Asteroid of the Half-Month: 25143 Itokawa Part III

Of all the challenges found by the new Hayabusa space probe (and there were lots), none involved lugging giant instruments around the Solar System. The entire craft weighed just over 500 kg, and a quarter of that was propellants. Scientifically, the investigations aboard Hayabusa were sufficient, not bleeding-edge. Things like high-resolution telescopes were left on Earth, as they should. Instead, particles of 25143 Itokawa were taken to our giant instruments- a sample return mission. Such were the open questions left by the Galileo mission, NEAR, etc.

Hayabusa did not visit 4660 Nereus as first planned. That would have been nice, but a C-type body was left to Hayabusa 2. Itokawa is, rather, an S-type; a sample would settle the issue of ordinary chondrite meteorites and S-types in a way that Galileo and NEAR only inferred. We see lots of S-type asteroids in our telescopes- they’re the number one type in the inner Solar System. And we have plenty of ordinary chondrites that fall to Earth- again, they’re the most common. Yet S-types don’t look like OCs, but like stony-iron meteorites.

Itokawa flew past Earth in 2001. Telescopes around the globe got observing runs, if for no other reason to lower risks for Hayabusa operations. Jun 2004, as Hayabusa was in flight, Itokawa made its next Earth pass. It came within two million km, under half its 2001 range. This was part of the logic for Itokawa: an easy target, with a favorable, Earth-crossing orbit (“low ΔV”). Even if Hayabusa failed, mustering the astronomy world was an achievement.

Hayabusa did not fail, but got over 1500 particles from a known body. The craft’s (lightweight) instruments also rendered data (and knowledge) of the sampling site. We know how our samples fit into contexts- of Itokawa as one example of asteroid diversity, and the site as one example over Itokawa’s surface. Not some random outlier, from some random body.

Ground telescopes, flight probes, and sample examination combine in complementary ways. Let’s look at not just a space body, but the investigation process: Solar System science.

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Asteroid of the Half-Month: 25143 Itokawa Part II

Soichiro Honda (yes, that Honda) once got asked the secret of his success. He reportedly said ‘One word: lucky.’ During the rise of Honda and similar manufacturers, Japan was dismissed as a land of cheap knockoffs. That era is clearly done. Japan has done the world’s first asteroid sample return, Hayabusa, though luck (good and bad) was clearly part of its story.

Japan has long wanted asteroid materials. In Jun 1985, nearly two decades before the launch of Hayabusa, a sample return meeting1 was gathered. This itself was after NASA and the NSF led an oversubscribed, 1971 international conference2 on asteroid exploration. In that and the following years, Peak Oil and the embargos added even more urgency if not funding. Through Hayabusa, we found something even more enabling: water in space.

Quick recap: the Hayabusa mission launched in May 2003, reached asteroid 25143 Itokawa, and gathered a sample. It returned in Jun 2010, dropping a reentry pack.

But back to 1985. That year, a Japanese team was assembled to analyze sample returns. They devised a mission to 1943 Anteros and back. Its trajectory was “surprisingly but accidentally very closely identical to the orbit of Hayabusa.” However, given 1985 technology (like chemical rockets) the mission was far too big and heavy (Kawaguchi et al. 2006). But by 1994, the Clementine probe had tested miniaturization, in flight. Crude forms of electric propulsion were flying, and ion thrusters were about to (gradually) take over communications satellites (such as Japan’s own ETS-6). Before Clementine even disbanded, a new Japanese team had formed, to study electric rockets for Mars and Near-Earth Objects (NEOs). They moved fast (for space), publishing a paper the next year on electric-thrust sample return (Kawaguchi et al. 1995). That mission got approved by Apr 1996, the start of Japan’s next fiscal year.

You may be thinking ‘April 1996 approval to May 2003 launch? What took seven years?’

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AotHM: 25143 Itokawa Part I

If you’re reading this- in English, off the internet- odds are good you’re not Buddhist. But you are a driver, or you trust car owners. Drivers are in your community, your circle of friends, workplace, likely your household. And you’re all certainly eaters. We can thank the Japanese (later Taiwanese, Koreans, etc.) for cars and consumer electronics. Yet not large-scale rockets, airliners, and similar aerospace pursuits. Why not? What’s the difference?

We (as in Western, educated, industrialized, rich democracies) hold positive images of ‘Japanese things’. That phrase, for a long stretch of time, conjured thoughts of your Sony stereo, the Honda in the driveway (and not in the shop), maybe the Lexus you wish was in the driveway. In this same period, the Japanese image of ‘Made in America’ was of substandard quality, possibly including the Space Shuttle blowing up. And that Americans are fat. They do buy tickets to Hollywood blockbuster productions, though, and ride Boeing airliners if not Chevy pickups. Tacitly, Japan’s space efforts are substandard. Again, why?

Like most nations, Japan started with sounding rockets- small, suborbital launchers for atmospheric studies, the aurora and ionosphere, etc. Since these are smaller, cheaper vehicles, they’re appropriate and accessible to learn rocketry and space hardware and operations. (This is where Brazil is now.) They also resemble tactical missiles- the short-range weapons most armies, navies, etc. buy, which makes production rates high. Japan’s sounding rockets include the Lambda series. As in Western practice, Greek is built into academia and science.

If one tries larger and larger rocket classes, though, the curve doesn’t just taper off, it breaks…

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