highaltitude.log.20090620

[00:00] <SpeedEvil> ah
[00:00] <SpeedEvil> I though you were going for a slow burning 4th
[00:01] <Laurenceb> yes
[00:01] <Laurenceb> 4th is monoprop
[00:01] <Laurenceb> I think you can get the dry mass down to 350 grams from the 4th stage
[00:02] <Laurenceb> - + 500 grams of tronics and batteries
[00:02] <Laurenceb> then the satellite
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[00:18] <Laurenceb> hmm looks like the trick is to have a double burn time for the first stage then coast for 30 seconds or so
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[00:18] <Laurenceb> at way you get above the atmosphere
[00:19] <Laurenceb> unfortunately thats rather hard to arrange with hybrids... maybe you need to ditch the identical module idea
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[00:58] Nick change: KingJ -> kingj
[01:03] <Laurenceb> SpeedEvil: I got it up to 500KM circular with identical stages from 20Km
[01:04] <Laurenceb> 40second burn time each, with 80 seconds cruise after first stage burnout
[01:12] <SpeedEvil> hmm
[01:12] <SpeedEvil> that's 3 stages, and a 4th small monoprop?
[01:15] <Laurenceb> yeah
[01:16] <Laurenceb> I was reading Sutton, it suggests using ablative "fuel" for the post combustion chamber
[01:16] <Laurenceb> effectively saves you a lot of mass if you can do that
[01:17] <Laurenceb> I'm working on a design with an aluminium retainer at the bottom - it may be possible to use it to hold a graphite throat liner
[01:17] <Laurenceb> theres a similar design in sutton
[01:18] <SpeedEvil> hmm
[01:18] <SpeedEvil> sutton is a good book :)
[01:19] <Laurenceb> so a seperate ablative liner that bolts on
[01:19] <Laurenceb> you need to insulate the graphite from the aluminium - wonder if ceramic foam materials may help
[01:23] <Laurenceb> http://www.ceramic-honeycombs.com/en/ProductShow.asp?id=14
[01:24] <Laurenceb> used for filtering molten iron ?! crazy stuff
[01:25] <SpeedEvil> :)
[01:28] <Laurenceb> ceramic foam lampshades ?!
[01:28] Action: Laurenceb heads to B&Q
[01:28] <SpeedEvil> 'I'd like to return this lampshade'
[01:29] <SpeedEvil> 'But it's melted, and smells of parrafin'
[01:32] <Laurenceb> unfortunately the compressive strenght is a bit low
[01:32] <Laurenceb> around 1MPa
[01:33] <SpeedEvil> 10cm*10cm or so for a 5* safety margin I guess
[01:33] <Laurenceb> it has to be used as a mount for the liner
[01:33] <Laurenceb> so its exposed to ~500PSI = 3.4MPa
[01:34] <SpeedEvil> ah
[01:38] Action: SpeedEvil is currently backing up new lappies old hard drive.
[01:38] <SpeedEvil> Slackware - here we come.
[01:40] <Laurenceb> cool
[01:46] <Laurenceb> http://www.smallparts.com <- nice site
[01:47] <SpeedEvil> I vaguely recall that
[01:48] <SpeedEvil> I actually do have some carbon foam that might almost suit
[01:48] <SpeedEvil> sort of open-cell foam, but from carbon
[01:49] <SpeedEvil> probably not very insulative though
[01:49] <Laurenceb> yeah thats the problem with carbon
[01:49] <Laurenceb> silica fabric would probably do something
[01:50] <Laurenceb> whats that stuff for gardening called?
[01:50] <SpeedEvil> ?
[01:50] <Laurenceb> that you add to compost
[01:50] <SpeedEvil> piss?
[01:50] <Laurenceb> white ceramic/pumice type stuff
[01:50] <Laurenceb> lol
[01:52] <Laurenceb> in small granules ~5mm
[01:52] <SpeedEvil> ammonium sulphamate?
