Development Program for An Advanced In-Line Reusable Launch Vehicle Concept Using a Small-scale End-Burning Solid and Hybrid Rocket Glider Demonstrator Approach

Abstract

This paper describes a development program for assessing and demonstrating technology required for an advanced in-line reusable vehicle concept which involves use of a frozen monolithic propellant as a load bearing member and phase-change in flight in an end-consuming manner. Relative motion between a forward crew/payload module and an aft/propulsion module allows for the ability to eliminate staging requirements on ascent and allows for the ability to reuse/return main-stage engines in an attempt to significantly reduce launch vehicle operational costs for affordable access to space. A sub-scale technology development program is presented here. The technology development program utilizes a set of designs for similarly configured small-scale end-burning solid and hybrid rocket powered glider vehicles to assess/demonstrate feasibility of various key technology elements for the full-scale vehicle concept. Groundwork for the sub-scale development of the full-scale technology elements vehicle concept is presented. Among these are: required ground systems to solidify propellant in-situ, retract facility ground systems prior to launch, the ability of propellant to fully bear thrust loads during flight (i.e., serve as a primary load-bearing element), vehicle integration system on ascent allowing controlled relative motion of the forward and aft modules, end-burning combustor and oxidizer feed system amenable to vehicle relative motion, and glide return of main-stage engines. We investigate a sequential plan to develop, assess, and demonstrate these technologies first with propellants that are solid at ambient temperature (solid motor and hybrid rocket propellants), then we address a sequential plan to similarly progress with propellants with melting points below ambient temperature. Sub-scale designs are presented for future ground and flight experiments of the development program. Nomenclature = inner radius, vehicle acceleration F = force = area = local gravitational acceleration * = throat area ! = constant of unit conversion, = / ! = outer radius ! = gravitational acceleration at Earth surface * = characteristic velocity h = height = cylinder diameter, wire diameter = moment of inertia = cylinder diameter, mean spring diameter !" = specific impulse E = Young's modulus = stress correction factor Nomenclature (continued) = length R = radius of cylinder = mass flow rate ℛ = mass ratio, vehicle M = vehicle mass, moment ! = yield strength / = oxidizer to fuel ratio t = time, thickness p = pressure, pitch lead T = tension, torque, temperature = radial location = thrust = regression rate !" = equivalent velocity Greek symbols = thread half angle ν = Poisson's ratio ε = strain = density = coefficient of friction σ, τ = stress !"#!$%&'(! = burn, burnout , = radial direction = chamber, collar = solid propellant, shoulder = fuel, forward module = total = oxidizer, initial , , = axial direction, yield