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.
A theoretical expression for the hysteresis loss in a transverse AC magnetic field with a large amplitude of trapezoidal wave form is derived for a bronze-processed Nb3Sn multifilamentary superconducting wire with a Nb barrier protecting Cu stabilizer from Sn diffusion. The present expression shows a quantitative agreement with our observed results over the whole range of the amplitude of the applied AC magnetic field up to near Hc2. It is to be emphasized that the values of pinning parameters adopted to estimate the values of hysteresis losses are the same as used in our previous paper to explain quantitatively the hysteresis losses when an AC magnetic field of a small amplitude is superposed to a DC bias magnetic field. Hence the hysteresis losses of a bronze-processed Nb3Sn multifilamentary superconducting wire with a Nb barrier can be described systematically over the whole range of the magnetic field by means of the modified Irie-Yamafuji model for the critical current density, if we take into account that the value of the critical current density contribut