Demo — Seeker Bench

Demo — Seeker Bench#

A seduction flare is a race against two clocks. One is the intensity clock — the flare must out-shine the target in band before the seeker settles. The other is the geometry clock — the aircraft is flying away from the flare, and once the pair splits the tracking gate the seeker resolves them and holds the real target. This bench puts both clocks on one screen so you can watch the seduction window open and slam shut as you drive the flare’s peak intensity and its rise time.

The two clocks#

Seduction is achieved only while the flare wins the J contest and the pair still fits the gate:

\[ \frac{J_\text{flare}(t)}{J_\text{tgt}} > 1 \qquad\text{AND}\qquad s(t) < g. \]

The flare’s in-band intensity rises then burns down, while the flare–target separation grows as the aircraft flies on and the flare drags behind:

\[ J_\text{flare}(t) = J_\text{pk}\,\bigl(1 - e^{-t/\tau_r}\bigr)\,e^{-t/\tau_b}, \qquad s(t) = v_\text{ac}\,\bigl[\,t - \tau_d\,(1 - e^{-t/\tau_d})\,\bigr]. \]

The gate half-width is the angular gate mapped to range, \(g = R\,\theta_{1/2}\); at \(R = 2\) km and \(\theta_{1/2} = 1.5°\) that is \(g \approx 52\) m. The window runs from \(t_\text{open}\) (flare crosses \(J_\text{tgt}\)) to \(t_\text{close}\) (separation crosses \(g\)).

Interactive demo#

Open in full screen

Walkthrough#

  1. Read the bench. The strip chart below the scene is the J contest — the rise-and-burn curve \(J_\text{flare}(t)\) against the flat \(J_\text{tgt} = 800\) W/sr baseline. The geometry clock plays out in the animated scene: the flare drifts aft of the jet and the live “sep / gate” callout tracks \(s(t)\) against the 52 m gate half-width, while the Seduction-window stat reports \(t_\text{close} - t_\text{open}\) for the current sliders.

  2. Start with the fast flare. With \(J_\text{pk} = 4000\) W/sr and \(\tau_r = 0.1\) s, the flare crosses \(J_\text{tgt}\) at \(t_\text{open}\approx 0.02\) s and the pair splits the gate at \(t_\text{close}\approx 0.73\) s — a window of about 0.7 s.

  3. Raise the peak intensity. Push \(J_\text{pk}\) up and the flare wins the J contest sooner and with more margin, securing the win — but the close barely moves, because gate exit is geometry, not brightness.

  4. Slow the rise time. Stretch \(\tau_r\) toward 1.0 s (10× slower). Watch \(t_\text{open}\) slide right while \(t_\text{close}\) stays put — the window shrinks, and the peak comes out lower because the burn is already decaying while the rise is still climbing.

  5. Find the failure point. Slow the rise far enough and \(t_\text{open}\) meets \(t_\text{close}\): the flare never wins the contest before the pair leaves the gate. Seduction fails with the magazine spent.

Key observations#

  • Seduction needs both clocks to agree. Winning the J contest is necessary but not sufficient; the pair must still share the gate. The window is the overlap, and it is short — under a second here.

  • Gate exit is set by geometry, not the flare. \(t_\text{close}\) is fixed by \(v_\text{ac}\), drag, and the gate half-width. That is why every second lost to a slow rise comes straight out of the window.

  • Rise time is a KPP — and a liability. A fast rise opens the window early, but a signature that jumps to peak in a fraction of a second is exactly what the IRCCM intensity cue is built to flag. The same knob helps seduction and betrays it.

  • This is a reticle-seeker story. An imaging Band IV seeker watches the two objects separate and keeps tracking the aircraft shape — no amount of \(J_\text{pk}\) out-shouts a sensor that sees shapes, which is the setup for Project 3.

Source#

MATLAB bundle · L24_FlareSeduction.m↓

The companion script builds the fast-flare intensity and separation curves, prints the 52 m gate half-width and the ~0.7 s fast-flare window, then swaps in a 10×-slower rise (\(\tau_r = 1.0\) s) to show the window shrink and the peak drop — the same knobs the sliders drive here.

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