Introduction
The Ra’ad Air Launched Cruise Missile (ALCM) is a peculiar system. It has long been rumored that it is too big to be carried by anything but the Mirage aircraft of the PAF. The purpose of this article is twofold: understand the design decisions made while designing the Ra’ad and what can be done to evolve the design. Hopefully, by the end we will appreciate why the Ra’ad is the way it is and try to think of ways to evolve it.
Basics
Weight
At 1,100 kg the Ra’ad is a rather heavy air launched weapon. However heavier ALCMs exist (Storm Shadow, Taurus) and are carried by aircraft with less clearances than the Mirage. Weight is not the key issue here.
Size
The Ra’ad is a significantly large missile. The following drawing has been made after many pixel-counting exercises and is a good ballpark estimate of its size.
View attachment 313914
DISCLAIMER: Pixel counting by its nature is inaccurate and these numbers could be off by up to 10%. Nonetheless these numbers give us valuable insight which we previously lacked.
Role
The Ra’ad is designed with a payload of 450 kg. This suggests that it is primarily designed to carry a nuclear payload or a large conventional payload against hardened targets. This differentiates the Ra’ad from other smaller stand-off weapons like the SOM, H-2/H-3, JSOW. Perhaps the most similar system to the Ra’ad is the AGM-158 JASSM picture below:
View attachment 313915
The JASSM is a 1000 kg system with a payload of 450 kg as well.
Design of the Ra’ad
A casual glance at the Ra’ad shows the “simple is better” approach being employed to the fullest. It is perhaps the most basic design one would come up with for a 1,100 kg ALCM. This is not necessarily a bad thing. Being the first ALCM designed by AWC it makes sense to start off with the basics.
The fuselage has a square cross section allowing easier manufacturing and at the same time reducing the height for the same volume (only slightly).
Another upside to using a rectangular cross section is that it reduces the tail area needed for stability (more on this later).
Issues
Probably the biggest issue people have with the Ra’ad is that it is too tall and wide to fit under most aircraft operated by the PAF. I will now attempt to break down why this is so.
As pointed out earlier the Ra’ad is a very large and heavy system even though it needs to fly like an aircraft. The reason aircraft have a vertical tail now comes into effect. Ideally speaking we want any small disturbances in the desired trajectory of flight to be taken care of “naturally” by the design of the aircraft. I will try to explain how this is achieved by the vertical tail as simply as I can to make it accessible to most of our readers. This is called positive stability.
View attachment 313924
An effect similar to the tail is provided by the fuselage with respect to yaw stability. A square fuselage provides more of this effect.
Roll Damping
As one would imagine the heavier the aircraft the more tail and wing area is required for “enough” positive stability. The Ra’ad is a heavy aircraft with very small wings so roll damping is small. This would mean for enough roll damping the designers have to compensate with more tail area in the form of ventral fins. The farther away they are from the center of mass of the missile the better they will perform as they produce more moment for the same area. It is for this reason they extend below the fuselage (in contrast to the vertical tail that are in line with the fuselage).
View attachment 313917
As the above image illustrates the vertical tail adds little or no roll damping and it is for this reason two ventral fins are there (among other reasons).
Yaw Stability
Yaw stability is provided by the vertical tails. It is evident that because of the mass of the missile a large vertical tail area is needed which is provided by two vertical tails.
View attachment 313918
The JASSM on the other hand employs one rather large vertical tail.
Pitch Stability and Authority
For very similar reasons an aircraft also needs a horizontal tail for stability. On top of that it needs it to have authority over pitch of the aircraft. Again the heavy weight of the Ra’ad means rather large horizontal tails are needed which make the missile 1.25 meters wide.
Reasons for Large Mass
The above argument begs the question why is the Ra’ad such a heavy system for the capability it provides.
Ra’ad
1100 kg
350 km range
4.88 m length
450 kg payload
JASSM
1021 kg
1000 km range (ER version)
4.27 m length
450 kg payload
The reasons for this can be only speculated but I suspect that:
1. The Powerplant being used is heavy and inefficient compared to JASSM (definitely true).
2. The subsystems are not evolved enough to be compact and light. These include INS systems, hydraulics/pneumatics/electric actuators.
3. The subsystems are not designed or modified for the Ra’ad to save costs and therefore pack poorly inside the missile.
Geometry
All this brings us to the issue of integration on PAF platforms.
The Mirage 3 can easily carry the Ra’ad ALCM and most importantly the addition of the cruise missile does not decrease the maximum permissible rotation angle (highlighted in red).
The situation is very bad with regards to the JF-17. The maximum permissible rotation angle is halfed and there is very little clearane with the ground. This makes it all but impossible for the JF-17 to carry the Ra’ad on its centerline hardpoint.
Perhaps it is also important to consider whether the wing hard point can carry the Ra’ad.
Even though vertical clearances are taken care of but the Ra’ad is so wide that it will interfere with the landing gear/ventral fin of the JF-17 and possibly any weapon system mounted on the hardpoint next to it.
