highaltitude.log.20090707

[00:02] <Laurenceb> http://www.dunnspace.com/alternate_ssto_propellants.htm
[00:03] <SpeedEvil> Cream-cheese/liquid-ozone!
[00:04] Action: Laurenceb wants some propargyl alcohol
[00:04] <Laurenceb> interesting they use crazy chamber pressures there
[00:05] <Laurenceb> your limited with H2O2 decomposition, but should be able to go over 3.4MPa by a long way
[00:05] <SpeedEvil> crazy low?
[00:05] <Laurenceb> you can buy it for electroplating nickle apparently
[00:05] <Laurenceb> high
[00:05] <Laurenceb> 20MPa
[00:06] <Laurenceb> interesting that H2O2 is so close to LOz
[00:06] <Laurenceb> LOx
[00:07] <SpeedEvil> Maybe they need it to decompose some of the less volatile species they have
[00:07] <SpeedEvil> residency time and reaction rate rise with increasing temp
[00:07] <SpeedEvil> increasing pressure
[00:08] Action: SpeedEvil is having net problems again
[00:08] <Laurenceb> I guess if you have a pump its not too much of a panalty
[00:09] <Laurenceb> with CF overwrapped 2.5KN engine the weight penalty is about 150 grams going from 3.4 to 20MPa
[00:09] <Laurenceb> your limited by machining accuracy and fuel viscousity
[00:09] <Laurenceb> and the liner is most of the weight
[00:12] <Laurenceb> your limited by H2O2 pumping - as the water vapour will turn superfluid at high pressure
[00:12] <SpeedEvil> huh?
[00:12] <SpeedEvil> oh
[00:12] <SpeedEvil> you're talking catalytic pimps.
[00:13] <Laurenceb> yeah
[00:13] <Laurenceb> 22MPa
[00:14] <Laurenceb> so a sensible upper chamber pressure might be 15MPa
[00:14] <SpeedEvil> Catalytic pumps have disadvantages.
[00:15] <SpeedEvil> But anyway - pumping energy at that gets quite high nomatter ho you do it
[00:15] <Laurenceb> yeah, you need to count that against ISP
[00:15] <SpeedEvil> Turbopumps work well at silly scales of course
[00:18] <Laurenceb> hmm yeah your talking about a ~3% decrease in ISP
[00:19] <Laurenceb> theres going to be a max performance point
[00:19] <Laurenceb> I'm guessing somewhere around 10MPa or so
[00:20] <Laurenceb> using something like 2.5% of your peroxide for pumping
[00:20] Action: SpeedEvil tries to remember other reasons.
[00:20] <SpeedEvil> I think film cooling might work better at high pressures
[00:21] <SpeedEvil> but I don't really remember.
[00:22] <Laurenceb> well a 1Kg nanosat to LEO SSTO looks possible for sure
[00:22] <Laurenceb> with 25Km balloon lauch
[00:23] <Laurenceb> and the engine would take some serious work
[00:23] Action: SpeedEvil wonders how you make a 25km balloon.
[00:23] <Laurenceb> balloon to
[00:23] <SpeedEvil> yeah.
[00:23] <Laurenceb> maybe graphite seals in the pump
[00:24] Action: SpeedEvil is at the point of free associating/falling asleep/mowing the lawn as I'm a bit hot.
[00:24] <Laurenceb> lol
[00:24] <Laurenceb> do you have neighbours?
[00:24] <Laurenceb> - or sping metal seals similar to piston rings
[00:25] <SpeedEvil> yes - but it's an electric lawnmower.
[00:25] Action: Laurenceb once tried to design a self powered lawnmower
[00:26] <Laurenceb> - grass goes to methane digester
[00:26] <SpeedEvil> It's called a sheep.
[00:26] <Laurenceb> unfortunately grass isnt too good in a methane digester
[00:27] <Laurenceb> I got one working with cabbage
[00:27] <Laurenceb> and running a bunsen burner once
[00:28] <SpeedEvil> I want a mini-digger type thing.
[00:28] <SpeedEvil> With lots of attachments
[00:28] <SpeedEvil> I mean an electric one
[00:28] <SpeedEvil> maybe 25kg basic weight
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[01:13] <edmoore> hi fergusnoble
[01:13] <fergusnoble> good evening
[01:13] <edmoore> all well?
[01:14] <fergusnoble> yup, spent the afternoon working on nosecone separation schemes
[01:14] <fergusnoble> everthing good your end?
[01:15] <edmoore> yep, spent the day with Tess
[01:15] <edmoore> She's off to Asia till end of august
[01:15] <edmoore> going back to cam tomorrow morning. May stop off en route to pick up an 817, PSU, SWR meter and a pair of shorter yagis
[01:15] <fergusnoble> cool
[01:16] <edmoore> can you think of anything else to add to the list?
[01:16] <fergusnoble> are you going to see alan soon?
[01:16] <fergusnoble> could be good
[01:16] <edmoore> alan r?
[01:16] <fergusnoble> technician
[01:16] <fergusnoble> does the 817 not have batts?
[01:17] <edmoore> psu is for me
[01:17] <edmoore> well, may give that high current one to CUSF
[01:17] <edmoore> and having something smaller and weaker for the icom
[01:18] <fergusnoble> ok
[01:18] <edmoore> re: alan, haven't booked an appointment. will probably discuss with you tomorrow if you're around
[01:18] <fergusnoble> ok, cool
[01:19] <edmoore> how does skype work with you? you weren't online today, unless I'm missing something
[01:19] <fergusnoble> i dont know much about it i think we just have to grab him when hes free and ask him what the deal is
[01:19] <fergusnoble> skype is good
[01:19] <edmoore> that's exactly what one does with him, yep
[01:20] <fergusnoble> wasnt online today no, but will be tomorrow
[01:20] <edmoore> ok
[01:22] <edmoore> can tell me what you've come up with on nose separation too.
[01:23] <edmoore> Sensors: Matt thinks it's a cool idea, is at a conference today and tomorrow but will send his study on wed and reckons that a test on model drop of full scale drop pressure hardware may work.
[01:23] <edmoore> and may be free for us
[01:24] <fergusnoble> awesome
[01:24] <fergusnoble> not got anything final on nosecone sep really
[01:24] <edmoore> it's a toughie
[01:25] <edmoore> maybe best left for a coffee and skype 2morrow
[01:25] <fergusnoble> some good ideas
[01:25] <edmoore> online whiteboard?
