OpenFront Nuke Flight Trajectory: Which Silo Fires, the Arc, and the U Key

Direct answer: the arc is automatic, but you control three of its inputs

When you click to launch a nuke, OpenFront does not draw a straight line from your base to the target. It draws a curved preview arc, and that arc is doing real work: it tells you which silo fired, how high the missile will climb, and roughly where it will come down. The good news is that the geometry is fully deterministic, not random, so once you understand the three inputs the game uses, you can read any arc on the map and predict the flight before the missile leaves the tube. Those three inputs are the launch tile, the target tile, and the arc direction. The launch tile is chosen for you by the engine, the target tile is wherever you click, and the arc direction is the one knob you actively turn with the U key. This guide walks through each of those three, in the order the game actually computes them, and then turns them into decisions: which silo you are really using, how to make the missile fly higher or flatter, how to minimize or maximize the time the enemy has to react, and how to read the landing zone accurately. The numbers below come from the official v0.34.18 tagged source, from the trajectory and nuke-speed functions, not from a forum estimate, so the geometry you are learning matches what is running on the server right now.

If you only remember one thing, remember that the arc peak is one third of the straight line between the silo and the target, floored at fifty tiles, and that the U key flips which side of that line the whole curve bows toward. Everything else in this guide is the consequence of those two facts. The arc is not a suggestion you can ignore and a missile you can still steer; it is the flight plan, drawn to scale, and the missile will fly exactly the path the preview shows. That is also what makes the trajectory learnable. There is no hidden randomness, no server-side jitter, no angle you dial in with a mouse; the only inputs are the two tiles and the one direction flag, and the rest is geometry. So the skill this guide is building is reading the three anchors of the arc, the start, the peak, and the end, and then making your silo placement and your U key presses produce the flight you want. When the section on flight time arrives, you will see that the same arc also encodes the clock the enemy is counting against, which is the reason the shape of the curve matters to the defender just as much as it matters to you.

How the launch tile is chosen: the engine picks the nearest usable silo

The first thing to internalize is that you do not choose which missile silo launches a nuke by hand. In v0.34.18 the launch position is resolved by a single engine call, and the rule it implements is distance first. When you commit to a nuke at a target tile, the game asks, from your own owned units, for the silo that is nearest to the destination and actually able to serve this launch, and that silo is where the missile spawns from. In practice this means your nukes always leave from the silo closest to the target you clicked, not from the silo closest to your capital, and not from whichever silo you built first. The consequence is that your base layout quietly decides every nuke flight you will ever make, which is why silo placement is a genuine strategic decision and not a cosmetic one. If your silo sits on the far edge of your territory, a nuke aimed at the enemy core will arc over a long stretch of map and spend most of its flight high in the air, because the straight-line distance from that edge silo to the target is large and the arc height is proportional to that distance. If instead you have a silo pushed forward near the border, the same nuke is a short, flat, fast flight, and the enemy gets almost no warning.

There is one more constraint on the same rule, and it is the one that surprises players the most. A silo that has just launched a missile is on cooldown, so if the nearest silo is still reloading, the engine falls back to the next-nearest usable silo, and your missile will visibly spawn from a different tile than you expected. That fallback is the single most common reason players say a nuke came from the wrong silo, and it is the engine doing exactly what it is programmed to do, not a bug and not a mis-aim on your part. The way to predict it is to look at how many silos you have and how far apart they are. With one silo, every launch uses it and every launch after the first waits for the cooldown, so your launches trail one after another. With several silos spread across your territory, the engine will rotate between them, and a burst of nukes will visibly fan out from several different tiles, which changes the arcs and the arrival times of the whole burst. So when you are planning a nuke, the first question is not which target but which silo, and the answer is the one the engine will hand you, the nearest tile that is not on cooldown, which you can read directly off the start of the preview arc.

The parabolic arc: how high the missile climbs is one third of the distance

The shape of the preview arc is not decorative; it is a real parabola that the missile flies, and its height is computed from the geometry between the launch tile and the target tile. The engine takes the straight-line distance between the two points and sets the peak of the curve to one third of that distance, with a floor of fifty tiles. So a nuke fired across a small gap climbs less than the same nuke fired across a large map, and on a very short hop the floor of fifty tiles keeps the arc from collapsing into a flat line that would be easy to read and easy to intercept. The curve is a Bezier arc anchored at the launch tile and at the target tile, with two control points placed a quarter and three quarters of the way along the straight line and pushed outward, perpendicular to that line, by the peak height. That perpendicular push is what you see as the arc bowing away from the straight line, and it is the single thing that separates a nuke arc from any other unit movement on the map, because no other projectile in the game climbs that high on a predictable curve.

