Mass of projectile (m)
lb
Area of cross-section (A)
in²
Drag coefficient (C)
Ballistic Coefficient (B)
lb/in²

The ballistic coefficient calculator will assist you in calculating the ballistic coefficient of a projectile. A projectile can be any object such as a ball, flying disk, or a bullet shot from a gun. The ballistic coefficient of a projectile depends on factors such as its mass and cross-sectional area. Along with various parameters like time of flight, height, range, and trajectory, this parameter is used in physics to estimate the behavior of projectile mid-air in the field which is known as the external ballistics.

The parameter also has significance in the area of space vehicle re-entry, therefore is considered important while designing these systems. Read onto understand how to calculate ballistic coefficient.

What is ballistics?

Before we understand ballistic coefficient, let us have a look at ballistics as a field. Depending on what a projectile faces, there are three types of subfields in the area of ballistics, which are:

  • Internal ballistics — this field covers the time when a bullet is inside a muzzle, i.e., the propulsion phase of a projectile.
  • External ballistics — one the bullet or a projectile leaves the launcher, its interaction midair against various forces of nature such as gravitation or air resistance and throughout its trajectory.
  • Terminal ballistics — once the projectile reaches towards its end of the trajectory, it most likely collides with an object, say a bullet piercing a target or a ball hitting a wall. The interaction between the projectile and its target as well as the effect on both object is covered by terminal ballistics.

What is ballistic coefficient?

The ballistic coefficient falls under the premise of external ballistics and is regarded as the property of an object to overcome air resistance while traveling. For a projectile weighing m kg and having drag coefficient C, the ballistic coefficient B can be written as:

B = m / (C * A),

where A is the area of cross-section of the projectile. The ballistic coefficient is measured in the units kg/m2 or lbs/in2. There are 7 different mathematical models for ballistics named G1 to G7. The G1 model is the most popular and is used for flat base and ogive nose projectiles. The ballistic coefficient related to the G1 model is also known as G1 ballistic coefficient.

How to calculate ballistic coefficient using this calculator?

Follow the steps below to calculate ballistic coefficient:

  • Step 1: Enter the mass of the projectile, m.
  • Step 2: Insert the area of cross-section, A.
  • Step 3: Fill in the drag coefficient, C.
  • Step 4: The calculator will then return the ballistic coefficient.

Using the ballistic coefficient calculator

Estimate the ballistic coefficient for a round projectile weighing 50 grams having a diameter 13 mm. Take drag coefficient as 0.51.

To prepare for the input first let's calculate the area of cross-section, considering a circular cross-section. The area can be calculated as:

A = π * D2/ 4 = π * 132/4 = 132.73 mm2
You can either use the formula above or can try our dedicated area of circle calculator. Now let's find out the value of coefficient.
  • Step 1: Enter the mass of the projectile, m = 50 g.
  • Step 2: Insert the area of cross-section, A = 132.73 mm2.
  • Step 3: Fill in the drag coefficient, C = 0.51.
  • Step 4: The ballistic coefficient for the projectile is:
B = m / (C * A) = 738.645 kg/m2= 1.0506 lbs/in2

The ballistic coefficient for the projectile is 1.0506 lbs/in2. The bullet is one of the low drag projectiles. The higher the value of ballistic coefficient, the lower the negative acceleration.

Applications of ballistic coefficient

Did you know?

  • For a reentry vehicle from space, it would be desired to have a low coefficient so that it can decelerate quickly causing a softer impact with the ground.

  • However, reentry projectiles like Intercontinental Ballistic Missiles (ICBM) or long range ammunition rounds are designed with higher ballistic coefficient to ensure the least interference of crosswinds and reach the target quickly with higher kinetic energy.

  • The low Earth orbit (LEO) satellite EYESAT-I has a ballistic coefficient of about 0.072 lbs/in2. EYESAT-I is a cubical amateur satellite weighing about 11.8 kg. Whereas, a 0.50 caliber low drag bullet has a ballistic coefficient of 1.062 lbs/in2.

FAQ

What is ballistic coefficient?

Ballistic coefficient is the property of a projectile to withstand air resistance mid-flight.

How do I calculate ballistic coefficient?

To calculate ballistic coefficient:

  1. Multiply the drag coefficient C of the projectile with its area of cross-section A.
  2. Find the inverse of the product.
  3. Multiply the mass m with the inverse.
B = m / (C * A)

What are the units for ballistic coefficient?

Ballistic coefficients are measured in the units - lbs/in2 or kg/m2.

Should ballistic coefficient be high or low?

The ballistic coefficients for satellites are designed to be very low to slow it down and cause minimal damage while reentering the atmosphere. On the other hand, the coefficient for a bullet is kept high to ensure minimal interference from atmosphere.

Rahul Dhari
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