OpenFront Nuke Defense Protocol: Real-Time SAM Response to an Inbound Warhead

Direct answer: verify automatic coverage, then plan for impact

When a warhead is already inbound, the decision is not “do I have enough SAMs” but “does my ring actually cover the last 150 tiles of this warhead’s flight, and is a slot ready on that side right now.” A nuke in v0.34.21 is targetable only while it is strictly inside 150 tiles of either its launch point or its destination, and a SAM Launcher can only shoot a targetable projectile that also lies inside its own firing range. That means your interceptable window is the final 150 tiles before impact, not the whole arc across the map. At the v0.34.21 flight speeds the window is short: Atom and Hydrogen Bombs move at 10 tiles per tick, so the final 150 tiles take 15 ticks, about 1.5 seconds at the configured 100 ms per tick; a MIRV warhead starts at 22 tiles per tick and covers the same distance in about 7 ticks, roughly 0.7 seconds. A MIRV warhead is faster than a Hydrogen Bomb, and one MIRV carrier can stage many warheads with small wait and speed offsets, so you are not defending one window but a dense stream of automatic targeting decisions. The protocol is therefore four steps, in order. First, the moment you see the first warhead, locate the landing zone and ask which of your launchers sits within firing range of a point inside the last 150 tiles of that arc. Second, check that a slot on that launcher is actually ready, because a slot that just fired is reloading for 90 ticks, nine seconds, and is useless for this intercept. Third, do not look for a fire control: the SAM targeting system launches automatically when its trajectory solver finds a reachable, targetable intercept and a slot is ready. Fourth, if no launcher covers the landing zone, accept that the system will not launch a futile missile and prepare for both local blast deletion and the separate global troop-loss calculation; moving ordinary troops beyond a visible ring does not exempt them. This guide owns that real-time moment. The SAM launcher guide answers the planning question of how many launchers to build; the MIRV mechanics guide answers what the weapon is and how the ladder works. Here the warhead is already flying and you are the defender, and the question is what to do in the next few seconds. The flight and range numbers below come from the official v0.34.21 tagged source, not from a forum estimate.

The flight window you actually have, per warhead

The table is a timing bound, not a promise that every launcher receives the whole bound. The automatic solver subtracts the SAM missile’s own travel time from the warhead’s remaining path and rejects a shot when the meeting tile lies outside the launcher’s dynamic range. A launcher can therefore detect a warhead inside the 600-tile search radius yet never spend a slot. Read 15 or 7 ticks as the maximum destination-side path segment available to solve, then let placement, missile travel, range, and construction state decide how much of it the launcher can actually use.

The single most useful number in a nuke-defense game is the length of the interceptable window, and it is different for every warhead type because the nuke flight speed differs. In v0.34.21, msPerTick() is 100, so the game advances at ten ticks per second. nukeSpeed() returns 10 tiles per tick for Atom and Hydrogen Bombs and 22 for a base MIRV warhead. The targetable range is 150 tiles, and a nuke is targetable only while strictly within 150 tiles of its launch point or destination. A defender normally relies on the destination half. Dividing 150 by speed gives 15 ticks, about 1.5 seconds, for Atom/Hydrogen and about 6.8 ticks, roughly 0.7 seconds, for a base-speed MIRV warhead. The actual automatic shot also needs the SAM missile, moving at 12 tiles per tick, to reach a computed meeting tile inside the launcher’s dynamic range. The verified values are:

Atom and Hydrogen Bombs have the same destination-window timing; MIRV warheads are faster and far more numerous, so MIRV stresses slot depth and reachability rather than giving the defender a repeated five-second reaction window. This is the number the community underestimates, because the visible arc of the warhead across the map looks long and slow, but the part of that arc your SAMs can actually touch is only the last 150 tiles. The rest of the flight the warhead renders opaque and is invulnerable, so a launcher sitting far from the landing point is watching a projectile it will never be able to shoot. The rule to internalize is that the warhead becomes a target only when it is inside the final 150 tiles, and your total useful decision time is the 150 divided by the speed, in ticks. When you see the alert you should already know, for each warhead type, how many seconds that division gives you, so you are not doing the arithmetic in real time against a timer.

