Ard

ARD is a European Space Agency program. The demonstrator was designed and built by a European industrial team with Aerospatiale as prime contractor.

Wednesday October 21, 1998, at 8:19 p.m. Paris time, the ARD capsule splashed down in the Pacific Ocean. Tracked during its descent phase under parachutes, it was immediately spotted by French Navy ships. The first European spacecraft to ever be successfully recovered, launched 1 hour, 41 minutes and 14 seconds before by Ariane 5, completed its sub-orbital flight followed by a perfect atmospheric reentry.

This demonstration of Europe's capacity to implement the guided and controlled re-entry of a space vehicle was European premier . It constitutes the first fundamental step towards the development of future European operational vehicles.

Flight data and first analyses of telemetry confirmed that ARD completely fulfilled its mission. With ARD, for the first time, Europe mastered the complete cycle of spaceflight from launch to splashdown and recovery. It therefore joins the major space nations in this area, since so far only the United States and Russia possess the required technologies. The success of the ARD flight is a historic first for Europe, which will open the pathway to the development of the launchers and space transport systems of the future. The scientific and technical data obtained are vital for the development of partially or entirely recoverable launch vehicles. They are also useful for designing spacecraft capable of reentering the atmosphere of other planets.

SHAPE: Spheroid-conical, like an Apollo capsule

DIMENSIONS: Diameter: 2.8 meters ; Length: 2 meters ; Mass: 2.8 metric tons

STRUCTURES: The ARD is composed of four main elements :

- a heat shield structure in light alloy supporting the thermal protections, - a conical structure in light alloy, housing the propulsion system and antennas, - a hexagonal central structure housing electronic equipment on three sides, and the parachutes and floatation balloons inside, - a jettisonable back cover.

THERMAL PROTECTIONS: The cone and the back cover are protected by Norcoat Cork panels (powdered cork and phenolic resin) with a 19 mm thickness. The heat shield is composed of 93 Aleastrasil tiles (silica cloth impregnated with phenolic resin) in 6 different forms, bonded to the metallic structure. Some of these tiles are equipped with sensors, making it possible to gather the necessary data for the aerothermodynamic characterization of the thermal protections. The heat shield also carried some thermal protection samples in the development stage. Norcoat Cork and Aleastrasil are both Aerospatiale-developed materials. They will maintain the internal temperature of the capsule at about 40°C, even during reentry through the dense layers of the atmosphere, when external temperatures reached 2000° C on the heat shield and 1000° C on the cone.

ATTITUDE CONTROL SYSTEM :

This system includes all the elements ensuring propulsion, attitude control and steering of the ARD during the ballistic and reentry phases. Seven 400 Newton hydrazine thrusters are used functioning in blow-down.

AVIONICS:

The avionics mainly is comprised of :

-an on-board computer (OBC)
- an inertial guidance system (SRI)
- a power supply system (BDP and batteries)
- a sequencing chain (ES/CDC)
- a redundant transmission chain
- a GPS
- two static recorders

SOFTWARE:

The capsule is completely automatic. On-board software manages navigation, guidance and control, and all mission sequencing.

DESCENT AND RECOVERY:

The descent and recovery subsystem ensured deceleration of the ARD before splash-down to limit the shock of impact. It also included the equipment to ensure that the capsule remained afloat in a vertical position, and provided the necessary information for signaling its position. It consists of :

- an extraction parachute (ų 1 meter)

- a stabilization and braking parachute (ų 5 meters) - a main 3-parachute canopy (ų 22m each) - two floater balloons - a SARSAT beacon - a video camera to record the opening of the parachutes.

June 4 1998 ARD leaves the port of Bordeaux aboard the Toucan for Kourou. It arrives on June 14th. Sunday, August 30, 1998 Beginning of the launch campaign.

Monday, September 28, 1998 Hydrazine tanks filled aboard ARD. Good health check.

Monday, October 5, 1998 Integration with the launcher

Sunday, October 11, 1998 The French Navy ships Le Revi and Le Prairial leave Papeete to go to the recovery zone with Aerospatiale and DASA teams aboard.

Friday, October 16, 1998 Dress rehearsal for the launch sequence in Kourou

Tuesday, October 20, 1998 - 11:00 a.m. The launcher is taken to its launch pad. The ships are in the recovery zone.

Wednesday, October 21 1998 - H0-6 hours Final functional check-out. H0 - 3 hours : the Aria aircraft take off for the reentry zone.

Wednesday, October 21, 1998 - 1:37 p.m. (Kourou time) Ariane 503 lift off.

