Interior of the retrieved capsule
There was no trace of burning seen inside the capsule, so my true first impression was that it was unexpectedly clean. There is no oxygen in space so there is no chance of oxidation, so it was no surprise that the inside of the capsule was undamaged. But still, I couldn’t help being surprised at how clean it was. As far as the heat shield was concerned, even though the front had scorch marks, the shield was intact and the entire surface had burned cleanly and evenly. I was also surprised at how much of the plastic tape that was applied on the heatshield stayed on, even though it was burned. This tape was attached to facilitate analysis - to study how hot the capsule had become after separation from HAYABUSA.
Likewise, I was deeply moved when I saw that the umbilical cable was still there, too. The cable connects the sample capsule and the spacecraft to supply electricity to the capsule’s heater and to transmit and receive information and commands. The cable was cut when the capsule separated from HAYABUSA, and then was enveloped in heat of over 10,000°C during re-entry, so I had expected that it would have melted away without a trace. However, to my great surprise, the cable was still there. I couldn’t believe it, and at the same time I thought it was a great memento of the HAYABUSA spacecraft.
Light streak in the sky created by HAYABUSA and the capsule (courtesy: Yutaka Iijima)
I think that the greatest achievement is the acquisition of technology that enables a round-trip flight. The technical objectives of HAYABUSA were 1) to conduct interplanetary flight with a new ion-engine propulsion system; 2) to perform autonomous navigation and guidance; 3) to collect samples from an asteroid; 4) to perform an Earth swingby using ion engines; and 5) to ensure the sample capsule’s re-entry.
Although the result of the sample collection is not yet clear, I think that HAYABUSA’s round-trip flight would not have been possible without the technologies developed for all five of these objectives. Focusing on just one objective, such as sample collection, is impossible - you can’t achieve it in isolation. Besides, these technologies are all essential for future sample return and round-trip flights, as well as resource utilization of other celestial bodies at greater distances. I think acquiring these technologies and being able to pass them on to the next generation is quite a striking achievement.
Aided by occasional strokes of luck, our project team never gave up until the end, and was is the team’s abilities that made the return of HAYABUSA possible.