Add atmosphere addendum source

MEMORY.md

@@ -28,11 +28,17 @@ This file is the durable handoff for AI agents working in this repository. Keep
 - Source docs reviewed:
   - `docs/AERO 3220 3DOF Information Spring 26.pdf`
   - `docs/Atmosphere Model SI Units.pdf`
+  - `docs/Addendum to Atomosphere Model Feb 26.pdf`
   - `docs/Missile and Target Data for 3DOF Spring 26.pdf`
 - Instructor clarification documented on `2026-03-28`:
   - The atmosphere model must be written and integrated into the simulation.
   - The atmosphere implementation must include the stratosphere model for altitude `> 11 km`.
   - The code will not run until the missing `XX` values are replaced with real numbers.
+- Stratosphere model confirmed from `docs/Addendum to Atomosphere Model Feb 26.pdf`:
+  - For `z > 11000 m`, use `T = T0 + lapserate*(11000 - z0)`, so temperature is constant above `11 km`.
+  - Compute `P11k = P0*(T/T0)^(-g/(lapserate*R))`.
+  - Compute `P = P11k*exp(-g*(z - 11000)/(R*T))`.
+  - Then compute `rho = P/(R*T)` and `acousticSpeed = sqrt(gamma*R*T)`.
 - Assignment baseline confirmed from the handout:
   - Velocity pursuit guidance gain = `0.5`
   - Blind range = `2 m`
@@ -54,7 +60,7 @@ This file is the durable handoff for AI agents working in this repository. Keep
 - [`code/Interceptor_3DOF.m`](./code/Interceptor_3DOF.m) drives the integration loop, plotting, and CSV export.
 - [`code/T3dxdt.m`](./code/T3dxdt.m), [`code/M3dxdt.m`](./code/M3dxdt.m), and [`code/getGuidance.m`](./code/getGuidance.m) still contain `XX` placeholders.
 - `getRho.m` is referenced by the driver and both dynamics functions, but the file is missing.
-- Because `getRho.m` does not exist yet, neither the lower-atmosphere branch nor the required stratosphere branch for `z > 11 km` is implemented in the repo.
+- Because `getRho.m` does not exist yet, neither the lower-atmosphere branch nor the addendum-defined stratosphere branch for `z > 11 km` is implemented in the repo.
 - [`code/getMD.m`](./code/getMD.m) exists and computes miss distance at the point of closest approach.
 - The missile/target data PDF appears image-based; a future agent should log the extraction method used when those tables are transcribed.
 
@@ -80,3 +86,4 @@ After any meaningful change, update:
 - `2026-03-28`: Created `README.md` and `MEMORY.md` from the `/docs` PDFs and current MATLAB code. Confirmed the repo is still an incomplete assignment skeleton with unresolved placeholders and a missing `getRho.m`.
 - `2026-03-28`: Documented professor guidance that the atmosphere model must be integrated into the simulation, must include the stratosphere branch for altitude `> 11 km`, and will not run until the `XX` placeholders are replaced.
 - `2026-03-28`: Clarified file roles so `MEMORY.md` is the durable handoff and `TODO.md` is the active execution tracker.
+- `2026-03-28`: Confirmed the stratosphere equations from `docs/Addendum to Atomosphere Model Feb 26.pdf` and recorded the required `z > 11000 m` branch for the future `getRho.m` implementation.

README.md

@@ -6,6 +6,7 @@ Hayden Project is a MATLAB 3DOF interceptor-versus-target engagement simulation
 
 - [`docs/AERO 3220 3DOF Information Spring 26.pdf`](./docs/AERO%203220%203DOF%20Information%20Spring%2026.pdf) defines the assignment, required plots, and evaluation settings.
 - [`docs/Atmosphere Model SI Units.pdf`](./docs/Atmosphere%20Model%20SI%20Units.pdf) provides the SI-unit atmosphere equations for temperature, pressure, density, acoustic speed, and Mach number for the lower-atmosphere branch shown in the handout.
+- [`docs/Addendum to Atomosphere Model Feb 26.pdf`](./docs/Addendum%20to%20Atomosphere%20Model%20Feb%2026.pdf) defines the stratosphere extension for altitudes above `11 km` MSL.
 - [`docs/Missile and Target Data for 3DOF Spring 26.pdf`](./docs/Missile%20and%20Target%20Data%20for%203DOF%20Spring%2026.pdf) is the source packet for the missile and target geometry, propulsion, and drag data that must be transcribed into the simulation.
 
 ## Instructor Clarification
@@ -15,6 +16,7 @@ Per professor guidance documented on `2026-03-28`:
 - The atmosphere model must be written and integrated into the 3DOF simulation.
 - The final atmosphere implementation must include the stratosphere model for altitudes above `11 km`.
 - The source files are intentionally incomplete until the missing `XX` values are replaced with real numbers from the assignment material.
+- The addendum specifies that for `z > 11000 m`, `T` is held constant at the `11 km` value, `P` decays exponentially from `P11k`, `rho = P/(R*T)`, and `acousticSpeed = sqrt(gamma*R*T)`.
 
 ## Assignment Baseline
 
@@ -48,7 +50,7 @@ At the moment, the repository is a partially completed assignment skeleton rathe
 
 - Multiple required values are still marked as `XX`.
 - `getRho.m` is referenced by the code but is not present in the repository, so the atmosphere model has not been integrated yet.
-- When `getRho.m` is added, it must support both the lower-atmosphere branch and the required stratosphere branch for `z > 11 km`.
+- When `getRho.m` is added, it must support both the lower-atmosphere branch and the addendum-defined stratosphere branch for `z > 11 km`.
 - The missile/target data packet still needs to be fully transcribed into MATLAB arrays and constants.
 
 ## Working Expectations

TODO.md

@@ -9,6 +9,7 @@ Last updated: `2026-03-28`
 - [ ] Implement `getRho.m` and include the required stratosphere branch for altitude `> 11 km`.
 - [ ] Fill the known assignment constants in [`code/Interceptor_3DOF.m`](./code/Interceptor_3DOF.m) and [`code/getGuidance.m`](./code/getGuidance.m).
 - [ ] Replace the current syntax-breaking `XX` placeholders that prevent the model from starting in Octave.
+- [ ] Use [`docs/Addendum to Atomosphere Model Feb 26.pdf`](./docs/Addendum%20to%20Atomosphere%20Model%20Feb%2026.pdf) when implementing the `z > 11000 m` atmosphere branch.
 
 ## Blocked