highaltitude.log.20090705

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[00:49] <Laurenceb> SpeedEvil: ping
[00:50] <Laurenceb> I was reading about a LLNL proposal called "mockingbird" but cant find much info about it
[00:50] <SpeedEvil> ?
[00:50] <SpeedEvil> rings vague bells
[00:50] <SpeedEvil> this would be about 6 years ago?
[00:50] <Laurenceb> apparently a SSTO 1500Kg GLOW with H2O2 and kerosene
[00:50] <Laurenceb> 1992
[00:50] <SpeedEvil> yeah
[00:50] <Laurenceb> 75Kg dry mass
[00:50] <SpeedEvil> for large values of 6
[00:51] <SpeedEvil> I don't think it went anywhere
[00:51] <Laurenceb> nope, not even any flashy presentations on it are findable
[00:51] <Laurenceb> apparently conical with 8 regen engines, CF body at 20PSI and decomposition powered piston pumps
[00:52] <Laurenceb> sounds very similar to the approach I was considering, then crossed with delta-clipper
[00:53] <Laurenceb> I'm not sure if regen engines are any better at the scale of a couple of KN thrust
[00:53] <SpeedEvil> dunno
[00:53] <SpeedEvil> I was preferring them for testability reasons
[00:53] <Laurenceb> with decent graphite you can have a 3mm thick nozzle
[00:54] <Laurenceb> then the chamber can be alumiuium with an ablative liner that acts like more fuel
[00:54] <Laurenceb> wheras regen you need quite thick walls to get enough fuel flow
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[08:27] <jcoxon> morning all
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[09:17] Topic changed on #highaltitude by jcoxon!n=jcoxon@host81-159-26-92.range81-159.btcentralplus.com: Welcome to #highaltitude - discuss anything to do with high altitude projects (balloons, gliders, etc) www.ukhas.org.uk, wiki.ukhas.org.uk - Potential Launch: BallestHalo 1, 11/07/09
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[12:25] <mc_-> Laurenceb
[12:25] <Laurenceb> hey
[12:26] <mc_-> was my rocket book any good?
[12:26] <Laurenceb> yeah thanks, very good read
[12:26] <mc_-> its meant to be as good as sutton
[12:27] <mc_-> where are you at with your design?
[12:27] <Laurenceb> heh I dont know
[12:27] <Laurenceb> I played about with a few things
[12:27] <Laurenceb> pressure fed kind of sucks really
[12:28] <Laurenceb> hard to get under 9% mass fraction
[12:28] <mc_-> yes, but its much much easier to build
[12:29] <mc_-> mass fraction isnt so critical with multiple stages IMO
[12:30] <Laurenceb> I'd say if you want to do an n-prize style launch
[12:30] <mc_-> I saw the cf tow speedevil found
[12:30] <Laurenceb> then two stages
[12:31] <Laurenceb> CF tube tank with helium pressurant
[12:31] <Laurenceb> then a pintle injector going into an ablatively cooled chamber with graphite nozzle
[12:31] <Laurenceb> then a second stage using spun solid
[12:32] <Laurenceb> similar to CU spaceflight martlet
[12:32] <Laurenceb> that way you can get maybe 100 grams into LEO
[12:32] <Laurenceb> with about 35Kg GLOW from a balloon
[12:32] <Laurenceb> its the most feasible way to do it I think
[12:32] <mc_-> what glow to orbit 20g?
[12:33] <Laurenceb> the same
[12:33] <mc_-> maybe 30kg?
[12:33] <Laurenceb> hmm I'm not sure how it scales
[12:33] <Laurenceb> I was set my the solid motor I chose
[12:34] <mc_-> true
[12:34] <Laurenceb> there may be a few tricks in changing the motor size
[12:34] <Laurenceb> but you will soon suffer from the weight of the electronics and guidance on the first stage
[12:34] <Laurenceb> you might be able to get it down to 20Kg if your lucky
[12:35] <mc_-> can you call the motor casing the satellite for the nprize?
