[00:00] <stilldavid> yeah, it was pretty inexpensive to start, and I bought it used from an online retailer. not too worried about keeping it in the car.
[00:00] <SpeedEvil> ah
[00:00] <stilldavid> this whole project has opened up so much for me to play with, though, that's why it's fun :)
[00:01] <stilldavid> playing with the gumstix, learning python, getting my HAM, I could go on...
[00:01] <SpeedEvil> http://cgi.ebay.co.uk/YAESU-VR500-COMUNICATIONS-RECIEVER-BOXED-AS-NEW_W0QQitemZ140327274264QQcmdZViewItemQQptZUK_ConsumerElectronics_SpecialistRadioEquipment_SM?hash=item20ac284718&_trksid=p3286.c0.m14&_trkparms=65%3A12|66%3A2|39%3A1|72%3A1690|240%3A1318|301%3A0|293%3A1|294%3A50
[00:01] <SpeedEvil> i'm unsure of
[00:02] <SpeedEvil> if it covers 433, and has decent noise figure - it does do SSB
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[00:07] <stilldavid> I think I'm going to look at handheld transceivers I can take on backpacking trips and the like
[00:08] <Laurenceb> I've got an icom pcr-1000
[00:08] <Laurenceb> but it needs power
[00:09] <Laurenceb> RocketBoy lent me a motorcycle battery that ran it ok
[00:09] <stilldavid> I'm over the pond.
[00:09] <SpeedEvil> ah
[00:15] <stilldavid> as far as yaesu, looks like the only handheld that does ssb recieve is the vx-8r at ~$370 usd
[00:15] <SpeedEvil> vr-500
[00:16] <stilldavid> transceiver :-/ Something I can use in the future
[00:17] <SpeedEvil> http://www.grove-ent.com/VR500TECHSPECS.htm
[00:17] <SpeedEvil> ah
[00:28] <stilldavid> http://www.universal-radio.com/catalog/ht/0066.html
[00:29] <stilldavid> that might be the one.
[01:14] <SpeedEvil> though doesn't seem to state sensitivity in SSB at 433 - however - yes - looks OK
[01:15] <SpeedEvil> checkout the PC lead - and protocols
[01:17] <stilldavid> PC lead?
[01:18] <stilldavid> ah, the DB9 cabe
[01:18] <SpeedEvil> I mean - if you ever might want to control it by
[01:18] <SpeedEvil> PC - you need to check to see if the protocols are sane
[01:35] <stilldavid> Might just go for the RX after all, it's a lot cheaper :-/
[01:36] <stilldavid> just came across a list of all reg'd microwave towers in my area. lots of companies and their assorted frequencies they're using
[01:37] <stilldavid> lots of SSB data from the sound of it :) water, electric, wireless companies...
[01:59] <Laurenceb> hmm its just about possible with two hybid stages and a peroxide third stage
[02:00] Nick change: KingJ -> kingj
[02:01] <SpeedEvil> I think unfortunately, you want to stay far away from 'just about possible'
[02:02] <Laurenceb> yeah
[02:02] <Laurenceb> but with hybrid the stages are quite short
[02:03] <Laurenceb> and unfortunately burn out will be hard to control, so you can go for horizontally stakced stages
[02:03] <Laurenceb> you want to go for two vertical ones, which allows the amount of propellant to be varied
[02:10] <SpeedEvil> barring the shuttle solution.
[02:11] <SpeedEvil> cut large holes in the chamber to ensure prompt thrust decay
[02:11] <SpeedEvil> oh - hybrid - not solid
[02:11] <SpeedEvil> sorry - tired.
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[07:39] <mc_-> http://news.bbc.co.uk/nolpda/ukfs_news/hi/newsid_7862000/7862827.stm?
[07:39] <mc_-> Laurenceb?
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[07:46] <mc_-> hi natrium
[07:54] <natrium42> yo
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[09:53] <Laurenceb> hi mc_
[09:53] <Laurenceb> interesting article, I hadnt heard of that
[09:55] <mc_-> you around today?
[09:56] <Laurenceb> online or irl ?
[09:57] <mc_-> in person? I can drive over to the uni
[09:57] <Laurenceb> guess so
[09:57] <Laurenceb> theres not much to see :P
[09:57] <Laurenceb> and my room is a tip :P
[09:58] <mc_-> is there somewhere good to meet?
[09:58] <Laurenceb> but yeah I'm free this afternoon if you want to meet up
[09:58] <Laurenceb> we could head to a pub maybe?
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[10:36] <edmoore> mornin all
[10:41] <SpeedEvil> ornin
[10:44] <edmoore> rnin SpeedEvil
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[11:06] <edmoore> yo jcoxon
[11:07] <jcoxon> hey edmoore
[11:07] <edmoore> all well?
[11:07] <edmoore> what's happening atm?
[11:07] <jcoxon> yes
[11:07] <edmoore> have slightly lost track
[11:07] <jcoxon> just having a revision break
[11:07] <jcoxon> ummm in the world of balloons?
[11:07] <jcoxon> not much really
[11:07] <edmoore> also we need to start throwing dates about for a UKHAS garden party/bbq
[11:08] <jcoxon> indeed
[11:08] <jcoxon> i'm away from teh 27th july till 3rd october just to warn
[11:09] <edmoore> what doin?
[11:09] <jcoxon> my elective
[11:09] <edmoore> in the US or AAAAAAAAAAAAAAAARRRGGH
[11:09] <edmoore> of*
[11:09] <jcoxon> nope, Glasgow for 3 weeks fighting swineflu then 6 weeks in Ghana in a small mission hospital
[11:10] <edmoore> churcill has 4 cases of swine flu
[11:10] <jcoxon> hoping to launch 2 flights before i go
[11:10] <Laurenceb> seriously?
[11:10] <edmoore> yep
[11:10] <Laurenceb> crazy
[11:10] <jcoxon> 1 latex floater flight and also peg vI again for a bit of sstv image fun
[11:10] <Laurenceb> be careful!
[11:10] <edmoore> floater?
[11:11] <edmoore> hole in t'bottom
[11:11] <edmoore> ?
[11:11] <jcoxon> yup
[11:11] <jcoxon> but with a one use valve
[11:11] <Laurenceb> valve?
[11:11] <Laurenceb> servo opertated?
[11:11] <jcoxon> to close the hole when we reach approx neutral bouancy
[11:11] <Laurenceb> jcoxon: whats the hardware?
[11:12] <jcoxon> Laurenceb, ummm not servo, cutdown operated
[11:12] <jcoxon> a rough idea: http://www.flickr.com/photos/jcoxon77/3641504463/
[11:12] <jcoxon> Laurenceb, just gps, avr and radiometrix
[11:12] <jcoxon> cut the main line so that the payload then pulls the second line tight closing the valve
[11:13] <Laurenceb> so you overfill
[11:13] <Laurenceb> then it slowly loses lift until it reaches zero vertical v?
[11:13] <Laurenceb> cunning
[11:13] <jcoxon> yeah then we close the valve and float...
[11:14] <Laurenceb> the tricky bit is stopping it from tangling
[11:14] <jcoxon> thats a good point
[11:14] <jcoxon> didn't think of that
[11:14] <edmoore> jcoxon - sstv v2 will be cool
[11:14] <jcoxon> think it'll be a fun mission - good test of the DL listener as well
[11:14] <Laurenceb> if you have the mechanism mounted directly onto the payload it'll work
[11:14] <edmoore> might be worth taking the antenna to an SWR meter
[11:15] <edmoore> and making sure all that juice gets radiated by the antenna
[11:15] <jcoxon> edmoore, yeah, going to have 2 radios this time
[11:15] <Laurenceb> jcoxon: I made a working servo valve
[11:15] <Laurenceb> with polypipe ball valve
[11:15] <jcoxon> one directly attached to the gumstix for sstv
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[11:15] <jcoxon> and then another for rtty etc
[11:17] <Laurenceb> jcoxon: if you make that vavle an integral part of the payload
[11:17] <Laurenceb> then it should work ok
[11:18] <jcoxon> the flight is really a 'fun' experiment flight
[11:18] <jcoxon> to see if it actually works
[11:19] <Laurenceb> also you need a seperate constriction hole - to limit the flow
[11:19] <Laurenceb> as o rings arent avaliable easily in stupidly small sizes
[11:20] <jcoxon> i think i'm going to go with my design
[11:20] <Laurenceb> but its pretty easy to built with some pipe and a couple of resistor cutdowns
[11:20] <Laurenceb> hmm I think it'll tangle
[11:21] <Laurenceb> also you'll never get a decent leak rate without a ~0.5mm or less hole
[11:21] Nick change: kingj -> KingJ
[11:21] <Laurenceb> at a first guess
[11:21] <jcoxon> Laurenceb, how could i work out what size hole to have?
