PERFORMANCE OF HYDROCARBON-FUELLED BOOSTER REPLACEMENTS FOR ARIANE 5

In this work, alternatives are considered to the current Ariane 5 configuration,  which adopts solid rocket boosters, based instead on hydrocarbon-fuelled strap-on boosters. Candidate fuels under investigation are liquid methane (LCH4) and kerosene; engines currently being studied at Avio S.p.A. are considered. The configuration of such boosters is determined for two reference cases: same payload mass in GTO (Geostationary Transfer Orbit), and same mass at lift-off as the current Ariane 5G launcher. The attendant advantage in terms of reduced lift-off mass, or increased payload, respectively, is quantified by means of a flight analysis tool. Particular attention is devoted to ensure that constraints on the flight path,  structural loads and booster attachment points are obeyed. It is found that both hydrocarbon fuels offers a remarkable payload advantage as compared to the current configuration based on solid  rocket boosters. An indicative cost analysis, based on available cost estimation relationships,  is used to shed light on the most convenient propellant combination. This suggests that, while LCH4 gives performance superior to kerosene, it also entails higher costs for expendable boosters, due to the more costly hardware required. However, the reverse may be the case if reusable strap-on boosters are envisaged, being refurbishment operations much cheaper as compared to kerosene-fuelled engines.