Friday, May 28, 2010

Sailing On A Star

Moon Princess Kaguya from "The Tale of the Bamboo Cutter's Daughter"

A week ago Friday, JAXA* launched an H-IIA missile from Tanegashima Space Center. On board were four small earth orbit satellites built by Japanese universities as well as the main attraction - Akatsuki, a craft which will carry out an extensive study of the atmosphere of Venus. Also on board was Ikaros, a "space yacht" built by JAXA which is testing the use of the sunshine for propulsion.

Here's the launch and separation of Akatsuki from the launch vehicle (2 min 46 seconds)

The next clip runs about 12 minutes and details (with English subtitles) the Akatsuki spacecraft and mission. It's quite impressive and if all goes well, will provide a wealth of information about the climate of Venus, which in turn may help us to better understand our own planet.

As a sailor, I was curious about the Ikaros mission. Particularly, how one could use sunlight to "tack" "upwind" in space to a planet closer to the Sun. Essentially, the sail is set so that the spacecraft's orbital velocity around the sun is slowed by the sunshine (photons). In other words, the sail is used as a brake, like when backing the jib on Bluesette. As the orbital velocity drops, the craft's orbit gets smaller - closer and closer to Venus. I found a website at Cal Tech with an excellent explanation of this - Tacking Solar Sails .

The Ikaros space craft (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) carries a sail that is just 0.0075mm thick wound around its core. Ikaros will spin at 20 rpm to unwind the sail using centrifugal force. When deployed, the square sail will measure 46 feet on a side. This clip is in Japanese, but you can get the (ahem) drift by watching the animation. There are thin film solar cells and dust counters attached to the sail. In addition to testing the sailing concept, the development of this craft and a much large one later on this decade, will lead to lower cost solar cells - an important element of Japan's efforts to reduce greenhouse gas emissions.

Fair winds Ikaros and Akatsuki.

Until next, sweet sailing.

*JAXA website is here: Japan Aerospace Exploration Agency


Doc Häagen-Dazs said...


Pandabonium said...

Doc - Just like sailing on Earth - no need for gas! I'm hoping for some terrestrial sailing this weekend.

Doc Häagen-Dazs said...

Done correctly, there should be no need for petro to sail on earth...

Don Snabulus said...


Can you drop me an email when you get a moment? Thanks.

Pandabonium said...

Doc - in a few years, we may not have a choice. ;^)

Don - done early today. I hope your email account doesn't put it in the spam file.

WV - "pnout" - a quick stop restroom service (p-n-out).