Hayabusa - good luck, and goodbye

Damn. Looks like Japanese space engineering ingenuity is going to pay off this time. Hayabusa's almost home.

In 1970, the three astronauts of Apollo 13 were brought back with improvisation the like of which nobody thought could be pulled off in-flight. Today, nobody thinks of the flight as yet another space mission that failed to fulfill its mission objectives, even if that's technically true - as a space quote, "Houston, we've had a problem" probably stands second in fame only to Neil Armstrong's immortal "giant leap" remark. While the fact that no human lives are at stake this time might lessen the impact of the heroism, JAXA is compensating by resorting to far more extreme measures in saving crippled space hardware.

Mr. Hayabusa (according to the Planetary Society, in Japan, ships and the like are referred to as male) just celebrated its seventh anniversary in space. That's three years more than it should ever have been there, and the impact of running machinery at so much beyond the design lifetime shows. Things stopped going by the plan long ago, though. Hayabusa was supposed to pay only a quick visit to the asteroid Itokawa, named after a Japanese space pioneer, but a series of instrumentation issues, including problems with the sample collector and the mistargeting of the attached minilander, culminated in total loss of communication in late 2005.

It took one and a half months even to hear from Hayabusa again, and three to speak with it again properly. By then, it had drifted well away from its asteroid outpost. Even though the sample collection system hadn't cooperated, optimism that some asteroid dust had been gathered in the capsule led the controllers to decide to try and conclude the mission as originally intended, by bringing the capsule back to Earth - only three years later than intended, as it was already too late to embark for the return trip on that orbit.

The trip back to Earth has been an eventful voyage. When Hayabusa left Earth, it had four ion engines to propel itself. Starting the return journey, it was down to two. Right now, all Hayabusa has left to change its trajectory is two half engines whose parts have been rigged together to work as one that is lousy but should just be good enough. The power system is old and damaged, requiring an extra maneuver to warm up the capsule with sunlight before its release. And did I mention the hydrazine fuel that is supposed to be burnt to turn the spacecraft in the right direction and perform the crucial final maneuvers? Well, every bit of it is gone. The maneuvers are instead done with the much weaker improvised ion engine, and for attitude control Hayabusa struggles with the said engine, combined with its final working reaction wheel and by using its solar panels as improvised solar sails to keep it under control. For perspective, another Japanese spacecraft is going to launch any day now to deploy the first experimental solar sail - that's just how cutting edge the technique is.

As I write this, Hayabusa is travelling towards Earth 10 million or so kilometers away, getting closer and speeding up (as the Earth's gravitation pulls it) day by day. Compared to the distance it has travelled, that's just in the neighborhood, and almost in the right direction. "Almost" meaning that at the current trajectory, it would miss the Earth by about 200 km. Only a few days before the June 13 touchdown in Australia, a final nudge should fine-tune the course to the landing site.

Which brings me to the two points of writing now, rather than in late June when the mission is hopefully succesfully completed. Firstly, there is still a definite chance of failure, and I want to grab the opportunity to congratulate the Hayabusa mission control of the amazing feats have managed - for having it to "go up in a hurtling piece of machinery and pull it back at the last yawning moment", however remotely. More importantly though, it's still possible to say goodbyes. For the crippled Hayabusa mothership, too weak to turn away after releasing the protected capsule, will perform its final act in finishing the delivery and burn up in the atmosphere of its home planet, joining the Apollo 13 lunar module as a piece of technology that was sacrificed to turn failure into success against all odds.