Distributed Launch - Enabling Beyond LEO Missions

Abstract

Mission planners currently are limited by the mass rockets can launch to the desired destination. Mir and the International Space Station (ISS) have bypassed this limitation by transporting hardware into orbit across numerous launches. So far this tact has not been employed for destinations beyond Low Earth Orbit (LEO). This paper describes the use of multiple launches (potentially of different rockets) and propellant transfer to enable missions that are impossible today. Such missions include very large National Security Geosynchronous Orbit (GSO) satellites that are beyond the Delta Heavy Launch Vehicle capability, Commercial resupply of Cis-Lunar stations, or missions to the Moon and Mars. The method of launching cryogenic propellant, storing it for weeks or months in a disposable Drop Tank, and then transferring the liquid hydrogen and liquid oxygen into a cryogenic upper stage such as Centaur, Delta Cryogenic Second Stage, or Advanced Cryogenic Evolved Stage (ACES) to propel the mission to the desired destination, is coined "Distributed Launch". This paper describes the Distributed Launch concept and summarizes relevant Atlas/Centaur and Delta flight results and ongoing testing at ULA, Yetispace and National Aeronautics and Space Administration (NASA) supporting the required enabling capabilities. The current technology readiness level of enabling technologies will be described along with the ongoing technology development at ULA that will enable distributed launch in the near future.

A Flexible Lunar Architecture for Exploration (FLARE) supporting NASA's Artemis Program

“…This cryogenic propellant is chosen for both the SpaceTug and the human lander reference design. The original Titan/Centaur was designed to support an 8-h mission with a boil-off of 2%/day [ 34 ]. ULA has developed and patented numerous concepts to store propellant on-orbit [ 35 , 36 ].…”

“…A new design, using the Centaur upper-stage as a secondary tank, called the CRYogenic Orbital Test (CRYOTE) concept, conceives of up to 1 year of storage of cryogenic propellants on-orbit [ 37 , 38 ]. Building on CRYOTE tests, the next ULA concept uses a “Drop Tank” which waits in LEO for “days, weeks, or even months” to refill a Centaur upper-stage launched on a subsequent mission [ 34 ]. The Drop Tank remains attached to its depleted upper-stage and spins slowly (1°/sec) to provide centrifugal acceleration that settles the cryogenic fluids.…”

“…A challenge of cryogenic fluid transfer on-orbit is evolved gas release during the fill process. “No-vent-fill” designs, tested by NASA in the 1990s [ 43 , 44 ], use cold liquid thermodynamic properties to condense the vapor in the tank [ 34 ]. In 2019, a company built an experiment “Furphy” on the ISS that successfully demonstrated the transfer of water on-orbit [ 45 ].…”