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To be completely fair, it was not powered by solar energy - the experiments were run on power from the non-rechargeable battery. Which is fine, this is what Phi
by jdiez17 12y ago
To be completely fair, it was not powered by solar energy - the experiments were run on power from the non-rechargeable battery. Which is fine, this is what Philae was designed to do. It looks like they completed all the objectives in the First Science Sequence (FSS), which was the lander's primary mission.
- acqq 12y agoAnd also to be fair, the whole mission didn't depend on any RTG technology, used only by the US and Russia in space: https://news.ycombinator.com/item?id=8610585 https://news.ycombinator.com/item?id=8610585
- jdiez17 12y agoWhile it would have been convenient to have a RTG onboard, it would have made the lander too heavy (with the current RTG technology. Smaller nuclear generators are possible in theory but none have been built yet.)
- acqq 12y agoYes, the lander was around 100 kg, whereas RTG would weight around 40 kg alone. And it would anyway be needed only in this case of unfortunate landing in the shadow. Once we talk about details it's clear how a lot of the complaints are based purely on a huge ignorance. It's good to ask to learn. But when somebody starts from the position that people who managed 25-year mission missed something to him "simple and obvious"...
- hrjet 12y ago> It's good to ask to learn. In that spirit, I have a question. How heavy are the solar panels? If their weight is comparable to 40kg then it makes RTG more attractive.
- gtirloni 12y agoI'm not sure about the exact weight but perhaps an estimation can be derived from the specifications available in the fact sheet [1] - Contractor: Galileo Avionica SpA - Cells Type: Si, Hi-ETA LILT - Cells Size: 3x3 cm2 - Power equiv. @ 3 AU: 32W - Total Size: 2.2m2 - Lifetime: 10 years [1] - http://www.dlr.de/rd/Portaldata/28/Resources/dokumente/rx/Philae_Lander_FactSheets.pdf http://www.dlr.de/rd/Portaldata/28/Resources/dokumente/rx/Ph...
- acqq 12y agoThe weight of solar cells used on the Earth comes from making them protected from the environment, the material that produces the power itself is very thin. http://sbir.gsfc.nasa.gov/SBIR/successes/ss/3-027text.html http://sbir.gsfc.nasa.gov/SBIR/successes/ss/3-027text.html Note "1 kW/kg" specification but it's probably in the Earth's orbit, using the inverse square law, it should be an order of magnitude less where Philae now is. Still, it appears it can remain quite light to have 2 m^2 of cells there. Anybody has more exact details for the weight of the cells on Philae?
- throwaway_yy2Di 12y ago1.7 kg, I think: TABLE I Mass breakdown of Rosetta Lander, including sub-units on the Orbiter. Unit Mass (kg) Thermal Control System 3.9 ...MLI ...2.7 ("multi-layer insulation") Power System 12.2 ...Electronics ...2.0 ...Batteries ...8.5 ...Solar Generator ...1.7 ***** Sum [Lander] 97.9 Sum [incl. Orbiter units] 111.0 Excerpt from table 1, page 208 of [paywall] http://link.springer.com/article/10.1007/s11214-006-9138-2 http://link.springer.com/article/10.1007/s11214-006-9138-2 [PDF mirror] http://www.researchgate.net/publication/257664668_The_Rosetta_Lander_(Philae)_Investigations/links/02bfe50e5ecb0f3078000000 http://www.researchgate.net/publication/257664668_The_Rosett...
- hrjet 12y agoThanks, but now I wonder. Mass is different from Weight (absolute and relative respectively). Are we comparing apples and oranges here?