by flying_neko
A quick computation reveals that orbitals compare rather poorly, in general, to the advanced techs: robotics, economy, science and mining.* Cost: Advanced Economy, Science and Mining cost 1-2 science more (once), but orbitals cost 5 materials each, plus a fraction of an action to build them. That's 5 materials + 1-2 money per orbital. Advanced Robotics costs 1-2 science *less* than Orbitals. As someone said, you may be better off building Cruisers or Monoliths or holding a "virtual fleet" with those materials (http://boardgamegeek.com/thread/740382/virtual-fleets)
* Return: Advanced Economy, Science and Mining allow you to colonise at least two or maybe three planets each. That may be a bit less than what you can do with Orbitals, but only if you can afford to spend at least 20 materials and two or three actions (including an influence action if you want to speed up the colonisation) on Orbitals. Advanced Robotics gives you an instant disc, which is a bit more than one orange planet. Not much, but for a very low price.
* Strategy and externalities. Advanced Robotics cannot be taken from you under any circumstance. You can be denied use of Advanced Economy / Science / Mining if you lose a hex, but your enemy cannot use it herself unless she has developed the same technology. A hex with an Orbital is very, very desirable for your enemies, as others have said before.
So IMHO:
