Space propulsion applications require the development of new ceramic matrix composites with a chemical and structural stability at ultra high temperature. Instead to limit the protection of a C/C composite to an outside coating made in UHTC (ultra high temperature ceramic), it is proposed to introduce UHTC materials as a matrix inside poorly densified C/C composites. Both powder impregnation (ZrB2, SiB4, SiC in various proportions) and liquid silicon-zirconium mixture infiltration enable manufacturing these UHTC based matrices in Cf/C preforms. The matrix is made of various proportions of ZrB2, SiC and ZrC. It is strongly bonded to the C/C matrix without degradation of this latter, due to the development of a limited reaction zone between the constituents. Also, samples present a high densification rate with less than 10 vol% open porosity. The oxidation behavior is evaluated on composites structures at temperatures higher than 2000°C up to 6 minutes, using an oxyacetylene torch. Chemical analyses and microstructural observations before and after oxidation testing are done to assess the protection ability of the ZrB2-SiC-ZrC matrices. A multi-oxides scale ensures the protection of the C/C composite, underneath, and oxidation progresses on a single and stable front in time. Thermal-cycling tests in such severe environmental conditions are finally carried out to evaluate the possibility to reuse these materials. Characterizations of in situ oxidation, under oxyacetylene torch, using synchrotron facilities are developed to go further in our investigations.