highaltitude.log.20090708

[00:35] <Laurenceb> http://imagebin.org/54925
[00:36] <SpeedEvil> Something silly in me says to put the launch tube inside the tank
[00:36] <SpeedEvil> but that's probably a bad plan
[00:36] <Laurenceb> it helps to make it streamlined doing it like that
[00:36] <Laurenceb> tho you have to make a fairly massive shroud
[00:37] Action: SpeedEvil is very tired ATM - so full appreciation of your high resolution realistically rendered image may have to wait.
[00:37] <Laurenceb> :P
[00:38] <Laurenceb> dia ftw
[00:38] <SpeedEvil> what's the graphite attached with?
[00:38] <SpeedEvil> that's the ceramic - clamped by something?
[00:42] <Laurenceb> graphite attatched with a two piece ceramic collar
[00:42] <Laurenceb> then a two piece alu collar on top of that
[00:43] <SpeedEvil> hmm
[00:43] <Laurenceb> threaded to screw into the bottom
[00:43] <SpeedEvil> the aluminium is hoped to conduction cool to the fueltank/
[00:43] <Laurenceb> theres very little heat into the alu
[00:43] <Laurenceb> <200watts
[00:43] <SpeedEvil> prolly want the bottom of the tank to be concave
[00:43] <SpeedEvil> relly?
[00:43] <Laurenceb> yes
[00:44] <SpeedEvil> oh
[00:44] <SpeedEvil> the phenolic
[00:44] <Laurenceb> you can get very good ceramic insulator
[00:44] <Laurenceb> rs sell some nice stuff thatd work fine
[00:44] <Laurenceb> yep
[00:45] <Laurenceb> prob want two grub screws to clamp the alu collar
[00:47] <Laurenceb> you probany want a fuel sensor or two at the bottom of the fuel tank, pref make an rs485 sensor
[00:47] <Laurenceb> then you can run an rs485 bus around all the servos, and use high voltage rs485 robotics servos
[00:49] <Laurenceb> http://www.trossenrobotics.com/dynamixel-rx-28-robot-actuator.aspx
[00:54] <Laurenceb> http://robosavvy.com/site/index.php?option=com_content&task=view&id=183&Itemid=135 <- nice
[00:54] <SpeedEvil> hmm
[00:56] <Laurenceb> 40 grams
[00:59] <SpeedEvil> That's not _horribly_ priced
[01:00] <Laurenceb> yeah, competitive with gumsticks
[01:00] <Laurenceb> and nicer to work with
[01:00] <Laurenceb> - x86
[01:01] <SpeedEvil> I don't see - x86 Processor uses less than 1 W - DC input from 6V~24V, at 2W. (that's 0.3Amp at 6V .. less than a servo)
[01:01] <Laurenceb> hmm stick the vga board on and youve got a netbook
[01:01] <SpeedEvil> what that means
[01:01] <Laurenceb> heh
[01:03] <SpeedEvil> esp given the mention of 2W elsewhere
[01:10] <Laurenceb> http://www.trossenrobotics.com/futaba-rs301cr-robot-servo.aspx
[01:10] <Laurenceb> nice - perfect for the jet vane control
[01:12] <SpeedEvil> what's the exhaust temp?
[01:12] <SpeedEvil> at the vanes
[01:14] <Laurenceb> ~800C
[01:15] <Laurenceb> youd have the servos somewhere on the outside on the chamber casing
[01:15] <Laurenceb> then stainless tube pushrods
[01:15] <Laurenceb> http://www.crustcrawler.com/motors/RX28/docs/RX28_Manual.pdf <- these things are nice
[01:16] <SpeedEvil> you do know that you get shocks hitting the vanes - which heat the gas up to pretty much the same temp as in the chamber?
[01:17] <Laurenceb> hmm
[01:17] <Laurenceb> that sucks
[01:18] <SpeedEvil> hence my initial mention of graphite vanes
[01:18] <Laurenceb> but thats only at the leading edge?
[01:21] <SpeedEvil> If the vane is at 0 degrees
[01:21] <SpeedEvil> otherwise it's a similar environment to flying at mach 15 or so at sea level.
[01:22] <Laurenceb> yeah
[01:22] <Laurenceb> maybe theres some high temperature alloy you could use
[01:22] <Laurenceb> only needs a little bit
[01:23] <SpeedEvil> Yeah.
