the future of european launchers: the esa perspective

r bulletin 104 — november 2000

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The Future of European Launchers: The ESA Perspective

M. CaporicciHead of Future Programmes and Technology Office, Directorate of Launchers, ESA, Paris

IntroductionAfter an initial pioneering period in the sixties,the applications of space in the strategic andthe commercial arenas, mainly in the fields oftelecommunications and Earth observation,began to emerge. It therefore made sense forEurope to equip itself with independent meansto guarantee its access to space. Developmentof the Ariane launcher was undertaken, whichbecame a striking commercial success that far exceeded even the most optimisticforecasts. One of the main reasons for thissuccess was the immediate focus oncommercial activities.

The increased competition and the newlyarising markets are forcing industry towardsoptimised products and reduced launch prices.The greater availability of launchers is allowingthe satellite manufacturers to choose and todrive launcher evolution, rather than having toadapt their designs to a few available launchvehicles.

All of these factors have totally changed theenvironment in which Europe had initiated thedevelopment of its own launch vehicle. Onetherefore has to examine the steps that nowhave to be taken to preserve the initialobjectives of independent access to space andcommercial success in the new worldwidescenario, in coherence with today’s Europeanstrategic, economic and political interests.

European objectivesModern society relies heavily on telecom-munications and the associated services. This reliance has been further accentuated bythe rapid emergence of information technology.It is essential not only for strategic andeconomic reasons, but also for political andcultural reasons, that Europe retains anindependent satellite manufacturing andoperating capability.

Inability to autonomously launch satellitesmanufactured in Europe would soon lead to theinability to preserve the satellite and spacemanufacturing industry, as well as restrictingaccess to downstream application markets inthe face of fully developed and organised UScompetition. US industry, reshaped byconsolidation, is able to produce satellites andlaunchers within the same company, oftenproviding the customer with a turn-key service.Europe has a growing ambition to play anactive role in peacekeeping actions anddisaster prevention and mitigation; this alsorequires a well-developed European spaceinfrastructure for Earth observation andtelecommunications, available without delayand without third-party dependency.

Given that the launch-services market is undergoing a radicalrestructuring, Europe has to be able to offer a more complete packageof services in order to maintain a sufficient level of industrial activityand reduce production costs. Therefore, for Europe to retain andimprove the competitiveness of its launchers on the world stage andto satisfy evolving market demands, an optimised range of launchvehicles is needed. This immediately leads to two distinct objectives,which are: to maintain European launcher competitiveness in theshort and medium term (up to 2010), and to prepare the necessarysteps for the timely development of the new systems that will berequired for longer term competition (2010 - 2020).

With the transformation of the Soviet Union andthe changing political scenario, a totally newenvironment has emerged in the 1990s. As theSpace Station has become an internationalcooperative effort, the launchers developed formilitary purposes in the countries that werepreviously part of the Soviet Union haveprogressively become available to the Westernmarket for use as commercial launchers,together with a large amount of relatedtechnology. At the same time, the consolidationof the US aerospace industry has created hugecorporations with strong interests in the spacelauncher field The satellite communicationsmarket has also evolved, with the burgeoningnumber of satellites required to provide the newservices and the introduction of the LEO andMEO constellation concepts to serve the entireglobe.

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An Ariane-5 launch

the future of european launchers

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Preserving an independent capability foraccess to space is and remains therefore anessential goal for Europe. Considering therelatively limited governmental budgetsavailable, it would appear that the objective ofindependence and unrestricted access mayonly be achievable if Europe is capable ofmaintaining full competitiveness on the worldmarket. Independence must also bemaintained under the condition of affordabilitywithin the European system, includinggovernments, industry and the launch serviceoperator, Arianespace.

Expendable-launcher activitiesLaunch-service providers currently competingworldwide have historically benefited from theirrespective governments’ development oflaunch vehicles and the associated groundinfrastructure. Such vehicles, developed forstrategic reasons, have progressively becomeavailable for commercial exploitation, withoutrequiring amortisation of the developmentcosts. Governments also developed the launchbases and their infrastructure as part of theeffort required to enter the elite of States withindependent access to space.

