T.J.Bones
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- Jul 18, 2020
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Most altimeters are basically fancy barometers. I am not asking about gps based systems. Altimeters measure air pressure and correlate pressure changes with altitude. So, to get an altimeter to work it needs to be exposed to the atmosphere during rocket flight. The conventional/recommended way of doing this is by having holes in the rocket’s body tube to expose the on board altimeter to the outside atmospheric air pressure.
Now for question 1. Are holes in the body tube necessary if the only purpose of the altimeter is to record altitude (not for some other E-bay function)? In this case, couldn’t the altimeter be tethered to the nose cone and conduct its atmospheric reading at ejection? I know ejection does not always occur at apogee, but it is supposed to.
Now for the second question. Holes in the body tube will have air rushing by them during rocket flight. According to Bernoulli’s principle this rushing air will create a low pressure zone at the body tube hole. This in turn will lower the air pressure inside the body tube, wherein the altimeter is located. Since lower air pressure is interpreted as higher altitude, would not this make the altitude reading of the altimeter inaccurate? If the effect I am describing is so small as to be negligible, then could not the same conclusion be drawn about the necessity of the air holes in the first place?
If you are using a gps based altimeter, then the air holes should not needed for that system either.
Am I missing something here?
Now for question 1. Are holes in the body tube necessary if the only purpose of the altimeter is to record altitude (not for some other E-bay function)? In this case, couldn’t the altimeter be tethered to the nose cone and conduct its atmospheric reading at ejection? I know ejection does not always occur at apogee, but it is supposed to.
Now for the second question. Holes in the body tube will have air rushing by them during rocket flight. According to Bernoulli’s principle this rushing air will create a low pressure zone at the body tube hole. This in turn will lower the air pressure inside the body tube, wherein the altimeter is located. Since lower air pressure is interpreted as higher altitude, would not this make the altitude reading of the altimeter inaccurate? If the effect I am describing is so small as to be negligible, then could not the same conclusion be drawn about the necessity of the air holes in the first place?
If you are using a gps based altimeter, then the air holes should not needed for that system either.
Am I missing something here?