The beleaguered Hayabusa asteroid probe is back on track to return to Earth after a clever workaround coaxed one of its ion engines back to life.
The recovery is yet another reversal of fortune for the Japanese spacecraft, which has been plagued with problems since its visit to asteroid Itokawa in 2005.
It landed on the asteroid twice in November of that year, but its pellet gun – designed to dislodge material for collection – failed to fire. After an episode where it spun out of control and temporarily lost contact with Earth, engineers regained control and set it on a course back home.
Scientists are still eager to see the spacecraft return to Earth in case some loose asteroid bits accidentally made their way into the collection chamber during the landings.
But Hayabusa has been hobbling home without the full use of its four ion engines, which ionise xenon gas and then use electric fields to accelerate the ions, providing a steady – though weak – thrust.
One engine broke down shortly after launch and a second quit in 2007. When a third gave up the ghost on 4 November, it looked like Hayabusa would have too little power to ever get home.
Charge buildup
But the mission team has now cobbled together another working engine using parts from two sick ones, the Japan Aerospace Exploration Agency (JAXA) announced on Thursday.
One engine is still able to spit out positive ions for thrust, but can no longer squirt out negatively charged electrons, a step needed to prevent electric charge buildup on the spacecraft. The team got around this by spewing the required electrons from a second sick engine that retains this ability.
Now that Hayabusa in effect has two working ion engines again, it is back on track to return to Earth in June 2010, as had been planned before the 4 November glitch, JAXA says. If all goes well, it will drop its sample capsule in the Australian outback.
But Hayabusa project manager Jun'ichiro Kawaguchi of JAXA cautions that no one knows how long the cobbled-together engine will last. "This new configuration is very new to us and we are not sure ... how much we can count on [it]," he told New Scientist.
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Have your say
The Dawn space craft needs to be returned to the Earth as well. There is nothing scientific about abandoning explorer space probes into the void of space. A use-and-throw-away policy cannot be pursued with these sophisticated instruments made of precious metal.
Perhaps a smart maneuver can set the trajectory of the Dawn space craft back to Earth after visiting Ceres and Vesta. And there is also the Planck space craft and Herschel. Why do scientists think they can just use a space probe for a few years and then throw it away. In this regard the missions to repair and restore the functionality of the Hubble space telescope are historic.
I'm not so sure about the economics of recycling deep space probes but I am definitely of the opinion that equipment such as Planck, Herschel and Hubble should be designed for refueling by autonomous spacecraft such as that recently demonstrated by ESA, because in most cases it's running out of maneuvering fuel or cooling gas, rather than catastrophic electronics failures, that causes these expensive devices to become defunct.
All it needs is adaptation of the devices already used for in-flight refueling of aircraft; and I have already tried more than once through NS to push this for the refueling of communications and other satellites, to extend their lives and make them more cost-effective.
Come on, guys: it's not rocket science, is it?
It's not just the fuel that's an issue, micro-meteroid impacts also take a toll, constant repairs and replacements are required to keep a satellite operational.
It would be ridiculous to return the Dawn space craft needs to Earth. Even if it were possible there would be no way to slow it down without vaporizing it in the upper atmosphere.
It is many times more valuable in the asteroid belt anyway. If there is any propellant left over after visiting Ceres and Vesta I'm sure NASA will extend the mission and try sending on to another asteroid.
It is cheaper to send many one way probes than a single round trip one because the cost of launching the extra propellant needed to return would be far higher than the entire cost of a one way mission. That is why sample return missions are so rare, even though everyone salivates at the thought of them.
I can see a couple of reasons why you may want to return an old spacecraft:
1) Minimise space junk, which is a hazard for subsequent missions
2) To display it in a space museum
I see that:
1) We can crash obsolete spacecraft into the earth's atmosphere (for LEO=Low-Earth Orbiting spacecraft), into some uninhabited crater (for missions to planets and moons), or parked in known orbits, like the one near geosynchronous orbit. However, what makes spacecraft obsolete is often that they have run out of fuel, or become uncontrollable, both of which may render such a maneuvre impossible.
2) At present, we have no practical or safe way to return an intact spacecraft through earth's atmosphere.
Apart from LEOs, it may be best to leave an intact space probe in a known orbit - perhaps later it can be retrieved for some future museum in space, after something more powerful than chemical rockets is developed.
I work with the people who think about this every day, and if there were a way they would have found it. But you can't just send a "come home" call. If there isn't propellant and the planets aren't in the right places, it's impossible. But several great spacecraft *are* being used after their design missions are over - MER, MRO, Artemis, Stardust, Deep Impact, Cassini, etc. etc. This is the remarkable part.
Did you get the part about they are not sure how long the cobbled up fix will work? They would never attempt some ambitious journey like that with failing engines. It would be good if the entire craft could be retrieved to at least get a good picture of what went wrong with the ion engines. It sounds like a poor design, they should probably be using a VASIMIR kind of technology, one without grids. I get the feeling the grids shorted out or something like that. I have experience with that kind of ion engine, we use them here on earth in a machine called an Ion etcher, it is very close to the design of an ion engine and I know our design very well and know the grids are the weak point. The Vasimir is a type of ion drive more akin to a microwave oven in that the ions are accelerated with radio waves and not by electric charges on a grid. That kind of technology, using a grid with holes for ions to escape into space for propulsion is asking for trouble somewhere down the line. The Vasimir is a microwave oven with a bell shaped magnetic field so none or very few of the thruster ions actually touch anything leaving the engine so it is by design more reliable, now depending on the cleverness of the klystron or magnetron design, maybe daisy chaining some together, whatever it takes, to make the RF section live forever, at least for 20 or 30 years which is what it will take to get to the outer system or the first interstellar probes
Return Trip
Mon Nov 23 07:40:17 GMT 2009 by MaDeR
http://madcio.no-ip.org/index.php/Butterfly
"Why do scientists think they can just use a space probe for a few years and then throw it away."
Because it cost too much and have no purpose?
BTW please NewSciencist, delete spammers.
This comment breached our terms of use and has been removed.
Some excellent improvising by the engineers - well done!
McGyver in spaaaaace!
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