[01:52] <SpeedEvil> http://en.wikipedia.org/wiki/Ammonium_sulfamate
[01:53] <SpeedEvil> oh - you may mean vermiculite
[01:53] <SpeedEvil> or perlite
[01:53] <Laurenceb> ah perlite
[01:53] <SpeedEvil> which is either expanded mica, or expanded glass
[01:53] <Laurenceb> thats the stuff
[01:54] <SpeedEvil> I assume that it was a filler in one of the composite nozzles
[01:54] <Laurenceb> oh yeah
[01:54] <SpeedEvil> however, it was misquoted as pearlite - which - as a allotrope of iron - seems unlikelyt
[01:54] <SpeedEvil> allotrope?
[01:54] <SpeedEvil> yeah
[01:54] Action: Laurenceb cant remember a level chemistry
[01:54] <SpeedEvil> different forms
[01:55] <Laurenceb> yeah
[01:55] <SpeedEvil> graphite/coal/nanotube/diamond
[01:55] <SpeedEvil> /graphene
[01:55] <SpeedEvil> damn versatile molecule carbon
[01:55] <Laurenceb> as far a ablatives go, epoxy silica is good enough
[01:55] <Laurenceb> the angle of the fibres makes a difference
[01:56] <Laurenceb> at 15 degrees to the center line is about best for char depth reduction
[01:56] <Laurenceb> 90 degrees gives less erosion
[01:58] <Laurenceb> I guess its probably easiest to use a filly ablative nozzle and throat
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[01:58] <Laurenceb> especially with hybrids where the burn rate increases with time
[01:59] <SpeedEvil> You'll get the RSPCA onto you.
[01:59] <SpeedEvil> With filly ablative nozzles.
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[09:42] <mc_-> hi jcoxon, see my valve pic ?
[09:43] <jcoxon> hey mc, yeah had a look this morning
[09:44] <jcoxon> couple of q
[09:44] <jcoxon> uestions
[09:44] <jcoxon> once the plastic has melted would the 'stopper' just drop into place?
[09:45] <mc_-> yes, but it might need a spring to help it
[09:47] <mc_-> perhaps its better if the stopper is V shaped
[09:48] <jcoxon> the other thing is that we'd need the cutdown circuitry in the neck of hte balloon
[09:49] <jcoxon> thats why i quite like having the 2 line system as we can cut the line closer to the payload
[09:51] <mc_-> for a mini zp the payload is right next to the zp
[09:51] <mc_-> to keep everthing within 2m limits
[09:51] <jcoxon> oh i haven't been designing for a mini-zp
[09:52] <jcoxon> going to use latex balloons still
[09:52] <mc_-> ah ok
[09:54] <mc_-> does your cutdown let He out?
[09:54] <jcoxon> no it stops it escaping
[09:55] <jcoxon> so you put an open vent in a latex balloon, like bill brown did in that powerpoint
[09:55] <jcoxon> then when you reach neutral bouyancy at altitude you cut the line and valve closes
[09:55] <mc_-> i meant your cutdown system?
[09:56] <mc_-> it separates payload and balloon?
[09:57] <jcoxon> it seperates one of the lines, so the payload pulls tight on the other closing the valve
[09:57] <jcoxon> whether i add a second cutdown i haven't decided
[09:57] <jcoxon> as in to terminate the flight itself
[10:01] <mc_-> i get it now
[10:01] <mc_-> so the cut circuit is in the payload
[10:01] <mc_-> and no wires goin up to the balloon
[10:03] <jcoxon> no, the cutdown circuit is down near the balloon
[10:03] <jcoxon> oops the payload
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[10:04] <jcoxon> yes
[10:04] <jcoxon> sorry misread you comment
[10:04] <jcoxon> bbl
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[11:10] <AlexBreton> sbasuita, what up?
[11:11] <sbasuita> AlexBreton, not much really
[11:11] <sbasuita> AlexBreton, bit bored
[11:11] <AlexBreton> yeah same
[11:11] <AlexBreton> gonna try and order that SD module soon
[11:12] <sbasuita> AlexBreton, cool
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[11:19] Nick change: kingj -> KingJ
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[11:27] <Guest14734> stupid mirc....
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[11:31] <sbasuita> back to xchat :)
[11:51] Action: sbasuita is playing with websdrs
[11:52] Action: SpeedEvil is playing with installing slackware.
