Density altitude and applied ballistics

In summary, the conversation discusses the relationship between air temperature, density altitude, and the flight of a bullet. The speaker is struggling to understand the pattern on a chart that shows the effect of temperature on elevation. They also inquire about the role of altitude, barometric pressure, and humidity in air density. The expert summarizer explains that density altitude is affected by air pressure, temperature, and humidity, with decreased air pressure, increased temperatures, and increased moisture resulting in lower air density. They suggest using an online calculator to determine density altitude, which requires inputting air temperature, dew point temperature, pressure, and elevation.
  • #1
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Hello, I am struggling with understanding air temperatures effect on density altitude and it's effect on the flight of a bullet. I understand that as temp goes up air resistance/density goes down but in looking at a chart I have I can’t seem to make out a pattern in relation to temp.

It appears that at some points on the chart a 10deg change in temp makes a 500’ shift in elevation one way but 10deg shift in the opposite direction can be 1000’ shift.

How do altitude/barometric pressure relate with temp in overall air density? Is this shift I am seeing in the chart, is it related to how water vapor/humidity is acting in those temp/baro conditions?

Thanks in advance for helping an ex-army grunt understand…..
 
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  • #2
I don’t know what chart you are looking at, but density altitude depends on the air pressure, temperature and humidity. Decreased air pressure, increased temperatures and increased moisture reduce the density of the air. You can usually ignore moisture,

There are rules of thumb to determine density altitude, but the easiest way is to use an online calculator. You need to know you altitude and obtain the weather. For the calculator below you need air temperature, dew point temperature (for moisture), your pressure and elevation. Note: The calculator uses mb for pressure and your pressure may given in kPa.. To convert simply drop the decimal ie 102.0 kPa is 1020 mb.

http://www.pilotoutlook.com/calculators/density-altitude-calculator
 
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1. What is density altitude and how does it affect ballistics?

Density altitude is the altitude at which the air density would be the same as the actual air density at a given location. This means that at higher altitudes, where the air is less dense, the density altitude will be higher. Density altitude can affect ballistics because air density plays a significant role in determining the aerodynamic drag and flight characteristics of a projectile.

2. How is density altitude calculated?

Density altitude is calculated using a combination of temperature, altitude, and atmospheric pressure. The formula for calculating density altitude is: DA = PA + [120 x (OAT - ISA Temp)], where DA is density altitude, PA is pressure altitude, OAT is outside air temperature, and ISA Temp is the standard atmosphere temperature at a given altitude. There are also online calculators and smartphone apps available for easy calculation.

3. Why is density altitude important in applied ballistics?

Density altitude is important in applied ballistics because it directly affects the performance of a projectile. As density altitude increases, the air becomes less dense, causing a higher trajectory and reduced velocity of the projectile. This can result in missed targets or decreased accuracy if not accounted for in ballistic calculations.

4. How do you adjust for density altitude in applied ballistics?

The most effective way to adjust for density altitude in applied ballistics is to use a ballistic calculator or computer program. These tools take into account the density altitude, along with other factors such as wind and bullet characteristics, to calculate the trajectory and impact point of a projectile. Some advanced ballistic calculators also allow for manual adjustments to be made for density altitude.

5. How can density altitude affect shooting at long ranges?

At long ranges, even small changes in density altitude can have a significant impact on the trajectory and impact point of a projectile. As the density altitude increases, the air becomes less dense, causing the projectile to experience more drag and drop faster. This can result in missed shots or decreased accuracy if the density altitude is not properly accounted for in ballistic calculations.

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