Japan To Launch Solar Sail Spacecraft "Ikaros"

separsons writes "On May 18th, Japan's Aerospace Exploration Agency (JAXA) will launch Ikaros, a fuel-free spacecraft that relies completely on solar power. The spacecraft's 46-foot-wide sails are thinner than a human hair and lined with thin-film solar panels. After a rocket brings the craft to space, mission controllers on the ground will steer Ikaros by adjusting the sails' angles, ensuring optimal radiation is hitting the solar cells. If the mission proves successful, the $16M spacecraft will be the first solar sail-powered craft to enter deep space."

Comments

Icarus?

[Kelson]

It's always seemed like a bad idea to name anything after a figure whose claim to fame was that he ignored warnings against exceeding the tolerances of his vehicle, causing it to break up and kill him.

Re:Icarus?

[Gerafix]

To be fair the Japanese don't have to do metric/imperial conversions so they should be fine.

Re:Icarus?

[srussia]

Talk about misnomer. This thing goes away from the Sun, not nearer it. Or maybe they meant post-wax-melt Icarus.

Re:Icarus?

[a whoabot]

Shouldn't your name be "SputnikPanik" then?

Re:Icarus?

[a whoabot]

That's possible, but I would doubt it. Greek words and names were usually transliterated by the Latins with "c" for Greek kappa (and "us" for cases with Greek second-declension masculine[omicron-sigma/"os"]). And this was done even after Etruscan had gone extinct. Maybe the tradition of transliterating as such came from the Etruscans, I don't know.

Re:Icarus?

[wienerschnizzel]

Reminds me of the shock I experienced when I found that one of the biggest brand of condoms in the US is called 'Trojan'. It can either refer to the people of Troy that got totally pwned or to the Trojan Horse from which the guys got out once they were inside...

Re:Icarus?

[radtea]

This thing goes away from the Sun, not nearer it.

Nope. Tilt the sail so there is thrust against the direction of orbital motion and the ship will fall inward toward the sun. Think of the spacecraft with the sail at 45 degrees to the radial direction ot the sun, so light is reflected along a tangent to orbit in the direction of motion.

So long as a solar sail craft is in orbit, it can either raise or lower its orbit more-or-less at will, although it is easier nearer the sun than further out. Once it is out of orbit, however, it can't ever return.

Re:Icarus?

[HiThere]

Not sure about that. I've seen claims that a lot of the thrust of a solar sail would be due to the solar wind...which would tend to stick, and thus couldn't be tacked against.

Also, solar cells tend to absorb photons, capturing their momentum, and when they re-radiate it (at a lower frequency) the direction is random.

If this is correct, then the simple model of solar sails tacking using reflected light is at least an oversimplification, and possibly so much of an oversimplification that it doesn't properly predict the effects.

Re:Icarus?

[Captain Nitpick]

Not sure about that. I've seen claims that a lot of the thrust of a solar sail would be due to the solar wind...which would tend to stick, and thus couldn't be tacked against.

Those claims are wrong. The force on a solar sail due to solar radiation pressure is about a thousand times that of the solar wind.

Also, solar cells tend to absorb photons, capturing their momentum, and when they re-radiate it (at a lower frequency) the direction is random.

The solar cells are going to be absorbing a small fraction of the incoming photons. If the sail is designed properly, the rest will be reflected in a controllable direction.

If this is correct, then the simple model of solar sails tacking using reflected light is at least an oversimplification, and possibly so much of an oversimplification that it doesn't properly predict the effects.

Your assumptions are wrong, and the model is correct.

MESSENGER has used its mostly reflective solar panels to make deliberate course changes. The basic physical principle is already proven, not just in the lab, but in space. JAXA is examining the practicality of building large solar sails, not whether they will work at all.

Thin sails

[Ricken]

The spacecraft's 46-foot-wide sails are thinner than a human hair and lined with thin-film solar panels.

Won't that easily break if something even touches it? (lots of space rock going a few km/s out there, or am i totally off?)

Re:Thin sails

[d1r3lnd]

Well yeah, but you could make it 100x thicker and all that debris whizzing around would still poke holes in it. This way, it's light enough to be a.) cheap to launch and b.) actually efficient enough at harnessing the solar "wind" to move its mass.

Re:Thin sails

[natehoy]

No, I suspect that's an expectation, but if the materials are built right it'll have some rip-stop capability so it'll just make a hole. That will affect the solar sail, but not significantly until you get a lot of them.

