ARD (Atmospheric Reentry Demonstrator)

The ARD (Atmospheric Reentry Demonstrator) was an ESA program that developed an unmanned Apollo shape capsule that performed a sub-orbital atmospheric reentry for demostration of applied reentry technologies and atmospheric reentry data recording purposes. The project was part of the developmental work for a future european manned capsule. It was launched from Kourou, in the French Guiana, in 1998, onboard an Ariane 5 rocket, performing a succesfuly reentry from orbit and splashdown in the Pacific Ocean.

As part of the program, Aerospatiale subcontracted to Alenia Spazio the design of the Descent and Recovery Subsystem (DRS) that would allow the ARD capsule to perform a soft splashdown at the end of its atmospheric reentry and controlled flotation over the ocean. Before the actual rocket-borne test, the qualification of the whole integrated subsystem was performed by means of a high altitude drop test from a stratospheric balloon. This test was performed with a mock-up of the real capsule denominated Qualification Model (QM), which had the same scale, shape and mass properties of the real model.

The QM -which can be seen in a cut-away scheme at left- measured 0.279 meters of diameter, 2.037 meters of height and had a mass of 2800 kg. It was equipped with sensors and instrumention that monitored pressure, temperature, accelerations for attitude monitoring, cover separation, shocks due to parachutes opening and QM water impact. The whole electronic system including telemetry and telecommands devices were placed in waterproof boxes.

The Parachute Recovery Assembly consisted of three successive stages. First, a 1.07-meter flat ribbon pilot chute is mortar-ejected at 14 km; once inflated, it pulls out the capsule back-cover. Then, a 5.80-meter conical ribbon drogue chute decelerates and stabilizes the vehicle during 78 seconds and finally, a cluster of three 22.9-meter polyconical slotted main parachutes is opened.

Due to the intrinsec dynamic instability of the capsule during splash down, a special Stabilizer Device was attached to it. It consisted of a low drag axisymmetric body which was attached below the front shield by three vectran ropes and released just before the parachute sequence initiation. The system was developed by the French company SAER under Aerosptaiale specifications.

The nature of the project posed a series of challenges for the balloon launch infrastructure of the Italian Space Agency, which needed to built special hardware and develope special procedures for the test. The gondola used to lift the capsule was developed inhouse by ASI engineers. Also the large weight of the capsule, the payload, the flight chain and the balloon (corresponding to a total ascensional force of 5390 Kg) brought to design and then realize a special set up for the launching crane. This design, stable up to 7000 Kg, allowed to perform safely the capsule release from the vehicle in the worst conditions static and dynamic. Moreover, to avoid oscillations of the capsule flight chain has been projected with special simmetries and ballast has been released by an external guide.

Launching procedures have been also reviewed in order to guarantee security and reliability.

Two telemetries were on board: one, managed by Aerospatiale, was devoted to capsule and related experiments, and the other, under complete ASI responsability, to the management of housekeeping parameters such as temperature, pressure, trajectory, telecommands status and on board batteries. Housekeeping telemetry, connected to separation interface, allowed the management, under security constrains, of the numerous pyrotechnical devices located on board.

As the first part of the flight was to be performed over land, a series of security measures were established, in particular a parachute with a variable cross section (reefing) was designed for use both in the expected descent conditions (just gondola after payload separation) and in the case of a failure or mission abort conditions (gondola and payload together). A mobile telemetry station has been also developed to deal with eventual altitude loss by the balloon and consequent change of trajectory. In case of trouble the mobile station was ready on the ground to follow the balloon, send telecommands, receive and record data transmitted thus avoiding the risk of mission fail.

The test was performed in close coordination with aerial and marine Italian authorities.

Balloon launched on: 8/20/1995 at 8:00 local
Launch site: Base di Lancio Luigi Broglio, Trapani, Sicily, Italy  
Balloon launched by: Agenzia Spaziale Italiana (ASI)
Balloon manufacturer/size/composition: Zero Pressure Balloon  
End of flight (L for landing time, W for last contact, otherwise termination time): 8/20/1995 at ~18:00 local
Landing site: On the Jonic Sea between the citys of Catania and Syracuse, Sicily, Italy

The balloon was launched on August 20th, 1995 using the dynamic method assisted by launch vehicle.

After a nominal ascent phase, the balloon reached float altitude but soon started a descending phase taking an easterly direction, instead of continuing westward toward the sea.

It flew over Sicily slowly losing altitude and generating a lot of UFO reports. It was lost os sight in the late afternoon over the Jonian Sea.

The capsule was separated from the balloon and amerized in the sea in the east coast of the island and was recovered after an intensive night search using helicopters.

The unexpected balloon failure prevented to perform the drop test.

• Balloon Flight Test for ARD-DRS Qualification Environmental Testing for Space Programms, Proceedings of the Third International Symposium held 24-27 June, 1997 at ESTEC, Noordwijk, the Netherlands
• The Atmospheric Reentry Demonstrator ESA brochure