esa bulletin 123 - august 2005 7

FLPP

The Road to theNext-GenerationEuropean Launcher– An overview of the FLPP

The Road to theNext-GenerationEuropean Launcher– An overview of the FLPP T he Future Launchers Preparatory

Programme (FLPP) was approved by thelast ESA Ministerial Council and began in

February 2004, ending a long period without aprogramme dedicated to future launchers at theEuropean level. The aim is to prepare the NextGeneration Launcher to be operational around2020. System studies and technology activitiestherefore need to be conducted, includingground and in-flight tests, to foster newtechnologies capable of providing highperformance and reliability, together with lowlife-cycle costs. The final choice between anexpendable or reusable type of launch vehiclewill be made on the basis of proventechnological readiness and consolidated costand risk assessments.

ProgrammaticsThe Agency’s Future LaunchersPreparatory Programme was initiated inFebruary 2004 with the aim of preparingfor the development of Europe’s Next-Generation Launcher (NGL). The FLPP isdesigned to strengthen European industry’sinnovative technology competences andfoster progress in the launcher field inorder to safeguard Europe’s guaranteedaccess to space in the longer term. Thechoice for the best Earth-to-orbit launchsystem architecture is essentially betweenan advanced expendable launcher and afully or partially reusable vehicle. Thefinal decision will be made on the basis ofcompetitive launch cost and marketrequirements, such as expectedcommercial payloads and the Europeaninstitutional mission needs stemming, for

Jürgen Ackermann, Jérôme Breteau, Jens Kauffmann, Guy Ramusat & Giorgio TuminoFuture Launchers Preparatory Programme,Directorate of Launchers, ESA, Paris

Ackermann 9/13/05 10:45 AM Page 6

esa bulletin 123 - august 2005 7

FLPP

The Road to theNext-GenerationEuropean Launcher– An overview of the FLPP

The Road to theNext-GenerationEuropean Launcher– An overview of the FLPP T he Future Launchers Preparatory

Programme (FLPP) was approved by thelast ESA Ministerial Council and began in

February 2004, ending a long period without aprogramme dedicated to future launchers at theEuropean level. The aim is to prepare the NextGeneration Launcher to be operational around2020. System studies and technology activitiestherefore need to be conducted, includingground and in-flight tests, to foster newtechnologies capable of providing highperformance and reliability, together with lowlife-cycle costs. The final choice between anexpendable or reusable type of launch vehiclewill be made on the basis of proventechnological readiness and consolidated costand risk assessments.

ProgrammaticsThe Agency’s Future LaunchersPreparatory Programme was initiated inFebruary 2004 with the aim of preparingfor the development of Europe’s Next-Generation Launcher (NGL). The FLPP isdesigned to strengthen European industry’sinnovative technology competences andfoster progress in the launcher field inorder to safeguard Europe’s guaranteedaccess to space in the longer term. Thechoice for the best Earth-to-orbit launchsystem architecture is essentially betweenan advanced expendable launcher and afully or partially reusable vehicle. Thefinal decision will be made on the basis ofcompetitive launch cost and marketrequirements, such as expectedcommercial payloads and the Europeaninstitutional mission needs stemming, for

Jürgen Ackermann, Jérôme Breteau, Jens Kauffmann, Guy Ramusat & Giorgio TuminoFuture Launchers Preparatory Programme,Directorate of Launchers, ESA, Paris

Ackermann 9/13/05 10:45 AM Page 6

esa bulletin 123 - august 2005www.esa.int 9

In its first two years, the FLPPprogramme is concentrating on assessingthe attractiveness of reusability from thelauncher affordability and robustnessstandpoints. Decisive progress has to bemade, however, with respect to currenttechnology to achieve a robust, low-cost,reusable system. The system requirements,overall development logic and tech-nological demonstrations required todesign and build such a demanding vehicleare going to be assessed, focusing on themost critical areas, like propulsion,materials and structures, aerothermo-dynamics, vehicle health management andavionics. These new technologies will beable to foster new system concepts. Inaddition, Europe plans to develop andoperate hypersonic experimental vehiclesfor flight demonstrations, when deemednecessary to overcome technologybarriers, study critical flight phases andassess reusability.