Because the height is proportional to the distance, a long-range nuke always has a taller, more looping arc, and a short-range nuke has a flatter, more direct one, and the preview arc is the best built-in tool you have for spotting a mistake, because the arc is a truthful map of the missile’s path. The top of the curve is roughly how high the missile will get, and the endpoints are exactly the silo it leaves from and the tile it lands on. If the curve looks wrong, the missile will fly wrong, so the arc is not a hint you can dismiss, it is the flight plan drawn to scale on your screen. When you are planning a nuke, read the three anchors on the curve, the start, the peak, and the end, and you have the entire trajectory summarized for free, which is why the rest of this guide keeps coming back to those three points. The peak tells you how much of the flight is spent high in the air, the start tells you which silo the engine chose, and the end tells you the landing tile. Put the three together and you can predict the whole flight, including how long it takes and where the enemy can reach it, before you spend a single unit of gold on the missile.

The U key: flipping which side of the line the arc bows toward

The arc direction is the one input you actively change with a key press, and it is the knob most players under-use. The engine carries a direction flag, and by default it points the arc so that it bows toward the top of the map. Pressing the U key toggles that flag, which makes the same nuke bow toward the bottom of the map instead. The start and end tiles do not move, and the peak height stays the same one-third-of-distance value, so the U key does not make the missile fly faster or slower and it does not change where it lands. What it changes is the side of the launch-to-target line that the whole curve hangs on, and that sounds like a small thing but it is the whole of your active control over the flight shape. In an open map with no obstacles it is mostly cosmetic, but the moment there is a SAM launcher, a wall of buildings, or a body of water between the silo and the target, the side of the bow decides whether the missile passes above or below the threat.

If the enemy has a SAM ring on the north side of your target and the default arc bows north, the missile will climb right into the interceptor’s zone, but pressing U to flip the bow south sends the same missile down the other side of the line, often through a gap the ring never covered. The rule is that U is your one real aiming correction: you cannot redirect the landing point with it, but you can choose the side of the corridor the missile flies on. Learn to look at where the enemy’s SAMs sit relative to the straight line from your silo to the target, and then use U to put your arc on the open side. That single habit turns a missile that would have been caught mid-arc into one that arrives. It is also worth understanding why the flag works this way and not some other way: because the arc is a symmetric parabola, flipping the perpendicular direction is the only way to mirror it without changing the endpoints, so the engine exposes exactly one boolean and you get exactly one mirror. That means your U key strategy is binary, either side of the line, and you do not need to chase a fine-grained angle. You need to pick the open side, and the preview arc updates instantly so you can see which side you are on before you commit the launch, which is the whole discipline in one sentence: watch the arc, check the threat side, and flip if the bow is on the wrong side.

The 150-tile targetable range and what it does to your aim

There is a hard geometric limit around every nuke that players rarely see but that shapes the whole flight, and it is the targetable range. In v0.34.18 a nuke is only targetable while it is within one hundred and fifty tiles of either its launch point or its destination, and the engine encodes that limit as a square radius of one hundred and fifty tiles around each endpoint. What that means in practice is that the middle of the arc, the high part of the loop over the middle of the map, is untouchable by anything, because it is more than one hundred and fifty tiles from both the silo and the target. The interceptable window lives only in the first one hundred and fifty tiles after launch and the last one hundred and fifty tiles before impact, and the safe middle section between them grows with the flight distance. For the player who is firing, the useful read is about the landing side. The missile becomes a live, interceptable object only when it is back inside one hundred and fifty tiles of where it is going to land, so the final stretch of the arc is the part the enemy can contest, and everything before that is a free ride.

For the defender, the same number is the entire window they have to respond, which is why the nuke defense protocol is built around counting that last one hundred and fifty tiles rather than the whole arc. For your own aiming, the targetable range is the boundary that tells you how much of the arc the enemy actually has to watch. If your landing is deep inside the enemy’s territory, the missile is safe for most of its flight and only exposed in the final hundred and fifty tiles, so the enemy’s SAMs only matter if they sit close to the landing zone, and a ring far from the landing is useless against you. The distance between your silo and the target sets the size of that safe middle section: the longer the flight, the longer the missile spends out of reach of both ends. This has a practical implication for when to fire. A long flight means the enemy has to commit their launchers early to the right side of the line, because once the missile is out of range of the silo they can no longer contest the middle, and only the final approach is left. So the targetable range is not just a defense number, it is an aiming tool that tells you which part of your arc is safe and which part is exposed, and it is the reason a long arc from a far silo is both taller and safer in the middle than a short arc from a near one.

