highaltitude.log.20090924

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[02:34] <ybit> heyo speedevil
[02:35] <ybit> you mentioned that http://solar-flight.com/ is almost meaningless, could you expand upon that thought?
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[03:50] <swilly> Can someone explain what free lift is vs nozzle lift?
[03:51] <swilly> I'm trying to calculate what size balloon to purchase for a 2lb payload
[03:51] <swilly> I knew this last year, but have gotten them mixed up again
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[06:31] <ybit> related to what i was asking about yesterday: http://sugarshot.org/project_description.html and http://en.wikipedia.org/wiki/Rockoon
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[06:33] <natrium> rokoons can get you above 100km, but not to orbit
[06:46] <ybit> that's what wikiepdia says
[06:46] <ybit> minus the 'not to orbit' part but it's kind of implied
[06:46] <natrium> CUSF has been working on a rokoon
[06:47] <natrium> try to catch edmoore if you're interested :)
[06:48] <ybit> California State University, Fullerton or Fresno?
[06:48] <ybit> it just needs to go about 60 more km to orbit..
[06:49] <natrium> http://www.srcf.ucam.org/~cuspaceflight/
[06:49] <natrium> cambridge university spaceflight
[06:49] <natrium> http://www.srcf.ucam.org/~cuspaceflight/martlet.php
[06:50] <ybit> Martlet - Design of a small sounding rocket, capable of launch from a high-altitude balloon that would give access to altitudes of up to 150km.
[06:50] <ybit> it lacks ~10km
[06:50] <natrium> why? what happens at 160km?
[06:51] <ybit> low earth orbit
[06:52] <ybit> http://en.wikipedia.org/wiki/Low_Earth_Orbit
[06:52] <natrium> you still need to gain orbital speed :P
[06:53] <natrium> which needs the greatest energy
[06:54] <natrium> getting to 160km is damn easy in comparison
[06:54] <ybit> which is...
[06:55] <ybit> http://en.wikipedia.org/wiki/Orbital_speed#Earth_orbits
[06:55] <ybit> ~7km/s, that doesn't seem too difficult
[06:55] <natrium> 1.0 MJ/kg vs 32.1 to 38.6 MJ/kg
[06:55] <natrium> it's an order of magnitude
[06:56] <ybit> i was just getting to that column, give me a sec will ya :P
[06:56] <natrium> that's 25,200 km/h
[06:58] <ybit> humor me, how cna that be so when the earth's escape velocity is 11.2 km/s
[07:00] <ybit> it just seems to me that you wouldn't needn't as much speed to enter orbit
[07:00] <ybit> but then again, maybe you do need it to maintain orbit because of the earth's gravitational pull. dunno which is why i ask
[07:01] <natrium> no, to keep a circular orbit you need a force towards the center
[07:03] <natrium> it's like swinging a weight on a string
[07:03] <natrium> you will feel some pull, which is actually you providing a force to keep the weight in circular motion
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[13:14] <Laurenceb> http://pastebin.com/m7208a958
[13:15] <Laurenceb> thats what I found in the DIYDrones code
[13:15] <Laurenceb> looks like they have a low pass filter on airspeed and a zero calibration at bootup
[13:15] <Laurenceb> not sure how well that will take to temperature changes :-/
[13:18] <SpeedEvil> Or altitude?
[13:18] <Laurenceb> yeah... I'm just trying to work out if they compensate for air density
[13:21] <Laurenceb> /Throttle
[13:21] <Laurenceb> throttle_set_point=PID_throttle(air_speed_hold, airSpeed(), t_dt);
[13:21] <Laurenceb> pulse_servo_0((throttle_set_point));
[13:21] <Laurenceb> AIUI they pitch up and down to reach the correct altitude
[13:22] <Laurenceb> I'm not sure if air_speed_hold is set be another control loop
[13:24] <Laurenceb> ooh no //Here will take the altitude error to control the throttle, has proportional and limits.
[13:24] <Laurenceb> air_speed_hold=constrain(AIRSPEED_CENTRAL+(alt_error*ALTITUDE_ERROR_AIRSPEED_PROPORTIONAL),ALTITUDE_ERROR_AIRSPEED_MIN,ALTITUDE_ERROR_AIRSPEED_MAX);
[13:24] <Laurenceb> pitch_set_point=constrain(alt_error*ALTITUDE_ERROR_PITCH_PROPORTIONAL,ALTITUDE_ERROR_PITCH_MIN,ALTITUDE_ERROR_PITCH_MAX);
[13:24] <Laurenceb> devious
[13:24] <Laurenceb> looks like they pitch up and increase speed
[13:25] <Laurenceb> hmm I suspect airspeed drift will be filtered out by that technique
[13:35] <Laurenceb> thats kind of annoying - I wondered maybe the sensor was good enough to give you reliable airspeed
[13:35] <Laurenceb> so it looks like they solved the drift issue by cheating
[13:37] <Laurenceb> and theres no altitude compensation
[13:38] <Laurenceb> they just use some macros
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[17:02] <rjharrison> Evening all
[17:03] <rjharrison> I'm planing a saturday launch ATM
[17:03] <rjharrison> Typically I think CUSF might be too
[17:08] <DanielRichman> oooh
[17:15] <SpeedEvil> :)
[17:20] <rjharrison> Not Icarus III but Icarus II
[17:20] <rjharrison> so only temp sensors in and out
[17:28] <DanielRichman> :(
[17:29] <DanielRichman> I really ought to get a decent aerial... sbasuita reckons that we'll be able to get a yagi on the day, and we're signed up on a HAM course, all that is available right now is a whip
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[17:56] <rjharrison> DanielRichman You'll be fin with a whip
[17:56] <rjharrison> Can you stick it up high somewhere
[17:56] <rjharrison> I can do 200miles on a whip
[17:57] <DanielRichman> don't fancy climbing onto the roof but I am on the second story
[17:58] <SpeedEvil> At the moment I have my 3G modem on a 5m mast made from 3 bits of bamboo.