Does your ring cover the landing, the geometry check

The second question is whether a launcher on the landing side of your ring is close enough to a targetable point to actually fire, and this is where most “my SAMs did nothing” reports come from. A level-N SAM Launcher has N missile slots and a real firing range given by the formula 150 minus 480 over level plus 5. A level 1 launcher reaches 70 tiles, a level 5 reaches 102, a level 10 reaches 118, and the range approaches 150 as the level climbs but never reaches it. The launcher also has a broad 600-tile search radius, but that number is only for early detection of fast projectiles; it is not the firing range, so a launcher 400 tiles from the landing zone sees the warhead early and still cannot shoot it. The geometry you must check is the triangle between the landing zone, your launcher, and a point inside the last 150 tiles of the flight. The warhead is targetable at any of those last-150-tiles points, but your launcher must be within its own firing range of the specific point where its missile will meet the warhead. If your ring is built tight around the core, every launcher is close to the landing zone and most will be in range of a targetable point, which is the correct defensive placement. If your launchers are spread out to a wide perimeter, some of them are inside the 600-tile search radius, see the warhead, and are still more than 150 tiles from any targetable point on the landing side, so they idle while the warhead lands. The check is a per-launcher test: for each automatic launcher, does its range intersect a targetable point on the landing-side trajectory? If the ring is built around the core, the answer is yes for most of it. If the ring is built on a wide arc, the answer depends on which direction the strike came from. The single most useful pre-game habit is to place at least one mid-level launcher directly between the core and each side of the map, so that no matter which direction an inbound warhead is aimed from, one launcher is on the landing side and inside its own firing range. That placement converts the geometry from a per-direction gamble into a guaranteed covered landing, and it is the difference between a ring that looks dense on the map and a ring that actually intercepts.

The real-time decision tree, from warning to automatic intercept

This tree is an observation protocol: it tells you why the automation will succeed or fail and what state to preserve afterward. It is not a sequence of manual firing inputs.

Now combine the window and the geometry into the four-step decision you run every time a warhead appears, and do it before the warhead reaches the landing zone. Step one is detection and landing-zone identification. The moment the alert fires, note where the warhead is aimed, because the landing zone is the only point that matters for your geometry check; everything you build toward the launch side is wasted for this intercept. Step two is the coverage check against that landing zone. Ask which of your launchers sits within its own firing range of a point inside the last 150 tiles of the flight toward that landing zone. If the ring is built around the core this is usually two or three launchers, the ones nearest to the impact side. Step three is the ready-slot check on exactly those launchers. A slot that fired on a previous warhead is reloading for 90 ticks, nine seconds, and a launcher whose only slot is reloading cannot intercept this warhead no matter how well placed it is, so the count that matters is not the number of launchers you own but the number of ready slots on the landing side. Step four is to observe the automatic result and switch to damage control if no reachable intercept exists. If at least one landing-side launcher has a ready slot and a reachable intercept, the targeting system fires automatically at the computed tick; there is no manual shot to time. If no landing-side launcher has a reachable ready slot, the far-side launcher will not waste a missile: its solver marks the trajectory unreachable. Accept the hit, move only map units that can escape local deletion, and budget for proportional troop losses across the global pool, outgoing attacks, and Transport cargo. The decision tree is fast on purpose. You are not trying to maximize intercepts in the abstract; you are answering one question for this specific warhead, which is whether a ready launcher on the landing side can touch a targetable point before impact, and acting on the yes or no without hesitation. The useful reaction is diagnostic rather than a manual trigger: the Atom or Hydrogen destination window is about 1.5 seconds, while a base-speed MIRV warhead has only about 0.7 seconds, so placement and ready slots must exist before the warning.

MIRV, a stream of windows instead of one

Because every SAM missile marks one warhead as already targeted, ready-slot capacity is an upper bound on simultaneous claims, not a percentage shield applied to the whole MIRV cloud.

