1.1 Project Objectives
The ‘Future High-Altitude High-Speed Transport 20XX’ (FAST20XX) project aims at providing a sound technological foundation for the industrial introduction of suborbital transportation in the medium term (5-10 years) and in the longer term (second part of this century), defining the most critical RTD associated building blocks to achieve this goal. Note that it is not the development of vehicles which is planned but the mastering of technologies required for such development should the decision be made in Europe. In addition, the corresponding required critical non-technical building blocks are identified. The identified critical technologies have been investigated in depth by developing and/or applying dedicated analytical, numerical and experimental tools, while the legal/regulatory issues have been discussed with government or international authorities as necessary. The underlying philosophy is to use realistic as well as futuristic concepts as guide lines for technology developments and for initiating answers to non-technical issues. The project objectives can be broken down as follows:
- The definition of three novel concepts for high-altitude high-speed transportation which satisfy the desire of humans to leave the atmosphere and view the earth from space and/or provide reference concepts for transatmospheric, point-to-point transportation . The first concept, ALPHA, is air launched from a carrier plane to reach the confines of the atmosphere by means of a hybrid rocket engine and then glides back to earth unpowered for a conventional runway landing. The 2nd and third concepts, both rocket-propelled (SpaceLiner and EVE), intend to transport about 50 people across long distances in extremely short time as well. The fully reusable two-stage Spaceliner would start vertically and land horizontally, while the EVE take-of would be assisted by a magnetically-levitated sled. Particular attention will be given to how such concepts can be put into operational use, and their respective benefits and environmental impact have been assessed.
- The identification of the prerequisites for the commercial operation of high-altitude high-speed transport. It will be quite important for future developments to tackle legal issues, and to reduce the necessary certification efforts common to commercial transport in a meaningful way. Liability and insurance issues have been considered as well. Medical research has to be revisited and the requirements with respect to acceleration loads a normal passenger have been reassessed. Last but not least an abort capability is required, satisfying the highest safety requirements.
- The identification of critical technologies. Any development efforts will be dominated by safety aspects, hence achieving robust designs yielding high reliability. A major issue will be among others the process of separation of the particular transportation vehicle and the launching carrier as well as the booster, the choice of trajectories which are comfortable for the normal passenger, the stability of the flight during all phases, efficient and safe hybrid propulsion and advanced light-weight structures. Operational re-usability is a major driver for cost-efficiency, and commercial attractiveness. Particular attention has to be paid to the effect on environment which concerns the reduction of noise and of emissions. While special heat protection is not required for vertical ballistic suborbital flight, the combination of high-speed and long-range capability leads to heat loads at several location of the vehicle including leading edges and stagnation point which will require novel structural concepts in connection with classical or composite materials.
It must be emphasized that a number of significant technological advancements have been achieved during FAST20XX, notwithstanding their exploratory (and thus uncertain) nature. FAST20XX, coordinated by ESA-ESTEC, has been supported by the EU within the 7th Framework Programme Theme7 Transport, Contract no.: ACP8-GA-2009-233816. Further info on FAST20XX can be found on http://www.esa.int/fast20xx, which includes also the participants and the respective contact details.