[01:23] <SpeedEvil> Pt/Ir should work well.
[01:24] <Laurenceb> http://www.goodfellow.com/E/Platinum-IridiumFoil.html
[01:26] <SpeedEvil> It's pretty much the same environment as a radiation cooled chamber would be.
[01:26] <SpeedEvil> As I understand it.
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[01:30] <Laurenceb> http://cgi.ebay.com/Tungsten-Sheet-Plate-6-x6-x0-02-99-95-Purity_W0QQitemZ390009862468QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5ace663944&_trksid=p3286.m20.l1116
[01:30] <Laurenceb> tungsten?
[01:30] <SpeedEvil> As I recall, tungsten is not very inert at all at high temps
[01:31] <SpeedEvil> I don't know exactly what it'd do of course
[01:31] <SpeedEvil> and how critical the fuel mix to get it to not do that would be
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[01:35] <Laurenceb> tungsted carbide has been used
[01:53] <Laurenceb> got it
[01:53] <Laurenceb> carbon fibre silicon carbide disc brakes
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[02:10] <SpeedEvil> hmm
[02:10] <SpeedEvil> maybe
[02:19] <Laurenceb> hard to get hold of
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[02:53] Nick change: KingJ -> kingj
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[13:09] Nick change: kingj -> KingJ
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[14:09] <Laurenceb> hello
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[14:11] <Laurenceb> hi jcoxon
[14:11] <jcoxon> hey Laurenceb
[14:12] <Laurenceb> whens launch?
[14:12] <jcoxon> still not sure
[14:12] <Laurenceb> and what are you using as the leak?
[14:12] <jcoxon> weather this weekend is not looking great
[14:12] <Laurenceb> :(
[14:12] <jcoxon> probably some waste piping and a cap with a hole in it
[14:12] <Laurenceb> yeah
[14:22] Nick change: KingJ -> kingj
[14:25] <Laurenceb> SpeedEvil: there is another option - vectored nozzle
[14:35] Nick change: kingj -> KingJ
[14:37] <SpeedEvil> yeah
[14:37] Action: SpeedEvil gyres and gimabls in the wabe.
[14:38] <SpeedEvil> I am unsure how smooth the nozzle has to be
[14:38] <SpeedEvil> one option I thought of was a assymetric nozle.
[14:39] <Laurenceb> I was thinking shape the aluminium attatchment flange
[14:39] <Laurenceb> so its able to rotate +-3 degrees or so
[14:39] <SpeedEvil> For example - cut off the nozzle at an angle, and you get a off-axis thrust component
[14:39] <Laurenceb> yeah, you cant control roll
[14:39] <SpeedEvil> If you make the end of the nozzle able to spin, ...
[14:40] <Laurenceb> lol
[14:40] <Laurenceb> I'm not sure if its important
[14:40] <SpeedEvil> or you have patches of the end of the 'nozzle' that can be removed
[14:40] <SpeedEvil> roll control is important if you don't have a rapid enough gimbal response
[14:40] <Laurenceb> yes
[14:40] <Laurenceb> maybe you could do it using the injector
[14:40] <SpeedEvil> ?
[14:41] <Laurenceb> spin the fuel
[14:41] <SpeedEvil> no - the throat acts like a wall
[14:41] <Laurenceb> hmm yeah
[14:44] <Laurenceb> I know, 4 nozzles
[14:48] <SpeedEvil> I don't know how rough a nozzle can be before you get complete discontinuity in flow.
[14:49] <SpeedEvil> If you add/remove a nozzle extension section with a servo
[14:49] <SpeedEvil> So you expand more on one side than the other
[14:50] <SpeedEvil> Heat flux at teh end of the nozzle is nominally very low.
[14:50] <SpeedEvil> But may not be if you get the discontinuity wrong
[14:54] <Laurenceb> hmm isnt the exhaust flow ionised?
[14:55] <SpeedEvil> No.
[14:55] <SpeedEvil> Looking at the reference frame of a particle of exhaust
[14:56] <SpeedEvil> As it goes through the throat, it's moving at the speed of sound, at a really high temperature.
[14:56] <SpeedEvil> As it moves along the nozzle, it expands and cools, with - from the point of view of the exhaust gas - a temperature that can approach freezing.