[12:35] <Laurenceb> yes if you can track it and it weighs < 20 grams
[12:35] <Laurenceb> but small motors are less efficient
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[12:36] <Laurenceb> its easy to fit a small radio bleeper on the front
[12:36] <Laurenceb> the trick is firing the second stage ok
[12:36] <mc_-> but they accelerate more the last second
[12:36] <Laurenceb> I think a couple of flywheels would work
[12:37] <Laurenceb> epoxy encapsulated transmitter
[12:37] <mc_-> flywheels for what?
[12:37] <mc_-> guidance?
[12:37] <Laurenceb> controlling the first stage attitude
[12:37] <Laurenceb> after burnout it coasts up to 200Km
[12:38] <Laurenceb> you need very good poiting when you fire the second stage out of its launch tube
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[12:42] <Laurenceb> the good new as as long as the second stage is lighter than the burnt out engine it will be passively stable
[12:42] <Laurenceb> so you only need very slow control from the flywheels
[12:42] <Laurenceb> so they can be very light
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[12:45] Nick change: zsircusr2 -> mc_
[12:46] <mc_> the flywheels would control tumbling
[12:46] <mc_> how would they help with pointing the top stage?
[12:47] <Laurenceb> the top is spin stabilised
[12:47] <Laurenceb> launching out of a plastixc tube
[12:47] <Laurenceb> with some blades built into the sides to act as rifling
[12:48] <mc_> are the flywh on the top stage?
[12:48] <Laurenceb> no
[12:48] <Laurenceb> on the first stage
[12:48] <mc_> ok got it
[12:48] <Laurenceb> they get it level to the horizon when it fires the secon stage
[12:49] <mc_> the loki launcher has rifling on it
[12:49] <Laurenceb> if you use high spec carbon fibre you should be able to get the mass fraction of the first stage to about 9%
[12:50] <mc_> pressure fed?
[12:50] <Laurenceb> then have the second stage make up around another 9%
[12:50] <Laurenceb> yes
[12:50] <Laurenceb> ~4.3Km/s deltav fron the first then similar from the second
[12:50] <Laurenceb> second also needs a similar mass fraction
[12:50] <Laurenceb> but it only has a very small payload
[12:51] <Laurenceb> so thats a bit easier
[12:51] <Laurenceb> also its a solid so theres less pressure vessle
[12:51] <Laurenceb> something like an O class motor
[12:52] <Laurenceb> or N or something
[12:52] <mc_> so it stages when its moving around 4km/s?
[12:54] <Laurenceb> sorry L class
[12:54] <Laurenceb> yeah
[12:54] <Laurenceb> fires from a balloon into a gravity turn
[12:55] <Laurenceb> then fires the second horizontally at apogee
[12:55] <mc_> your 1st stage has to do alot...
[12:55] <Laurenceb> http://www.pro38.com/products/pro75/motor.php
[12:56] <Laurenceb> L800-P would work
[12:56] <mc_> and its hard to recover
[12:56] <Laurenceb> not really
[12:56] <Laurenceb> well its going to fly a very long way :P
[12:56] <Laurenceb> several hundered Km
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[12:57] <Laurenceb> it probably wouldnt be worth it
[12:57] <Laurenceb> as the motor would be damaged anyway
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[12:57] <Laurenceb> the CF tube would actually be pretty cheap
[12:58] <Laurenceb> the most expensive things would be the nozzle and electronics
[12:58] <SpeedEvil> The CF tube gets mainly destroyed due to heat-soak at the end
[12:58] <Laurenceb> exactly
[12:58] <mc_> its difficult to test without getting things back
[12:58] <SpeedEvil> Protecting it from that would be quite heavy
[12:58] <Laurenceb> also reentry heating
[12:59] <Laurenceb> mc_ youd have 868MHz 500Mw transceiver on the first stage
[12:59] <Laurenceb> so you could talk to it all the time
[12:59] <mc_> i guess test flights could go straight up
[12:59] <Laurenceb> so youd have a good idea
[12:59] <Laurenceb> yeah you could reach 100Km with the first stage
[12:59] <Laurenceb> thats be a good record
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[13:01] <Laurenceb> I'd be tempted to use an off the shelf 868MHz modem, analogue devices IMU, thermopiles and gps
[13:01] <Laurenceb> then maybe something running a real time linux kernel...