[01:25] <fergusnoble> exactly
[01:25] <fergusnoble> yeah, we can work something out
[01:25] <fergusnoble> maybe just napkins and webcams
[01:25] <edmoore> cool
[01:26] <edmoore> the time I get back to cam depends on whether or not I decide to get radio (after rushour) or not (before rushour)
[01:27] <edmoore> although actually getting up at 5am doesn't really appeal to me much. So praps it'll be after rushour come what may. Can't image you'd be too upset not to have me at 9am though :)
[01:27] <fergusnoble> yeah, not planning on an early start
[01:27] <fergusnoble> :)
[01:28] <edmoore> ok. will stop off at ML&S then.
[01:29] <fergusnoble> ok, cool
[01:29] <edmoore> this'd do us. http://www.flickr.com/photos/barry10a/2752956141/in/set-72157606664072445/
[01:29] <fergusnoble> wonder if they do tripod yagi mounts
[01:29] <edmoore> ill ask
[01:30] <edmoore> though the old test tube clamp has its charm
[01:30] <fergusnoble> probably a bit low gain for our purposes
[01:30] <edmoore> maybe a 10m dish?
[01:30] <SpeedEvil> I saw 2.4m (IIRC) sectional dishes on ebay
[01:30] <fergusnoble> http://www.users.globalnet.co.uk/~arcus/cara/
[01:30] <fergusnoble> on the right
[01:31] <edmoore> nice
[01:32] <edmoore> http://www.nitehawk.com/rasmit/NLD/eme0812.pdf
[01:32] <edmoore> page 7
[01:32] <edmoore> that might be a bit more gain
[01:33] <Laurenceb> this for rocket comms?
[01:33] <fergusnoble> lol
[01:33] <edmoore> nah, just for normal balloons
[01:33] <edmoore> we think a 24 x 22-el yagi stack is really the bare minimum we need
[01:34] <Laurenceb> heh
[01:34] <Laurenceb> your crazy
[01:34] <Laurenceb> IMO the Ti trasceiver ICs are the way to go
[01:34] <Laurenceb> pity the UM12 is a silly implimentation
[01:34] <edmoore> oh? you never mentioned.
[01:34] <Laurenceb> heh
[01:35] <fergusnoble> Laurenceb: the CC1111/0?
[01:35] <Laurenceb> erm... cant remember offhand
[01:35] <Laurenceb> but 868 is probably best
[01:35] <Laurenceb> as you can go for 500mw
[01:36] <Laurenceb> lookup the ti "chipcon" series
[01:36] <fergusnoble> yup thatys it
[01:36] <Laurenceb> you might want an external power amp for 500mw
[01:36] <fergusnoble> i designed the badgercub around it
[01:36] <fergusnoble> only 10mw through
[01:36] <Laurenceb> nice
[01:37] <Laurenceb> yeah the UM12 implimentation sucks
[01:37] <Laurenceb> it cant even buffer internally
[01:38] <Laurenceb> and if theres a single error detected it stops and switches to reverse the direction of data flow
[01:38] <Laurenceb> which gives a big performance penalty
[01:39] <fergusnoble> ok, ill keep that in mind
[01:39] <fergusnoble> i was just going to kludge it to send rtty for now
[01:39] <Laurenceb> yeah nice plan
[01:39] <Laurenceb> but the performance looks good
[01:39] <Laurenceb> and my tests with the UM12 seem to verify that if you account for the lame firmware
[01:40] <fergusnoble> ok, have you been playing with hardware?
[01:40] <Laurenceb> got ~500m range but there were 3 6 story steel and concrete buildings in the line of sight
[01:40] <fergusnoble> cool
[01:40] <fergusnoble> what programmer did you get?
[01:41] <Laurenceb> and I used the stock antennas
[01:41] <Laurenceb> ?
[01:41] <Laurenceb> oh that - its an issue with avrdude
[01:41] <fergusnoble> huh? you can program it with an avrdude?
[01:42] <Laurenceb> I dont follow
[01:42] <Laurenceb> the UM12 is a "plug and play" transceiver module
[01:42] <fergusnoble> oh is that the usb donghle?
[01:42] <Laurenceb> theres a uC onboard to talk to the chipcon
[01:42] <Laurenceb> its a pcb about 25 by 45mm
[01:43] <fergusnoble> oh right, your not using the chipcon SoC?
[01:43] <Laurenceb> the UM12 uses a chipcon
[01:43] <fergusnoble> the badgercub uses the CC1111 which has an onboard 8051
[01:44] <fergusnoble> they also moake ones without an mcu
[01:44] <Laurenceb> yeah just looked at the UM12 and its got a CC1111 I think
[01:44] <Laurenceb> hmm
[01:44] <fergusnoble> ok, but your not programming the onboard 8051 yourself
[01:44] <Laurenceb> no
[01:44] <fergusnoble> ok
[01:44] <Laurenceb> actually no... I cant see under the sheilding
[01:45] <Laurenceb> its probably not
[01:45] <Laurenceb> as there a tqfp AVR on there as well
[01:45] <fergusnoble> i was wondering where you got a programmer for it so dont worry
[01:45] <Laurenceb> so its probably not one with a core built in
[01:45] <fergusnoble> the dev kit is expensive but they sell a stand alone programmer that is cheap but i cant find anywhere that sells it
[01:45] <Laurenceb> but its got sheilding over the top
[01:45] <Laurenceb> right
[01:46] <Laurenceb> so theres flash on the die as well?
[01:46] <fergusnoble> yup, its all completely integrated
[01:46] <Laurenceb> basically uC + transciever
[01:46] <Laurenceb> nice
[01:46] <fergusnoble> its a bit of a cruddy mcu
[01:46] <Laurenceb> uart?
[01:46] <fergusnoble> yeah
[01:46] <Laurenceb> perfect
[01:46] <fergusnoble> and spi, i2c, adc etc
[01:46] <Laurenceb> does it require an external RF switch?
[01:46] <Laurenceb> - some of them do
[01:47] <fergusnoble> the badgercub is that plud a venus gps plus a sarantel antenna
[01:47] <Laurenceb> heh perfect
[01:47] <fergusnoble> no, it requires a balun to connect to a single ended ant
[01:47] <fergusnoble> but the reference design gives an example so i just copied that
[01:47] <Laurenceb> so it has balanced RF out?