[14:57] <SpeedEvil> If you dip something into the exhaust though it gets _very_ hot though.
[14:58] <Laurenceb> yeah
[14:58] <SpeedEvil> Ideally the gas has finished reacting by the time it's gone through the throat
[15:01] <SpeedEvil> http://www.volkswagen.co.uk/volkswagen-world/futures/1-litre-car
[15:01] Action: SpeedEvil hates to think what a minor bump would cost to repair.
[15:02] <Laurenceb> heh
[15:03] <SpeedEvil> Also.
[15:03] <SpeedEvil> CF coloured tiny car - I want mine _bright_ orange.
[15:03] <SpeedEvil> If it's that low to the ground.
[15:04] <Laurenceb> I guess theres injection TVC
[15:05] <SpeedEvil> yeah
[15:05] <Laurenceb> but thast requires solenoid valves
[15:05] <Laurenceb> gymballed nozzle is probably easier
[15:05] <SpeedEvil> at least two
[15:05] <Laurenceb> just the roll issue grrr
[15:05] <Laurenceb> yeah you need two
[15:08] <Laurenceb> or four attitude control nozzles at the top
[15:08] <Laurenceb> using peroxide
[16:16] <jcoxon> hey all
[16:17] <jcoxon> exam finished :-)
[16:17] <jcoxon> hopefully free untill october (unless i have to retake :( )
[16:19] <SpeedEvil> Good luck! Look ok?
[16:19] <jcoxon> it was really hard
[16:19] <jcoxon> glad its over
[16:21] <jcoxon> right now to do some ballooning
[16:21] <jcoxon> really wanted to launch this weekend but it looks horrible
[16:21] <jcoxon> ping edmoore
[16:21] <edmoore> yo
[16:21] <edmoore> well done on finishing
[16:21] <edmoore> advanced warning i'm a bit distracted with work atm but fire away
[16:22] <jcoxon> are you now in cambridge for a while?
[16:23] <edmoore> all summer pretty much
[16:23] <jcoxon> okay cool
[16:23] <jcoxon> looks like i'm going to scrub this weekend
[16:23] <jcoxon> weather is just too dodgey
[16:23] <edmoore> doesn't look so good does it
[16:23] <jcoxon> typical, miss all the good weather last week
[16:24] <jcoxon> so i'll aim for one day next week
[16:24] <jcoxon> well one evening next week - would that be possible from Churchill?
[16:24] <Laurenceb> jcoxon: good luck
[16:24] <edmoore> I'm around whenever, save for weekend of 26th/27th
[16:24] <edmoore> yep, no problem
[16:25] <jcoxon> cool, im concious of time, i'm off at the end of hte month - would like to get this one in the air asap
[16:27] <jcoxon> thats all i need to ask
[16:27] <jcoxon> right going to play halo 3 for a while, - time to chill finally
[16:27] <edmoore> yep, just shout when the weather looks good.
[16:29] <jcoxon> bbl
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[17:24] <Laurenceb> SpeedEvil: the other option is two small fins for roll control
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[17:54] <Laurenceb> gtg, cya all
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[17:58] Nick change: G8KHW-2 -> RocketBoy
[17:59] <RocketBoy> I now have a daily permit for EARS until July 24th
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[18:09] <jcoxon> back
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[18:34] <Laurenceb> hello
[18:34] <RocketBoy> The weekend JS WX isn't looking good :-(
[18:35] <jcoxon> indeed
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[18:41] <jcoxon> hopefully some nice weather will appear next week
[18:41] <jcoxon> we missed some nice JS last week
[18:48] <RocketBoy> yeah
[18:48] <RocketBoy> on the plus side the July EARS rocketry launch is on this Sunday
[18:50] <jcoxon> oh cool
[18:50] <jcoxon> might pop up
[18:58] <jcoxon> wow just tested my nichrome wire cutdown
[18:58] <Laurenceb> eeek high current
[18:58] <Laurenceb> :P
[18:58] <jcoxon> completely melted the line over about 8cm
[18:59] <jcoxon> i'm impressed
[18:59] <Laurenceb> but how much current?
[18:59] <jcoxon> need to measure it, one sec
[19:02] <jcoxon> 3.7A
[19:02] <Laurenceb> how horrible I guess
[19:02] <Laurenceb> *not
[19:02] <jcoxon> according to my dying multimeter
[19:03] <jcoxon> its a seperate power supply
[19:03] <Laurenceb> the resistor cutdown takes about 500ma
[19:03] <jcoxon> on a relay
[19:03] <Laurenceb> ah
[19:03] <Laurenceb> voltage?
