BR-138

October 1998

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Directorate of Manned Spaceflight and MicrogravityDirection des Vols Habités et de la Microgravité

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The Atmospheric Reentry Demonstrator

BR-138-COVER 30-09-1998 11:34 Page 1

The

Atmospheric

Reentry

Demonstratornn

BR-138

October 1998

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ARD 29-09-1998 17:02 Page 1

Seven thrusters willorient the ARD duringatmospheric entry.

atmosphere. It will test and qualify reentrytechnologies and flight control algorithmsunder actual flight conditions.

In particular, the ARD has the followingmain demonstration objectives:– validation of theoretical

aerothermodynamic predictions,– qualification of the design of the

thermal protection system and ofthermal protection materials,

– assessment of navigation, guidanceand control system performances.

What is the AtmosphericReentry Demonstrator?ESA’s Atmospheric Reentry Demonstrator(ARD) is a major step towards developingand operating space transportationvehicles that can return to Earth, whethercarrying payloads or people. For the firsttime, Europe will fly a complete spacemission – launching a vehicle into spaceand recovering it safely.

The ARD is an unmanned, 3-axis stabilisedautomatic capsule that will be launchedon top of an Ariane-5 from the Europeanspace port at the Guiana Space Centre inKourou, French Guiana. Its suborbitalballistic path will take it to a maximumaltitude of 830 km before bringing it backinto the atmosphere at 27 000 km/h.Atmospheric friction and a series ofparachutes will slow it down for arelatively soft landing in the PacificOcean, some 100 min after launch andthree-quarters of the way around theworld from its Kourou starting point.

The ARD is a heavily-instrumented testvehicle. During the flight, it will recordand transmit to the ground more than200 critical parameters for analysis of theflight and the behaviour of the onboardequipment. It is also planned to locatethe capsule after splashdown and, ifpossible, to retrieve it for return to Europeand a more detailed technical analysis.

What are the objectives ofthe ARD?The ARD will allow Europe to study thephysical environment to which futurespace transportation systems will beexposed when they reenter the Earth’s

The Atmospheric Reentry Demonstrator

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Further objectives are:– the assessment of the parachute and

recovery system,– the study of radio communications

during atmospheric reentry.

As a pilot project, the ARD isdemonstrating that Europe can develop acomplete space vehicle in a shorter timeand with a smaller budget than in thepast. Last, but not least, the ARD is also ahistoric flight for Europe.

Why is this flight historic?So far, Europe has built satellites for allpossible scientific, governmental andcommercial applications, and carriedthem into space on its Ariane launchers. Ithas also developed and operatedautomatic platforms (Eureca, Spas) and amanned laboratory (Spacelab). However,it relies on other partners to carry theseelements into space, deploy and retrievethem, and to return them safely to Earth.To date, only the US and Russia have fully

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Ariane-5 and other advanced spacetransportation systems have reached thelimits of what is achievable today usingclassical mechanical and power designs.Further improvements in payload-carryingcapability, accompanied by a significantreduction in launch costs, require a realquantum leap in the technical andoperational approach: instead ofdiscarding the launch vehicle, or at leastimportant parts of it, after each launch, itwill be recovered whole for reuse onfurther missions.

This will not be easy. The road to reusablespace transportation systems will bedifficult, but if Europe is to maintain theremarkable position it has achieved withthe Ariane launcher family, and if itintends to take up the challenges of thefuture launcher market, it has to masterthe reentry technologies that will play anincreasingly important role in the launchvehicles that are expected to come afterAriane-5.

Acquiring its own competence in thesekey technologies is also important ifEurope wants to become an appreciatedand respected partner in the possiblegovernmental and industrial cooperationstructures of the future for thedevelopment of such vehicles.

The Atmospheric Reentry Demonstrator isan important step for Europe in achievingthese strategic goals.

mastered the technical and operationalknow-how for both the ascent and returnphases of space vehicles.

With the flight of the ARD, Europe isundertaking a complete spaceflight cycle,from launch to landing, with its ownexpertise for the first time.