[13:02] <Laurenceb> TVC with three high temperature stainless steel jet vanes
[13:02] <SpeedEvil> Laurenceb: Sponsorship from apple - use an iphone. :)
[13:02] <Laurenceb> heh
[13:02] <Laurenceb> the gps is good
[13:02] <Laurenceb> antenna probably a bit lacking
[13:03] <mc_> did you have a go using pranges to calculate a gps position?
[13:03] <Laurenceb> not yet
[13:03] <Laurenceb> I'm going to have a go tho
[13:03] <Laurenceb> with ucenter
[13:04] <mc_> im interested how it goes
[13:04] <SpeedEvil> meto
[13:05] <Laurenceb> we have a sounding rocket and several orbital scenarios
[13:05] <Laurenceb> I'll setup my ublox5 in the test chamber and see :P
[13:05] <SpeedEvil> test chamber?
[13:06] <Laurenceb> for satellites
[13:06] <Laurenceb> - just RF not thermal vac
[13:06] <SpeedEvil> you've got a GPS sim?
[13:06] <mc_> if it can nav at ground level it should work at any alt
[13:07] <Laurenceb> they do at SSTL
[13:07] <SpeedEvil> mc_: assumng that the code can do a position solution at 9km/s
[13:08] <SpeedEvil> or that the PLLs lock
[13:08] <SpeedEvil> Or is this te blackfin thing
[13:08] <Laurenceb> the PLLs may responds badly to the accel
[13:08] <Laurenceb> no, using a ublox5
[13:08] <SpeedEvil> this is for stage 1 only?
[13:08] <Laurenceb> yes
[13:09] <SpeedEvil> what's terminal V?
[13:09] <Laurenceb> ~4.4Km/sec
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[13:10] <SpeedEvil> The PLLs may not tune that far
[13:11] <Laurenceb> yeah but only if they did a sanity check or something is firmware
[13:11] <Laurenceb> it way well work
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[13:12] <mc_-> is that a typical price or just end of life stuff?
[13:12] <SpeedEvil> Or simply the PLL tuning registers are designed for 'sane' velocities.
[13:12] <SpeedEvil> mc_-: for what?
[13:12] <SpeedEvil> mc_-: oh
[13:12] <SpeedEvil> mc_-: I don't know
[13:12] <SpeedEvil> mc_-: There does seem to be a fair bit from a number of sellers.
[13:13] <SpeedEvil> mc_-: 12K tow is quite thick though
[13:13] <SpeedEvil> you can't use it for making really fine structures
[13:13] <Laurenceb> 0.6mm is good for pressurized tanks
[13:14] <SpeedEvil> sqrt(12K) is what - 110 - so 100*7um = probably around a milimeter in diameter total.
[13:14] <SpeedEvil> but for tanks, you'd need biaxial, so you're looking at possibly more like a milimeter and a half to two - though I'm not quite sure how it'd flatten
[13:15] <Laurenceb> ideally you want 2:1
[13:15] <Laurenceb> biaxial stuff
[13:15] <mc_-> i wonder if a small filament winder is feasible?
[13:15] <Laurenceb> but I was doing the numbers with 1:1
[13:15] <Laurenceb> youd need a liner
[13:16] <Laurenceb> probably too much work when you can buy tube pretty much off the shelf
[13:16] <SpeedEvil> mc_-: sure
[13:17] <SpeedEvil> mc_-: The mmore complex you want it to get - number of axes, non-cylindrical, ... it gets harder.