[19:03] <jcoxon> 5v
[19:03] <Laurenceb> not bad
[19:03] <Laurenceb> how long does it take to melt?
[19:04] <jcoxon> the line breaks after about 2 seconds
[19:04] <Laurenceb> ok
[19:04] <jcoxon> then it continues to melt the line untill it just doesn't exist
[19:04] <Laurenceb> similar to resistor cutter time wise
[19:04] <jcoxon> i've got my flight computer firing it for 10secs
[19:04] <Laurenceb> sounds sensible
[19:05] <jcoxon> transistor inbetween the avr and relay as well
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[19:49] <SpeedEvil> umm - why relay?
[19:49] <SpeedEvil> oh - for testing?
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[19:56] <Laurenceb> http://www.pro38.com/motor/K445-A.html
[19:56] <Laurenceb> wonder if you could scale down to <10Kg GLOW
[19:57] <Hiena> Ehehehe...I getting miss the good old FM pirating times. But seems lot of locals remembers, because i need airing only a few minutes trance music with my tuned signal generator to get "Is that you?" phone calls.
[19:57] <RocketBoy> Having built one of Laurenceb's resistor cutdowns recently I have to say i have been inpressed by the simplicity & reliability - i used some 4R7 resistors and 1.25mm braded nylon line - worked every time - even at 100K ft
[19:58] <Laurenceb> I actually avoided nylon
[19:58] <Laurenceb> due to the high melting point
[19:58] <RocketBoy> lat t
[19:58] <RocketBoy> last time I saw you use it it looked like nylon to me
[19:59] <Laurenceb> polyurethane or something
[19:59] <Laurenceb> I'm using solid core wire insulation now
[19:59] <RocketBoy> looked like kite twine
[19:59] <Laurenceb> up to where it meets the resistor
[19:59] <Laurenceb> then there was a ~10mm lenght of low melting point plastic
[20:00] <Laurenceb> RocketBoy: has anyone even built anything at EARS with thrust vector control?
[20:02] <RocketBoy> one one person as far as I know - gyrock
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[20:03] <Laurenceb> ah yeah that
[20:03] <Laurenceb> I was playing about with a n prize design
[20:03] <Laurenceb> thinking 2 stage, balloon launch
[20:03] <RocketBoy> http://www.ukrocketman.com/rocketry/gimbal.shtml
[20:04] <RocketBoy> thays in the UK - guys in the US have done it too
[20:04] <RocketBoy> thats
[20:04] Action: SpeedEvil ponders if a model heli dropping a concealed payload on the shuttle'd count.
[20:05] <RocketBoy> there have been a couple of activly stabilized designs in the UK - using fin trailing edges and cant fins
[20:06] <Laurenceb> I was thinking hydrogen peroxide with gymballed graphite nozzel for first stage
[20:06] <Laurenceb> - hydrogen peroxide and kerosene
[20:06] <Laurenceb> not sure if roll control would be needed
[20:07] <Hiena> RocketBoy, nice stuff.
[20:07] <Hiena> Any more detail about the used gyro?
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[20:07] <Laurenceb> handbuilt
[20:07] <Hiena> I means schematic, drawings, etc.
[20:07] <RocketBoy> the first gyroc versions used a homebrew gyro
[20:08] <RocketBoy> later versions used model helicopter gyros
[20:08] <RocketBoy> since it only ascends on low G - heli gyros are OK
[20:08] <Hiena> I see. Anyhow, i'll post it to a local UAV builders. They has serious conceptual problems. ;)
[20:09] <Laurenceb> interesting it has no roll control
[20:09] <RocketBoy> also see http://michael.sdf-eu.org/Gyroc/
[20:09] <Hiena> They always crying about, how hard to build/code a decent control loop.
[20:10] <Laurenceb> heh
[20:10] <Laurenceb> theres plently of code out there
[20:10] <Laurenceb> well algorythms anyway
[20:10] <SpeedEvil> Fuzzy logic is great.
[20:11] <Laurenceb> make it run fast is a bit harder
[20:11] <SpeedEvil> You just train it so that it knows that crashes are bad.