Why is the ARD importantfor Europe?Flight through the Earth’s atmosphereimposes an enormous stress on a spacevehicle. This is true in both directions:during ascent after launch, and duringreentry at the end of the mission. Thespeeds associated with spaceflight arevery high: at least 27 000 km/h isnecessary to achieve low Earth orbit.Space vehicles suffer considerablebuffeting and heating from theaerodynamic friction created by such highspeeds. Without the appropriateaerodynamic shape, robust mechanicalstructures, heat-resistant materials andintelligent automatic flight controlsystems, the vehicle would simply breakup and burn under the harsh conditions.

Reentry technology is not only importantfor space vehicles returning to Earth fromspace, but also for space transportationvehicles that carry payloads into space.These vehicles, or at least their lowerstages in the case of a multi-stage vehicle,generally fall back towards Earth aftercompleting their transport missions. TheAriane-5 core stage reenters theatmosphere at almost the same speed asa vehicle returning from low Earth orbit.Mastering reentry technology is not onlyimportant for guiding the upper stages ofexpendable launch vehicles into safetrajectories back to Earth, but it will beeven more important for the developmentof future space transportation systems.

Artist’s impression of the assembly of the ARD on Ariane-5’s Speltra in Kourou.

What is the overall designof the ARD?The ARD has an external diameter of2.80 m, an overall height of 2.04 m anda launch mass of 2800 kg. Roughlyspeaking, it looks like a 70%-scale Apollocapsule, with the remarkable differencethat it incorporates modern technologies.

The ARD has an air- and water-tightpressurised structure. In principle, it isdesigned to float by itself. However, afterlanding, two balloons will make sure thatit floats upright, with the heatshield fullyimmersed in the water. This positioncontributes to better thermal equilibriumand ensures that the Sarsat (satellitesearch and rescue) radio beacon andflashing light that guide the recovery shipare not immersed.

The ARD comprises four main elements:– a bulkhead structure that carries the

heatshield,

– a conical section that incorporates thereaction control system and houses aninternal secondary structure,

– a secondary structure inside the conicalpart to support the electricalequipment,

– a back cover to protect the descentand recovery systems during flight.

All structural elements are made ofmechanical-fastened aluminium alloyparts. The outer surface of the ARD iscovered with heat-protection material ofdifferent types.

What are the main systemfunctions of the ARD?Aerodynamics and automatic flightcontrolARD’s flight can be divided into threephases: ascent into orbit as a payload of

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based on Ariane-5’s performancecapabilities and on ballistic reentryparameters that could be representativefor a later Crew Transport Vehicle. As aresult, the ARD is a spheroidal-conicalcapsule very similar in shape to a NASAApollo capsule and, roughly speaking, a50%-scale model of what could be anoperational transportation vehicle capableof reentry.

The ARD’s automatic navigation, guidanceand control system consists of a GlobalPositioning System (GPS) receiver, aninertial navigation system, a computer,the associated data bus and powersupply and distribution system, and areaction control system. The reactioncontrol system is derived from Ariane-5’sattitude control system, using seven400 N thrusters drawing on hydrazine(N2H4) carried in two 58-litre tanks

Ariane-5; a free ballistic flight throughspace; and an aerodynamic, automaticallyguided flight through the atmosphere.

As soon as it reenters the atmosphere, theARD will become an aerodynamic vehiclethat automatically controls its flight pathwith the help of the onboard navigation,guidance and attitude control system. Itwill be like an aircraft in autopilot mode,with the substantial difference, however,that the ARD will be travelling athypersonic speed and, in place of controlsurfaces such as ailerons, elevators andrudders, it will use small rocket thrustersto change flight attitude.

To save time and money by avoiding theneed for a long aerothermodynamicselection process, an existingaerodynamic shape was adopted. Thedimensions and masses were defined

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ARD vehicle architecture.

ARD’s conical surface iscoated with thermalprotection consistingmainly of cork powderand phenolic resin.

pressurised by nitrogen. The thrusters arepositioned so that three provide control inpitch, two in roll and two in yaw.

One of ARD’s objectives is to validate theflight control algorithms that weredeveloped as part of the former Hermesspaceplane programme. The guidancealgorithm is similar to that used by NASA’sSpace Shuttle, based on a referencedeceleration profile and also used byApollo. This approach allows a good finalguidance accuracy with limited real-time

calculation complexity and storagerequirements. The accuracy is expected tobe 5 km, equivalent to kicking a goal witha football from a distance of 25 km. ESA’sinitial requirement for landing precisionwas ‘better than 100 km’.