A cornerstone of the European launchersstrategy is optimum use of availableresources. Therefore on the one hand aharmonisation of all European activitiesfor future launchers has been initiated, andon the other the FLPP will permit theprogressive restructuring of the Europeanindustrial landscape in preparation for afuture cost-effective NGL developmentand exploitation programme. From thestart, a number of cooperative activities inthe RLV field have been identified, notleast with Russia.

System StudiesThere is already a solid base of experienceand technology in Europe for the design ofELVs, which is being exploited to establishthe system-level capabilities needed toassess the risks inherent in developing andoperating RLVs. One of the main goals ofthe FLPP studies is to assess theattractiveness of launcher reusability bycomparing the economic features of thebest RLV options accessible for Europewith the possible ELV solutions on thebasis of comparable Technology ReadinessLevel (TRL).

The system work will have toaccomplish multiple objectives. RLVsystem design concepts will be developed

to allow quantification of performance,flexibility of operations, reliability, costand safety. On the basis of these concepts,a number of system-level trade-offsdealing with such aspects as propellantcombinations, stage arrangements, launchmodes and return-flight options will beperformed. A further task will be toelaborate guidelines and well-quantifiedobjectives for the RLV technologydevelopments in order to be able tomonitor their coherence and feed theresults into the vehicle concept studies.The objectives for the in-flight and on-ground experiments and demonstrationswill also be derived from the system needs.At a later stage, i.e. during FLPP Period-2,system studies of expendable NGLconcepts will be started, leading to a

thorough trade-off between the ELV andRLV concepts. This important decisionwill be largely based on the final missionspecification, but will also rely on theresults of critical-technology validationtests.

FLPP Period-1 is characterised by afocused approach, aiming at the selectionof one preferred RLV concept for each oftwo preliminary ‘reference missions’. Theavailability of results from a number ofprevious national and European RLVstudies, such as ESA’s Future EuropeanSpace Transportation InvestigationProgramme (FESTIP, 1995-1998), allowFLPP to focus just on what are seen as thecurrently most promising concepts,namely:

• semi-reusable concepts using a LiquidFly-Back Booster (LFBB) or ReusableFirst Stage (RFS)

• sub-orbital concepts• fully reusable Two Stage To Orbit

(TSTO) concepts.

Considerable experience in the analysis ofthese options already exists in Europe.Aside from FESTIP, other studies havebeen performed in recent years in France(e.g. SYS RLV) and Germany (e.g.ASTRA) on concepts belonging to thesecategories and their results will also beexploited in the FLPP system activities.The semi-reusable RLV concepts are anattractive area for potential cooperationwith Russia, where joint activities on theanalysis of reusable liquid stages will beconsidered.

Single Stage To Orbit (SSTO) conceptsand air-breathing ascent propulsionsystems (e.g. Scramjet) will not beaddressed as they do not meet thetechnology-maturity requirements.

In-flight ExperimentationFor any RLV development effort, in-flight

FLPP

8 esa bulletin 123 - august 2005 www.esa.int

instance, from the new ESA spaceexploration programme and theimplementation of European Union policyconcerning environment, security anddefence.

It is essential for Europe to retain itsautonomous, affordable and competitiveaccess to space both now and in the future.The near-term needs are covered by theEuropean launcher workhorse Ariane-5, tobe complemented in the near future by theVega small launch vehicle and operation ofthe Russian Soyuz launcher also fromKourou. Looking further ahead, however,Europe must already begin to prepare theprogrammatic and technical ground inorder to be able to undertake thedevelopment of an NGL a decade fromnow.