[20:11] <Laurenceb> well
[20:11] <Laurenceb> stuff like that at high level maybe
[20:12] Action: Laurenceb wonders what would case a rocket to spin up in the roll axis
[20:12] <Hiena> I know, and they know too. Yet, they doing insane mistakes. For example, the last time they fixed the pitot tube right to the wingtip. The static pressure intake was few millimeters from the leading edge, and the sensor was connected 1 meter long tubes to the sensor.
[20:13] <Hiena> Three mistake only for one sensor.
[20:13] <Laurenceb> lol
[20:14] <Laurenceb> 1) tube too long, 2) detects yaw rate 3) not measuring the true stagnation pressure ?
[20:14] <Hiena> Exactly.
[20:17] <Hiena> At the other case thes fixed a pressure based angle and slip sensor to the plane, and was surprised when it didn't work at low speed.
[20:17] <SpeedEvil> Hiena: ... I though that the length of tube was immaterial
[20:17] <RocketBoy> humm - I have a gyro videoclip in my collection - impressive
[20:18] <SpeedEvil> Why does length of tube matter?
[20:18] <Hiena> SpeedEvil, it's act as delay line.
[20:18] <SpeedEvil> Umm.
[20:18] <SpeedEvil> Not significantly aat the pressures involved I'd have thought
[20:18] <SpeedEvil> Unless you go _way_ too small on the guage
[20:20] <Hiena> Also, it's a thin walled silicone tubing, so it could makes a cute things.
[20:21] <SpeedEvil> For a 100Pa step, your tube needs to pressurise to 100Pa over ambient - involving a flow of .1% of the volume of the tube - for a 1m tube, that's a 1mm 'slug' of air.
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[20:23] <Laurenceb> RocketBoy: http://www.pro38.com/motor/K445-A.html
[20:24] <Laurenceb> do those come with a cardboard wrapper?
[20:25] <SpeedEvil> Laurenceb: Have you considered: http://rookery2.viary.com/storagev12/989000/989110_9383_625x1000.jpg
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[20:27] <Laurenceb> lol
[20:28] <Hiena> Ehhh...
[20:28] <Hiena> Ion powered penguins.
[20:28] <RocketBoy> pro38s have a plastic liner
[20:29] <Hiena> It would be interesting when the Orca destroyers arrives.
[20:29] <Laurenceb> RocketBoy: any idea how thick?
[20:29] <RocketBoy> sure - I'll measure one - hang on
[20:29] <Laurenceb> heh
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[20:30] <Laurenceb> awsome, any change you could measure the throat diameter as well?
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[20:35] <SpeedEvil> Laurenceb: Stage 1 - http://rookery2.viary.com/storagev12/989000/989030_2824_625x1000.jpg
[20:35] <Laurenceb> what the ....
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[20:38] <Laurenceb> RocketBoy: how long is the reload?
[20:40] <RocketBoy> depends on the motor
[20:40] <Laurenceb> http://www.pro38.com/motor/K445-A.html
[20:41] <Laurenceb> that lenght includes the case?
[20:41] <RocketBoy> its very aprox 34.1mm
[20:41] <Laurenceb> the throat?
[20:41] <RocketBoy> thats not a pro 38 - its a pro54
[20:42] <Laurenceb> right
[20:42] <RocketBoy> the K445
[20:42] <Laurenceb> ok
[20:42] <Laurenceb> so whats 34.1mm ?
[20:43] <RocketBoy> the pro38s
[20:43] <RocketBoy> the outer dia of the reloads
[20:43] <Laurenceb> ah
[20:43] <RocketBoy> (measure using some used reloads
[20:43] <RocketBoy> measured
[20:43] <Laurenceb> wow ok... so its called a 54mm motor ?
[20:44] <Laurenceb> but propellant is 34.1mm ?
[20:44] <RocketBoy> I'll have to measure a pro54 case later - but you can recon on similar redultion - so say 50mm
[20:44] <Laurenceb> thats good :P
[20:45] <Laurenceb> improves the dry mass a _lot_
[20:45] <Laurenceb> thanks
[20:46] <RocketBoy> well the propellent is actually smaller - its then loaded in a thin plastic liner - which then inserts in the aluminium casing
[20:46] <RocketBoy> the liner provies protection to the casing
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[20:46] <Laurenceb> ah right
[20:46] <Laurenceb> is there a casing on the propellant charge as well?