The alternative is to make something that is heavier and less effective, which will still get punctured if a bit of debris goes through it.

After all, things in space are usually not moving very slowly in relation to each other, so anything that touches it is likely to go right through anyway, regardless of the material. I suppose with something like this, the less resistance the material puts up the less its course is going to be screwed up by a space rock.

It's also relatively unlikely (though certainly not impossible) for them to have a strike in the first place. Look at how cluttered Low Earth Orbit is with Mankind's crap, and how many active satellites have ever been knocked out of commission by our own cesspool of concentrated garbage in LEO? Two that I recall, and they hit each other. I know there have been occasional stories about impacts, but they aren't terribly common, and the chances of them dwindle off rapidly past LEO and Mankind's junkyard.

Plus, $16 million?!? for a deep space probe that requires no fuel? That's chicken feed in terms of space travel. The Japanese could probably mass-produce them for $12 million a pop or less given economies of scale, send 10 of them out in different directions, lose 8 of them to debris strikes and whatever, and STILL get better science longer than pretty much anything short of nuclear we could send up today.

Re:Thin sails

[AikonMGB]

Yes, you are right -- micrometeoroid impacts are definitely an issue that you have to deal with when you are using thin-membrane materials in space. Hopefully the engineers will design features called "rip stops" (among other names) into the sail to prevent tears from spreading through the sail. These are usually accomplished by putting a grid of perforations throughout the sail -- when a tear encounters one, the circular shape spreads the tensile stresses across the adjacent material, reducing the likelihood that the tear will propagate. This way a micrometeoroid impact won't ruin your entire sail, just the local grid element.

There are probably other methods of implementing rip stops, but I haven't read any significant literature on them. Anything bigger than a micrometeoroid, and you have bigger problems -- but in this case, a traditional satellite would have just as big a problem.

Aikon-

Re:Thin sails

[SnarfQuest]

I believe that "Saran Wrap" is about this thin, but you still trust it to protect you from the mold growing on the leftover beans in your fridge. Thin doesn't mean it has to be extremely fragile.

Re:Thin sails

[yariv]

...harnessing the solar "wind" to move its mass.

I guess you didn't mean this, but just to avoid confusion. There is something called "solar wind", charged particles ejected from the sun, it has nothing to do with this sail. The sail uses light pressure, the pressure of light emitted by the sun.

meh

[jt418-93]

the bjorans did this centuries ago :)
repeat

Re:meh

[H0p313ss]

They call it science-FICTION for a reason. And this is Trek you're talking about.

Coolness Factor and Project Name

[decipher_saint]

Very cool project, I can't wait to see this baby in action!

That said, someone already mentioned the project vehicle name, but we all know it should have been Odin: Photon Sailer Starlight.

I suddenly feel very nerdy, much more so than normal.

Re:Coolness Factor and Project Name

[Yvan256]

I suddenly feel very nerdy, much more so than normal.

Are you suddenly speaking more fluently in Javascript or Klingon?

Preparation

[gmuslera]

In the case it or one of its successors are launched to another solar system, i suggest that it carry scaled down versions of the ninja turtles, so if some come back to this mote in god's eye will never figure how we really are.

Re:Where's it going?

[gyrogeerloose]

Anyone know where it's going? "Deep space" isn't much of an answer, as it includes everywhere that isn't Earth. Does it have a destination besides "away"? The article does not say...

As far as I can tell, it's an experiment to test the propulsion system with no other purpose. Here's a slightly better article about it.

Re:Where's it going?

[Fritz T. Coyote]

Earthquakes, Volcanoes, Climate Change, Wars, Plaques, vanishing bees and the possibility that George Lucas might make another movie? All of these are signs that the 4 Horseman are saddling up and getting ready for a ride.

So "away" is good enough for me.

Hopefully to a planet that was not colonized by the Golgafrincham B Ark.

Re:Solar power in deepspace

[drinkypoo]

A solar panel collects light and turns it into electricity. And solar panels are much thicker than a human hair.