In order to reach the target and to holddeceleration levels to 3.5 g and thermalflux within acceptable limits throughoutthe whole flight, the ARD will snake tothe left and right of the direct flight pathwith the help of the reaction controlsystem thrusters.

ARD’s controlled reentry phase will lastabout 15 minutes. The position andvelocity information required for theautomatic control system will becalculated during flight from theaccelerations measured by inertialnavigation system. During reentry, theARD will also activate a GPS receiverwhich is expected to indicate its positionand velocity with great precision.However, the GPS data will be added intothe control loop algorithms only if theyappear to be inside a ‘credibility window’defined by classical inertial navigation.

The GPS data will also be used toaugment the post-flight analysis of theactual flight path. In fact, theperformance of the automatic systemdepends on the quality of the guidance

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ARD’s heat shieldincludes four CeramicMatrix Composite testsamples; three arevisible here.

containing randomly oriented silica fibresimpregnated with phenolic resin. Thesetiles are arranged as one central tile andsix circumferential rings. ARD’s conicalsurface is coated with Norcoat 622-50FI,composed mainly of cork powder andphenolic resin. In addition to these‘classical’ materials, six samples of newmaterials are included: four CeramicMatrix Composite (CMC) tiles on the heatshield, and two flexible external insulationpanels on the conical surface. TheAleastrasil material has a very lowablation factor: it is expected that the

algorithms and the accuracy of thevelocity and position data. Comparisonwith the GPS information will distinguishbetween the dispersions arising from theinertial navigation systems and thosegenerated by the guidance function itself.

It is worth noting that, although GPSnavigation has become a massconsumption product today, theapplications where the user travels atmore than 27 000 km/h are few indeed.

Thermal protectionDuring reentry into the atmosphere, ARD’sheatshield will be exposed totemperatures ranging up to 2000ºC anda heat flux as high as 1000 kW/m2,resulting from the ionisation of thesurrounding atmosphere under theaerodynamic pressure of the hypersonicvehicle. On ARD’s conical area, thetemperatures could reach 1000ºC, with aheat flux of 90-125 kW/m2. Inside, thetemperature will not rise above 40ºC.

Most of ARD’s thermal protection elementsare based on materials already developedby Aerospatiale within French strategicdefence programmes. However, the flightwill also test a number of new-generationmaterials.

The 600 kg heatshield is composed of 93tiles made of Aleastrasil, a compound

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Thermal protectiontiles are applied to theARD heatshield atAerospatiale.

heatshield will lose only 0.5 mm of itsthickness during reentry. This has theadvantage that ARD’s aerodynamic shapecan be considered as constant, whichconsiderably helps the flight controlalgorithms.

Descent and recoveryThe descent and recovery system isdesigned to decelerate ARD beforesplashdown in order to limit the impactloads and to ensure flotation for up to 36 h. The system consists of a mortar forejecting the first extracting parachute,several staged parachutes, two balloonsto ensure upright flotation, and a Sarsatradio beacon to transmit ARD’s positionthrough a satellite system to the ARDMission Control Centre in Toulouse. TheARD is also equipped with a flashing lightto guide the recovery boat. That vesselcan also directly receive ARD’s Sarsat radiobeacon.

In order to avoid tearing the parachutes,the deployment sequence will not beginuntil the speed falls below Mach 0.8,probably around 14 km above the Pacific,depending on the actual atmosphericconditions (pressure, temperature,humidity) in the landing zone. Maximumdynamic pressure as the sequence beginsis 5500 Pa.

The 0.9 m-diameter extraction parachuteis ejected by a mortar from under theback cover on the ARD’s conical part. Thissmall parachute then extracts a 5.8 m-diameter drogue parachute, typically atan altitude of 13.5 km. The drogue ispartially folded (‘reefed’) to reduce its airresistance and unfolds to its full diameterin two steps. That is jettisoned 78 s laterat 6.0 km altitude, and a set of three

22.9 m-diameter main parachutes isreleased. They are also reefed and openfully in three steps in order to avoid over-stressing the system. They will slow thedescent rate to 6.8 m/s (20 km/h). Afterlanding, these parachutes are separatedand the two balloons inflate to ensureupright flotation. The descent andlanding system has been qualified at real-scale during a dedicated balloon droptest over the Mediterranean Sea.