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[20:47] <RocketBoy> yes
[20:47] <RocketBoy> - aluminium casing for pressure
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[20:48] <Laurenceb> I ment over the reload
[20:48] <RocketBoy> the liner seals to the nozzel and combustion chanber end
[20:48] <Laurenceb> right
[20:49] <Laurenceb> whats the throat diameter approx?
[20:49] <RocketBoy> no the reload is amoniumperchlotate + aluminium pellats in a platic liner - the liner then inserts in the casing
[20:50] <RocketBoy> varies quite a lot depending on motor (size, long/short burn etc.)
[20:50] <Laurenceb> ok got you
[20:50] <Laurenceb> sorry
[20:52] <RocketBoy> http://pro38.com/products/pro54/pro54.php
[20:52] <Laurenceb> think I get it
[20:52] <RocketBoy> the reload in the liner is at the bottom of the picture
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[20:52] <Laurenceb> so my idea would be to mill off most of the liner from the reload
[20:52] <Laurenceb> place it inside CF tube
[20:52] <RocketBoy> the casings are around it
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[20:53] <Laurenceb> then pour castable ceramic around it
[20:53] <Laurenceb> - same as the martlet plan
[20:53] <RocketBoy> sure if the CF epoxy holds up
[20:53] <Laurenceb> yeah knowledge of chamber pressure is vital
[20:54] <Laurenceb> cesarroni mention 2500psi
[20:55] <RocketBoy> yeah - I should think that would be relativly easy to back calcualte from the thrust curve
[20:56] <RocketBoy> see - http://pro38.com/pdfs/Pro54_instructions.pdf - shows it all
[20:57] <RocketBoy> is CF + ceramic much lighter than ali
[20:58] <Laurenceb> about an order of magnitude
[20:58] <RocketBoy> the MARS guys made a CF hybrid motor i think
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[21:00] <RocketBoy> I'd be going for the 54mm L730 rather than the K445
[21:00] <Laurenceb> hmm I think it'll take a 75mm motor to work
[21:01] <RocketBoy> in that case I'd look at the aerotec motors
[21:02] <RocketBoy> I think the bigest 75mm
[21:03] <Laurenceb> arg I messed up
[21:03] <Laurenceb> burnout weight is total weight at burnout?
[21:03] <RocketBoy> yes
[21:03] <RocketBoy> includiing casing aand remainder of reload
[21:04] <RocketBoy> should be inital weight less pellate weight
[21:04] <Laurenceb> right start again
[21:05] <RocketBoy> initial weight = loaded weight
[21:09] <RocketBoy> http://www.aerotech-rocketry.com/customersite/resource_library/Catalogs_Flyers_Data_Sheets/09-10_aerotech_catalog.pdf
[21:10] <RocketBoy> mmmm M1850 - 7500 Ns
[21:10] <RocketBoy> 75mm
[21:11] <Laurenceb> think I can get delta v of 4.9Km/sec with a K445-A
[21:12] <Laurenceb> and 20 gram payload
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[21:12] <RocketBoy> see digagram on bottom of page 5 to see how it all fits together
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[21:15] <RocketBoy> I doubt the K445 is any better than any other Cesaroni "classic" reload
[21:15] <Laurenceb> hmm throat is big
[21:15] <RocketBoy> its all down to ISP
[21:16] <Laurenceb> yeah they have done tests
[21:16] <RocketBoy> are the "blue thunder"/"Vmax" reloads any better?
[21:16] <Laurenceb> some have considerably better ISP - looks to be down to burn uniformity
[21:17] <Laurenceb> and motor size - bigger is better ISP
[21:17] <Laurenceb> from why?
