Near Term Space Exploration with Commercial Launch Vehicles Plus Propellant Depot, Dr. Alan Wilhite and Dr. Douglas Stanley, Dale Arney and Chris Jones, GRAs Georgia Institute of Technology/ National Institute of Aerospace

"The Propellant Depot Hypotheses

* Large in-space mission elements (inert) can be lifted to LEO in increments on several medium-lift commercial launch vehicles (CLVs) rather than on one Heavy Lift Launch Vehicles (HLLVs)
* The heavy in-space transportation mission elements are beyond the payload capability of medium-lift CLVs; however, 80 to 90 percent of their mass is propellant that can be delivered in increments to a Propellant Depot and transferred to the in-space stages
* Saves DDT&E costs of HLLV
* Low-flight-rate HLLV dominated by high unique fixed costs. Use of CLVs eliminates these costs and spreads lower fixed costs over more flights and other customers.
* Use of large re-fueled cryo stages save DDT&E/ops costs for advanced propulsion stages (e.g., SEP)"