Wednesday, October 21, 1998 - H 0 + 12 minutes ARD separation and positioning

Wednesday, October 21, 1998 - H + 17 minutes 36 seconds Reception of ARD telemetry in Libreville

Wednesday, October 21, 1998 - H0 + 1 hour 19 minutes 6 seconds ARD begins its atmospheric reentry

Wednesday, October 21, 1998 H0 + 1 hour 28 minutes Opening of parachutes at the predicted altitude of 14 km. Descent is visible from the tracking helicopter

Wednesday, October 21, 1998 - H0 + 1 hour 41 minutes 14 seconds Splashdown

Wednesday, October 21, 1998 - H + 1 hour 46 minutes 14 seconds End of ARD mission

Wednesday, October 21, 1998 - H0 + 4 hours The ships arrive near the capsule. Recovery operations are nominal. During the next few hours the capsule is made secure and its hydrazine tanks are emptied.

Friday, October 30, 1998 Arrival of the ships in Papeete. ARD is placed in a container.

Tuesday, January 19, 1999 After shipment via Marseilles, ARD returns to Aerospatiale's facilities in Aquitaine for expertise.

The data obtained from the ARD flight will validate mathmatical models and studies concerning many indispensable techniques and technologies required for the mastery of returning spacecraft from orbit.

- Accuracy and precision of aerothermodynamic models

- Good performance of the thermal protection system and materials

- Performance and robustness of the software for navigation, guidance and control. The precision sought at impact is between 5 and 10 Km, and deceleration should be limited to 3.5 g.

- The behavior of the parachute chain, and mastery of splash-down.

During the entire flight sequence more than 200 measurements of pressure, temperature, vibrations, etc. were taken simultaneously and transmitted to ground stations.

Main Flight Parameters:

EVENTS (Time from T0) PREDICITION (Time from T0) DATA MEASURED IN FLIGHT (Time from T0) Separation from Ariane 5 00h12mn00s 218 km 00h12mn00s 216 km Orbital Injection Semi-major axis : 6798.5 km Inclination : 5.753° Semi-mjor axis : 6802.4 km Inclination : 5.754° Beginning reentry (120 km) 1h18mn58s 4746s : 1h19mn6s Acceleration (max) 3.2 g 3.7g Angle of incidence 22° 20° Maximum roll attitude command 105° 110° Black-out Between 90 and 42 km altitude Between 89 and 43 altitude Lateral movement 68 km 67 km Parachute opening 1h28mn14s 14 km altitude 1h28mn00s 14 km altitude horizontal precision : 3 km Splashdown 1h42mn55s Vertical speed : 6.7 m/s Impact 7 g Precision (point of impact) : 5 km 1h41mn14s Vertical speed : 7 m/s Impact 7.1 g Precision (point of impact) : 4.9 km End of mission 1h47mn55s 1h46:mn14s

All of the flight data is available and is being analyzed. The measurements collected by the onboard sensors and the avionics data have been recorded and been transferred to computers for thorough analysis.

The first results show that after a perfect injection by Ariane 5, all on-board systems functioned nominally and according to predictions.

The navigation-guidance and control system functioned perfectly, adapting the deceleration of the capsule to compensate for a slight difference in longitude. Then it activated the opening of parachutes at the planned altitude, at a distance less than 3 km from the center of the target zone.

The nominal performance of the parachute chain was confirmed by the images filmed by the on-board camera, and the "soft" splashdown occurred under nominal conditions of acceleration and speed. Recovery and safety operations were accomplished as planned.

The coupling of the inertial guidance system and the GPS system, which was a world premier, made it possible to know the exact position of the capsule with excellent precision, and at all times. Measurements of the duration of the black-out phase demonstrated the validity of previsional models. Links with TDRS confirmed that it is indeed possible to maintain communications during this phase.

Lateral movements were nominal, with only a one kilometer difference from predictions. The thermal protections also were proved to be highly efficient, and are in a remarkable state after the flight.

All these early results confirm the that the initial design was sound and robust.

Flight data analyses will continue during the coming year, making it possible to improve mathematical and theoretical models, and our understanding of the phenomena encountered. ARD, whose objective was to validate simulation tools in flight, has demonstrated that Aerospatiale and its European partners are able, today, to master the all of the technologies associated with returning from orbit.

Aerospatiale Espace & Défense (France) Prime Contractor Over-all system architecture Thermomechanical architecture Avionics architecture and its validation Algorithms and software (ground and on-board) Assembly, Integration, and Test Thermal protections Telemetry system

Alenia (Italy) Thermal control, Parachute system Floatation system Sensors

Sabca (Belgium) Structures

Sonaca (Belgium) Structures

Alcatel/Etca (Belgium) Ground control bench

Trasys (Belgium) Software encoding

MMS (France) Functional electronics

Dasa (Germany) Attitude control system

References:

http://www.aeromatra.com/ep223x.html

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