highaltitude.log.20151104

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[01:28] <BeaverOne> https://www.flickr.com/photos/100852237@N06/22737804886/in/dateposted-public/
[01:40] <mbales_> wooo!
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[02:57] <BeaverOne> Laurenceb: http://www.ams.org/journals/ert/2015-19-11/S1088-4165-2015-00470-4/S1088-4165-2015-00470-4.pdf
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[08:43] <SpacenearUS> New position from 03DL1NBR-12 after 032 days silence - 12http://tracker.habhub.org/#!qm=All&q=DL1NBR-12
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[09:02] <WillDWork> I see that Super Strypi launcher failed
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[09:11] <fsphil> yes it did a spinny thing
[09:13] <fsphil> totally a technical term
[09:19] <fsphil> their radio link seems to have worked well even after it broke up
[09:30] <RealBorg> sad to say that humanity was technologically more advanced by the end of the 60s
[09:31] <x-f_> why so?
[09:31] Nick change: x-f_ -> x-f
[09:33] <RealBorg> saturn v rocket is unsurpassed for its payload (and probably reliability)
[09:39] <RealBorg> strypi has a payload of 250kg to sso, the saturn v had a payload of 48,600kg to tli
[09:40] <x-f> super strypi's purpose was a cheap launch vehicle
[09:55] <RealBorg> it failed. spectacularly. a very expensive firework
[10:02] <day> RealBorg: dont forget all the awesome war tech the cold war created...
[10:02] <day> i could watch the SPRINT rocket videos all.day.long
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[10:03] <RealBorg> and there is nothing as ambitous as the x33 and sr-71
[10:03] <RealBorg> these days
[10:04] <day> yy. new technologies completely changed the game and made pushing existing technology useless :(
[10:04] <day> how good is an observation plane if you can have satellites
[10:05] <RealBorg> space shuttle: retired; concorde: out of service; last visit to moon: 43 years ago
[10:06] <day> isnt china planning a manned moon mission?
[10:07] <RealBorg> us is planning a mars mission - to be financed and approved by a congress and president yet to be elected
[10:08] <day> what do they even want there? i think there are better ways to spend money :/
[10:09] <day> granted they need to keep a balance between actual progress and making news to keep the money flowing. but still
[10:13] <RealBorg> I'd like to set up a permanent basis on the moon
[10:13] <day> i did like that too. but, would it serve a purpose?
[10:16] <RealBorg> showing that it can be done, that humans can permanently live in space
[10:16] <RealBorg> better purpose than to continue observing the effects of leo/microgravity
[10:17] <fsphil> RealBorg: they failed this time. maybe they'll learn what went wrong and try again, maybe they'll learn the whole idea was bad. either way it's not all bad
[10:17] <RealBorg> little gravity and no atmosphere would make it an ideal base for further missions
[10:17] <day> but a moon base wouldnt be all that different from an earth base. Just without an atmosphere and less gravity
[10:18] <day> by that logic a spacestation would be much better.
[10:18] <RealBorg> 1/3 of gravity means you can build structures 3 times as big/high and need less than 1/3 of the fuel to get them into space
[10:19] <Geoff-G8DHE_> Where is the fuel going to come from ? Earth ?
[10:19] <day> RealBorg: no starting something from earth you pay earth + moon landing + moon start
[10:19] <RealBorg> maybe if that space station had a huge airlock for assembling things
[10:20] <Geoff-G8DHE_> Also you would want to dig down not up so that you can better shielding and insulation
[10:21] <RealBorg> arguably there is stuff on the moon we can use
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[10:23] <eroomde> RealBorg: it's energetically much easier to explore the rest of the solar system from LEO than from the moon
[10:24] <eroomde> there might be reasons to go to the moon but that isn't one of them
[10:24] <day> eroomde: do you have one? im thinking real hard, but i cant come with anything that would benefit from it
[10:24] <eroomde> not really
[10:24] <RealBorg> energetically yes, but when I see astronauts working in microgravity i think the 1/3 gravity would help a lot
[10:24] <day> it has to be something that requires gravity
[10:24] <day> but cant be done on earth
[10:25] <fsphil> radio obervations from the far side
[10:25] <eroomde> maybe astronomy
[10:25] <fsphil> that's about it
[10:25] <eroomde> an IR scope or something
[10:25] <gonzo_> apart from the science from a few samples of moon rock, did we achieve anything from the actual moon landings. I mean the landing itself, not the exercise in getting there.
[10:25] <fsphil> the moon is a rather good shield
[10:25] <day> fsphil: i thought about that as well. but you could do that from space as well. and if you need the moon shielding you could put it in the L point behind the moon
[10:25] <daveake> 1/6th gravity fwiw
[10:25] <eroomde> gonzo_: not really manned spaceflight is basically the crappest way of doing science
[10:26] <eroomde> per $
[10:26] <gonzo_> that was a way of doing politics
[10:29] <fsphil> day: that's a fair point
[10:29] <fsphil> would need station keeping thrusters, but that's still easier than landing
[10:31] <eroomde> well the moon might be a bit easier from a longevity pov
[10:31] <eroomde> you could assemble something large
[10:32] <eroomde> you could heat sink into the moon to keep everything like detectors cool indefinitely
[10:32] <fsphil> the 2 week night could be useful for that
[10:32] <eroomde> yep
[10:32] <eroomde> you don't have to package everything to fit in a single fairing
[10:32] <eroomde> tho i guess any of these plans assume a different model for launching stuff
[10:33] <eroomde> some sort of very cheap way to repidly deliver a few tonnes at a time to LEO for about 10-100x cheaper than the current cost
[10:33] <eroomde> someone should work on solving that problem really, because that's the most important problem to solve atm
[10:34] <SpeedEvil> yeah.
[10:34] <SpeedEvil> :)
[10:34] <day> eroomde wants his cubesat :D
[10:34] <SpeedEvil> All of this 'energetic' shit utterly misses the point.
[10:34] <SpeedEvil> As does lightweight design, and ISRU and ...
[10:35] <SpeedEvil> It all gets much, much cheaper if you get the launch cost down to what technology allows.
[10:35] <eroomde> day: nope, i'm working on something else!
[10:35] Action: SpeedEvil wants to ride in a UK spaceplane too.
[10:35] <day> i doubt that there will be a big cost change as long as we are forced to use rockets
[10:35] <day> eroomde: details? :3
[10:36] <eroomde> if you can make them completely reusable...
[10:36] <SpeedEvil> day: Rockets can get well below 1/10th of current cost.
[10:36] <fsphil> L2 is 67000km above the lunar surface. annoying
[10:36] <day> SpeedEvil: fuel isnt the main price driver?
[10:36] <SpeedEvil> day: The fuel cost for a falcon 9 to launch 20 tons to LEO is $300K or so. Under 1% of the launch cost.
[10:36] <day> oh
[10:36] <eroomde> day: not in the least
[10:36] <eroomde> fuel costs nothing
[10:37] <SpeedEvil> Solid rockets can cost more.
[10:37] <eroomde> it's the fact that you're making something as complex as a 747 and throwing it away after every flight
[10:37] <day> what is the price driver then?
[10:37] <day> it cant be RnD
[10:37] <SpeedEvil> day: handbuilding 747s and throwing them away.
[10:37] <eroomde> it's entirely analogous to the price of a transatlantic flight ticket if the plane was single use vs what transatlantic flight tickets actually cost us now
[10:38] <day> SpeedEvil: well we had spaceshuttles, were they significantly cheaper?
[10:38] <eroomde> no
[10:38] <eroomde> lol
[10:38] <eroomde> they werent really reusable, but just rebuildable
[10:38] <day> well...at best :P
[10:38] <eroomde> they took them apart after every flight and inspected and xrayed every engine components and so on
[10:39] <eroomde> and the SRBS and main fuel tank were disposable anyway
[10:39] <eroomde> and it was built by 437 different contractors across all 50 states on cost-plus
[10:39] <eroomde> and the design drivers were different government agencies with conflicting and silly requirements
[10:39] <SpeedEvil> Actually all 50 states?
[10:39] <eroomde> but the idea behind the shuttle is the right one
[10:39] <SpeedEvil> (It wouldn't surprise me)
[10:40] <eroomde> no probably not, though there will be a huge army of tiny sub-sub contractors to the primes spread all over
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[10:40] <eroomde> day: my personal opinion is that this is the right idea: http://www.bbc.co.uk/news/business-34694935
[10:40] <SpeedEvil> The idea behind teh shuttle is one of the right ones.
[10:40] <eroomde> and to that end, I'm working on the sabre engine
[10:40] <day> i dont think its feasable to reuse the thrusters. it would take a lot of money to get them down safely :/
[10:40] <SpeedEvil> What is technically feasible is the other question.
[10:40] <SpeedEvil> day: Falcon 9 has 99.9999% (I think that's the right number) managed engine reuse.
[10:40] <day> eroomde: as in private or professional?
[10:41] <RealBorg> eroomde, did you note I mentioned the X33 and SR71 before? ;)
[10:41] <eroomde> professional
[10:41] <eroomde> i'm doing r+d on the sabre engine as my job, right now
[10:41] <day> neat
[10:41] <eroomde> apart from actually being on irc talking to you right now
[10:41] <SpeedEvil> It came from 200km/3km/s, to 2m/10m/s without issue.
[10:41] Laurenceb_ (~Laurence@host86-143-55-195.range86-143.btcentralplus.com) joined #highaltitude.
[10:41] <SpeedEvil> It was just the remaining 10m/s that was the issue.
[10:41] <eroomde> RealBorg: I didn't note that, no
[10:41] <day> eroomde: which obviously helps technology progress much more! :p
[10:41] <eroomde> lol
[10:42] <SpeedEvil> There is no question that first stages can be reused - second stages are harder. Airbreathing engines are novel, and rather harder still.
[10:42] <SpeedEvil> But potentially very awesome.
[10:42] <SpeedEvil> And potentially cheaper given some assumptions.
[10:42] <SpeedEvil> It's like the Drake equation.
[10:42] <day> i figured that one out in kerbal already :D
[10:42] <eroomde> but we have now shown the key bits of the airbreathing work, in steady state, in representative conditions
[10:42] <eroomde> at about flight scale
[10:42] <RealBorg> great
[10:43] <SpeedEvil> There are so many assumptions that you can take either way that it can be hard to nail stuff down to what can be flying in 10 years for what cost.
