PROFILPELAJAR.COM

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Merged and redirected

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I merged this article with Lighter than air and redirected the page. Almost all of the information in this article was taken from that one; the few new additions have been copied to Lighter than air. Stebbins (talk) 05:50, 14 January 2009 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2009-01-14T05:50:00.000Z","author":"Stebbins","type":"comment","level":1,"id":"c-Stebbins-2009-01-14T05:50:00.000Z-Merged_and_redirected","replies":["c-Inwind-2009-01-21T10:09:00.000Z-Stebbins-2009-01-14T05:50:00.000Z"]}}-->

The article should not be merged (see Talk:Lighter than air#Merge tag). Inwind (talk) 10:09, 21 January 2009 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2009-01-21T10:09:00.000Z","author":"Inwind","type":"comment","level":2,"id":"c-Inwind-2009-01-21T10:09:00.000Z-Stebbins-2009-01-14T05:50:00.000Z","replies":[]}}-->

--Navigaiter2 (talk) 22:47, 17 January 2010 (UTC) I softened the misleading statement that "most countries have banned hydrogen for lifting gas in manned vehicles" because it made no distinction in types of manned vehicles. After reading FAR Part 21, I found that they ban H2 only for purposes of granting what they call a "Type Certification." It is the set of ultimate government safety hoops which apply to commercially manufactured vessels destined to be used for human passengers and air freight for money. Ultralights and Experimental class airships are usually made at home and do not require a type certificate. See our airship design workshp at smallblimps.lefora.com Allen Meece, the Navigaiter ;-][reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2010-01-17T22:47:00.000Z","author":"Navigaiter2","type":"comment","level":1,"id":"c-Navigaiter2-2010-01-17T22:47:00.000Z-Merged_and_redirected","replies":[]}}-->

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text modification

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I have added a lot of text and I did many modifications:
I had originally translated this English article into Dutch (my native language), then I added a lot of interesting stuff to that Dutch text, and now I added the same things to the original english text. But, because I'm not a native english speaker, there may be language errors or strange word choices in my text. Please feel free to correct them and make fluent english text out of my words. --Erik Wannee (talk) 13:53, 17 April 2011 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2011-04-17T13:53:00.000Z","author":"Erik Wannee","type":"comment","level":1,"id":"c-Erik_Wannee-2011-04-17T13:53:00.000Z-text_modification","replies":[]}}-->

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Question about lifting gas in Vega mission balloons

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I have a question: The balloons in the Vega mission on Venus used helium as lifting gas. As explained in this article, this is not necessary in this quite dense atmosphere. Helium has the disadvantages of diffusing easily through a balloon's wall, the need to be transported in a compressed cilinder, and having to be inflated into the balloon at the right moment.
That raises the question why they didn't simply bring some water in this balloon? During the journey in interplanetary space it would stay compactly frozen; as soon at it will enter the hot venus atmosphere (during a parachute descent) it will be heated to steam, automatically inflating the balloon. No pressure vessel needed, no special valves to let the gas into the balloon: fewer things that can fail. The lifting power of steam on Venus will certainly be sufficient to float a balloon in Venus' atmosphere and it will not easy diffuse through the balloon wall.
Who can explain why they have chosen for helium? If you have a good explanation, please add it to the text of this article. Erik Wannee (talk) 19:59, 1 June 2011 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2011-06-01T19:59:00.000Z","author":"Erik Wannee","type":"comment","level":1,"id":"c-Erik_Wannee-2011-06-01T19:59:00.000Z-Question_about_lifting_gas_in_Vega_mission_balloons","replies":[]}}-->

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Vacuum vs helium

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This article states vacuum would weigh 16% less than helium but Vacuum airship has 14%. Which is right? Bizzybody (talk) 06:13, 26 July 2014 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2014-07-26T06:13:00.000Z","author":"Bizzybody","type":"comment","level":1,"id":"c-Bizzybody-2014-07-26T06:13:00.000Z-Vacuum_vs_helium","replies":["c-Erik_Wannee-2014-07-27T10:27:00.000Z-Bizzybody-2014-07-26T06:13:00.000Z"]}}-->

By definition, the weight of a perfect vacuum is zero. So the only weight would be the spheres that contain the vacuum. In the postulated theoretically perfect situation with weightless spheres, they don't have weight, too. So then the whole vehicle would be weightless. That would make the absolute weight infinitely much less than that of any other airship filled with gas.