In the last years, strong emphasis has beenplaced, in particular in the USA, on a drasticreduction in the cost of access to space. Thesharing of work within the USA is regulated bythe Presidential policy, which attributes to theDepartment of Defense the task of developinga new cost-effective generation of expendablelaunchers, through the Evolved ExpendableLaunch Vehicle (EELV) programme, and toNASA the task of identifying, evaluating anddemonstrating the technologies required for anew generation of Reusable Launch Vehicles(RLVs).

The EELV’s objective is to achieve reductions inthe cost of expendable launchers of the orderof 25%, by making use of conventionaltechnologies coupled with improved andsimplified manufacturing processes, vehicledesigns optimised for cost, and streamlinedintegration and launch operations. Theprogramme is also designed to reaffirm thesupremacy of the United States in the worldlaunch-service market. The programme relieson government funding, complemented withinvestments by the two large US aerospacecorporations, Boeing and Lockheed Martin.

The EELV programme will generate twomodern families of launch vehicles, Delta-4 andAtlas-V, which in synergy with the existingsmaller Delta-2, Athena, Taurus and Pegasusvehicles, will allow the USA to cover the entirerange of launch services, from small to very

heavy payloads, commercial and governmentalmissions, into LEO or towards interplanetaryjourneys. As part of the programme, theexisting ground infrastructure will also bemodernised and improved processing methodswill be adopted.

Ariane-5 improvementsTo keep up with the above developments in thesatellite market and with the growing launch-vehicle competition, ESA has proposed toEuropean governments several improvementsto the existing Ariane-5 launcher, which havebeen approved and are already beingimplemented. They will provide greater missionversatility, will increase the launcher’sperformance, and will also streamlineproduction and operations, thereby reducingthe specific launch cost. These improvementswill be delivered by the Ariane-5 EvolutionProgramme, focussed on improvement of thelauncher lower composite by the adoption ofthe larger thrust Vulcain-2 engine, and theAriane-5 Plus Programme, focussed onimproving the upper stages by adding a restartcapability and the introduction of cryogenicpropellants. A new upper stage cryogenicengine, Vinci, is also being developed.

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The Vulcain-2 motor undertest at Lampoldshausen (D)


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satellite constellations. The initial narrow-bandconstellations (i.e. Orbcomm) were composedof satellites weighing just a few hundredkilograms and used small launchers for orbitinjection. The wide-band systems, such asIridium and Globalstar, rely on satellites withmasses of several hundred kilograms, whichhave been launched on medium-sizedlaunchers, such as the Long March, Delta-2and Soyuz. The next generation of broad-bandsystems (Skybridge, Teledesic, etc.) will rely onsatellites weighing 1.5 – 2 tons, placed intohigher orbits, and will require launch capabilitiesof 4 – 6 tons to LEO.

So it is expected that if, following the finalcommercial outcome of the first generation, asecond generation of constellations is realised,a medium-lift launch vehicle with suchcapabilities to LEO will be ideally placed toserve such a market. This type of vehicle is alsoideally sized for governmental missions in polarEarth orbit, as are required for civil and militaryEarth observation (Spot, Helios) ormeteorology (Metop). The number of thesemissions is insufficient to justify by itself thedevelopment of a dedicated vehicle, but theuse of a heavy launcher such as Ariane-5 maywell involve unacceptable cost or scheduleconstraints.

Europe has two choices in the face of thegrowing demand for diversified launch services: – to strengthen the European launcher industry

by developing a coherent family of Europeanlaunch vehicles, or

With such improvements Ariane-5 willprogressively acquire the capabilities requiredfor dual launches into GTO of the latest andheaviest telecommunications satellites, and forthe deployment in Low Earth Orbit (LEO) ofsatellite constellations.

In parallel, Arianespace is working withEuropean industry to reduce manufacturingand operating costs. The streamlining of theindustrial organisation, through the consolidationof European industry, is also expected to leadto cost reductions and more effectivemanagement.