[10:43] <eroomde> it's now a more straightforward engineering job to package it all into a demo engine, rather than dundamental r+d
[10:43] <eroomde> well, r
[10:44] <day> eroomde: what is your background (as in what did you study)
[10:44] <eroomde> engineering batchelors and masters
[10:44] <day> oh. i expected something more fundamental.
[10:44] <eroomde> and once upon a time run CUSF, which is where the hab link comes from
[10:44] <RealBorg> "2010 a space odyssey" was based on scientific prediction of the future
[10:45] <eroomde> day: they start from first principles where i did my degree, so that's god enough
[10:45] <eroomde> good*
[10:46] <eroomde> so long as you have a fairly solid understanding of thermodynamics, the rest is fairly sraightforward
[10:46] <day> eroomde: i expected the project to be more in a fundamental research stage. as in Physics/Maths guys mainly
[10:46] <SpeedEvil> It's just plumbing, but if you do it right, shit flows uphill.
[10:46] <eroomde> the cycle of the sabre engine is a bit complicated, but only compared to normal rocket engines. it's fine if you think about it thermodynamically, as the careful moving of energy and power about the place
[10:46] <day> i dont think thats how plumbing is supposed to work SpeedEvil :x
[10:46] <RealBorg> engineers brought man to the man, scientists now discuss the moral ethics of sending people to mars
[10:46] <eroomde> but if you have a background as a missile guy, like many rocket people, it can be a bit confusing
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[10:47] <eroomde> but once you home into actually making the thing, it's just heat transfer equations like you'd use if you were designing office air conditioning units
[10:47] <eroomde> just with a much higher power density and much higher risk of explosion and more chemistry and so on, but the maths is the same
[10:47] <SpeedEvil> day: To a large degree, the physics is very well understood. For each tiny point in the system, the equations are mostly tractable and understandable by any physicist. It's the interaction between them into a whole functioning engine which is complex, and engineering more than fundamental physics.
[10:48] <craag> tldr; extreme hvac
[10:48] <SpeedEvil> There are _so_many_ fields in which this is true.
[10:48] <fsphil> software development :)
[10:48] <SpeedEvil> Simple physics understanding may not help you that much.
[10:48] <eroomde> yes, the engineering is often harder than the physics
[10:48] <day> said the engineer :D
[10:48] <eroomde> well it's true
[10:48] <eroomde> i understand all the physics
[10:49] <SpeedEvil> https://www.youtube.com/watch?v=vYA0f6R5KAI - is related.
[10:49] <SpeedEvil> The physics of rocket engines is 'simple'.
[10:49] <RealBorg> but engineering is about making physics behave in the way you want it ;)
[10:49] <eroomde> but making a technique to braise togther 15km of 4-micron-thick walled tubing into a very complicated heat exchanger without any bloackages is just really really hard
[10:50] <SpeedEvil> But - the engineering is majorly complex. For example, the above involves tracking rocket combustion products in the chamber as they react, tracking dozens of different chemical species.
[10:50] <eroomde> realborg is right - the engineering starts from the assumption that you understand the physics, and now you want to apply it to do something
[10:50] <SpeedEvil> Shockwaves, ...
[10:50] <SpeedEvil> eroomde: hah. I was just trying to work out how to make aluminium twinwall sheet at home.
[10:51] <eroomde> yes, the nature and angle of the shockwaves changes as a function of the molecular mass of all the intermediate species of the combustion, which is fun
[10:51] <gonzo_> but engineering means bringing ALL the physics tovgether, not just the few narrow subjects that you may be trying bto investigate/impliment
[10:52] <day> SpeedEvil: are you building rockets as well... i start to think everyone here builds rockets
[10:52] <eroomde> in a nice happy simple rocket engine world, you make the assumption that you have a completely subsonic combustion chamber in which combustion happens, then a throat with a nice choke, then a supersonic nozzle in which combustion has finished and you can assume frozen equilibrium conditions
[10:52] <eroomde> in reality...
[10:52] <SpeedEvil> day: I want to, but health issues have gotten in the way.
[10:52] <day> :(
[10:52] Action: fsphil made a water rocket once
[10:52] <SpeedEvil> I made a 'black powder' rocket once.
[10:53] <eroomde> day: we welcome anyone who wants to build stuff that goes to high altitudes here :)
[10:53] <SpeedEvil> Fortunately, I diddn't understand how to actually make black powder, which is probably a good thing, I just mixed it.
[10:53] <eroomde> you have to mix is surprisingly a lot
[10:53] <fsphil> sadly it has a nasty crack in it from a bad landing, so will never fly again.. not without duct tape anyway
[10:54] <gonzo_> last water rocket I made, was to entertain the kids on a summer day. Wound up the compressor and got about 50psi into the coke bottle before it broke free
[10:54] <gonzo_> holed two garden fences
[10:54] <SpeedEvil> I am reminded an early falcon 9 which had a crack found in the engine bell extension.
[10:54] <gonzo_> but it ammused the kids
[10:54] <SpeedEvil> Which was rapidly sorted by a pair of shears.
[10:54] <SpeedEvil> (probably not actually shears, but they cut off the very end)
[10:55] <eroomde> i did some water rockets last year
[10:55] <gonzo_> these days I stick to making mortars from robinsons juice bottles, at familiy bbq's
[10:56] <eroomde> also built another toy rocket https://cdn.evbuc.com/eventlogos/1479902/wb2014rocketenginedemonstration.jpg
[10:56] <eroomde> an acrylic hybrid for demoing at talks and stuff (e.g. that was at Wuthering Bytes last year)
[10:56] <eroomde> giving a talk in london on fri where i'll fire it
[10:58] <gonzo_> when the amsat gatertings were at UoS, the peoples from sstl/uni would often do a small firing demo
[10:58] <eroomde> i might try and go to amsat next time
[10:58] <eroomde> when is it usually?
[10:58] <gonzo_> good fun, and being students (of all ages) H&S would be kept to a sensible level
[10:59] <gonzo_> last weekend in june usually ed
[10:59] <gonzo_> I missed last year, had another evenmt on
[10:59] <eroomde> i enjoyed the only one i've been to
[11:00] <craag> amsat-uk ? last weekend in july
[11:00] <eroomde> we did rockets there iirc
[11:00] <eroomde> butane ones
[11:00] <gonzo_> sorry, that was July
[11:00] <gonzo_> http://amsat-uk.org/colloquium/
[11:01] <eroomde> fsphil: ^
[11:01] <gonzo_> they did have it in september one year, as there was the FC sat announcement to make. Which I think would be a better time
[11:02] <gonzo_> ed, was that the pop bottle challenge??
[11:02] <eroomde> yes
[11:02] <gonzo_> that was meths vapour
[11:03] <eroomde> g0mrf
[11:03] <eroomde> i've forgotten his name but i remember his call
[11:03] <RealBorg> has someone tried filling a balloon with knallgas any igniting over a nozzle at altitude?
[11:03] <eroomde> OH GOD, IT'S HAPPENING
[11:03] <craag> TIL ed is a ham
[11:03] <gonzo_> dave... Bowman?
[11:03] <eroomde> can you get chemo to stop the ham spreading?
[11:03] <gonzo_> it's called 'soap'
[11:04] <eroomde> RealBorg: i don't understand the question
[11:04] <eroomde> again?
[11:04] <eroomde> gonzo_: that was it
[11:04] <Geoff-G8DHE_> :)
[11:05] <RealBorg> eroomde, H2 + O2 gas
[11:05] <eroomde> so a balloon filled with h2 + o2?
[11:05] <RealBorg> you ever let small air balloons fly by their exhaust?
[11:05] <eroomde> sure
[11:05] <RealBorg> take that to altitude and ignite the exhaust
[11:06] <RealBorg> not that I expect much but it would be fun
[11:07] <RealBorg> not wasting precious helium and probably even stopping the h2 from escaping the atmosphere
[11:07] <eroomde> so the balloon is just full of h2
[11:07] <eroomde> and you vent it out of the neck through a nozzle and have it mix with the atmospheric air, and you ignite?
[11:08] <RealBorg> I doubt there is enough oygen up there to ignite
[11:08] <eroomde> agreed
[11:08] <eroomde> flame front would disipate fairly quickly
[11:08] <eroomde> you wouldn't get much that could be identified as propulsion, but it might be fun at least
[11:09] <RealBorg> so i propose filling the balloon with the explosive knallgas mixture
[11:09] <SpeedEvil> Laurenceb looked at a solar-powered rocket HAB.
[11:09] <day> knallgas is an english word?
[11:09] <SpeedEvil> But he is quite, quite mad.
[11:09] <eroomde> no
[11:09] <eroomde> never heard of knallgas before
[11:09] <day> well its german
[11:09] <RealBorg> english word is hydrooxygen
[11:09] <SpeedEvil> (actually, the numbers work, it's just engineering)
[11:09] <eroomde> but if you fill the balloon with an explosive mixture and ignite it, it'll just explode everthing
[11:09] <eroomde> no propulsion, just explosion
[11:09] <RealBorg> err, Oxyhydrogen
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[11:11] <day> all this H talk reminds me of this nutjob that came into our office once. he wanted to patent his Hydrogen Oxygen generator. frickn hilarious. That being said that thing was scarily big
[11:11] <RealBorg> if you expel it faster than the shock front it wont ignite the gas in the balloon
[11:11] <eroomde> yes but you can't
[11:11] <eroomde> the upstream pressure would have to be enormous
[11:11] <Laurenceb_> anyone know how to exclude a folder from rsync?
[11:12] <RealBorg> shockfronts tend to travel slower at altitude, right?
[11:12] <eroomde> --exclude=path
[11:12] <eroomde> RealBorg: no
[11:12] <RealBorg> so how much pressure could a elastic balloon provide, how much can you do with a nozzle
[11:12] <eroomde> i think you're confusing a few concepts
[11:13] <eroomde> RealBorg: like nothing
[11:13] <eroomde> explain to me what the nozzle is for
[11:13] <RealBorg> in a storm lighter you often see the flame is starting some mm from the nozzle
[11:14] <eroomde> storm lighters use just fuel
[11:14] <eroomde> they get oxygen from the atmosphere
[11:14] <eroomde> it has to mix first before you get ignition
[11:14] <eroomde> what you're proposing is more like a stick of dynamite
[11:15] <SpeedEvil> In principle, you can add a flame arrestor.
