You wrote. "Planumex was launched to become the main interplanetary cryptocurrency and currency for trade. As we approach the intergalactic age, the need for a single coin to be used throughout the galaxy will increase." And what will happen to the rest of the cryptocurrency? What planet of the solar system are you going to first establish trade relations with?
You raise a great question, "What will happen to the rest of cryptocurrency?"
It will continue on as you would normally expect where people in California are sending bitcoin to those in Dubi etc. However it will not be the forefront for those coins to be sent to mars, moon, or space. The way most of the PoW and some PoS coins require a different communication structure regarding blocks and the the chain be accepted as the "longest chain" this will ultimately not insensitive mining out in space as earth miners will probably clear block times faster due to latency. So in regards to what will happen, is they will remain being used on earth as normal.
In regards to, "What planet of the solar system are you going to first establish trade relations with?"
I can only assume this was ask for a quick laugh, however we do have plans to first partner with satellite providers to host our nodes with their technology. Essentially each satellite in space would act as a public node or what we refer to as "Satellite Nodes". NASA has been developing technology to allow for laser communication which would allow us to communicate via IP to IP or Peer to Peer across these "Satellite Node". Each node will communicate the chain across space and will hold all transaction data and verify with each of the nodes on a private network the "Planumex Blockchain". Our goal is first space transactions and confirmations than we aim to have transactions confirmed and sent from the moon and potentially even mars in the very near future. You can take a look at a diagram created by NASA showing how this might work:
http://blogs.discovermagazine.com/d-brief/files/2018/07/dtn-ssi.png