The strategic goal is to serve as much aspossible of the commercial GTO satellitemarket with multiple launches, so as to reducethe vehicle specific cost and maintain asufficiently high production level, even in amarket that, in terms of number of launches,has not grown as much as was expected a fewyears ago.

Complementary launchersWhile these improvements will allow Ariane-5 tocope with the heaviest payloads in aneconomically effective manner, completion ofthe range of launch services offered by Europeis still a necessity, in particular through theaddition of small and medium-size launcherscomplementing Ariane-5 for the lighter classesof payload and for Low Earth Orbit.

The diversification of the satellite market has ledto a demand for launch services outside thetraditional GEO orbit. Based on the history oflaunches conducted over the last few years,there is a clear concentration of payloads withmasses of between 500 and 1500 kg beinglaunched into LEO, corresponding essentiallyto governmental scientific and Earth-observation missions. Such missions, mainlysponsored by the space agencies, are aimed atthe demonstration of technologies or theinvestigation of specific scientific phenomenawith limited investments. While most of thesemissions demand dedicated launches intoparticular orbits, limitations on overall missioncost require the use of low-cost launchvehicles. Estimates made by ESA, Arianespaceand industry foresee 30 – 35 missions over thenext ten years from European governmentalagencies in this payload class. Some of thesemissions will be the result of cooperativeprogrammes and will probably fly on non-European vehicles, but more payloads will beidentified from those countries that cannot relyon an independent capability for access to space.

Also considerable demand for launch servicesinto LEO has come from the first generation of

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Artist’s impression of a Vegalaunch


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– to procure launch vehicles available on themarket at the lowest possible cost tocomplement Ariane-5 in the lighter payloadclasses.

In the short term, the second option can beeasily implemented by making use of thelaunch vehicles from the former Soviet Union orother non-market-economy countries, throughthe creation of joint ventures or directprocurement from foreign entities. While thisoption may be satisfactory for the customerand for the launch operator, it brings neithereconomic nor technical advantages to theEuropean launcher industry.

In the 1990’s the European launcher industryenjoyed a favourable situation, with fullproduction of the Ariane-4 vehicle for thecommercial market in the presence of relativelyweak and disorganised competition and, at thesame time, was engaged in the large,government-sponsored, Ariane-5 developmentprogramme. The termination of Ariane-4production is leading to the shutting down ofseveral production lines all over Europe, at atime when the main Ariane-5 developmenteffort is also being completed. The workforeseen for the Ariane-5 improvementsconcerns only selected areas and industry willhave to rely primarily on production work andhence commercial success in the marketplace.

Based on market trends, 25-30 commercialGEO satellites per year are currently foreseen inthe next decade, which means that Ariane-5 maybe limited to a maximum of 6 to 7 commerciallaunches per year. This in turn may lead tounder-use of the production facilities andimportant reductions in the industrial workforce.

To preserve Europe’s independent access tospace at an affordable cost, the commercialsuccess of Ariane-5 is a pre-requisite. A keyfactor in this respect is the launch rate and theassociated increase in production with theconsequent economies of scale. Ideally for theEuropean launcher industry, therefore, anyrequirement for launch services in addition toAriane-5 should be based on the samecomponents, use the same production facilitiesand launch infrastructure in Europe and FrenchGuiana, and involve the same operationalteams, in order to get maximum synergy.

As far as industrial or risk-capital investments innew launcher developments are concerned,they need to be pursued for all those activitiesthat involve limited risk and offer a return oninvestment in a time interval acceptable for thefinancial markets. This is the case, for example,for hardware or vehicle improvements, whichrely on previous developments, improvement ofstages, or integration of existing elements to build up a new system. Nevertheless,government support must be provided forthose activities consisting of the developmentof innovative technologies, new vehicles orstages, or the associated ground infrastructure,for which the risk is higher and where presentworld market pricing prevents the quickamortisation of the investments.

VegaFor the above reasons, ESA has proposed,following an Italian initiative, to undertake, withthe participation of several of its MemberStates, the development of the Vega smalllauncher, targeting the market for smallgovernmental missions to LEO in the payloadclass up to 1500 kg. This small launcher isintended to provide Europe with a low cost andflexible capability for comparatively quickaccess to space, on request. The productionmeans required for such a development, and inparticular those related to solid propulsion, areavailable from the Ariane, and other nationalprogrammes.

