There are only a few ways to make this effect happen. But, it's not possible to emulate a nuke explosion without ordering a computer to nuke the area with an: "ai script at location."
One of the ways you could do it, is to create a bunch of units for a computer player under the vessel and then killing the units under it. This will create a huge explosion of any sort of color or size. But it does have the tendancy to have the unit unplacable error. If you like, you may use air units.
Actually, I think that's the only way. >_<