[01:47] <fergusnoble> its just a couple of passives
[01:47] <fergusnoble> yeah
[01:48] <Laurenceb> and Rf in is sperate?
[01:48] <fergusnoble> no, the rf in shares the same antenna
[01:48] <Laurenceb> ah ok
[01:48] <fergusnoble> (and chip pins)
[01:48] <Laurenceb> some of them have seperate in out
[01:48] <fergusnoble> ok
[01:48] <Laurenceb> which would be good for 868 as you could stick in an external 500mw amp
[01:49] <fergusnoble> this one disables its tx stuff when you try to rx
[01:49] <Laurenceb> yeah
[01:49] <Laurenceb> thats where the UM12 firmware screws up
[01:49] <Laurenceb> it doesnt handle Tx/Rx transitions properly
[01:49] <Laurenceb> and doesnt buffer data
[01:50] <Laurenceb> also the pcb design is daft - two crystals for a start
[01:50] <Laurenceb> they should run the avr off one crystal and use a clkout to drive the chipcon transceiver
[01:51] <Laurenceb> but it has rs485 support which is groovy
[01:51] <fergusnoble> hehe
[01:52] <Laurenceb> how dig is badgercub and what does it have broken out?
[01:52] <Laurenceb> *big
[01:52] <Laurenceb> arg
[01:52] <Laurenceb> I was thinking of adding an analogue devices IMU
[01:53] <fergusnoble> its about 3x6cm
[01:53] <edmoore> Laurenceb: one of the yummy all-in-one 6DOF units?
[01:53] <Laurenceb> no
[01:54] <Laurenceb> 9 DOF :P
[01:54] <fergusnoble> and i can break out some stuff if you want, not sent off the board yet
[01:54] <Laurenceb> Id need to test a venus receiver with a simulator really
[01:54] <edmoore> mag?
[01:54] <Laurenceb> yep
[01:54] <Laurenceb> $400
[01:55] <edmoore> got a link to hand?
[01:55] <Laurenceb> just a sec
[01:56] <Laurenceb> http://www.analog.com/en/mems/imu/adis16400/products/product.html
[01:56] <Laurenceb> they changed the range and pricing...
[01:57] <Laurenceb> http://www.analog.com/en/mems/imu/adis16405/products/product.html
[01:57] <edmoore> I like the look of that.
[01:57] <Laurenceb> thats probably what would be ideal ^
[01:58] <Laurenceb> 16 grams iirc
[01:58] <Laurenceb> does your fancy ARM compiler have a good math lib?
[01:58] <edmoore> yep
[01:58] Action: Laurenceb is thinking all floating point code
[01:59] <edmoore> http://www.rowley.co.uk/news.htm#CrossWorks%20for%20ARM%201.7%20Released
[01:59] <Laurenceb> what compiler are you using ?
[01:59] <Laurenceb> ah
[01:59] <edmoore> "New highly-optimised GPL-free floating point math library."
[01:59] <edmoore> wooooo
[02:00] <edmoore> it even tells you how optimised it is
[02:00] <edmoore> "highly"
[02:00] <Laurenceb> heh
[02:00] Action: Laurenceb demands benchmarks
[02:01] <Laurenceb> ooh only $150
[02:01] <Laurenceb> much as I refuse to pay for software... its tempting
[02:03] <Laurenceb> does badger cub have JTAG?
[02:03] <edmoore> well it's based on an 8051
[02:03] <edmoore> as fergusnoble just explained
[02:03] <Laurenceb> huh
[02:04] <Laurenceb> I thought that was inside the chipcon transceiver...
[02:04] <edmoore> and very few 8051s, as far as i know, have jtag
[02:04] <edmoore> yes it is
[02:04] <fergusnoble> Laurenceb: its some Ti 2-wire prog i/f
[02:04] <Laurenceb> oh - your using the chipcon as the uC
[02:04] <Laurenceb> right
[02:04] <edmoore> cub is just a simple smaller tracker
[02:04] <edmoore> it's not the new badger
[02:04] <Laurenceb> I see
[02:05] <Laurenceb> ok, I'm looking to build something with that AD IMU and an arm
[02:05] <akawaka> regular math lib is slow?
[02:06] <edmoore> i think it's not so architecture optimised
[02:06] <Laurenceb> yeah
[02:06] <edmoore> so for example crossworks, which we use, also gives an option to do single float ops
[02:06] <Laurenceb> the red hat lib looks to be grabbed from linux
[02:06] <edmoore> (the IEEE standard being to work with doubles)
[02:07] <Laurenceb> hmm if the redhat lib uses doubles its really screwed
[02:07] <akawaka> yeah
[02:07] <edmoore> actually you might want to check me on that, but certainly things like trig and logs/exps are all specified to be double precision
[02:07] <Laurenceb> ok
[02:08] <akawaka> back in the ps2 days the gcc compiler would default to doubles, so you had to make sure you suffixed every floating point constant with 'f'
[02:08] <edmoore> plain old mults and adds might not be
[02:08] <Laurenceb> I'm looking at of order 2KFLOPs for each attitude filter run
[02:08] <akawaka> sin( foo ) is double
[02:08] <akawaka> sinf( foo ) is single
[02:09] <akawaka> but i could see a software lib using a higher precision internally
[02:09] <edmoore> yep, crossworks adopts same nomenclature
[02:09] <akawaka> since the hardware usually does
[02:38] <akawaka> Laurenceb: 2kflops on which processor?
[02:39] <Laurenceb> ?
[02:39] <Laurenceb> its determined by the equations
[02:40] <akawaka> i mean you want to reach 2kflops on which processor?
[02:40] <Laurenceb> arm
[02:41] <Laurenceb> no
[02:41] <Laurenceb> 2K floating point operations per iteration
[02:41] <Laurenceb> so 1K interations per sec would be 2MFLOPS
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[03:17] Nick change: KingJ -> kingj
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[08:41] <Laurenceb> sup my homie
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[10:39] <gordonjcp> edmoore-induced oscillations
[10:39] <edmoore> oh sorry
[10:39] <edmoore> it's a slightly bitty morning
[10:39] <edmoore> want to go back to cam, waiting for ML&S to get back to me so I can pick some stuff up on the way
[10:41] Action: Laurenceb discovered spacefellowship
[10:41] <Laurenceb> I see theres a CU spaceflight section
[10:45] Nick change: kingj -> KingJ
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[11:23] Action: SpeedEvil discovers get_iplayer.
