Urban search and rescue after an earthquake.

The mission

An international USAR contingent reaches the city thirty hours after the earthquake. The base of operations goes up at a stadium on the edge of the damage; sectors are assigned; teams move into the collapse zone with search cameras, listening devices and dogs. Everything the teams produce — worksite triage marks, structural assessments, photographs, above all the location of every live find — must reach the base, and through it the coordination cell that assigns cranes, medics and the next team. Between the worksites and the base lies a city whose communications infrastructure collapsed with its buildings.

What breaks

The urban network dies at every layer at once: towers come down with the structures that carried them, the grid goes dark, and the buried backhaul is cut in a hundred places. Whatever survives at the edges of the city is instantly saturated by a population trying to find its families. And even a working radio has to fight the terrain the earthquake made — streets of steel and concrete rubble that block line of sight within a block, teams working in courtyards, voids and basements that no signal leaves directly.

The classical fallbacks are known and painful. Runners carry paper between worksites and base — slow, and the form arrives after the crane was assigned elsewhere. Voice-only VHF relays what a voice can say, which is not a structural assessment, a photograph or a grid reference read under stress. A satellite terminal per team is weight, cost and a sky view the urban canyon frequently denies. Coordination degrades to shouting distance exactly when a dozen teams from several countries most need one picture.

The architecture on this mission

The contingent brings its network in with it. Every team kit, every vehicle and the drone overhead runs the same software node; nodes authenticate by key and self-form one encrypted mesh the moment they power on — no server, no controller, no configuration ceremony on a rubble pile. Traffic finds the base over however many hops the ruins require, up to eight: a kit deep in a shadowed courtyard reaches a vehicle parked at the corner, the vehicle reaches the drone holding overhead, the drone reaches the base. When a team moves and the geometry changes, routes re-form on their own; a vanished hop is detected and routed around in about a second.

The base’s satellite terminal is the single expensive asset, and the mesh makes it everyone’s: one shared uplink to the national coordination cell, reached from any worksite in the sector. Traffic is classed so the uplink and the thin hops are spent in the right order — victim locations and tasking first, assessments and photographs next, everything else after. And because teams routinely work beyond every hop for an hour at a time, findings travel store-carry-forward: they queue on the kit, survive the gap, and deliver in priority order at the next contact. Between contingents from different countries there is a quieter property that matters: every hop is separately encrypted, and a relay cannot read the traffic it carries — one team’s node can forward another team’s findings without either seeing the other’s data. Keys rotate automatically every two minutes, with zero packets lost in the swap.

How the deployment unfolds

1. Arrival, hour thirty. The base stands up at the stadium; the satellite dish and the base node come up together. Team kits join the mesh by key as they are switched on — the network exists before the first team leaves the gate.
2. Sectors assigned. Teams move into the collapse zone; vehicles parked at corners become waypoint relays without anyone designating them; the drone climbs over the sector as the high hop that stitches the shadowed worksites together.
3. A team goes deep. Three blocks in, behind a pancaked apartment building, the direct path to base is gone. The kit’s traffic re-routes over the vehicle and the drone automatically — the team never stops to think about the network, which is the entire measure of success.
4. The find. A listening device confirms a live victim. The location and the worksite assessment cross the mesh in the top class, reach the base and go out over the satellite to the coordination cell — while a team working out of reach on the far edge queues its own findings for the next contact.
5. Shift change. The drone lands for batteries, teams rotate, vehicles move. The mesh re-forms on the new topology in seconds; nobody re-establishes anything, and the queued findings from the far edge deliver the moment a hop appears.
6. The record. The journal holds who was reachable, when, over which hops — a timestamped connectivity record of the deployment that feeds the after-action review and the next mission’s load-out decisions.

What each mechanism contributes

• Self-forming mesh join — kits, vehicles and the drone become one network by being switched on; key-based authentication, no infrastructure, no ceremony. Shipped.
• Multi-hop routing with per-hop encryption — up to eight hops through the ruins; relays forward what they cannot read, which lets contingents from different countries share one fabric. Shipped.
• Store-carry-forward — findings, assessments and victim locations queue through out-of-reach periods and deliver in priority order on the next contact. Shipped, opt-in.
• Class priorities — victim locations and tasking ahead of photographs and bulk imagery on every thin hop and on the shared uplink. Shipped, opt-in.
• Continuous measurement — a per-hop, per-hour reachability record of the whole deployment, produced as a by-product of operating. Shipped.

The honest boundary: Atlas cannot make radio pass through a collapsed building — where nothing propagates, a node must physically be placed: a vehicle at the corner, the drone overhead, a kit left on a rubble crest as a relay. It does not find victims and it does not replace search doctrine or international coordination procedure; the satellite terminal is equipment the base brings. What the mechanisms demonstrably survive is the shadowing, fragmentation and out-of-reach gaps a collapsed city actually imposes.

What a pilot should prove

• Base connectivity for a team kit across multiple relay hops on a collapsed-structure training site, with the hop count and continuity read from the journal.
• Findings delivery: assessments and locations generated while out of reach arrive complete and in priority order after reconnection.
• Topology survival: the drone relay is swapped mid-exercise and vehicles move, with routes re-forming and no session re-established by hand.
• A deployment artefact: the reachability journal of the exercise, usable in the after-action review and for the next load-out decision.

One training site, one base, two teams. The evaluation format covers the structure.