At present, National Space Development Agency of Japan (NASDA) is moving ahead of the development tests of the cryogenic engine LE-5, and setting further about the development of the second-generation, high-performance rocket engine LE-7. Combination of liquid oxygen (LOX) and liquid hydrogen (LH2) was chosen as propellants through the technological experiences of LE-5, to minimize the total vehicle weight for certain launching capacity into geostationary orbit. The most critical point to realize this high-performance engine is in the high pressure level, especially the turbopump discharge pressure must be increased remarkably. This paper concentrates on LE-7 LH2 turbopump and introduce followings. 1) Required performance and Restraints for LH2 turbopump 2) Description of design 3) Technical problems
A bronze-processed Nb3Sn wire with a Nb barrier protecting Cu stabilizer from Sn diffusion contains a superconducting hollow cylindrical layer of Nb3Sn inside the barrier. Moreover a Nb3Sn superconducting layer in each filament is hollow cylindrical, too. In this paper the expressions for the magnetizations and hysteresis losses for this type of wire were derived in the case where a transverse AC magnetic field of trapezoidal wave form with a small amplitude was superposed to a DC bias magnetic field. The present expressions were compared with our experimental results and both of them agreed well with each other over a wide range of the DC bias field. The hysteresis losses of a Nb3Sn wire with a Nb barrier is mainly subjected to the magnetizations of a superconducting cylinder inside the Nb barrier, and amounts to several times larger than that with a Ta barrier. It is also pointed out that the values of critical current densities of superconducting barrier and superconducting filaments which contribute to the magnetization are usually different from that estimated from the critical current measurement by a resistive method, while the magnetic field dependences are nearly the same.