Lessons learnt from the Ariane Experience

Ing. Luca del MonteESA-HQ, Paris

Corso di Propulsione Aerospaziale

Universita’di Roma “La Sapienza”A.A. 2004-05

2Corso di Propulsione Aerospaziale

A.A. 2004-05

Risk Management has always been a key point for European Launchers.

• After the E.L.D.O. disaster (11 successive launch failures), the risk to develop a new European Launcher had to be minimised. New Means and Procedures for development have been set up.

• After Ariane 1 development, a production line had to be settled to minimise the risks of a new competitive launch service. Production risk management was experienced through the Ariane 4 programme.

• After the space commercialisation era, Europe has to adapt to the new international context, where development and production are integrated, but

where the most important risk is to loose its competences.

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Development risk management:

a. A launcher design depends upon disciplines (propulsion, guidance and control, structures etc) which need to be coherent: this is obtained through General Specification design rules established at System level.

b. A launcher development implies many actors who need to be coordinated through Management Rules accepted by every participant.

c. A launcher qualification is the result of a good Development Plan.

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General Specification design rules (1/3)

• They define the rules applicable for designing each element, subsystem or system related to the launcher.These rules include:

– The dimensioning trajectories.

– The aerodynamic conditions (Standard atmosphere, standard gusts and winds etc).

– The loads applied to dimension an external structure (Static, dynamic,Shocks acoustic noise etc).

– The margin design coefficients specific to the used technology.

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General Specification design rules (2/3)

• These rules are necessary to:– Guarantee an acceptable coherence between all subsystems.

– Allow data exchanges from the equipment designer to the system integrator.

• These rules have to be updated during all the development, and any deviation from them has to be justified and accepted by the launcher designer.

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General Specification design rules (3/3). Lessons learned from Ariane

• The General specifications used from Ariane 1, and updated with the new development programmes, are compulsory to design a coherent launcher.

• The modern informatics tools improve the efficiency of the general specification, if they remain simple and users friendly.

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System Design(1/2)

• Every design starts with a concept, then a system.The system is divided into parts for ease of study,understanding, and design. This must be done with a system focus back to the total product. When this step is completed by each part, the results are integrated back into a system.The real product integrity is established through the integration where the compartmentalization is merely a tool for helping achieve the integrity.

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Launcher designed by

9Corso di Propulsione Aerospaziale

A.A. 2004-05

Launcher designed by

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A.A. 2004-05

Launcher designed by

11Corso di Propulsione Aerospaziale

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System Design(2/2)

• System requirements are not only performance, but :– Development costs and schedule.

– Production costs.

– Operations and launch services costs.

– Reliability.

– Risk management

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System design optimisation

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A.A. 2004-05

System Design Ariane lessons learned (1/2)

• The Ariane development programme was conducted by a Prime (C.N.E.S.) who had a system design contract with industry (Aérospatiale). A constant dialog, enriched by some competitive studies resulted in an reinforced system optimisation which allowed to have the Ariane 1 to 4 first flights without failures.

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A.A. 2004-05

System Design Ariane lessons learned (2/2)

• The Ariane 5 first flight failure evidenced 3 main weaknesses:– The software developments become more and more integrated and are

generally on the critical path. Software reliability has to be improved by new methodologies (cross checking etc.)

– The System tests are mandatory because they integrate different disciplines (Guidance and Control simulation with hardware in the loop).

– Cost and planning overpressure and too much confidence before a flight qualification, lead to unacceptable risks.