Acta Astronautica 64 (2009) 1015 – 1020 www.elsevier.com/locate/actaastro ELV: Pressure-fed LO x /LH 2 upper stage Max Calabro a , ∗ , Christophe Bonnal b , Aron Lenstch b a The Inner Arch, Villennes, France b Cnes DLA, Evry, France Received 15 February 2006; accepted 8 December 2008 Available online 24 March 2009 Abstract Cnes is leading extensive studies for the future generation of ELVs. The trend is today to research easy to use, robust and reliable solutions for the propulsion of future expendable launch vehicles but also with a high level of performances associated to as low as possible recurring cost of the launch vehicle. Among the different configurations (i.e. “linear”, linear with SRBs, tri stages, parallel with cross feeding) conventional two stage architecture seems the one of the best to reach these goals. In the two stage configuration, there is competition between SRB (500 ton of propellant), LO x /LH 2 (350ton of propellant) or even LO x /methane, but always the second stage is cryotechnic (LH 2 /LO x ), different technological solutions are possible. A way could be an extensive use of composite materials both for the structures, the tanks and the engines with use, as much as possible of automatic processes. In near future breakthrough or improvement of the fiber strength may increase the interest of such technologies. The aim of this paper is to present the technical choices for 40ton of propellant second stage leading to cost effective configuration. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction Cnes is leading extensive studies for the future gener- ation of ELVs. The trend is today to research easy to use, robust and reliable solutions for the propulsion of fu- ture expendable launch vehicles but also with high level of performances associated to as low as possible recur- ring cost of the launch vehicle. Among the different configurations (i.e. “linear”, linear with SRBs, tri stages, parallel with cross feeding) conventional two stage ar- chitecture seems the one of the best to reach these goals. In the two stage configuration, there is competition ∗ Corresponding author. E-mail addresses: max-calabro@wanadoo.fr, max.calabro@freesurf.fr (M. Calabro). 0094-5765/$ - see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.actaastro.2008.12.011 between SRB (500 ton of propellant), LO x /LH 2 (350ton of propellant) or even LO x /methane, but al- ways the second stage is cryotechnic (LH 2 /LO x ), different technological solutions are possible [4,5]. A way could be an extensive use of composite mate- rials both for the structures, the tanks and the engines with use, as much as possible of automatic processes. In a near future a breakthrough or improvement of the fibers strength may increase the interest of such tech- nologies. The aim of this paper is to present the technical choices for a 40 ton of propellant second stage lead- ing to a very effective configuration. In a near future a breakthrough or improvement of the fibers strength may increase the interest of such technologies. Liquid composite wound tanks can weigh three to four times less than a metallic one under the same