[11:21] Action: Laurenceb forgets the equation
[11:21] <jcoxon> is there a way to calculate it?
[11:21] <Laurenceb> ok, first thing you need is the pressure in the envelope
[11:22] <Laurenceb> you can work that out using youngs modulus for latex
[11:22] <Laurenceb> then work out the tension in the latex... and derive the pressure in the envelope
[11:22] <Laurenceb> forgotten the name of the equation for the leak through the hole
[11:22] <Laurenceb> wikipedia can probably help
[11:23] <Laurenceb> if you want I'll write some sim code for you this evening
[11:23] <jcoxon> read somewhere that roughly its about 5mmHg backpressure from the balloon
[11:23] <jcoxon> Laurenceb, that would be really helpful if you could
[11:23] <Laurenceb> as leak rate pressure ect is all interelated
[11:23] <jcoxon> my maths isnt great
[11:23] <Laurenceb> ok... *goes to wikipedia*
[11:23] <SpeedEvil> I think it's something really simple
[11:24] <SpeedEvil> like density*outflow speed = pressure
[11:24] <SpeedEvil> approximately
[11:24] <Laurenceb> yeah for order of mag...
[11:24] <Laurenceb> lets do that
[11:24] <SpeedEvil> at least for weell subsonic flow
[11:25] <jcoxon> and i was thinking the valve activation logic should be:
[11:25] <SpeedEvil> 5mmHg is what - 1000Pa?
[11:25] <Laurenceb> 670
[11:25] Nick change: KingJ -> kingj
[11:26] <jcoxon> > 18km to be well clear of planes etc
[11:26] <jcoxon> actually thats too high
[11:26] <jcoxon> > 16km
[11:26] <SpeedEvil> if this is for 15Km, density will be around 100g/m^3 for air, so ..
[11:26] <jcoxon> and an ascent rate of < 1m/s
[11:27] <SpeedEvil> 6.5g/m^3 for He
[11:27] <Laurenceb> yeah its going to have to be around a square mm or less I think
[11:27] <SpeedEvil> The low density means it goes quite fast
[11:27] <Laurenceb> as you ascend the defferential pressure decreases
[11:28] <SpeedEvil> not ure of that
[11:28] <SpeedEvil> I don't think you can assume the latex is close to linear
[11:28] <SpeedEvil> But probably somewhat, yes.
[11:29] <SpeedEvil> I'm not sure what effect really cold temps have on its reluctance to expand
[11:30] <Laurenceb> I'd say <1mm square at any rate
[11:30] <jcoxon> Laurenceb, really?
[11:31] <Laurenceb> yeah
[11:31] <jcoxon> that said it makes sense
[11:31] <jcoxon> bill brown's experiements were 1/16th inchc
[11:31] Nick change: kingj -> KingJ
[11:32] <jcoxon> http://nearspaceventures.com/gpsl2008/GPSL2008.ppt
[11:40] <jcoxon> on a solenoid valve is the orifice size a diameter?
[11:40] <SpeedEvil> yes
[11:40] <Laurenceb> yes
[11:40] <SpeedEvil> it's the equivalent apature to the flow resistance of the solenoid
[11:40] <Laurenceb> use your sensortechnics valve
[11:41] <jcoxon> thats what i'm thinking
[11:41] <jcoxon> its orifice is 1.143mm
[11:41] <jcoxon> so 4.1 mm2
[11:42] <SpeedEvil> probably diameter
[11:42] <jcoxon> oops
[11:42] <Laurenceb> 1.02
[11:42] <jcoxon> yeah
[11:42] <Laurenceb> *1.0260826
[11:43] <Laurenceb> may just work
[11:43] <jcoxon> lets think about the flight logic
[11:43] <jcoxon> would it be worth keeping it closed till say above 10km
[11:43] <jcoxon> then opening it
[11:43] <jcoxon> till vertical v is ~0
[11:44] <jcoxon> then closing it and floating
[11:44] <Laurenceb> measure the escent rate roughtly on takeoff
[11:44] <Laurenceb> then see if you need to start dumping immediately as someone screwed up on the inflation
[11:45] <Laurenceb> continue measuring so you can calculate a dump period to do near the cruise altitude
[11:45] <jcoxon> so have an 'ascent' stage which aims to have a ascent rate of say 3m/s
[11:45] <Laurenceb> no
[11:45] <Laurenceb> best to ascend as fast as poss
[11:45] <jcoxon> oh right
[11:45] <jcoxon> then calculate dump period for later
[11:46] <Laurenceb> yeah
[11:46] <jcoxon> once we are safely out of the way of planes and JS
[11:46] <Laurenceb> then dump as 50% of that
[11:46] <Laurenceb> then measure again ect
[11:46] <Laurenceb> fine tune until your level
[11:46] <Laurenceb> but only go to that stage once you quite high up
[11:47] <Laurenceb> you could go for the target ascent rate as well
[11:47] <Laurenceb> but have it undefined below say 12Km
[11:47] <jcoxon> don't want to complicate anything
[11:47] <Laurenceb> if you want to level off at 18km say
[11:47] <Laurenceb> code can be as complex as you want
[11:48] <Laurenceb> thats the beauty of it
[11:48] <jcoxon> then only issue would be that we wouldn't have enough time to dump the gas before reaching burst
[11:48] <Laurenceb> yeah
[11:48] <Laurenceb> theres a few things to consider
[11:49] <jcoxon> i've got 2 valves so i don't mind using one of them
[11:51] <Laurenceb> I'll have a go as some sim code for you
[11:51] <jcoxon> cool
[11:51] <Laurenceb> SpeedEvil: I came up with a new rocket design
[11:51] <jcoxon> would be good to fly this after the 8th july (thats my last exam)
[11:51] <Laurenceb> two stage hybrid with 3rd monoprop stage
[11:51] <Laurenceb> ok
[11:52] <Laurenceb> 108Kg GLOW, 1Kg cubesat payload to 630Km circular orbit
[11:54] <SpeedEvil> balloon 0>
[11:55] <SpeedEvil> ?
[11:55] <Laurenceb> 20Km balloon
[11:55] <Laurenceb> 150mm CF tube with vertically stacked stages
[11:57] <SpeedEvil> hmm
[11:57] <Laurenceb> I think graphite nozzle is the best, by a small margin, and you can use jet vanes to do TVC
[11:57] <Laurenceb> stainless jet vanes work
[11:57] <SpeedEvil> burn + coast on the first?
[11:57] <Laurenceb> yeah
[11:58] <SpeedEvil> graphite vanes are quite cheap
[11:58] <Laurenceb> but harder to machine
[11:58] <jcoxon> http://news.bbc.co.uk/1/hi/uk/8110001.stm
[11:59] <jcoxon> 70k ft - pah
[12:00] <Laurenceb> heh
[12:01] <jcoxon> right i'll bbl - need to do some more revision
[12:01] <jcoxon> thanks for the help Laurenceb and SpeedEvil
[12:05] <jcoxon> wow this thurs would be a great day to launch
[12:05] <jcoxon> oops, shuld go...
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[12:11] <Laurenceb> I found that RS sell some interesting ceramics
[12:12] <Laurenceb> theve got a rigid insulation material thatd work for mounting the nozzle and some high temperature blanket for surrounding the fuel
[12:12] <SpeedEvil> hmm
[12:13] <Laurenceb> you need about 2mm of blancket to line the fuel section
[12:14] <Laurenceb> I was thinking glue it to the inside of the CF and smear the propellant charge with epoxy
[12:15] <Laurenceb> that way small isolated sections of propellant wont break off and block the nozzle
[12:21] <Laurenceb> you only need 3 jet vanes which is nice
[12:23] <SpeedEvil> Or 1, if you're silly
[12:23] <SpeedEvil> (aforementioned rotating vane)
[12:23] <Laurenceb> jet vanes are light and you can use servos to drive them
[12:23] <SpeedEvil> 4, if you cant them appropriately, give you roll control
[12:24] <Laurenceb> so do three
[12:24] <SpeedEvil> hmm - true - but adds complexity to the control laws
[12:24] <Laurenceb> erm....