Onboard measurement and telemetrySince the ARD is primarily a technologydemonstrator, it is important to obtain asmuch information as possible from theflight on the aerothermodynamic reentryenvironment, the behaviour of thethermal protection materials, theperformance of the navigation, guidanceand control hardware and software, and

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Principal stages in the mission of ARD

thrusters. They will be used mainly forqualifying the thermal protection material,but will also evaluate aerothermodynamicheat fluxes.

The pressure measurements will be madeon the outer surface (heatshield andconical section). Together with theassociated temperature measurementsand the reflectometer measurements,they will validate the aerothermodynamicpredictions on heat flux and pressuredistributions.

The accelerations and rotations measuredwith the help of the inertial navigationsystem and additional accelerometers willbe used to reconstitute the flighttrajectory, to identify the ARD’s

the functioning of the parachute andrecovery system.

Consequently, more than 200 differentparameters will be measured andrecorded during flight and transmitted tothe ground at up to 250 kbit/s. Theonboard measurement scheme covers121 temperature channels, 38 pressurechannels, 14 accelerometer and gyrochannels, 8 reflectometer channels, 5force measurement channels, 1 acousticchannel and a number of functionalparameters such as mission sequences.

The temperature measurements willrecord the temperature history within theclassical and the new-technology thermalprotection materials on the heatshieldand the side cone, within the structureand in the reaction control system

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(continued on p14)

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L0: the flight begins with the liftoff of Ariane-5 from Kourou’s ELA-3 launch complex.

L0+2 min 21 s: altitude 70 km, Ariane’s twosolid-propellant boosters separate from thecore stage.

L0+3 min 13 s: altitude 115 km, Ariane’sfairing, which shields the payload fromaerodynamic pressure during flight throughthe dense layers of the atmosphere, separates.

L0+9 min 59 s: altitude 167 km, Ariane’score stage shuts down and separates from theupper stage which continues to carry theSPELTRA, the ARD and the second Ariane-5payload. The following phase is anunpowered ballistic flight (the upper stagefires only after releasing the ARD).

L0+12 min 2 s: altitude 218 km, in amanoeuvre called ‘largage en route’ (‘releaseon the fly’), Ariane’s upper stage releases theARD into a ballistic suborbital trajectory. Theupper stage, together with the SPELTRA andthe second payload, continues its flight into ageostationary transfer orbit.

L0+12 min 30 s: the ARD begins automaticflight control. Between altitudes of 357 kmand 636 km, the ARD will be within radiovisibility of the Ariane ground station inLibreville, Gabon, which will forward thetelemetry to the ARD Control Centre inToulouse. The Centre will only monitor theflight and receive telemetry, and will not sendany commands to the ARD.

L0+43 min 21 s: the ballistic arc culminatesat an apogee of 830 km above the IndianOcean over 78.50ºE/5.40ºS, south-east of theMaldives Islands and north-east of the Britishisland of Tchagos. When the ARD hasdescended to about 200 km altitude,telemetry will be received by the first ARIAaircraft. It will also be in contact with a TDRSsatellite.

L0+78 min: altitude 120 km, above thePacific Ocean, speed 7533 m/s (27 130 km/h),the ARD enters the atmosphere on a trajectoryangled 3º below the horizontal. This marks the

beginning of the aerodynamic flight phase. Inorder to reach the landing zone with 5 kmaccuracy and to keep the deceleration forcesand thermal fluxes within authorised limits,the ARD automatically curves either side of itsnominal flight path using its thrusters. At90 km altitude, the heating begins to becomesignificant. At 90-80 km altitude, the ARD isexpected to enter the radio blackout zone; at45 km, it emerges from the blackout. Thesecond ARIA aircraft is positioned to receivetelemetry from the moment the ARD endsblackout until it lands on the water.

L0+88 min 12 s: speed about 800 km/h(Mach 0.8), at an altitude of 14 km (the actualvalues depend on the atmospheric conditions)the automatic parachute deploymentsequence begins with the ejection of the smallextraction parachute. The drogue parachute isdeployed 500 m lower down. 78 s later, at analtitude of 6 km, the three main parachutesare released for a splashdown of <20 km/h.

