There's a world of difference between HG ships spinning about and using agility to jet about and avoid nuclear warheads blasting in vacuum, and the same ships trying to maneuver through dense atmosphere when the missiles come inbound and the nukes go off. Some ideas on combat rules in/near a gas giant:
Now you have a scenario where SDBs hiding deep in a gas giant are dangerous and useful, where capital ships in orbit are trying to drive them out by "depth charging".
You also have a potential to make fighters useful in this role: they're small, more expendable, have an easier time hitting with missiles if the base roll is low and the target can't use agility, and can be used as in-atmosphere forward observers. In addition, Striker allows point defenses to be used in dedicated support - in other words, escorting craft can use their defensive batteries to defend themselves or the escorted craft. To emulate the Striker point defense rules, allow the beam weapons of a squadron of fighters in the GG atmosphere to function as a single battery - factor depending on the number of guns ('cause Striker doesn't care about factor, it only cares about how many missiles get destroyed) - and don't apply a computer modifier ('cause that doesn't seem to make a difference for this purpose at Striker ranges).
Of course, we don't have to apply Strike or MT close combat rules. It's just convenient to apply the known rule set to the situation rather than go in blind and make up something entirely new, and it makes the role of the gas-giant-hiding SDB much more relevant and dramatic.
- Atmosphere affects weapon performance and maneuver:
- Atmosphere shortens beam weapon ranges (Striker) and presents a barrier to particle beams. Ships deep in the gas giant would be able to stay outside the effective range of beam fire from orbit while bringing scooping ships under beam fire. So, particle accelerators are not available, and beam weapons are not available for offense between deep SDBs and overwatch ships in orbit, though ships daring to go into the atmosphere to scoop (or fight) could trade shots with SDBs.
- Assuming both parties are close enough to trade beam fire, they're fighting in Striker-style air combat. They're running on 30-second turns, firing twice per turn; they may evade under Striker rules, gaining the agility defensive bonus. So, fire is exchanged every 15 seconds, and the craft get the benefit of their agility as well as computer rating. Easiest to use the High Guard weapons tables to reflect battery fire bonuses, rather than Striker's base 8+ (which, not coincidentally, is the odds for a F1 laser to hit, so it's a convenient bridge between the two rule sets). If you're running a situation where the scoopers get ambushed in atmosphere while the overwatch fleet is fighting a space battle with attackers in orbit, the gas giant battle's likely to be resolved and one side plummeting into the depths before a single High Guard turn is completed.
- Under Striker rules, missiles aren't affected by agility if their own agility equals or exceeds that of the target. The standard missile is either a 5G6 missile (Special Supplement 3) or a 6G6 missile (COACC). Let's assume the naval missile is a target-designated high-performance 6G missile, since a homing missile invites a chance of inadvertently hitting the forward observer and the navy'd use a better missile than civilians. So, take the High Guard missile attack table, give the missile a +4 in atmosphere (giving the F1 battery a 2+ to hit), modify only by difference in computer rating (reflecting use of ECM). Agility/evasion does not apply.
- Spinal mounts are not available for in-atmosphere ship-to-ship combat: particle accelerators are out in the first place, and there's no way atmospheric buffeting is going to permit anything remotely like enough accuracy to manage a spinal meson shot against an evading target less than 40 Km off. Meson bays are available.
- Under MT rules, streamlined ships hit a top speed (and therefore a maximum agility bonus?) unless they are also airframe, and the DM is based on the difference in speed between the two maneuvering craft, therefore potentially 0. Other than that, similar to Striker: the DM doesn't appear to apply to missiles, and many, many turns pass and many, many shots are traded before the standard HG turn passes. One could use the MT model for beam (and bay meson) fire instead of the Striker model, setting a maximum agility 1 for craft in atmosphere that are streamlined but not airframe, and allowing an attacker to use his agility to counter his target's agility. SDBs are most likely airframe, for obvious reasons.
- Nukes are more effective in atmosphere. Certain kill within 15 meters, or maybe to give them a fighting chance you could go with a 97 penetration, which translates to a -47 on the HG damage table, basically any nuclear missile hit generates a crit. (Actually, it'd be rather hard for them to be less effective than the way they're presented in High Guard.) Coupled with the way missiles are handled in atmosphere, the only real defense is to kill them before they go off.
- Atmosphere may hinder detection and tracking.
