X-37B launch with light sail succefully launches

[Borgholio]

So would it be possible to link several sails together with more sturdy connectors? Or would the required mass of the connectors eat up the advantage of the sail being larger? Is there, so to say, a known optimal size of a sail?

You could link I suppose, but that would greatly increase the complexity of the thing. So far as I know, there is no optimal size as far as propulsion goes. The limit is in how big it can be and still fit into a rocket.

[Simon_Jester]

The optimal size depends on what acceleration you want, and what material science you have to hold it together. It's not going to be a one-size-fits-all answer.

[Terralthra]

If you make sturdier connectors, that also increases the mass of the assembly, which reduces the overall acceleration (F=ma). Sooner or later, you'll hit diminishing returns to the point where adding more sail area actually decreases your acceleration.

[SpottedKitty]

You've also got to have the whole thing able to fold up small enough to fit under a launch shroud (if you're still talking about launching on conventional rockets). And don't forget light enough for your launch vehicle to lift it off the pad. All of these will of course have different limit points and "sweet spots" of high efficiency, so the whole thing is going to end up as a compromise. Which pretty much sums up the entire field of spacecraft design, a lot of it is a matter of duelling compromises.

[dragon]

Contact lost

A computer problem during the test flight of the Planetary Society’s LightSail spacecraft has left the prototype satellite unable to communicate with mission control, preventing (at least for now) the scheduled deployment of its solar sails to ensure that they work as planned.

What went wrong? According to Engadget and Popular Science, LightSail’s hardware launched with an older version of its Linux-based operating system, and as it turns out, this version of the OS shipped with a major glitch. It was to transmit a series of data packets back to Earth, sending detailed information about its position and other relevant data.

After the first two days, however, the transmissions went silent. The Planetary Society believes that with each packet it sent, it created a file too big for the software to handle, causing the OS to crash. Specifically, once its file reached 32 megabytes in size, the flight system locked up. While the issue was fixed in later versions of the OS, it persists on LightSail’s system.

Fixing the likely frozen LightSail

For the time being, the Planetary Society has put the spacecraft’s primary mission on hold so that they can deal with the software issue. They believe that the system is frozen, and while the flight control team has been attempting to send commands to LightSail in order to get it to reboot, thus far their attempts have been to no avail.

“The team is looking into other possible ways to reboot the system, but there’s also the chance that charged particles in space may strike an electrical component of the system and zap it awake (no, seriously),” Popular Science said. “If that happens, the Planetary Society won’t waste any time and will deploy the solar sail immediately, lest the software freeze again.”

In a blog entry posted earlier this week, the Planetary Society said that personnel at both the Cal Poly San Luis Obispo and Georgia Tech ground stations would continue to be on the lookout for the probe as it passed by. The Cal Poly team would be automating the reboot command so that it would be sent to Light Sail on every few ground station passes, with the hope that one of the commands would find its way to the spacecraft and fix the issue.

Mission control personnel are also reportedly evaluating a series of fixes that could allow them to work around software vulnerability, if and when contact is reestablished. One, they explained, is a Linux file redirect that would send the contents of the problematic file to a null location – “a sort-of software black hole,” they explained. Early tests using this technique have been called “promising,” the organization said.

Read more at http://www.redorbit.com/news/space/1113 ... Zzb6Y95.99

link

[LaCroix]

Aw, maaan...

If all fails, they should consider sending another satellite with a pointy stick up to push the reset button...

[Borgholio]

That sucks...they launch and only afterwards figure out there was a patch released for the software.

[dragon]

unless of course they are only saying it's lost, maybe it's on some secret mission after all it was launched by a secret military spaceplane

[SpottedKitty]

If all fails, they should consider sending another satellite with a pointy stick up to push the reset button...

It's surprising how many spacecraft glitches could be easily solved if only we could do exactly that. Think of the antenna problem on the Galileo Jupiter orbiter.

[orbitingpluto]

That news is a bit old, as they've regained contact on the 31st. Link to the Planetary Society blog about it.

[LaCroix]

I think I need to add "sponateous cosmic ray reboot" to my list of explanations for strange computer behavior. And when someone tells me that this is bullshit, I'll just show them this article...

[jwl]

I think I need to add "sponateous cosmic ray reboot" to my list of explanations for strange computer behavior. And when someone tells me that this is bullshit, I'll just show them this article...

Cosmic rays do cause computer errors, but not as badly on earth as in space because the atmosphere gets in the way.

[dragon]

That news is a bit old, as they've regained contact on the 31st. Link to the Planetary Society blog about it.

So what secret mission did it do during the missing time.

[LaCroix]

I think I need to add "sponateous cosmic ray reboot" to my list of explanations for strange computer behavior. And when someone tells me that this is bullshit, I'll just show them this article...

Cosmic rays do cause computer errors, but not as badly on earth as in space because the atmosphere gets in the way.

You know, I know - but the users may never know...

[Borgholio]

That news is a bit old, as they've regained contact on the 31st. Link to the Planetary Society blog about it.

Good to hear! I wonder if they can patch the OS from down here or if they're just going to try to work around it?

[orbitingpluto]

I don't know if they got the patch up, but they did deploy the solar panels today, important because power levels dropped rather low during the computer freeze. The solar sail might be deployed Friday, but that's counting on getting the batteries charged up, and no other problems occurring between now and then.

[Zeropoint]

If all fails, they should consider sending another satellite with a pointy stick up to push the reset button...

It's surprising how many spacecraft glitches could be easily solved if only we could do exactly that. Think of the antenna problem on the Galileo Jupiter orbiter.

http://freefall.purrsia.com/ff1000/fv00955.htm

[orbitingpluto]

I'm two day's late to this news, but apparently LightSail fell silent on the 4th, with a battery glitch suspected. Depending on what is causing it, it's the orbit will precess so that in the next few weeks, LightSail will receive near continuous sunlight during each orbit, hopefully doing something good for it's power situation.

[orbitingpluto]

LightSail makes contact after dropping silent for a second time, it's batteries charged enough to call home, but low enough to make it's ground team decide to not risk solar sail deployment for now. If it manages to charge up between now and it's when it contacts a ground station early on Sunday, it could deploy the sail around 2pm EDT that day. Why it wasn't charging is still under investigation though.

[orbitingpluto]

And the sail is deployed, with images coming tomorrow.

[SpottedKitty]

<fingers crossed>

[orbitingpluto]

They have a partial picture, here's the blog post, and here is the pic itself. According to the blog, they will have the full picture downloaded during a ground pass tomorrow morning, the partial one is scrambled and partly blank because they were unable to download all of it while the spacecraft was still in range.

[Borgholio]

Even that partial pic is pretty nifty though.

[orbitingpluto]

Over wings of silver, high in the heavens, that great engine which gives wind to it's sails is beheld. Spoken plainly, you can the Sun and one side of spacecraft in the picture linked to above, my apologies for indulging myself there.

According to the accompanying blog post, they will be getting a picture of the other side of the spacecraft tomorrow. That picture should have Earth in the background, so there's that to look forward to.

[InsaneTD]

That does look cool.