Philae Found
esa.int
esa.int
The description of the documentary says [1]:
> Unable to carry enough fuel owing to weight restrictions, the Rosetta scientists devised a delicate cat and mouse trajectory to reach their distant destination. In the ten years Rosetta had been in space she flew around the Earth three times, Mars once and the asteroid belt twice, to gain the momentum she needed to reach her destination. In the months before landing, the team navigated Rosetta safely to a world never before observed at such distances or accuracy. Rosetta orbited the comet before releasing Philae onto the surface.
Quoting from the article of this thread:
> “We were beginning to think that Philae would remain lost forever. It is incredible we have captured this at the final hour.”
This brings a much better ending for the people who worked on the mission for more than 30 years. [1] We tend to anthropomorphize things like spacecrafts, landers, rovers and many other inanimate objects. I think for the team (and many others following this news), this photo would be like being able to see a dear friend one last time, say goodbye in their minds and have some kind of closure.
The Wikipedia article, and especially the section titled "Landing and surface operations" [2], is also quite interesting to read.
[1]: http://www.pbs.org/program/catch-comet/
[2]: https://en.wikipedia.org/wiki/Philae_(spacecraft)#Landing_an...
Focusing on a point solution like "propulsion" is not even the right kind of question to answer "why not solve this problem with humans?".
These are all a lot easier if you are not worried about mass anymore. Just give all your structures a 3x safety factor like a bridge, and bring extras of anything complicated. Heck bring a mechanic and tools, too.
Of course this is all fantasy, which was the point of this subthread under kordless, in the first place.
EDIT
> Focusing on a point solution like "propulsion" is not even the right kind of question to answer "why not solve this problem with humans?".
To be more clear: I agree with you. I'm just playing the idea of "what if we had much better propulsion." But of course we don't, so in real life, we do need to carefully consider the factors you mention.
You could say the same thing about safety, and the need for return.
Nuclear thermal, and nuclear/solar electric (aka ion) rockets achieve better specific impulse despite carrying separate weight for power. Some nuclear designs (e.g. Orion as johncolanduoni said) do have overlap between reaction mass and energy source mass. Solar sails, ground lasers, and gravity assists avoid some of the need for carrying reaction mass. All these are perfectly newtonian.
Chemical does win among currently working designs at accelerating quickly, which is critical for human exploration, and to some degree for getting to orbit. There is no inherent physical reason alternatives can't achieve that.
I must recommend the extremely fun Project Rho site though I'm just started reading it: http://www.projectrho.com/public_html/rocket/enginelist.php It's not always clear where existing science ends and Sci-Fi begins, but that's generally on technology barriers (e.g. we haven't yet managed break-even contained fusion), not mythical "entirely new understanding of physics". And the amount of actual science — detailed papers, prototypes etc — on diverse and bizzare drive designs is way more than I expected!
> “This [...] means that we now have the missing ‘ground-truth’ information needed to put Philae’s three days of science into proper context, now that we know where that ground actually is!”
> The images also provide proof of Philae’s orientation, making it clear why establishing communications was so difficult following its landing on 12 November 2014.
Mostly the curiosity of the public and more importantly the scientists who worked so hard on the project only to have their lander not land properly.
Otherwise the fact that Philae was lost almost immediately upon landing has been a huge story line this past year. I believe the blog assumed the readers would know this. A CNN article would typically provide back story but this is original source from ESA.
It's like, if SpaceX launches a rocket and it explodes - a real failure would be if they captured no telemetry and had no idea what happened vs knowing everything that happened and being able to replay the mission after the fact. Often times the data is far more important than the outcome.
1. Launch contracts for paying customers where mission success was defined as "unharmed payload to correct orbit".
2. Test/demo missions with mass simulator instead of payload where mission success was defined as "unharmed payload to correct orbit" (two missions: Falcon 1 Flight 4 [0] and Falcon 9 Flight 1 [1]).
3. Rocket landing development flights with Grasshopper where mission success was defined as advancing the ability to land the booster.
