EURASTROS ascent trajectory and abort analysis

The EURASTROS study [1] was a joint study between Ariane Group GmbH and the German Aerospace Center (DLR), exploring astronautic transport capabilities of Ariane 6. The study included the preliminary design of a crew module (CM) [2], a service module (SM) [3], a performance analysis of possible Launch Abort System (LAS) concepts and a cost analysis [4]. This paper presents the work performed with the purpose to define the general ascent strategy and to design suitable end-to-end abort strategies compatible with the mission and system requirements. It shows the selected reference ascent trajectory and covers detailed preliminary analyses of the exo- and endo-atmospheric abort scenarios regarded within the EURASTROS project. All analyses were closely tied to continuous optimization of the Ariane 6 ascent trajectory and corresponding iteration of achievable payload performances, using astronautic transport to an ISS orbit as reference study case. The conducted analyses explored multiple possibilities for performance adjustment in agreement with human rated mission requirements, while also respecting space debris mitigation standards. Eventually these investigations concluded in the proposal of 11 Mg propellant un-loading of the Upper Liquid Propulsion Module (ULPM) of the Ariane 64 (A64) with respect to standard GTO upper stage fuel, yielding a trajectory enabling for maximum performance and also sufficient safety. The crew module, envisioned for a total crew of up to three astronauts, was designed with close resemblance to the Apollo CM, with a Service Module (SM) for exo-atmospheric flight at the rear and a Launch Abort System (LAS) for endo-atmospheric abort at the front, but with volume reduced by 28 %. For the LAS design, the most promising configurations were designed towards minimum thrust allowing to reach a minimum safety distance of 200 m to the launch vehicle within 3.5 seconds after separation and to fulfill further safety requirements in case of an abort from launch pad. Simulations conducted at DLR concluded that the bare minimum thrust should exceed 950 kN for both concepts in order to meet imposed safety requirements. Based on these results a subsequent mass budget estimation yielded a total mass estimate between 4700 – 5400 kg for the LAS. The SM is based on the ASTRIS kick stage and utilizes the engine BERTA running on storable fuel. This module is dimensioned to provide continuous exo-atmospheric launch abort capabilities while preventing any potential impact on populated areas on European and Eurasian soil. For such an abort scenario, the Last Direct Re-entry Point (LDR) after which an abort-to-orbit would be executed, has been defined. Influences of the corresponding maneuver pitching angles on ballistic downrange as well as on required time for abort-to-orbit are explored and the SM minimum thrust was adjusted to yield sufficient performance capabilities. Eventually, six abort modes for exo-atmospheric flight are proposed and discussed

Assessment of VTVL and VTHL Reusable First Stages

Two-stage vertical take-off vertical landing (VTVL) and vertical take-off horizontal landing (VTHL) partially reusable launcher configurations are systematically analyzed. The investigated configurations consider a reusable first stage that either performs a landing at the launch site (return to launch site RTLS) or a landing downrange of the launch site (downrange landing DRL). The considered propellant combinations include LOX/LH2, LOX/LCH4 and LOX/RP-1. Configurations based on staged combustion and gas generator cycle engines are analyzed. The same engines however with different expansion ratios are used on the reusable first stages and the expendable upper stages. Special emphasis is put on analyzing the different configurations under similar design assumptions that allow a comparison of gross lift-off masses, stage lift-off masses, stage structural indices as well as loads encountered by the reusable stages during atmospheric reentry. Based on this comparison benefits and drawbacks of the investigated RLV configurations are discussed

Family of Launchers Approach vs. “Big-Size-Fits-All”

One option for future space transportation concepts could be a family of launchers supporting a wide range of payload performance. The idea bases upon using “building blocks” of common stages or main propulsion rocket engines and applying them in a modular way. A somehow contrarious option is a single TSTO launch vehicle serving all kinds of missions, even those which have payload mass requirements much below the design capacity. The technical investigations described in this paper evaluate the two antipodal design approaches of either establishing a launcher family consisting of modular building blocks or choosing a full-size launcher which serves all missions with minimal adaptations of the upper- and kick-stage selection. The paper summarizes major results of the preliminary technical design process. The overall shape and aerodynamic configuration, the propulsion and feed system, the architecture of the stages are described and different technical solutions are compared. Payload performance is optimized for the different concepts in the GTO-mission, manned flight to ISS and to SSO. The winged configurations’ controllability in hypersonic reentry and subsequent subsonic flight is assessed. The study is completed by a relative comparison of to be expected RC/NRC of the different launcher concepts

Advanced Re-Entry Systems Based on Inflatable Heat Shields in the EFESTO Project: Preliminary IOD Mission and System Definition

The European Union H2020 project EFESTO is coordinated by DEIMOS Space with the goals of improving the TRL of Inflatable Heat Shields for re entry vehicles in Europe from 3 to 4/5 and paving the way to an In Orbit Demonstration (IOD) that could further raise the TRL to 6. This paper provides a synthesis of the EFESTO design and experimental achievements and sums up the inflatable heatshield IOD mission and system design. This is the final step of the EFESTO project. First, the initial IOD design resulted from a dedicated Concurrent Engineering Facility (CEF) session is introduced. The session core consisted of trading-off the system configuration options derived from the sequential design and testing campaigns, including the inflatable structure and F-TPS key subsystems. Additional aspects, such as launcher and landing site selection, were considered. The driving rationale is the maximization of the scientific return of the experiment while also taking into account feasibility considerations related to the current European space sector capabilities and market opportunities. The subsequent design phase focused on harmonizing the CEF mission and system definition and extending it with a preliminary assessment of the IOD system realization and mission implementation. This final output represents a unique contribution of the EFESTO project to the European know-how in inflatable heatshield technology and promotes the relevance of the EFESTO consortium in the frame of a European re-entry technology roadmap