[11:27] <Laurenceb> sudo apt-get install iplayer
[11:29] <SpeedEvil> perl script to rip the streams
[11:31] <Laurenceb> ah
[11:31] <Laurenceb> can you get round the timelimit?
[11:31] <Laurenceb> or are they removed from the server?
[11:33] <Laurenceb> stupid bbc are clearly so obsessed with apple
[11:33] <Laurenceb> freaking ifans
[11:33] <SpeedEvil> It downloads the file
[11:34] <SpeedEvil> I'm currently downloading some high quality streams from Wimbeldon.
[11:34] Action: SpeedEvil isn't really interested in tennis.
[11:35] Action: Laurenceb thinks he konws what interestes speedevil
[11:35] <Laurenceb> you discust me
[11:36] <Laurenceb> :P
[11:47] <Laurenceb> btw I came up with an idea for ignition with a regen engine
[11:47] <Laurenceb> preload the engine with catalyst containing propellant
[11:47] <SpeedEvil> My idea along that line was a little high-pressure tank and solenoid
[11:47] <Laurenceb> then when it starts that'll be forced out first, causing ijnition
[11:47] <Laurenceb> yeah
[11:48] <Laurenceb> thats useful if you want restartable
[11:48] <SpeedEvil> shut off the engine, inject xml of catalyst into the fuel line
[11:48] <Laurenceb> but if you can live without
[11:48] <Laurenceb> yeah
[11:48] <SpeedEvil> chunks of potassium permanganate in the chamber have apparanytly been used
[11:48] <Laurenceb> also if you could use a common nitrogen system for the tank and accumulators
[11:48] <Laurenceb> but it all adds complication
[11:49] <Laurenceb> liquid cat additive apparently works very well
[11:49] Action: Laurenceb sticks a cat in a blender
[11:49] <SpeedEvil> tabby?
[11:49] <Laurenceb> lol
[11:49] <SpeedEvil> hemoglobin is a catalyst.
[11:50] <Laurenceb> heh might actually work
[11:50] <Laurenceb> emo power
[11:50] <SpeedEvil> though as it's enzyme based, it breaks down at a % or so, and 40C
[11:51] <Laurenceb> the big problem with SSTO is high accel at burnout
[11:52] <SpeedEvil> throw away big engine, light little one?
[11:52] <SpeedEvil> though that raises almost as many issues
[11:53] <Laurenceb> yeah
[11:53] <Laurenceb> may as well go for two stage if you want to do that
[11:53] <Laurenceb> and you start to suffer from fixed wieght overheads
[11:53] <Laurenceb> but two stage is obviiously easier
[11:54] <Laurenceb> once you get to three or four stages it starts to get suboptimal
[11:54] <Laurenceb> for <100Kg GLOW stuff
[11:54] <Laurenceb> unless you go for spin stabilised solids or something with minimal fixed mass overheads
[11:55] <Laurenceb> also theres all the extra design and testing work
[11:56] <SpeedEvil> twelve stages sugar/KNO3
[11:56] <Laurenceb> lmao
[11:57] <Laurenceb> that stuff is horrible
[11:57] <SpeedEvil> why?
[11:57] <SpeedEvil> (other than ISP)
[11:57] <Laurenceb> poor performance, dangerous
[11:57] <Laurenceb> hard to cast well
[11:57] <SpeedEvil> seen the richard nakka site?
[11:57] <Laurenceb> yes
[11:58] <Laurenceb> but do you really want to be mucking about with that stuff
[11:58] <Laurenceb> easy way to blow yourself up
[11:59] <Laurenceb> annoying thing with propargyl alcohol is heat capacity
[11:59] <SpeedEvil> I came to the conclusion that - in the UK - trying to make solids is a bad idea legally
[11:59] <Laurenceb> looks like it can absorb max 1.5% of engine energy
[11:59] <Laurenceb> yeah that true
[12:00] <Laurenceb> *too
[12:01] <Laurenceb> I'm not sure whats sensible for energy fraction absorbed by the coolant
[12:01] <SpeedEvil> hmm
[12:01] <Laurenceb> but 1.5% seems too low
[12:02] <SpeedEvil> consider how much goes out without touching the walls though
[12:03] <Laurenceb> yeah I need to do a full analysis
[12:04] <Laurenceb> you could always switch to methanol or something
[12:04] <Laurenceb> with minimal panalty
[12:04] <Laurenceb> bbl
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[12:35] <Laurenceb> back
[12:36] <SpeedEvil> why propargyl?
[12:38] <Laurenceb> higher density and isp
[12:39] <SpeedEvil> ah
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[13:26] <Laurenceb> hmm that sugar shot to space site is interesting
[13:26] <Laurenceb> but its just 100Km
[13:26] <Laurenceb> they could just use martlet
[13:28] <SpeedEvil> honey/H2O2
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[13:30] <Laurenceb> lol
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[13:41] <Laurenceb> hmm a 50m side lenght tetroon would lift a 100kg rocket to 32Km
[13:48] <Laurenceb> a proper balloon shape uses about 30% less polythene
[13:49] Action: SpeedEvil wonders what the roll of polythene in the attic is.
[13:49] <SpeedEvil> It's about 20kg - but I'm unsure how thick
[13:50] <Laurenceb> from B&Q?
[13:50] <SpeedEvil> no
[13:51] <SpeedEvil> local ex-plastics factory
[13:52] <Laurenceb> you can cut a small section and weigh
[13:52] <Laurenceb> B&Q sell 9.5um or something IIRC
[14:04] <SpeedEvil> easier to just fold 7 times and measure*128
[14:06] <Laurenceb> http://garvspace.com/NLV.htm
[14:06] Action: Laurenceb isnt convinced
[14:09] <Laurenceb> although it looks like the payload mass fraction is very low
[14:09] <Laurenceb> that things got to weight 10 ton
[14:11] <Laurenceb> giving 0.1%
[14:15] <Laurenceb> http://garvspace.com/index.html <- that looks like the same sort of scale I'm thinking of
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[14:29] Nick change: Laurenceb -> edmoore
[14:29] <edmoore> hi
[14:29] Nick change: edmoore -> Laurenceb
[14:30] <Laurenceb> he needs to register his nick :P
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[14:51] <natrium42> .
