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Compared with the interplanetary probes of the last decades, how can the next generation in the next decades be miniaturized? Not really meaning small in size, but low in mass. The purpose would be to allow a larger part of the mass budget for science instruments. And what are the most important developments in this direction which have already happened between for example Voyager and New Horizons?

How do different functions contribute to mass on an interplanetary probe today?

I have some naive imaginations:

  • A physical structure which can survive launch from Earth. But maybe the individually sturdy components of a probe could be assembled to a fragile structure in microgravity at the ISS? For example, solar panels and radio dish could be folded out manually, without the probe having to carry the unfolding mechanism onboard.

  • Power system and thermal control. I suppose an RTG is as about slim as it can be. But what about the heat distribution system?

  • Radiation protection. One necessarily needs mass to stop cosmic rays. But it is only electronics which is sensitive to radiation (right?) So if one has multiple redundancies and can reprogram damaged chips to work around their damages, maybe shielding could be replaced by several almost massless microchips?

  • Communication with Earth. How thin and light can you make a reflecting radio dish? The rest, I suppose, is electronics which is of negligible mass already.

  • Orientation. Maybe one could use solar pressure instead of rotating wheels, or fuel for rocket engines?

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I'll just answer your proposals first:

  • Unfolding mechanisms make up a minuscule part of the structural weight. Docking at the ISS would take an enormous amount of fuel and effort. This is definitely not a workable path.
  • There are engineers who do nothing but optimize the thermal systems in spacecraft for their whole career. I find this enormously boring, but these people know what they are doing.
  • Electronics are not routinely protected by anything like a lead casing. It wouldn't help anyway, because it would have to be insanely thick to keep out gamma radiation. Redundancy mechanisms are highly developed and always applied.
  • You can save weight with lighter spacecraft antennae, if you make the antenna on the receiving side more powerful. But there are physical limits to this. New light materials and special antenna shapes also come in handy on the spacecraft.
  • The current trend is away from using the solar panels for radiation pressure. The amount of fuel you save generally does not make up for the additional complexity and cost.

I don't have the time to answer the rest of your question right now. Maybe I will find time tomorrow.

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  • $\begingroup$ Great points! But, then why is expensive slow radiation hardened electronics used, if the problem could be solved by simply using some more sets of redundant electronics? And what about Chipsats to Europa? With a cubesat as mothership. NASA did pay a little money to have a look into it. Is it astrobio-hype fiction? $\endgroup$
    – LocalFluff
    Nov 27, 2014 at 0:29
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    $\begingroup$ Spacecraft are enormously expensive, and generally do not do a lot of number crunching. That's why it makes sense to spend extra on slow radiation-hard components to get that extra bit of safety. That being said, off-the-shelf hardware with lots of redundancy is used in cheaper SC, like university-made satellites. I can't comment on the chipsat to Europa mission, because I have not studied chipsats. $\endgroup$
    – Rikki-Tikki-Tavi
    Nov 27, 2014 at 0:48

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