L0+100 min: the ARD lands at134.0ºW/3.9ºN, south-east of Hawaii andnorth-east of the French Marquesa Islands.Two balloons inflate for stability. The analysisof the telemetry received and relayed toToulouse by the second ARIA aircraft and thesignals of the ARD Sarsat beacon will allow thecapsule’s location to be determined within1500 m. The recovery ship will stand off at asafe distance to avoid being hit by the ARD orits debris in case the guidance system fails andthe capsule breaks apart under the thermaland dynamic stresses. Having received thelanding coordinates from the ARD ControlCentre, the ship will approach within 100 m. Itwill then wait for 10 h before venturing anycloser. During this time, the water will cool thecapsule so that there is no risk of an explosionfrom the hydrazine remaining in the attitudecontrol system. A recovery team of divers andtechnical specialists will then secure the ARDin the water and lift it on board the ship. Thevessel will deliver it to Papeete (Tahiti) inFrench Polynesia, from where it will betransported by a commercial ship to Europeand returned to prime contractor Aerospatialein Saint-Médard-en-Jalles near Bordeaux inFrance for inspection and testing.

What is the ARD flight sequence?

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The ARD will be mounted on the top position of Ariane-5’s SPELTRA multiple payload carrierstructure, with the heatshield pointing in the direction of flight .

ARD integrated atAerospatiale, Bordeaux.

aerodynamic coefficients and to evaluatethe dynamic stability and robustness ofthe automatic guidance and controlsystem. The information from the GlobalPositioning System (GPS) receiver will beused in the post-flight analysis of theflight behaviour.

Some technology measurements will bemade on the parachute system, includingmonitoring all deployment phases with avideo camera, a tri-axial accelerometer,and a number of strain gauges on mainparachute lines.

One mission objective is to studycommunications possibilities duringreentry and, in particular, to make adetailed analysis of blackout phenomenaand their effect on radio links. Radioblackout is expected between 90 km and40 km altitude owing to the ionisation ofthe super-heated atmosphere around thevehicle from dynamic compression. As

soon as the ARD descends to 200 km itwill be in telemetry contact with two USAir Force aircraft. At the same time, theARD will be transmitting to NASA’sTracking & Data Relay Satellite (TDRS)system and will receive signals from GPSsatellites. The attenuation and blackoutphenomena affecting the aircraft, TDRSand GPS links will be carefully analysedafter the flight. This should help tosuggest ways of countering thephenomena. This was possible with theUS Space Shuttle, which manages tomaintain TDRS contact despite theionisation of the surrounding atmosphereHowever, the Shuttle reenters at only 2-3 g, compared with the ARD’s 3-3.5 g.

Does the ARD usetechnologies from otherprogrammes?Maximum use was made of existingtechnology and off-the shelf hardware inorder to keep the ARD’s developmentschedule short and the development costlow.

The attitude control system is derivedfrom the Ariane-5 system. The electricalsystem, the telemetry hardware, the test-rigs and some of the software also comefrom Ariane-5. The pyrotechnic gear, thethermal protection and the antennas stemfrom French defence programmes. Thebatteries are similar to those aboardSpot 4. The GPS receiver is derived fromthat carried by France’s Rafale fighteraircraft. Most of the know-how onhypersonic aerodynamics, advanced heatprotection systems and hypersonic flightalgorithms derive from the former Hermesspaceplane programme.

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impact velocity of <6.8 m/s and wasrecovered by boat. The whole descentphase lasted 924 s. The drop test wasperformed under the industrialresponsibility of Alenia, which made useof the services of the stratosphericballoon launch base of the Italian spaceagency (ASI) in Trapani, Sicily.

The same drop test model was later usedfor a water recovery test and trainingsession in the Pacific Ocean by a Frenchmilitary recovery ship.

What ground facilities willbe used?The ARD will be launched from theGuiana Space Centre in Kourou, FrenchGuiana. It will make use of the centre’susual ground preparation and controlfacilities.

