Asteroid Ryugu Sample Collection: Feasibility Study and Innovation in Hydrogel-Based Capture

This study investigates the feasibility of in-orbit asteroid sample collection missions. While the paper explores the use of a capture device at the Liapunov orbit at L2, it primarily focuses on collecting small asteroid ejecta particles (1.1809-10mm). This raises the question of how to effectively collect larger particles using a hydrogel-based system, particularly at the Liapunov orbit. This paper explores this challenge and proposes a novel solution.

Reasons for Choosing Asteroid Ryugu

Please provide the reason for selecting asteroid Ryugu as the subject of this study.

Correction in Figure 1 Legend

The legend of Figure 1 on page six contains an error. β=8.02315 · 10−4 should be corrected to β=0.037297.

Distinguishing TDM1 and TDM2

What distinguishes the TDM1 and TDM2 positions, as discussed on page ten?

Impact Angle Range Discrepancy

In Figure 5 on page twelve, why is the impact angle range for Point Mass Restitution Coefficients greater than that for Rigid Body Restitution Coefficients?

Use of Liapunov Orbit

Why did the authors only use the Liapunov orbit among the nine types of orbits, as stated on page eighteen?

Enhancing Capture Probability

On page twenty, in the last line, 'However, since the orbit is much bigger, it can not be ensured that, when an ejecta is escaping, the spacecraft will be there and not in another tract of its path.' Suggestion: On page twenty, in Figure 12, two capture spacecraft can be placed at the two ends of the orbit to increase the capture probability and prevent the required particles from escaping.

Correcting Figure Reference

Additionally, it is known from Figure 3 that larger particles feature higher vej velocities, rather than Figure 3.1.

Innovation in Hydrogel Capture

The abstract of this paper states that the study evaluates the feasibility of in-orbit asteroid sample collection missions, but the size of the asteroid ejecta particles in the article is small (1.1809-10mm), and the size of the capture device is much smaller than the Liapunov orbit size at L2. Please provide a detailed introduction on how to use hydrogel for large-scale asteroid ejecta collection at the Liapunov orbit at L2, and emphasize the innovation of this paper, such as using the zero velocity surface for capturing asteroid ejecta. This paper introduces a novel approach for capturing larger ejecta particles at the Liapunov orbit using hydrogel. This approach utilizes the zero velocity surface to effectively capture these particles, significantly improving the feasibility of large-scale asteroid sample collection missions.