[12:25] <Laurenceb> a few flops
[12:25] <SpeedEvil> true
[12:26] <Laurenceb> http://news.bbc.co.uk/1/hi/technology/8063975.stm
[12:26] <Laurenceb> arduino, where electronics became really really gay
[12:26] Action: Laurenceb cringes
[12:26] <SpeedEvil> A) It's painting by numbers.
[12:27] <SpeedEvil> B) It lets people learn stuff, and go on from there.
[12:30] <Laurenceb> you can do three jet vanes for <200grams
[12:32] <SpeedEvil> I think I was looking at around 50g for my single solution
[12:32] <SpeedEvil> one big bearing going right round the combustion chamber - I found a really light one - and a single motor.
[12:33] <Laurenceb> interesting
[12:33] <Laurenceb> but its pretty insignificant
[12:33] <SpeedEvil> yeah
[12:33] <Laurenceb> the graphite nozzle is 300 grams
[12:33] <Laurenceb> then the alu mount is ~100
[12:33] <Laurenceb> so 150 grams isnt much
[12:34] <SpeedEvil> yeah.
[12:34] <Laurenceb> hmm this is interesting - my code screws up with different timesteps
[12:34] <Laurenceb> I think the start of the gravity turn is really critical
[12:35] <Laurenceb> theres a weird velocity feedback effect that screws up at longer timesteps
[12:35] <Laurenceb> the nice thing with a gravity turn is that the cruise after first stage burnout is stabilised by the residual atmosphere
[12:37] <Laurenceb> you can blow the first stage off from the second with vertical stacking
[12:37] <Laurenceb> just fire the motor
[12:38] <Laurenceb> the only tricky bit really is the tunable He regulator
[12:39] <SpeedEvil> solenoid valve?
[12:39] <Laurenceb> maybe
[12:39] <SpeedEvil> rather than proper?
[12:39] <Laurenceb> solenoid valve + pressure sensor
[12:39] <Laurenceb> I allowed 100grams so that may be enough
[12:41] <Laurenceb> then theres a blow off cap over the injector face
[12:43] <Laurenceb> - well rip off in four sections cap, that then gets burnt up
[12:44] <Laurenceb> bbl
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[14:45] <Laurenceb> hi edmoore
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[14:49] <edmoore> afternoon all
[14:49] <edmoore> hi Laurenceb
[14:50] <Laurenceb> what are you up to these days?
[14:50] <Laurenceb> you finished exams ages ago?
[14:54] <Laurenceb> working on 4th year project?
[14:56] <edmoore> finished 3rd year projects last week
[14:56] <edmoore> then have been to france and had may week
[14:56] <edmoore> summer work i guess starts tomorrow
[14:56] <edmoore> thought the other guys are probably going to start after graduation
[15:00] <Laurenceb> cool
[15:01] <Laurenceb> oh I didnt realise there was a third year project
[15:01] <Laurenceb> good luck with results
[15:01] <Laurenceb> brb
[15:01] <edmoore> that was the image compression etc
[15:01] <edmoore> ta
[15:05] <rjharrison> http://news.bbc.co.uk/1/hi/uk/8110001.stm
[15:06] <rjharrison> Not that high really
[15:07] <rjharrison> BTW Pyros rock. Using 1.5v AAA to fire will move to cap in a bit
[15:07] <SpeedEvil> :)
[15:19] <edmoore> they do!
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[16:27] <edmoore> jcoxon: when do you go oop north again?
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[16:34] <jcoxon> edmoore, 26th july
[16:34] <edmoore> cool beas
[16:35] <jcoxon> just to say thurs looks like an amazing launch day
[16:35] <jcoxon> :-)
[16:35] <jcoxon> not that i'm available
[16:41] <edmoore> so it does
[16:47] <jcoxon> so edmoore whats the summer job?
[16:47] <jcoxon> martlet?
[16:47] <edmoore> staying here
[16:47] <edmoore> working on martlet and t'other project
[16:48] <jcoxon> auto directing yagi?
[16:48] <edmoore> and perhaps a bit on hobble
[16:48] <jcoxon> :-)
[16:48] <edmoore> nope, esa
[16:48] <jcoxon> oh cool
[16:48] <jcoxon> sounds fun
[16:48] <jcoxon> i'd like a summer of 'projects'
[16:48] <edmoore> I don't know how far the Benz (ben and ben) have got with the auto yagi. it may be that we just grab it off them and spend a day or two whipping it into service
[16:49] <jcoxon> cool cool
[16:50] <jcoxon> wow the last time i launched a payload was last november
[16:50] <jcoxon> i need t oget organised!
[16:51] <edmoore> helium awaits
[16:52] <edmoore> so what's the next one - float or sstv?
[16:52] <jcoxon> i'm not sure really
[16:53] <jcoxon> which one will be most fun?
[16:53] <jcoxon> sbasuita, ping
[16:59] <edmoore> gimme 2 secs?
[16:59] <edmoore> no question mark needed, even
[17:00] <jcoxon> :-)
[17:05] <edmoore> so the valve would be cool, I think
[17:05] <edmoore> I have a personal interest in valve performance, it must be said
[17:06] <jcoxon> yeah
[17:06] <jcoxon> i think the valve is a little bit simpler
[17:06] <jcoxon> as in not a gumstix mission
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[17:08] <jcoxon> Laurenceb was saying that he reckons we'll need a very small hole
[17:31] <Laurenceb> I was indeed
[17:32] <Laurenceb> I think the sensortechnics valve will do, but its not that good a vent
[17:32] <jcoxon> i'm wondering if just going for the original idea might be better
[17:32] <Laurenceb> as you get higher the density decreases, but that will increase the flow, however the differential pressure also decreases
[17:33] <Laurenceb> youd need to be pretty sure of the leak rate, as itd be set before launch
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[17:34] <Laurenceb> oh wow starchaser are working on hybrid motors
[17:36] <Laurenceb> including peroxide/acrylic
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[17:38] <Laurenceb> hi there mc_-
[17:39] <Laurenceb> look what I found: http://starchaser.co.uk/index.php?view=news_latest&mgroup=news
[17:39] <mc_-> hi again
[17:41] <mc_-> I used to be part of that group
[17:42] <mc_-> they didnt know what theyre doing
[17:42] <Laurenceb> interesting
[17:42] <Laurenceb> I dont understand how they fund it
[17:42] <Laurenceb> seem to drive around the country all the time with that rocket on a lorry
[17:43] <mc_-> think they have got some grants
[17:43] <Laurenceb> they are working on peroxide/polymer now, but if they dont know what they're doing :P
[17:43] <SpeedEvil> easy
[17:43] <SpeedEvil> the rocket is full of drugs.
[17:43] <Laurenceb> haha
[17:44] <Laurenceb> its got floodlights and cannabis inside
[17:44] <Laurenceb> they sell it to the schoolkids
[17:45] <Laurenceb> http://starchaser.co.uk/images/gallery/htp5/03.jpg <- lol @ rs boxes
[17:46] <Laurenceb> http://starchaser.co.uk/images/gallery/htp5/07.jpg <- cardboard tubes?
[17:48] <mc_-> developing motors isnt too expensive
[17:49] <Laurenceb> IMO best to find as much data from papers
[17:49] <Laurenceb> no use reinventing the wheel, which is what a lot of people do, and mainly what they seem to be doing
[17:49] Action: SpeedEvil presents Laurenceb with a septagonal wheel.
[17:50] <mc_-> i was at their launch on Dartmoor when they burnt the moor...
[17:50] <Laurenceb> if you can get to the point where you dont have to completely redesign your hardware, thats about the best you can hope for
[17:50] <Laurenceb> you'll probably need to do a few revisions
[17:50] <SpeedEvil> Especially if you can - ideally - keep the hard parts constant.
[17:51] <Laurenceb> but you want to avoid the stage of building experiments just to see what it does
[17:51] <SpeedEvil> IMU/GPS/...
