Next generation Heavy Lift Launch Vehicle: Large diameter, hydrocarbon-fueled concepts

The Space Launch System (SLS) is envisioned as an heavy-lift launch vehicle (HLLV) that will provide the foundation for future large-scale beyond low earth orbit (LEO) missions. In support of the initial Mission Concept Review (MCR) milestone, several teams were formed during the initial Requirements Analysis Cycle (RAC) to identify reasonable vehicle candidates that could potentially meet the requirements that will be imposed on this system. One such team, dubbed RAC Team 2, was tasked with identifying launch vehicles that were based on large diameters (up to Saturn V diameter of 33 feet) and utilized high-thrust LOX / RP engines as a first stage propulsion system. While the trade space was relatively large, recent NASA activities examined similar concepts (namely the Heavy Lift Launch Vehicle Study in late 2009 and the Heavy Lift Propulsion Technology Study of 2010). While the findings from these studies were incorporated in the Team 2 activity, additional branches of the trade space were examined and alternative approaches to vehicle development were considered. Furthermore, Team 2 set out to define a highly functional and cost-effective launch vehicle concept. In this manner, a versatile two-stage launch vehicle concept was chosen as a preferred option. This preferred vehicle option has the capability to fly in several different configurations (e.g. engine arrangements) that gives this concept an inherent flexibility which allows the vehicle to meet a wide range of performance requirements without the need for block upgrades. Even still, this concept preserves the option for evolvability should the need arise in future mission scenarios. The foundation of this conceptual design is a focus on low cost and effectiveness rather than efficiency or cutting-edge technology. The approach and process used to decide on this concept is detailed in this paper, as well as the trade space that was examined leading to this preferred concept.