The bvr missile is launched at the position of the launch---. The brain of the missile calculates the approximate speed of the aircraft that launched it and adjusts itself to its approximate distance travelled that aircraft.
Not exactly.
When the missile is launched, it will immediately know its own flight conditions, meaning if the missile is launched at 5000 meters altitude and 300 KIAS, it will uses that information to calculate its own flight path. So it is redundant for the parent aircraft to have anything like a 'pre-conditioning' process if that is what you are trying to say. When a missile is launched, the facts that matters are target information, not parent aircraft's flight conditions. Pre-conditioning the missile of target information, such as heading, airspeed, and altitude, are much more important.
It does not have to have a MISSILE lock.
Depends on the missile. The reality is that lock prior to launch is the ideal launch condition, but given the unpredictability of combat, we developed the 'fire and forget' type of missile. Of course, we also joked with a lot of truth that we can forget about hitting the target with that kind of missile.
Assuming radar guided for now, a missile's sensor view is severely limited compared to parent aircraft's and that is why the early generations of BVR missile required constant parent's radar lock on the target for the radar guided missile to succeed. Even as sensor sophistication grows, the missile just become less dependent on the parent aircraft, not fully independent from it. The dependency comes in several forms, such as initial target radar information or manual pilot queuing like the helmeted high off boresight method. The goal for 'fire and forget' type missiles is always the same: The sooner the missile is oriented towards the target, the better the odds of success, so if the target can be acquired by the missile prior to launch, all the better.
You have to keep in mind the necessity and history of the development of the BVR missile.
Guns required visual range proximity and it does not matter who you are, as a combatant, ground or air, you want to kill from as far away as possible. Today, we are developing guided bullets for the long distance sniper. Then from guns we developed missiles and installed some types of guidance on them. When I said 'installed' I do not mean physically but also conceptually. Some of my students/trainees from long ago have a difficult time understanding that difference.
Am going back to my 'instructor' mode and am going to have to compress two days of lessons into one post...
The early days of air-air missiles were not missiles but merely unguided rockets and against what are called
'STEADY STATE' targets -- bombers. Steady state targets are also known as 'cooperative targets'. They are cooperative, not in the sense that the bomber pilot will allow himself to be shot, but in the sense that they are:
- Ignorant of their status as targets
- The bomber aircraft is not very maneuverable
- The mission require the aircraft to be flown in a predictable manner
But even with favorable target conditions, unguided air-air rockets did not have a very good record.
The problem had little with aerodynamics because the same people who designed aircrafts designed those rockets and they are technically well versed. The problem was that when the rocket encounter anything that make it deviate from the 'steady state' target, it had no point of reference to reorient itself, whether that target is an aircraft or a ground fixture. The rocket was essentially a giant bullet.
So from the conceptual necessity for human involvement, we physically installed a connection to the rocket to make it a missile: the wire guided missile.
Obviously, the wire guided method have limitations so we relegated that method to the ground forces where targets are confined to 2D space and within line-of-sight. A more sophisticated guidance method is needed for (3D) airborne targets, even against steady state targets.
Then conceptually, we decided to slave the missile to the parent launch aircraft via an EM 'leash'. That EM leash is reflected radar signals from the target. Cannon rounds do not travel dozens of km, but human visual acuity does. So the initial radar guided missile were still within visual range (WVR) mode. We electronically illuminated the target to use the target itself as a point of re-orientation and in the 3D battlespace, re-orientation is a constant activity and is measured in microseconds. It does not matter if the target is completely ignorant of being a target. Every time the missile received an echo pulse, that is a command for re-orientation, even if the 'error' or 'displacement' figure from the previous pulse is mathematically zero.
When the target becomes 'non-cooperative', aka maneuvering and/or using distraction/seduction methods, that error or displacement figure gets larger and larger and this complicate things for the guided missile.