[11:52] <sbasuita> old school
[11:52] <sbasuita> shame the java interfaces can't do decoding
[11:52] <sbasuita> there was a tonne of digital
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[12:00] <AlexBreton> sbasuita, rolling down to Wickes for some 25mm polystyrene sheet
[12:01] <SpeedEvil> kingspan/celotex PIR/PUR sheet has twice the insulative qualities
[12:01] <SpeedEvil> though is a bit more tricky to work with
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[12:03] <AlexBreton> they only seem to sell celotex in bulk
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[12:05] <AlexBreton> Speedevil, celotex seems to be quite a bit more esxpensive
[12:05] <AlexBreton> 10 quid for the sheet
[12:06] <SpeedEvil> yes, it's about double the price - but the same cost per unit of insulativeness
[12:06] <SpeedEvil> or whatever
[12:06] <AlexBreton> SpeedEvil, celotex or Kingspan?
[12:06] <AlexBreton> which is best?
[12:06] <SpeedEvil> (most celotex/kingspan is in the range of 0.02W/m/K, not 0.04W/m/K that polystyrene is.
[12:06] <SpeedEvil> they are the same
[12:07] <AlexBreton> OK celotex is 2 pounds / sheet, Kingspan is 10 /sheet
[12:07] <SpeedEvil> though complicating matters, celotex I think do polystyrene with special blowing agents that does 0.03W/m/k
[12:07] <AlexBreton> I'll buy some celotex sheet then, not polystyrene
[12:07] <AlexBreton> thanks for the tip ;-)
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[13:10] <rjharrison> boo
[13:10] <rjharrison> Hi all
[13:10] <edmoore> hi
[13:10] <rjharrison> anything exciting going on
[13:10] <rjharrison> Hi edmoore: Did you have a good trip
[13:10] <edmoore> yes thanks
[13:10] <rjharrison> Any news on the lost badger?
[13:11] <edmoore> it's lost
[13:11] <rjharrison> Shame, it teased everyone with it's track
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[13:59] <jcoxon> hey rjharrison
[14:04] <edmoore> jcoxon and rjharrison check inboxes
[14:04] <jcoxon> hehe
[14:04] <jcoxon> have you solved the problem?
[14:05] <edmoore> yep :)
[14:06] <jcoxon> twas good work getting 2 pictures
[14:06] <edmoore> yeah
[14:06] <jcoxon> hows tricks ed?
[14:06] <edmoore> not bad
[14:07] <edmoore> just trying to cancel vodafone contract
[14:07] <jcoxon> getting an iphone?
[14:08] <edmoore> been on hold for about 40 mins now
[14:08] <edmoore> just left it speakerphoning in the corner
[14:08] <edmoore> yeah
[14:09] <jcoxon> not going for the new vodafone google phone
[14:09] Action: jcoxon has one
[14:09] <edmoore> otherwise it's not too bad. had a decent may well
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[14:21] <edmoore> ok bbbl
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[14:23] <rjharrison> Ye jcoxon
[14:23] <rjharrison> hey
[14:24] <jcoxon> hey
[14:24] <rjharrison> Moving to the Atmega168
[14:24] <jcoxon> you are?
[14:25] <rjharrison> Yep
[14:26] <rjharrison> The only real difference is the fuse settings
[14:27] <jcoxon> more space on the 168 isn't there?
[14:27] <jcoxon> oh has my board arrived?
[14:28] <rjharrison> Not yet I think it should be monday
[14:28] <rjharrison> i'll pop it in the post to you on monday if you like
[14:29] <jcoxon> yeah
[14:29] <jcoxon> how much do i owe you?
[14:30] <rjharrison> Oh just a rough converion of the invoice
[14:30] <rjharrison> There or there abouts
[14:32] <jcoxon> okay, cool
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[16:10] <Strel> hi all. what's everyone's verdict on a pegasus XLR flex wing with a rotax 447 engine?
[16:29] <SpeedEvil> not really that sort of room alas.
[16:29] <SpeedEvil> Well - it's on-topic - but few in the channel I think fly planes.
[16:30] <SpeedEvil> more automated things dropped from balloons, and UAVs.
[16:32] Nick change: KingJ -> kingj
[16:37] <Strel> no problem. just curious as one is up for sale. :)
[16:38] <Strel> not by me but i seen one up for grabs and wondered on peoples verdicts.