Outlook on the New Generation of European Reusable Launchers

The technical investigations described in this paper evaluate the two seemingly antipodal design approaches of either establishing a launcher family consisting of modular building blocks or choosing a full-size reusable launcher stage which serves all missions with adaptations limited to the upper- and kick-stage selection. The paper summarizes major results of the preliminary technical design process iteratively performed at DLR-SART. The overall shape and aerodynamic configuration, the propulsion, the architectures of the stages are described and different technical solutions are compared. Payload performance is optimized for the different concepts in the GTO-mission, manned flight to ISS and to SSO. The winged configurations’ controllability in hypersonic reentry and subsequent subsonic flight is assessed

The EFESTO Project: Advanced European Re-Entry System based on Inflatable Heat Shield

EFESTO is a project funded by the European Union H2020 program aiming for a revamp and growth of European know-how and systems engineering capabilities in the strategic field of Inflatable Heat Shield technology for re-entry vehicles. This project analyzes the use of Inflatable Heat Shields for Mars exploration and Earth re-entry applications that served as representative study-cases. In addition to design activities at system and sub-system levels, the EFESTO team focused on testing the aerothermodynamic properties of the Flexible TPS and the mechanical characteristics of the shield, the latter exploiting a manufactured high-fidelity Inflatable Structure demonstrator. The data gathered from the two test campaigns additionally served for experimental-numerical rebuilding and cross-correlation. Finally, a phase-0 feasibility study defined a preliminary IOD mission design to enable in-flight verification and validation of the critical technologies. This paper will present the whole excursus of the project, including the key phases of use-cases survey and investigation, mission scenarios definition and analysis, system engineering and sub-system design, technology development and ground demonstration, future roadmap identification with reference IOD feasibility analysis and early definition. The project achievements have improved the European TRL of Inflatable Heat Shields from 3 to 4/5, thus paving the way towards further developments in the mid-term future. This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 821801

EFESTO - advancing European hypersonic inflatable heatshield technology for Earth recovery and Mars high-mass delivery missions

The European Union H2020 EFESTO project is coordinated by DEIMOS Space with the end goals of improving the European TRL of Inflatable Heat Shields for re-entry vehicles (from 3 to 4/5) and paving the way towards further improvements (TRL 6 with a future In-Orbit Demonstrator). This paper presents the project objectives and provides with a general overview of the activities ongoing and planned for the next two years, promoting its position in the frame of a European re-entry technology roadmap. EFESTO aims at (1) the definition of critical space mission scenarios (Earth and Mars applications) enabled by the use of advanced inflatable Thermal Protection Systems (TPS), (2) characterization of the operative environment and (3) validation by tests of both the flexible materials needed for the thermal protection (flexible thermal blanket will be tested in arcjet facility in both Earth and Martian environments) and the inflatable structure at 1:2 scale (exploring the morphing dynamics and materials response from packed to fully inflated configuration). These results will be injected into the consolidated design of a future In-Orbit Demonstrator (IOD) mission

Multidisciplinary Design Analysis of Reusable European VTHL and VTVL Booster Stages

While initially met with skepticism, launch vehicles with reusable stages are now an established and successful part of the global launch market. Thus, there is a need to analyze and assess the possibility of such a system being designed and built in Europe. Accordingly, in 2016 the German Aerospace Center (DLR) initiated a study on reusable first stages named ENTRAIN (European Next Reusable Ariane). Within this study two return method categories, respectively vertical take-off, vertical landing (VTVL) and vertical take-off, horizontal landing (VTHL) with winged stages, were investigated. First, preliminary design tools were used to identify promising configurations and in the second phase more specialized and extensive analyses were conducted for subsystems of special interest. From this second phase, the results of the evaluation of two areas are presented: Structure as well as system dynamics, guidance and control. The results of these analyses together with previously published results from other subsystems increase the confidence in the designs proposed and evaluated within the ENTRAIN study as well as in the general understanding of the technical factors driving the design of reusable stages

Development of Inflatable Heat Shield Technology for Re-Entry Systems in EFESTO project

The EFESTO project is funded by the European Union H2020 program. The purpose is to increase European capabilities in designing Inflatable Heat Shields for re-entry vehicles. The technology of inflatable heat shields enables increasing the spectrum of space-based applications as it provides effective heat protection and deceleration capabilities for atmospheric descent while being comparatively mass and volume efficient which is a significant asset for a space mission. The use of inflatable heat shields for Mars exploration and for Earth re-entry of a launcher upper-stage for later reuse were selected at the initial study phase as potential application for the HIAD technology. These two application cases are to demonstrate the performance of this technology under realistic conditions and to provide a representative study frame for the design of inflatable heat shields trained at tangible applications

Development of Inflatable Heat Shield Technology for Re-Entry Systems in EFESTO project

The EFESTO project is funded by the European Union H2020 program. The purpose is to increase European capabilities in designing Inflatable Heat Shields for re-entry vehicles. The technology of inflatable heat shields enables increasing the spectrum of space-based applications as it provides effective heat protection and deceleration capabilities for atmospheric descent while being comparatively mass and volume efficient which is a significant asset for a space mission. The use of inflatable heat shields for Mars exploration and for Earth re-entry of a launcher upper-stage for later reuse were selected at the initial study phase as potential application for the HIAD technology. These two application cases are to demonstrate the performance of this technology under realistic conditions and to provide a representative study frame for the design of inflatable heat shields trained at tangible applications