[21:18] <RocketBoy> well sure - for bigger motors the mass faraction of the casing will be marginally less
[21:18] <Laurenceb> *who
[21:18] <Laurenceb> they measured total ISP/delta mass
[21:18] <RocketBoy> Vmax is Cesaroni
[21:18] <Laurenceb> *total Ns
[21:18] <Laurenceb> cant see it on the website
[21:19] <RocketBoy> Bule thunder is Aerotech
[21:19] <RocketBoy> there is cesaronit "blue streak" - just different propellant combinations
[21:22] <Laurenceb> ISP seems to hover about 210 maximum
[21:22] <Laurenceb> but with a better nozzle in vacuum
[21:22] <Laurenceb> problem is the nozzle gets wider than then propellant tube
[21:24] <Laurenceb> http://www.pro38.com/motor/K445-A.html
[21:27] <RocketBoy> sure - in the vacuum of space - the ideal exit pressure is 0
[21:28] <RocketBoy> - so quite big ;-)
[21:28] <Laurenceb> the accel is rather high
[21:28] <Laurenceb> >100G :P
[21:28] <Laurenceb> probably wants something slower burning
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[21:30] <Laurenceb> http://www.pro38.com/motor/J210-16A.html surely not
[21:30] <RocketBoy> yeah - there are stories of the propellant deforming under that sort of acceleration - and blocking the exit (boom) - i don't know how true they are
[21:31] <Laurenceb> hmm I get 191 from those numbers
[21:33] <RocketBoy> BBL
[21:52] <Laurenceb> some of the aerotech motors are longer burning
[21:52] <Laurenceb> might get it down to 100G
[21:58] <Laurenceb> what can quartz oscillators take?
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[22:05] <SpeedEvil> up to several tens of KG
[22:06] <Laurenceb> hmm I guess the really small SMD ones will be ok
[22:06] <SpeedEvil> possibly
[22:06] <Laurenceb> I broke a radiometrix dropping it from a hab into a concrete car park
[22:06] <SpeedEvil> qualify them in your centrifuge.
[22:06] <Laurenceb> but that used a very large crystal
[22:06] <SpeedEvil> (Washing machine)
[22:06] <Laurenceb> heh
[22:07] <Laurenceb> well youd do some statck stage 2 firings from the launch tube
[22:07] <Laurenceb> into... a wall maybe :P
[22:09] <SpeedEvil> my washing machine does 700G
[22:09] <Laurenceb> http://www.pro38.com/motor/K445-A.html <- gives about 310G at burnout
[22:10] <Laurenceb> the aerotech motors are below 100
[22:11] <Laurenceb> I think a Ti chipcon based transceiver should survive
[22:13] <Laurenceb> so you can get delta V of around 5Km/sec for the spun solid with a decent nozzle
[22:13] <Laurenceb> so you need about 4 for the first stage, giving <10Kg glow
[22:14] <Laurenceb> should be liftable with 5 1000gram latex balloons
[22:14] <SpeedEvil> I doubt the motor willl stick to thecase at 100G
[22:15] <Laurenceb> they can get similar G with a normal rocket
[22:18] <Laurenceb> with some of the shorter burn time motors
[22:18] <Laurenceb> also they use weaker propellant geometeries
[22:19] <Laurenceb> you could add some small vanes to spin up the rocket as it flew
[22:21] <Laurenceb> 50Hz or so would help a lot
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[22:33] <Laurenceb> http://www.youtube.com/watch?v=uAt2xD1L8dw
[22:34] <SpeedEvil> you mean to spin up to 3000RPM?
[22:35] <Laurenceb> yes
[22:35] <Laurenceb> or rather use the launch tube to spin at ~200RPM
[22:35] <Laurenceb> then some vanes that spin it up further
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[22:38] <SpeedEvil> I suppose you could have a centrifugal clutch thing to pul the vanes out when it's at speed
[22:38] <SpeedEvil> or even just a spring
[22:39] <Laurenceb> you could make a test structure
[22:39] <Laurenceb> to see if it is actually a problem
[22:41] <SpeedEvil> yeah
[22:41] <SpeedEvil> This may void your washing machine warranty. :)
[22:42] <Laurenceb> or a steel arm
[22:42] <Laurenceb> fix the engine on and have a jet deflector to make it spin
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[22:50] <RocketBoy> humm - a rotating tube launched finless rocket - there is an idea for EARS Sunday
[22:50] <Laurenceb> CF tune with spring loaded blades to bite in and give some spin
[22:51] <Laurenceb> *tube
[22:51] <RocketBoy> I was thinking of a motor
[22:52] <RocketBoy> (DC)
[22:52] <RocketBoy> and some bushes to make contact
[22:53] <RocketBoy> simples
[22:56] <SpeedEvil> Laurenceb: http://en.wikipedia.com/wiki/gyroget
[23:03] <RocketBoy> nights
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[00:00] --- Thu Jul 9 2009