---
title: Flight: hull, engines and thrusters
summary: Thrust, boost, travel, braking and steering: locate the settings and change one variable at a time.
section: ships
kind: guide
status: reference
updated: 2026-10-27
tags: ["X4","modding","ship","flight"]
sources: ["https://wiki.egosoft.com/X4%20Foundations%20Wiki/Modding%20Support/Assets%20Modding/Guides/JPMFlight/","https://wiki.egosoft.com/X4%20Foundations%20Wiki/Modding%20Support/Breaking%20Changes/"]
---
## Three sets of parameters


The hull defines mass and motion response. Engines define longitudinal thrust and `boost/travel` modes. Thrusters define lateral thrust and rotation. Resulting speed belongs to the selected combination of hull and equipment.



Table paths start inside the properties of the relevant macro. Parameter meanings were checked against [Flight Parameter Setup, Daniel Turner](https://wiki.egosoft.com/X4%20Foundations%20Wiki/Modding%20Support/Assets%20Modding/Guides/JPMFlight/). The guide includes 7.50 notes; distinguish a field found in 9.00 from its active runtime behavior.



## Engine: thrust and modes


| Path | Type / units | Meaning |
| --- | --- | --- |
| `thrust/@forward`, `thrust/@reverse` | Numeric thrust parameters | Forward and reverse thrust; not speed in metres per second |
| `boost/@duration` | Number, seconds | Boost duration from full boost capacity |
| `boost/@thrust` | Dimensionless multiplier | Base-thrust amplification during boost |
| `boost/@acceleration` | Dimensionless multiplier | Boost acceleration amplification; separate from thrust |
| `boost/@release` | Number, seconds | Coasting interval after boost before amplified braking |
| `boost/@coast` | Dimensionless multiplier | Deceleration adjustment during the release interval |
| `travel/@charge` | Number, seconds | Delay before travel mode engages |
| `travel/@thrust` | Dimensionless multiplier | Base-thrust amplification in travel mode |
| `travel/@attack` | Number, seconds | Time to reach maximum travel speed according to the guide |
| `decelerationcurve/point` | `Position/value` pairs | Longitudinal braking amplification curve |
| `strafecurve/point` | `Position/value` pairs | Lateral deceleration curve across speed regimes |


`travel/@release` still exists in the inspected 9.00 engine macro, but the guide marks that braking control as deprecated. Attribute presence alone does not establish an effect; inspect reverse thrust and braking curves.



## Thrusters and hull


| Location | Parameter | Effect |
| --- | --- | --- |
| Thruster macro | `thrust/@strafe` | Lateral thrust |
| Thruster macro | `thrust/@pitch`, `@yaw`, `@roll` | Rotational thrust: pitch, yaw and roll |
| Hull macro | `physics/@mass`, `physics/inertia`, `physics/drag` | Mass, inertia and resistance by axis |
| Hull macro | `physics/accfactors` | Acceleration multipliers for individual directions |
| Hull macro | `jerk` | Smoothing when acceleration rises or falls |
| Hull macro | `steeringcurve/point` | Steering-speed multiplier across speed regimes |


In jerk, `accel/decel` and value control smoothing; ratio changes the transition shape. These are neither seconds nor thrust. Curve value is a multiplier; position identifies regular, boost or travel speed regions. position="2" does not mean 2 metres per second; the upper regimes depend on their maximum speeds.



## Example: only the selected engine thrust


For `engine_arg_s_allround_01_mk1_macro`, the 9.00 base forward value is 384. Patch file: `assets/props/Engines/macros/engine_arg_s_allround_01_mk1_macro.xml.`



```xml
<diff>
  <replace sel="/macros/macro[@name='engine_arg_s_allround_01_mk1_macro']/properties/thrust/@forward">422.4</replace>
</diff>
```



Expected data result: forward thrust rises by 10%; reverse thrust and other fields remain unchanged. This does not promise exactly 10% more speed or acceleration in every mode. The shared engine resource changes, so the scope is not limited to one `Elite`.



replace writes the absolute value 422.4; it does not multiply the current value by 1.1. If another mod changes the engine, compare the effective XML and load order.



## One reproducible comparison


Record the hull, engine, thruster and in-game modifications. On a new instance, measure regular speed, acceleration, boost, travel charging, braking and turning. Change one field and repeat the same actions in the same place. XML values were checked by reading; this example has not been run as a new game test.



For a change limited to one hull variant, first choose the scope: [hull properties](wiki:ship-properties) or a separate equipment resource. Do not change slot sizes to tune speed: see [equipment compatibility](wiki:ship-equipment).