S. Schmidt et al./ Acta Astronautica 55(2004)409-420 Ta2W-%32 :日1:36.71 NIMONIC TEMP-SENXXR Fig. 14. Ceramic nozzle on test bench 4.2(left-hand side )and during the vacuum hot-firing test. CHAMIER NIMONI 3.3.3. Summary The use of nozzle extensions made of C/Sic for upper-stage engines was successfully demonstrated with respect to NO//L NIMONIC EXTENSION Mechanical loads during the transient start-up and shut-down phase Manner of functioning of the metal/ceramic inter face Manufacture of a tailor-made ceramic structure with adapted stiffening ring Design, manufacture and hot-firing test of full-scale nozzle components. Weight reduction(60% compared to metal nozzle) Fig. 15. 400 N engine(flight version) 3.4. 400n combustion chamber construction. Further advantages compris Combustion chambers for apogee-and attitude-control engines for satellites are currently made of refractory Simplification of the construction method by redt heavy metals such as rhenium, iridium and plat ing the individual components(single-piece con- inum. Due to the high stability to chemical attack struction), hence reduced test effort. and high service temperature of up to 1850 K, the Increase in the permissible wall temperatures ofcur- refractory metals are used as the material for com- rently 1900-2200 K (with suitable layer system), bustion chambers. Besides high material and man ence increase in specific impulse(performance) ufacturing costs as well as the substantial use of. Reduction of engine mass of 30-50% raw materials, heavy metals exhibit a high density, amounting to more than 21 g/cm" Fig 15 depicts the In order to study the use of fibre-composite ceramics current 400 N engine(flight version ). for small thrusters, in 1998 the first hot-firing tests The potential offered by CMCs as a structural ma- were carried out at sea level with different C/SiC terial for small thrusters lies among other things in the combustion chambers. The propellant compatibil learly lower manufacturing costs compared to metal ity(MMH/N2O4), diverse clamping concepts, andS. Schmidt et al. /Acta Astronautica 55 (2004) 409 – 420 417 Fig. 14. Ceramic nozzle on test bench 4.2 (left-hand side) and during the vacuum hot-3ring test. 3.3.3. Summary The use of nozzle extensions made of C/SiC for upper-stage engines was successfullydemonstrated with respect to: • Mechanical loads during the transient start-up and shut-down phase. • Manner of functioning of the metal/ceramic inter￾face. • Manufacture of a tailor-made ceramic structure with adapted sti;ening ring. • Design, manufacture and hot-3ring test of full-scale nozzle components. • Weight reduction (60% compared to metal nozzle). 3.4. 400 N combustion chamber Combustion chambers for apogee- and attitude-control engines for satellites are currentlymade of refractory heavymetals such as rhenium, iridium and plat￾inum. Due to the high stabilityto chemical attack and high service temperature of up to 1850 K, the refractorymetals are used as the material for com￾bustion chambers. Besides high material and man￾ufacturing costs as well as the substantial use of raw materials, heavymetals exhibit a high density, amounting to more than 21 g=cm 2 . Fig. 15 depicts the current 400 N engine (Oight version). The potential o;ered byCMCs as a structural ma￾terial for small thrusters lies among other things in the clearlylower manufacturing costs compared to metal Fig. 15. 400 N engine (Oight version). construction. Further advantages comprise: • Simpli3cation of the construction method byreduc￾ing the individual components (single-piece con￾struction), hence reduced test e;ort. • Increase in the permissible wall temperatures of cur￾rently 1900–2200 K (with suitable layer system), hence increase in speci3c impulse (performance). • Reduction of engine mass of 30–50%. In order to studythe use of 3bre-composite ceramics for small thrusters, in 1998 the 3rst hot-3ring tests were carried out at sea level with di;erent C/SiC combustion chambers. The propellant compatibil￾ity(MMH=N2O4), diverse clamping concepts, and