[17:51] <Laurenceb> I was thinking motor wise
[17:51] <SpeedEvil> well - some of the hard parts
[17:51] <Laurenceb> hopefully IMU gps works first time
[17:51] <SpeedEvil> that too
[17:51] <mc_-> armadillo seem to redesign h/w often
[17:51] <Laurenceb> - obviously you test it a _lot_ on the ground
[17:52] <Laurenceb> armadillo are mucking about burning money for fun itd seem
[17:52] <SpeedEvil> and most importantly - have huge margins
[17:52] <Laurenceb> thats not going to be that possible
[17:52] <SpeedEvil> yeah - I was basically budgeting a whole extra stage as margin
[17:53] <SpeedEvil> So 5* the optimistic GLOW
[17:53] <Laurenceb> ISP magin is the hardest and most important
[17:53] <SpeedEvil> yeah
[17:53] <Laurenceb> I've seen simple stuff achieve 87% theoretical ISP
[17:54] <Laurenceb> so 290 what you can hope for
[17:54] <Laurenceb> but theres a lot to pre and post combustion chambers, chamber pressure, and flow rates
[17:55] <Laurenceb> lots of people claim 90% if you optimise it right
[17:55] <SpeedEvil> Especially for small motors, with low residence times, that seems optimistic
[17:56] <SpeedEvil> Seems easy ifyou've got a chamber the size of your car.
[17:56] <Laurenceb> yeah what does the standard ISP code assume for residence time?
[17:56] Action: SpeedEvil is jamming.
[17:56] <SpeedEvil> (raspberry)
[17:57] <Laurenceb> :P
[17:57] <SpeedEvil> well - to get that right - you really need to do the horribly hard stuff.
[17:57] <SpeedEvil> Drop size, flow-rate, mixture patterns, assymetries, ...
[17:57] <Laurenceb> yeah
[17:58] <SpeedEvil> easily doable for gas/gas thrusters maybe.
[17:58] <Laurenceb> a good thing about polymers over paraffin and aluminium powder is you dont have drops
[17:58] <SpeedEvil> maybe even solids
[17:58] <Laurenceb> the thing with 86% was only ~30cm long
[17:58] <Laurenceb> they put the low efficiency down to alu particles not fully combusting
[17:59] <SpeedEvil> this was with what?
[17:59] <Laurenceb> aluminium lithium hydride powder and polythene with 80% HTP
[18:00] <SpeedEvil> they stock AlLiH powder in B&Q? :)
[18:00] <Laurenceb> apparently they sourced a few barrels of powder
[18:01] <SpeedEvil> AlLiF is clearly superior.
[18:01] <Laurenceb> heh
[18:01] <SpeedEvil> ozone is a fun propellant
[18:01] <SpeedEvil> pity it's rather tricky to tame
[18:02] <Laurenceb> the bench scale paraffin hybrids I've seen have had pitiful efficiency
[18:02] <Laurenceb> around 60%
[18:03] <Laurenceb> you can see the paraffin droplets just fly out the back
[18:03] <Laurenceb> there was a nasa study that claimed 95% theoretical ISP was possible with a shuttle SRB scale one
[18:04] <Laurenceb> ISP of 370 with LOX and tubropump into the injector
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[18:04] <SpeedEvil> nice
[18:04] <Laurenceb> boosted the shuttle performance by miles
[18:04] <SpeedEvil> but yeah - bench scale seems likely to be problematic without some complications.
[18:04] <mc_-> how about a plastic fuel grain matrix with wax?
[18:05] <Laurenceb> - or tonnes even :P
[18:05] <mc_-> then the wax wont slump
[18:05] <Laurenceb> wax is a distraction as I see it
[18:05] <SpeedEvil> the problem is that if it melts - you have little control over the droplet size
[18:05] <Laurenceb> it burns too fast
[18:05] <SpeedEvil> the wax slumping isn't a problem
[18:05] <Laurenceb> and the ISP is little higher
[18:05] <SpeedEvil> if you have stuff added
[18:05] <SpeedEvil> fibres, and carbon black
[18:05] <Laurenceb> yeah
[18:06] <SpeedEvil> and if you have little control over the droplet size - it works very well in big things
[18:06] <SpeedEvil> but not so well if you have to have really tiny droplets, as your chamber is so small that it hasn't finished reacting the big drops when they get to teh back
[18:06] <Laurenceb> it worked well for the shuttle as they could have single port and keep a 100 second or more burn time
[18:07] <mc_-> how about a big chamber to burn everthing?
[18:07] <Laurenceb> thats the idea of a postcombustion chamber
[18:08] <mc_-> yes
[18:08] <Laurenceb> but your not going to build one thatd work for paraffin
[18:08] <mc_-> wax is cheap
[18:08] <SpeedEvil> mc_-: insulating it is then a problem
[18:08] <Laurenceb> the best you can hope for is one big enough to bost your ISP with polymer
[18:08] <SpeedEvil> mc_-: plus - you don't have room for a 20m long combustion chamber on a 2m rocket
[18:08] <Laurenceb> you use ablative liner that adds to the thrust
[18:09] <Laurenceb> but it still adds to the mass
[18:09] <mc_-> does isp matter so much for the early stages?
[18:09] <Laurenceb> as you need extra pressure vessle and magins on the ablative
[18:09] <mc_-> just scale it up instead
[18:09] <Laurenceb> not so much for the rist stage
[18:09] <Laurenceb> but you want to keep a common design
[18:09] <Laurenceb> to save costs
[18:10] <Laurenceb> then you can bulk order the parts for machining
[18:10] <mc_-> big and dumb is cheapest
[18:10] <Laurenceb> not when its balloon launched
[18:10] <mc_-> true
[18:10] <Laurenceb> and electronics and carbon fibre are relatively cheap
[18:11] <mc_-> what costs?
[18:11] <SpeedEvil> mc_-: scale it up is easy to ssay - but to get it to work using solely that philosophy means you at least need a launcher with many tons liftoff weight
[18:11] <Laurenceb> helium, envelope, CF tube, He cylinders
[18:11] <Laurenceb> my 2 stage design atm is maybe £5K realistically
[18:12] <mc_-> scale down the payload
[18:12] <SpeedEvil> mc_-: doesn't really help much
[18:12] <Laurenceb> 1Kg is the minimum you could sell
[18:12] <Laurenceb> 100mm cubesat
[18:12] <SpeedEvil> mc_-: you then run into other problems with scaling the rocket
[18:12] <Laurenceb> you could easily charge £100K to launch one
[18:13] <Laurenceb> bringing in £95K per launch
[18:13] <mc_-> a wax hybrid seems feasible to build
[18:13] <Laurenceb> wax is a distraction IMO
[18:14] <Laurenceb> acrylic and a lathe and you avoid all the issues inherant in small scale wax
[18:14] <SpeedEvil> speaking personally - I'd pay maybe 500 for a 100g 40*40*40 sat
[18:14] <Laurenceb> mm?
[18:14] <SpeedEvil> yes
[18:14] <mc_-> acrylic also seems good
[18:14] <Laurenceb> well that just covers the costs then :P
[18:15] <SpeedEvil> you can fit a lot in that sort of payload with mobile phone type stuff
[18:15] <mc_-> if you build a motor i can find somewhere to test it
[18:15] <Laurenceb> dartmoor ?
[18:15] <Laurenceb> :D
[18:16] <Laurenceb> I was pondering a cubesat for gps sounding
[18:16] <mc_-> or out at sea
[18:16] <Laurenceb> 100mm cubesat with 20 or so mini sats inside
[18:16] <Laurenceb> mc_-: ideally a barge, then you can launch the balloon from it
[18:17] <mc_-> barge or boat
[18:17] <Laurenceb> this 2 stage design neatly fits in a 20' shipping container
[18:17] <Laurenceb> but barges are expensive
[18:18] <Laurenceb> holy £"$$
[18:18] <Laurenceb> http://www.bristolharborgroup.com/commercial/stock_deck_barge_designs.html
[18:18] <Laurenceb> I'll take that back
[18:19] <Laurenceb> $10K for 120'x30'
[18:19] <Laurenceb> that is totally insane
[18:19] <Laurenceb> and shipping containers are £600
[18:20] <Laurenceb> enough room spare for a helipad and you have an affordable offshore evil james bond base for <$20K
[18:22] <Laurenceb> this is awesome, an evil seafortress
[18:23] <SpeedEvil> umm
[18:23] <SpeedEvil> I think you'll find that's for the design
[18:24] <Laurenceb> hmm
[18:24] <SpeedEvil> love to be wrong, but... :)
[18:24] <Laurenceb> heh
[18:25] Action: Laurenceb ponders shipping containers as barge building meterial
[18:29] <Laurenceb> http://www.wright-international.com/wil1989-fishfarmfeederbarge.php
[18:29] <Laurenceb> ^ ok you get rather less for your money
[18:30] <Laurenceb> that thing is enough to make my eyes bleed
[18:31] <Laurenceb> boats are pretty cheap really
[18:32] <Laurenceb> http://www.wright-international.com/wil1462-660teucontainerfeedership.php <-- I mean you could almost pay that for a very large house
[18:34] <RocketBoy> 1.8m side, 7.5 micron polythene (total 46 gram) ZP tetroon - about 1Kg lift :- http://imagebin.org/53237
[18:35] <Laurenceb> sweet! nice work
[18:35] <Laurenceb> how did you seal it?