In the version currently under consideration,Vega consists of three solid stages (P80, Zefiroand P7), which inject the upper composite intoa low-altitude elliptical orbit. A liquid uppermodule, known as AVUM (Attitude Control andVernier Upper Module), is included in the upper

Artist’s impression ofAriane-5 ESC-B

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Possible medium-launcherconfiguration


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A European medium-size launcherTo serve the satellite-constellation market andmedium-size governmental missions, amedium-size European launch vehicle may bedeveloped, making use of elements derivedfrom Ariane-5 and the small launcher. Themarket for such launcher is largely dependenton the success of the concept of constellationsin LEO and MEO and, although its developmentis currently being studied by ESA, it will beundertaken only once the market is confirmed.Evidence as to the outcome of the firstgeneration of constellations is expected tobecome available at the end of 2001.

Several configurations are presently beinganalysed, which are all built around existingelements, such as the Ariane-5 P230 booster,the Vega P80 motor, the Ariane-5 L10 storableupper stage with new turbopump-fed engine ornew cryogenic stages (H18, H25) based on theVinci engine, development of which is justbeing initiated for Ariane-5. Three possibleoptions are P230/P80/L10, P230/H25 andP80/P80/H18. The final choice will dependessentially on the performance required andtiming on the market, as Europe must not missout on the launch opportunities provided by the second generation of constellations, ifthese are realised. A scenario identified byArianespace in the event of successfuldevelopment of the second generation puts thedemand for constellation deployment at theequivalent of ‘nine half-Ariane-5 launchers’ peryear.

The medium-sized launch vehicle based on theabove elements will help to satisfy these marketrequirements, whilst simultaneously benefittingthe overall Ariane system with increasedproduction needs and synergy of operations.The development of a launcher of this class,relying largely on existing components andground infrastructure, may be mainly funded byprivate investment, if the corresponding marketdemand is indeed confirmed.

composite to improve the accuracy of theprimary injection (compensation of solid-propulsion performance scatter), to circularisethe orbit and to perform the de-orbitingmanoeuvre at the end of the mission. TheAVUM also provides roll control during the finalboost phases and three-axis control duringballistic phases and before payload separation.It may also be used to achieve theunconventional orbits required, for example, forsome scientific missions.

The first stage, P80, will foster the developmentof the advanced technologies required for anew generation of solid motors with higherperformance and lower cost, including a large-diameter filament-wound case for high-pressure operation, a nozzle using a newflexible joint, new thermal protections and anelectric actuation system for the nozzle. Thismotor has replaced the initial low-cost metallicmotor derived from the Ariane-5 booster, dueboth to its greater performance, which allowsmost of the small-mission requirements to becovered, including heavy radar satellites, and tothe opportunity of using the Vega developmentto advance the solid-propulsion technologyrequired for future improvements to Ariane-5.

The Zefiro motor, whose development wasinitiated by FiatAvio with company funding anda contract from the Italian Space Agency, is the second stage of Vega. It has a low-masscarbon-epoxy case, manufactured withfilament-winding technology using high-strength pre-impregnated carbon fibre and acarbon phenolic nozzle with 3D carbon-carbonthroat insert. Two successful motor tests havealready been performed, and a third is inpreparation. Currently, the propellant loading isbeing increased from 16 to 23 tons, byincreasing the length of the motor.

The third stage is a 7-ton solid motor derivedfrom Zefiro, but a liquid storable stage using aturbopump-fed engine was considered as apossible alternative to replace this thirdstage and the vernier module (AVUM).Such an engine could be derived fromthe current Ariane-5 upper-stageengine and would be mainlydeveloped on the basis of industrialinvestments.

The Vega configurations describedwould use the same technologies, thesame production facilities, the sameoperational infrastructure, the samelaunch pad and the same teams as theAriane-5 launcher, thereby achievingmaximum synergy and contributing toAriane-5 cost reductions.