Among the various solutions promisingaffordable access to space, ReusableLaunch Vehicles (RLVs) offer the potentialfor major cost reductions well beyondthose provided by on-going improvements

to Expendable Launch Vehicles (ELVs).Before being able to make a sound choicebetween an ELV and an RLV for the NextGeneration Launcher, a number of criticalreusability-related technologies need to bedeveloped and demonstrated, as well as

acquiring RLV system-level expertise.Before finally deciding on the NGL’sdevelopment, there is a need for sufficientmaturity of system and technologycompetencies to assess the associated costsand risks.

Launchers

Industrial Policy

It was decided at the outset to grant all NGL-related activities within FLPP to anindustrial prime contractor, and EADS and Finmeccanica have therefore created anew company, provisionally called ‘NGL Prime Co’.

The industrial work at system and technology level began at the end of 2004, with acomprehensive road map of activities that will provide, step by step, the resultsneeded for the decision on the NGL to be taken at the end of the decade.

The industrial activities in 2005 encompass RLV system concept studies togetherwith the preparation of on-ground demonstrations for various structure andpropulsion subsystems, as well as the progressive implementation of in-flightdemonstrations with testbeds and experimental vehicles.

The current family of launchers that will be operating in the near-and medium-term from the European Spaceport in Kourou,French Guiana

Ariane-5 G Ariane-5 ECA Ariane-5 ES Soyuz Vega

Sub-orbital concept (Courtesy of DLR)

LFBB concept (Courtesy of DLR)

TSTO concept (Courtesy of CNES)

Ackermann 9/13/05 10:45 AM Page 8

esa bulletin 123 - august 2005www.esa.int 9

In its first two years, the FLPPprogramme is concentrating on assessingthe attractiveness of reusability from thelauncher affordability and robustnessstandpoints. Decisive progress has to bemade, however, with respect to currenttechnology to achieve a robust, low-cost,reusable system. The system requirements,overall development logic and tech-nological demonstrations required todesign and build such a demanding vehicleare going to be assessed, focusing on themost critical areas, like propulsion,materials and structures, aerothermo-dynamics, vehicle health management andavionics. These new technologies will beable to foster new system concepts. Inaddition, Europe plans to develop andoperate hypersonic experimental vehiclesfor flight demonstrations, when deemednecessary to overcome technologybarriers, study critical flight phases andassess reusability.

A cornerstone of the European launchersstrategy is optimum use of availableresources. Therefore on the one hand aharmonisation of all European activitiesfor future launchers has been initiated, andon the other the FLPP will permit theprogressive restructuring of the Europeanindustrial landscape in preparation for afuture cost-effective NGL developmentand exploitation programme. From thestart, a number of cooperative activities inthe RLV field have been identified, notleast with Russia.

System StudiesThere is already a solid base of experienceand technology in Europe for the design ofELVs, which is being exploited to establishthe system-level capabilities needed toassess the risks inherent in developing andoperating RLVs. One of the main goals ofthe FLPP studies is to assess theattractiveness of launcher reusability bycomparing the economic features of thebest RLV options accessible for Europewith the possible ELV solutions on thebasis of comparable Technology ReadinessLevel (TRL).

The system work will have toaccomplish multiple objectives. RLVsystem design concepts will be developed

to allow quantification of performance,flexibility of operations, reliability, costand safety. On the basis of these concepts,a number of system-level trade-offsdealing with such aspects as propellantcombinations, stage arrangements, launchmodes and return-flight options will beperformed. A further task will be toelaborate guidelines and well-quantifiedobjectives for the RLV technologydevelopments in order to be able tomonitor their coherence and feed theresults into the vehicle concept studies.The objectives for the in-flight and on-ground experiments and demonstrationswill also be derived from the system needs.At a later stage, i.e. during FLPP Period-2,system studies of expendable NGLconcepts will be started, leading to a

thorough trade-off between the ELV andRLV concepts. This important decisionwill be largely based on the final missionspecification, but will also rely on theresults of critical-technology validationtests.