[18:35] <SpeedEvil> shiny
[18:35] <Laurenceb> B&Q dust sheet?
[18:35] <RocketBoy> yep
[18:36] <SpeedEvil> I love the 'heavy duty' 7.5 micron ones :)
[18:36] <RocketBoy> tape
[18:36] <Laurenceb> neat, yeah I think tape is the way to go
[18:36] <Laurenceb> what sort?
[18:36] <RocketBoy> not bad for an hours work
[18:36] <SpeedEvil> at least try some tape in the freezer tho
[18:36] <RocketBoy> 1" wide clear sellotape
[18:37] <Laurenceb> ah simple
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[18:37] <Laurenceb> IIRC there was a JAXA balloon using tape
[18:37] <Laurenceb> they used some fancy £M stuff
[18:37] <Laurenceb> erm 3M
[18:38] <RocketBoy> i'd probably try heat sealing next time
[18:38] Action: SpeedEvil has barrels of 3M tape.
[18:38] <SpeedEvil> Though it's copper.
[18:38] <SpeedEvil> need to get it on ebay
[18:38] <Laurenceb> hmm boat pricing is weird, its like the lower end of the market is driven up - guess its all the boaty people
[18:38] <Laurenceb> RocketBoy: you want to go transatlantic with that?
[18:39] <RocketBoy> nope - just for experimenting
[18:39] <RocketBoy> at the mo
[18:39] <Laurenceb> it may work... whats the volume?
[18:39] <RocketBoy> about 1cu m
[18:40] <SpeedEvil> Laurenceb: yeah. I mean - couldn't you imagine yourself, a bevy of young ladies, taking to sea, with all the ameneties, including a ncluding a fully covered generator room (although at present the generator is not operational)
[18:40] <Laurenceb> needs helipad
[18:41] <Laurenceb> obligatory http://www.youtube.com/watch?v=R7yfISlGLNU
[18:41] <SpeedEvil> Couple of bits of MDF - job done.
[18:41] Action: SpeedEvil passes Laurenceb a big 'H' stencil.
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[18:45] <Laurenceb> you can buy a huge container ship for $15M, but a barge costs $150K - doesnt make sense
[18:46] Action: SpeedEvil knows a sillier one.
[18:47] <SpeedEvil> http://www.youtube.com/watch?v=zWRlKHMmfC0
[18:54] <mc_-> LB, do you anyone who has a lathe?
[18:54] Action: SpeedEvil has a lathe.
[18:54] <Laurenceb> RocketBoy?
[18:54] <SpeedEvil> But it's very, very broken
[18:54] <Laurenceb> http://www.wright-international.com/wil1991-25tcranebarge.php ,-- not a bad price
[18:54] <Laurenceb> also, free crane
[18:55] <mc_-> how about filament winding a tank?
[18:55] <Laurenceb> hmm you could just buy it off the shelf
[18:55] <mc_-> it would be stronger than a cf tube
[18:55] <SpeedEvil> Laurenceb: you want to get into contact with some nice somalian gentlemen.
[18:55] <Laurenceb> heh
[18:55] <SpeedEvil> mc_-: filliment winding isn't simple
[18:56] <mc_-> why
[18:56] <SpeedEvil> mc_-: and you can't really do it simply on a lathe
[18:56] <Laurenceb> mc_-: I doubt you could easily wind a better tank than off the shelf tube
[18:56] <SpeedEvil> you need to be able to do windings very far from the axis of the cylinder
[18:56] <Laurenceb> you could hawever use the lathe to spin aluminium alloy bulkheads
[18:57] <SpeedEvil> from a tangent
[18:58] <mc_-> i dont know if filament wound tube is off the shelf
[19:00] <SpeedEvil> it is
[19:00] <SpeedEvil> it's just that it's a dedicated machine that can only do tube
[19:01] <Laurenceb> you can get really high spec CF off the shelf in tube form
[19:02] <Laurenceb> its a matter of how much you want to pay
[19:02] <RocketBoy> yep I have a lathe - but it wouldn't be any good for filament winding - but i have used it to make rockey bulkheads
[19:03] <RocketBoy> rocketry
[19:03] <mc_-> cf tube isnt filament wound afaik
[19:04] <Laurenceb> still, for the stuff I've designed, you can easily get a safety factor of 2 with off the shelf
[19:04] <mc_-> missiles used to be filament wound in the 60s
[19:05] <Laurenceb> you get to a point where its not worth the trouble
[19:05] <Laurenceb> as the other components are still just as heavy
[19:06] <mc_-> are the cf tubes specs trustworthy?
[19:06] <Laurenceb> cost goes up ~ exponentially with tensile strenght
[19:06] <RocketBoy> in model rocketry we normall use CF tube made from CF sheet wound on a manderal
[19:06] <Laurenceb> well they use CF fabric which I would assume is
[19:07] <SpeedEvil> I saw what I thought was a filliment winding machine on the CF tube that Laurenceb linked to.
[19:07] <SpeedEvil> On reflection, it might just have been a winder
[19:07] <mc_-> would it take 1000psi?
[19:07] <Laurenceb> depends on the thickness
[19:08] <Laurenceb> I've designed for 500 with a 50% safety factor
[19:08] <Laurenceb> erm 100%
[19:08] <mc_-> how do you bond to it?
[19:08] <Laurenceb> sand, epoxy, or bolt and o rings
[19:08] <mc_-> and maintain the strength?
[19:08] <Laurenceb> for bolting your need to add reinforcement
[19:08] <mc_-> cant used bolts
[19:09] <mc_-> cf doesnt work with bolts
[19:09] <Laurenceb> prob best to use a CF flange
[19:09] <mc_-> is a flange off the shelf?
[19:09] <Laurenceb> not sure
[19:10] <SpeedEvil> It's not that hard to make - if you can get prepeg
[19:10] <Laurenceb> you could probably have some made up
[19:10] <SpeedEvil> but it's not really that hard to make, even if you can't - just more annoying
[19:11] <mc_-> dont think orings can be put in cf?
[19:11] <Laurenceb> dont see why not
[19:11] <Laurenceb> if designed appropriately
[19:11] <mc_-> how do you make the groove?
[19:12] <Laurenceb> you dont have one
[19:12] <Laurenceb> only one in the alu
[19:12] <mc_-> how do you seal?
[19:12] <Laurenceb> o rings can seal in that situation
[19:12] <SpeedEvil> compress the o-ring against the smooth CF/epoxy
[19:13] <SpeedEvil> the interface o-ring pressure is >> the tank pressure, so it seals
[19:13] <Laurenceb> theres whole books on how to do this right :P
[19:13] <mc_-> dont u need a groove?
[19:13] <Laurenceb> only on a minimum of one surface
[19:14] <mc_-> i think bulkhead needs a groove
[19:14] <Laurenceb> reusability is one thing to consider
[19:14] <SpeedEvil> nope.
[19:14] <Laurenceb> but your not going to be able to reuse it prectically
[19:14] <SpeedEvil> not if you're retaining it by some other mechanism
[19:15] <SpeedEvil> you want to be able to do a dozen test-fires ideally
[19:15] <Laurenceb> the CF is going to be thermally stressed too much acound the motor
[19:15] <Laurenceb> especially after burnout
[19:16] <Laurenceb> annoyingly that means an entirely seperate testing rig
[19:16] <mc_-> can the cf tube seal against a o ring?
[19:16] <Laurenceb> yes
[19:16] <SpeedEvil> it's nice smooth epoxy on the surface
[19:16] <Laurenceb> but you still have to secure the bulkhead
[19:16] <SpeedEvil> Or can be made so
[19:17] <mc_-> what holds the bulkheads in?
[19:17] <Laurenceb> bolts may just work, if the tube is reinforced at the point where the holes are
[19:17] <SpeedEvil> And what do you mean you can't bolt CF?