But I think your question is not about the weight but about the buoyancy. Then I propose to do the same calculation as in the chapter 'Hydrogen versus helium' but then we take vacuum instead of hydrogen:

The buoyancy for one m³ of helium in air is:

0.178 kg * (1 − (1.292 / 0.178) ) = -1.114 kg

The buoyancy for one m³ of vacuum in air is:

0 * (1 − (1.292 / 0) ) = .... Hey, division by zero? What's wrong with this formula?

I really think that the formula that they used there is completely wrong. In my opinion it should be:

F_B=(ρ_air - ρ_gas) * g * V

Where F_B=Buoyant force; g=gravitational acceleration=9.8 m/s²; V=volume (in m³).

Let's use this formula:

The buoyancy for one m³ of helium in air is:

(1.292-0.178) * 9.8 = 10.9 Newton

The buoyancy for one m³ of vacuum in air is:

(1.292-0) * 9.8 = 12.7 Newton

So the buoyancy of vacuum is 12.7 / 10.9 = 1.16 or 16% higher than that of helium. Erik Wannee (talk) 10:27, 27 July 2014 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2014-07-27T10:27:00.000Z","author":"Erik Wannee","type":"comment","level":2,"id":"c-Erik_Wannee-2014-07-27T10:27:00.000Z-Bizzybody-2014-07-26T06:13:00.000Z","replies":[]}}-->

I have corrected the wrong formulas. I have also removed that stupid term 'buoyancy mass', because buoyancy has not a mass but a force.
And about those 14% and 16%: they are both correct. It is like the following situation: If you would decrease a number from 20 to 10; you decrease it by 50%. But if you would increase that number again from 10 to 20, you won't have to increase it with 50% but with 100%. Erik Wannee (talk) 06:09, 29 July 2014 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2014-07-29T06:09:00.000Z","author":"Erik Wannee","type":"comment","level":1,"id":"c-Erik_Wannee-2014-07-29T06:09:00.000Z-Vacuum_vs_helium","replies":[]}}-->

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"Negligible" difference between H and He

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Keep in mind, the difference between the two may be small, but the weight/volume ratio of the balloon and cargo carrying apparatus does not change between the two gasses, so the weight cost is absorbed entirely by the payload capacity.

See http://www.airships.net/helium-hydrogen-airships/ for figures on how this affects various airship designs and take note of the fact that the difference is large enough that the Hindinberg could not have flown using helium. — Preceding unsigned comment added by 71.4.36.14 (talk) 21:50, 20 April 2017 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2017-04-20T21:50:00.000Z","author":"71.4.36.14","type":"comment","level":1,"id":"c-71.4.36.14-2017-04-20T21:50:00.000Z-\"Negligible\"_difference_between_H_and_He","replies":[]}}-->

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Hot Air Ballooning citation

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Google easily found a weather balloon ride company website (Maryland-based Light Flight Hot Air Balloons, Inc. & Barnstormer Aero) which gives their rule of thumb as 140 degrees Fahrenheit hotter than the surrounding air. It's a commercial/vendor site, not an academic or journalistic source, but they have no plausible reason to lie about something so easily verifiable within industry safety manuals, especially given that the page is designed to assure customers of their safe operating conditions. FYI, I'm located in New Mexico, not Maryland, and have no ties to the company. 97.123.99.176 (talk) 21:30, 20 February 2018 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2018-02-20T21:30:00.000Z","author":"97.123.99.176","type":"comment","level":1,"id":"c-97.123.99.176-2018-02-20T21:30:00.000Z-Hot_Air_Ballooning_citation","replies":[]}}-->

Merge "Lighter than air"

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The Lighter than air article has virtually the same content as this one. And obviously the topics are essentially the same. Even if you want to argue that there is a slight distinction, I cannot imagine one could come up with enough unique content to merit two articles.

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Opinion and Understanding

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I agree the articles to be merged, as their similarity of the content really means a merging will make sense. Thanks guys! — Preceding unsigned comment added by 113.254.108.215 (talk) 08:51, 20 May 2018 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2018-05-20T08:51:00.000Z","author":"113.254.108.215","type":"comment","level":1,"id":"c-113.254.108.215-2018-05-20T08:51:00.000Z-Opinion_and_Understanding","replies":[]}}-->

-- MC 141.131.2.3 (talk) 22:35, 22 February 2018 (UTC)[reply]__DTELLIPSISBUTTON__{"threadItem":{"timestamp":"2018-02-22T22:35:00.000Z","author":"141.131.2.3","type":"comment","level":1,"id":"c-141.131.2.3-2018-02-22T22:35:00.000Z-Opinion_and_Understanding","replies":[]}}-->