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Old Sep 19, 2012, 07:38 AM
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Zen09's Avatar
Germany, HB, Bremen
Joined Jun 2010
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Quote:
Originally Posted by dave1993 View Post
and it has big time more lift than helium.
Not quite, hydrogen will lift about 10% more than helium for the same volume.


I'm also thinking about using hydrogen for my future project. Helium would be ridiculously expensive.
I guess a hydrogen gas cylinder from industrial suppliers would be cheaper, but if you need a licence for that I think electrolysis is the way to go.
There are a few problems with that though, like building a powerful and large enough cell to supply a reasonable flow so you don't have to wait weeks till the balloon is done. Or taking a gasoline electric generator at field to supply the cell.

Anyway, extreme care must be taken when manipulating hydrogen, like using antistatic gloves and costume.Things can turn into a disaster dead easily.


BTW, how do you cover the filament with rcandy? Pour it when it's liquid or stuff it in powder form?
AFAIK this type of fuel does not ignite as easily as BP for example. So I have not even tried it, but used powder from match stick heads instead - which I know are extremely sensitive. If it works with rcandy it's great!
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Old Sep 19, 2012, 07:56 AM
RC beginner
New York
Joined Oct 2008
6,054 Posts
you are probably right about the difference between the two. i was thinking because hydrogen is half the weight it would lift 2x more but apparently this aint true. maybe walmart helium is the best way to go. but its not pure and more expensive. diy hydrogen is certainly cheaper. so i dunno.

im not sure about hydrogen disaster. unlike the test tube that pops/whistles, our baloons filled with pure hydrogen just went up pretty harmlessly in a blue ball of flame. i would not try that indoors though.

we dipped the filament in the melted rocket candy. thin coat was best. thick coats sometimes (but rarely) failed to ignite. it was hard to get the powder form to stick. same for match head perchlorate etc.
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Old Sep 19, 2012, 08:37 AM
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Germany, HB, Bremen
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Yes it's half the weight but air displacement is what matters more, and 1.2kg / m^3 air density compared to 0.18 and 0.08 of helium/hydrogen makes the difference less.

Quote:
Originally Posted by dave1993 View Post
our baloons filled with pure hydrogen just went up pretty harmlessly in a blue ball of flame.
Unless is mixed with oxygen, it does not blow that bad, but you wouldn't want to be anywhere near (while filling it). Serious burns.

I was afraid I could damage the filament with semi liquid fuel, since it's fragile. Gonna test with powder, it should stick if I fill the whole bulb .
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Old Sep 20, 2012, 09:11 AM
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Thanks dave, will look more into it.
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Old Sep 22, 2012, 08:56 PM
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United States, CA, Arcata
Joined Oct 2011
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I second the use of an MCU over the Pi for this application... The onboard system doesn't need a whole lot going on, and the Pi is a bit overkill. Plus a chip such as the Atmega328p can be had for only a few bucks. There are many sensor modules available including altimiters, GPS, etc.
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Old Oct 01, 2012, 10:02 PM
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Spanaway, WA
Joined Jul 2006
1,585 Posts
Well as of right now all my son wants to do is send legos up with a camera. I have not had much time to play with any electronics so the project is not moving any which way for the time being. I will let you all know what happens as it happens.

Massey
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Old Oct 02, 2012, 07:58 AM
AndyKunz's Avatar
Illinois
Joined Sep 2001
23,653 Posts
Some inspiration for you both:

Teenagers Send Lego Man Into Space (0 min 56 sec)

A Toy Train in Space (2 min 28 sec)


Andy
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Old Oct 02, 2012, 10:06 AM
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Colorado
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There was a time back in the summer of 2000 when I launched 3-4 helium filled balloons per day to 70,000+ ft. Depending on wind conditions, telemetry indicated that the furthest a payload landed was 270 miles from the launch site. Flight time to balloon burst averaged 2.5 hours.
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Old Oct 02, 2012, 12:58 PM
Stuart
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Joined Dec 2008
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Originally Posted by rmteo View Post
There was a time back in the summer of 2000 when I launched 3-4 helium filled balloons per day to 70,000+ ft
Thats a lot of Lego, what were you building up there ?
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Old Oct 02, 2012, 08:04 PM
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Thats a lot of Lego, what were you building up there ?
I was feld testing a phased array antenna tracking system for radiosondes. Although we already had GPS based systems at the time, the customer wanted an alternative in case access to DOD satellites were denied during a conflict.
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Old Oct 03, 2012, 10:04 AM
RC beginner
New York
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im also considering something like that for tracking because gps is so expensive and heavy. but those little 50 cent ook tx modules weigh almost nothing. so im trying to find some way to mod them for 462mhz fm so i can track with cheapo frs talkies. ive been working on this for 2 years but still not quite there.
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Old Oct 03, 2012, 10:53 AM
Stuart
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UK, Cardiff
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Quote:
Originally Posted by dave1993 View Post
im also considering something like that for tracking because gps is so expensive and heavy
Well, the Mediatek 3329 GPS modules cost around $25 (or less) and weigh 6g. The Hope RF modules weigh 0.8g.
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Old Oct 03, 2012, 11:33 AM
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New York
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so only 80x more expensive and 10x heavier. lol! actually i can get sirfIII modules for around $8 even with antenna weighing around a gram but still too much for my balloon and micro uav plans:

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Old Oct 03, 2012, 07:58 PM
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Colorado
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Quote:
Originally Posted by dave1993 View Post
im also considering something like that for tracking because gps is so expensive and heavy.
At the time, GPS sondes (a disposable item, the ground tracking equipment sold for about US$40,000) at around US$800 each were considered cheap.

On the system I was working on, the sondes were considerably cheaper (about 1/4 the price) as they did not have GPS (just a UHF transmitter) but the ground station had a budgetary price of US$250,000+ IIRC. And it it weighed something like 150lb and required a 3-man crew to deploy.

FYI, something I am working on High Endurance UAV, motive/power subsystem??

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Old Oct 04, 2012, 11:56 AM
RC beginner
New York
Joined Oct 2008
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yikes! so if i can build a tracker for a buck or two for hobby use it will be very satisfying. im pretty close atm with just some minor cost and range issues. my goal is to get 10-15miles. i know from field tests the frs can do that now its the tx end (modulation. antenna, etc) that needs work.

btw i hope that guy dont nudge his throttle stick by accident. it will give new meaning to the phrase "being in two places at once".
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