[19:17] <SpeedEvil> Assuming you have proper clamping bits, and aren't trying to flatten it
[19:18] <mc_-> stress concentrates around the holes
[19:18] <Laurenceb> internal ring of CF, and epoxy it to the tube
[19:18] <Laurenceb> then drill through
[19:18] <SpeedEvil> mc_-: sure it does - you can get round that though
[19:18] <SpeedEvil> It's anoying, yes.
[19:18] <Laurenceb> you can work out the concentration and appropriate reinforcement
[19:18] <mc_-> maybe, but it all adds weight
[19:19] <Laurenceb> yeah, but good for testing
[19:19] <Laurenceb> for flight you can use a CF flange
[19:19] <SpeedEvil> stainless tube, with water round it, for testing
[19:19] <Laurenceb> heh
[19:19] <Laurenceb> water is a massive overkill
[19:20] <SpeedEvil> overkill is good.
[19:20] <Laurenceb> so a CF flange with spun alu glued to it
[19:20] <mc_-> it a long process from static test to flight hardware
[19:20] <Laurenceb> not really
[19:20] <Laurenceb> as you already know what works
[19:21] <mc_-> my guess is a year+
[19:21] <Laurenceb> you use the test to a) get everything down to <1% error, and b) characterise TVC
[19:21] Action: SpeedEvil has the answer!
[19:21] <SpeedEvil> We need scrapheap challenge to sponsor it.
[19:21] <Laurenceb> you need to avoid the stage of playing about to learn the basics
[19:22] <mc_-> would be nice to have a test site within a short drive
[19:23] <Laurenceb> you want to avoid too many tests
[19:23] <Laurenceb> you want to know what works, test it, fine tune
[19:23] <Laurenceb> a few cycles of tests
[19:24] <Laurenceb> avoid the faffing about stage
[19:24] <mc_-> dont think anyone wants to faff
[19:25] <Laurenceb> theres enough data out there to design the basics on paper, you dont need to play about for ages and spend tons of money
[19:25] <mc_-> but tests rarely are as expected
[19:25] <Laurenceb> Id say test data I've seen is pretty consistent
[19:26] <Laurenceb> its not _that_ finicky
[19:26] <mc_-> flight tests or static tests?
[19:27] <Laurenceb> static tests
[19:27] <Laurenceb> go for static tests then first flight test is a full attempt
[19:29] <Laurenceb> you'll know that it works as long as avionics functions at that point
[19:30] Action: SpeedEvil thinks Laurenceb may be a _leetle_ bit overoptimistic.
[19:30] <Laurenceb> ok maybe a first stage test to make sure you avionics functions
[19:32] <Laurenceb> but do it from the balloon
[19:33] <Laurenceb> mc_-: I didnt realise starchaser were the people that incinerated dartmoor
[19:34] <Laurenceb> thats quite embarrasing for them
[19:35] <mc_-> most static tests are very over engineered
[19:36] <Laurenceb> http://houseboats.apolloduck.co.uk/feature.phtml?id=115700 <- thats affordable
[19:36] <Laurenceb> yeah, youd need a few static flight hardware tests once the design was finalised
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[19:37] <mc_-> a few static tests + a few flight tests will take 12 months+
[19:37] <Laurenceb> yep
[19:38] <Laurenceb> but theres plenty of money to be made
[19:38] <mc_-> you need a team to do this
[19:38] <Laurenceb> of course
[19:38] <mc_-> teams is where most groups fail
[19:39] <Laurenceb> yeah
[19:39] <mc_-> ppl disagree
[19:39] <Laurenceb> well really itd need to be a company
[19:39] <Laurenceb> for funding and so on, and once it was operational
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[19:40] <mc_-> more complexity..
[19:41] <Laurenceb> you couldnt just do something like this "for fun"
[19:41] <Laurenceb> maybe itd be affordable, but you may as well make some money from it
[19:44] <mc_-> think it impossible to get funding
[19:44] <Laurenceb> in the initial stages, yes
[19:45] <Laurenceb> once you have some hardware, maybe not
[19:45] <mc_-> have to have a customer to get funding
[19:45] <SpeedEvil> It's always the case. Once you have an orbiting laser battery that can destroy tokyo, it's easy to get funding.
[19:46] <Laurenceb> you need funding to buy the barge launch platform thats for sure
[19:47] <mc_-> can hire a barge
[19:47] <SpeedEvil> 'You want to do what on my barge???'
[19:48] <SpeedEvil> Contact sealand.
[19:48] <mc_-> halo launched a rockoon from a barge
[19:49] <Laurenceb> link?
[19:49] <mc_-> its one of the links when you goog rockoon
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[19:51] <mc_-> goole halo rockoon
[19:53] <Laurenceb> in 1997?
[19:53] <Laurenceb> http://en.wikipedia.org/wiki/Civilian_Space_eXploration_Team <- wow I didnt know that
[19:53] <Laurenceb> 100Km has been reached
[19:54] <Laurenceb> hmm 6m tall and 10 inch diameter... quite a lot bigger
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[19:57] <mc_-> its not proven csxt reached 100km
[19:57] <Laurenceb> http://houseboats.apolloduck.co.uk/feature.phtml?id=112726
[19:58] <mc_-> no gps alt
[19:58] Action: Laurenceb hands out wire brushes and paint
[19:58] <Laurenceb> ah ok
[19:58] <mc_-> imo it has to be repeatable
[20:00] <Laurenceb> that'd make a pretty cool launch facility
[20:01] <mc_-> not sure why noone has done an unmaned scaled down spaceship1
[20:01] <Laurenceb> the advantage of a barge is you can move with the wind, so balloon launch is easier
[20:01] <mc_-> yes
[20:02] <Laurenceb> not sure how seaworthy those things are
[20:03] <mc_-> do it need tobe seaworthy?
[20:03] <SpeedEvil> you may want to do it far out to sea
[20:04] <SpeedEvil> equator would be nice from some perspectives
[20:04] <SpeedEvil> launching from 0,0 would simplify the nav :)
[20:04] <mc_-> puts the cost up
[20:04] Action: SpeedEvil is reminded of the lunar comsat
[20:05] <Laurenceb> 0.0 gives you more velocity
[20:06] <Laurenceb> also you need to be far from populated areas to drop stages
[20:06] <mc_-> geting to 100km is diffidult enough
[20:06] <Laurenceb> north sea isnt big enough
[20:07] <Laurenceb> if 100 has been done already I dont see the point
[20:07] <mc_-> it hasnt
[20:07] <Laurenceb> you say :P
[20:07] <SpeedEvil> and you want a boat that can do at least 100mph west - every littl helps.
[20:07] <Laurenceb> heh
[20:10] <mc_-> do you have cf around the c. chamber?
[20:10] <Laurenceb> yes
[20:11] <Laurenceb> its all one lenght of tube
[20:11] <mc_-> can it take the heat?
[20:11] <Laurenceb> there isnt any heat
[20:11] <mc_-> you would need a liner?
[20:11] <SpeedEvil> till burnout
[20:11] <Laurenceb> yes
[20:12] <Laurenceb> burnout is hard to predict
[20:12] <Laurenceb> and is a bit variable across the propellant, so you need a liner
[20:12] <Laurenceb> about 2mm of high temperature quilt works
[20:12] <Laurenceb> its only about 100 grams per stage
[20:13] <Laurenceb> the CF is still damaged inevitably
[20:13] <Laurenceb> you cant really reuse it
[20:14] <Laurenceb> onother problem is pieces of propellant falling off just before burnout, you need to epoxy it to the liner
[20:14] <mc_-> cf loses strength if its hot
[20:15] <Laurenceb> yeah, but the fibres are parallel to the face
[20:15] <mc_-> glass might be better?
[20:15] <Laurenceb> that helps a lot
[20:15] <Laurenceb> glass is way too heavy, its the epoxy that loses strenght
[20:16] <Laurenceb> the liner only takes up 100grams, so theres nothing really to be optimised
[20:17] <Laurenceb> theres ablative liners in the pre and post combustion chambers, but I continued the quilt for the entire lenght for safety
[20:28] <Laurenceb> Im wondering if you could glue spun aluminium bulkheads to prepreg flanges
[20:29] <Laurenceb> http://barges.apolloduck.co.uk/display.phtml?aid=115446 <- would work
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[20:34] <Laurenceb> http://barges.apolloduck.co.uk/feature.phtml?id=115670 <- more like it, would fit two shipping containers side by side, and motorized
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[20:49] <Laurenceb> looks like its possible to match alu to CF youngs modulus wise
[21:01] <SpeedEvil> ?
