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0 pointsthrowaway_yy2Di11y ago0 comments

1.7 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

[PDF mirror] http://www.researchgate.net/publication/257664668_The_Rosett...

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

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4 comments · 2 top-level

Rebelgecko11y ago· 1 in thread

Since an RTG creates more "waste" heat than actual electricity, would that obviate the need for the thermal control system? Or at least reduce the amount of insulation needed?

acqq11y ago

Typically it wouldn't "obviate the need for the thermal control system," see fbender's answer:

https://news.ycombinator.com/item?id=8614514

"An RTG's primary objective is to produce electrical energy (at an abysmal efficiency). The excess heat generated by an RTG is seldomly used for thermal control since it can also not be regulated and it emits simply too much heat energy."

hrjet11y ago· 1 in thread

Thanks, but now I wonder. Mass is different from Weight (absolute and relative respectively). Are we comparing apples and oranges here?

acqq11y ago

We compare correctly: we measure everything on Earth (that means, under the same gravity) and the proportionality holds, so it's still more than 20 times less mass to carry for the power source with the given solar panels vs. the RTG. The mass doesn't go away, the amount of stuff remains, the weight is how much something pulls down the spring in the spring scale and that depends on gravity, but we conveniently measure on Earth.

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