Considering Ad. Petrach claims it would take at least a decade to build one Knossos in order to reopen Delta Sup.-Sol node, it would mean that we would be looking at a time period of around 50 years before we could attempt to make our way home after the Lucifer blew the node. A lot could have happened in that time period.
Only 4 Vasudans made it through the node. Therefore, it is plausable that if they did settle on Earth initially, then there is the chance that they died out due to limited numbers. However, in saying this, I do not know if GTI and GTA headquaters had Vasudan consultants or scientists.
Considering this extended hiatus between home and the fleets, it could be possible that Earth either diverted a lot of resources into developing new craft capable of high speeds in order to investigate the possiblity of new undiscovered nodes within Sol. I did suggest that this is what the Ancients initially did when they first started collonising planets and systems.
Going on a tangent to my previous idea, it is also entirely credible that seeing as Earth has been attacked once before, the GTA implemented plans for an agressive defence of the node should it ever re-open. These plans could include RBCs, Corvettes, new destroyers or a Super Destroyer with the single intent of mullering anything that could come through the node.
My plan is simple then. We attempt to get communications through. We know from battling the Lucifer in Subspace that radio transmissions canget through, albeit with some interference. Therefore I suggest we station a Communications Science Cruiser as close to the Delta node as possible on as many GTA frequencies that we know of. If communications fail, then we send in 1 lone fighter in a recognised type such as a Hercules or a Ulyesses through the node. My theory being it is better to lose 1 fighter than the crew of a destroyer if Earth becomes hostile. If the fighter comes through unscathed, then we send a fleet consisting of 1 destroyer, (preferably Orion, but given they will be ancient at this time, we may have to settle for Hecate), 1 Science Cruiser and a Sobek, simply to show Earth that neither us or the Vausdans are hostile.