IAC-11-D2.4.8 Investigations of Future Expendable Launcher Options Martin Sippel, Etienne Dumont, Ingrid Dietlein [email protected] Tel. +49-421-24420145, Fax. +49-421-24420150 Space Launcher Systems Analysis (SART), DLR, Bremen, Germany The paper summarizes recent system study results on future European expendable launcher options investigated by DLR-SART. In the first part two variants of storable propellant upper segments are presented which could be used as a future evolvement of the small Vega launcher. The lower composite consisting of upgraded P100 and Z40 motors is assumed to be derived from Vega. An advanced small TSTO rocket with a payload capability in the range of 1500 kg in higher energy orbits and up to 3000 kg supported by additional strap-on boosters is further under study. The first stage consists of a high pressure solid motor with a fiber casing while the upper stage is using cryogenic propellants. Synergies with other ongoing European development programs are to be exploited. The so called NGL should serve a broad payload class range from 3 to 8 tons in GTO reference orbit by a flexible arrangement of stages and strap-on boosters. The recent SART work focused on two and three-stage vehicles with cryogenic and solid propellants. The paper presents the promises and constraints of all investigated future launcher configurations. Nomenclature TSTO Two Stage to Orbit VEGA Vettore Europeo di Generazione Avanzata D Drag N VENUS VEGA New Upper Stage Isp (mass) specific Impulse s (N s / kg) cog center of gravity M Mach-number - sep separation T Thrust N W weight N g gravity acceleration m/s2 1 INTRODUCTION m mass kg Two new launchers, Soyuz and Vega, are scheduled to q dynamic pressure Pa enter operation in the coming months at the Kourou v velocity m/s spaceport, increasing the range of missions able to be α angle of attack - launched by Western Europe. Nevertheless, continuous improvement of the launch vehicles is necessary in the γ flight path angle - future which requires starting such investigations already today. Subscripts, Abbreviations DLR’s launcher analysis group SART is focusing its AP Ammonium Perchlorate research on a few promising development lines. Some AVUM Attitude and Vernier Upper Module (of concepts have been studied jointly with industry; other VEGA) investigations are carried-out independently by internal DLR funding. CAD Computer Aided Design ELV Expendable Launch Vehicle A DLR space agency funded study called VENUS is GLOW Gross Lift-Off Mass looking at future upgrades of Vega. This analysis is now GNC Guidance, Navigation, Control focusing on three and four stage configurations based on GTO Geostationary Transfer Orbit solid rocket motors for the lower stages and on different HTPB Hydroxyl Terminated Poly Butadiene storable liquid propellant upper stages. ISS International Space Station Another interesting, simpler concept is currently studied LEO Low Earth Orbit by SART, namely a two-stage to orbit launch vehicle LH2 Liquid Hydrogen (TSTO) making use of synergies by implementing stage LOX Liquid Oxygen or component hardware already existing or under MEOP Maximum Expected Operating Pressure development. This approach should reduce development MMH Monomethyl Hydrazine cost, but even more importantly, promises to raise MR Mixture Ratio production numbers of components and thus decrease MTO Medium Transfer Orbit manufacturing cost and enhance quality. The studied NGL Next/New Generation Launcher TSTO configurations, which aim for a performance range in-between Vega and Ariane 5, are all based on a SI Structural Index (m / m ) dry propellant solid rocket motor for the first stage and a cryogenic SRM Solid Rocket Motor liquid propellant upper stage with VINCI engine SSO Sun Synchronous Orbit currently under development for Ariane 5 ME. TRL Technology Readiness Level Copyright © 2011 by DLR-SART. Published for the 62nd International Astronautical Congress, Cape Town, SA. 1 Under the terms “NGL” and “Ariane 6” a still somehow turned out to be the one with lowest structural weight to nebulous future medium lift launcher configuration is be placed inside a long cylindrical interstage. A sphere investigated in Europe within ESA’s FLPP research of 2.19 m diameter is intersected by a cone containing program and in France by CNES and industrial the N2O4 with the MMH in the remaining sphere- contractors. This launcher with a potential GTO payload section volume. This innovative design allows for a capability range between 2 and 8 tons has also been highly efficient structure because short cylinder independently investigated by DLR-SART and elements with relatively heavy dome connections can be preliminary results are presented here. avoided. However, processes for a cost efficient manufacturing and quality assurance of this design All presented payload performance data consider the de- could become challenging. orbitation