EUS/Skylab-II with an Xenon atmosphere and a Cryogenic Xenon cargo to loft ISS to GTO and beyond

Con ops; SLS lofts EUS and Skylab-II to dock with ISS. EUS uses Xenon as a ullage gas and SEP propellant.The Skylab-II is pressurized with Xenon.The stack docks with ISS and brings a cargo of Cryogenic Xenon to pressurize the ISS.  EUS performs a chemical burn to depletion and then switches over to SEP operations.The chemical burn is needed to Loft the ISS/Skylab-II stack above the atmosphere so that the SEP does not have to fight atmospheric drag from the ISS solar arrays.Shortening the travel time through the Van Allen belts is useful too.The EUS then becomes a wet lab habitat.

The ISS pressurized volume of 916 m³ would hold 6 tons of Xenon ( 916 x 5.9 Kg = 5,404 Kg)

The Skylab-II would hold   495 cubic meters of Xenon (495 x 5.9 Kg = 2,920 Kg)

EUS Xenon ullage gases would represent at chemical burn out and with a 495 M3 Hydrogen tank ( 495 x 5.9 = 2,920 Kg)

EUS Xenon Ullage gases for the LOX tank?

This is 11 tons of gases Xenon short of the 30 tons needed However the 30 tons of xenon needed from LEO does not account for the EUS burn

ISS weight (420 tons)

Skylab-II weight  37,300 Kg (37 tons)

EUS dry mass weight 11,853 Kg (12 tons)

http://www.aqua-calc.com/calculate/volume-to-weight

EDIT Dec 2017

These two papers discuss LH2/LO2 zero boil-off stage lofted to  LEO to a 10 day HEO by a SEP system through the van Allen belts over two years (80 to 100 tons)

11-0971 10 day HEO

11-2974_A1b 10 day HEO

I think 100 tons payload to a 10 day HEO is less than 1/4th the weight Of Xenon propellant (20 tons?) or 3.1Km/s

So 469 tons x  .20% is 93 Mt of Xenon  we argue mass fractions savings could be had by cryogenic Xenon tanks