Object’s speed and its heating temperature

In summary, the conversation discusses the heating of objects such as asteroids, aircraft, and spaceships as they enter Earth's atmosphere at high velocities. The faster the object moves and the denser the atmosphere, the more it heats up. The question is raised whether it is possible to predict or calculate the heating temperature of an object moving at a specific speed and altitude. It is suggested that the drag coefficient for the object can be used to estimate the heating power caused by friction. A link to an online calculator for a flat plate is provided, along with information about the SR-71 and X-15 programs. The conversation also touches on the calculations for imperfect gas and limitations of the derived results.
  • #1
Eagle9
238
10
When some certain object (asteroid, aircraft, spaceship and etc.) moves at great velocities into Earth’s atmosphere it heats. The faster its moves and the denser is the atmosphere the heater this certain object becomes. This is simple is clear. Now, is it possible somehow to predict or calculate this heating temperature? For instance, the object moves at the speed of 975 meter/sec at the altitude of 80 km above the sea level, can we calculate its heating temperature? Are there some formulas in Physics or ready-made charts/diagrams for this purpose? I need this data for the altitude of 0-160 km above the see level…:wink:
 
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  • #2
No easly calculation: it is specific to the geometry (and other properties) of the object.
 
  • #3
russ_watters said:
No easly calculation: it is specific to the geometry (and other properties) of the object.

Well, let’s assume that it is long tube with the diameter of 5 meters, now it could be calculated?:wink:
 
  • #4
You might be able to get a rough estimate by looking at the drag force. The drag is caused by several things, but friction is one, and that is what causes the heating. Force time velocity gives your heating power. So, you need to look up the drag coefficient for the object in question.
 
  • #5
kcdodd said:
You might be able to get a rough estimate by looking at the drag force. The drag is caused by several things, but friction is one, and that is what causes the heating. Force time velocity gives your heating power. So, you need to look up the drag coefficient for the object in question.

So, if I understood correctly I need to find the drag coefficient? And where is it possible to find it? Are there some ready-made charts?
 
  • #6
Look for: skin friction coefficient, supersonic drag, slender body

Here is an online calculator for a flat plate(link at bottom of the page):
http://adg.stanford.edu/aa241/drag/skinfriction.html

The drag for given air density, velocity, surface area, friction coefficient is:

[tex]D = 0.5 \rho v^{2} S C_{f}[/tex]

Just to get an idea:
The SR-71 has surface temperatures above 300 degrees celsius at 980m/s(MACH 3.2) and 24km height.

Edit:
You might try to find some surface temperature data from the X-15 program.
 
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  • #8
nucleus said:

Ok, thank you very much, I think this is what I wanted :smile:. However, I would like to specify some issues since I am not physicist and sometimes it is a bit difficult for me to understand some problems in this science.
First of all, here is the illustration what I actually wanted to know. Imagine a long and thin rod is rotating in the atmosphere with various angles of attack. I want the result for the situation when this rod has got almost vertical position-70°, 80° or 90°.
http://img576.imageshack.us/i/engd.gif/


Frankly saying I do not know properties of which gas (calorically perfect gas or calorically imperfect gas) should be calculated for the real Earth’s atmosphere. As I know perfect gas does not exist in the nature at all, therefore I need to measure property of imperfect gas, right? I read the information presented in the web-link given by you. If I understood everything correctly I need the Total Temperature calculated in the Java calculator, right? So, as an example, I put the following values: the object moves in the atmosphere at the altitude of 80 000 meters (by the way after the calculation this value for some reason was decreased to 76 200 meters) at the speed of 975 meters/sec. After computations I saw the following result: Total Temperature is equal to 646 Kelvin degrees (for imperfect gas). Is it right? So, this object would be heated to the temperature of 646 degrees?
http://img504.imageshack.us/img504/8301/calculatoru.jpg

I have actually got one more question. For which altitudes this derived result (646 degrees K) is correct? For the whole section of the atmosphere from the seal level to the altitude of let’s say 150 km above the sea level? Or there are some limitations?
 
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  • #9
log0 said:
Look for: skin friction coefficient, supersonic drag, slender body

Here is an online calculator for a flat plate(link at bottom of the page):
http://adg.stanford.edu/aa241/drag/skinfriction.html

The drag for given air density, velocity, surface area, friction coefficient is:

[tex]D = 0.5 \rho v^{2} S C_{f}[/tex]

Just to get an idea:
The SR-71 has surface temperatures above 300 degrees celsius at 980m/s(MACH 3.2) and 24km height.

Edit:
You might try to find some surface temperature data from the X-15 program.
Ok, thank you very much, I will take look at it :smile:
 
Last edited by a moderator:

Related to Object’s speed and its heating temperature

1. What is the relationship between an object's speed and its heating temperature?

The relationship between an object's speed and its heating temperature is directly proportional. This means that as the object's speed increases, its heating temperature also increases. Similarly, as the object's speed decreases, its heating temperature decreases as well.

2. How does air resistance affect an object's speed and heating temperature?

Air resistance can have a significant impact on an object's speed and heating temperature. As an object moves through the air, it experiences friction from the air molecules, which slows it down and causes it to heat up. This is why objects such as spacecrafts have heat shields to protect them from the high temperatures caused by air resistance during re-entry into the Earth's atmosphere.

3. Can an object's shape affect its speed and heating temperature?

Yes, an object's shape can affect its speed and heating temperature. Objects with a streamlined shape, such as a bullet or a rocket, experience less air resistance and can therefore travel faster and generate less heat compared to objects with a less aerodynamic shape.

4. How does the material of an object affect its heating temperature?

The material of an object can have a significant impact on its heating temperature. Materials with a higher thermal conductivity, such as metals, can conduct heat away from the object more efficiently, resulting in a lower heating temperature. On the other hand, materials with a lower thermal conductivity, such as wood or plastic, can trap heat and cause the object to heat up more quickly.

5. Is there a maximum speed at which an object can travel without heating up?

No, there is no maximum speed at which an object can travel without heating up. However, as an object approaches the speed of light, its mass increases and the energy required to accelerate it further also increases. This means that the object would require an infinite amount of energy to reach the speed of light, making it practically impossible to do so.

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