Chinese air to air missiles

plawolf · Dec 22, 2020

silentlurker said:
You mean pl-21? or a second pl-15 sized ramjet aam

The PL21 is surely too big for internal carriage?

The PL15 has impressive performance, but I think a ramjet missile would allow similar if not superior performance in the same sized missile, if not smaller. And smaller is what you want for internal carriage.

silentlurker · Dec 22, 2020

I mean, the ramjet and air scoop itself takes a certain amount of space as well, look at how big (width-wise) the scoop is on the Meteor for example. Not a issue for external hardpoints but might cause problems in an internal bay where the missiles are right next to each other unstaggered.

siegecrossbow · Dec 22, 2020

plawolf said:
The PL21 is surely too big for internal carriage?

The PL15 has impressive performance, but I think a ramjet missile would allow similar if not superior performance in the same sized missile, if not smaller. And smaller is what you want for internal carriage.

Tradeoff with ramjet is that it has worse maneuverability at the terminal phase of interception.

plawolf · Dec 22, 2020

silentlurker said:
I mean, the ramjet and air scoop itself takes a certain amount of space as well, look at how big (width-wise) the scoop is on the Meteor for example. Not a issue for external hardpoints but might cause problems in an internal bay where the missiles are right next to each other unstaggered.

AAM ramjet inlets usually sit under the missile body, so should pose no issues for internal carriage since it’s width, and not depth that is the main limiting factor for the J20.

plawolf · Dec 22, 2020

siegecrossbow said:
Tradeoff with ramjet is that it has worse maneuverability at the terminal phase of interception.

Isn’t it the other way around?

Ramjet should have greater range if the body of the missile and fuel mix are the same. As such, it should be fully powered for a longer part of the flight envelope, which should give it better chance of having better manoeuvrability in the terminal phase, owing to being still powered, than even the PL15’s dual pulse motor, as if the second stage runs out of propellant, it’s still going to be going off inertia only.

latenlazy · Dec 22, 2020

plawolf said:
Isn’t it the other way around?

Ramjet should have greater range if the body of the missile and fuel mix are the same. As such, it should be fully powered for a longer part of the flight envelope, which should give it better chance of having better manoeuvrability in the terminal phase, owing to being still powered, than even the PL15’s dual pulse motor, as if the second stage runs out of propellant, it’s still going to be going off inertia only.

Your instantaneous impulse, especially at higher angular changes, is much lower for a ramjet missile than a rocket. That matters a lot for the terminal phase.

plawolf · Dec 22, 2020

latenlazy said:
Your instantaneous impulse, especially at higher angular changes, is much lower for a ramjet missile than a rocket. That matters a lot for the terminal phase.

True, but I think the underlying assumes are key here. You are assuming both to be powered in the terminal phase, while I am considering scenarios where the ramjet is still powered but the rocket has run out of propellant.

Modern counter AAM tactics is usually a game a attrition and range, where fighters try to bleed incoming missiles of all their propellant and energy before the missile can get close enough to engage, rather than super-manoeuvrability last minute extreme G jinx’s. As such, I value longer range over raw turning ability. Because even with the ramjet’s inferior terminal agility, it’s probably still far more than what fighters could hope to reliably shake off if it gets within range.

Blitzo · Dec 22, 2020

plawolf said:
True, but I think the underlying assumes are key here. You are assuming both to be powered in the terminal phase, while I am considering scenarios where the ramjet is still powered but the rocket has run out of propellant.

Modern counter AAM tactics is usually a game a attrition and range, where fighters try to bleed incoming missiles of all their propellant and energy before the missile can get close enough to engage, rather than super-manoeuvrability last minute extreme G jinx’s. As such, I value longer range over raw turning ability. Because even with the ramjet’s inferior terminal agility, it’s probably still far more than what fighters could hope to reliably shake off if it gets within range.

Dual pulse or multi-pulse motors.

PL-15 is known to be dual pulse, I suspect this new missile would be at least the same.

That said I imagine it's not a clear cut decision, and ramjet vs dual/multi pulse motor has been debated ad nauseum as well over the years. Benefits of ramjet (sustained energy) but its disadvantage of parasitic drag and size are known.

silentlurker · Dec 22, 2020

latenlazy said:
Your instantaneous impulse, especially at higher angular changes, is much lower for a ramjet missile than a rocket. That matters a lot for the terminal phase.

??? Impulse is the integral of force over time, how can aything have instantaneous impulse?

Blitzo · Dec 22, 2020

Deino said:
But the question is, is it a true new missile or - and at least IMO those in that model looks so - a variant of the PL-15 with folding wings?

It looks like there are more differences than just folding fins.

Red: rear fin geometry (folding?)
Yellow: two different protrusions (forward and behind mid fins) not on PL-15. (?datalink or guidance related addition?)
Green: different mid fin geometry and placement.

Chinese air to air missiles

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