[21:01] <SpeedEvil> it's oodles less stiff
[21:01] <SpeedEvil> oh - you mean sectionally
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[21:19] <Laurenceb> yes
[21:20] Action: Laurenceb has been watching the sunset
[21:20] Action: Laurenceb becomes a druid
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[21:22] Action: SpeedEvil thinks it's still up.
[21:23] <SpeedEvil> just down I guess
[21:28] <Laurenceb> hmm http://www.srrb.noaa.gov/highlights/sunrise/sunrise.html says 9.17, I timed it as 9.13
[21:28] <Laurenceb> and I was on a hill... odd
[21:32] <Laurenceb> aha there was a hill 10m higher than me in the way, all is explained
[21:33] <SpeedEvil> If google earth would properly shade stuff, that would be awesomee
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[21:45] <Laurenceb> interesting with the starchaser propellant they've got for a/b quite low
[21:46] <Laurenceb> - wide diameter bore in relation to propellant diamter
[21:47] <SpeedEvil> hmm
[21:47] <Laurenceb> I went for a bore of 0.6 times the propellant diamter
[21:51] <Fighter|gone> The 434MHz NTX2 is definately correct for license exempt operations in the UK yes?
[21:51] <Laurenceb> yep
[21:51] <Fighter|gone> Just their site says:
[21:51] <Fighter|gone> Available for licence-exempt operation in the 433MHz (EU) and 458MHz (UK) bands
[21:52] <Fighter|gone> Which implies to me you need a 458Mhz one for the UK :p
[21:52] <SpeedEvil> UK is in the EU
[21:53] <Fighter|gone> Ah so the UK is both 433 and 458?
[21:53] <SpeedEvil> it could also - and I think it does - imply that 458 is also available in the UK
[21:53] <Fighter|gone> Great, thanks
[21:53] Nick change: Fighter|gone -> Fighter1405
[21:53] <Fighter1405> OFCOM doesn't have anything much I can see about it :p
[21:54] <Laurenceb> weve only used 434
[21:55] <Fighter1405> Great, that's good
[21:55] <Fighter1405> Given I have a NTX2-434.075-10
[21:56] <Laurenceb> hmm the changing diamter is a bit of an issue, you have to throttle the motor, which harms efficiency
[21:56] <Laurenceb> prob one of the other reasons you cant get to really high efficiency
[21:59] <Laurenceb> but they seem to respond quite well to throttling, you can probably do it losing only 5% or so
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[22:09] <Fighter1405> Right, I gained nothing at all from reading the spec for the NTX2 :( what voltages are needed at the TXD pin for marks and spaces?
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[22:10] <SpeedEvil> work out how much you have to modulate it by - say 400Hz - over the maximum frequency span
[22:10] <SpeedEvil> if it has a span of 4KHz from 0-5V, then to modulate it by 400Hz, you need it to be 2-2.5V (1/10th range) say
[22:11] <Fighter1405> Eek, should it say somewhere what voltage it is centered around?
[22:12] <Fighter1405> 4. With 0V - 3.0V modulation input.
[22:13] <Fighter1405> DC-biased to 1.2V approx.
[22:13] <Fighter1405> So centered at 1.2v?
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[22:16] <AlexBreton> hi all
[22:16] <AlexBreton> sbasuita, you here?
[22:16] <Fighter1405> Hey AlexBreton
[22:16] <sbasuita> AlexBreton, evening
[22:16] <AlexBreton> OK
[22:16] <AlexBreton> ordered the SD module
[22:16] <sbasuita> ; )
[22:16] <AlexBreton> now, question
[22:16] <sbasuita> ?
[22:16] <AlexBreton> we have 2 choices for the board material
[22:16] <AlexBreton> a) polystyrene and b)celotex
[22:17] <AlexBreton> polystyrene we can get at the hardware store for a fiver
[22:17] <AlexBreton> celotex has half the U-value but will cost us 20 quid
[22:17] <AlexBreton> coz it's only available online and the delivery is rather pricey
[22:17] <AlexBreton> so, which do we go for?
[22:17] <SpeedEvil> no, it's not
[22:17] <AlexBreton> yes, but I can't find a shop in the area
[22:18] <SpeedEvil> There are going to be oodles of builders merchants within 20 miles
[22:19] <SpeedEvil> go to jewson, or travis-perkins website for a list
[22:19] <SpeedEvil> where are you - cambridge?
[22:19] <AlexBreton> Reading
[22:20] <AlexBreton> aha
[22:20] <sbasuita> AlexBreton, how did you come up with celotex?
[22:20] <AlexBreton> local hardware store has celotex, but only 50mm
[22:20] <AlexBreton> SpeedEvil told me ;-)
[22:20] <AlexBreton> (thanks there)
[22:20] <AlexBreton> 50mm is a tad thick
[22:21] <sbasuita> AlexBreton, well
[22:21] <Laurenceb> you can buy blue foam on ebay
[22:21] <Laurenceb> its the best
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[22:21] <Laurenceb> for this sort of stuff
[22:21] <SpeedEvil> you can get 25mm too
[22:22] <AlexBreton> yeah
[22:22] <SpeedEvil> it is however more fragile than polystyrene
[22:22] <AlexBreton> costs 17 quid for some reason
[22:22] <AlexBreton> probably tonnes of it
[22:22] <SpeedEvil> it's a rather big sheet :)
[22:22] <SpeedEvil> 1200*2400*25mm
[22:22] <SpeedEvil> also - look on ebay
[22:22] <SpeedEvil> for some in your area
[22:23] <AlexBreton> sbasuita, what's the verdict?
[22:23] <SpeedEvil> the building materials and supplies section
[22:23] <SpeedEvil> it depends if the sums indicate you need it
[22:25] <AlexBreton> Jewson appears to sell 'high performance plasterboard insulation'
[22:25] <sbasuita> AlexBreton, might as well go for some proper insulating materials
[22:25] <sbasuita> AlexBreton, get the school to pay
[22:26] <SpeedEvil> that may be plasterbo0ard+laminated insulation.
[22:26] <SpeedEvil> Which might be a tad heavy :)
[22:26] <Laurenceb> depends how you define fragile
[22:26] <SpeedEvil> however - turning up looking impoverished and asking for any broken sheets may have results
[22:27] <Laurenceb> compressive and tensile strenght is much higher
[22:27] <Laurenceb> but its much more rigid
[22:27] <Laurenceb> so tends to get smashed
[22:27] <SpeedEvil> suppose
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[22:28] <AlexBreton> how about a compound construction?
[22:28] <AlexBreton> plasterboard and celotex?
[22:28] <sbasuita> AlexBreton, yeah, probably best to find a brick and mortar store and ask for some broken bits
[22:28] <AlexBreton> would be a pain to put them together
[22:28] <sbasuita> AlexBreton, compound construction isn't in the syllabus till A level man
[22:28] <sbasuita> AlexBreton, you're playing with dangerous forces
[22:28] <AlexBreton> cut the crap
[22:28] <AlexBreton> I'm serious
[22:28] <AlexBreton> ;-)
[22:29] <AlexBreton> we could get some crappy MDF
[22:29] <AlexBreton> a thin sheet
[22:29] <AlexBreton> and 25mm of celotex on the inside or outside
[22:29] <AlexBreton> what do you reckon?
[22:30] <AlexBreton> or wait...cardboard
[22:30] <AlexBreton> some really thick one
[22:31] <SpeedEvil> plasterboard is _heavy_
[22:31] <SpeedEvil> However, a simple wooden frame inside wouldn't be a bad plan
[22:31] <sbasuita> Hmm...
[22:31] <sbasuita> lots of options to think about
[22:32] <SpeedEvil> make a box out of 3mm or so plywood, with each side having all but the edge 30mm cut away
[22:33] <SpeedEvil> cardboard isn't a silly idea.
