J-20 5th Gen Fighter Thread IV (Closed to posting)

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Quickie

Quickie

Colonel
plawolf said:
I am not aware of any IRAAMs that are launched via dropping. All dogfighting missiles are rail launched, and for good reason.

When you drop a missile, you are relying on gravity for safe separation, so that pretty much dictates the fighter can not perform any violent manoeuvres during launch as well as massively restrict the potions the fighter can launch. Imagine, if you will, what would happen to a drop launched missile if the carrying fighter is launching during a hard turn.

If the fighter was pulling positive Gs during the turn, the second or so between separations and engine ignition could easily mean the missile looses the lock before it can move under its own power.

If the fighter was pulling negative Gs, it may well fly into its own missile.
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You got a point there, although those issues can be taken care of by way of programming of FCS, avionics and pilot training, although that means there're some limitations on what the pilot can do during firing. That's probably how the F-22 does it. The J-20 can have it both ways with the advantage that the missile was already in the air stream before it was ejected and therefore has more stability and controllability.
 
plawolf

plawolf

Lieutenant General
Quickie said:
You got a point there, although those issues can be taken care of by way of programming of FCS, avionics and pilot training, although that means there're some limitations on what the pilot can do during firing. That's probably how the F-22 does it. The J-20 can have it both ways with the advantage that the missile was already in the air stream before it was ejected and therefore has more stability and controllability.
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The F22 rail launches its AIM9s as well. Its only the AMRAAMs that are drop launched.

No one drop launches dogfighting missiles, and there isn't really much of a reason to want to drop launch them, so why bother with all the added complexity and limitations on the pilot?
 
Quickie

Quickie

Colonel
Even with a rail launch, the missile is basically left on its own the second it has left the rail, so the same limitations would apply, at least during sharp turns. The pilot still wouldn't want to launch the missile from the rail if the aircraft is making a sharp turn into the missile launch direction.

The other thing is with the side bay door closed, the missile would still encounter less air turbulent than the case with the F-22 with the bay door opened.
 
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latenlazy

Brigadier
Quickie said:
Even with a rail launch, the missile is basically left on its own the second it has left the rail, so the same limitations would apply, at least during sharp turns. The pilot still wouldn't want to launch the missile from the rail if the aircraft is making a sharp turn into the missile launch direction.

The other thing is with the side bay door closed, the missile would still encounter less air turbulent than the case with the F-22 with the bay door opened.
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I think the difference is that when the missile is rail launched, the motor has already been turned on at the point of separation, which allows you to program the missile to maneuver away from the fighter. The risk is that when you drop launch there's that moment where the motor hasn't yet turned on, which means it can't maneuver away from a potential intersection. That or even once the motor's fired it may not have enough room to maneuver away from an intersection.
 
plawolf

plawolf

Lieutenant General
latenlazy said:
I think the difference is that when the missile is rail launched, the motor has already been turned on at the point of separation, which allows you to program the missile to maneuver away from the fighter. The risk is that when you drop launch there's that moment where the motor hasn't yet turned on, which means it can't maneuver away from a potential intersection. That or even once the motor's fired it may not have enough room to maneuver away from an intersection.
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Exactly, when a missile is rail launched, it only leaves the rail when it is moving under its own power. With an IRAAM, you would only launch when you have a solid tone, so the missile has the target locked and is homing in even before it leaves the rail. IRAAMs are also typically equipped with solid rocket engines tuned for maximum acceleration, and the missile would achieve its max speed within a few seconds. That means that it would be pretty damn hard, if not impossible for the launch aircraft to hit its own missile upon launch even if the pilot wanted to. Training and just common sense should be enough to allow pilots to launch at almost any point in any maneuverer with minimal risk.

With drop launch, there is a crutial half second or second or more, when the missile has left the aircraft but has not yet started its engines, and as such, if both you and your target at doing hard turns, the missile could easily loose the lock before it has power to steer itself to keep the target in its field of view.
 
Quickie

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Colonel
latenlazy said:
I think the difference is that when the missile is rail launched, the motor has already been turned on at the point of separation, which allows you to program the missile to maneuver away from the fighter. The risk is that when you drop launch there's that moment where the motor hasn't yet turned on, which means it can't maneuver away from a potential intersection. That or even once the motor's fired it may not have enough room to maneuver away from an intersection.
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It's a given the missile is on its own power and control as soon as it leaves the rail. The problem is the change in the direction of the missile thrust is not instantaneous. Assuming the fighter is making a hard right turn and trying to launch the right side AAM, at the point the missile leaves the rail, its acceleration towards the (specifically, the centre of) turn has suddenly become zero since the missile TVC is only beginning to change the direction of the missile and its acceleration into the turn. During this change, there is still the danger of the fighter and missile crossing path, not to mention the missile exhaust would in that instant be directed towards the aircraft. So, in the end, pilots will still have to deal with the issue of the risk of launching missiles and how best to launch missiles in different situation, notwithstanding the problem is probably less of an issue with the rail launched method at lower G and they are handled differently between the 2 methods of launch.



plawolf said:
Exactly, when a missile is rail launched, it only leaves the rail when it is moving under its own power. With an IRAAM, you would only launch when you have a solid tone, so the missile has the target locked and is homing in even before it leaves the rail. IRAAMs are also typically equipped with solid rocket engines tuned for maximum acceleration, and the missile would achieve its max speed within a few seconds. That means that it would be pretty damn hard, if not impossible for the launch aircraft to hit its own missile upon launch even if the pilot wanted to. Training and just common sense should be enough to allow pilots to launch at almost any point in any maneuverer with minimal risk.

With drop launch, there is a crutial half second or second or more, when the missile has left the aircraft but has not yet started its engines, and as such, if both you and your target at doing hard turns, the missile could easily loose the lock before it has power to steer itself to keep the target in its field of view.
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Not to be mistaken that I'm arguing the advantages of rail launch and eject-and-launch of SRAAM. I was saying the J-20 has the option of using either. Btw, there may be situation where the eject-and-launch method may have more merit in certain situation, for example, where you need to hide the heat signature of the burn of the AAM until only after the fighter have make the turn, or to protect the RAM material or for whatever reason there may be.

Anyway, this is just my take of the moment. There's still the question of a smaller missile having enough stability after being ejected because of its smaller mass. We know that bigger AAMs have no such problem of stability.
 
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