The Planetary Society Blog
By Emily Lakdawalla
Hayabusa update: Return to Earth with only one thruster and one reaction wheel
Apr. 30, 2007 | 15:05 PDT | 22:05 UTC
Once again, the website JSpace has helpfully provided an English translation, from the original Japanese, of an update on the status of Hayabusa from science journalist Shin-ya Matsuura. The update was based upon a press conference held on April 24 on the status of Hayabusa's return voyage to Earth. The main piece of news on the engineering side is that Hayabusa -- already down to just one of three reaction wheels -- is also down to just one of four ion engine thrusters. Every time that it seems that the Hayabusa mission can't get any more difficult, it does.
The ion engine system includes four thrusters in total, lettered A through D. Thruster A has performed poorly since the beginning of the mission, and is not being used. Thruster B was found to be unstable during testing on April 20, so can no longer be used. Thruster C also shows unstable performance; it's not clear to me when that started. So only thruster D is available now for the return trip. Of the four thrusters, thruster D is the one that has been used the most, a total of 11,100 hours to date. The design lifetime for the thrusters is 14,000 hours, and the other three have become unstable long before this lifetime was reached.
This makes the return journey, which officially started on April 25, 2007 at 5:00 JST (08:00 UTC), even harder. To quote from the JSpace translation, "The intended plan was to operate two ion thrusters and a wheel when near to the Sun, and operate one ion engine without using a wheel far from the Sun. However, due to unstable performance of the B thruster, we decided to achieve the return mission by using one engine and a wheel continuously." Using only one thruster for the return trip will definitely send it long past its design lifetime. Thrusters have been tested on the ground to a limit of 20,000 hours, but no further; the return trip will definitely send thruster D over that. Things don't look good, but then they haven't looked good for Hayabusa for a long time, and yet the spacecraft continues to survive, and JAXA refuses to give up. Project Manager Jun'ichiro Kawaguchi is quoted as saying "precisely speaking, the [mission] status is 'not impossible to return.'" "Not impossible." Poor Hayabusa. But it's not dead yet -- let's all keep hope alive.
Comments
This comment form is powered by GentleSource Comment Script. It can be included in PHP or HTML files and allows visitors to leave comments on the website.
| 