- Under MegaTrav rules,
- warcraft of TL14+ can detect craft hidden in gas giants (and vice versa) and lock onto them via power plant neutrino emissions. TL14+ craft in orbit fire normally (with those weapons able to be fired) on craft in the gas giant; TL14+ craft hiding in a gas giant can fire normally on craft in orbit (with those weapons able to be fired). However, this occurs under High Guard turns: once per 20 minutes. That may be a little slow if there's a friendly in there fighting for his life.
- TL12-13 warcraft hiding in a gas giant detect and lock on craft in orbit using mass detectors.
- Warcraft of TL13 might detect craft hidden in gas giants (8+) using neutrino sensors; if they successfully detect, they can lock on. (The gas giant's mass prevents the use of mass detectors to detect warcraft hiding there.)
- At TL12 or less, craft cannot detect or lock onto craft hiding in gas giants.
- At TL11 or less, craft in hiding cannot detect or lock onto craft in orbit unless they emerge from hiding. They can detect and respond to craft that descend from orbit into the gas giant's atmosphere (though, gas giants being large, one may require a roll to see how many turns it takes for them to get within range of the target).
- Under Striker rules, orbiting ships may use forward observers to fire at planetside targets; this can also be applied to targets in a gas giant.
- Engaging is not guaranteed. The hiding craft may descend to a depth at which forward observation is not possible due to atmospheric effects on sensors. Alternately, the hiding craft may directly attack the observer, but it is vulnerable to indirect fire while doing so.
- Indirect fire is at the Striker rate, 1 attack every 30 second turn, so there is clear advantage in putting an observer in the atmosphere and using indirect fire. "Forward observation" in this case consists of the observing ship, at a range of under 40 Km from a target, feeding sensor data directly from its sensors to the ship in orbit, with computers making the necessary correction to address the difference in viewpoint.
- Both meson and missile indirect fire are available, no deviation issues, just a normal to-hit roll for mesons and treat missiles as above when they arrive.
- A craft engaged in atmospheric spotting, or scooping, or combat has nowhere to hide; hiding craft may rise to its altitude and engage it in combat, with combat going by Striker's 30-second combat turns.
- For in-atmosphere craft able to fire spinal mounts or missiles up at ships in orbit, the same forward observation rule might apply, but with more space for maneuver, it's not likely an orbiting fleet's going to let them close to F.O. range. Firing occurs under High Guard rules using the High Guard turn. They also can't set range - that's entirely up to the ships in orbit. If they're at an altitude that permits missile fire, they can be fired on by missiles
- Under MegaTrav rules,
- Disengaging: no guidance here, we're on our own. Let's say a ship in atmosphere wanting to disengage to orbit needs 40 30-second turns (one HG turn) to rise out of the atmosphere and into vacuum, at which point it is at short range and under High Guard turns and rules. A ship in atmosphere wanting to disengage by descending could descend to deeper atmosphere in the same time: missiles would get crushed below a certain altitude, and let's say that forward observation becomes impossible at those depths due to atmospheric effects. That doesn't stop meson fire at TL14+, though it slows to the High Guard turn. Gives a situation where TL14+ ships in orbit are trying to slowly clear the GG of hostile SDBs by firing mesons at neutrino signatures - a slow process with low odds: assuming maximum agility and all other things being equal, the typical meson spinal needs a 9+ to hit (10/36), the meson bay an 11+ (and likely to be stopped by configuration or a very light meson screen).
Now you have a scenario where SDBs hiding deep in a gas giant are dangerous and useful, where capital ships in orbit are trying to drive them out by "depth charging".
You also have a potential to make fighters useful in this role: they're small, more expendable, have an easier time hitting with missiles if the base roll is low and the target can't use agility, and can be used as in-atmosphere forward observers. In addition, Striker allows point defenses to be used in dedicated support - in other words, escorting craft can use their defensive batteries to defend themselves or the escorted craft. To emulate the Striker point defense rules, allow the beam weapons of a squadron of fighters in the GG atmosphere to function as a single battery - factor depending on the number of guns ('cause Striker doesn't care about factor, it only cares about how many missiles get destroyed) - and don't apply a computer modifier ('cause that doesn't seem to make a difference for this purpose at Striker ranges).
Of course, we don't have to apply Strike or MT close combat rules. It's just convenient to apply the known rule set to the situation rather than go in blind and make up something entirely new, and it makes the role of the gas-giant-hiding SDB much more relevant and dramatic.