[13:18] <mc_-> yes, ppl pay lots of money for cf bike parts
[13:18] <Laurenceb> with a regen chamber and piston pump SSTO from a balloon is possible
[13:18] <mc_-> might be a way to earn some money for rockets
[13:18] <Laurenceb> 100Kg glow
[13:18] <Laurenceb> 1Kg to orbit
[13:19] <Laurenceb> also for pumped, methanol may work slightly better
[13:19] <SpeedEvil> lower visc?
[13:19] <Laurenceb> yes, and more predictable cooling properties
[13:19] <Laurenceb> also O/F is 3.2
[13:19] <Laurenceb> rather than 7.3
[13:19] <Laurenceb> and ISP is 2% higher
[13:19] <mc_-> doesnt matter if a winder takes weeks to build a tube
[13:20] <Laurenceb> but the tank is 6.5% larger
[13:20] <Laurenceb> the idea is to make it easy
[13:20] <Laurenceb> - winder isnt easy
[13:21] <mc_-> whats hard to do ?
[13:21] <Laurenceb> I'm not sure what % of heat goes through the chamber walls
[13:21] <Laurenceb> but kerosene is limited to 1.3%
[13:21] <Laurenceb> whereas methanol is about 4%
[13:21] <Laurenceb> filament winder
[13:23] <SpeedEvil> mc_-: go and wind a nice oriented ball of string.
[13:23] <SpeedEvil> It's not trivial
[13:24] <Laurenceb> http://www.graphitestore.com/itemDetails.asp?item_id=3336&prd_id=26&cat_id=22&curPage=2
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[13:25] <Laurenceb> thatd do for the nozzle
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[13:26] <mc_-> i think steppers would be accurate enough to wind in the axial direction
[13:27] <Laurenceb> but... why
[13:27] <Laurenceb> when you can buy CF tube
[13:27] <SpeedEvil> the gain is fairly small.
[13:27] <Laurenceb> and the bulkheads arent that significant weight wise
[13:27] <mc_-> i dont think cf tube is strong enough
[13:27] <Laurenceb> you can get about 30%
[13:28] <Laurenceb> its not very significant
[13:28] <Laurenceb> for the effort you may as well build a piston pump
[13:29] <SpeedEvil> Err - what?
[13:29] <SpeedEvil> You're proposing making CF tube.
[13:29] <SpeedEvil> Or CF tanks
[13:29] <SpeedEvil> which are the same thing more or less neglecting the bulkheads
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[13:33] <Laurenceb> if you add some methanol and catalyst to the kerosene you can make it hyperglolic
[13:34] <SpeedEvil> I thought of that - I couldn't find any references to how well it'd work
[13:35] <Laurenceb> theres a chinese paper
[13:35] <Laurenceb> apparently works very well
[13:35] <Laurenceb> but they dont give the % methanol you need to get enough permanganate to dissolve
[13:36] <SpeedEvil> yeah - I wasn't sure if the permaganate would react with the methanol
[13:36] <Laurenceb> it will dissolve in kerosene directly, but only at very low percentages
[13:36] <SpeedEvil> I was thinking of basically an emulsion
[13:36] <Laurenceb> also keytones work
[13:36] <Laurenceb> apparently not
[13:36] <SpeedEvil> Or some soap-based solution.
[13:36] <SpeedEvil> Or even colloidal silver
[13:36] <Laurenceb> I could understand the engrish
[13:37] <Laurenceb> but it didnt appear to be an emulsion
[13:37] <SpeedEvil> Methanol is miscible in kerosene?
[13:37] <Laurenceb> yes
[13:37] <SpeedEvil> Oh.
[13:38] <Laurenceb> apparently
[13:38] <Laurenceb> I was thinking with two piston pumps you can do 4 port nozzle injection with the exhaust
[13:39] <SpeedEvil> umm
[13:39] <Laurenceb> if there was just a way to do the injection without pumping you could do crude pointing
[13:39] <Laurenceb> then hyperglolic propellant and youve got a "space tug"
[13:39] <SpeedEvil> you mean just dump, or output propulsively?