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[15:34] <natrium42> edmoore?
[15:34] <edmoore> hi
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[15:36] <natrium42> yo
[15:36] <natrium42> sup?
[15:37] <edmoore> not much, just setting up some stuff in this room I'm gonna work in. also setting up our new yeasu 817.
[15:37] <edmoore> u?
[15:38] <natrium42> i am on vacation in sicily
[15:38] <edmoore> oh nice!
[15:38] <natrium42> just doing business stuff atm :S
[15:38] <edmoore> doing business in sicily is dangerous
[15:38] <natrium42> do you have summer off too?
[15:39] <edmoore> not really, am working in cambridge for most of it
[15:39] <natrium42> ah
[15:41] <natrium42> do you know about ballast halo plans?
[15:41] <edmoore> nope
[15:41] <edmoore> Laurenceb might
[15:41] <edmoore> or fergusnoble
[15:42] <edmoore> I've been a bit out of the loop this last week
[15:42] Action: natrium42 pokes Laurenceb and fergusnoble
[15:42] <fergusnoble> hello
[15:42] <natrium42> othello fergusnoble
[15:43] <fergusnoble> checkers natrium42
[15:43] <natrium42> all well?
[15:43] <fergusnoble> yup, pretty good
[15:43] <SpeedEvil> np: Beyonce - Halo.
[15:43] <natrium42> good good
[15:44] <natrium42> lol
[15:44] <natrium42> hi SpeedEvil
[15:44] <fergusnoble> hows things with you?
[15:44] <Laurenceb> hello
[15:44] <Laurenceb> sorry afk
[15:44] <Laurenceb> what you pestering me for?
[15:44] <natrium42> pretty good, getting sunburned in italy
[15:44] <natrium42> Laurenceb: ballast halo
[15:44] <Laurenceb> cool, stopping by in UK?
[15:45] <natrium42> no plans, sorry
[15:45] <Laurenceb> I think jcoxons plan was to stick a bung in the bottom
[15:45] <Laurenceb> with a small hole drilled in
[15:45] <Laurenceb> so the balloon follows some sort of parabolic flight
[15:45] <edmoore> oh, I have heard about this one, yes
[15:46] <edmoore> on saturday
[15:46] <edmoore> aiming to catch sunset and float for a while
[15:46] <Laurenceb> its launching saturday?
[15:46] <natrium42> cool
[15:46] <edmoore> 1/16th (yay imperial) hole in a bung in the neck of the balloon
[15:46] <edmoore> yes
[15:46] <natrium42> perhaps i will drop by
[15:46] <edmoore> steve might launch this weekend too
[15:46] <Laurenceb> has he built the bung?
[15:47] <edmoore> I don't know - his last exam is tomorrow
[15:47] <Laurenceb> oh he prob nicked it from a chem lab :P
[15:47] <edmoore> not an actual bung
[15:47] <edmoore> brb need to skype
[15:48] <natrium42> alexeikarpenko
[15:48] <natrium42> wait, or was it natrium42
[15:48] <natrium42> i always forget my skype name
[15:48] <edmoore> not you!
[15:48] <natrium42> :(
[15:48] <edmoore> boss/ish/former
[15:49] <edmoore> sorry
[15:49] <natrium42> :~(
[15:56] <_kc0wys> hey all
[15:57] <_kc0wys> just letting you all know i'm launching on thursday July 9 at 10AM CDT
[15:57] <natrium42> ooh
[15:57] <natrium42> nice
[15:57] <natrium42> what's the payload?
[15:58] <_kc0wys> avr mega16, 1200 bps radio modem link, live 2-watt video transmitter, 3 video cameras, 1 still digital camera, onboard video record
[15:58] <natrium42> whoa
[15:59] <natrium42> so live video?
[15:59] <SpeedEvil> Good luck!
[15:59] <natrium42> you should ustream it
[15:59] <Laurenceb> justin.tv it
[15:59] <Laurenceb> stickam it
[16:00] <_kc0wys> i'm not sure if i'll be able to get internet where i'm launching
[16:00] <natrium42> Laurenceb it
[16:00] <_kc0wys> but i'll try to figure something out
[16:01] <natrium42> :)
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[16:39] <rjharrison> hi fergusnoble
[16:40] <fergusnoble> rjharrison: hiya
[16:40] <rjharrison> fergusnoble anything on the cusf front atm
[16:40] <rjharrison> Do you still need to construct badger junior
[16:40] <fergusnoble> in terms of launches?
[16:40] <rjharrison> Yep
[16:40] <fergusnoble> i expect it to be a few weeks
[16:41] <fergusnoble> need to get badgercub built and bench tested first
[16:41] <fergusnoble> our next flight will be to test that
[16:41] <fergusnoble> hopefully with uplink :)
[16:41] <rjharrison> Yep have you sent the prototype off yet?
[16:41] <rjharrison> Uplink cool on 187?
[16:42] <rjharrison> I'm on with that too
[16:42] <rjharrison> unfortunatly steve and I lost our test payload
[16:42] <fergusnoble> no, the design is ready to go but have got caught up in mechanical design for the drop vehicle
[16:43] <fergusnoble> uplink on 434 probs
[16:43] <rjharrison> Ooh
[16:43] <rjharrison> FM
[16:43] <rjharrison> USB?