1.2 Progress and Achievements
2 Technologies for Low-Energy Suborbital Transportation
In WP 2.1.2, the reference ALPHA vehicle was modelled and optimised in several iterative design steps by consolidating all modelling and experimental results from the other WP2 and some ALPHA related WP4 work packages. In WP 2.1.3, the VDK-ULB code was developed together with a trajectory code. Coupled to the CENAERO MINAMO optimizer, it was possible to identify optimised values for the key parameters of the method as well as the engine dimensioning. Moreover, MINAMO has permitted to identify the degree of influence of each parameter on the global vehicle performance. In WP 2.2.1, two different wind tunnel models were designed and manufactured. Both, static six-component force measurements with emphasis on lateral motion in the low supersonic and transonic flow regimes and measurements of the Pitch damping derivatives in supersonic flow have been performed in the Trisonic Windtunnel Koeln (TMK). An experimental database has been created. In WP 2.2.2, the Chimera method as well as the 6 degrees-of-freedom modeler implemented within the NSMB (Navier Stokes Multi Block) flow solver, available at CFSE, were applied to simulate the separation process of the ALPHA vehicle from its carrier aircraft and its trajectory during a few seconds after the release. Five separation trajectories were computed using different configurations or different initial conditions. In WP 2.2.3, numerical simulations of the reference under-wing separation scenario using a flight mechanics and CFD codes coupling have been performed. The cross-checking of the ALPHA CoG trajectories obtained with NSMB code (CFSE) and elsA code (ONERA) were very satisfactory and let presume a good level of safety for such a kind of release. On the opposite, a piggy-back separation seems to be much more complex to carry out. In WP 2.2.4, the CAD-file of HOPPER and the aerodynamic data of HOPPER and ALPHA respectively were revised, consolidated and provided together with a description of the aerodynamic data base. In WP 2.3.1, a GNC architecture has been identified and assessed for the ALPHA mission, showing no issues in terms of controllability. ALPHA aerodynamics have been evaluated by CFD calculations for verification of the AEDB and to support load sizing cases. In WP 2.3.2, the performance of the ALPHA vehicle was computed including its reference trajectory, flight loads and related sensitivity information. In WP 2.3.3 nonlinear control laws for ALPHA manual flight were designed. In WP 2.4.1, the definition and preliminary CAD-based design of an innovative, safe and “green” hybrid rocket motor configuration for the ALPHA vehicle was performed, considering all performance and accommodation constraints. The motor design work was closely accompanied by an analytical structural and strength analysis of the ALPHA hybrid motor and an FEM-based modelling of selected motor subsystems. In WP 2.4.2, two reusable scaled hybrid test motors with the designation AI-X1000 and AI-X6000 were designed, manufactured and integrated in order to demonstrate the main ALPHA hybrid propulsion technologies at reduced scale. In WP2.4.3, work on the paraffin/nitrous oxide hybrid rocket engine was continued. Two new engines were manufactured in order to study various aspects of the combustion. The first one was used to study paraffin grain length ranging from 5 to 19 cm. As it was demonstrated that the 5 cm grain length gives the best combustion, a new engine designed specifically for this length was manufactured. The reduction of the grain length for the injection line showed higher regression rate and better specific impulse. Moreover ULB has developed regression rate sensors that allowed the measurement of the regression rate in quasi real time. A pressurised injection line was also designed and developed. In WP 2.5.1, the 1st and the 2nd iteration loop of airframe modelling and airframe optimisation have been performed. A detailed CAD model of the ALPHA vehicle has been generated under consideration of different manufacturing aspects of composite materials. Non-linear FEM based structure analysis and several optimisation loops have been performed to find a lightweight airframe. In WP 2.5.2, the definition, specification and design of all required ALPHA subsystems have been performed. A statistical approach and in-house research have been accomplished. Moreover, data of COTS parts and known parts successfully integrated into the PHOENIX landing demonstrator have been applied to improve the subsystem design. Subsequently, an enhanced mass breakdown of the subsystem has been generated and the optimal location of the components has been investigated.
3 Technologies for High-Energy Suborbital Transportation
The SpaceLiner is the reference concept of the WP3 “Technologies for High-Energy Suborbital Transportation”, and most of the activities performed during the project have supported the subsystems definition and consolidation of this high performance intercontinental passenger transport.
As an overall summary of WP3 activities, the main progress and achievements can be considered both from the system side and from the technology side.
In particular, the SpaceLiner System has matured and evolved along the three-year FAST20XX project, from the initial SL2 concept (Phase 0 study level) through the SL4 at project mid-term to the last SL7-1 version reaching a Phase A development level. This statement is valid both from the system and subsystem points of view.
A number of topics have been addressed at system level, such as:
- configuration trade-off
- preliminary design of the mission
- trajectory optimisation
- cabin layout and passenger comfort
- off-nominal flight and abort scenarios
- passenger rescue system
- rocket engines, tanks and propellant feed system
- TPS and leading-edge active cooling
- landing gear
- flight control
- costs for development and operation
- results of WP4 on environmental impact, business, medical, and safety aspects have been included in the system level investigations
The general feasibility of the SpaceLiner as a high speed passenger transport has been demonstrated, thanks to the several activities developed in the FAST20XX project.
From the technology side, the following conclusions can be drawn out.
Active Cooling, Flow Control: the effectiveness of the advanced active transpiration cooling system, use of porous material to control boundary layer laminar-to-turbulence transition, control of passive/active oxidation transition of ceramic reusable TPS, have been proven by means of experiments and simulations.
Advanced Structures: Orbiter structure has been designed, analyzed and optimized, materials have been preliminarily identified, structural analysis of the rescue capsule has been performed for three critical load cases, a conservative window design has been proposed as a base benchmark.