[13:40] <SpeedEvil> with the exhausts - as an option
[13:40] <Laurenceb> into the end of the nozzle
[13:40] <Laurenceb> to direct the exhaust stream
[13:40] <SpeedEvil> I mean - you either dump the propellant, or use it at the appropriate place in the nozzle
[13:41] <SpeedEvil> with a solenoid or something per exhaust
[13:41] <Laurenceb> nope
[13:41] <Laurenceb> if you use pwm with the injection you dont need any more hardware
[13:42] <Laurenceb> you can control the exhaust from each side of each piston
[13:42] <SpeedEvil> Isn't the exhaust constant per stroke?
[13:42] <Laurenceb> no
[13:42] <SpeedEvil> If you want to maintain an output pressure
[13:42] <Laurenceb> there has to be a regulator to stop horrible vibration
[13:43] <Laurenceb> as a side effect of this you can pwm the injection
[13:43] <Laurenceb> and use the exhaust for attitude control
[13:43] <SpeedEvil> I was assuming a accumulator
[13:44] <Laurenceb> or that would probably work too
[13:46] <SpeedEvil> well - accumulators
[13:50] <Laurenceb> fuel +ox
[13:52] <Laurenceb> I was thinking of a composite overwrapped engine liner
[13:52] <Laurenceb> made from copper or alu
[13:52] <SpeedEvil> yeah
[13:52] <SpeedEvil> dump cooled?
[13:52] <Laurenceb> no
[13:52] <Laurenceb> inner liner with ribs
[13:53] <Laurenceb> then fill the channels with wax and overwrap maybe
[13:53] <Laurenceb> vertical channels going up and down
[13:54] <SpeedEvil> I mean - dump it out the end - not regenerate
[13:54] <SpeedEvil> or full regenerative
[13:54] <Laurenceb> full
[13:54] <Laurenceb> maybe an adaptor ring around the top
[13:54] <Laurenceb> CNC milled with channels to connect everything up
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[13:57] <Laurenceb> top of the chamber is the fuel tank bottom, so its cooled by the fuel
[14:04] <Laurenceb> what I dont understand about your electrodeposition idea is how you attach the fins
[14:08] <SpeedEvil> you electrodeposit them
[14:08] <SpeedEvil> take a cylinder
[14:09] <SpeedEvil> now, place square rods of wax round it
[14:09] <SpeedEvil> with gaps
[14:09] <SpeedEvil> and electrodeposit to fill the gaps
[14:09] <SpeedEvil> doing this for a complex geometry is of course more annoying
[14:10] <Laurenceb> yeah a lot more
[14:10] <Laurenceb> hmm maybe you could solder strips on
[14:10] <Laurenceb> and then you may as well spin the inner casing
[14:10] <Laurenceb> so no electrodeposition needed
[14:12] <Laurenceb> http://imgur.com/URaQW.png
[14:12] <SpeedEvil> preliminary tests indicated it was possible
[14:13] <Laurenceb> doing a chamber and nozzle would be hard
[14:16] <SpeedEvil> spun chamber, electrodeposited fins, finish with lathe, then spin on a heated metal outside
[14:16] <SpeedEvil> so it shrink-fits
[14:16] <SpeedEvil> at least that was the theory
[14:16] <Laurenceb> argg
[14:17] <Laurenceb> spun chamber, soldered on fins, cut to smooth finish on lathe, then fill recesses with wax and wrap with composite
[14:17] <Laurenceb> easier
[14:18] <Laurenceb> soldering the fins is a pain tho
[14:21] <SpeedEvil> maybe
[14:24] <Laurenceb> you could build a jig to hold the fins in place then electroplate onto them
[14:24] <Laurenceb> so use thins sheet for the fins
[14:28] <Laurenceb> how do you do the spinning for the chamber? start with sheet?
[14:30] <SpeedEvil> tube
[14:35] <Laurenceb> can you get seamless tube that size?
