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This page (revision-18) was last changed on 04-Jan-2013 13:33 by pgaillard  

This page was created on 23-Dec-2011 20:37 by pgaillard

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At line 36 added one line
The sail could also be the balloon itself that lifted the payload. Tthere are actually [solar balloons|http://www.solar-balloons.com/] that can lift themselves to 50000 feet.
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In our case the idea would be to use helium inside to lift first and then heat the air below the balloon and cool the air above to create a push upwards.
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!! Communication with device
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Wifi is cheap, ubiquitous and unregulated. Wikipedia [documents|http://en.wikipedia.org/wiki/Long-range_Wi-Fi] some pretty long range links (over 200km) that require directional antennae.
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Pointing one antenna is reasonably easy but pointing the antenna on the balloon seems much trickier...
!! Near Space Telescope
If we bring some decent telescope up with a balloon and point it up we get a small space telescope.
This reduces:
* atmospheric losses. The main benefit is for blue and ultra-violet (20% and more). So for the other colors, the benefit is not really awesome for amateurs...
* lens effects caused by atmospheric turbulences
* no blue sky even during the day: you could observe during the DAY.
The downsides are:
* more cosmic rays?
* stability is an issue and may reduce the ability to benefit from the absence of atmospheric turbulences (awesome seeing).
Given the risk of not recovering the telescope, we need a cheap telescope maybe [DIY|Do it Yourself telescopes]
!! Balloons and blimps
A balloon can fly very high (50km) and is pretty safe (no explosives involved if it's helium).
The air weighs about 1.3kg per cubic meter at sea level, so a balloon of a couple cubic meters should be enough to lift a good payload.
Since helium is expensive, it might be tempting to use hydrogen instead.
If a cubic meter at ground level there would be about 50 moles of dihydrogen, which would release about 50*286kJ = 15MJ if inflamed by air and require about the same energy to produce from water.
! Reading
* Nicolas Regnault's PHD Thesis (in French): http://tel.archives-ouvertes.fr/tel-00006558/en/. This contains interesting background info that's quite readable
** discussions about detection of supernovae, how they are visible with regular light
** discussions on merging information from different telescopes
** discussions about the effect of atmosphere (seeing, absorption).
* [FAA rules for balloons and rockets|http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&rgn=div5&view=text&node=14:2.0.1.3.15&idno=14]
Version Date Modified Size Author Changes ... Change note
18 04-Jan-2013 13:33 4.556 kB pgaillard to previous
17 04-Jan-2013 13:26 4.379 kB pgaillard to previous | to last
16 22-Mar-2012 09:53 4.018 kB pgaillard to previous | to last
15 16-Feb-2012 12:49 3.881 kB pgaillard to previous | to last
14 15-Feb-2012 16:46 3.696 kB pgaillard to previous | to last
13 15-Feb-2012 16:43 3.278 kB pgaillard to previous | to last
12 30-Jan-2012 17:12 2.781 kB pgaillard to previous | to last
11 20-Jan-2012 09:37 2.452 kB pgaillard to previous | to last
10 20-Jan-2012 09:30 2.115 kB pgaillard to previous | to last
9 20-Jan-2012 09:21 1.745 kB pgaillard to previous | to last
8 20-Jan-2012 09:20 1.736 kB pgaillard to previous | to last
7 20-Jan-2012 08:55 1.073 kB pgaillard to previous | to last
6 23-Dec-2011 21:06 0.726 kB pgaillard to previous | to last
5 23-Dec-2011 21:05 0.735 kB pgaillard to previous | to last
4 23-Dec-2011 20:56 0.592 kB pgaillard to previous | to last
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2 23-Dec-2011 20:53 0.447 kB pgaillard to previous | to last
1 23-Dec-2011 20:37 0.354 kB pgaillard to last
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