[16:43] <fergusnoble> not sure yet, need to fiddle with this TI radio chip
[16:43] <rjharrison> Humm
[16:44] <rjharrison> Let me know how you get on
[16:44] <fergusnoble> i think i will try and emulate from the ground transmitter what the paired chip transmitters usually do
[16:44] <rjharrison> I'll leave you in peace for a bit
[16:44] <fergusnoble> which i think is USB FSK
[16:44] <rjharrison> Cool
[16:44] <fergusnoble> so tell me about yours and steves payload? i didnt hear anything about it
[16:48] <Laurenceb> fergus: I guesstimated 5Km to 100Km with a small yagi
[16:48] <Laurenceb> hard to guesstimate the building loss
[16:48] <rjharrison> Well we used a RM module on FM on 187MHz unfortunately we lost the payload on descent
[16:48] <Laurenceb> I tested with an icom and radiometrix on a similar path
[16:49] <Laurenceb> I'd hazard a guess of at least 50Km
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[16:49] <Laurenceb> you should be able to get 200Km at least without the dodgy firmware on the UM12 modules
[16:49] <rjharrison> fergusnoble: we were just recording the audio output from the RM RX
[16:49] <Laurenceb> and with ganged yagis... :P
[16:50] <Laurenceb> fergus: you could try and emulate the Ti chip using a transceiver
[16:50] <Laurenceb> so your ground station is much more sensitive and has high power Tx
[16:51] <fergusnoble> Laurenceb: obviously we will use our greater power allowance
[16:51] <fergusnoble> 40W ftw
[16:52] <edmoore> fergusnoble: concentrate on skype not this please :p
[16:52] <rjharrison> fergusnoble: http://www.radiometrix.co.uk/products/ent1enr1.htm
[16:52] <rjharrison> fergusnoble: You have been told :)
[16:53] <Laurenceb> heh
[17:24] <rjharrison> Does anyone have a postcode for RocketBoy?
[17:24] <rjharrison> PM it if you do
[17:25] <edmoore> yep
[17:25] <edmoore> 2 secs
[17:26] <edmoore> done
[17:26] <rjharrison> edmoore Thanks
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[17:36] <Laurenceb> http://www.graphitestore.com/itemDetails.asp?item_id=1680&prd_id=143&cat_id=15&curPage=1
[17:46] <Laurenceb> are there low density castable ceramics?
[17:46] <Laurenceb> maybe you could airate it somehow...
[17:46] <edmoore> Laurenceb: yes
[17:46] <edmoore> the shuttle uses just such things
[17:46] <Laurenceb> yeah sure
[17:46] <edmoore> about the density of polystyrene
[17:46] <Laurenceb> ideal
[17:47] <Laurenceb> but castable like that stuff I linked?
[17:47] <edmoore> not sure.
[17:47] <Laurenceb> maybe you could add something to the mix
[17:48] <Laurenceb> e.g. CO2 generator
[17:48] <edmoore> so far the 817 has proved good at receiving radio 4
[17:48] <Laurenceb> heh I was doing that with my icom
[17:49] <Laurenceb> if you can get a martlet type rocket to 85% fuel fraction, N-prize becons
[17:49] <Laurenceb> the key seems to be what you use to support the motor
[17:49] <Laurenceb> ideally needs something about 0.25grams/Cm^3
[17:51] <Laurenceb> still much denser than polystyrene
[17:52] <rjharrison> the 817 will come into it's own on for the next balloon chase.
[17:52] <rjharrison> Other than that the 817 is great for R4
[17:57] <Laurenceb> of 5live
[17:57] <Laurenceb> *or
[17:57] <Laurenceb> tho thats just 100% sport or trash nowadays
[17:57] <Laurenceb> used to be good ~5 years ago
[18:00] <SpeedEvil> IIRC you can get quartz balls.
[18:00] <SpeedEvil> hollow
[18:00] <SpeedEvil> but they are expensive
[18:01] <Laurenceb> hey good point
[18:01] <Laurenceb> yeah
[18:01] <Laurenceb> its not a vast amount of airation raquired
[18:01] <SpeedEvil> Cinderblocks!
[18:01] <SpeedEvil> :)
[18:01] <Laurenceb> its worth putting more work into the second stage as its so small
[18:01] <Laurenceb> - for n [prize
[18:01] <SpeedEvil> yeah
[18:01] <SpeedEvil> lots
[18:02] <Laurenceb> ~2.6Kg total mass
[18:02] <Laurenceb> if you can get at least 85% fuel then a 25Kg glow attempt is possible
[18:02] <Laurenceb> with 100 gram payload
[18:02] <Laurenceb> cessaroni L1115-P-U motor for the second stage
[18:03] <Laurenceb> and helium pressure fed H2O2/Kerosene for the first
[18:04] <Laurenceb> use a pyro blown diagphram to vent the ullage gas for spinning up the second stage nmaybe
[18:05] <Laurenceb> although a rifled CF tube "cannon" type launch system would have less to go wrong and be approx the same weight
[18:08] <SpeedEvil> I'm unsure how easy it is to get it spinning withoutt eccentricity
[18:09] <Laurenceb> yeah
[18:10] <Laurenceb> compressed helium baerings are going to be hard
[18:10] <Laurenceb> prob better to try a rifled tube
[18:10] <Laurenceb> nice and light if its CF with angled spring blades on the secondary
[18:11] <Laurenceb> *sprung
[18:11] <SpeedEvil> I mean with the rifled tube
[18:12] <Laurenceb> I dont follow?
[18:12] <Laurenceb> the tube isnt machined in any way
[18:12] <Laurenceb> just have angled blades on the 2nd stage digging into the sides
[18:12] <Laurenceb> 3 or fopur of them
[18:13] <SpeedEvil> I'm unsure how well that'll work - it seems easy to get it bouncing around uncleanly
[18:14] <Laurenceb> depends how well the tube is made
[18:14] <Laurenceb> if it was wrapped on a mandrel, it should be smooth
[18:18] <Laurenceb> its all pretty buildable
[18:21] <Laurenceb> you could even yet it to 32Km with £800 of latex balloons
[18:28] <SpeedEvil> I mean - instability in pointing due to the diameter of the projectile being not the same as the tube - and it rattling out of the tube, not spinning cleanly out
[18:29] <Laurenceb> theres nothing to stop you adding some sort of spigot
[18:30] <Laurenceb> or just thin foam pads with PTFE covering
[18:31] <SpeedEvil> I think you mean sabot.
[18:31] <SpeedEvil> yeah
[18:32] <Laurenceb> hmm 16 Kaymont 1000gram balloons :P
[18:36] <Laurenceb> I was working on an aluminuium ablative lined chamber
[18:37] <Laurenceb> graphite nozzle with jet vanes servo operated, pintle injector
[18:37] <SpeedEvil> hmm
[18:37] <SpeedEvil> Al _really_ sucks if it gets slightly warm structurally
[18:38] <SpeedEvil> As in major strength loss at 200C
[18:38] <SpeedEvil> (though alloys vary a little)
[18:42] <Laurenceb> its not going to
[18:42] <Laurenceb> just a bit easier to machine
[18:42] <Laurenceb> and a bit better heat wise than CF
[18:43] <Laurenceb> the only tricky bits are machining the nozzle - lathe and injector - also lathe
[18:43] <Laurenceb> stick a servo on the injector for throttling
[18:44] <Laurenceb> anyway, gtg, cya
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[18:47] <SpeedEvil> machining the lathe?
