Entry Ballistic Coefficient
Compute the mass-to-drag-area ballistic coefficient from supplied aerodynamic reference quantities.
Description
Ballistic coefficient compares spacecraft mass with its effective drag area.
Ballistic coefficient compares spacecraft mass with its effective drag area. It has mass-per-area units and depends on the chosen aerodynamic reference area and drag coefficient.1
Compute the mass-to-drag-area ballistic coefficient from supplied aerodynamic reference quantities.
When to use Entry Ballistic Coefficient
Use this tool to compute the mass-to-drag-area ballistic coefficient from supplied aerodynamic reference quantities.
Prepare the orbital state or model parameters in one reference frame. Confirm compatible distance/time units and the stated angular and gravitational-parameter conventions.
How to use Entry Ballistic Coefficient and understand its results
- Prepare the orbital state or model parameters in one reference frame. Confirm compatible distance/time units and the stated angular and gravitational-parameter conventions.
- Enter spacecraftKg, dragCoefficient, referenceAreaSquareMeters using the field table and calculation rules, then run the tool.
- Read ballisticKgPerSquareMeter. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| spacecraftKg | Spacecraft kg | number | Required |
| dragCoefficient | Drag coefficient | number | Required |
| referenceAreaSquareMeters | Reference area square meters | number | Required |
Enter positive spacecraft mass in kg, dimensionless drag coefficient and reference area in m². The tool divides mass by their product and returns kg/m². The coefficient and area must refer to the same aerodynamic convention.
ballisticCoefficient = mass/(dragCoefficient × referenceArea) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| ballisticKgPerSquareMeter | Ballistic kg per square meter | number |
{
"input": {
"spacecraftKg": 100,
"dragCoefficient": 2,
"referenceAreaSquareMeters": 5
},
"output": {
"ballisticKgPerSquareMeter": 10
}
}Limitations and assumptions
It does not determine drag coefficient from speed or geometry or predict an entry trajectory. Attitude, changing area, heating and aerodynamic uncertainty are not modeled.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Exponential Entry Peak Deceleration: Evaluate the constant-flight-path, drag-only Allen–Eggers exponential-atmosphere peak-deceleration approximation; lift and changing entry angle are neglected. For a complementary task, use Drag Stationkeeping Impulse: Estimate drag make-up impulse from a constant environment and supplied orbit duty factor; density variation and maneuver losses are not modeled.
References
-
Entry Ballistic Coefficient — tool.io
Similar or alternative tools
- Exponential Entry Peak Deceleration
Evaluate the constant-flight-path, drag-only Allen–Eggers exponential-atmosphere peak-deceleration approximation; lift and changing entry angle are neglected.
- Drag Stationkeeping Impulse
Estimate drag make-up impulse from a constant environment and supplied orbit duty factor; density variation and maneuver losses are not modeled.