] <Laurenceb> and dont even try it if your female
[00:45] <SpeedEvil> Yeah.
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[01:30] <Laurenceb> looks like the viscous losses are about three orders of magnitude too high in a centrifugal pump
[01:31] <SpeedEvil> hmm
[01:31] <SpeedEvil> they won't scale well I suppose, yeah
[01:31] <SpeedEvil> shear rate will go way down as size goes up
[01:32] <Laurenceb> space propulsion analysis suggests piston pumps or other techniques for <5KN thrust
[01:33] <Laurenceb> alternative is a gearbox
[01:33] <Laurenceb> but thats way too heavy
[01:36] <SpeedEvil> belt drive can be moderately light
[01:36] <SpeedEvil> but that boosts the size of the pump too
[01:37] <Laurenceb> hmm if you design it carefully you can avoid some of the shear
[01:37] <Laurenceb> but its still going to kill the efficiency
[01:37] <Laurenceb> it'd be hard to reach even 50%
[01:38] <Laurenceb> clearly one of the reasons theres serious work going into piston(less) pumps
[01:43] <SpeedEvil> I suppose in principle, a roton-esque design
[01:43] <SpeedEvil> but that raises more issues
[01:48] <Laurenceb> I guess a double way piston pumping fuel and oxidiser and running of peroxide decomposition is the best bet
[01:48] <SpeedEvil> possibly
[01:49] <Laurenceb> if the catalyst is hot itll be very fast
[01:49] <Laurenceb> maybe an electric preheater
[01:50] <Laurenceb> and two units to allow for attitude control as well
[01:50] <Laurenceb> run at maybe 100Hz
[01:53] <Laurenceb> peroxide attitude control thrusters can easily respond that fast
[01:57] <Laurenceb> have a peroxide pump built in as well for the stuff that powers it
[02:11] <Laurenceb> oops did it wrong
[02:11] Nick change: KingJ -> kingj
[02:11] <Laurenceb> ok 90% is pretty feasible
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[07:57] <DanielRichman> ping sbasuita
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[09:47] <jcoxon> morning all
[10:15] <jcoxon> wooohoo our xbox has returned from it being fixed for red ring of death
[10:36] <SpeedEvil> hmm. http://www.myhdl.org/doku.php/why
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[11:28] <gordonjcp> SpeedEvil: interesting
[11:29] <SpeedEvil> (python->chips)
[11:29] <gordonjcp> yeah
[11:30] <gordonjcp> urgh, I need to try and get my head around Eagle
[11:30] <SpeedEvil> Or just use pcb
[11:30] <gordonjcp> it says something for the state of PCB CAD when I'm seriously considering hand-drawing a board with about 150 devices because it's just easier
[11:30] <SpeedEvil> have you tried pcb?
[11:30] <SpeedEvil> I found it not too bad at all
[11:31] <gordonjcp> I'll give it a go
[11:31] <gordonjcp> the pcb house I'm planning on using wants Eagle format though
[11:31] <SpeedEvil> It will do gerber output
[11:31] <SpeedEvil> and many other thingss
[11:31] <gordonjcp> okay
[11:32] <SpeedEvil> I've only ued it 'in anger' for a 250 hole or so eurocard sized thing
[11:32] <SpeedEvil> 2 layer
[11:32] <gordonjcp> this is a mostly-analogue device
[11:33] <SpeedEvil> yeah - this was an ECU
[11:33] <SpeedEvil> (That I still haven't gotten built)
[11:34] Nick change: kingj -> KingJ
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[16:17] Nick change: G8KHW-2 -> RocketBoy
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[17:00] <Laurenceb> hi
[17:22] <Laurenceb> http://www.solarcomposites.com/composites/compositecarbon.html#24K
[17:24] <Laurenceb> thats 4.1GPa XD
[17:25] <SpeedEvil> Fun
[17:25] <SpeedEvil> I'm still trying to come up with fun ways to use the cheap tow I found on ebay
[17:26] <Laurenceb> I was looking at pintle injectors
[17:26] <Laurenceb> you can have just one injector and it doubles as a throttle
[17:27] <SpeedEvil> yeah
[17:27] <SpeedEvil> well - it's one moving part - but two injectors, yeah
[17:27] <Laurenceb> will nicely fit in the center of a spun aluminium alloy bulkhead
[17:28] <Laurenceb> another idea - make a tube from bent CF sheet
[17:29] <Laurenceb> http://www.carbonology.com/carbon-fibre-sheet-02mm-0008-thickness-c-2_49.html <- like that
[17:29] <SpeedEvil> that ssolves some of the fixturing issues
[17:30] <SpeedEvil> All you need is a simple jig to clamp a section in a cylindrical egment while the glue sets, and you're done
[17:31] <SpeedEvil> flat section if you're not being optimal
[17:33] <Laurenceb> it'd be good for a pumped design
[17:33] <Laurenceb> pumped using reciprocating piston pumps is going to be the lightest you can get I think
[17:34] <Laurenceb> tank pressurised to 20PSI or so with liquid CO2
[17:34] <Laurenceb> then use H2O2 decomposition to drive the pump
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[17:34] <Laurenceb> should be able to get >95% fuel fraction
[17:35] <SpeedEvil> hmm
[17:36] <SpeedEvil> sounds plausile
[17:36] <Laurenceb> only tricky bit is H2O2 injection
[17:36] <Laurenceb> I cant work out how youd do that
[17:36] <SpeedEvil> little vane pump?
[17:37] <SpeedEvil> you mean into the piston pump?
[17:37] <Laurenceb> yes
[17:38] <Laurenceb> maybe solenoid pump injectors
[17:40] <Laurenceb> needs about1% of the pumped volume
[17:55] <Laurenceb> hmm you dont actually have to pump anything
[17:56] <Laurenceb> you can use an "airlock" type arrangement to inject
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[19:03] <edmoore> hi RocketBoy
[19:04] <edmoore> re: your email, I'm quite sure I read it more explicitly on the sparkfun website a bit ago, but now the nearest I can find is: http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=127
[19:05] <edmoore> "The Lassen iQ is a classic. But its days are numbered."
[19:05] <edmoore> "This was one of the first low-cost GPS modules. These sold really well and we continue to carry it to cover legacy demand."
[19:05] <edmoore> "This was a great module in its day. The iQ is slowly working its way down the retirement curve."
[19:07] <edmoore> I can't however find an explicit declaration that it's being discontinued
[19:15] <RocketBoy> edmoore: ta - the info i heard was a bit more specific - like SF wern't buying any more
[19:16] <edmoore> I think that might be a change of policy from SF
[19:16] <edmoore> as I am pretty sure I read that they were letting them go till they're gonr
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[19:27] <Laurenceb> good riddance
[19:27] <Laurenceb> ublox5 is better
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[19:35] <Laurenceb> sure there will be plenty going around for some time to come
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[19:43] <RocketBoy> edmoore: ta - i'll see what Dimond Point say about the IQ
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[19:46] <rjharrison_iphon> Hi all
[19:46] <rjharrison_iphon> On way to Reading
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[19:47] <RocketBoy> I hope your not driving ;-)
[19:49] <Laurenceb> that should read crash quit
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[00:00] --- Sat Jul 4 2009