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[19:25] <Laurenceb> http://www.cotronics.com/vo/cotr/pdf/onepg700.pdf the foam there together with quartz microballoons should get to a nice low density
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[19:27] <SpeedEvil> I only vaguely remember quartz microbaloons - check they are in facct available
[19:27] <SpeedEvil> however - what's the curing temp?
[19:28] <Laurenceb> room
[19:29] <SpeedEvil> well - won't polystyrene beads work?
[19:29] <Laurenceb> http://www.cotronics.com/vo/cotr/pdf/onepg700.pdf
[19:30] <Laurenceb> they'll melt... but maybe it wont matter
[19:30] <Laurenceb> woops
[19:30] <Laurenceb> http://www.eagerplastics.com/7962.htm
[19:30] <SpeedEvil> as long as the vapour can get out
[19:30] <Laurenceb> yeah
[19:30] <Laurenceb> it only has to be a layer ~1mm thick
[19:30] <SpeedEvil> I got a kilo of glass balloons from 3m.
[19:31] <SpeedEvil> They look _so_ pretty under a microscope.
[19:31] <Laurenceb> to protect the CF wall from overheating due to uneaven burnout
[19:31] <SpeedEvil> Like frozen balls of rainbow.
[19:31] <SpeedEvil> you spread this over the whole wall?
[19:31] <Laurenceb> yes
[19:31] <Laurenceb> or rather pour it in around the motor
[19:32] <Laurenceb> or fuel even
[19:32] <SpeedEvil> this is around the motor?
[19:32] <SpeedEvil> err
[19:32] <SpeedEvil> I've lost where you're at.
[19:33] <Laurenceb> for a second stage
[19:33] <Laurenceb> mini spun thing, 2.5Kg total weight
[19:33] <Laurenceb> you need something around the fuel grain to protect the CF wall
[19:33] <SpeedEvil> Why?
[19:33] <SpeedEvil> oh
[19:34] <SpeedEvil> this is at the very end of the burn
[19:34] <Laurenceb> uneaven burnthrough
[19:34] <Laurenceb> yes
[19:34] <SpeedEvil> so you don't have massive undesigned off-nominal thrust.
[19:34] <Laurenceb> has to last a few hundered ms
[19:34] <SpeedEvil> When you grow a second nozzle in the sid.e
[19:34] <Laurenceb> exactly
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[19:35] <SpeedEvil> Do youhave thrust termination?
[19:35] <Laurenceb> nope
[19:35] <SpeedEvil> Or are you basically praying it doesn't over/underperform
[19:35] <Laurenceb> off the shelf cessaroni motor
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[19:35] <SpeedEvil> doesn't +-5% say screw you?
[19:36] <Laurenceb> you need a few % extra
[19:37] <SpeedEvil> oh - of course
[19:37] <SpeedEvil> to first order, your perigee is set by burn alt. Your apogee only is set by impulse.
[19:37] <Laurenceb> exactly
[19:37] <Laurenceb> launch first stage into gravity turn
[19:37] <Laurenceb> then at apogee fire the second
[19:38] <Laurenceb> problem is it needs to be pointing right
[19:38] <Laurenceb> I think you can get away with aerodynamic stabilisation after burnout
[19:38] <Laurenceb> - burnout is at around 80Km
[19:38] <Laurenceb> and it should be stable
[19:38] <SpeedEvil> umm.
[19:39] <SpeedEvil> There isn't thhat much atm there.
[19:39] <Laurenceb> as long as you attitude control is good
[19:39] <Laurenceb> but its going 4.5Km/sec
[19:40] <SpeedEvil> I dunno about the hypersonic gas dynamics though. I'm unsure how it stabilises.
[19:41] <Laurenceb> a few hundered mN potentially at play
[19:41] <SpeedEvil> Your mean free path there is still quite small isn't it.
[19:41] <Laurenceb> yeah, the nose
[19:41] <Laurenceb> yes
[19:44] <Laurenceb> you could spin up the first stage
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[19:48] <Laurenceb> no...
[19:48] <SpeedEvil> that'd make pointing a bit harder
[19:48] <SpeedEvil> and teh slosh is annoying
[19:48] <jcoxon> evening all
[19:48] <Laurenceb> exactly
[19:49] <SpeedEvil> however - an electric spin motor isn't heavy
[19:49] <Laurenceb> slosh isnt, due to the high G near burnout
[19:49] <Laurenceb> yeah but the avaliable torque is low
[19:49] <SpeedEvil> Laurenceb: how?
[19:49] <Laurenceb> work it out
[19:49] <SpeedEvil> Laurenceb: Do you need to do the accelleration in a couple of seconds?
[19:49] <Laurenceb> well if you start flying sideways
[19:50] <Laurenceb> its bad for drag
[19:50] <SpeedEvil> what's the upper stage mass
[19:50] <Laurenceb> 2.5Kg
[19:50] Action: SpeedEvil ponders.
[19:50] <Laurenceb> jettison the first stage
[19:50] <SpeedEvil> Spin the cubesat at launch.
[19:50] <Laurenceb> - launch tube and tronics
[19:50] <SpeedEvil> Brake to spinup second stage
[19:50] <Laurenceb> no cubesat here, just a 100gram payload
[19:51] <SpeedEvil> Probably not sensible
[19:51] <SpeedEvil> ah
[19:51] <Laurenceb> n-prize
[19:51] <Laurenceb> 25Kg GLOW
[19:52] <Laurenceb> you could dump the first stage and have the tronics, 2second stage and launch tube carry on
[19:52] <Laurenceb> itd actually be better for drag
[19:53] <SpeedEvil> this is spinning to avoid any guidance needs?