Ideally, I would rather have constant target updates in millimeter increments, for example. If the target move from zero to one millimeter, I want to know about it. But let us say the target is agile enough that from one microsecond to the next, it moved one meter. Now I have to put extra efforts to re-orient myself to keep the target inside my sensor view. But not only is the target so agile, it also uses things to obscure my sensor view, such as chaff or clouds or a mountain top. Each one of these compound that error or displacement figure, making me work harder and harder to keep the target in view. It turns out this EM connection is not as secure as conceptually thought when it was presented as a leash. I have to rely on a third party -- the parent aircraft -- to produce and sustain this connection. As if that is not difficult enough, there could be interference in the production of EM signals onto the target and on the echo signals that I must rely upon.
The next stage is to give the missile its own sensor but because there are technical constraints, the missile's sensor is severely limited in capability compared to the parent aircraft. Still, any sensor is better than no sensor. Now the missile have two sets of radar guidance, one from the parent aircraft and one from itself. But precisely because the missile's sensor view is much smaller than the parent aircraft's, the missile still needs some kind of initial target information.
Assume the missile's view -- straight ahead -- is zero degree as a reference.
If the initial target information is also zero, as in the target is literally in front of me, my initial flight path will be zero. No fuel necessary for re-orientation.
If the parent aircraft tells me who is on the starboard wing that the target is 30 degrees to port, which is out of my view, I have no choice but to have faith that the parent is correct. Fuel is necessary to make initial course correction.
If the target is non-cooperative prior to launch, that 30 degree error or displacement signal may become larger or smaller, forcing me to constantly recalculate my initial course correction. Remember, the parent aircraft is constantly feeding me these updates.
This leads to day two's lesson, the designs of missiles...
Aerospaceweb.org | Ask Us -
Missile Control Systems
Why do WVR missiles have canard controls and BVR missiles have tail controls ?
Tail control is probably the most commonly used form of missile control, particularly for longer range air-to-air missiles like AMRAAM and surface-to-air missiles like Patriot and Roland. The primary reason for this application is because tail control provides excellent maneuverability at the high angles of attack often needed to intercept a highly maneuverable aircraft.
Radar guided missiles predicts where the target is going to be then calculate an interception to that spatial point. If the target is non-cooperative, meaning maneuvers and/or uses EM countermeasures to create large error/displacement signals, rapid nose (sensor view) re-orientation is necessary, hence the high angles of attack. The 'attack' is not the target but that spatial point where the target is suspected/guessed going to be. This is where a lot of people have a difficult time envisioning.
Canard control is also quite commonly used, especially on short-range air-to-air missiles like AIM-9M Sidewinder. The primary advantage of canard control is better maneuverability at low angles of attack, but canards tend to become ineffective at high angles of attack because of flow separation that causes the surfaces to stall.
The AIM-9 is passive sensor -- infrared. Because there is no target feedback like an EM stream, passive sensor-ed missiles are tail chase missiles. The missile is not looking ahead of the target, just at its tail. So as far the sensor is concerned, as long as the target is within view, any target aspect change is a low angle of attack change. This is also where a lot of people have a difficult time envisioning.
Sensor type dictate interception laws which in turn affect the implementation of the flight control type, such as tail or canard control.
All of this lead up to the question: Does the missile require target lock prior to launch ?
For the AMRAAM, and its alleged peers from other countries, the requirement will depends on the immediate situation. The further the target is from the planned launch position, the more the desire for that target to be cooperative, meaning ignorant of its prey status in relationship to the hunter, which mean 'No', not required. That does not mean the pilot can launch at max range. He does not know if the target will become non-cooperative.
But if the target is non-cooperative at the same planned launch position, then the hunter will have to get closer in order to secure missile lock and/or be in a favorable position so his missile do not have to work as hard to secure its own target lock.
It is not a blanket 'Yes' or 'No' answer applicable to all missiles and situations. The pilot that does not know his weapons, advantages and limitations, will end up wasting his ammo and probably end up dead. At least figuratively, as in shot down, if not literally dead.
