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3-30-2014 ~ Blog #603 (David)
There's no way out of our neighborhood without driving by a farm. On the way back from German today Brigitta and I stopped by one of the farms and took pictures of cows. Bri took the first four with the D3100 and the super-zoom 18-200. The following shots were taken with a 50mm f1.4, 11mm f2.8 and an old 85mm f2.
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3-16-2014 ~ Blog #602 (David)
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Umbrella Rocket Success! 3-16-2014 ~ Blog #600 (David)
Read about it here: Umbrella Rocket Success!
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Umbrella Rocket and Green Tumbler Rocket Fails 3-9-2014 ~ Blog #599 (David)
Click the link above for a post on this
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3-6-2014 ~ Blog #598 (David)
I've had a great birthday. Here are a few photos:
For my birthday dinner Joan made one of my favorites. It never had a real name because Joan invented it. Whenever I request it I always do so by describing it, "that spaghetti with zucchini, mushrooms, onions and sausage". I pointed out during dinner that it really needed a name and Brigitta immediately chimed in, "How about Spaghetti and Friends?" We all laughed and that pretty much set the name of Joan's awesome meal.
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The Finless Rocket Flies Again 3-5-2014 ~ Blog # 597 (David)
I redesigned the Finless Rocket. The launch lugs have been replaced with rail buttons for a more streamlined look. This version uses a 100+ gram plastic ogive nose cone that has 200 grams of lead in the very tip. Loaded with a motor and parachute, the entire rocket weighs about 825 grams. The concentrated weight in the nose shifts the center of gravity of this rocket well in front of its center or pressure, even without fins. The first version of this rocket included a long section of body tube behind the motor nozzle. When it flew the first time it appeared very underpowered. On a rocketry forum I've recently learned about the "Krushnic Effect" which basically boils down to rocket motors lose significant power if the nozzle is blasting through a tube. I cut the tail tube down from about 9 inches to about 2 inches. The 70 Newton, 1 second burn motor lifted the rocket very well. It flew very straight for a few hundred feet where it wobbled before apogee. It was windy and gusty today. Based on parachute decent time and ground distance covered I calculated that one rocket was pushed along by over 20 mph winds. I think the wobble may have been a gust induced wind cocking. Even if the finless rocket naturally wobbles while coasting up, I'm very happy with its performance. It proves the point that rocket stability really does come down to the primary rule of placing the center of pressure behind the center of gravity. The finless rocket proves that some of the most trusted rocket simulation programs can be wrong. It also proves that the old-school string test has a lot of validity. Check out the flight video and "wind tunnel" test.
(47 seconds, 37MB, 1080p)
My thumb shows the CG with a spent motor. The CG with a live motor is about 2 inches back.
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3-4-2014 ~ Blog # 596 (Joan & David)
Today was Annika 9th Birthday, and also Fat Tuesday. Anytime her birthday falls before Lent it is cause for celebration, but when it falls on the day before... well well made it extra grand. Joan made her a Hall version of a King Cake for breakfast (alas, no bay inside). Annika took in ice cream bars for her classmates to celebrate her special day. Joan made Annika's choice for dinner: homemade ham and macaroni and cheese with brownies for dessert. She had a great time opening her gifts, almost as great a time as Svea and Brigitta had wrapping them. We've created a tradition of wrapping birthday presents in newspaper and drawing pictures overtop. Here are Annika's gifts for this year.
Nana's 91st birthday was celebrated on Sunday. Svea made her a Texas Sheet Cake and Joan made chicken soup because Nana was cold. She especially liked her digital clock with REALLY big numbers on it.
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