bascule Posted October 16, 2009 Share Posted October 16, 2009 (edited) I might as well post this considering it began in my former hometown... http://www.cnn.com/2009/US/10/15/colorado.boy.balloon/index.html The story began with the announcement that a 6-year-old boy had constructed a relatively large UFO-shaped helium balloon along with his father. Allegedly, one of his brothers reported that the boy had hopped aboard the balloon shortly before it broke free of the ground and floated up into the air. (Bonus points: calculate the volume of helium needed to lift your average 6-year-old into the air and see if it is even plausible for this much helium to fit in a 20' diameter 5' tall circular balloon) After an hour in the air, a news helicopter began following the balloon. In the meantime reports came in that something had fallen from the balloon. The balloon continued its flight for another hour, being circled by the helicopter, until it eventually touched down in Colorado Springs. The boy was not aboard. Some time later, the boy was discovered hiding in the attic of his parents' garage. There's been a lot of suspicion this was all a publicity stunt: wI6UONWCq7A Quote the young would-be pilot to his parents: "you guys said that we did this for the show" Merged post follows: Consecutive posts merged(Bonus points: calculate the volume of helium needed to lift your average 6-year-old into the air and see if it is even plausible for this much helium to fit in a 20' diameter 5' tall circular balloon) I did my own extra credit assignment: Other news sources are reporting the balloon was 7 feet tall, so let's split the difference and call it 6 feet in diameter. The balloon appears to be an oblate spheroid with a horizontal radius of 10 feet and a vertical radius of 3 feet. Using the formula for the volume of a spheroid: [math]\frac{4}{3}\pi (10 feet)^2(3 feet)=35584L[/math] According to Wikipedia, helium provides approximately 9.8N of lift per cubic meter So this balloon would provide approximately 36 kilograms lifting force, or about 79 pounds. Various estimates place the weight of your average 6 year old boy between 65-70 pounds. So it's possible this balloon might be capable of lifting a 6 year old child. Edited October 16, 2009 by bascule Consecutive posts merged. Link to comment Share on other sites More sharing options...
Mr Skeptic Posted October 16, 2009 Share Posted October 16, 2009 I don't think the kid was smart enough to realize what hiding could do. He probably accidentally loosed the balloon and then hid because he was afraid that he lost the balloon they did "for show" and his dad would be mad. Calculation: for a rectangular balloon of 5' X 20' X 20' in 25 C air, it could lift 56 kg. Make that about 1/3 or 1/2 to make up for the irregular shape, and you get 18 or 28 kg. A six year old should be about 20 kg. Add a few kg for the weight of the balloon. Yeah, I think it would be feasible. Link to comment Share on other sites More sharing options...
Pangloss Posted October 16, 2009 Share Posted October 16, 2009 "So, you listen to me. Listen to me: Television is not the truth! Television is a God-damned amusement park! Television is a circus, a carnival, a traveling troupe of acrobats, storytellers, dancers, singers, jugglers, side-show freaks, lion tamers, and football players. We're in the boredom-killing business!" Link to comment Share on other sites More sharing options...
bascule Posted October 16, 2009 Author Share Posted October 16, 2009 I don't think the kid was smart enough to realize what hiding could do. I think it's all a publicity stunt. Watch the video. Link to comment Share on other sites More sharing options...
EZmpc Posted October 18, 2009 Share Posted October 18, 2009 (edited) I did a "layman's" writeup on this a few days ago to share my thoughts on the event with friends and family - how ridiculous it was that it would have taken only a basic understanding of buoyancy principles and geometry to sort out in a few minutes that the craft wasn't large enough to carry away Falcon. here are my calculations... http://spreadsheets.google.com/ccc?key=0AhK386hjlMQGdEhrVktsOWlnNERCS3RtV3hueGtSVGc&hl=en Remember that Fort Collins, CO is at an altitude of around 5000 feet, so the densities of air (and the helium gas) are lower than at sea level. Also, the ambient temperature and relative humidity are a consideration. I set up my Excel spreadsheet at home to use gas laws to calculate the actual densities instead of using the 20C temp/sea-level standard which is commonly referenced when discussing gas densities. There are various unknowns - most work AGAINST the amount of potential lift. Anyhow - I found this forum when searching if anyone else was discussing the hard science. I look forward to reviewing other subjects in the forum! - EZ Edited October 18, 2009 by EZmpc Link to comment Share on other sites More sharing options...
Mr Skeptic Posted October 20, 2009 Share Posted October 20, 2009 (edited) It seems the balloon wasn't enough to lift 37 pounds. Edit: This is what I overheard over the radio. Edited October 20, 2009 by Mr Skeptic Link to comment Share on other sites More sharing options...
bascule Posted October 20, 2009 Author Share Posted October 20, 2009 here are my calculations... http://spreadsheets.google.com/ccc?key=0AhK386hjlMQGdEhrVktsOWlnNERCS3RtV3hueGtSVGc&hl=en We're getting very, very different figures for the volume of the balloon. "Cone shape assumed" - appears to be the key difference. I'm modeling the balloon as an oblate spheroid. Your volume is: 14.83 m2 My volume is: 35.58 m2 My volume is over twice the size of yours. Also I don't think the balloon is best modeled as a cone. Link to comment Share on other sites More sharing options...
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