FLPP Period-1 is characterised by afocused approach, aiming at the selectionof one preferred RLV concept for each oftwo preliminary ‘reference missions’. Theavailability of results from a number ofprevious national and European RLVstudies, such as ESA’s Future EuropeanSpace Transportation InvestigationProgramme (FESTIP, 1995-1998), allowFLPP to focus just on what are seen as thecurrently most promising concepts,namely:

• semi-reusable concepts using a LiquidFly-Back Booster (LFBB) or ReusableFirst Stage (RFS)

• sub-orbital concepts• fully reusable Two Stage To Orbit

(TSTO) concepts.

Considerable experience in the analysis ofthese options already exists in Europe.Aside from FESTIP, other studies havebeen performed in recent years in France(e.g. SYS RLV) and Germany (e.g.ASTRA) on concepts belonging to thesecategories and their results will also beexploited in the FLPP system activities.The semi-reusable RLV concepts are anattractive area for potential cooperationwith Russia, where joint activities on theanalysis of reusable liquid stages will beconsidered.

Single Stage To Orbit (SSTO) conceptsand air-breathing ascent propulsionsystems (e.g. Scramjet) will not beaddressed as they do not meet thetechnology-maturity requirements.

In-flight ExperimentationFor any RLV development effort, in-flight

FLPP

8 esa bulletin 123 - august 2005 www.esa.int

instance, from the new ESA spaceexploration programme and theimplementation of European Union policyconcerning environment, security anddefence.

It is essential for Europe to retain itsautonomous, affordable and competitiveaccess to space both now and in the future.The near-term needs are covered by theEuropean launcher workhorse Ariane-5, tobe complemented in the near future by theVega small launch vehicle and operation ofthe Russian Soyuz launcher also fromKourou. Looking further ahead, however,Europe must already begin to prepare theprogrammatic and technical ground inorder to be able to undertake thedevelopment of an NGL a decade fromnow.

Among the various solutions promisingaffordable access to space, ReusableLaunch Vehicles (RLVs) offer the potentialfor major cost reductions well beyondthose provided by on-going improvements

to Expendable Launch Vehicles (ELVs).Before being able to make a sound choicebetween an ELV and an RLV for the NextGeneration Launcher, a number of criticalreusability-related technologies need to bedeveloped and demonstrated, as well as

acquiring RLV system-level expertise.Before finally deciding on the NGL’sdevelopment, there is a need for sufficientmaturity of system and technologycompetencies to assess the associated costsand risks.

Launchers

Industrial Policy

It was decided at the outset to grant all NGL-related activities within FLPP to anindustrial prime contractor, and EADS and Finmeccanica have therefore created anew company, provisionally called ‘NGL Prime Co’.

The industrial work at system and technology level began at the end of 2004, with acomprehensive road map of activities that will provide, step by step, the resultsneeded for the decision on the NGL to be taken at the end of the decade.

The industrial activities in 2005 encompass RLV system concept studies togetherwith the preparation of on-ground demonstrations for various structure andpropulsion subsystems, as well as the progressive implementation of in-flightdemonstrations with testbeds and experimental vehicles.

The current family of launchers that will be operating in the near-and medium-term from the European Spaceport in Kourou,French Guiana

Ariane-5 G Ariane-5 ECA Ariane-5 ES Soyuz Vega

Sub-orbital concept (Courtesy of DLR)

LFBB concept (Courtesy of DLR)

TSTO concept (Courtesy of CNES)

Ackermann 9/13/05 10:45 AM Page 8

esa bulletin 123 - august 2005www.esa.int 11

(Phase-A type) study of the proposedconcept as part of the short-term in-flight experimentation strategy

– identify promising Class-3 vehicleconcepts, such as Reuse-X, reflecting onamong other things specific propulsionsystem requirements.

The concepts selected will be furtherinvestigated during the second part ofFLPP Period-1.

