It is a lot cheaper to fleet together unarmed transports with warships, which does the same job you are trying to do without losing the expense of the weapons when you lose the transport ship during the invasion.

Yeah, I figured that. In this game I just already had a transport near an enemy planet and my warships were several turns away (bad luck mixed with personal fatigue) so I decided to do a quick upgrade. Guess you learn something every day.

~Nero

I find armed transports work very well if you design them right. If you don't believe me, I'll let you have a chat with the Santa Clause class.

Whether or not it's a total waste is debateable. In most cases, I find they make perfect mainline combat ships, and I can afford to sacrifice one or two to take over a planet when I know I can't afford to keep a fleet stationed on it for very long. I typically don't send out transports right off the bat because I first want to neutralize all enemy fleets before I start conquering planets.

I had considered something like that myself at one point: "Hey, if I just put one troop module on each of my ships, they'll still be pretty effective in combat and I won't have to worry about escorting them or having the computer wiping out a stack of undefended transports. Plus, all of my fleets will always be able to invade." Problems there are:

(1) any ship you lose now will also mean losing troops. True, you are spreading your eggs into more baskets by diving your soldiers among more ships, but it's generally not too big of a deal to keep defenseless transports away from the AIs. With the latest patch, there's no more "first strike" so you will be losing more ships in combat, and therefore, more troops.

(2) as others have said, you lose tranports in the invasion attempts. If I recall correctly, you lose any transport that can't be completely filled up with soldiers after the invasion. So, let's say you invade with 5 armed ships each containing a transport module (so 2.5 billion troops total). Now let's say at the end, only 900 million survive. Bam, you're out 4 of your 5 ships (there's only enough to completely fill one ship with 500 million soldiers). Not only do the base hulls cost more than a cargo hull (smalls cost the same as cargo right?) but you also lose all the extra cost from the weapons and defenses (defense is very expensive) that you put on them. It'd be a very different story if your transport ships didn't magically disappear during an invasion (and personally, I'd prefer that you didn't lose them), but as it stands right now, it seems like quite a waste to me.

There is no debate. A ship that's had weapons placed on it, and the expense of doing it's job properly, and WILL instantly die if it enters battle, or be wasted upon invasion, is a complete and utter waste of money since 1.2. Before, they had limited use. Now, they're total crap.

For later on in the game, I do generate a large capacity, fast transport primarily for population shifting - particularly to "new" planets. On these I will put token weapons & defenses to take advantage of military starbases if needed.

this is all true but i just don't like to send unarmed ships into combat

Well, you don't - if you are making invasion ships the way to go is to maximize the speed and sensors of the ship so you can keep out of trouble. If the enemy warships have more legs than your transports - you need to do more research before you take him on....