1. An old feature of FreeSpace 2...
Although SSMs (Subspace Missiles) may seem a new feature, their script were part of the main FreeSpace 2 code that got released with the game. They weren't used in the game for obvious balance issues, which resulted in certain overkill (or, at least, in consistent damage).
Thanks to the Source Code Project, the new versions of FreeSpace Open added full support for subspace missiles and dinky shockwaves - two features INFASA will be using for one of its most powerful and surprising weapons.
2. ...which is coming back with glory!
As it was clearly specified elsewhere, the player will see many on-board computer programs (OCPs) that serve a multitude of purposes. One of the programs that is finally being revealed is the Sledgehammer, the Martian development of the Warhammer program used by the GTA.
The Sledgehammer (as well as its rivals - read below for more info about the matter) is expected to lead the Republic to the successful creation of a powerful strike force, which may be obviously used for catastrophic planetary bombardments.
3. The Sledgehammer program
The Sledgehammer, mostly known as the primary program used by the Martian Republic's Talisman Brigade (name given to the Martian squadrons of GTB Zelos-class superbombers), allows a perfect interaction between a bomber's sensor systems and the remote guidance system of its torpedoes. A bomber making use of the Sledgehammer program can launch its torpedo and watch it entering subspace in a matter of seconds. The torpedo hasn't disappeared from the battlefield - it's just using subspace to move around its target and prepare to jump back at any moment to catch the target's gunner by surprise.
Thanks to the advanced sensors of Zelos superbombers, small subspace pulses at given frequencies can be sent to let the torpedoes jump back to the battlefield in a random location (and with their speed significantly increased) around their target. The gunners aboard the target will have only a few seconds left to react before the impact and the consequent explosion.
This kind of deployment is riskful, because the torpedo is still vulnerable to enemy attack before entering subspace and gaining speed. In case of successful interception, the torpedo may be destroyed only a few hundred meters from the bomber that launched it, thus causing the bomber itself (and the rest of the bomber wing in case of mass strike) to sustain massive damage from the torpedo's immense and disruptive shockwave. In order to solve this problem, the Sledgehammer waits for the torpedoes to enter subspace before arming their main charge. This safe move will protect the bombers, but it surely won't make life any easier for the bomber's target, which will be hit by the armed torpedo. Even interceptor pilots who have to take the torpedoes down after the jump may face certain death if they're not careful.
Despite the encouraging additions, there's another real problem to deal with: the possible destruction of the bomber during the SSM strike procedure. The problem has been solved thanks to a recent upgrade of the Sledgehammer, which ensures a quick transmission of vital targeting info to all torpedoes should the integrity of the bomber be severely compromised. This allows the subspace torpedoes to hit their target even without the bomber's guidance systems.
4. The Grand Cross
The program was the way too useful to see its use limited to bombers, only. It became pretty clear that it could be easily used to reinforce planetary defenses and ensure a superb protection against strikes.
The basic infrastructures planetary defenses are very old, but still not up to date and all but incompatible with SSMs. The Grand Cross defense system, created by the Jovians and made public to the other factions of Sol, full merges planetary defenses with subspace torpedoes. Mars, starting from the Grand Cross, developed the Shield of Ares system. The Shield makes use of Mars' natural moons, Phobos and Deimos, to triangulate the position of incoming hostile warships and launch a large amount of SSMs to the designated targets for quick resolution.
5. Parallel development of the Warhammer and Grand Cross systems
As stated above, the Sledgehammer is a Martian program based on the GTA's Warhammer. Similarly, the Shield of Ares is based on the Jovian Grand Cross. This clearly means that the Martian Republic is in possession of specific development of basic technologies.
Because the Republic is not the sole faction in Sol to use the Zelos superbombers and derivations of the Grand Cross, the player can expect to see other variants of these technologies in INFASA. The Jovians themselves, for example, are supposed to be in possession of an incredibly advanced program that may make the Martian's Sledgehammer look like the result of amateurish work . The same principle may be applied to the Shield of Ares (which may result poor if compared to new and unknown upgrades of the Grand Cross).
For obvious reasons, the Jovians did not sell their most advanced technologies to the other major powers of Sol, and this will have certain consequences in the future.