[17:58] <SpeedEvil> Works well
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[18:05] <rjharrison> right off home chat later
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[20:22] <natrium42> hi
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[20:25] <rjharrison_> Off to olimex now :)
[20:26] <rjharrison_> http://www.robertharrison.org/svn/filedetails.php?repname=the-icarus-project&path=%2FIcarus+III%2Feagle%2FIcarus+III%2FIcarus-brd.pdf
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[20:27] Nick change: natrium42_ -> natrium42
[20:28] <rjharrison_> any eagle peopel who want to have a quick look the files are here
[20:28] <rjharrison_> http://www.robertharrison.org/svn/listing.php?repname=the-icarus-project&path=%2FIcarus+III%2Feagle%2FIcarus+III%2F#path_Icarus%20III_eagle_Icarus%20III_
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[22:00] <fuzzylugnuts> Hey
[22:01] <natrium42> Oy
[22:02] <fuzzylugnuts> how's it going?
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[22:02] <natrium42> good, how are you/
[22:03] <fuzzylugnuts> Pretty good. Thinking about making cap discharge battery tabber
[22:05] <fuzzylugnuts> and other things
[22:06] <fuzzylugnuts> thinking about that phiget stuff too
[22:20] <fuzzylugnuts> I dunno
[22:20] <fuzzylugnuts> on the plus side my old ballooning group is going down the same path as me, so we can help eachother
[22:21] <SpeedEvil> I had good results soldering to cells.
[22:21] <SpeedEvil> Worked for me.
[22:22] <SpeedEvil> Absolute cleanliness is the key.
[22:22] <fuzzylugnuts> Yeah, I have a bit too without any ill affects
[22:22] <SpeedEvil> Clean cell surfaces. On a horizontal tip of a hot iron, build up a blob of solder, and apply the cell, then remove.
[22:22] <SpeedEvil> this step should take under a second.
[22:22] <fuzzylugnuts> :O
[22:23] <SpeedEvil> You should be able to touch the cell immediately after the solder.
[22:23] <fuzzylugnuts> :P
[22:23] <fuzzylugnuts> dude
[22:23] <fuzzylugnuts> chill
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[22:23] <SpeedEvil> then after a few mins, tin some wire, press it against the tinned area, and repeat the above process.
[22:23] <SpeedEvil> Voila - nice solderjoint.
[22:24] <SpeedEvil> With very little heat input
[22:24] <fuzzylugnuts> its just that I have a 400v, 5,400uf cap just itching to be used.
[22:24] <SpeedEvil> what sort of cap?
[22:24] <fuzzylugnuts> electrolytic
[22:25] <fuzzylugnuts> I have alot of projects on the table right now
[22:26] <fuzzylugnuts> so it probably won't happen
[22:26] <SpeedEvil> that's what - 300J?
[22:27] <fuzzylugnuts> oh man.. what is it.. 1/2 capacity times voltage^2 ?
[22:28] <fuzzylugnuts> I sold one of my pride and joys on ebay a while back... a 100uf 3kv cap
[22:28] <fuzzylugnuts> so many fond disk launching memories
[22:28] <SpeedEvil> nice
[22:28] <fuzzylugnuts> it was enough juuuuuust to make a little dent in an aluminum can if I wrapped some solid wire around it
[22:29] <fuzzylugnuts> back in highschool.
[22:30] <fuzzylugnuts> that was some fun.
[22:30] <fuzzylugnuts> the ballooning stuff has been interesting though
[22:31] <fuzzylugnuts> seems like there is so much you can get into
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[22:41] <fuzzylugnuts> I really like this POS keyboard. Its got a built in touchpad
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[23:01] <fuzzylugnuts> anyone use GrLevel3?
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[23:48] <RocketBoy> rjharrison_:
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[23:53] <swilly> I have a quick question concerning this chart for balloons: http://www.kaymont.com/pages/sounding-balloons.cfm . Is the "free lift" in the chart taking into account the weight of the balloon and listed payload?
[23:54] <SpeedEvil> Free lift is the unbalance force of the balloon
[23:55] <SpeedEvil> So the 200g balloon - you inflate until it's got 510g of force pulling upwards - and you get the recommended condition
[23:55] <swilly> ah
[23:56] <SpeedEvil> payload is 250g - so the unbalanced force when you put both on is 260g
[23:56] <swilly> thanks!
[23:56] <SpeedEvil> which means that it will go upwards with that force
[23:56] <swilly> how much lift is normally recommended for a loaded balloon
[23:56] <SpeedEvil> Err
[23:56] <SpeedEvil> I may be confused
[23:56] <SpeedEvil> sorry - it's late
[23:56] <swilly> not a problem
[23:57] <SpeedEvil> yeah - that's wrong.
[23:57] <SpeedEvil> The above thing I was describing is nozzle lift - the force you measure when filling it to see if it's full enough
[23:57] <swilly> i see
[23:57] <swilly> actually - I should have googled first :(
[23:57] <swilly> http://balloon.pbworks.com/BalloonMath
[23:58] <SpeedEvil> Gross lift = the whole amount of lift. Subtract the balloon weight to get nozzle lift
[23:58] <SpeedEvil> subtract the payload weight to get free lift
[23:58] <SpeedEvil> ah
[23:58] <swilly> do you launch balloons?
[23:58] <SpeedEvil> I have plans - but not actually launched one
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[00:00] --- Fri Sep 25 2009