No new theory today. Your group is the B-21 design cell, and the period belongs to Project 3: given a fixed budget, choose the signature-management package that makes the B-21 hardest to find — across radar, IR, and the rest — against a three-band threat that will not let you hide in every band at once.
## The ask Recommend a **prioritized signature-management package** for the B-21 that minimizes the range at which it is detected, under a fixed budget, against a mixed threat. Everything you need is Block 3: the fourth-power RCS law (L25–L26), the passive IR range rule (L23), radar-absorbing material (L27), and the multi-spectral fusion rule from L28 — detection is a union, so the range that matters is the **loudest band**, $R_\text{det} = \max_b R_b$. ## The threat mix Three threats, each with its own detection law and reference point: | Threat | Band | Detection law | Reference | | --- | --- | --- | --- | | VHF surveillance | low-band radar | $R = 90\,(\sigma_\text{VHF}/2.0)^{1/4}$ | 90 km at 2 m² | | X-band fire-control | high-band radar | $R = 45\,(\sigma_\text{X}/0.03)^{1/4}$ | 45 km at 0.03 m² | | IR MANPADS | infrared | $R = \min\!\big(8\sqrt{J/300},\ 6\big)$ | 8 km at 300 W/sr, lethal to 6 km | At baseline the B-21 is found at **≈ 90 km — the VHF surveillance radar is the loudest band.** DIRCM drives the MANPADS range to zero, but it costs a slot. ## The method Signature → detection → loudest band. Apply your package's decibel cuts to each band's signature, recompute the three ranges, and take the maximum — that is where you are found. Then attack *that* band, and expect the limiter to move. ## The budget — and the tension Every investment on the menu costs against two caps: **total cost ≤ 10** and **total weight ≤ 5**. The tension is the whole project: **VHF is the limiter, but X-band RAM barely touches it** — a decibel poured into the wrong band buys nothing. The low-band levers that actually move VHF are the heavy, expensive ones, and the budget cannot buy everything. Find the package that spends *at the limiter* and reaches the lowest $R_\text{det}$ you can. ## Your tasks 1. **Score the baseline** — the three ranges and the loudest band, before any investment. 2. **Model the menu** — apply each investment's dB effects; verify against the starter. 3. **Search the budget** — find a package within cost ≤ 10 and weight ≤ 5 that minimizes $R_\text{det}$. 4. **Chase the limiter** — show which band limits at each step and where it jumps. 5. **Aspect (bonus)** — nose-on ingress versus tail-on egress: who sees you, and when. 6. **Recommendation** — one slide: the package, its $R_\text{det}$, and why it beats the obvious buy. ## Materials Work the [pre-flight](L29_Preflight.md) before class — anyone can be called to the board. Lesson slides (PDF) Project 3 handout (PDF) B21_SignaturePattern.csv SignatureMenu.csv MATLAB bundle · L29_Project3Starter.m↓ The starter reads `B21_SignaturePattern.csv` and `SignatureMenu.csv`, scores the baseline and one example package (X-band RAM + plume suppression) against the three threats, and shows the fourth-power trade — the plumbing, so your group starts at the trade study, not the file I/O. Extending it to the full menu, a budget search, and an aspect sweep is the job. The interactive **[Project 3 dashboard](Project3.md)** lets you explore packages before you write any code. (Both CSVs are bundled in the code zip beside the starter, which reads them from the current folder.) ## How to use the work day - **First 10 minutes** — groups assigned; read the handout together and score the baseline by hand. - **Next 30 minutes** — divide the work: menu model, budget search, aspect view, recommendation. - **Last 10 minutes** — regroup: best package so far, what's blocked, who owns what before L30. Plan the recommendation first — it tells you what to compute. Next lesson: **L30 — Project 3 presentations.** Slides and code due before class, HW3 due at the start of class, and Quiz 3 in class.