[11:15] <SpeedEvil> A simple mesh will not work in this case likely.
[11:15] <eroomde> in a balloon with a very tiny delta-p, i strong suspect you couldn't get an injector velocity fast enough to protect you
[11:15] <RealBorg> it does, but when the ?platinum? wire does not ignite you see the mixed gas forming a flame some mm from the nozzle
[11:15] <SpeedEvil> A long thin tube may
[11:15] <RealBorg> because it cannot burn fast enough to travel back
[11:15] <eroomde> yes because it has to mix in this scenario
[11:16] <eroomde> it's not comparable
[11:16] <eroomde> stop comparing it
[11:16] <eroomde> you could possibly use a flame arrestor, yes
[11:17] <eroomde> but you'd need some really high feed pressures for any of this to be feasible
[11:18] <eroomde> or at least, a large delta-p across the injector
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[11:25] <Matt_PrjHet> Sorry to talk HAB instead of explosives for a sec :p
[11:25] <Matt_PrjHet> I'm trying to cut the costs & increase practicality on my 2nd launch by using a T instead of an L cylinder.
[11:25] <Matt_PrjHet> Only problem is my payload is heavy and I keep getting a 4m/s ascent rate. How likely is a Hwoyee 1600g not to burst at 4m/s?
[11:26] <eroomde> it's likely to burst
[11:26] <SpeedEvil> In general, not bursting only happens ratther slower
[11:26] <eroomde> with a heavy payload and a decent ascent rate you're fine
[11:26] <SpeedEvil> I don't recall a not-burst at under 1.5m/s or so for any balloon
[11:26] <Matt_PrjHet> I keep getting 'Potential floater' in the calc
[11:26] <day> now knowing that the rocket fuel is rather cheap, it amazes me even more that no hobbyist managed to get a rocket to space and or orbit yet
[11:26] <eroomde> having said all that, i hope you are not assuming that you'll get the entire advertised helium fill from the bottle to the balloon
[11:26] <day> i always assumed its a money issue
[11:26] <SpeedEvil> day: It's a scale problem.
[11:26] <eroomde> i wouldn't go more than 80%
[11:26] <eroomde> and even then
[11:27] <eroomde> day: space is one thing
[11:27] <Matt_PrjHet> I am... and D'oh
[11:27] <daveake> Matt_PrjHet Get an Air Products M20 cylinder instead
[11:27] <eroomde> orbit is a very very very very much harder thing
[11:27] <eroomde> orders of magnitude harder
[11:27] <daveake> N20
[11:27] <SpeedEvil> day: The impulse of a rocket goes with length^3 - due to volume. Drag goes as to length^2 though.
[11:27] <day> is there a certain weight that the rocket has to have to reach orbit?
[11:27] <eroomde> no
[11:27] <eroomde> but there are practical considerations
[11:27] <SpeedEvil> day: It is much, much harder to get to orbit with small rockets, and you will at least need another stage.
[11:27] <eroomde> you like maths?
[11:27] <eroomde> are you sitting comfortably?
[11:27] <eroomde> then we'll begin
[11:27] <daveake> http://www.click4balloons.co.uk/helium-canister-hire-uk-local-collection-871-c.asp
[11:28] Action: day puts on the seatbelt
[11:28] <SpeedEvil> day: For example, for 'normal' rockets, you can (more or less) entirely ignore drag, and thrust at max, only needing to throttle down a bit due to aero loads.
[11:28] <eroomde> there is one equation tonrule them all in rocketry, imaginateively called the rocket equation
[11:28] <daveake> Cheaper than the BOC L but rather more gas than a BOC T
[11:28] <eroomde> it lets you know how much you can increase your velocity by, by ejecting reaction mass
[11:29] <eroomde> the equation itself is:
[11:29] <SpeedEvil> day: For rockets which are smaller than perhaps 500kg, you can't do this, and you need the first stage to accellerate to ~mach 0.8 or so, and cruise slowly up to where the air is thinner before staging.
[11:29] <SpeedEvil> This basically wastes most of your first stage.
[11:29] <eroomde> delta-V = exhaust_velocity * natural_log(start_mass / finished mass)
[11:29] <eroomde> units are m/s
[11:30] <eroomde> so looking at that equation, you have two knobs you can tweak
[11:30] <eroomde> 1) how fast you eject the stuff
[11:30] <SpeedEvil> http://www.ewp.rpi.edu/hartford/~ernesto/S2013/EP/MaterialsforStudents/Lee/Sutton-Biblarz-Rocket_Propulsion_Elements.pdf - if you want to know far, far, far more on this topic.
[11:30] <day> and how good the stuff is
[11:30] <RealBorg> space shuttles rockets even had to throttle down after leaving the atmosphere
[11:30] <eroomde> 2) how big a proportion of your mass you can make fuel - the more the better
[11:30] <day> mass wise
[11:30] <Matt_PrjHet> Wow I just worked out 80% of a T... <1m/s :O
[11:30] <eroomde> so let's plug in some numbers
[11:30] <eroomde> let's say you want to put a small 100kg satellite into low earth orbit
[11:30] <daveake> Yeah don't rely on the cylinder being full
[11:31] <RealBorg> eroomde, what do you think could be the smallest rocket to reack orbit with no payload?
[11:31] <SpeedEvil> Is there a 'sticker pressure' on these cylinders?
[11:31] <eroomde> how much fuel on its own you that need? we're ignoring the mass of rocket straucture and engines at this point
[11:31] <SpeedEvil> RealBorg: It is almost a meaningless question - it depends on assumptions.
[11:32] <SpeedEvil> RealBorg: For multi-stage rockets where you have the first one or two stages dedicated to fighting drag - possibly carryable.
[11:32] <Matt_PrjHet> googling M20 Dave. Actually I was just re-reading your guide to see what I've forgotton and I came across the no sub-5m/s bit!
[11:32] <day> eroomde: but this equation wouldnt work within a gravity field right?
[11:32] <daveake> N20
[11:32] <eroomde> something like liquid oxygen and liquid keroscene, if burnt with 100% efficiency, have an exhaust velocity of about 3500m/s
[11:32] <daveake> typo
[11:32] <eroomde> day: getting there
[11:32] <RealBorg> SpeedEvil, keep it simple and assume single stage
[11:32] <SpeedEvil> RealBorg: many, many tons
[11:32] <Matt_PrjHet> Google N20 :D
[11:32] <eroomde> so how much delta-v do we need for orbit - for LEO the nswer is about 8000m/s
[11:33] <eroomde> but of course you're not starting at 400km in a vacuum, you're starting on the ground
[11:33] <daveake> 4m/s is fine so long as you actually achieve it; as a guide for beginners it's safer to tell them to aim for 5m/s in case they don't fill properly
[11:33] <eroomde> and you have to fight gravity and drag and other stuff just to get to that alt
[11:33] <eroomde> so that adds about another 1500m/s
[11:33] <day> oh. i thought they are already in the 8km/s :D
[11:33] <eroomde> so, very very very roughly, let's say you need about 10000m/s delta-v budget
[11:33] <eroomde> day: nope
[11:34] <daveake> Matt_PrjHet I already googled for you - http://www.click4balloons.co.uk/helium-canister-hire-uk-local-collection-871-c.asp
[11:34] <eroomde> ok so rearrange that equation to get: mass_initial/mass_final = exp(delta_v / exhause_velocity)
[11:35] <day> eroomde: im guessing the exhaust v depends on the fuel you use and can be modified with a nozzle. which in return affects the throughput. Do they use extremely small nozzles in space?
[11:35] <eroomde> = e^(10000/3500) = 18ish
[11:35] <eroomde> day: extremely large infact
[11:35] <eroomde> and yes 3500m/s throughout is a big simplication and it'll be a bit worse than that
[11:35] <eroomde> anyway, that equation says the mass ratio has to be about 18
[11:36] <eroomde> i.e. the propellant must weigh 18* the dry mass of the rocket and payload
[11:36] <RealBorg> that's not so much after all
[11:36] <SpeedEvil> A quarter of the size of rocket, and double the drag.
[11:37] <RealBorg> and this was also a good description of space shuttle's major problem
[11:37] <eroomde> RealBorg: you live in a different universe to everyone else
[11:37] <eroomde> you should talk less
[11:38] <eroomde> so, 18* is actually really hard
[11:38] <day> eroomde: this sounds a lot. but if i scale it down. it doesnt really. 10kg/3.5kg
[11:38] <eroomde> it's very hard to make a rocket with a structural fraction of less than about 0.1
[11:38] <eroomde> whereas this ssto thing needs a structural fraction of about 0.05
[11:38] <eroomde> so consider this 100kg payload
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[11:39] <darsie> hi
[11:39] <eroomde> infact no need, that's neither here nor there
[11:39] <eroomde> consider the strcural fraction
[11:39] <eroomde> you have a rocket combustion chamber
[11:39] <eroomde> it might be several tens of bars in the chamber
[11:39] <eroomde> say 100 to a rough order of magnitude
[11:40] <eroomde> to inject anything in the first place it needs to be fed at a higher pressure, just to go into a vessel at 100bar
[11:40] <eroomde> so you need to feed the fuel at say 150bar
[11:40] <eroomde> now, look around you for something that is at a high pressure in that sort of ballpark
[11:41] <day> so scaling it up makes it easier constructionwise because the volume increases quicker than the circumfence (which demands how much weight im wasting on the housing) ?
[11:41] <eroomde> say a co2 fire extinguisher - that is full of liquid co2 which has a vapour pressure of i think about 60 bar
[11:42] <eroomde> and that probably has about 1-2kg of co2 in it abut maybe 4-5kg of aluminium to contain that pressure
[11:42] <eroomde> in other words the structural fraction is about 2-3
[11:42] <eroomde> and for our rocket we need it to be 0.05
[11:42] <day> that probably equals the safety margins :P
[11:43] <eroomde> so you build the worlds most absurdly power dense pumps so you can store the fuel at much lower pressures, with thinner walls, and then pump them up to the injection pressure
[11:43] <eroomde> and you power them off a little separate rocket engine you build to drive the pump turbine
[11:43] <eroomde> anyway, basically i'm labouring the point, but when you actually try and work through the engineering, building something with a stractural fraction required for ssto is almost impossible difficult
[11:43] <eroomde> if you stage, it gets easier
[11:43] <day> but why do rockets uses bigger nozzles in space? was my thought process earlier fundamentally wrong?
