Balloon. Parachute. Payload

Transcription

1 Steps to launch a weather balloon 1. Study the winds 2. Assemble the payload (box of stuff) 3. Inflate the balloon 4. Tie it all together with the parachute 5. Launch (Let it go) As balloon rises, it gets bigger in the thinner air When balloon gets 20 feet across in size, it pops Parachute brings the payload back to earth 6. Track the balloon as it rises, pops, and descends 7. Find it, open the camera, and look at the pictures. Balloon Parachute Payload

2 Studying the Winds We use a web site to predict where the balloon will go It s best to launch when the balloon will land at a place that s easy to find

3 Assemble the payload Our payload is a Styrofoam cooler. Lightweight Big Inside we put Camera Programmed to take pictures every 10 seconds Camera lens sticks out a hole in the side of the cooler GPS tracker Transmits its location every 10 minutes to a satellite The satellite puts it on a web page that we can see with a computer. We want to keep the payload as light as possible

4 Inside the cooler, we have the camera and GPS tracker Outside the cooler, we have emergency Space blanket foil. This acts as a radar reflector so airplanes can see it from far away. Camera is specially programmed so it takes pictures every 10 seconds with a fast shutter, so the pictures won t be blurry. Camera sticks out the side tilted down, so we get pictures of the earth and sky. The Parachute brings the payload back slow and steady, so we get clear pictures on the way down. Also, it s required by law to have a parachute.

5 Weight is very important The lighter the payload, the higher the balloon will rise Adding up the Payload Weight: Empty Cooler 4.50 oz Camera 5.82 oz Four AA batteries 2.04 oz GPS Tracker 7.37 oz Foil, glue, line 0.07 oz ========= Payload Weight Empty Balloon Parachute 19.8 oz oz oz Gross Weight = oz (There are 16 oz in a pound. 16 So, divide Gross Weight (oz) by 16) = 3.16 lbs

6 Balloon Math Helium is measured in Cubic Feet One cubic foot is about the size of a birthday party balloon. It takes about 16.2 cubic feet to lift one pound Or, about 16 party balloons to lift a pound of butter. To compute how much helium we need 3.16 lbs total weight to lift lbs free lift so the balloon goes up fast = lbs total weight that we need to lift X cubic feet per pound of lift = cubic feet of helium needed The balloon will be exactly 5.0 feet across when inflated with this much helium. Expert Question 1: Our tank holds 80 cubic feet of helium. How many party balloons could we fill with the left-over helium? Expert Question 2: How many party balloons does it take to lift a single cube of butter?

7 If our payload weighs 3.16 lbs and we inflate the balloon so it s 5 feet across, then - It will go up for about 2 hours 6 minutes - It will rise to an altitude of 99,000 feet (19 miles), at a rate of 780 feet per minute - That s about 9 miles/hr - As it rises for 19 miles, the air gets thinner and thinner, and our balloon expands to 20 feet across - The balloon will then pop, the parachute will open, and it will start falling (descending) to earth - The parachute is 5 feet across, and will fall at a rate of 1139 ft/min - That s about 13 miles per hour - It will take 1 hour 27 minutes to fall back to earth - The payload should hit the ground 3 hours 33 minutes after launch 5 feet Across at launch How cold is it up there? At 19 miles high it s about -58 degrees F. But it s actually colder at 16 miles high, where it s -70 degrees F. If you pour a glass of water at -70 F, it will freeze before it hits the ground!

8 What happens if we Buh-Bye! Nice Knowin Ya! Don t inflate enough? -The balloon will go up too slowly, get caught in the winds, and travel too far away. Inflate too much? -The balloon will rise quickly, but will pop too soon.

9 Balloon Launch Checklist Foil glued to payload Reward notice taped on payload GPS Tracker turned on GPS Tracker sending position updates Camera turned on and taking pictures Payload container tied up with line Balloon inflated to 5 feet across Balloon tied to parachute Parachute tied to payload Countdown Launch! Write down time of launch

10 What could we do differently? Use a bigger balloon to go higher Use a different camera and shoot video Use different instruments Temperature Altitude Launch at night and take pictures of the moon and stars Any other ideas? How much does it cost? Weather balloon Kaymont 600 $20 (e-bay) Camera Canon A470 $65 (e-bay) Parachute Rocketman 5 $50 (the-rocketman.com) Cooler lifoam 30qt $3 (K-Mart) GPS Tracker*1 SPOT 1 $70 (e-bay) Helium*2 80 cf Tank $40 (Airgas) Lithium batteries Energizer $10 (Target) Total $248 *1 You have to buy a $100 annual subscription for the GPS tracking service. *2 You need a regulator for the helium tank. Either borrow one, or buy one from Harbor Freight for $40.