X-33

L10

P80

P230

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Reusable-launcher activitiesIt is believed that the only potential means forfurther significant reduction of the recurrentlaunch cost is to make the launcher partially orcompletely reusable and to greatly increase itsreliability, while preserving its operability.Reductions of one order of magnitude or morewith respect to the Space Shuttle have beenmentioned as the objectives of several studiesand technology developments being supportedby NASA and the US Air Force. In the frameworkof its Reusable Launch Vehicle (RLV) activities,NASA has initiated such developments as theDC-XA, X-34 and X-37 experimental vehicles,the X-33 RLV demonstrator, and many otherstudies and technology activities devoted toadvancing the level of maturity of the criticaltechnologies.

This trend is confirmed in the US FederalBudget request for 2001, which foresees anallocation of about 4.5 billion dollars in theperiod 2001–2005 for the Space LaunchInitiative, covering RLV technology developmentand demonstration. This technology maturationphase is expected to be followed by a decisionin the USA to develop a new vehicle, fundedeither by the government alone or jointly bygovernment and industry.

A major driver for the USA in developing an RLVis the need to replace the ageing Space Shuttlefleet. The Shuttle, with its large cargo capability,will be the main player in the construction andoperation of the International Space Station,but its high operation and maintenance costsand the need for major vehicle refurbishmentlead NASA to envisage a decision on thedevelopment of a second-generation reusabletransportation system by 2005. Trade-offs ofvarious solutions are currently being performed,with a view to producing an operational vehicleby 2012.

The US military could decide, more or less atthe same time, to develop a sub-orbital or

orbital, global-reach space plane to satisfymilitary mission requirements. This interest isconfirmed by a number of developmentssponsored by the US Air Force, such as theinitial DC-X vehicle, the X-40A and the militaryparticipation in the NASA X-37 financing. Sucha global-reach space plane would begovernment funded and would not be availablefor commercial applications, although therewould be the technology return to industry.

In parallel, there are a number of privateinitiatives aimed at developing orbital or sub-orbital reusable vehicles for the smaller payloadclasses. Some of them have gained officialsupport under the NASA programmes and oneor more of these proposed concepts mightreceive sufficient funds to provide a reusable orsemi-reusable small launcher. Demonstrationsof air breathing high-speed propulsion systemsare also being pursued in the USA and around2005 these systems could be considered forthe initial development of long-range, high-speed military applications.

Although it is not clear that the anticipated large cost reductions can indeed be achievedin the short or medium term, these on-goingdevelopments in the USA will allow a betterunderstanding of the critical areas, thedevelopment of new technologies and theoperation in flight of several experimentalvehicles. In the longer term (2015 – 2020),therefore, Europe cannot be sure of maintainingits market share by the use of conventionalexpendable launchers, if a technical break-through is achieved elsewhere. Such step mayinitially result from the need to satisfy USnational requirements, but it could also heavilyaffect the worldwide commercial launch servicescenario.

The FLTP programmeBack in 1994, ESA proposed the FutureEuropean Space Transportation InvestigationsProgramme (FESTIP) to its Member States, in

order to study possible RLV conceptsand initiate the development of therelated technologies. Several launcherconcepts were subsequently designed NASA X-vehicles

X-37 X-34

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phase and to progressively implement suchdemonstrations

– to provide, through the analysis of candidatevehicle concepts and the synthesis of thetechnology activities, elements in support ofa possible programmatic decision on theinitiation of a European developmentprogramme for the next generation oflaunchers, which is currently not expected tobe required before 2007.

The technology developments represent thelargest part of the activities in the first period ofthe FLTP (1999–2001). In particular, strongemphasis is placed on propulsion, largelauncher structures and reusability aspects(e.g. health monitoring, inspections).

The vehicle concept definition work is aimed atthe definition of reference architectures andsystem concepts for future commercialoperational vehicles. It deals more specificallywith:– the selection of dimensioning missions and

the pre-design of a limited number of baselineconfigurations

– the identification of the technologyrequirements that must be met to make theconcepts feasible

– the overall system architecture optimisation,with emphasis on operability and on re-usability assessment

– the performance of cost assessments,including technology development costs,launcher development costs and recurrentoperating costs

– the technology-readiness assessment andthe definition of the programmatic featuresfor a potential future launcher development.