During the ballistic flight phase, ARD’stelemetry will be received by a groundstation in Libreville, Gabon, belonging tothe Guiana Space Centre network. Thatstation will be within radio visibility whenthe capsule is between altitudes of357 km and 636 km.

How many ARD modelshave been built?In line with the climate of ‘faster, cheaper,better’, the classical approach of buildinga flight model and a number of models ofvarious degrees of fidelity for geometrical,electrical and other ground engineeringtests was abandoned in favour ofproducing the single ‘protoflight model’.This means, however, that an additionalARD flight model cannot easily be built byupgrading existing ground models toflight standards.

Has there been any testflight before the ARD’sflight on Ariane-5?In addition to the protoflight model, atest model for qualifying the parachuteand recovery system under actual flightconditions was built. This model wascarried by a stratospheric balloon to analtitude of 23 km. The capsule wasreleased and fell to 14.7 km, where theparachute sequence was automaticallyinitiated at a dynamic pressure of 5336 Pa(specification: 5500-5000 Pa) and a speedof Mach 0.75 (specification: M<0.8). Thecapsule landed safely on water with an

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Preparing to launchthe ARD test model ona stratospheric balloonfrom Trapani, Italy todemonstrate thedescent and recoverysystem. Inset: thesame capsule waslater used for arecovery test andtraining session offTahiti.

ARD 29-09-1998 17:18 Page 15

This test model demonstrated the descent andrecovery system in July 1996 after being releasedfrom a high-altitude balloon launched from Trapani,Italy.

During the reentry phase, as soon as theARD has descended to about 200 kmaltitude, it will transmit radio signals to aNASA TDRS satellite and to one of thetwo Advanced Range InstrumentationAircraft (ARIA) waiting in the reentry zone.

The ARIAs are special KC-135 aircraftequipped for receiving telemetry datafrom reentry vehicles. They are verysimilar in design to the Boeing B-707.They are operated by the US Air Forceand leased by ESA through NASA.Normally based at Edwards Air Force Basein California, they will operate for theARD mission out of Hawaii. One ARIA willposition itself to receive the telemetrybefore the ARD enters radiocommunication blackout, while thesecond will wait for it to emerge.

The information received by them will beforwarded from the ARIA control centre toNASA’s Goddard Space Flight Center nearWashington DC, which will relay them,together with the information receivedthrough the TDRS control centre, to theARD control centre in Europe.

The ARD control centre is located withinthe Toulouse Space Centre of the Frenchspace agency (CNES). It consists of theARD control room, the flight monitoringcentre and the sea recovery coordinationgroup, and will maintain close contactwith the Sarsat control centre, themeteorological centre and the recoveryship in the Pacific Ocean.

The recovery ship is a type RR 4000 tugand supply vessel of the French Navy,equipped for receiving ARD telemetry. It

will wait for the ARD near the Equator,south-east of Hawaii and north of theFrench Marquesa Islands. It will alsolaunch balloons to profile the atmosphereat the landing site. If the sea recovery issuccessful, the ARD will be returned toAerospatiale in Bordeaux for furtheranalysis.

What if the ARD cannot berecovered at sea?Should the parachute and recoverysystem fail or the sea recovery beunsuccessful, the mission will still beconsidered as a success provided that thetelemetry transmitted during descentyields extensive knowledge of the flightconditions and the behaviour andperformance of the flight control systemsand thermal protection materials.

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and there would be the risk of it breakingapart and its pieces beginning to meltbefore hitting the water. That is why therecovery ship will wait at a safe distanceuntil splashdown. This also means thattelevision pictures of the landing will notbe possible.

Is sea-landing an option forfuture operational reentryvehicles?Finding and recovering a relatively smallobject floating in the sea is an extremelydifficult and risky undertaking. This hasbeen demonstrated by early US spaceprogrammes and, more generally, by theextensive experience with shippingaccidents and military aircraft crews whocome down over water.

What if the ARD guidancesystem fails?The flight parameters have been chosenso that, even in the event of a totalmalfunction of the ARD, the capsule willdescend safely in the Pacific Ocean, farfrom any human settlement or maritimeroute. As it will be injected by Ariane-5into a suborbital ballistic trajectory, theARD cannot go into an orbit around theEarth. Even with no further action by itsautomatic guidance system, it would onlydescribe a three-quarter circle around theEarth and then fall back into the PacificOcean, very much like the core stage ofAriane-5 itself. However, without theproper orientation of its heatshield by theattitude control system and the limiting ofthe deceleration forces by active flightmanoeuvres, the ARD would not reach itslanding target with a precision of 5 km

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What is the total ARD cost?