[14:39] <SpeedEvil> for large stuff - yes - sheet
[14:44] <Laurenceb> joined into a tube?
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[14:52] <SpeedEvil> yes
[14:59] <Laurenceb> guess you can use thin sheet and plate over everything
[15:01] <SpeedEvil> carbon-loaded beeswax is traditional
[15:23] <jcoxon> hey Laurenceb and SpeedEvil
[15:44] <Laurenceb> hi
[15:44] <Laurenceb> http://www.efunda.com/formulae/fluids/calc_pipe_friction.cfm#calc
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[16:19] <jcoxon> hey RocketBoy
[16:42] <Laurenceb> SpeedEvil: you could buy thinwall copper tube and make a jig for bending it
[16:43] <Laurenceb> then something to clamp it over the liner whist its electroplated
[16:48] <Laurenceb> pass through rollers to make it square
[16:48] <Laurenceb> then a jig to bend it the the right shape
[16:49] <Laurenceb> then something as simple as cable ties around the liner before more plating
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[17:43] <jcoxon> anyone around?
[17:45] <DanielRichman> Hello
[17:46] <jcoxon> hey
[17:46] <DanielRichman> How are you?
[17:46] <jcoxon> good thanks
[17:47] <jcoxon> need some ideas for a logo for atlantic halo (trans-atlantic attempt)
[17:47] <DanielRichman> Does the jetstream ever go the other way?
[17:48] <jcoxon> not really
[17:48] <DanielRichman> So are you launching in america?
[17:48] <DanielRichman> and trying to get to Europe?
[17:49] <jcoxon> yes
[17:49] <jcoxon> thats the plan
[17:49] <jcoxon> have you seen the wiki?
[17:49] <DanielRichman> Logo... hmm
[17:49] <DanielRichman> just looking it up actually ;)
[17:50] <jcoxon> we have fallen behind a little recently
[17:50] <DanielRichman> Oh so natrium will be launching
[17:50] <jcoxon> but my next launch is going to be ballasthalo 1
[17:50] <DanielRichman> Are any of you planning to go over there ?
[17:50] <jcoxon> so prepare to test the ballast tanks
[17:50] <jcoxon> DanielRichman, probably not
[17:50] <jcoxon> we'll be here to receive
[17:50] <DanielRichman> ahh, ok
[17:50] <DanielRichman> Says you have permission
[17:51] <DanielRichman> Were there difficulties?
[17:51] <jcoxon> permission?
[17:51] <jcoxon> tis a job in progress
[17:51] <jcoxon> no permission yet, Nav Canada and the FAA aren't too sure how to approach the concept
[17:51] <jcoxon> so they are working something out
[17:52] <DanielRichman> cool
[17:52] <jcoxon> well that was the situation last time we had the 'big meeting'
[17:53] <jcoxon> need a logo though
[17:53] <DanielRichman> Can't think of anything so far, sorry
[17:53] <jcoxon> and my brain is revision mush right now
[17:53] Action: DanielRichman looks at previous HALO logos
[17:54] Action: DanielRichman fails to find them
[17:54] <DanielRichman> It's the Pegasus launches that all have logos, right?
[17:54] <jcoxon> ummm pegasus have some logos
[17:55] <jcoxon> its more that i've submitted the next flight to the ARHAB launch list
[17:55] <jcoxon> and they quite like a logo
[17:55] <jcoxon> to go in the table
[17:56] <DanielRichman> Well although Halo is High Altitude Object, it's almost (something) AtLantic Ocean
[17:57] <jcoxon> didn't see that before - clever
[17:58] <DanielRichman> But apart from that I have no ideas, sorry :(
[17:58] <jcoxon> no worries
[17:58] <jcoxon> i'll keep on thinking
[17:58] <jcoxon> hows your payload?
