Launching liquids
Hi everybody,
A group of students in my class would like to design an experiment to investigate the behavior of liquids in near space during our May 23 launch. They would like to put several different liquids in plastic containers into a pod and film them with a mini-camcorder. I found a brief description of a similar experiment in chapter 13 of Paul Verhage's book on parallax.com (thanks, Howard!). It uses a servo-controlled "speed control valve" to exhaust the air inside the container. This sounds more complicated than what the students will be able to do in a short period of time. Does anybody in our group have any experience with liquids?
Cheers,
Bernhard
A group of students in my class would like to design an experiment to investigate the behavior of liquids in near space during our May 23 launch. They would like to put several different liquids in plastic containers into a pod and film them with a mini-camcorder. I found a brief description of a similar experiment in chapter 13 of Paul Verhage's book on parallax.com (thanks, Howard!). It uses a servo-controlled "speed control valve" to exhaust the air inside the container. This sounds more complicated than what the students will be able to do in a short period of time. Does anybody in our group have any experience with liquids?
Cheers,
Bernhard
Replies to This Discussion
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Permalink Reply by Howard Brooks on -
We have launched liquids (water, water/alcohol mixtures, cola, fruit juices, liquid hand soap, hand sanitizer, oils) on several flights. We use small plastic washing bottles (30 ml Nalgene washing bottles) with the spray tube removed. We never fill the entire bottle and do not attempt to evacuate the air. Our students have recorded the temperatures of the liquids during the flight with a simple diode-resistor thermometer connected to a regulated 5 volt power source. The diode is inserted into the bottle through the spray tube hole. It is a challenge to seal the lid and the hole for the thermometer, but we have had success with the 2 hour epoxy that we use in pod construction and/or silicon caulk. Sealing is critical since the orientation of the bottles is not predictable during the first few minutes of the descent.
The StratoStar realtime data downlink has allowed the students to watch the temperature changes during flight. The data clearly show the difference in heat capacity of various liquids and the phase transition process when that occurs. Here a couple of graphs of data from previous flights
The thermometers may not have been perfectly zeroed, but the shapes of the curves are accurate.
The Nalgene bottles are translucent and I'm not sure how much detail would be available on the video image.
Howard
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Permalink Reply by Bernhard Beck-Winchatz on -
This is very interesting, Howard! Thanks for sharing! The difference between oil and water based liquids is very obvious, so I think just comparing these two along with air temperature would give a really interesting result for non-science students, without them having to do much data analysis. I think they are really fond of their idea to video tape the liquids inside the pod, so I won't try to convince them not to do it. But I'll definitely encourage them to keep track of the temperatures as well. Thanks also for the tip to use the 30 ml Nalgene bottles!
Howard Brooks said:We have launched liquids (water, water/alcohol mixtures, cola, fruit juices, liquid hand soap, hand sanitizer, oils) on several flights. We use small plastic washing bottles (30 ml Nalgene washing bottles) with the spray tube removed. We never fill the entire bottle and do not attempt to evacuate the air. Our students have recorded the temperatures of the liquids during the flight with a simple diode-resistor thermometer connected to a regulated 5 volt power source. The diode is inserted into the bottle through the spray tube hole. It is a challenge to seal the lid and the hole for the thermometer, but we have had success with the 2 hour epoxy that we use in pod construction and/or silicon caulk. Sealing is critical since the orientation of the bottles is not predictable during the first few minutes of the descent.
The StratoStar realtime data downlink has allowed the students to watch the temperature changes during flight. The data clearly show the difference in heat capacity of various liquids and the phase transition process when that occurs. Here a couple of graphs of data from previous flights
The thermometers may not have been perfectly zeroed, but the shapes of the curves are accurate.
The Nalgene bottles are translucent and I'm not sure how much detail would be available on the video image.
Howard
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