Tatsuaki Okada

It is expected for wire-sawing to keep cutting performance by successive supply of cutting edges. The performance of wire-sawing in vacuum has been investigated for lunar and planetary explorations. In this report, cutting power was measured in vacuum. An octagonal load cell with strain gauges was mounted under the workpiece holder to measure the principal and normal forces simultaneously. The normal force was applied with a constant load spring. The wire speed was varied from 0.3 to 1.0 m/s. The principal force in vacuum was slightly larger than that in air and was constant in the measured range. Consequently, the cutting power was proportional to the wire speed.

It is expected for wire-sawing to keep cutting performance due to successive supply of cutting edges in vacuum. Because the nickel bond of the saw wire is softer than basalt, the nickel was shaved and adhered onto basalt. The diamond grits on the saw wire slips on it. Although the machining amount was decreased with a decrease of the vacuum pressure, the tool wear of both bare and nickel-coated saw wires was almost constant. Consequently, the grinding ratio, which is the ratio of the machining amount to the wear, was small at high vacuum. The dispersion of carbon from diamond into nickel caused the tool wear.

The JAXA Hayabusa-II mission is the follow-up to the original Hayabusa mission launched in 2003 \ which succeeded in returning the first dust particles from a near-Earth asteroid to Earth. JAXA intends to launch Hayabusa-II in 2014 for similar measurements of the asteroid 1999 JU3, a C-type asteroid, and invited the German Aerospace Centre (DLR) to contribute a small lander package to the mission. Based on this invitation, DLR is developing the Mobile Asteroid Surface Scout (MASCOT) to complement the main spacecraft's scientific objectives, with the Centre National d'Etudes Spatiales (CNES) providing payload and subsystem support. MASCOT will provide in-situ surface science and allow investigation of up to three sites on the asteroid surface. A short on-asteroid lifetime of two complete asteroid rotations (-16 hours) will provide measurements under different illuminations and thermal conditions, with Hayabusa-II being used to transmit all of the scientific data back to Earth. The harsh landing environment and strict mission requirements lead to some difficult design challenges. An innovative "hopping" mechanism will allow MASCOT to leap across the asteroid surface in bounds of up to 220m, albeit robustness of this concept must first be proven in a comprehensive suite of simulations and tests. Mass, limited to 10 kg, is critical: savings via the use of a carbon-fibre main structure and simplified subsystems allows the carriage of four scientific payloads, namely a multispectral wide angle camera, a radiometer, a magnetometer and an IR microscope. Thermal control is a challenge given the contrasting requirements of deep-space cruise and on- surface operation. Available energy also puts a strict limit on operations and restricts the lifetime of the mission. Copyright © (2012) by the International Astronautical Federation.

In future lunar, planetary or asteroid explorations, in-situ analysis of rock samples are strongly demanded to obtain many data from various aspects. For precise composition analysis, a sample surface should be smoothed. In this report, a surface shaver with a piezoelectric actuator is proposed and its machining performance in air is investigated. Shaving teeth are mounted at the ends of a lever mechanism. The device is pressed through four springs onto the specimen with a linear actuator. When a sinusoidal voltage of 50 Vp-p and an offset voltage of 25 V ware applied, the natural frequency was 556 Hz and the unloaded amplitude of shaving teeth were 0.77 mmp-p. Basalt samples were machined for 10 minutes in air. The surface roughness was small with an increase of the pressing force. However, the removal amount was smaller with an increase of the pressing force further. The surface roughness varied widely not only due to removal amount but also due to pores.

This report deals with a rock-crasher embedded in the science integrated package for future lunar exploration. The crusher measures 59×60×129 mm and weighs 490 g. The generative impact force and consumption power were 150 N and 6 W at a voltage of 24 Vp-p and a driving frequency of 50 Hz device. A tool bit with pyramids driven with a solenoid was made from tungsten carbide. Hard basalt, granite and anorthosite were smoothed.

In the Hayabusa-2 pre-project, science case and onboard instruments are studied to conduct in situ observation at the surface of NEO 1999JU3, with a candidate 10kg class small lander. Science requirements, strawman payloads, and operation scenario will be briefly described at the meeting.