Didier Bizzarri

Air-Hydrogen Heat Exchangers for Advanced Space Launchers

This paper deals with air-hydrogen heat exchangers intended to provide in-flight oxygen collection capability to a reusable or semireusable two-stages-to-orbit launcher with an oxygen collection phase in supersonic cruise at Mach 2.5. It aims to present a theoretical but mainly technological and experimental feasibility study of heat exchangers sufficiently efficient and reliable to suit the extreme requirements of this application. Two precoolers of two different types (shell and tubes, and plate and fins) have been selected and designed with the objective of fulfilling all constraints of the concept in terms of performance, leak tightness, reliability, compactness, etc. This design process has been validated with four subscaled breadboards (two of each type) tested on two test benches (for performance and leak tightness), developed by Belgium and Spain, in on-design and off-design conditions. All these results highlight the suitability of the new technologies given the extreme requirements of the concept. An optimum design for each technology is recommended considering its proper advantages and disadvantages. An innovative precooler technology is presented and tested.

Integration of vehicle, propulsion system and separation unit designs for a launcher using in-flight oxygen collection

The use of in-flight Oxygen Collection has shown to significantly improve space launcher performance. The conceptual approach followed by the Royal Military Academy of Brussels (RMA) has tried to widen the available design margins in order to reduce the required technological leap and limit the economical risk associated with such a development. The aim of the ESA-funded theoretical and experimental study on an air separation device is to demonstrate the possibility of performing efficient air distillation in a compact rotating column. An integration of the vehicle, propulsion system and separation unit designs is presented aiming to optimise the overall vehicle performance while keeping technological difficulty and system complexity at a reasonable level. Reference vehicles are presented in their specific mission profiles with an emphasis on TSTO’s. Different layouts of the internal energy and mass flowsheets are compared, in order to make best use of the refrigeration capacity of the hydrogen fuel running though the propulsion system during the first phase of the flight considering the separator as a classical distillation column. This analysis provides the requirements in terms of heat exchange capacity, compression ratios and number of so-called transfer units needed in the separator. Here, the system is intentionally kept simple, to limit complexity, but the analysis is thorough and accurate, including, for example, the effect of the presence of argon. An analysis of the separation unit to reach those requirements is proposed. That includes internals, practical building with estimates of pressure drop, separation performance and flow limitation. Analysis of size reduction of the distillation unit from usual 1-g column to the high-g unit is provided as well as the scale up methodology of laboratory results. First experimental results obtained with our centrifugally enhanced distillation separation system are presented and perspectives for a larger on-board operational unit proposed.

Analysis of Minimal In-Flight Oxygen Collection Cycle for Two Stage Launchers

[Abstract] In the context of an ESA-funded study on an air separation device intended to provide in-flight Oxygen Collection capability to future launchers, experimental and system level investigations are performed. Formerly hosted by the Belgian Royal Military Academy, it is now sustained by the Universite Libre de Bruxelles. Looking at the world wide picture of space launcher studies, oxygen collection is seldom studied by space researchers and engineers. There are few really rational causes to this situation. Aerospace engineers are often reluctant to invest themselves in very different fields, which is strongly required here. Besides, the research projects are often cornered by funding constraints towards very high technology options. This often pushes resulting preliminary studies away from practically and economically viable new applications. To make design trades more accessible over such an heterogeneous set of concepts, simple models are required. The work provided here is the result of simplifying both the cycle, to limit technological constraints while retaining most of the performance, and to provide an approximate modelling while retaining a sensible analysis and sufficiently accurate predictions. The vehicle considered here has been presented in previous articles, but the result has a wider scope. Strong beneficial effects comes from combining the propulsion cycle of the first stage (possibly subsonic) with the separation process, leading to both oxygen collection and even improved propulsion efficiency for the first stage. This approach attempts to draw a reasonable bottom line for the separation plant performance and for the required system complexity. Simplified, but widely accepted, methods are presented for analysing the various aspects of the separation plant performance. Although the model has some drawbacks that can be corrected using a limited set of more accurate predictions, the mass and energy balance can be solved accurately. Options that have a strong impact on performance –mainly expressed by the collection ratioare analysed: use of significant hydrogen pressurisation and use of para-ortho conversion that improves cooling capacity of hydrogen. Although the system is brought to minimal complexity and some hydrogen capacity is wasted for system heat integration simplicity, the retained performance are found well within minimal requirements to sustain operation and are consistent with previous more accurate computations. The analysis therefore allows to assess a viable bottomline for the propulsion system complexity and technological level and to predict performance of oxygen collecting two stage to orbit vehicles with a rather simple analysis.

Experimental study of a heat exchanger for an in-flight oxygen collection launcher

In the scope of an ESA -funded theoretical and experimental study (in the GSTP3 programme) on heat exchangers intended to provide in -flight oxygen collect ion capability to a reusable or a semi -reusable TSTO launcher with an oxygen collection phase in supersonic cruise, two subscale models of an air -hydrogen precooler and a test set -up are currently being developed in Belgium and in Spain. The vehicle we for esee for this application is described in previous conference papers as well as the work on our ESA -funded airborne air separator, which is the other critical element of the oxygen collection plant. This current paper is concentrating only on the theoretic al but mainly the technological and experimental aspects of such an air precooler. The experimental and technical aspects include choices and main trade -offs that have had to be made during the design process by the different partners (Techspace Aero, von Karman Institute, Iberespacio, University of Liege, Royal Military Academy of Belgium and University of Brussels). After we fixed the requirements at system level and at the precooler level, a simulation work of generic heat exchangers is presented includi ng the problem of frost formation and its influence on the heat exchanger performance. A few advanced heat exchanger designs are analysed resulting in a more detailed parametric and performance analysis of two advanced configurations. A detailed study of the most advantageous heat exchangers materials is shown resulting in the selection of the alloys for the two breadboards. The manufacturing processes for these two breadboards are defined, based on trials on small scale models inspired from the two techno logy candidates. Perspectives are also given for the mechanical and thermodynamic testing of the two breadboards.

Experimental study of air-hydrogen heat exchangers

This paper has been prepared in the frame of an ESA-funded theoretical and experimental study in the GSTP3 programme on heat exchangers intended to provide in-flight oxygen collection capability to a reusable or a semireusable TSTO launcher with an oxygen collection phase in supersonic cruise at Mach 2.5. The study could also be applicable to a subsonic air-launch case as the ones studied in the EC FP6 SSA study called FLACON. Four subscale models (breadboards) of an air-hydrogen precooler as well as a performance test set-up and a leak test set-up have been developed by Belgium and Spain. This paper is concentrating on the theoretical but mainly the technological and experimental aspects of such an air-hydrogen precooler and its four related breadboards. The paper will present: - the precooler requirements - the selection of the heat exchanger (precooler) types and their materials - the design of two full size air-hydrogen precoolers (of two different types) - the design of four breadboards (two of each type) - the manufacturing of the four breadboards - the design and construction of the test set-up for performance and leak checks - the experimental results obtained with the four breadboards. The potential problem of frost formation and its influence on heat exchanger performance will also be investigated.

Compact Air Separation Technology For In-Flight Oxygen Collection

In-flight Oxygen Collection has already been described in previous publications, mainly as a conceptual approach [2-6]. The improvement potentials have been studied and possible uses of the technology go beyond the concept presented here. That is in the aerospace field and also outside, in a much wider range of applications. Hardware work on compact separation are seldom described [7-8]. As the setup was nearing completion, design know how improved. The last problems were solved and the setup was made fully operational and subject to testing.