A MIRV changes the problem from a single intercept into a staggered stream of intercepts, and that is the reason it is the hardest defense to run. A MIRV costs 25M plus 15M for every earlier MIRV launch in the match. A carrier can stage up to 350 target tiles; its warheads spawn together but receive 0-14 wait ticks and speed bands from 22 to 26 tiles per tick, so they reach their separate 150-tile targetable windows as a dense, uneven stream. That means your SAM ring is not being asked to shoot one target at one instant; it is being asked to shoot a sequence of targets, each with its own short window, and the windows overlap in time. The 350-warhead cap belongs to each MIRV carrier, not to a level-10 Silo; Silo level controls ready launch slots, while valid target spacing can make the actual staged count lower. The reload is the critical constraint here. A slot reloads for 90 ticks, nine seconds, and if the MIRV warheads arrive faster than your ready slots reload, you will have a window with a ready launcher and the next window with none, and the second warhead lands. The defense question for a MIRV is therefore not “can I intercept the first warhead” but “can I sustain intercepts across the whole staggered arrival.” The practical answer depends on the level of your ring. A ring of high-level launchers, where each launcher has many slots, can keep a pool of ready slots cycling through the staggered windows, because while some slots fire and start reloading, other slots on the same launcher are still ready. A ring of level-1 launchers, one slot each, cannot, because after the first volley every slot is reloading and the later warheads have no ready launcher to intercept them. The rule is that against a MIRV you need slot capacity, not launcher count; a few high-level launchers on the landing side beat many level-1 launchers, because the staggered arrival punishes any launcher whose slots all fire at once. The community answer that matches this is to keep at least two launchers on the landing side at a level high enough that their combined ready slots exceed the number of warheads arriving in any overlapping pair of windows, so that the ring can absorb the stagger instead of being overwhelmed by it.

Scenario 1, a hydrogen at your core in a one-versus-one

Walk the full protocol against a concrete situation, a one-versus-one where the enemy has a level-1 Hydrogen Silo and fires at your core with no prior warning. Your setup is a ring of three launchers built around the core, two at level 5 and one at level 10, and your backline is holding near the coast. The enemy Silo is on the far side of the map, so the Hydrogen Bomb has a long arc but still advances at 10 tiles per tick. The alert fires. First, the landing zone is your core, so the last 150 tiles of the flight are the region right around your core, and your ring built around the core means all three launchers are on the landing side. Second, the coverage check: a level 5 launcher reaches 102 tiles and a level 10 reaches 118, and the launchers are built within roughly 30 to 50 tiles of the core, so each is well inside its firing range of the targetable points in the last 150 tiles around the core. Third, the ready-slot check: the two level 5 launchers have five ready slots each and the level 10 has ten, and none of them has fired yet, so there are twenty ready slots on the landing side. Fourth, the automatic result: a Hydrogen Bomb is one warhead, so one reachable ready slot can be enough; the trajectory solver chooses the launch tick and whichever eligible launcher claims the target first. The SAM missile travels at 12 tiles per tick while the Hydrogen Bomb crosses its final 150 tiles in 15 ticks; the solver fires only when both paths produce a reachable meeting point, so this assumed geometry ends in an intercept without a player click. The backline stays put, no troops are lost, and the core is unharmed. Now the variant that matters: the same hydrogen, but your ring was built on a wide perimeter arc and the two launchers nearest the impact side are both at level 1 with a single slot each, and one of them fired on an earlier skirmish and is reloading. The coverage check now fails for the reloading launcher, and the other level 1 reaches only 70 tiles, which may not cover the specific targetable point on the landing side if the arc brings the warhead in from the flank. With no reachable ready launcher, there is no panic-fire action: the far-side system stays idle. Move vulnerable map units beyond the 100-tile outer blast radius if possible, but do not claim that ordinary troops are saved by distance; any owned tiles hit trigger proportional losses in the global troop pools. The difference between the two outcomes is not the number of launchers, it is whether the ring was built around the core with ready slots on the landing side, which is the placement this guide is built to protect.