Bringing together the ESA programmeand currently running national initiatives isclearly the best means of ensuring that in-flight experimentation really takes place inEurope and that a true technological returnon the investments made is created forMember States. Given Russia’sconsiderable experience in this field, itscooperation will also be considered with aview to reducing demonstration risks andthe associated costs.

PropulsionThe main propulsion system’s technicalcomplexity and interaction with the overallperformance and operational capabilitiesof an ELV or RLV gives propulsion a key

role in launcher development and makesits operational implementation a majorchallenge. Today, operational experiencewith RLV rocket engines is still ratherlimited. The US Space Shuttle and theRussian Energia/Buran vehicles rely on theonly flight-proven reusable (or robust)rocket engines, and their experiences haveshown how technically demanding thereusability requirement really is. This iswhy the initiation of development inEurope of high-performance reusablerocket engines is an ambitious challengethat will have to be carefully responded towithin FLPP. Success within the scheduleforeseen will rely on existing Europeanindustrial and national-agency know-howand the fact that the key players of theEuropean propulsion industry aremembers of the NGL Joint PropulsionTeam defining the future engines.

Basically, the propulsion activities inFLPP Period-1 include two parallel andinterdependent sets of system andtechnology activities aiming at achievingappropriate technology-readiness levelsfor identified critical technologies. Atsystem level, the studies and tradeoffs on

propulsion cycles and architectures (gasgenerator, staged combustion, full-flowstaged combustion), high-performancepropellants (LOx-LH2 and hydrocarbons),and requirements definition and design-method elaboration are being closelycoordinated with the parallel launchersystem studies. At technology level,activities on already identified criticaltechnologies are in progress for majorcomponents such as turbo pumps, valves,health-monitoring systems, nozzles, thrustchambers and pre-burners. All of theseactivities involve representative testing attechnology, component or subsystem level.A set of activities designed to improvesolid-propulsion cost efficiency andcombustion characteristics is also includedin FLPP Period-1.

During FLPP Period-2, the technology-demonstration activities will be continuedwith increasingly representative scales ofhardware. All key engine technologies willbe test-proven with component and/orengine-level demonstrators before the finaldevelopment decision for the NextGeneration Launcher is taken.

Risk management is a cornerstone of theFLPP propulsion activities due to the closeinteraction of the system-design activitieswith the convergence process at thepropulsion system and technology levels.

Materials and StructuresA technology-development effort onstructures and materials is included in theFLPP themes to distil a burgeoning arrayof advanced structural concepts down tothose that are close enough to maturity forapplication in fully or partially reusablelaunch vehicles and should provide thebest performance at an affordable cost.Major challenges include reducing overallstructural mass, increasing structuralmargins for robustness, reusablecontainment of cryogenic hydrogen andoxygen propellants, reusable thermal-protection system, significantly reducingoperational costs for inspection and re-validation of structures and sustainability,all of which must be addressed in closecooperation with the other themes of theprogramme.

FLPP

10 esa bulletin 123 - august 2005 www.esa.int

experimentation is indispensable both for validating system and tech-nology performance models, as well as for gathering the first operationalexperience. Past experience withexperimental vehicles shows that a step-by-step flight-demonstration approachallows one to limit the risks with aprogressive investment effort, especiallyfor the most technically challengingdevelopments.

The various European studies andprojects conducted to date involving in-flight experimentation have been evaluatedin the frame of an ESA ‘harmonisation’study, resulting in the identification ofthree distinct in-flight experimentationlevels, or classes of vehicles:

Class-1: ‘Flying Test Beds’, focusing ondesign-tool validation and dedicated to asingle discipline, and thus not concept orsystem representative.

Class-2: ‘Intermediate ExperimentalVehicles’, focusing on the integration at

system level of key technologies, such asvehicle thermal-protection and health-management system components andflight controllability by means ofaerodynamic control surfaces.

Class-3: ‘Experimental Vehicles’,aiming at validation of a combination oftechnologies and system-design capab-ilities, such as shape representativeness,fully integrated thermal-protectionsystems, guidance, navigation and control,vehicle health-management systems,reusability and operations.

