Ramjet missiles

[WelshZeCorgi]

So what are the benefits of ram jet powered missiles? Are there any downsides to ram jets when compared to rocket propellant? 

 

(I mean fox 3s: Meteor, 120 and R77, but yes if you want to include antiship or other hypersonic missiles, sure.)

Edited April 24, 2021 by WelshZeCorgi

[G.J.S]

They are safer, as there is no need to carry combustible oxidiser, and also the missile can have much longer ranges or burn times.

Only downside I can think of is that you need at least a couple hundred knots at launch to enable the engine to work.

[jojo]

3 hours ago, G.J.S said:

They are safer, as there is no need to carry combustible oxidiser, and also the missile can have much longer ranges or burn times.

Only downside I can think of is that you need at least a couple hundred knots at launch to enable the engine to work.

That problem is generally solved with a booster stage to bring the missile to the most efficient speed. 

[WelshZeCorgi]

So ramjet tech has existed for a long while now, with the SR-71 coming to mind along with the ramjet prototypes predating it. 

 

I wonder why military tech took so long for ramjet A-A missiles to become a thing. What changed that they're now popping up? Maybe ramjets are difficult to miniaturize? Too expensive back then? 

[G.J.S]

On 4/26/2021 at 11:32 AM, WelshZeCorgi said:

So ramjet tech has existed for a long while now, with the SR-71 coming to mind along with the ramjet prototypes predating it. 

 

I wonder why military tech took so long for ramjet A-A missiles to become a thing. What changed that they're now popping up? Maybe ramjets are difficult to miniaturize? Too expensive back then? 

The -71 isn’t ramjet powered.
At speed it “behaves” similar to a ramjet, in that at M3+ ALL of its propulsive thrust is from the reheat (afterburner) section - dry thrust provides nothing - and inlet suck provides little if any propulsive force.
All thrust is from the burner plume only. 
From M1.8 upwards to M2.8+, inlets provide a suction that contributes up to 20% of the propulsive force but tails off the closer to M3 the aircraft got.

 

I believe that the problems in miniaturising effective Ramjet ‘engines’ is one of the main reasons for its seemingly late appearance given the relative age of this tech. And personally, I think I would rather have a chemical rocket engine rather than a Ramjet engine A2A missile, because in a slow turning fight a chem rocket will light off and give its expected thrust, a Ramjet would need quite a few knots already under its belt in order to go off like a scalded cat - not enough airspeed and a Ramjet engine will in effect choke itself with a rapid series of unstarts, producing nowhere near enough thrust. Chemical engines for missiles are IMHO always going to be more reliable.

[jojo]

On 4/26/2021 at 2:32 PM, WelshZeCorgi said:

So ramjet tech has existed for a long while now, with the SR-71 coming to mind along with the ramjet prototypes predating it. 

 

I wonder why military tech took so long for ramjet A-A missiles to become a thing. What changed that they're now popping up? Maybe ramjets are difficult to miniaturize? Too expensive back then? 

 

Most ramjet use liquid fuel, which is not really convenient, especially for storage.
One of Meteor missile achievements is to use solid fuel for the ramjet, and it throttle it, cut it and restart in terminal phase.

 

The main problem of traditional rocket propelled missile is that it looses effectiveness at long range since it's only slowing down.

 

Anyway, both liquid fuel or solid fuel ramjet use a solid fuel booster to accelerate to ramjet powered speed.

 

Off course a Meteor missile isn't designed for dogfight 

 

 

[Emu]

Meteor isn't technically a ramjet, it's a throttleable, ducted rocket, or CWDE (Continuous Wave Detonation Engine).  The propellant is solid and contains some oxygen but not enough for complete detonation, it is pre-burnt to form a throttleable plasma, which is then injected into the ram system where it detonates in conjunction with the hot air.

[Xilon_x]