The fixed-price contract with Aerospatiale for the development of the ARD was valuedat ECU 30 million. The modifications resulting from the Ariane-5 failure led toadditional expenditures of ECU 3.2 million.

The atmospheric drop-test cost ECU 1.8 million. The ARD ground segment representsa value of ECU 4 million. Additional ECU 4 million are reserved for the detailedanalysis and evaluation of the results from the ARD flight, a task requiring about1 year.

In total, the whole ARD project, covering the flight segment, the ground segment, theevaluation of the flight, as well as additional activities, will cost about ECU 43 million.

It is very difficult to locate an object in anunstructured, moving environment,without any landmark or other visualclue. For the recovery itself, the mainproblem is that, if the landing on thewater takes place far from the coast,helicopters cannot reach the landingzone and fixed-winged aircraft cannotland on the water.

It is therefore mandatory to pre-positionone or more ships in the target area.Additional ships are required in order toallow for an accidental landing outside ofthe nominal area. In the case of amanned vehicle, it is important to reachthe landing point rapidly, since the crewcannot tolerate rough seas for very long.The Apollo programme showed that suchrecovery operations require considerablenaval forces.

Securing the vehicle in the water andlifting it aboard a recovery ship under allpossible weather conditions is anadditional challenge. It requiresexperienced and courageous specialistswho often put their lives at risk.

Water landing is therefore chosen only ifthe otherwise preferred landing on solidground is not feasible because oftechnical or safety reasons.

For the ARD, a water landing wasselected because, as a prototype vehicle,it is not certified to reenter theatmosphere and land over populatedareas.

What are the applicationsand future evolution of theARD?The ability to reenter safely, fly throughthe atmosphere and perform a precisionlanding is the prerequisite for thedevelopment of any space vehicle thatreturns to the ground, be it anunmanned launch vehicle or a mannedspacecraft.

The experience gained with the ARD willtherefore benefit Europe’s future launcherprogrammes after Ariane-5, such asFESTIP (Future European SpaceTransportation Investigation Programme),and the cooperation with NASA on the X-38 programme. The X-38 is anexperimental vehicle designed to validatethe technologies for a Crew ReturnVehicle for the International SpaceStation, capable of carrying astronautsback to Earth in an emergency. TheEuropean share in the X-38 is primarilyconcentrating on aerodynamics, hotstructures and fuselage structure, controlsurface systems, landing gear and otheressential hardware and software items.

In a broader sense, there are alsosynergetic effects of the ARD withscientific research vehicles that are able toenter the atmosphere of other planets ormoons. For example, ESA’s HuygensProbe, delivered by the Cassini Orbiter,will land on Titan, Saturn’s largest moon,in 2004. The Huygens entry vehicle wasdeveloped and manufactured by thesame industrial prime contractor as theARD: Aerospatiale in Bordeaux.

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On the Agency side, a lean in-housemanagement structure was adopted,delegating as much responsibility aspossible to industry. A joint project teamwas set up in Toulouse, composed of ESAand CNES engineers who had alreadyworked on the Hermes spaceplaneprogramme and its follow-up programme,the Manned Space TransportationProgramme.

This approach resulted in a record-breaking development time of only 24months, within a budget envelope ofroughly ECU 11 000/kg for ARD flighthardware. Comparable satelliteprogrammes have traditionally requiredsubstantially longer development timesusing budgets typically withinECU 100 000-1 000 000/kg for flighthardware.

It is also worth noting that thekilogramme price of the ARD is evenlower than the transportation cost of thelaunch vehicle itself. (Ariane-5 costs aboutECU 20 000/kg transported into orbit).

Is the ARD Europe’sresponse to the call for‘Better, Faster, Cheaper’?The ARD was not only seen by theEuropean Space Agency as a technologydemonstrator, but also as a managementdemonstrator to show that Europe cantake up the challenge of ‘Better, Faster,Cheaper’. Its development was thuscontracted by ESA to Aerospatiale as afixed-price contract, with less rigidtechnical requirements and a largerfreedom for the selection ofsubcontractors than usual in the past.