[11:44] <eroomde> but there's still a huge amount of *stuff* required in gubbins and plumbing and so on to reach orbit
[11:44] <eroomde> and that all takes up mass, which means the rocket gets very large very quickly
[11:44] <eroomde> i think this solid thing that failed to get to orbit yesterday is probably about as small as you could go
[11:44] <eroomde> but it's arguable too small
[11:44] <eroomde> nozzles:
[11:44] <day> what thing do you mean?
[11:45] <eroomde> you have a chamber full of high pressure gas, right?
[11:45] <SpeedEvil> The above book - Suttons Rocket Propulsion Elements - is pretty much the seminal work in the area.
[11:45] <eroomde> seminal *introductory* book
[11:45] <eroomde> it's very light on technical details
[11:45] <SpeedEvil> Well - yes.
[11:45] <SpeedEvil> If it was the seminal work, it would be a library
[11:45] <eroomde> well, huzel and huang is very much better if you actually want to make a liquid rocket engine
[11:45] <eroomde> and is about the same size
[11:46] <SpeedEvil> yeah.
[11:46] <eroomde> anyway, day
[11:46] <eroomde> you have a combustion chamber full of very high pressure gas
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[11:46] <eroomde> if you just put a hole in the combustion chamber, the gass will escape in all directions
[11:46] <eroomde> out to the sides and so on
[11:47] <eroomde> for maximum thrust, you want all the gas to escape as fast as possible in just one direcvtion
[11:47] <eroomde> because by conservation of momentum, that means you get the maximum amount of momentum put back, in one direction, into the rocket
[11:48] <SpeedEvil> ed meant: http://www.nasaspaceflight.com/2015/11/super-strypi-spark-inaugural-launch/
[11:48] <eroomde> so, what a nozzle does it it fits over the combustion chamber throat and, in a controlled way, slowly expands the gas (and it accelerates in the process) until it is at the same pressure as the outside ambient pressure, but just going very fast
[11:49] <eroomde> if it's at the same pressure as ambient when it leaves the nozzle mouth, it won't diverge or converge, because the atmosphere won't be pushing or sucking on the exhaust plume, because it's at the same pressure
[11:49] <day> i see so it is essentially like a termination resistor
[11:50] <eroomde> so what that means is that a conventional nozzle is designed to work optimally only at one altitude (or ambient pressure)
[11:50] <eroomde> day: yes
[11:50] <eroomde> and as the ambient pressure drops, the nozzle has to get bigger to expand the gas more to match ambient
[11:50] <SpeedEvil> ' The assembled rocket is 17 metres (55 feet) long, 1.5 metres (5 feet) in diameter and has a total mass at liftoff of 28,240 kilograms (62,260 lb).'
[11:50] <SIbot> In real units: 55 ft = 17 m
[11:50] <SIbot> In real units: 62,260 lbs = 28240.6 kg
[11:50] <eroomde> in a 3 stage rocket, you just size each nozzle to be best about half way up its operating altitudes
[11:50] <eroomde> in space, in theory you need an infinitely large nozzle
[11:51] <eroomde> obviously thats impractical so you just compromise
[11:51] <eroomde> make it as big as possible as a trade off with added mass and volume and so on
[11:51] <SpeedEvil> Also - I note https://en.wikipedia.org/wiki/Black_Arrow - this was a UK launcher which was 18 tons for 135kg of payload to orbit.
[11:52] <Matt_PrjHet> N20 fits the bill perfecty Dave!
[11:52] <eroomde> also the gases cool as the expand but you don't want them expanding/cooling to the point of changing phase (e.g. back to a liquid or solid) because that then is no longer imparting thrust as a pressure force back on the nozzle
[11:52] <darsie> N2O*
[11:52] <eroomde> day: but yes, thinking of a nozzle as an impdeance matcher is a good way of thinking about it
[11:53] <eroomde> for maximum power transfer
[11:53] <eroomde> except momentum in this case
[11:53] <daveake> Matt_PrjHet I much prefer the AP steel culinders to the BOC ones
[11:53] <daveake> You could also look at the new BOC Genie ones
[11:53] <eroomde> in theory the first stage of a Titan 2 rocket could reach orbit if it just launched itself, no payload
[11:54] <eroomde> that might be lighter, i don't know
[11:54] <eroomde> RealBorg: ok, explain please why 'that was the problem with shuttle'
[11:54] <day> but is it possible to use the fuel more efficient by using different nozzles? (aside from the issue you described earlier). My thinking is the following
[11:54] <Matt_PrjHet> Fitting it in the car is the 2nd major concern! I had to borrow my Dad's van last time with the L!
[11:55] <day> can you output the fuel more efficient by increasing its exit velocity with a smaller 'hole'?
[11:55] <gonzo_> I remember the lectures in system dynamics. Trying to explain electronic models in terms of mechanical analolies. But things had come to the point that students have a better feel for the electronics. So having to teah the material backwards, and teach machanis, so that they could then teach it 'forwards' to meet the sylabus!
[11:55] <eroomde> day: i don't quite understand the question
[11:55] <eroomde> fuel = combustion products?
[11:55] <SpeedEvil> day: 'no'
[11:56] <eroomde> hole = throat or nozzle exit?
[11:56] <SpeedEvil> day: For pretty much any interpretation of that question.
[11:56] <day> eroomde: your equation says exit velocity * ln(...)
[11:56] <eroomde> sure, so the maximum exit velocity is achieved by 1) picking the right propellants and 2) matching the nozzle correctly
[11:56] <day> eroomde: throat i guess. it would probably lead to a higher pressure in the chamber
[11:57] <eroomde> there is only one right answer with matching a conventional nozzle
[11:57] <eroomde> ah so you meandecreasing the throat size as you ascend
[11:57] <eroomde> so the nozzle area ration gets bigger
[11:57] <eroomde> so it stays properly matched
[11:57] <eroomde> ?
[11:57] <day> well i was thinking orbit, where you dont need a lot of thrust to overcome gravity
[11:58] <eroomde> yep, you r idea works in orbit
[11:58] <eroomde> in ascent you obviously would reduce thrust this way, which would increase gravity losses
[11:58] <day> yeah
[11:58] <eroomde> but in orbit you generally do have much lower thrust engines
[11:58] <eroomde> so you can get a better area ratio, and so a better exhaust velocity, for less overall mass
[11:58] <day> maximize exit velocity to conserve mass
[11:58] <gonzo_> would reducing thrust as alt increases also keep it matched?? Though I assume you would then run out of thrust at sone stage
[11:59] <eroomde> gonzo_: exactly
[11:59] <eroomde> that's the gravity losses
[11:59] <eroomde> the faster the better while going perpendicaulr to gravity well
[11:59] <day> do modern rockets have a dynamic acceleration flight path? that factors in gravity loss/ friction etc?
[11:59] <eroomde> if you were to perfectly hover a rocket (1:1 thrust) then all of its fuel would be used on gravity loss
[12:00] <eroomde> day: yes
[12:00] <day> wow
[12:00] <eroomde> you optimise the trajector to the design and thrust profile or the rocket
[12:00] <eroomde> it can be quite a non-linear problem to solve
[12:00] <eroomde> you do sometimes want more thrust in space
[12:00] <eroomde> imagine you're going to mars
[12:00] <gonzo_> have any launches used dynamic engine bells, with moving parts, to keep it matched?
[12:00] <eroomde> you need to isert yourself into orbit when you get there
[12:00] <eroomde> gonzo_: ha
[12:00] <eroomde> no comment
[12:01] <eroomde> but consider i'm working on an engine that has to work both at sea level and a vacuum
[12:01] <eroomde> and this is exactly my field
[12:01] <gonzo_> again, theroy vs the engineering
[12:01] <eroomde> ...
[12:01] <eroomde> back to mars
[12:01] <eroomde> lets say you need to perhaps remove 1000m/s to pur yourself in a circular mars orbit
[12:02] <eroomde> ideally you would burn all of that when you arrive at mars perfectly at a tangent
[12:02] <eroomde> i.e. drop 1000m/s all at once and suddenly find yourself in a circular orbit
[12:02] Action: russss is enjoying this week's Rocket Science Hour with eroomde
[12:02] <eroomde> in reality, no one has made a direc delta-function engine yet
[12:02] <eroomde> so you actually have to burn for a while
[12:03] <day> it might be a bit uncomfortable as well
[12:03] <eroomde> and all the burn that is occuring at a point that isn't perfectly tangential will be subject to gravity losses
[12:03] <eroomde> so you end up using more fuel that you would ideally want to
[12:03] <eroomde> but the thrustier your engine the better, still, from that point of view
[12:03] <eroomde> so there are some bigger space thrusters being flown on missions nowadays
[12:04] <eroomde> as it means more fuel left over to use once you're doing operational stuff in orbit
[12:04] <eroomde> modulo the added weight of a bigger engine - again it's all nitty gritty engineering trade-offs rather that something with an obviously right answer
[12:05] <eroomde> gonzo_: i was a bit obtuse earlier but yes there is research into altitude compensating nozzles
[12:05] <day> is there any rocketfuel research going on? or is the rocketfuel today as good as it gets?
[12:05] <eroomde> that's what i've been working on this year
[12:05] <eroomde> day: yeah pretty much
[12:05] <day> :(
[12:06] <eroomde> hydrogen and oxygen is about as good as it gets for exhaust velocity
[12:06] <eroomde> unless you doing really really pathological things tat you would never want to do
[12:06] <SpeedEvil> day: 'as good as it gets' always has wrinkles. H2/O2 is 'as good as it gets' - but sucks operationally in many ways.