Low-Density Effects in Suborbital Flight: theoretical and experimental tools have been proven to be reliable in the prediction of rarefied aerodynamics and aerothermodynamics relevant for high altitude suborbital flights.
Flight Dynamics and Safety: SL4 was used for preliminary checking of Flying Qualities, lessons learned have been applied to the evolved SL7.1 concept showing improved Flying Qualities; entry GN&C architecture has been proposed, suitable algorithm has been proposed and tested, trajectory modifications have been implemented for SL7 to ensure margins for trajectory control.
From the project management point of view, all the fourteen WP3 subtasks have been concluded within the official end of the project. Concerning technical deliverables, a big reporting effort made by some partners in the weeks just after the Final Presentation at DLR Bremen has allowed to complete the project with the delivery of the entire set of reports within January 2013. All the WP3 milestones have been achieved as expected. The use of person-months for WP3 has been in-line with that foreseen in the Annex I “Description of Work” of FAST20XX Proposal.
It must absolutely be highlighted the strict and fruitful cooperation that has been established among the WP3 partners, who have shown their own high-level skill, professionalism and strong commitment to the project. This is also another good result of the FAST20XX project.
As a final remark, much work is still to be done to make the system and the technologies studied during FAST20XX fully mature and applicable to the industrial development, design, construction and full operability of a future suborbital transport system. Moreover, regarding SpaceLiner related activities, the necessity of an extension through a new co-funded (EC ?) project has emerged clearly from the outputs of FAST20XX. This will also allow not to waste the fruits of these three years of intensive work.
4 Prerequisites for Operational Suborbital Flight
In the second project period activities covering ground and flight operational aspects, legal/regulatory, environmental, medical, business as well as GNC aspects have been carried out and finalized.
An operational scenario has been sketched for the Alpha vehicle, including a schematic layout of the spaceport ground facilities, assessment of a mission, definition of flow charts and models for the crew personnel and vehicle fleet. Furthermore the pre-launch, launch and post-launch operational processes have been defined including an estimation of the required number of employees.
Legal work has been addressing liability and insurance aspects both for a scenario under the aviation law regulation as well as a scenario assuming regulation under international space law. The main problem for future insurers of suborbital flights is the difficulty to assess the risks. Furthermore two work packages on the future authorization have been finalized. In the first, which more generally addresses the approach and roadmap, a survey as been conducted, the “FAST20XX Questionnaire on Human Suborbital Flight”, followed by a workshop, which was hosted by the European Commission in Brussels on 2012-10-11. Some of the major discussion topics have been an initial light-touch regime followed by a step-by-step “learn-as-you-go” approach to avoid over-regulation, the potential regulation on national versus European level as well as an internationally harmonized regulatory framework to avoid penalizing or emigration. A second work package looked more specifically into the potential benefits and drawbacks of a certification versus a licensing approach, comparing the current licensing framework of the Federal Aviation Agency FAA in the USA with the certification option proposed in Europe, in particular by the European Aviation Safety Agency EASA under the light of the proposed vehicle concepts in Europe (e.g. winged versus un-winged vehicles, ground- versus air-launched, etc.).
Noise emissions, in particular the sonic boom carpet as well as the atmospheric impact of emissions such as water vapour and NOx have been assessed and studied. Noise during launch and ascent, the strength of the sonic boom generated during re-entry as well as of the sonic boom generated by the Spaceliner during the flight in the outer fringes of the atmosphere have been assessed and analysed.
Medical topics in period 2 covered G-induced issues, medical screening as well as critical incidence issues and first aid. Various options such as authoritarian screening similar to astronaut selection versus independent passenger health consulting and coaching based approaches have been discussed. The type of probability of medical risk factors as well as possibilities to carry out first aid measured during a suborbital flight have been assessed.
Business cases and scenarios have been defined from currently available studies and simulations have been carried out in order to identify the sensitivities with respect to technical vehicle aspects such as development and production cost (complexity), vehicle fleet size, component lifetimes, propellant cost, maintenance cost, required flight- and ground crew, etc. for different scenarios of passenger demand and ticket prices with the objective to assess profitability and return on investment.
Last, the design and assessment of an advanced automatic guidance, navigation and control (GNC) concepts based on robust control techniques and autonomous flight technologies has been assessed for the ALPHA and Spaceliner vehicle. This included health monitoring algorithms for the GNC such as to identify sensor malfunction during flight and assure fault-tolerance and safety.