A mid 21st Century technology species the Morvane on the planet Elvar in the yet to be discovered Yorvinia system are able to reach the orbits of planets as far out as Jupiter is from earth. On one of the gas giant's moons, a ancient artifact is discovered. The artifact turns out to be an alien shipyard class replicator, requiring only raw materials to reproduce almost anything. The system's asteroid belt provides enough materiel to duplicate their initial primitive ships far faster than they could hope to produce them on their home world. This home world is heavily factionalized and with one faction able to suddenly increase the size of their navy, they very quickly become so powerful that they sweep all opposition before them. This faction is a brutally repressive regime that is also a completely xenophobic religious group and run the planet with an iron fist.
All this occurred twenty-five years ago. Shortly after seizing power, a Romulan V-8 Bird of Prey entered the system and was surprised by the sizable local fleet. The Romulan ship was disabled and a bridge hit prevented the ship from being able to self-destruct. Even this old design was a quantum leap forward in technology for the Morvane. It took them twenty years to reverse engineer the captured ship enough to be able to repair it sufficiently for the alien shipyard to replicate the ship. The cloaking device was too badly damaged to repair and remains beyond the Morvane's ability to reverse engineer. The locals were able to replicate three-dozen ships, giving them a warp capable fleet and they called these ships Eagles of Righteousness.
This massive use of materiel stripped the system of nearly every vital resource available. Since they were now warp capable, they were no longer restricted to the limitations of their home world's system, the locals took to exploring for the means of expanding their domain. The nearest system to the locals was uninhabited and massive strip mining produced enough materiel to make four-dozen more ships. However, with only two planets, the system could not hope to sate the local's desire for power.
The next nearest system, was at warp four, a month away. There is a relatively new colony in this, the Parfeni system. Called Sanctuary, it consists of some 25,000 colonists. The PC's ship responds to a reported sighting of a Romulan Bird of Prey. Arriving hopelessly too late to intercept, the PCs can find no trace of the Romulan ship. The alien replicator is extremely efficient and has improved the original Romulan engine design in such a way that they produce so little waste that unless the area it is operating in is scanned within an hour, there isn't enough of a residual trace to detect. A check into background of the freighter Vagabond, and the captain, Lars Killian that made the report, finds he has a bad reputation. The PCs write the sighting off as "Crying Wolf" and return to their regular duties. The captain is livid and swears he'll prove the PCs wrong.
The Eagle raced back to the home world and the zealots of the religious order declare a jihad on the blasphemous "Non-people" on the newly found planet. Mustering six-dozen of the seven-dozen ships in the fleet, the zealots depart to cleanse the new world. En route, the freighter captain, doggedly trying to prove he was right flies right into the armada. The Vagabond is faster than the armada and flees sending a distress. The PC's ship is again closest, and by regulation, they have no choice but to respond. They manage to establish communications with the freighter and the screen shows the ship in shambles. The old and poorly maintain engines couldn't handle the strain of running at high speed for so long and failed allowing the armada to close. Captain Killian, despite his situation manages to smile as he proudly shouts "I TOLD you they were real!" The signal cuts off and sensors detect the Vagabond breaking apart. The PC's ship is far faster than the armada and they can easily break contact as even a ship as strong as theirs can not fight seventy-two Eagles alone.
The call for assistance brings grim news, the colony is in a fairly remote and newly expanded area and even though the PCs have five days before the armada arrives, only five other Starfleet vessels can arrive in that time. The reinforcements do not give Starfleet enough firepower to fight the armada as it currently stands or evacuate the colony in the time remaining. Figure the reinforcements arrive at staggered times with two arriving within eight hours (USS Inchon a Larson-class destroyer and the USS Buenos Aires a Loknar-class frigate), one within twenty-four (USS Canberra a Chandley-class frigate), one in forty-eight (USS Tripoli another Larson-class destroyer), and the last one a mere three hours before the armada (USS Gellak a Brenton-class cruiser). The colony has several shuttles and a few freighters but no planetary defenses.
The question is how can the PCs defend the colony against hopeless odds?
Given Starfleet's combat experience advantage, there are several things the PCs can do to even the odds prior to the Morvane Armada arrives:
Unpowered photon torpedoes can be sown in the armada's path as mines to slow the Morvane or to channel their path into an ambush site. A Starship Strategy/Tactics, a Starship Weapons Technology, and an Astrogation roll are needed to construct the mines and place them squarely in the path of the armada enough to delay their advance. The Morvane travel in waves of twelve ships each. Each ship in the lead wave has to roll a Starship Sensors at -20% and a Starship Strategy/Tactics roll to detect the mines in time to avoid the mines. If either roll fails, the ship move close enough to cause a proximity burst. This will do one-half damage of the photon's normal yield. If both rolls fail, the ship sustains a full strength hit. As the ships are moving in open space, they are traveling with shields down. After the first mine strike, they will raise shields. This doesn't stop the mine rolls, but will reduce damage to the armada.
Asteroids can be tractored to form an obstacle course, or towed at high impulse toward the armada to at least break up the formation. A Starship Strategy/Tactics, a Starship shields, and an Astrogation roll will plot the course of the armada accurately enough to impede their progress.