[12:06] <eroomde> yes exactly
[12:06] <SpeedEvil> (hydrogen is very, very undense and has a really low temperature)
[12:06] <eroomde> h2+o2 is better performing than keroscene+o2
[12:06] <eroomde> but hydrogen is 1/7th less dense than kero
[12:07] <eroomde> so for a given delta-v you need a tank with 7 times the volume for h2 than kero
[12:07] <eroomde> = more weight
[12:07] <eroomde> not to mention that cryo tanks have a higher minimum structural fraction than kero
[12:07] <eroomde> the best kero tanks are like stainless steel bladders that have to be kept under pressure to stay stracturallt rigid
[12:07] <eroomde> some icbms use that kind of tank
[12:08] <eroomde> kero tanks can get to about 1% stractural fraction, LH2 maybe 10%
[12:08] <eroomde> so yes, trade-offs
[12:08] <eroomde> but at bigger scales the advantages of h2 increase
[12:08] <eroomde> cube-square law etc
[12:08] <eroomde> the really pathological stuff is things like liquid lithium+liquid flourine
[12:08] <Darkside> wat
[12:08] <SpeedEvil> I wish liquid ozone was a thing.
[12:08] <eroomde> with a lot of extra hydrogen thrown in to be accelerated by all the heat produced
[12:08] <day> ive seen a docu about solid rocketfuel and submarines a while ago, it was quite interesting
[12:08] <Darkside> has someone actually done that
[12:09] <eroomde> Darkside: not for an operational rocket
[12:09] <Darkside> that sounds insanely dangerous
[12:09] <eroomde> but ground tests yes
[12:09] <eroomde> yes it is
[12:09] <day> they used something based on aluminium iirc
[12:09] <SpeedEvil> Darkside: Pretty much all of the 'insane' propellants have been tried.
[12:09] <Darkside> eroomde: what woul dbe the byproducts of that?
[12:09] <eroomde> there are other insanely dangerous oxidisers like ClF3
[12:09] <adamgreig> lol ClF3
[12:09] <russss> nope
[12:09] <adamgreig> is that The Most Insane?
[12:09] <SpeedEvil> Darkside: http://www.amazon.co.uk/Ignition-Informal-History-Liquid-Propellants/dp/0813507251
[12:09] <eroomde> which will combust with stainless steel, asbestos, concrete, sand, and rocket test engineers
[12:10] <Darkside> i thought that was ClF4
[12:10] <eroomde> if you have a bend in your plumbing, the ClF3 will just keep on going in a straight line
[12:10] <adamgreig> https://en.wikipedia.org/wiki/Chlorine_trifluoride Darkside
[12:10] <Darkside> ah
[12:10] <Darkside> i thought it was tetraflouride
[12:10] <eroomde> it's horrifying and no one has used it
[12:10] <russss> ClF4 is the ion I think
[12:10] <eroomde> in anger
[12:10] <adamgreig> "Solubility in water: Reacts violently"
[12:10] <day> i think that was the propellant they were using Polyurethane-bound aluminum-APCP
[12:10] <russss> ClF3 has no right to exist.
[12:10] <mattbrejza> still not as bad as F2O2
[12:10] <adamgreig> "Solubility: reacts violently"
[12:10] <SpeedEvil> Ozone is arguably more fun than CLF3
[12:11] <SpeedEvil> ClF3 will not actually high-order detonate if you get the tank wrong.
[12:11] <SpeedEvil> Or look at it.
[12:11] <eroomde> yes that wiki article includes a quote from "Ignition!" with SpeedEvil mentioned
[12:11] <Darkside> http://blogs.sciencemag.org/pipeline/archives/2008/02/26/sand_wont_save_you_this_time
[12:11] <Darkside> that's the article i remember
[12:12] <Darkside> 1 Used from £1,461.39
[12:12] <Darkside> lol nope
[12:12] <eroomde> i have the pdf
[12:12] <eroomde> it's a great read
[12:13] <eroomde> probably the best written informal scientific book i've ever read
[12:13] <SpeedEvil> https://en.wikipedia.org/wiki/Green_Propellant_Infusion_Mission
[12:13] <eroomde> infact the writing is so good that the forward is written by a giuy who admired his writing
[12:13] <eroomde> a certain I. Asimov.
[12:13] <SpeedEvil> Is an example of 'modern' propellants.
[12:13] <day> C1F is crazy :O. you can ignite glas just by spraying it onto it?
[12:14] <SpeedEvil> They are not designed for flat-out performance, but for overall highest system performance - which very much isn't the same thing.
[12:14] <SpeedEvil> It is relatively safe - even though the formula does contain OHNO
[12:14] <eroomde> https://www.dropbox.com/s/4taobs1w31q0u2f/ignition.pdf?dl=0
[12:14] <eroomde> ignition.pdf ^
[12:14] <eroomde> download it
[12:14] <Darkside> will do
[12:15] <adamgreig> http://web.archive.org/web/20060318221608/http://www.airproducts.com/nr/rdonlyres/8479ed55-2170-4651-a3d4-223b2957a9f3/0/safetygram39.pdf
[12:15] <eroomde> but yes, lithium+flourine+h2 is the best performing combo tested
[12:15] <adamgreig> air products safetygram for ClF3
[12:15] <eroomde> because therodynamics (i'm not going to try and explain it over ascii), it makes sense to have excess hydrogen
[12:15] <eroomde> for more thrust
[12:15] <eroomde> so you might think the best ratio of o2+h2 in a rocket engine is stoichiometric
[12:16] <eroomde> but actually no, you get more thrust if you go fuel rich
[12:16] <eroomde> i.e. excess hydrogen
[12:16] <eroomde> it boils down to its heat capacity and molecular mass meaning it gets accelerated to a higher pseed than the rest of the combustion products, for a given temperature
[12:17] <adamgreig> "a very useful chemical in operations requiring a high-energy fluorinating agent"
[12:17] <eroomde> and given momentum is just mass+v, higher v is better
[12:17] <adamgreig> "the compound represents one of the highest-reactivity products that Air Products currently manufactures"
[12:17] <eroomde> mass*v*
[12:17] <russss> adamgreig: I think I've seen that PDF before but I missed the images "Vapor and Liquid Release on Raw Chicken"
[12:17] <eroomde> nuclear rockets infact were just a fission reaction dumping heat into h2, which was then accelerated through a nozzle
[12:18] <eroomde> that gave almost an order of magnitude better exhaust velocity
[12:18] <eroomde> but flying fission reactors on experimental rockets was considered a bit sporting
[12:18] <adamgreig> not even the silliest nuclear rocket though huh
[12:19] <SpeedEvil> Even more exciting today is fission fragment rockets.
[12:19] <adamgreig> https://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29
[12:19] <adamgreig> " Early versions of this vehicle were proposed to take off from the ground with significant associated nuclear fallout"
[12:19] <SpeedEvil> Uranium dust becomes highly charged as it decays.
[12:19] <SpeedEvil> You contain the charged dust electrostatically.
[12:19] <eroomde> day: ion engines have an arder of magntiude better exhaust velocity than chemical
[12:19] <eroomde> but piss all thrust
[12:20] <eroomde> so they're used in space applications
[12:20] <SpeedEvil> You then direct the emitted fission fragments (which are going at a sizable fraction of c) out magnetically
[12:20] <eroomde> but useless for launchers
[12:20] <SpeedEvil> https://en.wikipedia.org/wiki/Fission-fragment_rocket#Research
[12:20] <eroomde> and if you're a l00n from the internet, you can start talking about how EM drive is the future
[12:20] <SpeedEvil> Low thrust, but it can get you to rendevous with pluto in a year.
[12:20] <adamgreig> "[the steel container wall] split while it was being maneuvered onto a dolly, instantaneously releasing 907kg of cold ClF3 liquid onto the building floor"
[12:20] Action: eroomde aways realborg patiently
[12:20] <adamgreig> ah yes
[12:20] <eroomde> awaits*
[12:20] <eroomde> adamgreig: i like the rest of that paragraph
[12:21] <eroomde> about the technician's failure mode
[12:21] <eroomde> Miraculously, nobody was killed, but there was one casualty  the man who had been steadying the cylinder when it split. He was found some five hundred feet away, where he had reached Mach 2 and was still picking up speed when he was stopped by a heart attack.
[12:22] <adamgreig> but he wasn't killed?!
[12:22] <eroomde> (this is such a good book, i re-iterate that everyone should have a read)
[12:22] <eroomde> no, he just ran for his life
[12:22] <adamgreig> o lol
[12:23] <eroomde> "This episode was still in the future when the rocket people started working with CTF, but they nevertheless knew enough to be scared to death, and proceeded with a degree of caution appropriate to den- tal work on a king cobra. And they never had any reason to regret that caution. The stuff consistently lived up to its reputation."
[12:25] <Sirius-BE> If someone needs it in a word format... i scanned it and OCR it and edited it ... because is one of the best booke ever written in that field
[12:25] <day> eroomde: are you actively following the EM Drive 'drama'?
[12:26] <eroomde> no
[12:27] <eroomde> not in the least
[12:27] <day> why not? isn't that kind of groundbreaking?
[12:27] <eroomde> sure, but in the same way that going faster than light and quantum computers would be groundbraking
[12:28] <eroomde> even if you can show it's possible, you're still absurdly far away from using it in a practical, useful way
[12:28] <eroomde> it's basically irrelevent to my job and life
[12:29] <day> i see.
[12:29] <eroomde> but if someone can conclusively show a real effect for the reasons they think then i'll of course be curious
[12:30] <eroomde> but not conserving momentum is such a bold claim that i think you can ignore almost all the noise about it until lots of very respectable institutions have independently verified any claim
[12:30] <eroomde> a bit like the faster than light neutrino stuff a couple of years ago
[12:31] <day> :)
[12:31] <eroomde> the scope of subtle experimental error seems, to me, about 10^6 times more likely to explain any weird results than actually breaking conservation of momentum
[12:31] <adamgreig> the level of things they're having to try and account for as well
[12:31] <adamgreig> it's about a million things to try and hold constant
[12:32] <adamgreig> might as well just build a 10MW version that develops enough thrust to levitate, no one would argue with that :P
[12:32] <SpeedEvil> Some of the claims being made early on would for example result in being able to have a 150MPH motorbike, with an EMdrive, and a generator run from the wheels, and have it perpetual motion
[12:33] <SpeedEvil> As power = velocity * force, and if force is indepenatnt of speed, and proportional to electrical power input, there is a speed at which one exceeds the other.