[19:53] <Laurenceb> no
[19:53] <Laurenceb> fins
[19:53] <SpeedEvil> the second stage
[19:54] <Laurenceb> no
[19:54] <Laurenceb> a launch tube for the second stage
[19:54] <Laurenceb> and the second stage + the guidance electronics
[19:54] <Laurenceb> with fins on the back
[19:54] <SpeedEvil> pop-out oversized fins on the main stage?
[19:58] <Laurenceb> too heavy
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[19:58] <Laurenceb> aha I know
[19:58] <SpeedEvil> http://www.theregister.co.uk/2009/06/05/tob_minuteman_1/
[19:58] <SpeedEvil> seen that?
[19:58] <rjharrison> Evening all
[19:58] <Laurenceb> at burnout turn off the main fuel + oxidiser valve
[19:58] <SpeedEvil> I suspect it'd be lots lighter than staging
[19:59] <Laurenceb> then coast up to staging altitude
[19:59] <Laurenceb> then open it to release the helium
[19:59] <Laurenceb> use to jet vanes to get correct attitude
[19:59] <SpeedEvil> hmm
[19:59] <Laurenceb> requies so o rings so it can seal properly
[19:59] <SpeedEvil> you'd I think want a mode where you barely crack the valve open
[20:00] <Laurenceb> I was thinking of a pintle injector valve operated via a toothed belt from a servo
[20:01] <Laurenceb> I dont think sideways flight would be a problem
[20:02] <Laurenceb> as soon as you start incurring drag, its correct the flight
[20:02] <Laurenceb> so its start oscillating
[20:02] <Laurenceb> and as you got above about 120Km its probably start rotating 360 degrees
[20:03] <Laurenceb> if the tail was inside the bow shock there wouldnt be much torque on the stage
[20:05] <SpeedEvil> doesn't drag stabilised launch have a fundamental issue if that sets your perigee?
[20:05] <Laurenceb> its only drag stabilised after burnout
[20:05] <Laurenceb> the jet vanes are used before
[20:06] <Laurenceb> for a realistic first stage flight you have to have a cruise period
[20:06] <SpeedEvil> ah - right - follow you now
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[20:06] <Laurenceb> around 60 seconds
[20:07] <Laurenceb> launch 30km, cruise under jet vanes for 40seconds to 80Km, 4.5Km/s, cruise to 200Km, 4.1Km/s or so, then use helium to correct attitude, fire second horizontally
[20:08] <Laurenceb> second accelerates to orbital V +a bit of tolerance, giving some elliptical orbit
[20:08] <SpeedEvil> what's your helium mass again?
[20:08] <Laurenceb> 300 grams
[20:08] <SpeedEvil> hmm.
[20:08] <Laurenceb> if ISP=100
[20:09] <Laurenceb> and you have 1% thrust authority with the jet vanes, it works ok
[20:09] <SpeedEvil> I suppose you are strongly limited in that case by your vector angle
[20:09] <SpeedEvil> for the jet
[20:10] <Laurenceb> yeah
[20:10] <SpeedEvil> what total angular accelleration does that work out to?
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[20:11] <SpeedEvil> three teeny vent holes on the side I suppose are another option
[20:11] <SpeedEvil> and solenoids
[20:11] <Laurenceb> about 0.3 rads per sec
[20:12] <SpeedEvil> not horrible.
[20:13] <Laurenceb> youd want to test fly the first with a dummy second to see exactly what happens
[20:13] <Laurenceb> may turn out oscillations are strongly damped
[20:13] <SpeedEvil> For most of it, you can test with lots less even.
[20:13] <SpeedEvil> 50Km even at apogee
[20:14] <SpeedEvil> for the thrust vectoring of helium test
[20:15] <Laurenceb> if oscillations tend to build up you could be very clever
[20:15] <Laurenceb> and do thrust vectoring throughout the cruise period
[20:15] <Laurenceb> with gradual helium venting
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[20:16] <Laurenceb> not sure if mesospheric wind gusts could screw up that approach
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[20:34] <Laurenceb> bbl, cya
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[20:55] Nick change: G8KHW-2 -> RocketBoy
[21:19] <edmoore> hi jcoxon
[21:19] <edmoore> what's new?
[21:19] <edmoore> last one tomorrow!
[21:23] <jcoxon> indeed
[21:23] <jcoxon> just popping to tescos for chocolate
[21:23] <jcoxon> bbiab
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[22:24] <jcoxon> back
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[22:40] <AlexBreton> Hi all
[22:40] <AlexBreton> just buying the celotex for our balloon
[22:41] <AlexBreton> what thickness would you recommend?
[22:41] <AlexBreton> 25, 30, 40 or 45mm?
[22:43] <SpeedEvil> whatever they've got broken bits of.
[22:43] <AlexBreton> erm, we are no so poor as so to resort to broken bits
[22:43] <AlexBreton> ;-)
[22:43] <AlexBreton> a local store has 50mm
[22:44] <SpeedEvil> 50mm should work fine.
[22:45] <AlexBreton> we'd have to buy it from them
[22:45] <AlexBreton> easier to order online
[22:45] <AlexBreton> transport options are kinda buggered lately
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[23:04] <Laurenceb> back
[23:05] <edmoore> night all
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[23:06] <SpeedEvil> http://news.bbc.co.uk/1/hi/uk/8138012.stm
[23:06] <SpeedEvil> sort of CF related
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[23:36] <Laurenceb> http://en.wikipedia.org/wiki/File:GoogleRack_ComputerHistoryMuseum.jpg
[23:36] <Laurenceb> ^crazy
[23:36] <Laurenceb> talk about cheap
[23:37] <Laurenceb> corrigated cardboard insulation and aluminium trays are so thin its bending the motherboards
[23:38] <Laurenceb> they couldnt even afford cable ties
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[23:40] <SpeedEvil> I doubt it.
[23:41] <SpeedEvil> That looks like a space prototype
[23:41] <SpeedEvil> where everything is put in the right positions - but not held together as it should be
[23:42] <SpeedEvil> I think much of that bending is also camera distortion
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[23:51] <Laurenceb> I want to build this rocket design now :P
[23:52] <Laurenceb> wonder how hard it is to machine graphite
[23:57] <Laurenceb> http://en.wikipedia.org/wiki/File:EPFL_CRAY-II_2.jpg <- eeeeeeeekkk
[23:58] <SpeedEvil> yeah
[00:00] --- Wed Jul 8 2009