Aerospatiale had already gained asubstantial knowledge of reentrytechnology through its involvement in theformer ESA/CNES Hermes spaceplaneprogramme and in French strategicmissile programmes. Furthermore, inorder to keep development time shortand development cost low, Aerospatialewas requested to make use of existingand flight-qualified equipment whereverpossible.

Which industrial companies have been involved?

Under the lead of Aerospatiale’s Space and Defense Division, located at Saint-Médard-en-Jalles near Bordeaux,France, 27 European and US companies participated in the realisation of the ARD. The major contractors andtheir areas of technical responsibility are:

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• Aerospatiale (France) as prime contractorwas responsible for vehicle layout;thermal protection; architecture andvalidation of the guidance andnavigation system; onboard and groundsegment software; assembly, integrationand testing; antennas.

• Alenia (Italy) together with Irvin in Italyand USA was responsible for the descentand landing system, i.e. the parachutesystem and the flotation equipment,including the balloon drop-test inTrapani (Sicily). Alenia was also in chargeof thermal control and participated inthe in-flight measurements.

• Daimler-Benz Aerospace (Germany) wasresponsible for the reaction controlsystem.

• ETCA (Belgium) developed the functionalcontrol bench.

• Matra Marconi Space (France) wasresponsible for the functional electronics.

• SABCA and SONACA in Belgiumdeveloped the structure.

• TRASYS (Belgium) was involved insoftware development.

Further subcontracts involved SextantAvionique, Intertechnique and Onera inFrance, ABT and ETCA in Belgium, Saab inSweden, Alcatel in Denmark and Crisa inSpain.

The industrial set-up resulted in a workshare of approximately 50% of the totalcontract value of ECU 30 million for Frenchcompanies, 20% for companies in Belgium,15% in Germany and 15% in Italy.

About 200 people across Europe wereinvolved in the development of the ARD.

What are the milestones ofthe ARD project?The Procurement Proposal for the ARDwas submitted to the Industrial PolicyCommittee of ESA in January 1994. The3-month Feasibility Study was completedin April 1994. It was followed by a 5-month Preliminary Design Phase forwhich the formal contractual kick-off withAerospatiale took place on 6 July 1994.This phase was completed by aPreliminary Design Review in September1994.

The Development Contract withAerospatiale was signed on 30 September1994. A Detailed Design Phase startedimmediately and was completed by aCritical Design Review in March 1995.

The development of equipment andelements lasted until December 1995.Integration and testing took placebetween November 1995 and September1996.

Unfortunately, the failure of the firstAriane-5 flight in June 1996 not onlyproduced a substantial delay of thesecond Ariane-5, for which the ARD wasoriginally planned, but also the decision

to launch the capsule with its particularlaunch and separation sequence (‘largageen route’) only on the third Ariane-5.Consequently, the ARD was placed instorage at Aerospatiale.

The findings of the Ariane-5 failurecommission led to a number of ARDmodifications, since the capsule hadadopted existing Ariane-5 hardware, inparticular the inertial navigation system.With the changes made, the QualificationReview of the ARD was successfullyconducted in March 1997.

The drop test from a stratospheric balloontook place in Trapani (Sicily) on 14 July1996.

After the formal reconfirmation of theARD on the third Ariane-5 flight, and thedefinition of the launch campaignschedule for this flight, the FinalAcceptance Review for the ARD wasconducted at Aerospatiale in Saint-Médard-en-Jalles on 11 May 1998. Thefollowing day, the ARD was officiallyhanded over to ESA and then shipped toKourou, where it arrived on 15 June1998, ready for the launch campaign.

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BR-138 (ISBN 92-9092-613-9)

Text: D. Isakeit, Ph. Watillon, A. Wilson (ESA);C. Cazaux (CNES);G.Bréard, T. Leveugle (Aerospatiale)

Editor: A. WilsonPhotos: ESA, Aerospatiale, DASAArtist’s views: D. DucrosDesign: C. Haakman, A. Wilson

Price: 15 Dutch Guilders

© European Space Agency

ARD 29-09-1998 17:02 Page 2