Yes, I reviewed Fires of Heaven some time ago, as a role playing game supplement. I am now reviewing the section of it that was dedicated to the spacecraft construction, operation and combat rules as a separate game onto itself. The author described the rules as a 90 page set of space wargame rules with RPG elements added in, and as such that's what I'd reviewing it as.
The FOH spacecraft rules follow the mold set in EABA and Stuff, with some minor modifications. The scale is generally 1 hexagon = 1000 kilometers, or a 'Megameter" if we want to be all metrically correct.:p One turn = 6 minutes.
There is a spacecraft scale version of the ubiquitous EABA universal chart thoughtfully provided.
The first topic is construction, and I'll wade right into it. The standard EABA measurement unit, the hexagon, has remained untouched by it's transplantation from conventional settings to the icy blackness of deep space, still measuring 1 meter across by 1 meter deep, and usually massing in at ~500 kg or so, but now some rules for material density can change this on occasion.
Ship construction is generally not radically different that many similar systems, but quite detailed in some areas. There are a limited number of systems available to buy, but you have wide options in the details of many systems. Systems take up volume and often mass as well, and may have power requirements. Your basic hull determines your available volume.
The setting is somewhat on the low end of technology in most SFRPG terms, Artificial gravity exists in limited availability, as does anti matter. There is a single FTL engine, the Rozkhov drive, a wide variety of conventional engines that work along Newtonian lines and a gravity drive used by an advanced race of hostile aliens.
Each type of conventional engine has it's own characteristics. Some are quite cheap to operate, like ion drives, but consume a lot of power and are of very limited thrust. (You will NOT lift off from a planet like earth on ion drives.)
Others offer more thrust at the expense of greater fuel demand and/or higher maintenance costs, or sometimes other issues. (If your engine exhaust consists of superhot, radioactive, toxic metal vapor, don't expect to be allowed to land in inhabited areas.)
Sensors are curiously limited in detail, but well covered in terms of operation and effect.
Weapons are limited to lasers, particle accelerating ion cannon, missiles, short range plasma weapons and point defense gauss hypervelocity fltechette style weapons. The advanced Vorn have a gravitic shear that's quite nasty.
All in all, ship construction is a wonderful balance of abstraction and detail that can produce vessels of adequate detail to use as RPG settings and still be fully serviceable as wargame units. There are even some brief but very useful notes on making RPG maps based on the designs.
The rules for the production, distribution and use of power are a jewel, making energy management often a tactical necessity.
One thing that most people interested in FoH's spacecraft rules will need to understand is that the game system is usually not linear in effect. Most things in the EABA system are measured in levels, and levels are usually expressed as dice of effect, Each level represents a roughly 1/3 increase in power, energy, strength, etc. Every 3 levels equals one dice. Differences of less than 3 levels are expressed as modifiers of +1 or +2. Thus a weapon that does 2d+0 damage has 1/2 the total energy or effect as a weapon doing 3d+0, and a reactor producing 3d+2 power is producing about 66% more total energy than a reactor producing 3d+0.
So it's important to remember, for example, that 5 1d+0 reactors will NOT power a system with a 5d+0 energy demand, it would take 2^4, or 16, 1d+0 reactors to produce enough energy to run a single 5d+0 power demand device. (Note that one large reactor is more efficient than several little ones, so a single 5d+0 reactor takes up a lot less space and fuel than 5 1d+0 reactors.) It also takes a lot more power to go from 10d+0 to 10d+1 that it takes to go from 3d+0 to 3d+1, or even from 3d+0 to 5d+0.
Once the non linear nature of the EABA system is understood, it gets quite easy to use.
After a ship is constructed one can create a customized hit location for it quite easily under the FoH rules. The total ship's volume is divided into 36 hit locations, and each system is assigned a number of hit locations based on it's volume. Thus ships that are mostly cargo will take cargo hits far more often than a ship with little cargo capacity.
Also, one can arrange the hit locations to reflect a front to back, right to left or inside outside arrangement to make systems inside the ship harder to hit than ones on the surface of the hull.
Making a hex map is quite easy now, as you know how many hexes a system takes up and thus how many hexes of floor space it needs on a map.
Starship level weapons are actually fairly weak in FoH, when compared to the typical instruments of mass destruction carried by most SF vessels. While people are used to WW2 battleships carrying gigantic cannon, far larger and more potent than their counterparts on land vehicles, ships in FoH are lucky if they have a weapon as powerful as a tank's main gun, and many are not much more powerful than an assault rifle due to the fact that the weapons in FoH must travel vast distances, thus they require huge amounts of machinery to focus and aim them across tens of thousands of kilometers. Often the focusing and aiming systems of a weapon will be as large or larger than the weapon itself, and even so a lot of energy is lost over the distance.
This does not make ships weak, however, as a ship that needs to impress a planetary population can always carry nuclear or antimmatter missiles which can be used once the defending spacecraft have been defeated.. It also makes heavily armored fightercraft mounting much shorter ranged but more powerful weapons plausible.
Note if you're willing to sacrifice a full firing arc you can have a honking big gun on your ship's prow, sort of a small spinal mount, but it will have problems hitting targets not in your forward arc.
Ships have damage points and damage levels, when a ship suffers enough damage points it can cross a damage level, reducing it's effectiveness and imposing a penalty on virtually all actions the ship takes. However, larger ships may not have a vast number of damage points in the FoH system, rather the larger a ship is, the harder it becomes to damage it.
The larger a ship is, the harder it becomes to do actual damage to it in overall terms. Ships have damage limits that limit how much damage an attack can do in one hit, and some large ships have damage limits below zero. Several things can affect a damage limit, Explosive weapons increase a ship's damage limit, allowing explosive weapons to have more damaging effects than normal ones. Also, multiple hits that penetrate armor in a single turn can raise a ship's damage limit for that turn.
Hits that penetrate armor but do not do actual damage to the ship can still damage systems and occupants. So it might be possible to shoot out a ship's engines, weapons, sensors, etc. while leaving the structure largely intact. Individual systems can be targeted, tho usually at penalties to hit.
The effect of weapons used inside ships are given rules for, and it's easier to damage a ship from the inside as the armor's mostly on the outside. So RPG level combat can be ran in parallel to ship combat.
All in all, the FoH combat system is a nearly perfect balance of detail and abstraction, and produces a wonderfully playable game that works at the RPG and wargame level. I think this may be the best set of ship construction and combat RPG rules I've ever seen.
Now, hopefully someday the author will expand upon and release this as a separate multi genre spacecraft construction and combat system with rules to cover numerous tech levels and settings that would allow it to be used for more SFRPG settings and to simulate popular SF genres. Things like full shields, cloaks, ships phasing in out of hyperspace, alternative FTL systems, etc.
That would be a great day for SFRPG players everywhere.