Scenario 2, a MIRV volley against a mid-level ring

Now the harder situation, a one-versus-one where the enemy has a level-8 MIRV Silo and fires a staggered volley at your core while you hold a mid-level ring. Your ring is four launchers, two at level 8 and two at level 12, built around the core, and your backline is holding near the coast. The level-8 Silo provides eight launch slots, but a single MIRV carrier still stages up to 350 warheads; their 0-14 tick waits and 22-26 tile-per-tick speed bands create the stagger, not the Silo level or price ladder. As the first reachable warheads arrive, the automatic ring spends ready slots one target at a time. Four launchers at levels 8, 8, 12, and 12 expose 40 ready slots at most, so they cannot guarantee a stop against a carrier that stages hundreds of valid targets. The critical moment is the second wave. While the slots that fired on the first wave are reloading for 90 ticks, the second wave arrives inside the same landing zone, and the question is whether enough ready slots are still cycling. The level-12 launchers contribute twelve slots each and the level-8 launchers eight each, but only slots not already spent can claim later warheads; remaining capacity depends on how many earlier paths were reachable, not on a guaranteed two-wave script. The stagger is the design of the problem: the enemy is trying to time the second wave to land in the reload gap of your first volley, and a ring with deep slot capacity on the landing side closes that gap because the higher-level launchers still have ready slots while the lower-level ones are reloading. The variant that fails: the same MIRV volley against a ring of level 1 launchers, twelve of them, one slot each. Twelve level-1 launchers can claim at most twelve reachable warheads before every slot enters the 90-tick reload, leaving the rest of a large MIRV stream unopposed. The lesson is that against a staggered MIRV, slot capacity beats launcher count, and the placement that matters is a couple of high-level launchers on the landing side that keep a ready-slot pool cycling through the staggered windows. If you are defending against a known MIRV and you have reserve Gold, the move before the volley is to upgrade one landing-side launcher to a higher level so that its slot pool can absorb the stagger, because the cost of one upgrade is far less than the cost of a lost core. Move Warships, Trade Ships, Transports, and other local units away from likely MIRV impact tiles when time permits, but remember that MIRV troop loss is also applied through its configured global casualty formula; map distance is not blanket immunity.

When the defense will fail, the five cases

Most nuke-defense losses come from one of five specific, avoidable cases, and recognizing which one you are in is more useful than trying to remember a formula. Case one is the late build. A reactive SAM build is unreliable: an under-construction launcher does nothing, and it must finish early enough for the solver to find a later destination-side intercept. Keep coverage ready before launch rather than assuming the opaque middle of a flight makes the later 150-tile destination window disappear. Case two is the placement that is far from the landing zone. A launcher built on a wide perimeter sees the warhead inside its 600-tile search radius but is more than its own firing range from the targetable points on the landing side, so it idles; the fix is to place at least one mid-level launcher between the core and each side of the map so the landing side is always covered. Case three is the reloading slot. A launcher whose slots all fired on the previous warhead is reloading for 90 ticks and is useless for this one; the fix is to keep a ready-slot pool by using high-level launchers with many slots, so that some slots are always ready even after a volley. Case four is the staggered MIRV against a thin ring. A volley of level-1 launchers, one slot each, fires its whole pool on the first wave and has nothing left for the staggered later warheads; the fix is slot capacity on the landing side, not more single-slot launchers. Case five is the economic mismatch. If the enemy’s nuke program is funded from a much larger economy than yours, you cannot match their launch frequency with a ring you keep rebuilding, and the correct response is not a bigger ring, it is to deny the launch itself by destroying or capturing the enemy Silo, because every Silo you remove removes an entire source of inbound warheads and no amount of SAM coverage fully replaces that. The pattern behind all five is the same, the defense fails when a launcher on the landing side is either absent, out of range, or out of ready slots at the moment the warhead needs intercepting, and the pattern is fixable in every case by the specific placement and capacity the rest of the guide describes. The community threads that say “my SAMs do nothing” almost always resolve to one of these five, and the diagnostic is to run one hydrogen test against your own ring and watch which case is the one losing, because the test takes thirty seconds and tells you exactly which of the five to fix before a real match.

What to do in the seconds you lose, the fallback

If the geometry says the warhead will land, use the nuke evacuation guide to separate movable objects that can cross the outer radius from troop pools that still take player-wide losses.