Flight time: arc length and per-type speed together set the window

The total time a nuke is in the air is the product of how long the path is and how fast the missile travels along it, and in v0.34.18 the two come from different places. The path length is the parabolic arc you have just learned to read, and the speed depends on the type of nuke. The engine returns a slower value for the standard atom and hydrogen bombs, a faster value for the MIRV mother missile, and the fastest value for the individual MIRV warheads once they separate. That ordering is the whole story of timing. A standard bomb on a short arc is the slowest, most telegraphed flight in the game, and it gives the defender the most time to reposition and bring a launcher to bear, while a MIRV warhead on a longer arc, by contrast, covers the distance faster, so the window the defender has before impact is shorter even though the path is longer. The two ways to change the flight time are therefore to change the arc and to change the weapon, and you have both available to you at launch time.

To minimize the time the enemy has to react, you want a short arc, which means a silo close to the target, and a fast warhead, so the missile covers a short distance at the top speed the engine allows. To maximize the time you have to plan, or to make a nuke that is easy for the defender to read, you want a long arc from a far silo and a slow standard bomb. This is why silo placement is not only about arc shape but about timing: the same MIRV fired from an edge silo gives the enemy a much longer warning than the same MIRV fired from a border silo, even though it is the exact same weapon with the exact same speed. When you are choosing when to launch, treat the arc you are seeing as a clock. A flatter, shorter arc means less warning and a harder intercept for the defender, while a tall, long arc means more time and an easier read. The which nuke to commit guide decides which weapon is worth spending, and this section decides how the flight itself will feel once you spend it, because the same hydrogen bomb is a different threat at every range, and the defender is reading your arc to estimate the clock you are giving them. The single most useful habit is to never fire a nuke without first looking at the preview arc and asking what flight time that arc encodes, because the arc is the only honest estimate of the window the defender has, and it is the number you are optimizing when you place silos and choose warheads.

Scenario A: routing an arc through a gap in a SAM ring

Put the mechanics together and the decision becomes concrete. Suppose the enemy has built a SAM ring around their core, and the ring is strong on the north side but thin on the south side, because they extended their territory southward and never re-aimed their launchers. You want to nuke that core. Your default arc, with the direction flag at its top-bow setting, will climb northward toward the target, which is exactly the strong side of their ring, and the missile is going to be inside a launcher’s reach while it is still more than one hundred and fifty tiles out from the landing. The fix is the U key. Flip the direction flag so the arc bows south instead, and now the same missile, from the same silo to the same landing tile, takes a path that hangs on the south side of the straight line and passes through the thin part of the ring. The peak height is unchanged, the landing is unchanged, but the corridor the missile occupies is different, and you have moved the intercept point out of the launcher that was waiting for it.

The second lever is the silo itself. If your nearest silo to the target is the one that produces the north-bow path, check whether a second silo, further from the target, would produce a flatter arc that dips under the ring instead of over it. A lower arc under a ring is often safer than a high arc over it, because a low missile spends less of its flight at the heights where the launchers are aimed, and the targetable range means the only part you can still be caught in is the final hundred and fifty tiles. The discipline here is to read both the arc side and the arc height before you fire, and to use the U key and your silo choice to route the missile through the gap rather than through the wall. The payoff is a nuke that was going to be caught arriving clean, which is the entire difference between spending a nuke and wasting one. In a real game this is also where the cooldown fallback matters, because if you flip the silo to the farther one and the nearest one is on cooldown, the engine may still pick the one you do not want, so the scenario only works when you have control over which silo is free, which is another reason to build two silos and keep them spread so you have a choice of arc shapes at any given moment.

Scenario B: minimizing and maximizing the warning window

The same arc, read as a clock, gives you two opposite goals, and both come from the same two levers, the silo distance and the weapon speed. To minimize the warning the enemy has, you want the shortest, fastest flight. That means choosing the silo closest to the target so the straight-line distance, and therefore the arc, is as short as it can be, and launching a fast weapon such as a MIRV warhead so the missile covers that short distance at the top speed the engine allows. On a small map with a border silo, this produces a flat, quick arc that gives the defender only the final one hundred and fifty tiles to react, and at the fast warhead speed that is a matter of a few seconds, which is often not enough time to bring a launcher into position. To maximize the warning, the opposite, you would choose a far silo for a long, tall arc and a slow standard bomb, and the missile spends most of its flight in the safe middle section, high over the map, before it becomes targetable at the end.