[22:33] <AlexBreton> yes
[22:33] <AlexBreton> thick cardboard is surprisingly strong
[22:33] <AlexBreton> costs peanuts and is rather light
[22:34] <SpeedEvil> you'll need to paint it of course
[22:34] <AlexBreton> well we were thinking of using cardboard as the frame
[22:34] <AlexBreton> and celotex or polystyrene on top
[22:34] <AlexBreton> or inside
[22:34] <AlexBreton> makes no real difference
[22:34] <AlexBreton> I'm sure all of us have old Amazon boxes to use
[22:35] <sbasuita> OK, so to wrap up: celotex is insualting but weak so we will use that and just support it with another material?
[22:35] <AlexBreton> yes
[22:35] <AlexBreton> you got it
[22:35] <sbasuita> cool
[22:35] <SpeedEvil> warm - hopefully :)
[22:35] <AlexBreton> the supporting material is some sort of light wodd or cardboard
[22:35] <SpeedEvil> Are you putting a camera in?
[22:35] <AlexBreton> how about balsa?
[22:36] <AlexBreton> SpeedEvil yes
[22:36] <sbasuita> SpeedEvil, yes
[22:36] <AlexBreton> balsa wood...very very light
[22:36] <SpeedEvil> one, or two?
[22:36] <AlexBreton> strong enough
[22:36] <AlexBreton> 1
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[22:36] <sbasuita> SpeedEvil, side facing
[22:36] <SpeedEvil> I'd consider putting it vertically
[22:36] <SpeedEvil> I mean portrait
[22:36] <SpeedEvil> not landsscape
[22:37] <AlexBreton> why so?
[22:37] <SpeedEvil> and canted down, so that you get a normal landscape shot with a bit of zoom effectively, and then a large strip that'll show you bits that you normally don't see
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[22:38] <SpeedEvil> I'm just saying this is what I'm planning on for my launch - eventually - not that it's a brilliant idea.
[22:38] <AlexBreton> hmmm
[22:38] <AlexBreton> I think conventional landscape this time
[22:38] <sbasuita> yeah
[22:38] <SpeedEvil> Just that you rarely see the ground other than at a very extended range.
[22:39] <AlexBreton> brb, gonna print off a receipt ;-)
[22:39] <sbasuita> i think for the second launch we'll go ground exclusive
[22:39] <SpeedEvil> and it might be nice to see more.
[22:39] <SpeedEvil> Oh
[22:39] <sbasuita> so this time we'll go for some horizon stuff
[22:39] <SpeedEvil> you also need a UV filter
[22:39] <SpeedEvil> will give you lots better pics
[22:39] <sbasuita> Not sure if we'll need to mount it at an angle, because the payload will probably hang off centre due to balance
[22:39] <sbasuita> we'll see
[22:39] <sbasuita> SpeedEvil, any recommendations?
[22:39] <SpeedEvil> and acts as a handy window to keep the wind out
[22:39] <SpeedEvil> nope - ebay
[22:40] <sbasuita> "However, UV filters (in particular filters lacking coating) may introduce flaring and have negative impact on contrast and sharpness, especially when a strong light source is present."
[22:40] <sbasuita> that doesn't sound too good
[22:41] <AlexBreton> lol
[22:41] <AlexBreton> UV filter's don't make much difference on the ground
[22:41] <SpeedEvil> Yes - however - the extreme levels of UV in the upper atmosphere
[22:42] <AlexBreton> has every launch used one?
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[22:42] <AlexBreton> bbl
[22:42] <SpeedEvil> IIRC the launches from people that have added filters say they improve things
[22:43] <sbasuita> AlexBreton, might as well
[22:44] <SpeedEvil> but ask again tomorrow - more people'll be around
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[22:48] <fnoble> natrium42: you around?
[22:48] <natrium42> yo
[22:50] <fnoble> do you have an eagle footprint for the sarantel antenna?
[22:50] <fnoble> also, which is the one to use with the venus? did you go for active or passive?
[22:50] Action: Laurenceb would be interested in that too :P
[22:51] <natrium42> yeah, i made a footprint
[22:51] <natrium42> i can email it to you
[22:51] <natrium42> as for antennas, i tried quite a few
[22:51] <fnoble> ah thanks, that would be awesome if you dont mind
[22:52] <natrium42> do i have your email address?
[22:52] <fnoble> erm, im not sure, ill pm it to you
[22:52] <natrium42> fn217?
[22:52] <fnoble> yup thats it
[22:52] <natrium42> ok, cool
[22:54] <fnoble> so how did the different antennas compare?
[22:56] <natrium42> sent
[22:56] Nick change: Fighter1405 -> Fighter|sleep
[22:57] <natrium42> i ended up going with 18mm passive patch as it was cheaper than anything else
[22:57] <fnoble> ok
[22:58] <natrium42> taoglas tiny active patches worked quite well
[22:58] <natrium42> but were easy to detune
[22:59] <g1zvn> fnoble, sarantels can be jammed by other clocks on the board
[22:59] <natrium42> i'd go with helix antennas for ballooning stuff
[22:59] <natrium42> as they are near omni directional
[22:59] <fnoble> yup, ok, also i want the pcb to be vertical which wouldnt work with a patch
[23:00] <g1zvn> ive got some srntls if you need some
[23:00] Nick change: g1zvn -> mc_
[23:00] <fnoble> mc_: how bad is the clock jamming? is there an easy way to prevent it?
[23:00] <natrium42> fnoble, there are 90 mounted patches --> http://taoglas.com/antennas/GPS_Antennas/Internal_GPS_-_Active_Patch_Modules/
[23:01] <natrium42> but like i said, they are really easy to detune if you have things nearby
[23:01] <mc_> depens on the clk freq
[23:01] <fnoble> i have a 48mhz crystal on board and a 434mhz radio
[23:02] <SpeedEvil> The Freerunner phone suffered from SD clock jamming the GPS
[23:02] <mc_> keep the srntl away from evrything
[23:02] <fnoble> natrium42: thats good to know
[23:02] <SpeedEvil> on testing - it wasn't revealed - as they used a GPS tester, with too high a signal level
[23:02] <fnoble> hehe, they never thought to take it outside and see if it worked :)
[23:02] <mc_> yes,most ppl test wrongly
[23:03] <fnoble> natrium42: how did you find the performance of the sarantel?
[23:03] <fnoble> thanks for the lib btw
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[23:05] <mc_> fnoble sugest you put the srntl on a short piece of coax
[23:06] <mc_> might perform much better
[23:06] <fnoble> mc_: was hoping for an integrated solution, all on the pcb
[23:07] <mc_> or point the null towards the clk on your pcb
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[23:07] <fnoble> natrium42: did you test the SL1204?
[23:08] <natrium42> nope
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[23:08] <natrium42> i only have the 1st gen ones
[23:10] <fnoble> ok
[23:10] <fnoble> did they work ok?
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[23:20] Action: Laurenceb is reading "space propulsion analysis and design"
[23:21] <Laurenceb> http://www.srrb.noaa.gov/highlights/sunrise/sunrise.html
[23:21] <Laurenceb> erm - http://www.amazon.co.uk/Propulsion-Analysis-Design-Ronald-Humble/dp/0070313202
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[23:22] <Laurenceb> hey mc_-
[23:22] <Laurenceb> space propulsion analysis and design has a nice section on hybrid motors
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[23:30] <natrium42> <fnoble> did they work ok? <- yes
[23:30] <Laurenceb> you have the venus working now?
[23:32] <SpeedEvil> meant to mention that to you too - that's a good one
[23:32] <Laurenceb> the hybrid theory is interesting
[23:32] <Laurenceb> but you need to be careful treating it to such high precision
[23:33] <Laurenceb> the graphs of regression rate are a bit off what I've seen in test data - due to the effect of the precombustion chamber I suspect
[23:35] <SpeedEvil> http://groups.google.com/group/sci.space.policy/browse_frm/thread/4eb0f25a1c3268bb/fe725371918310ac?hl=en&tvc=1&q="space+propulsion"+sutton#fe725371918310ac
[23:36] <SpeedEvil> http://groups.google.com/group/sci.space.policy/browse_frm/thread/4eb0f25a1c3268bb/8ad7475b623fea98?hl=enx8;ad7475b623fea98
[23:37] <SpeedEvil> rather
[23:37] <SpeedEvil> Henry Spencer has _lots_ of clue
[23:38] <fnoble> edmoore: boo
[23:39] <SpeedEvil> Laurenceb: above is a list of books
[23:39] <Laurenceb> yeah, thanks
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[23:47] <Laurenceb> peroxide hybrid theoretic ISP is approx equal to RP-1 peroxide
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[00:00] --- Mon Jun 22 2009