A large number of candidate concepts havebeen studied since the early eighties within theframework of the ESA activities and in nationalprogrammes. Recently, the ESA FESTIPprogramme made a systematic effort tocompare reusable and partially reusablelauncher concepts against common definedrequirements and on the basis of commondesign rules. All of this work will serve as an input to the FLTP. Candidate conceptsinclude both fully reusable and semi-reusablelaunchers.

Semi-reusable concepts, whether Two-Stage-To-Orbit (TSTO), or multiple stage to orbit, canbe considered as technically feasible with thepresent technology. Moreover, they can beviewed as a step towards the development ofmore advanced fully reusable concepts. Suchconcepts have been studied on severaloccasions in Europe. So far, the conclusion hasbeen that the specific recurrent costs achieved

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at a sufficient level of detail to performcomparisons and evaluations of thetechnological developments required, and theassociated development and launch-servicecosts were also assessed. In parallel, a numberof critical technical problems were analysedand hardware developments aimed atdemonstrating possible solutions wereperformed.

To further its understanding of launcherreusability, already investigated in FESTIP andother national programmes, and to improve therelated European technology level, ESAproposed a new optional programme to itsMember States in 1999, namely the FutureLaunchers Technologies Programme (FLTP),the primary objectives of which are:– to confirm the interest of launcher reusability– to identify, develop and validate the

technologies required to make possible thedevelopment of a new generation of costeffective launchers

– to elaborate a plan for the ground and in-flight experimentation and demonstrationsrequired to achieve a sufficient level ofconfidence prior to the vehicle development

The two preferred FESTIPconcepts: Fully reusable

TSTO, and suborbital firststage with an expendable

upper stage

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significant reduction of recurrent costs. Theyare presently seen in Europe as a subject forlong-term research. Initial applications for someof these types of propulsion (ramjet, scramjet)will be in the field of high-speed military craft.

The FLTP technology-development and on-ground demonstration activities include:– rocket-engine cycle analyses and definition

of requirements for reusability– propulsion component development and

testing– demonstration of lightweight reusable

structures (cryogenic tanks, primary structures,thermal protection and hot structures)

– health-monitoring systems for structures andpropulsion systems

– analysis and verification of critical aero-thermodynamic phenomena.

Rocket propulsion has advanced significantlythrough the Ariane programmes, which, inparticular, have allowed Europe to gainexperience with the operation of cryogenicengines. For new launcher concepts, furtheradvances are required in order to introduceengine reusability and operability, to increasethe level of performance and thrust. Forexample, fully reusable vehicles will benefit fromhigher-thrust cryogenic engines than thoseavailable in Europe today.

For these rocket engines, new componentsneed to be developed, such as advancednozzles, new types of injectors, simplified andmore robust turbo machinery, electricallyactuated precision valves, etc. Preliminarydemonstration of these components isessential.

are of the same order as those of today’sAriane-5 (for a higher launcher complexity). The competitiveness of these particularconcepts is therefore difficult to demonstratewith respect to the ELVs expected to beavailable in 15 years from now, and even moreso if the USA offers a fully Reusable LaunchVehicle (RLV) on the market. However, all of thepossibilities for semi-reusable launchers havenot yet been exhausted, which is why the workon such concepts is being pursued within theFLTP.

A particular type of semi-reusable launcher isthe sub-orbital launcher, which requiressomewhat more advanced technology, but stillseems to be within reach. This vehicle doesnot achieve a stable orbit, so that its payloadneeds an additional boost to reach orbitalvelocity, to be provided by an expendableupper stage. The concept is technicallypromising, but its largest uncertainties areassociated with its innovative operation cycle,which includes a downrange landing. Furtherstudies should provide the elements needed tofinally assess the feasibility and costeffectiveness of the concept.