SpaceX did R&D on all flights (for example they unsuccessfully tried parachute recovery), but for all flights of Falcon 1 and Falcon 9 (not Grasshopper), they always stated that mission success is to get the customer's payload unharmed to the correct orbit, or to demonstrate the ability to get the customer's payload unharmed to the correct orbit. If they defined mission success as anything else, a potential customer might think SpaceX would sacrifice the payload to advance SpaceX's own goals (like recoverability R&D), and this customer would not fly with SpaceX.
0 - https://en.wikipedia.org/wiki/Ratsat
1 - https://en.wikipedia.org/wiki/Dragon_Spacecraft_Qualificatio...
When a rocket explodes on a launch pad, and you've gathered petabytes of telemetry data and sensory data from all of it's systems, you can study and research that data to figure out what went wrong and put procedures and systems in place to mitigate that in the future. You learn from the mistakes, thus the outcome of the failure is a success. This doesn't mean we should stand in the viewing area of SpaceX's control center and cheer them on for their work in making a rocket explode. They still failed their mission, but they can make their future missions more safe and more robust because of what they learned in a real world failure situation.
http://www.esa.int/spaceinimages/Images/2016/09/OSIRIS_narro...
Shame the spears could not stick it on at the first impact.
[1] https://en.wikipedia.org/wiki/Philae_(spacecraft)#/media/Fil...
[1] https://www.youtube.com/watch?v=rJ2eqH3Bz4c
[2] http://blogs.esa.int/rosetta/2014/11/14/three-touchdowns-for...
These numbers sound completely ridiculous, unless you've played Kerbal Space Program, and know the visceral pain of bouncing above Minmus with a pixel of monopropellant left in the tanks.
[changed, thanks]
Linked from http://www.esa.int/spaceinimages/Images/2016/09/OSIRIS_narro...
[1]: https://en.wikipedia.org/wiki/67P/Churyumov%E2%80%93Gerasime...
I looked at the pictures and the human eye can barely see the lander. Considering that the chances of losing these landers is not that low, I don't understand why they don't make them visually more distinctive.
Andrew Ng gave a talk recently where he talks about designing the autonomous cars not for aesthetics, but predictability (via visual distinctiveness). [1] In the same spirit, shouldn't there be efforts to make these spacecraft modules more visually distinctive?
I suspect there's a lot of re-thinking of how to land on a comet going on as well.
I can imagine a cage-like outer shell where the robot inside is able to rotate on two axes under power. Let it tumble any which way and then use sensors to determine the correct orientation and right itself.
NASA has a concept for this: https://ti.arc.nasa.gov/tech/asr/intelligent-robotics/tenseg...
I've tried to find a video showing it happening, but while there's lots of animations of bouncing, rolling, and the final opening up, they all miss the critical moment. Also, car safety videos are really badly poisoning the search results...
Here you go. Really enjoyed watching that.
"Considering that the chances of losing these landers is not that low" - most of the time, when the mission fails, they don't make it to the surface, though. As far as I know, Beagle 2 is the only lander that was lost and later found. The Mars Polar Lander likely dropped onto the surface from some 40m up, maybe a wreckage could be found there. But other than that, I'm not aware of any landers that could be found with a camera in orbit. Debris is hard to find, even on earth - it took over 20 hours to find a crashed fighter jet in Switzerland last week, and another day to find the pilot's body.
If it was hot pink it would have made no difference, it ended up in a bad spot with limited solar power.
ESA is lucky it had a high-resolution camera to distinguish the lander from the terrain. If you only have low-res cameras, it might be useful to have a visually distinguished lander so you find it despite of poor resolution (1 bright pixel).
A naive solution might be to make future landers reflect a certain wavelength and use a tiny camera that is tuned to capture that wavelength. Finding the lander should be much easier then.
You could probably have any number of multi-purposed systems for that task.
That's a complicated way of saying "paint it like barricade tape", isn't it?
Rather than search for it, let it tell Rosetta where it is.
The problem with this is that even though the beacon could be only a few grams and use micro-watts (1 milliwatt transmission 1/1000th of the time?) of energy, Rosetta would need a receiver capable of picking it up.