[16:46] Nick change: kingj -> KingJ
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[20:21] <sbasuita> What mode is in the middle of this waterfall? http://outside.wallawalla.edu:8901/
[20:37] <sbasuita> ooh
[20:37] Action: sbasuita is listening to heathrow on globaltuners
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[20:41] <SpeedEvil> looks like noise
[20:42] <SpeedEvil> If you look, there is no real signal content
[20:42] <SpeedEvil> no time-varying portion, like all the other signals
[20:42] <SpeedEvil> actually - that's not quite true
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[22:49] <Laurenceb> hello
[22:52] <sbasuita> hi
[23:02] <Laurenceb> SpeedEvil: ping
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[23:16] <SpeedEvil> j
[23:16] <SpeedEvil> ?
[23:17] <Laurenceb> hi
[23:18] <Laurenceb> I ran some sims using rought drag data, and got into orbit for the ground - without a sat
[23:18] <Laurenceb> *rough
[23:19] <Laurenceb> but only 230Km circular
[23:19] <SpeedEvil> I can orbit 0Kg right now in a 230Km orbit!
[23:19] <SpeedEvil> There - I just did it again!
[23:19] <SpeedEvil> :)
[23:20] <SpeedEvil> what are you assuming for Cd?
[23:20] <Laurenceb> heh, the 4th stage and electronc is in orbit
[23:20] <Laurenceb> between 0.1 and 0.5
[23:20] <Laurenceb> depending on mac
[23:20] <SpeedEvil> mac?
[23:20] <SpeedEvil> oh
[23:20] <SpeedEvil> that''s very low for an assembly of tubes
[23:21] <Laurenceb> it needs long coast period at end of first stage burn
[23:21] <SpeedEvil> for one tube, with a optimally low-drag, and a good nosecone maybe
[23:21] <Laurenceb> theres a large fairing on the front
[23:21] <Laurenceb> about 20cm diameter
[23:22] <SpeedEvil> I don't think that does that much at subsonic speeds
[23:22] <SpeedEvil> I could be wrong
[23:22] <SpeedEvil> haven't researched this much
[23:22] <Laurenceb> it basically gets you up to 31Km and about 100m/s at second stage ignition
[23:23] <Laurenceb> but I'm wondering if you could remove the first stage and improve the 4th
[23:23] <SpeedEvil> I'm sure I remember this is where I came in.
[23:23] <Laurenceb> then got for a 20Km balloon with a much lighter rocket
[23:23] <SpeedEvil> hmm
[23:23] <Laurenceb> about 55Kg
[23:25] <SpeedEvil> 20km is what - 50g/m^3 - so 1000m^3 ish, or 14m diameter or so.
[23:25] <SpeedEvil> not bad at all
[23:25] <Laurenceb> yeah drag losses really screw things up for a ground launch
[23:26] <Laurenceb> your losing ~1.5Km/s at least
[23:26] <SpeedEvil> Of course, it makes the setup a lot harder.
[23:26] <SpeedEvil> Unless you design it for another 90Kg lift.
[23:26] <SpeedEvil> And take a parachute along.
[23:26] <Laurenceb> 20Km is fairly doable, especially if you can get the weight down
[23:26] <Laurenceb> why?
[23:27] <SpeedEvil> tinker with it, then light the blue touchpaper by hand!
[23:27] <Laurenceb> oh lol
[23:27] <Laurenceb> well your not going to want to be near it anyway
[23:28] <SpeedEvil> course
[23:28] <Laurenceb> and it needs good attitude control, so I dont see a problem with a balloon, other than envelope fabrication and helium
[23:28] <Laurenceb> which gets a lot easier as you get lighter
[23:28] <SpeedEvil> Or even H
[23:29] <SpeedEvil> at least for test launches
[23:29] <Laurenceb> I'm not convinced hybrids are easier
[23:29] <SpeedEvil> drop a couple of bags of cement on london.
[23:30] <Laurenceb> easier to build, but there seems to be more to go wrong
[23:30] <SpeedEvil> you mean uncertainties over mixture?
[23:31] <SpeedEvil> and regression rate?
[23:31] <Laurenceb> yes, and nozzle design is complicated
[23:31] edmoore (n=ed@pomegranate.chu.cam.ac.uk) joined #highaltitude.