Several fully reusable launcher concepts – bothSingle-Stage-To-Orbit (SSTO) and Two-Stage-To-Orbit (TSTO) – have been proposedworldwide. Some have even progressedtowards the development phase. The TSTOfamily of fully reusable concepts appears to befeasible with the least technology innovation.Further concept trade-offs are required, inparticular related to the return of the first stageto the launch base. Progress in propulsiontechnology may be required if the size of thevehicle is not to become excessive.

The rocket-propelled SSTO reusable launcherconstitutes a large step in terms of thetechnology level required. This option was thegoal of the work performed in the USA byLockheed Martin. So far, the concept studieshave shown a high potential for recurring-costreductions, but with large uncertainties due, inparticular, to the high sensitivity of the design totechnological assumptions. Even for the USA,the technical difficulties and operationalimplications of realising an SSTO launcher areconsiderable and may not be resolved soon.

The reusable launcher concepts usingadvanced air-breathing propulsion, either in theform of a ramjet, supersonic combustion ramjetor air liquefaction, separation and collectiontechniques, require technologies that are veryfar from implementation on operational vehicles.This type of vehicle might be of interest for latergenerations of RLVs, which aim at a further

FLTP technologydemonstrators

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– large airframe elements (inter-tank structure,thrust frame) with integrated health-monitoringsystems

– metallic and non-metallic thermal-protectionsystems improved with respect to mass,reusability and operational constraints

– highly loaded hot structural elements suchas wing leading edges, flaps and rudders,using metallic or composite (C/C and C/SiC)materials

– new health-monitoring and non-destructive-inspection techniques.

Aerothermodynamics is also a key technologyfor reusable launchers, providing the necessaryinputs to all other major technologies such asflight mechanics or structures and thermalprotection.

Roughly ten years ago with the Hermesprogramme, a vast wealth of know-how andcapabilities was generated in Europe. Similarachievements were acquired in nationalprogrammes such as Sänger or PREPHA,which have partly been advanced in FESTIP. Atthe same time, a number of large test facilitieshave been built throughout Europe, allowing asubstantial extension of the possible testdomains.

In order to preserve and improve the availableEuropean hypersonic know-how, in FLTP workwill be performed on a limited number of basicaerothermodynamic launcher problems (e.g.base drag, effect of multiple propulsion plumes,shock-wave/boundary-layer interaction, laminar/turbulent transition, etc.), which are critical forthe practical design of reusable launchers.

However, the area in which Europe needs tomake major progress is that of in-flightexperimentation. Many of the phenomenainfluencing the mission of a reusable launchercannot be reproduced on the ground, and in-flight experimentation is the only means ofverifying the theoretical predictions andreducing the technological risk, before startingfull-scale vehicle development. Today Europehas no direct experience with high-speed flightand atmospheric reentry by large wingedvehicles. Moreover, the shape of these vehiclesis often driven by the high-speed flight qualities,resulting in poor low-speed aerodynamics,which makes it difficult to perform low-speedmanoeuvres and automatic landings. Noexperience with the reusability of materials,structures and repeated operation ofpropulsion systems is available.

For similar reasons, great emphasis has beenplaced in the USA since the 60’s on the design,manufacture and testing of dedicated

The EXTV – a flight-testproposal vehicle resulting

from the FESTIP studies

For reusable engines, reliability in flight andrapid maintenance on the ground are essentialaspects. This means that a completely newdesign approach is required, which greatlyreduces the need for acceptance testing, relieson an integrated health-monitoring system, andmakes it possible to control or limit the effectsof failures.

Launcher cost reduction and performanceimprovement also rely on advanced materials,manufacturing processes and improvedstructural concepts, which allow lower operatingcosts, reduced vehicle dry masses, as well asreliable, maintainable and health-monitoredstructures. As a design goal, the structuresmust have the lowest possible massescompatible with the combined mechanical,thermal and fatigue load, reusability and costobjectives.

Europe has acquired experience in themanufacturing of metallic and compositeexpendable structures. Optimisation of designwith regard to non-conventional reusablestructural concepts and investigation of materialcharacteristics associated with reusability(cyclic loading, environmental resistance, long-term compatibility with propellants, fatigue,operational life including reentry, repairtechniques and non-destructive inspection) willinduce structural ratio improvements that canonly be verified by representative vehiclestructure demonstrations.

