L29 — Project 3 Work Day#
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#
Score the baseline — the three ranges and the loudest band, before any investment.
Model the menu — apply each investment’s dB effects; verify against the starter.
Search the budget — find a package within cost ≤ 10 and weight ≤ 5 that minimizes \(R_\text{det}\).
Chase the limiter — show which band limits at each step and where it jumps.
Aspect (bonus) — nose-on ingress versus tail-on egress: who sees you, and when.
Recommendation — one slide: the package, its \(R_\text{det}\), and why it beats the obvious buy.
Materials#
Work the pre-flight before class — anyone can be called to the board.
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 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.