Powered Flyby Velocity Budget
Budget a local powered-flyby velocity vector change and specific kinetic-energy change from supplied periapsis speeds and angle; no B-plane trajectory is solved.
Description
A powered flyby can change both the magnitude and direction of local periapsis velocity.
A powered flyby can change both the magnitude and direction of local periapsis velocity. Vector impulse and kinetic-energy change describe different aspects of that local maneuver.1
Budget a local powered-flyby velocity vector change and specific kinetic-energy change from supplied periapsis speeds and angle; no B-plane trajectory is solved.
When to use Powered Flyby Velocity Budget
Use this tool to budget a local powered-flyby velocity vector change and specific kinetic-energy change from supplied periapsis speeds and angle; no B-plane trajectory is solved.
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 Powered Flyby Velocity Budget 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 incomingPeriapsisSpeed, outgoingPeriapsisSpeed, burnDirectionAngleDegrees using the field table and calculation rules, then run the tool.
- Read localVelocityChange, specificKineticEnergyChange. 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 |
|---|---|---|---|
| incomingPeriapsisSpeed | Incoming periapsis speed | number | Required |
| outgoingPeriapsisSpeed | Outgoing periapsis speed | number | Required |
| burnDirectionAngleDegrees | Burn direction angle degrees | number | Required |
Enter nonnegative incoming and outgoing periapsis speeds in matching units and their direction angle in [0,180] degrees. The tool uses the cosine law, clips a negative roundoff radicand to zero, and returns impulse magnitude plus signed specific kinetic-energy change in squared speed units.
deltaV² = vIn²+vOut²−2vIn vOut cos(angle); deltaEnergy = (vOut²−vIn²)/2 Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| localVelocityChange | Local velocity change | number |
| specificKineticEnergyChange | Specific kinetic energy change | number |
{
"input": {
"incomingPeriapsisSpeed": 3,
"outgoingPeriapsisSpeed": 4,
"burnDirectionAngleDegrees": 90
},
"output": {
"localVelocityChange": 5,
"specificKineticEnergyChange": 3.5
}
}Limitations and assumptions
This does not solve B-plane geometry, a physical flyby path or heliocentric energy. Periapsis clearance, force duration and achievable directions are not inferred.
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 Gravity Assist Velocity Rotation: Rotate a planet-frame excess-velocity vector and transform it back to the heliocentric frame under an ideal unpowered flyby. For a complementary task, use Hyperbolic Capture Insertion: Calculate an aligned impulsive periapsis capture burn from a hyperbolic arrival to a specified elliptic orbit, excluding plane changes.
References
-
Powered Flyby Velocity Budget — tool.io
Similar or alternative tools
- Gravity Assist Velocity Rotation
Rotate a planet-frame excess-velocity vector and transform it back to the heliocentric frame under an ideal unpowered flyby.
- Hyperbolic Capture Insertion
Calculate an aligned impulsive periapsis capture burn from a hyperbolic arrival to a specified elliptic orbit, excluding plane changes.