A solar panel is anything flat and, in this context, photovoltaic. The part of a typical solar panel where the magic happens is much thinner than a human hair; it's the junction between two materials. The rest of it is just there to protect that part (and to enable its production during manufacturing, of course.) But since thin-film solar panels have been around for more than a little while, you have no excuse for not knowing about them and yet simultaneously "contributing" to this discussion. Thin-film panels are now cost-competitive with crystalline panels and are expected to eventually be much less expensive due to their reduced energy cost of manufacture. This also reduces the time to energy payback, which was around seven years with crystalline panels in the 1970s. (I have GOT to find my source on that again, must be in some old homedir someplace...) And in space, nothing non-structural has to hold up its own weight or survive winds (aside from the solar wind) so it can be as thin as will provide sufficient tensile strength. Like, say, a sheet of plastic.

A solar sail converts photon impact to momentum. Anything photons are absorbed or reflected by is a solar sail. A solar panel converts a portion of photon impact to electricity, trading photon velocity for electron velocity. These are not incompatible goals. As far as I understand, a reflective solar sail actually imparts more velocity than an absorptive one, but both work.

A Mote in Gods Eye

[monkaru]

This reminds me of the novel "A Mote in Gods Eye" by Larry Niven and Jerry Pournelle. Who knows, maybe one day we'll be that "mote". http://en.wikipedia.org/wiki/The_Mote_in_God's_Eye

Re:Solar power in deepspace

[SnarfQuest]

They have a flashlight mounted under the solar sail to provide the becessary light when they get too far from the sun. That's why they need the solar panels, to provide power to the flashlight when it's too dark for the sail to work otherwise, which also powers the solar cells.

Re:Where's it going?

[SnarfQuest]

With a name like "Ikaros", it's obviously going to have a parabolic flight path.

Re:What could possibly go wrong?

[RevWaldo]

Possible outcomes:

1) try > succeed > learn

2) try > fail > learn

Given the amazing low price tag for the mission, both are good outcomes.

Tachyon Eddy

[wisnoskij]

Now all we have to do is find a tachyon eddy and we could be on Cardasia in no time.

Is it just me or is Japan's space program awesome

[BetterSense]

I haven't really payed much attention to Japan's space program in the past...heck I didn't really know they had a space program. But they recently landed a probe on an asteroid, and returned it to earth with asteroid rocks. When I read that it was like, "Oh. Japan has a space program, and they actually did something scientifically interesting". It seems like space programs are all about bitching about government funding and endlessly redesigning ancient rocket designs and speculating about manned missions to other planets, and meanwhile Japan went to an asteroid and brought back rocks. So when they say they are going to make this solar sail thing, I believe that they are going to make this solar sail thing.

Inhabitat Articles

[BJ_Covert_Action]

This is a bit offtopic but it's becoming more prevalent and frustrating on slashdot. Is there a chance we could stop posting so many Inhabitat stories to slashdot? More often than not they aren't even stories so much as single paragraph posts that say, "Look at this really cool technology! Isn't it cool and, more importantly green?" They never even bother to go into a decent amount of technical detail about the really cool technology. Hell, in this case, the wikipedia article has more relevant technical details than the Inhabitat article. It's not like we put a post to slashdot every time a new wikipedia article on technology opens up. For that matter, if we are just posting links to websites about really cool technology, we could easily go digging through websites that are dedicated to the particular technology to get the really juicy bits of interest. For instance, when talking about Ikaros, why don't we try looking it up on one of the dozens of websites dedicated to cataloging spacecraft? Well that's not news is it? That's just cataloging interesting technology which, as far as I can tell, is all Inhabitat does.

I guess what I am getting at is that just because Inhabitat stumbled upon something cool they didn't know existed, it doesn't mean there is any news regarding that particular item. Now, if Ikaros launched recently, or if it's mission was underway, or if it was experiencing some technical difficulties, that would be something. The fact that the mission exists in the first place is neither a recent development nor particularly newsworthy. It seems like the firehose is getting clogged with Inhabitat submissions and frankly its starting to seem like slashvertising for the blog.

Re:Mythology FAIL (Re:Icarus?)

[the_humeister]

Daedalus flew too close to the sun, melted his wings, and died.

His father, Icarus, the creator of the wings, then landed and never flew again in mourning over his son, who's death Icarus was in part responsible for.

Mythology fail! Icarus flew too high and fell.

Re:Mythology FAIL (Re:Icarus?)

[Foobar of Borg]

Daedalus flew too close to the sun, melted his wings, and died.

His father, Icarus, the creator of the wings, then landed and never flew again in mourning over his son, who's death Icarus was in part responsible for.

Was that before or after Laius killed Oedipus and married Jocasta?