An approach taking into account thesethree classes of vehicles has been adoptedfor the FLPP in order to reduce thedevelopment risks. Considering theexisting planned development schedule fora series of Class-1 type vehicles (e.g.EXPERT, PHOENIX-1, etc.), it wasdeemed appropriate for FLPP to focus onClass-2 and Class-3 and so the industrialsystem team has been tasked in Period-1 to: – define an optimised long-term in-flight

experimentation strategy– select the most promising Class-2

Intermediate Experimental Vehicle(IXV) and perform a consolidation

Launchers

The European Heritage Regarding RLVs

Several system studies were conducted during the 1980s to investigate possibleconcepts for a European RLV, both at ESA level (FLS, WLC, RRL, FESTIP, as wellas the Hermes Programme which included some RLV-related technologies andfacilities) and at national level (Hotol, Sanger, Taranis, Star-H, WLC, STS 2000,FLS and RRL).

In 1998, ESA flew the Atmospheric Re-entry Demonstrator (ARD) capsule, whichprovided valuable information on atmospheric re-entry.

The Agency’s Future Launchers Technologies Programme (FLTP) was approved in1999 with the objectives of confirming the interest of launcher reusability underrealistic assumptions, and of identifying, developing and validating the requiredtechnologies. The unbalanced participation in the programme by Member States andthe consequent problems with implementing procedures resulted in the FLTP beingput on hold.

Several programmes were, however, set up in Europe, both at national level (e.g.Astra, Prora and Prepha, as well as vehicle concept studies like Boomerang, Astral,USV and Everest) and ESA level (X-38/CRV), to foster the development of some ofthe technologies required for future reusable space transportation systems.

Moreover, some specific RLV technologies are still being developed within the ESATechnology Research Programme (TRP) and General Support TechnologyProgramme (GSTP).

Concepts for potential engines for Reusable or Expendable Launch Vehicles (Courtesy of SNECMA Moteurs)

High performance RLV

High performance RLV Low cost ELV

Vulcain evolution

Ackermann 9/13/05 10:45 AM Page 10

esa bulletin 123 - august 2005www.esa.int 11

(Phase-A type) study of the proposedconcept as part of the short-term in-flight experimentation strategy

– identify promising Class-3 vehicleconcepts, such as Reuse-X, reflecting onamong other things specific propulsionsystem requirements.

The concepts selected will be furtherinvestigated during the second part ofFLPP Period-1.

Bringing together the ESA programmeand currently running national initiatives isclearly the best means of ensuring that in-flight experimentation really takes place inEurope and that a true technological returnon the investments made is created forMember States. Given Russia’sconsiderable experience in this field, itscooperation will also be considered with aview to reducing demonstration risks andthe associated costs.

PropulsionThe main propulsion system’s technicalcomplexity and interaction with the overallperformance and operational capabilitiesof an ELV or RLV gives propulsion a key

role in launcher development and makesits operational implementation a majorchallenge. Today, operational experiencewith RLV rocket engines is still ratherlimited. The US Space Shuttle and theRussian Energia/Buran vehicles rely on theonly flight-proven reusable (or robust)rocket engines, and their experiences haveshown how technically demanding thereusability requirement really is. This iswhy the initiation of development inEurope of high-performance reusablerocket engines is an ambitious challengethat will have to be carefully responded towithin FLPP. Success within the scheduleforeseen will rely on existing Europeanindustrial and national-agency know-howand the fact that the key players of theEuropean propulsion industry aremembers of the NGL Joint PropulsionTeam defining the future engines.