of the upper stage after final injection in order to avoid their uncontrolled reentry or the generation of The payload performance of the VENUS II 3-stage new space debris. launcher in a polar orbit could reach about 2200 kg and 3100 kg into an ISS-LEO inclined 51.6 degrees. These Note that all presented launcher concepts are under values are several hundred kilograms above what is to investigation to obtain a better understanding of future be expected for Vega. With its GLOW between 162.4 ELV options. Study results should support Germany’s and 163.2 Mg the payload fraction is in the range 1.35% preparations of the European ministerial council 2012. to 1.9%. For none of the launchers, even the most promising ones, is a development decision currently implicated. Table 1: Characteristic calculated performance data of small launcher upper stage engine options 2 VENUS II AESTUS 2 BERTA The small launcher VEGA with an advanced solid 55 8 propellant first stage, P80, will become operational vacuum thrust kN soon. VEGA consists of three solid rocket motors and a vacuum spec. impulse s 336.4 321.3 small liquid propulsion module for precise orbit chamber pressure bar 60 15 injection called AVUM. Germany is not participating in ENGINE SIZE this launcher development project. total engine length m 2.171 1.194 Already in 2007 DLR and Astrium started looking into a nozzle exit diameter m 1.361 0.65 potential upper stage evolvement and performance nozzle expansion ratio - 280 ca. 110 upgrade of the VEGA launcher in a study called VENUS (references [1] through [4]). A second iteration of VENUS has been initiated in July 2009 which ran through June 2011 and focused on options for storable liquid upper stages in a small launcher. A comprehensive overview on the results of VENUS II is presented in [5]. This study considers in particular a 3-stage and a 4-stage configuration based on solid rocket motors for the lower stages and different storable liquid propellant upper stages. DLR has been involved in the preliminary sizing of the launchers, organization of concurrent engineering design sessions run in DLR’s Concurrent Engineering Facility (CEF) in Bremen, and all performance and trajectory optimization. Astrium, as prime contractor, has been responsible for the pro- pulsion system definition and conceptual design and the upper stages’ mechanical and functional architecture. Both small launcher configurations investigated in VENUS II use the P100 solid motor as the first stage which is a derivative of the P80 of Vega with increased propellant loading. The three stage vehicle (sketch in Figure 1) further consists of a new second stage called Z40 which is a proposed evolution of the Z23 motor of Vega. It is characterized by increased fuel mass of almost 40 tons and a longer combustion time in comparison to Z23. The storable propellant upper stage with the proposed turbopump fed MMH-N2O4 engine AESTUS 2 (Table 1) has been slightly redefined in VENUS II compared to similar launcher arrangements studied in the first loop of VENUS (see [2, 3]!). Various Figure 1: Sketch of VENUS II three-stage launcher fuel tank layouts all with optimal 5400 kg propellant configuration with Aestus II engine in upper stage loading have been explored in preliminary sizing. From a comprehensive trade-off the spherical conical type IAC-11-D2.4.8 2 The VENUS 4-stage configuration shown in Figure 2 3 ADVANCED SMALL TSTO LAUNCHER resembles more the shape and architecture of Vega. The need for a performance upgrade of VEGA and the Three solid motors (P100+Z23+Z9A) are completed by simplification of the overall lay-out combined with a a storable liquid propellant upper stage intended to reduction in the total number of stages has been the replace the current AVUM. Investigations on a suitable major driver in the study of an advanced small engine which does not yet exist in Europe have been expendable TSTO launcher. Six different liquid engine performed with several trade-offs on the thrust level, options with three different propellant combinations chamber pressure, and combustion chamber cooling have been analyzed by SART. One major result concept [5]. The selected pressure-fed engine should published in [1, 2, 3] is the strong interest in a achieve 8 kN of thrust and has been dubbed BERTA combination of a solid first stage and a cryogenic upper (see data in Table 1). stage. This small TSTO has the additional advantage of being very compact and having the shortest length of all A similar upper stage spherical-conical tank architecture investigated versions presented in [1, 4]. as for the 3-stage vehicle has been selected but with 1700 kg MMH/N2O4 propellant instead of 580 kg The preliminary design and more detailed investigation UDMH/N2O4 in AVUM. The calculated structural of such an advanced small TSTO was initiated at DLR index of this L1.7, however, is unfavorably impacted by early in 2010.