Players rarely want to maximize warning on a nuke they are firing, so this scenario mostly matters when you are reading the enemy’s nuke, and that is the higher-value use of the skill. When you see a tall, looping arc coming at you, you are being fired at from a far silo and you have a long window to build a ring and reposition, and the height of the loop is a direct estimate of how far away the shooter is, because the peak is one third of the distance. When you see a flat, short arc, you are being hit from a nearby silo with a fast warhead and your window is short, so you react immediately and do not waste a launcher on the wrong side of the line. Reading the shape of the incoming arc as a timer is a free advantage, and it is why the preview geometry matters to the defender as much as to the attacker, because the enemy is doing the exact same read on your arcs that you are doing on theirs. The MIRV mechanics guide covers the cost and the warhead ladder, and this section covers how that ladder changes the clock you are reading on the map, which is the reason the same MIRV threat is a different emergency at every range, and the reason a defender who can read arc height can prioritize which incoming missile to intercept first.

Failure modes and how the enemy turns your own arc against you

The arc is a real asset, but it is also the single biggest tell you give the enemy, and the failure modes all come from treating it as a freebie. The first failure is launching from the nearest silo on cooldown, so the engine falls back to a farther silo and the arc becomes taller and slower than you planned, giving the defender a longer window than you expected and possibly routing the missile through a launcher you did not plan for. The second is firing the default top-bow arc into the strong side of a SAM ring because you never checked which side the launchers are on, so you hand the enemy a target right in the middle of their coverage and the missile is caught with most of its flight still in front of it. The third is stacked launches. When you buy several nukes at once, the silo queues them across successive ticks so the launches trail one after another instead of overlapping, and a burst of missiles arriving on the same arc is exactly what a pre-aimed ring is built to catch, so spreading the launches over time or over different silos is better than a tight cluster that all shares the same corridor.

The fourth failure is the enemy reading your arc and pre-positioning, which is the most insidious one because it is not a mistake you make, it is a pattern they exploit. A defender who sees your arc side and your arc height knows the corridor before the missile leaves the tube, so a repeatable pattern, always the top bow from the same edge silo, becomes something they can sit inside and wait for. The counterplay is variety and the U key. Change the bow side between shots, change the silo you use, and use the fast warhead when you want to deny the window and the slow bomb when you want to read their response before committing. The deepest lesson is that the arc is two-sided. It is your aiming tool and it is the enemy’s targeting tool at the same time, so the moment you fire, the information you are reading is the exact information they are reading back, and the player who wins the nuke fight is the one who treats every arc as a message in both directions and plans the second nuke before the first one lands, because the second nuke is the one that is not pre-aimed and the one that actually gets through.

Mode and map adjustments, and where this guide ends

The trajectory mechanics hold across every mode, but the numbers you act on shift with the setup, and the same arc means a different thing on a small map than it does on a large one. In a one-versus-one the map is small and the enemy silo is close, so your arcs are short and flat and the final one hundred and fifty tiles is nearly the whole flight, which means timing is the dominant lever and the U key is used more for dodging a single aimed ring than for routing a long path. In Nations and team modes the map is larger and there are several players with nukes, so you are reading multiple arcs at once and the arc side matters more because the threat comes from more directions, and the safe middle section of a long arc becomes genuinely useful because you have time to reposition while a slow bomb is still out of reach. On a larger map the tall, looping arcs you see are the far-silo flights, and reading their height is how you estimate how far away the shooter is, because the peak is a direct fraction of the distance.

Map size also changes the targetable math in a specific way. A longer flight puts more of the arc in the untouchable middle, so on big maps nukes are safer in flight and only exposed at the ends, while on small maps almost the entire flight is inside one hundred and fifty tiles of an endpoint and therefore contestable the whole way. This is the reason the same hydrogen bomb is a very different threat on a large Nations map than on a small one-versus-one, and the reason the U key is more valuable on the large maps where there is room to route around a ring instead of going over it. This guide owns the flight itself, which silo fires, how the arc is shaped, and the U key. The hotkeys guide lists the U key and the other inputs, the nuke calculator covers the damage and cost side, and the water nukes guide covers the one map condition, a landing in water, that changes the impact. Read the arc as a flight plan, use the U key as your one real correction, and place your silos so the arcs you get by default are already the ones you want to fire, because the cheapest trajectory is the one you never have to correct, and the strongest silo layout is the one that puts the good arcs in your hands by default.