Basically, the propulsion activities inFLPP Period-1 include two parallel andinterdependent sets of system andtechnology activities aiming at achievingappropriate technology-readiness levelsfor identified critical technologies. Atsystem level, the studies and tradeoffs on

propulsion cycles and architectures (gasgenerator, staged combustion, full-flowstaged combustion), high-performancepropellants (LOx-LH2 and hydrocarbons),and requirements definition and design-method elaboration are being closelycoordinated with the parallel launchersystem studies. At technology level,activities on already identified criticaltechnologies are in progress for majorcomponents such as turbo pumps, valves,health-monitoring systems, nozzles, thrustchambers and pre-burners. All of theseactivities involve representative testing attechnology, component or subsystem level.A set of activities designed to improvesolid-propulsion cost efficiency andcombustion characteristics is also includedin FLPP Period-1.

During FLPP Period-2, the technology-demonstration activities will be continuedwith increasingly representative scales ofhardware. All key engine technologies willbe test-proven with component and/orengine-level demonstrators before the finaldevelopment decision for the NextGeneration Launcher is taken.

Risk management is a cornerstone of theFLPP propulsion activities due to the closeinteraction of the system-design activitieswith the convergence process at thepropulsion system and technology levels.

Materials and StructuresA technology-development effort onstructures and materials is included in theFLPP themes to distil a burgeoning arrayof advanced structural concepts down tothose that are close enough to maturity forapplication in fully or partially reusablelaunch vehicles and should provide thebest performance at an affordable cost.Major challenges include reducing overallstructural mass, increasing structuralmargins for robustness, reusablecontainment of cryogenic hydrogen andoxygen propellants, reusable thermal-protection system, significantly reducingoperational costs for inspection and re-validation of structures and sustainability,all of which must be addressed in closecooperation with the other themes of theprogramme.

FLPP

10 esa bulletin 123 - august 2005 www.esa.int

experimentation is indispensable both for validating system and tech-nology performance models, as well as for gathering the first operationalexperience. Past experience withexperimental vehicles shows that a step-by-step flight-demonstration approachallows one to limit the risks with aprogressive investment effort, especiallyfor the most technically challengingdevelopments.

The various European studies andprojects conducted to date involving in-flight experimentation have been evaluatedin the frame of an ESA ‘harmonisation’study, resulting in the identification ofthree distinct in-flight experimentationlevels, or classes of vehicles:

Class-1: ‘Flying Test Beds’, focusing ondesign-tool validation and dedicated to asingle discipline, and thus not concept orsystem representative.

Class-2: ‘Intermediate ExperimentalVehicles’, focusing on the integration at

system level of key technologies, such asvehicle thermal-protection and health-management system components andflight controllability by means ofaerodynamic control surfaces.

Class-3: ‘Experimental Vehicles’,aiming at validation of a combination oftechnologies and system-design capab-ilities, such as shape representativeness,fully integrated thermal-protectionsystems, guidance, navigation and control,vehicle health-management systems,reusability and operations.

An approach taking into account thesethree classes of vehicles has been adoptedfor the FLPP in order to reduce thedevelopment risks. Considering theexisting planned development schedule fora series of Class-1 type vehicles (e.g.EXPERT, PHOENIX-1, etc.), it wasdeemed appropriate for FLPP to focus onClass-2 and Class-3 and so the industrialsystem team has been tasked in Period-1 to: – define an optimised long-term in-flight

experimentation strategy– select the most promising Class-2

Intermediate Experimental Vehicle(IXV) and perform a consolidation

Launchers

The European Heritage Regarding RLVs

Several system studies were conducted during the 1980s to investigate possibleconcepts for a European RLV, both at ESA level (FLS, WLC, RRL, FESTIP, as wellas the Hermes Programme which included some RLV-related technologies andfacilities) and at national level (Hotol, Sanger, Taranis, Star-H, WLC, STS 2000,FLS and RRL).

In 1998, ESA flew the Atmospheric Re-entry Demonstrator (ARD) capsule, whichprovided valuable information on atmospheric re-entry.

The Agency’s Future Launchers Technologies Programme (FLTP) was approved in1999 with the objectives of confirming the interest of launcher reusability underrealistic assumptions, and of identifying, developing and validating the requiredtechnologies. The unbalanced participation in the programme by Member States andthe consequent problems with implementing procedures resulted in the FLTP beingput on hold.

