WIP: integrate Missile DATCOM; prediction discrepancies unresolved

CHANGELOG.md

@@ -32,6 +32,7 @@ Attention: The newest changes should be on top -->
 
 ### Added
 
+- ENH: Missile DATCOM sensitivity ascents with a 20% CD floor, larger in-envelope axial-force discrepancies from Wu et al. (2019), and ±2% nose-to-CP distance. Three apogee, speed and stability results include apogee ± the largest scenario excursion. These are engineering assumptions motivated by White (1995), not statistical confidence bounds.
 - ENH: Reproducible Monte Carlo seeding, and an append that continues the same study [#1187](https://github.com/RocketPy-Team/RocketPy/pull/1187) [#1053](https://github.com/RocketPy-Team/RocketPy/issues/1053) [#1075](https://github.com/RocketPy-Team/RocketPy/issues/1075)
 - ENH: 3-DOF single rail button flight phase (tip-off analysis), enabled with the opt-in `Flight(use_udot_rail2=True)`. Between the upper rail button leaving the rail and the lower one following it, the rocket pivots about the lower button under a solved constraint wrench instead of jumping straight to free 6-DOF flight. The window is reported as `between_rails_time`, `between_rails_velocity` and `tip_off_duration`, printed by `Flight.info()` and shaded in the attitude plots. Requires `simulation_mode="6 DOF"` and `equations_of_motion="standard"`. [#920](https://github.com/RocketPy-Team/RocketPy/pull/920)
 - ENH: Support fixed-time parachute deployment triggers [#1133](https://github.com/RocketPy-Team/RocketPy/pull/1133) [#437](https://github.com/RocketPy-Team/RocketPy/issues/437)

README.md

@@ -40,6 +40,11 @@ RocketPy is the next-generation trajectory simulation solution for High-Power Ro
 3. **Aerodynamic Models**
    - Optional Barrowman equations for lift coefficients
    - Easy import of drag coefficients from other sources (e.g., CFD simulations)
+   - Experimental Missile DATCOM integration with nominal, upper and lower
+     coefficient sensitivity flights for apogee, ascent speed and stability.
+     Flight reports show apogee ± the largest scenario departure in meters.
+     [Usage, assumptions and limitations](docs/user/rocket/datcom.rst) and
+     [comparison examples](docs/examples/datcom/README.md).
 
 4. **Parachutes with External Trigger Functions**
    - Test the exact code that will fly
@@ -65,6 +70,41 @@ RocketPy is the next-generation trajectory simulation solution for High-Power Ro
 
 These powerful features make RocketPy an indispensable tool for high-power rocket trajectory simulation, catering to enthusiasts, researchers, and engineers in the field of rocketry.
 
+DATCOM flights include two engineering sensitivity ascents around the nominal
+prediction. Static wind-axis **CD varies by at least ±20% at every Mach and
+AoA**. Within Mach 0.8–3.02 and alpha ±6°, larger axial-force discrepancies
+from Wu et al. are used as a CD-error proxy after converting them to the native
+prediction's denominator; outside that envelope the excursion is 20%.
+**CP varies by ±2% of its distance from the nose**, with static pitching/yawing
+moments transferred consistently. Drag is varied along the airflow, preserving
+perpendicular force; native damping derivatives are retained. These replace
+the earlier independent CN/CM-alpha variations. CP uncertainty is not a
+percentage of stability margin. Both powered and coast tables use this rule.
+
+The reference for the design-accuracy discussion is J. T. White (1995),
+*An assessment of missile DATCOM prediction accuracy relative to generic
+Body+Wing+Tail missile pitch aerodynamics*, AIAA 95-1893,
+[doi:10.2514/6.1995-1893](https://doi.org/10.2514/6.1995-1893).
+White evaluates CN/CP for Mach 1.5–5.0; his cited preliminary-design criteria
+concern normal force and CP relative to body length. **He does not establish
+a universal ±20% CD uncertainty or ±2% nose-to-CP uncertainty.** Applying these
+two percentages throughout rocket flight is an explicit engineering assumption,
+not a result validated by that paper.
+
+The larger drag discrepancies adapt Table 2 of Hanzhou Wu, Min Gao, Weidong
+Song, Zhao Jie and Yi Wang (2019), *Accuracy Analysis of Aerodynamic Calculation
+of Two-dimensional Ballistic correction Projectile based on Missile Datcom*,
+**IOP Conference Series: Materials Science and Engineering 612**, 032096,
+[doi:10.1088/1757-899X/612/3/032096](https://doi.org/10.1088/1757-899X/612/3/032096),
+under [CC BY 3.0](https://creativecommons.org/licenses/by/3.0/).
+
+Printed apogee ± uncertainty is the largest departure from nominal in the two
+correlated scenarios, **not a confidence interval or a guaranteed envelope**.
+The comparison discrepancies remain unresolved. See the
+[method and limitations](docs/user/rocket/datcom.rst) and
+[comparison charts](docs/examples/datcom/README.md). Use
+`Flight(..., datcom_uncertainty=False)` to skip the two extra ascents.
+
 ## Validation
 
 RocketPy's features have been validated in our latest [research article published in the Journal of Aerospace Engineering](http://dx.doi.org/10.1061/%28ASCE%29AS.1943-5525.0001331).

data/rockets/ast_her/README.md

@@ -0,0 +1,23 @@
+# Asteria AST-HER DATCOM example inputs
+
+**Flight status: Asteria / AST-HER has not flown.** All Asteria apogees and trajectories in this example are simulated predictions, not flight measurements or flight validation.
+
+Snapshot from the local `Asteria-Flight-Dynamics` repository on 2026-10-21.
+`configuration.json` merges its current input and visualization JSON files;
+the provenance section records source paths and SHA-256 hashes of data files.
+
+The configured `input/thrust-curves/opt-ThrustCurve.csv` does not exist, so
+`thrust_curve.csv` copies its existing `Optimized_ThrustCurve.csv`. The saved
+atmosphere is for 2026-10-20 15:30 UTC. No network request is necessary.
+
+See `docs/examples/datcom/asteria_comparison.ipynb` for the executed comparison
+of ordinary RocketPy with native DATCOM. Both retain these motor/tank mass and
+inertia inputs and the saved atmosphere. Asteria's supplied ordinary drag curve
+is snapshotted in `docs/examples/datcom/comparison_data/asteria_drag_curve.csv`
+with its hash recorded. The configured ogive tail is native-DATCOM only;
+ordinary RocketPy uses an explicitly noted conical-tail approximation.
+
+The native executable is user supplied. DAMP, powered nozzle-annulus/coast
+full-base drag and adaptive Mach/alpha/Reynolds schedules are used. No Asteria
+hold-down clamp, PROTUB or recovery model is included. AST-HER has not flown;
+these are simulation comparisons, not measured-flight validation.