[12:33] <gonzo_> nis this explainable in the use of boltzmann constant, in relation to the press/media
[12:35] <gonzo_> ed, I did wonder from your previous comment (dynamic engine bells) of that was something you m,ay not be allowd to talk about
[12:36] <gonzo_> but that tutorial, would make a great amsat talk!
[12:37] <SpeedEvil> gonzo_: you do know of aerospikes?
[12:38] <gonzo_> nope. Are they gypo's that steal the wheels off your plane when it's parked on the apron?
[12:39] <SpeedEvil> no
[12:39] <SpeedEvil> They invert the nozzle into a spike, and the propellant flow expands magically
[12:39] <SpeedEvil> As if it was in a nozzle-sort-of
[12:41] <gonzo_> googled. Interesting
[12:41] <gonzo_> there is nothing new under the sun!
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[12:53] <Laurenceb> holy scrollback batman
[12:58] <eroomde> gonzo_: i can't really talk about it, no
[12:58] <eroomde> well, i can generally
[12:58] <eroomde> not specifically what we're doing tho
[12:59] <gonzo_> a generic tutorial on rocket theory would be a good talk though.......... Hint
[13:00] <day> eroomde: is this project in any way secret? it looks like it is governmental funded, and basically everyone already has seen key information (usa, esa)
[13:00] <SpeedEvil> http://www.gizmag.com/bae-reaction-hypersonic-engine/40169/
[13:00] <SpeedEvil> 'seen' does not mean 'is free to release'. I am very sure NDAs will have been involved.
[13:01] <SpeedEvil> Nor does government funded generally mean you can get engineering diagrams.
[13:02] <day> SpeedEvil: according to wiki the usa already made evaluations, so likely a bit more than diagrams
[13:02] <SpeedEvil> I mean 'you' as in a member of the public.
[13:02] <eroomde> day: there's a publically available patent
[13:02] <day> well me has no use for this information anyways
[13:02] <eroomde> that's the single most technical document that is publically available
[13:03] <SpeedEvil> And yes - the patent is quite interesting
[13:03] <eroomde> whether or not it's still representative of the state of the art is another question
[13:03] <SpeedEvil> I wish I understood it.
[13:03] <BeaverOne> SpeedEvil Laurenceb: http://www.ams.org/journals/ert/2015-19-11/S1088-4165-2015-00470-4/S1088-4165-2015-00470-4.pdf
[13:04] <SpeedEvil> wut?
[13:04] <BeaverOne> it's a theorem
[13:04] <SpacenearUS> New vehicle on the map: 03ZS6ACT _chase - 12http://tracker.habhub.org/#!qm=All&q=ZS6ACT%20_chase
[13:05] <SpeedEvil> BeaverOne: well - yes - why are you posting it.
[13:05] <SpeedEvil> If you wish me to read it, first paypal 100K.
[13:05] <BeaverOne> thought perhaps it'd be a good stimulation and interest for your mind
[13:06] <SpeedEvil> I need less stimulation, not more.
[13:06] <BeaverOne> :( c'mon
[13:06] <chris_99> Laurenceb, get to the bottom of the loadcell/inst. amp issue?
[13:09] <eroomde> Laurenceb: http://i.imgur.com/9ZH5Kyq.png
[13:09] <eroomde> this is about full scale right?
[13:09] <adamgreig> not even close apparently
[13:09] <adamgreig> tens of grams mass, 5kg is full scale
[13:10] <eroomde> units would be helpful
[13:16] <Laurenceb> oh hi there
[13:16] <Laurenceb> lol
[13:16] <Laurenceb> yeah I'm busy with work, I suspect the REF input is being weird
[13:16] Action: Laurenceb is watching http://spaceflightnow.com/2015/11/03/ors-4-mission-status-center/
[13:16] <Laurenceb> looks perfect to me, but no stage 2 ignition?
[13:17] <Laurenceb> heh sorry about units, thats ~60grams placed on the load cell
[13:17] <Laurenceb> ok 2 work
[13:19] <Laurenceb> if I can fix it I might be ready to do a full test thins evening
[13:19] <Laurenceb> proper supercap ignition system firing a Klima on a load cell
[13:20] <SpeedEvil> :)
[13:20] <chris_99> cool
[13:21] Action: RealBorg is back from flying his plank
[13:21] <RealBorg> eroomde, the shuttle had a lot of weight they had to accelerate
[13:22] <RealBorg> wasting lots of fuel for something that is not even close to a commercial plane
[13:22] <eroomde> it had a mass ratio of 16. pretty normal. it was big tho, sure
[13:22] <eroomde> but not specially big for people + large payloads
[13:22] <eroomde> of course, the requirement to launch people just to launch satellites was the stupid bit
[13:24] <Laurenceb> also all the wings and stuff
[13:24] <Laurenceb> I really dont see what they achieved
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[13:24] <RealBorg> it didn't have a particularly large payload compared to the saturn v
[13:25] <RealBorg> Laurenceb, they commited to a reusable space glider then cut the budget
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[13:26] <Laurenceb> only the wings added no value
[13:26] <RealBorg> no, they could have made it a lifting body / flying wing
[13:27] <SpeedEvil> Hypersonic aerodymanics was poorly understood at the time.
[13:27] <eroomde> i don't think it's hugely better understood at the time
[13:27] <SpeedEvil> The first flight almost became unstable.
[13:27] <eroomde> and i don't think the shuttle was constrained by not understanding hypersonics
[13:28] <SpeedEvil> The first flight avoided an accident due to chance due to not understanding hypersonics.
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[13:28] <day> hypersonic wing design is interesting
[13:29] <day> its interesting how different they look
[13:29] <RealBorg> sr71, x33 projects, both cancelled
[13:29] <eroomde> illuminati?
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[13:30] <day> cant be because a sr71 is an expensive useless piece of history
[13:30] <RealBorg> they were scientists of their time - i don't think they would have cancelled it
[13:30] <Laurenceb> illuminati confirmed
[13:30] <day> ^
[13:31] <day> was it canceled under bushs administration?
[13:31] <Laurenceb> maybe he wanted to make peace with the fishes
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[13:33] <RealBorg> x33 was canncelled under bush jr.
[13:33] <day> 2001
[13:35] <eroomde> next time you think your day isn't going well: https://upload.wikimedia.org/wikipedia/commons/4/43/NOAA-N'_accident.jpg
[13:36] <RealBorg> what happened there?
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[13:36] <eroomde> technician forgot to do the bolts to the base
[13:36] <eroomde> he might have got fired
[13:37] <gonzo_> not something that you would want to out on your CV
[13:37] <daveake> "Made a mistake that cost $135M"
[13:37] <adamgreig> "but, will never ever forget to do up your bolts"
[13:38] <gonzo_> poss miss off that period in your enployment and just blag that you were contracting
[13:38] <x-f> bolts were temporarily removed for another project, iirc
[13:38] <daveake> 2 mistakes apparently - one guy removed them but didn't document it; another guy failed to check despite the procedure saying he should
[13:39] <gonzo_> and manager who harrangued the tech 1 into robbing the bolts for expiediency, prob still there
[13:39] <daveake> Presumably both of them quickly made a bolt to the job center
[13:39] <adamgreig> idk, nasa loves blaming the managers to
[13:39] <gonzo_> sorry, I am not geing to get into aniother pun thread
[13:40] <adamgreig> too
[13:41] <gonzo_> what is my wit-worth?
[13:45] <SpeedEvil> Depends if you got it on taper.
[13:45] <gonzo_> ISO wish I hadn't said that......
[13:46] <eroomde> enough
[13:46] <gonzo_> Sorry ed, did you say UNF??
[13:47] <eroomde> no
[13:49] <chris_99> Laurenceb, just wondering with the silabs chip, did you use a 30MHz xtal, i'm wondering, could you program any frequency between 1421050 MHz ?
[13:52] <Laurenceb> no, I used ...
[13:52] <Laurenceb> cant remeber lol
[13:52] <Laurenceb> 27mhz maybe
[13:52] <Laurenceb> and a TCXO
[13:54] <chris_99> ah heh, but with that, could you program a large range of frequencies do you know, as i'm a tad confused with the module i ordered ( http://www.aliexpress.com/item/2pcs-lot-Upgrade-version-RF4463F30-1W-FSK-GFSK-Si4463-small-size-3km-high-power-long-range/2008837242.html ) seems to only have a freq. range of 410-450MHz, just wondering if you might know why that is
[13:54] <adamgreig> the chip can output whatever frequency
[13:54] <Laurenceb> I'm also confused
[13:54] <adamgreig> but the passives making the matching network and filters will likely be matched to one frequency
[13:54] <Laurenceb> the input frequency does not influence range of outputs
[13:54] <adamgreig> the crystal frequency is irrelevant
[13:54] <adamgreig> the issue is that the hardware design after the board involves filters with a specific frequency band
[13:54] <chris_99> oh you mean the inductors etc. on the antenna adamgreig ?
[13:55] <Laurenceb> yes
[13:55] <adamgreig> the inductors and capacitors between the antenna and the module
[13:55] <chris_99> ah ok that makes sense
[13:55] <chris_99> ta
[13:56] <chris_99> so the other thing i was wondering, 433MHz is usable only to 10mW i think?
[14:00] <pb0ahx_> !flights
[14:00] <SpacenearUS> 03pb0ahx_: Current flights: 03BENNY_1 10(304f)
[14:01] <pb0ahx_> !dial 304f
[14:01] <SpacenearUS> 03pb0ahx_: Latest dials for 03BENNY_1 10(304f): 031 MHz
[14:01] <pb0ahx_> BENNY_1 is not yet flying ???
[14:01] <Laurenceb> so someone just ordered a heart rate monitor for racehorses
[14:01] <Laurenceb> lulz
[14:02] <daveake> pb0ahx_ Delayed till next Wednesday
[14:02] <daveake> this was in the mailing list this morning
[14:02] <pb0ahx_> daveake, tnx info i chekt not yet mail hihihi
[14:02] <chris_99> heh, while it's running Laurenceb ?