I assume Rosetta has something like software defined radio but due to when it was designed, not sure if this is the case. In any case Rosetta is loaded with really sophisticated radio gear probably it could be build such that there is no weight or energy penalty for this.
Wish more NASA folk would read hacker news and could chime in
> Radio ranging data tied its location down to an area spanning a few tens of metres, but a number of potential candidate objects identified in relatively low-resolution images taken from larger distances could not be analysed in detail until recently.
We don't know just how low Philae can go, however, there is a good chance it's electronics won't break below the rated temperature.
I hope they finish the series!
All panels are available at its sister wiki [2]
In my opinion it is a beautiful work of art, pushing the limits of what the media allow the artist to do (the media in this case being comic strips in the webcomic format.
[2] https://www.explainxkcd.com/wiki/index.php/1446:_Landing/All...
To those who didn't click on the second link, you really should. It is like a journal of the lander, except in webcomic format.
The second link, that's the one that has all the panels.
Goes on to mention producing a true-color photo is kind of a pain in the ass for these probes.
0. http://www.straightdope.com/columns/read/3088/why-are-images...
About the only use for colour photos in space is PR with non-scientists anyway. That was one major obstacle the Hubble Space Telescope had to face. It's a useful component, to be sure, but not one to justify adding much more weight or cost to a planned mission in all cases.
In case of Rosetta/Philae the probe was very weight-restricted, taking even a very long course towards the comet to save fuel since it didn't have much.
Combine multiple spectrum and you get a color image.(Though comets don't have too much change across the spectrum.)
I imagine it's easier to properly calibrate a monochrome camera, and makes it easier to image stuff outside of the visible wavelengths.
Nice to know that it was still there after the last burst, that it hadn't been swept into space. And from the pictures it's going to be on there for awhile.
The succession of missions (going back 20 years now) is here: http://neo.jpl.nasa.gov/faq/#spacecraft
Compared to the rest of the achievements of this mission, it seems like this should have been relatively easy: 67P is all of like 2.5 miles wide and the orbit is at like 10 miles. You'd think that a few high res photos in a single orbit would capture nearly every inch of the entire rock.
What kind of landing gear + fixation gear would have been better?
Harpoons protruding from each leg could be fired automatically as soon as a stable enough position was detected, or manually when deemed safe; having more legs available could only improve chances of getting a safe fixation.
Neither are the people who worked on this lander :)
It's pretty hard to see the details of a cometary surface from earth. And there isn't much you could do with no gravity and an all-rubble surface either way.
> It included bolting itself to the surface, if I remember correctly, but it seems almost impossible to fixate three legs with almost no gravity on that surface.
Philae had a harpoon for anchoring itself to the surface (with a thruster on the other side to compensate). The harpoon failed to fire. The legs were not intended for fixation, only to dampen the landing.
I'm following this mission almost from the beginning, amazed by the success despite Philae's short lived life on comet, and think the science aspect of it all is unbelievably great. But that landing moment made all the difference, and it failed to fix it on the surface, hence the criticism.
Would we consider Curiosity mission success if landing put it upside down?
Legs keep it oriented, give a stable platform, and cushion the initial landing.
Top thruster pushes it into the surface, damping any bounce back from the impact.
Harpoons attach to the surface, affixing it permanently.
The top thruster was reported to not work at all, and the harpoons were unable to work by themselves. It's not clear if they would have worked if the top thruster was working as well.
> “This wonderful news means that we now have the missing ‘ground-truth’ information needed to put Philae’s three days of science into proper context, now that we know where that ground actually is!” says Matt Taylor, ESA’s Rosetta project scientist.
It is important because Philae did made measurements and sent the data to us, but we didn't knew what the measurements measured, now we know.
It would be like throwing a ball that can tell about how much a place is wet in a random direction, and conclude that some place is 90% wet... Then, what place it was? A lake? A swamp? A beach? And then you find a picture of it in a bog, and conclude the bog was 90% wet.