"Sieg" Cruise Missile, WIP, need assistance

[Mister Flylice]

Generally, I had an idea for a new cruise missile roughly based on the BrahMos II. Those of you that don't know, the BrahMos II is currently the fastest cruise missile in the world, with lab tests stating its top speed as Mach 5.26.

The Sieg is supposed to effectively be a heavy cruise missile; using the same propulsion of a BrahMos II but carrying a heavier payload, thus dropping its speed to say, Mach 4.8 (Help needed on that.)

I don't know much of what else to do regarding the design of the missile, which is why I've posted it here for help.

[V12]

How much heavier are we talking about here? Generally missile payload doesn't scale easily. Like a group of people standing on each other's shoulders, if the one of the top gains 10 pounds, the one under him has to be stronger, and below, and as the result, the one at the bottom needs to carry extra 100.

If you want just a small increase in payload, say from 200kg to 300kg, there are a few options.
Let's see... if the more conservative of current media info is correct, Brahmos 2 is a two-stage missile with a Mach 3 ramjet and a Mach 5 rocket-boosted second stage. If so, the second stage likely weighs about 750kg without propulsion. A speed drop from M5.26 to M4.8 would save about 150MJ, which amounts to 50kg of fuel, or 65kg with involved structure. The lower thermal stress easily allows to shave off another 35kg, arriving at an increase of payload with no other compromises.

If you want to increase the payload further, that requires more substantial weight savings with more consequences. Another component of the final stage is guidance. What is the missile intended for - the same use as Brahmos or a different purpose? If the latter, some guidance systems might become unnecessary, and can free up space for the payload.

If that's not the case, the two options are increasing the sophistication level and increasing total weight. For a missile intended to be deployed by 2014, sophistication increase is not an easy option if staying within solid MT, but might be doable for a disproportionate cost. Launch weight increase, clearly, allows for more payload, but check if your launchers can handle that.