Using the asteroids as missiles is much more difficult. The above three rolls are required, plus an additional Starship Strategy/Tactics and an Astrogation roll plus a Starship Helm Ops to aim the makeshift missile correctly. The ships in the lead wave must critically fail a Starship Sensors roll to not detect the incoming asteroid. If the asteroid is detected, there is no chance of a hit. If my some miracle the asteroid hits, the unlucky and unshielded ship is completely destroyed.
The planet has a couple industrial fabricators. Using a few grams of anti matter, the PCs can make more mines than the ship can alone, but not an endless minefield. It will take a Starship Weapons Technology and a Structural Engineering roll to fabricate the mines. It will take an Astrogation roll to place them accurately. These mines are detected and avoided per the standard rules for mines.
The Morvane are ruthless, but do not have any experience in ship to ship combat, so some fancy ESO type maneuvers could go a long way to even the odds. The Morvane will be particularly vulnerable to Chain Collision, Exploit Weakness, "Watch and Learn," Shield Repulsing, and the Thruster Knockout tactics (eac rolled with a +10% bonus).
Given their xenophobic and zealous nature, negotiations are not an option.
The PCs can fight a retrograde operation that will succeed in delaying the armada. If PCs can beat the Morvane commander's Starship Strategy/Tactics three times in a row, they buy enough time for additional Starfleet ships to arrive. Each success represents an additional day of time, for each success after three, one additional destroyer has time to arrive. However, no more than three ships are close enough to arrive in time regardless of rolls.
After the PCs have whittled down the Morvane and are a day from entering the Parfeni system and having to stand and fight, the PCs receive a subspace signal that is from the Romulans! They have been contacted by Federation officials threatening all out war and they have categorically disavowed any knowledge of who is making this attack. They do NOT want war with the Federation and have sent their closest strike force to assist. The PCs should realize that even if they have the full eight ships possible, they can not fight so many even obsolete ships alone. The Romulan strike force consists of a V-30 cruiser, a V-27 cruiser, and four T-10 destroyers. This force is strong enough that with a lot of luck will just BARELY be enough to halt the armada. The PCs have a tough decision on their hands, do they allow Romulans into Federation space or do they try and stand on their own. A Starship Strategy/Tactics roll will know that fighting alone is a lost cause. A Federation Law roll will find a loose enough interpretation of the regulations that will allow the Romulans to assist.
If the PC's think of it, they can be the ones that send the above message to the Romulans, the risk to the captain is the assistance will not have the blessing of Starfleet as it will above. However, given the nature of the threat, there won't be any repercussions. Don't tell the PCs this! The captain will probably get a very stern explanation of regulations, but that will be the extent of fall out.
Since the Morvane attacked a Romulan ship and are in uncharted space, as soon as the Morvane retreat, the Romulans will cloak and pursue to find where these imposters came from and seek vengeance. The PCs will no doubt be curious about this as well and will want to prevent another attack from occurring. The planet Elvar is four days and eight hours away at warp seven and only three days away at warp eight. The GM should contrive to leave the Federation ships either non-warp capable or limited to warp seven by damage to give the Romulans the chance to reach the Yorvinia system first. The GM should also contrive to have the Romulan forces suffer the brunt of the losses in the battle with the armada. The rationalization for this is the Romulans are so incensed by these imposters that they attack with an unusual fury. The Romulan strike force should be reduced the V-27, the V-30, and no more than one T-10. The Starfleet destroyers and the Loknar will also sustain heavy damage due to their inability to maintain full 360 degree shields. The PC's ship and the Chandley, should survive the battle fairly intact.
On arrival in the Yorvinia system, the Romulans will immediately realize the significance of the replicator and will immediately move to seize the facility. They will beam over a strong contingent of marines to take control of the station and move to intercept any Federation ships. The Romulans will assert that they were the ones wronged by the Morvane and they will claim the replicator as compensation for their losses and damage to their reputation. The Romulans first action will be to "punish" the Morvane for their "Transgressions against the Star Empire." This punishment takes the form of a planetary bombardment. The Federation now finds itself in the awkward position of having to rescue the Morvane from the Romulans! Before the PCs can react, a number of Romulan ships decloak and move to block the PCs from intervening. The Morvane have the bad luck of being closer to Romulan space than Federation space and their reinforcements have arrived. The PCs are once again severely outnumbered! Since the Yorvinia system is near the backwaters of Romulan space, the ships that arrive will not be the top of the line like the initial strike force. The reinforcements will consist of six V-11 cruisers.
Reeling from the first wave of the planetary bombardment, the Morvane realize they face racial extinction and are quick to accept Federation help. The twelve rear guard Eagles move to join the Federation ships forcing the Romulans to stop their bombardment and fight the combined force. The Romulans will be hampered by the fact that they must protect "their" new facility. Starfleet will of course want to scan this incredible find, but can NOT allow it to remain under Romulan control. The PC's ship or if the Canberra is still in the fight, their marines can be used in an epic fight for the replicator. Of course the battle on board does critical damage to the device and will cause it to overload and be destroyed.
The alternative is the Romulans are ruthless enough to choose to destroy the device rather than let the Morvane or the Federation have the priceless prize and will fire on it even if their troops are still aboard. As soon as the replicator is destroyed, the Romulans cloak and break off. Any Romulan ship that can't cloak or go to warp, will self destruct.
It can be added that the scans made of the alien facility during the fight eventually lead to the invention of the replicators of the Next Generation.