Lesson 24 Flashcards#
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1. What are the four ways to attack an IR seeker's optical track?
Starve it (reduce signature \(J\) so the track never starts — suppression), clutter it (competing sources — flares/decoys), deceive it (inject false info into the tracker — seduction/DIRCM), and damage it (overload or destroy the detector with directed energy).
2. In one line, what is the real target of every IRCM move?
Not the missile itself but the missile's information — the data the seeker uses to track. Break the data and the weapon flies at nothing.
3. State the condition under which a seduction flare beats a reticle seeker.
While \(J_\text{flare}/J_\text{tgt} > 1\) with margin and the flare and target still both fit inside the seeker's tracking gate. Both must hold at once.
4. What is the "seduction window"?
The overlap in time when the flare out-shines the target (J contest won) and the pair still shares the tracking gate — from \(t_\text{open}\) (flare wins J) to \(t_\text{close}\) (gate exit).
5. Write the flare rise-and-burn intensity model.
\(J_\text{flare}(t) = J_\text{pk}\,(1 - e^{-t/\tau_r})\,e^{-t/\tau_b}\): it rises with time constant \(\tau_r\) and burns down with \(\tau_b\). A fast rise (small \(\tau_r\)) wins the J contest almost immediately.
6. How does seduction differ from distraction and dilution?
Seduction is post-lock — it drags the gate off an already-tracking missile. Distraction puts decoys out before lock so the seeker acquires a flare. Dilution presents many credible targets at once so the shooter must engage them all.
7. Name the three IRCCM cues that reject a conventional flare and what each looks for.
Trajectory (the flare decelerates and falls away, unlike an aircraft), spectral (a ~2000 K flare is far hotter than a tailpipe, so its two-color ratio is wrong), and intensity (the signature jumps to peak in a fraction of a second, faster than any real change).
8. What does a seeker do when any IRCCM cue trips?
It freezes the gate on the original track and ignores the newcomer (the flare). Any one tell is enough to trip the logic.
9. Why is a flare spectrally distinguishable from a jet tailpipe?
An MTV flare burns near 2000–2200 K (Wien peak ~1.4 µm) while a tailpipe is ~800 K (~3.6 µm); the color / two-color-ratio mismatch flags the flare as too hot, too blue.
10. Why is flare rise time a KPP?
Gate exit \(t_\text{close}\) is fixed by geometry, not the flare, so every second a slow rise takes to win the J contest comes straight out of the seduction window — and a fast jump is also exactly what the IRCCM intensity cue watches for.
11. Against which threat bands are flares effective versus limited?
Effective against older Band I/II reticle seekers; limited against modern Band IV imaging / two-color seekers.
12. Why does an imaging (Band IV) seeker beat conventional flares?
It tracks a shape, not the brightest pixel. When a flare separates, the seeker sees two objects and keeps tracking the one shaped like an aircraft — you cannot out-shout a seeker that can see shapes.
13. How does a DIRCM system defeat an IR seeker, and how does it improve on lamp jammers?
A missile warning system detects launch and cues a turret; a modulated laser (AN/AAQ-24 class) shines into the seeker's optics to inject false tracking error and force optical break lock. Earlier lamp jammers (ALQ-144 class) radiated blindly and continuously; lasers add power, precision, and tailoring.
14. How does design-level signature suppression attack \(J\), and what is its payoff?
Plume mixing/nozzle shaping, burying and masking hot parts, and low-emissivity skin cut in-band \(J\). By \(R_\text{max} \propto \sqrt{J}\) this shrinks every seeker's detection and launch range before any engagement — an always-on IRCM, baked into airframes like the B-21.
15. In the demo, what seduction window does the fast flare achieve and what sets its end?
About 0.7 s: the flare wins the J contest at ~0.02 s and gate exit occurs at ~0.73 s (a 52 m gate half-width at 2 km / 1.5°). The exit is set by geometry, not the flare.