[17:59] <DanielRichman> Going good, I'm juggling working on another project and writing a SD-Card Driver
[18:01] <DanielRichman> (Logo-wise) I guess you need to decide if you want to go for the typical green/blue map with an arrow between america & europe or something else
[18:05] <jcoxon> yeah
[18:05] <jcoxon> right i'll bbiab, thanks for the ideas
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[19:45] <rjharrison> Evening all
[19:48] <rjharrison> sbasuita: How are you guys getting on
[19:48] <rjharrison> near launch yet?
[19:48] <DanielRichman> rjharrison, I'm juggling working on another project and writing a SD-Card Driver
[19:53] <rjharrison> Oh
[19:53] <rjharrison> so DanielRichman you are on pause atm
[19:55] <DanielRichman> yes
[19:55] <DanielRichman> well
[19:55] <DanielRichman> sort of
[19:55] <rjharrison> is the SD card for AVR or ARM?
[19:56] <DanielRichman> avr
[19:56] <rjharrison> hehe cool
[19:56] <DanielRichman> yeah. pooling on the 140 page spec and two example implementations to try and make a non-blocking version
[19:56] <rjharrison> Are you doing fat or lust overwting a pre initialised file
[19:56] <DanielRichman> neither
[19:56] <DanielRichman> No filesystems involved
[19:57] <DanielRichman> just start at byte 0 and write.
[19:57] <rjharrison> Cool
[19:57] <DanielRichman> though I might have a 'superblock' of sorts with a pointer to the last byte written, so it can pick up where it left off
[19:57] <rjharrison> and then your avr will have to read back the data too unless you write a reader
[19:58] <DanielRichman> nah, Linuxxx can do it
[19:58] <DanielRichman> cat /dev/sdb1 shoudl do the trick?
[19:58] <rjharrison> True
[19:58] <rjharrison> or dd
[19:59] <DanielRichman> yes
[19:59] <DanielRichman> anyway; bbiab
[20:17] <SpeedEvil> you can take a fat formatted card, make one huge file on it.
[20:17] <SpeedEvil> and then treat that as a virtual device
[20:18] <SpeedEvil> so you can access /bigfile on device a a FS
[20:18] <SpeedEvil> without actually bothering with FS stuff, you just write to the big file
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[21:20] <sbasuita> DanielRichman, do we need anything for school this week?
[21:20] <DanielRichman> sbasuita, hahahaha
[21:20] <DanielRichman> :)
[21:20] <DanielRichman> (no).
[21:21] <DanielRichman> sbasuita, I think i will bring writing stuff... and that's it
[21:21] <sbasuita> ok, so that consists of finding a biro and shoving it one's pocket
[21:21] <DanielRichman> What's wrong with your current pens?
[21:22] <DanielRichman> BTW: Register is in big school 8:25 irrc
[21:22] <sbasuita> nothing really... I have a selection in front of me
[21:22] <Laurenceb> SpeedEvil: for a regen chamber, spin copper foil over a former, then use a jig to bend lenghts of thinwall copper tube ~1mm diameter over it
[21:23] <Laurenceb> then electroplate ~0.2mm of copper over the top, then overwrap
[21:31] <Laurenceb> http://img1.picturewizard.com/1328F50/0/Communism.gif
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[21:43] <SpeedEvil> Laurenceb: maybe
[21:43] <SpeedEvil> Laurenceb: seemed very tricky to get it adhered well
[21:43] <Laurenceb> you need a jig to hold it all in place
[21:43] <Laurenceb> then submerge in the bath
[21:44] Nick change: peddie_ -> peddie
[21:44] <SpeedEvil> I'm unsure it's practical to plate under tubes
[21:45] <Laurenceb> it doesnt have to go under them
[21:45] <Laurenceb> as long as they are fixed at the edges
[21:45] <SpeedEvil> Umm.
[21:45] <Laurenceb> as copper is so thermally conductive
[21:45] <SpeedEvil> probably
[21:46] <Laurenceb> alternativelty spin aluminium and mill out the channels with a cnc mill
[21:47] <Laurenceb> which ends up about 20% heavier
[21:47] <Laurenceb> but has greater structural margins
[21:48] <Laurenceb> not sure how well you can spin aluminium alloy
[22:06] <Laurenceb> hmm apparently not very well
[22:07] <Laurenceb> between 15 and 60% elongation, and the lower quality alloys elongte less
[22:07] <SpeedEvil> Annealing works well
[22:10] <Laurenceb> anneal then continue working it?