[14:02] <Laurenceb> yes
[14:02] <Laurenceb> this is going to be a nutty project
[14:03] <chris_99> is it wireless?
[14:03] <Laurenceb> no, µSD logging
[14:03] <chris_99> aha
[14:03] <chris_99> so doing a bit of reading, i guess i can use 446MHz @ 500mW, as data does seem permissable
[14:04] <Laurenceb> I havent heard that one before
[14:04] <adamgreig> isn't that PMR
[14:05] <eroomde> yes it is
[14:05] <adamgreig> don't think that's ok for data
[14:05] <eroomde> you won't be using in airborne chris_99
[14:05] <chris_99> no i wont
[14:05] <eroomde> but you migt not be intending to - haven't been following
[14:05] <chris_99> if i launch in air ill use 10mW
[14:05] <adamgreig> not on 446MHz either
[14:06] <chris_99> yeah 434 or something isn't it
[14:06] <eroomde> yes
[14:06] <eroomde> if it's not in that table of frequencies, powers, bandwidths, and explicitly allowable airborne, you're stuffed
[14:08] <adamgreig> PMR446 is voice-only last I understood it
[14:08] <chris_99> from an ofcom datasheet 'Additionally, Digital PMR446 facilitates the transmission of data, and has an automatic transmission'
[14:08] <adamgreig> but the new digital pmr446 regs that are being harmonised might change that somewhat
[14:14] <day> adamgreig: you mentioned the L C filter between the output and the antenna earlier. Do you know where to find infos on how to calculate the components? I stumbled across it in a datasheet as well(likely the same datasheet you were writing about)
[14:16] <day> i assume its goal is to attenuate everything outside of the wanted frequency band?
[14:16] <adamgreig> it's a bit more complicated than just a filter
[14:16] <adamgreig> it has to also impedance match the PA to the antenna
[14:16] <eroomde> day speakes impdance matching, we've established
[14:17] <adamgreig> and it usually must interact with the PA to produce an actual output signal
[14:17] <adamgreig> the high efficiency PAs on these things are typically weird things
[14:18] <adamgreig> specifically you can choose whether to drive it as a switched current drive, class E amp, or on/off switched square wave sort of thing
[14:18] <adamgreig> if you have switched current you need to have an output stage that converts the current to a voltage or otherwise matches it
[14:18] <adamgreig> class e needs a resonance to drive at the output
[14:18] <adamgreig> and stuff
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[14:19] <day> adamgreig: does the filter depend on the antenna as well?
[14:19] <adamgreig> look at silabs app note AN693
[14:19] <adamgreig> in general no
[14:19] <adamgreig> assuming the antenna is on-frequency and matched for 50R
[14:19] <adamgreig> the matching components on the output will match to a 50R transmission line typically
[14:19] <day> then why doesnt the manufacturer simply provide a guideline
[14:20] <adamgreig> but like, you could use a 100R antenna and match to that, whatever
[14:20] <adamgreig> they do
[14:20] <adamgreig> see AN693
[14:20] <adamgreig> it's just a complicated guideline because it's a complicated subject
[14:20] <adamgreig> and depends on which one of those drive modes you want, which depends on what engineering tradeoffs you want to make
[14:20] <adamgreig> power efficiency vs total output power vs duty cycle vs spectral content vs etc etc
[14:20] <adamgreig> some setups are cheaper in terms of number or quality of external parts required too
[14:21] <day> i was looking at the transmitter that the PAVA uses (upu posted it a while back)
[14:21] <adamgreig> all the usual things what engineers do
[14:21] <Laurenceb> heh silabs matching
[14:21] <Laurenceb> I've never developed it further than the datasheet design
[14:21] <adamgreig> it's a bit of a pig
[14:21] <Laurenceb> Leo remodelled it all in spice and did a ton of analysis
[14:21] <Laurenceb> dunno if it gained him much, he thought 1 or 2 dB
[14:21] <day> an SI4060
[14:22] <adamgreig> yea well he needed something that'd do 434 and 144 at the same time etc
[14:22] <Laurenceb> yup
[14:22] <adamgreig> same app note is relevant day
[14:22] <Laurenceb> choice of inductors seems to be quite critical
[14:22] <adamgreig> yea
[14:22] <Laurenceb> and Murata inductors seem to beat all the competition
[14:22] <adamgreig> there are a lot of questions about wirewound vs thin film vs thick film vs whatever
[14:22] <Laurenceb> at least last time I looked
[14:22] <Laurenceb> yeah I've used wirewound
[14:22] <adamgreig> "beat" depends on your metric
[14:23] <Laurenceb> heh
[14:23] <adamgreig> wirewound are expensive and fiddly
[14:23] <Laurenceb> shrug
[14:23] <adamgreig> usually "works fine" with chip inductors and stuff
[14:23] <Laurenceb> this isnt mass production
[14:23] <Laurenceb> expensive and fiddly is acceptable
[14:23] <adamgreig> yea
[14:23] <adamgreig> I ended up using a different network for 868 and 434 to simplify matters but it's still a pain
[14:24] <Laurenceb> yeah that was Leos problem
[14:24] <adamgreig> I assume richardeoin has put some thought into this matter too
[14:24] <Laurenceb> ah yeah
[14:24] <adamgreig> see if you can spot which one is 434 https://www.flickr.com/photos/randomskk/20118348235/in/album-72157653850703723/
[14:25] <Laurenceb> that ublox footprint is nasty
[14:25] <adamgreig> takes a little longer to design but seems to work well
[14:25] <Laurenceb> nice
[14:25] <Laurenceb> presumably lighter too?
[14:25] <adamgreig> less solder yea
[14:26] <Laurenceb> middle is 434?
[14:26] <adamgreig> it's the same geometry ublox use
[14:26] <adamgreig> correct, you win
[14:26] <Laurenceb> heh
[14:26] <Laurenceb> still dont know what I'm looking at
[14:26] <Laurenceb> whats the big IC in the middle?
[14:26] <adamgreig> the radio
[14:26] <Laurenceb> oh yeah lol
[14:26] <Laurenceb> I have some on my desk doh
[14:26] <adamgreig> lol
[14:27] <Laurenceb> micro is on the other side?
[14:27] <adamgreig> not exactly
[14:27] <jcoxon> adamgreig, the horror, the horror
[14:27] <adamgreig> https://www.flickr.com/photos/randomskk/19896760151
[14:27] <Laurenceb> oh its a module
[14:27] <Laurenceb> nice
[14:28] <adamgreig> can't decide whether I'll enjoy pursuing the r2 hardware (much smaller) or redoing the firmware for this one in assembly though
[14:28] <adamgreig> think the latter will be more educational for now
[14:29] <Laurenceb> huh where does the firmware run?
[14:30] <adamgreig> on the microcontroller
[14:30] <adamgreig> usual place really
[14:30] <Laurenceb> this is another board?
[14:30] <Laurenceb> sorry I'll shut up lol
[14:30] <Laurenceb> slow day
[14:31] <adamgreig> god the pogo pins on this thing though
[14:31] <adamgreig> would rather just do r2 to get rid of those
[14:31] <adamgreig> programming is such a faff
[14:31] <eroomde> pssst Laurenceb https://www.silabs.com/Support%20Documents/TechnicalDocs/Si106x-8x.pdf
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[14:33] <Laurenceb> oh its one of those
[14:33] <Laurenceb> eek 8051
[14:34] <Laurenceb> guess silabs 8051 is quite nice
[14:34] <adamgreig> surprisingly ok
[14:34] <adamgreig> single cycle for everything, no microcode, down to 10nA sleepy sleep
[14:34] <Laurenceb> nice
[14:34] <Laurenceb> Rx sensitivity looks good too
[14:34] <adamgreig> better pin allocation to peripherals than an stm32 as well
[14:35] <adamgreig> though really sodding confusing
[14:35] <Laurenceb> heh it might work for rockoon tracker
[14:35] <Laurenceb> if you could bounce packets off it then there is no need for multiple ground stations
[14:35] <Laurenceb> not sure if i'd trust that
[14:39] <Laurenceb> if you like asm, thumb 2 is very nice
[14:39] <adamgreig> i surely know it
[14:39] <adamgreig> super nice
[14:39] <eroomde> i read that with a midwest accent
[14:39] <eroomde> 'yes maam, i surely know it'
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[14:45] <TIBS01> lazy
[14:45] <TIBS01> u must be close to me
[14:45] <TIBS01> if your near the m25
[14:46] <TIBS01> 12th June 2002
[14:46] <TIBS01> GC6397 - Roaring Down
[14:46] <TIBS01> I use the road that runs along the top of North Downs as a way of avoiding the M25 some days on my way to work. Recently I stopped to see whether there was anywhere a cache could be hidden, and found this place. View cache page.
[14:46] <TIBS01> =
[14:46] <LazyLeopard> South-east London, yes.
[14:46] <TIBS01> where kent ?
[14:47] <LazyLeopard> Orpington
[14:47] <TIBS01> ahhh
[14:47] <TIBS01> u ham licensed ?
[14:47] <LazyLeopard> Yep
[14:47] <TIBS01> u must know me then
[14:47] <TIBS01> 2e0sgg
[14:48] <TIBS01> and tony g1hig
[14:48] <TIBS01> who runs gb7ok and gb7lo
[14:48] <LazyLeopard> Been known to SOTA on G/SE-005 Botley Hill
[14:48] <TIBS01> ahhh
[14:48] <TIBS01> u prob spoke to me then
[14:48] <TIBS01> im in the medway towns
[14:49] <TIBS01> ill bbiAB I goto pick up me son from school
[14:52] <Matt_PrjHet> Hey Adam, who's a good person to speak to about getting permission to film a launch at Churchill?
[14:52] <Matt_PrjHet> Is it someone in the CUSF or shall I arrange it direct with the college?
[14:53] <eroomde> cusf. definitely not the college
[14:53] <eroomde> ping adamgreig so his nick highlights
[14:54] <adamgreig> hey yea
[14:54] <Matt_PrjHet> I'm a n00b at IRC. DO I just write or is it an @
[14:54] <adamgreig> film as in media crew?
[14:55] <Matt_PrjHet> Yeah, well, one freelancer with his camera.