Several programmes were, however, set up in Europe, both at national level (e.g.Astra, Prora and Prepha, as well as vehicle concept studies like Boomerang, Astral,USV and Everest) and ESA level (X-38/CRV), to foster the development of some ofthe technologies required for future reusable space transportation systems.

Moreover, some specific RLV technologies are still being developed within the ESATechnology Research Programme (TRP) and General Support TechnologyProgramme (GSTP).

Concepts for potential engines for Reusable or Expendable Launch Vehicles (Courtesy of SNECMA Moteurs)

High performance RLV

High performance RLV Low cost ELV

Vulcain evolution

Ackermann 9/13/05 10:45 AM Page 10

12 esa bulletin 123 - august 2005 www.esa.int

To be economically viable, the stages of anRLV must be able to withstand repeatedly theharsh environmental conditions encounteredduring all phases of the mission. All elementscontributing to the dry mass of the vehicle(e.g. primary structures, engines, tanks,thermal-protection systems, etc.) must becost effective and as light as possible in orderto give each stage the structural indexcompatible with high robustness.

Improving the performance and reducingthe cost of RLV primary structures largelyrelies on identifying and developinginnovative reusable structural concepts andarchitectures, adequate advanced materialsand manufacturing processes, and refinedanalytical techniques allowing reducedvehicle dry mass together with low operatingcosts. The various structural subsystems of a

typical RLV will be subjected to complexloadings and temperature conditions, leadingto severe thermo-mechanical gradients. Thestructures that carry loads from one part ofthe launcher to another must have goodreliability, availability and maintainabilityand require as little maintenance, repair andoverhaul as possible, which can partly beachieved through the use of ‘structural healthmonitoring systems’. One approach is to useCFRP structures with fibre-optic sensorsembedded at critical locations within thematrix and other innovative sensors attachedto the structure’s surface.

Propellant tanks form a large part of thevehicle’s structure and dominate the airframedesign effort, influencing as a consequencethe aerodynamic and thermal aspects of thevehicle’s configuration. The design and

manufacture of large reusable cryogenicpropellant tanks are very complex, be theymetallic or composite structures. The factthat RLVs ascend into orbit full of cryogenicpropellant and return with almost emptytanks presents particular thermal andstructural challenges. Mastering thefabrication of reusable, high-volumetric-efficiency, cryogenic propellant tanks istherefore one of the key technologies forRLV development.

The FLPP will also address thedevelopment of an advanced, reusablethermal-protection system and load-carryinghot-structure subsystems. These will bothprotect the vehicle airframe from the thermalloads imposed by the high temperaturesreached and the harsh environmentsencountered at several points during ascentand re-entry, and contribute to its externalaerodynamic shape. The programme willbegin to overcome the hurdles of developingreusable metallic and ceramic structuresdedicated to large-area applications atelevated temperature. The thermal protectionmust not only be lightweight and cost-effective, but also durable, involvingminimum maintenance or repair.

ConclusionThe Future Launchers PreparatoryProgramme will leverage existing Europeantechnology investments in the field ofreusable concepts based on the large effortsmade over the last 15 years with fundingfrom ESA and national agencies. Thechallenge in the FLPP technology effort willbe to define, design, analyse, build and test,either on the ground or in flight, variousrepresentative demonstrators validating therequirements defined in the FLPP systemstudies. This proactive demonstrator policywill foster rapid technology maturation,focusing on concrete targets such as theexperimental vehicle (IXV) dedicated toreentry technologies. As a system-concept-driven technology programme, the FLPPcombines innovation with addressing futuremarket needs. r

Launchers

CFRP intertank subscale demonstrator structure for a futurereusable launcher, including an embedded fibre-optic healthmonitoring system (Courtesy EADS-CASA and Contraves Space)

Reusable rudder metallic structure building-block element (Courtesy of Dutch Space)

Ackermann 9/13/05 10:45 AM Page 12