[23:31] <Laurenceb> and shearing of propellant ect
[23:31] <Laurenceb> theres a lot to screw up
[23:32] <SpeedEvil> nozzle design?
[23:32] <SpeedEvil> how
[23:32] <SpeedEvil> oh - the post-combustion chamber?
[23:32] <Laurenceb> it seems you can get about 10% higher ISP over kerosene, but maintaining optimal conditions is harder
[23:32] <Laurenceb> yes the post combustion chamber
[23:33] <Laurenceb> also the middle bulkhead is hard to mount
[23:33] <Laurenceb> without weakening the CF tube
[23:33] <Laurenceb> and the entire thing ripping intself in half
[23:34] <SpeedEvil> Bit of prepeg, over a collet, with a plastic layer over the surface, making a little hat-shape, push halfway down tube, pull off plastic from end, expand collet, heat?
[23:35] <Laurenceb> yeah I guess, but very fiddly
[23:35] <Laurenceb> two tubes might be better
[23:35] <Laurenceb> then both attached to the nijector
[23:37] <SpeedEvil> I think you picked the wrong hobby if you want not fiddly :)
[23:38] Action: Laurenceb wonders about taping an envelope together rather than heat sealing
[23:38] <SpeedEvil> Have you considered full-scale steam locomotive rebuilding?
[23:38] <Laurenceb> lol
[23:38] <SpeedEvil> I'd want a hell of a lot of testing of tapes.
[23:39] <Laurenceb> theres a french guy who built a man carrying solar balloon with parcel tape :P
[23:39] edmoore (n=ed@pomegranate.chu.cam.ac.uk) left irc:
[23:39] <Laurenceb> also he built it on the top of a multistory car park at 1am
[23:41] <SpeedEvil> ...
[23:41] <SpeedEvil> That shows the courage of your convictions.
[23:41] <SpeedEvil> Assuming he was the man.
[23:41] <Laurenceb> http://pagesperso-orange.fr/ballonsolaire/photos-coupe-icare.htm
[23:42] <Laurenceb> lol W26NP
[23:44] <SpeedEvil> nice
[23:44] <stilldavid> SpeedEvil: got a minute to help me figure out my radio?
[23:45] <SpeedEvil> sure
[23:45] <stilldavid> I suppose it would just be fldigi help. I read the log where you explained FSK
[23:45] <SpeedEvil> np: The Buggles - Video Killed the Radio Star.
[23:46] <SpeedEvil> I've only slightly used fldigi
[23:47] <stilldavid> can it decode FSK, or is it radio-dependent?
[23:50] <SpeedEvil> The SSB radio essentially converts a slice of spectrum down to audio
[23:50] <SpeedEvil> where the soundcard can recieve it
[23:51] <SpeedEvil> then fldigi can do lots of modes - fsk, mfsk, psk31, morse, columbo, ...
[23:51] <stilldavid> Gah, I don't think my radio supports SSB then.
[23:51] <SpeedEvil> what is it?
[23:51] <stilldavid> whoops, should have done more research...
[23:52] <stilldavid> Yaesu FT-7800
[23:54] <SpeedEvil> 'Modes : F3E, F2D, F2A ' - from an ebay auction.
[23:54] <SpeedEvil> Looks like not.
[23:54] <SpeedEvil> It may sort-of-recieve FSK, but not in a way that fldigi will directly understand.
[23:54] <stilldavid> I hear pops, but that's it.
[23:55] <stilldavid> Any recommendations for an inexpensive radio?
[23:55] <SpeedEvil> you should hear something that sounds like a low intermittent buzz
[23:55] <SpeedEvil> that changes as you transmit data
[23:56] <stilldavid> Right now I have it set to send "hello world" in plain rs-232 at 50bps once every 5 seconds.
[23:56] <SpeedEvil> what you will recieve will not be 0000011111111000000011111100000 - as you would if there was no highpass in the way - but
[23:57] <SpeedEvil> 00000100000000-10000000100000-10000...
[23:57] <SpeedEvil> with small impulses at each bit-change, not steady values
[23:58] <SpeedEvil> sorry :(
[23:58] <stilldavid> heh, not your fault :P I clearly need to read up some more.
[23:59] <SpeedEvil> fortunately, ebay should at least do a partial refund
[00:00] --- Sun Jun 21 2009