Therefore within FLTP it is planned to design,manufacture and test:– a low-mass, reusable composite cryogenic

tank– a light metallic (aluminium-lithium) cryogenic

tank

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The definition of flight passenger experimentsand testbeds will be initiated in the first phaseof the programme. However, the major emphasisin this phase will be on the elaboration ofproposals for experimental vehicles, to beimplemented in the programme continuation.

The decision to actually develop a reusablelauncher will largely depend on the evolution ofthe international market and competition. Sincethe Space Shuttle will remain in service untilabout 2012, a US RLV development decision isplanned around 2005.

In formulating its own strategy, Europe will haveto consider both autonomous developments aswell as international cooperation, in order toadvance its technology level. In particular, itshould be taken into account that the first RLV in the USA may be developed for thegovernmental missions to the InternationalSpace Station and preparation of a spaceexploration infrastructure. Europe may becalled upon to participate in some aspects ofsuch development. Commercial vehicles willrepresent a later spin-off of the government-funded developments. Europe must thereforeconsider carefully what are the most effectivesteps for reducing the vehicle development risk to acceptable levels before possiblycommitting to its own RLV development effortaround 2006 – 2007.

ConclusionOn the basis of the anticipated world-widelaunch-service scenario outlined above and thealready defined European objectives, threelines of action should be pursued:– to maintain Ariane-5’s competitiveness in the

short and medium term, by improvements tothe launcher (greater mission versatility,increased launcher performance, optimisationof production and operations) aimed atreducing specific launch cost

– to complete the range of launch servicesoffered by the possible addition of European-manufactured small- and medium-sizedlaunchers, in order to compete effectively onthe international market

– to prepare the technology needed for thetimely development of the new systems thatmay be required in the longer term (2015 –2020).

These three steps will together allow Europe toretain its current leading position in the launchmarket and maintain its independent access tospace, which is crucial for any future strategicspace activity. r


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experimental vehicles, which paved the way forthe Space Shuttle’s development. The Shuttlein turn is today providing a large amount offlight data, which the USA can use to design asecond generation of reusable launch vehicles.Nevertheless, as mentioned above, severaladditional X-vehicles are currently beingdeveloped or are planned by NASA to gainadditional operational experience in the variousaspects of reusable launcher missions.

In Europe, atmospheric re-entry experience hasbeen gained with ESA’s Atmospheric ReentryDemonstrator (ARD) and other capsulesdeveloped at national level and in militaryactivities. But none of these vehicles wasreusable, nor had a shape comparable to areusable launcher.

Within the FESTIP programme, ESA haspursued flight opportunities for passengerexperiments on ‘foreign’ vehicles. For example,an agreement has been concluded with NASAwhich will allow repeated flights on the X-34vehicle of two European thermal-protectionsystems.

In parallel, in the framework of the InternationalSpace Station activities, Europe is participatingin the development of the X-38 and CRVvehicles, which with their demonstration flightswill offer an additional opportunity for testingEuropean elements under reentry conditions.

The preparation of a coherent flightexperimentation approach is an essential partof the FLTP. The requisite flight activities will bedefined at an early phase in the FLTP on thebasis of the needs identified, including costevaluation of the corresponding hardwaredevelopment and testing. In-flight experimentswill be progressively implemented according tothe level of technological maturity achieved andthe available flight opportunities.

Part of the overall FLTP in-flight experimentationactivities will be:– elaboration of a flight experimentation strategy– definition of in-flight experiments as

passengers on existing vehicles, includingopportunities for international co-operation

– development and testing of flying testbedsfocussing on the validation of specifictechnologies and operational aspects requiredfor future European launchers

– elaboration of a technical and programmaticproposal for the development of theexperimental vehicles required for masteringthe various phases of the reusable launchermission

– design, development and in-flight testing ofselected experimental vehicles.

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the future of european launchers: the esa perspective

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