[14:57] <adamgreig> thought i heard something about discovery channel, film crew, etc
[14:57] <adamgreig> i mean, definitely the person to contact is contact@cusf.co.uk which goes to me among other people
[14:57] <gonzo_> just write the nick
[14:57] <adamgreig> your email from 25th is in my inbox, shamefully
[14:58] <Matt_PrjHet> Yeah, after our X-Wing vid, Discovery (Daily Planet) got in touch and wanted to know if we had another launch planned for an insert on their daily science show. THey're doing a Star Wars special.
[14:58] <adamgreig> basically sorting commercial film crews involves a chunk more people to contact and get permission from but we have to do that, not you
[14:58] <adamgreig> have been putting off thinking about it for a bit as been busy and the predictions are all shit :P
[14:59] <Matt_PrjHet> tbh when they called I was like "Pshh, Yeah! Of course we've got another launch planned!" #Fibbing Been fairly busy getting it all ready myself!
[15:00] <adamgreig> in principle there's no problem, we just need to get permission from higher up people for launches involving external media companies and stuff
[15:00] <adamgreig> usually granted without issue
[15:00] <Matt_PrjHet> They're shooting us playing with models Friday, then they're keeping a freelancer on standby for a couple of weeks while we check the weather every day...
[15:01] <Matt_PrjHet> Sure, I totally understand. Is there anything I can do to help?
[15:02] <adamgreig> not especially. we need probably around 5 days notice which complicates predictions, and will need to know how many people in total
[15:02] <adamgreig> uhm otherwise maybe I would suggest picking some likely dates and emailing us :P
[15:03] <Matt_PrjHet> Ha ha... Email you then bug you on IRC ;)
[15:03] <adamgreig> yea for sure
[15:03] <adamgreig> there are other people who in theory might also deign to reply to those emails which makes my life easier :P
[15:03] <Matt_PrjHet> Yep I can do that.
[15:03] <adamgreig> whereas if you email just me or bug just me it's only me who can help :P
[15:06] <Matt_PrjHet> 5 days is probably good. I've stuck a request for a NOTAM in launching out of Oxford towards the end of the month (theory being, more chance of landing back in the UK.) If I can get a Cambridge launch before that, then all the better. But I guess, in theory I'll have a idea T minus 7...
[15:07] <eroomde> where in Oxford?
[15:07] <Matt_PrjHet> Wallingford
[15:07] <Matt_PrjHet> Brightwell Vineyard
[15:07] Nick change: fl_0 -> fl_0|afk
[15:08] <eroomde> oh
[15:09] <eroomde> i lived in britwell salome a few years ago
[15:09] <eroomde> central ox now
[15:11] <Matt_PrjHet> Ah, just down the road! It's a friend of mine's Vineyard. I said, as thanks for letting us launch from there I'd stick thier logo on the side of the payload and snap it with our Pi cam :)
[15:11] <Matt_PrjHet> 12.% SSDV
[15:11] <eroomde> have you got permission yet?
[15:11] <eroomde> i'd have thought benson might be problematic
[15:12] <Matt_PrjHet> I haven't heard otherwise... It's my first NOTAM. I launched from Churchill before.
[15:13] <eroomde> if you've not heard anything back yet i wouldn;t take that as a sign that it's ok
[15:13] <eroomde> quite possible to get rejections 2 days before
[15:13] <eroomde> fingers crossed
[15:13] <Matt_PrjHet> Oh really?
[15:13] <eroomde> yes really
[15:13] <Matt_PrjHet> A***
[15:14] <Matt_PrjHet> That's a bit rubbish...
[15:14] <Laurenceb> ok strain gauge works
[15:14] <Laurenceb> it was the ref input to the inst amp
[15:14] <adamgreig> causing the slow response?
[15:14] <adamgreig> weird
[15:14] <Laurenceb> yeah
[15:14] <Laurenceb> works now.. I think
[15:14] <Laurenceb> needs more testing still
[15:14] <eroomde> what was it doing and what's it doing now?
[15:15] <Laurenceb> it was oscillating
[15:15] <Laurenceb> now its stable
[15:16] <eroomde> the reference signal was oscillating?
[15:16] <eroomde> that's...bad
[15:16] <Laurenceb> yes
[15:16] <Laurenceb> lol
[15:16] <Laurenceb> at very high frequency
[15:16] <Laurenceb> it was doing some weird stuff
[15:16] <Laurenceb> and the load on the load cell influenced it
[15:17] <Laurenceb> seems the time delay was related to the size of the output capacitor on the ref vreg
[15:17] <SpeedEvil> I blame immigration.
[15:17] <SpeedEvil> It's all the fault of the poles.
[15:17] <Laurenceb> and the zeros
[15:17] <eroomde> on complicated aircraft
[15:18] <Laurenceb> what on them?
[15:18] <Laurenceb> snakes?
[15:18] <Laurenceb> snakes on a complicated aircraft
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[15:24] <tweetBot> @daveake: LORA1 has arrived. Landing site was a field of sheep; looks like they gave the aerial wires a good chew! #UKHAS https://t.co/eyfQ03y0jg
[15:26] <eroomde> or someone said 'it's fine, i'll just use my penknife' when they decided against buying proper wire strippers
[15:26] <adamgreig> now they have two problems?
[15:27] <adamgreig> christ
[15:27] <SpeedEvil> The fun part is a skilled person can use their penknife.
[15:27] <adamgreig> or their teeth
[15:27] <eroomde> or a magnifying glass to focus the sun's rays
[15:27] <SpeedEvil> And cause unskilled watchers to fuck it up
[15:27] <adamgreig> ighter
[15:27] <adamgreig> lighter, even
[15:27] <SpeedEvil> Lighter is great for stripping enamelled wire
[15:30] <SpeedEvil> ^99.9% of the time.
[15:30] <SpeedEvil> 0.01% of the time, the skilled person fucks up.
[15:31] <SpeedEvil> (math mistake intentional)
[15:31] <SpeedEvil> 'I don't need safety guards'
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[15:50] <gonzo_> I used to strip enamelled wire, by scraping a line of coating off one side, then apply the iron. The solder would wick under and lift the coating off as the heat softened it
[15:50] <gonzo_> depending on the coating
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[17:00] <Lunar_Lander> hello
[17:02] <Laurenceb> http://i.imgur.com/5NRl00D.png
[17:02] <Laurenceb> its messy
[17:02] <Laurenceb> but its fast
[17:03] <Laurenceb> I think all the mess is related to me picking the test mass off by hand
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[17:03] <BeaverOne> Laurenceb: what project are you working on?
[17:03] <Laurenceb> you can see my gripping it at 1.32
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[17:04] <Laurenceb> BeaverOne: test stand for mini rockoons
[17:04] <BeaverOne> !!!!
[17:04] <BeaverOne> Laurenceb: very interested in that
[17:04] <jcoxon> DL1NBR-12 has re-appeared in russia
[17:10] <kc2pit> eroomde: Thanks for giving me an excuse to reread Ignition. I expect to get some strange looks when I get to the bit about the card gap test and the bats.
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[17:17] Nick change: Wiktor -> creepyWiktor
[17:18] Nick change: creepyWiktor -> Wiktor
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[17:48] <SpacenearUS> New vehicle on the map: 03KD2EAT-11 - 12http://tracker.habhub.org/#!qm=All&q=KD2EAT-11
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[18:01] <eroomde> kc2pit: i know right
[18:02] <eroomde> i also kind of fancy a naval canon turret as an armoured lab
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[19:00] Nick change: Upui -> Upu
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[19:59] Action: Laurenceb lols
[19:59] <Laurenceb> http://emdrive.wiki/Potential_EMDrive_solar_system_explorer_ship
[20:00] <chris_99> heh
[20:00] <Laurenceb> why did I know to expect this
[20:01] <Laurenceb> http://forum.nasaspaceflight.com/index.php?topic=38577.msg1441969#msg1441969
[20:01] <mattbrejza> earth to jupiter in 61 days?
[20:01] <Laurenceb> his brain is already there
[20:02] <mattbrejza> or 167 to pluto
[20:05] <Lunar_Lander> "neptune and back in six minutes"
[20:05] <Lunar_Lander> :)
[20:06] <Lunar_Lander> (first episode of Star Trek ENT for the record)
[20:17] <Laurenceb> wow high speed load cells are awesome
[20:18] <Laurenceb> I can see individual myofilaments activating in my arm
[20:19] <Laurenceb> this is bonkers
[20:21] <chris_99> whatcha doing?
[20:22] <Laurenceb> just prodding it with my finger then sampling at 100khz
[20:22] <Laurenceb> looking at the noise
[20:22] <Laurenceb> can see all the high speed muscle tissue funkiness
[20:23] <chris_99> the noise definitely relates to muscle stuff?
[20:24] <ProSpectre> when will the Pi go to ISS?
[20:26] <daveake> Dec 3rd
[20:31] <SpeedEvil> Laurenceb: do you get the same if you try it on a chicken?
[20:31] <SpeedEvil> ( a dead chicken)
[20:34] <chris_99> heh good idea
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[20:55] <eroomde> ProSpectre: i feel like the ISS is going to the Pi
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[22:30] <Laurenceb_> and its dead in here again
[22:30] <Laurenceb_> #highaltitude more like #slackeratwork
[22:30] <chris_99> haha
[22:30] <Lunar_Lander> :D
[22:32] <mfa298> we solved that by using slack at work for communications.
[22:34] <mfa298> seems like all the activity here is during the day when some of us are busy at work
[22:38] <Laurenceb_> "busy"
[22:42] <mfa298> well some of us are in the real world and nasty challenges to face.
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[23:15] <Laurenceb_> eroomde: pingnk this looks sane?
[23:15] <Laurenceb_> *do you think this looks sane?
[23:15] <Laurenceb_> http://i.imgur.com/PSezwcB.png
[23:15] <Laurenceb_> bottom drag coefficient, its for a 12cm long, 18mm diameter rocket with 65mm long nosecone
[23:16] <Laurenceb_> it doesnt look right to me
[23:16] <Laurenceb_> (this is openrocket)
[23:18] <Laurenceb_> also the peak at mach 1 looks low to me?
[23:20] <Laurenceb_> e.g. G7 bullet http://microcfd.com/images/g7-bullet-drag.gif
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[00:00] --- Thu Nov 5 2015