When the geometry check says no launcher covers the landing zone, you are going to take the hit, and the question becomes which losses can still be limited. Moving a Warship, Trade Ship, Transport, or other map unit beyond the outer blast radius can protect that unit from the explosion’s separate local deletion pass. It does not move your army outside the proportional casualty calculation. Once one of your owned tiles is hit, the ordinary Atom or Hydrogen calculation removes troops from your global uncommitted pool, every outgoing attack, and the cargo of every Transport, including Transports outside the visible ring; more owned tiles in the blast repeat that calculation. Distance therefore saves only the local unit deletion, not all troops. Preserve movable assets when there is time, but budget for the global loss and do not claim that water or a 100-tile retreat makes the force safe. If a trajectory is unreachable, the automatic launcher does not spend its slot; use that preserved capacity when judging whether another affordable warhead may follow. If the enemy spent their reserve on one Hydrogen Bomb, recovery may now matter more than another impossible intercept; the post-MIRV recovery guide covers the bounded rebuild. Plan the counter-strike only from the force that actually remains after impact. The fallback is the correct branch of the decision tree, but it is damage control: protect movable units from direct deletion, expect proportional losses across all troop locations, preserve the next viable intercept, and reassess the border after the event resolves.

The damage boundary matters because OpenFront does not store ordinary land troops at a geographic backline. For every player with tiles in the blast, NukeExecution counts affected owned tiles and repeatedly applies nukeDeathFactor to that player’s global uncommitted troops, each outgoing attack, and every Transport’s cargo. Atom and Hydrogen use (5 * humans) / max(1, tilesOwned) on each affected tile; MIRV warheads use their separate max-troop curve. The 100-tile Hydrogen outer radius therefore answers which tiles, structures, and local units are in the blast, not which soldiers escape the population calculation. A ship or other map unit can avoid direct local deletion by leaving the radius, but its troops may still participate in the global calculation when the player owns impacted land. This is why the fallback starts with an honest loss estimate, not a promise to save an army by dragging a front marker across water. After impact, recount actual troops, attacks, cargo, Cities, and borders before committing a counterattack; planning from the pre-impact number compounds the nuclear loss with a bad conventional trade.

Mode and map adjustments, where the numbers shift

Team play adds a coordination constraint rather than changing the weapon constants. An allied launcher near the threatened destination may contribute an intercept against an enemy warhead, but teams still have several separate economic centers and cannot assume a single shared core. Mark which allied coverage actually intersects each likely destination, and do not add launcher levels that protect different centers as if every slot could reach every strike. In FFA and Nations, repeat the same check for each direction because the nearest hostile Silo can change while the 150-tile targetability rule does not.

The same protocol changes in a few specific ways depending on the mode and the map, and the shifts are large enough that copying a one-versus-one answer into a different setup is a real mistake. In one-versus-one the map is small and the enemy Silo is far, so the flight arc is long and the last-150-tiles window is the whole window you have to defend, which is why the ring-built-around-the-core placement works so cleanly. In a Nations or team mode the map is larger and there are more players with nukes, so you can be hit from multiple directions at once, and the single-landing-side check becomes a multi-direction check, which is why the placement of a mid-level launcher between the core and each side of the map, not just one side, becomes mandatory. In team mode, each player keeps a separate economy and core. Coordinate spending rather than pooling it: count an allied launcher only when its dynamic range actually intersects the threatened destination path, because launchers protecting another teammate’s core cannot be treated as ready slots for yours. Map size changes total travel time, not the 150-tile destination window: a longer arc can give more time after the launch warning, but it does not let you pre-place a structure that was never built, and an unfinished launcher still cannot act. Difficulty is not a distance shield and does not change the configured Atom/Hydrogen blast radii or their casualty formula; mode and map alter who can attack and from which directions, while the verified weapon constants remain the same. The invariant is that a warhead is targetable strictly within 150 tiles of launch or destination. For defense, the destination-side travel time is about 15 ticks for Atom/Hydrogen and about 7 ticks for a base-speed MIRV warhead; coverage, slot state, and automatic trajectory reachability determine the result. The mode and map change the geometry and each player’s spending priorities; they do not change the window, and the window is the number the whole defense is built on.