[22:10] <Laurenceb> guess so
[22:10] <Laurenceb> I've done a bit of copper turning bit it was ages ago
[22:11] <SpeedEvil> I even experimented with spinning steel
[22:11] <SpeedEvil> worked OK.
[22:11] <SpeedEvil> For mild steel
[22:11] <SpeedEvil> with annealing.
[22:11] <SpeedEvil> However I wa limited on my lathe
[22:11] <SpeedEvil> I need to fix the spindle
[22:13] <Laurenceb> you could just buy a huge 12'' by 7'' rod
[22:13] <Laurenceb> would cost about as much as graphite tho
[22:13] <Laurenceb> ~£200
[22:14] <SpeedEvil> Of Al?
[22:14] <SpeedEvil> I'm unsure how trivial that is to machine
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[22:24] <Laurenceb> hmm apparently you should anneal several times during the spinning for it to work
[22:24] <Laurenceb> makes sense now
[22:26] <Laurenceb> need a small furnace
[22:26] <Laurenceb> fire bricks + gas torch works
[22:26] <Laurenceb> and an IR thermometer
[22:27] <SpeedEvil> or a pizza oven
[22:29] <Laurenceb> should take 4 or so annealing treatments to get the initial tube into shape
[22:30] <Laurenceb> then take the thickness down on the lathe, and then mill in the cooling channels
[22:31] <Laurenceb> coat with wax, then cut off excess wax, treat exposed alu to promote adhesion and overwrap
[22:35] <Laurenceb> how accurate could the channels be milled?
[22:35] <Laurenceb> 1mm wall thickness?
[22:42] <SpeedEvil> No idea really.
[22:42] <SpeedEvil> At the throat, you want them as small as you can
[22:42] <SpeedEvil> You want all of the channels to go past the throat
[22:45] <Laurenceb> yeah, make the fins higher
[22:46] <SpeedEvil> You want the flow to be nice and fast
[22:46] <SpeedEvil> which means small channels - otherwise you can get runaway bubble formation at hot-spots
[22:46] <Laurenceb> your limited how much heat you can chuck in
[22:47] <Laurenceb> I'm not sure how well it works with kerosene
[22:47] <Laurenceb> methanol would probably work, and offer a slight performance increase
[22:47] <Laurenceb> kerosene is rather poorly defined stuff
[22:47] <SpeedEvil> yeah
[22:48] <Laurenceb> you dont know what is going to do at 200C
[22:48] <SpeedEvil> and it can coke
[22:48] <SpeedEvil> RP-1 is specially processed to avoid that
[22:48] <SpeedEvil> I suspect something like 99.9% hexane or something might avoid that
[22:48] <Laurenceb> you could use the peroxide, I suspect black arrow did that
[22:48] <SpeedEvil> As you don't care at all about price
[22:48] <Laurenceb> but then you have to carry more fluid
[22:48] <Laurenceb> and its more viscous and denser
[22:48] <SpeedEvil> hexane or octane is more or less the same as kero though
[22:49] <SpeedEvil> oh
[22:49] <Laurenceb> yeah, if you can source it
[22:49] <SpeedEvil> Peroxide cooling can go very wrong
[22:49] <SpeedEvil> as you've got the nasty thermal runaway issue
[22:49] <Laurenceb> yeah
[22:50] <Laurenceb> well I think you can get the engine mass down to ~1Kg
[22:51] <Laurenceb> for a 2.3KN engine
[22:52] <Laurenceb> exit pressure ~12PSI
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[23:47] <Laurenceb> I'm pretty sure SSTO is possible with a design like this balloon launched
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[00:00] --- Mon Jul 6 2009