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Wow, I just looked into it and it turns out the ESA actually hasn't used RTGs before, but planned to use one with this very mission[0:p78]. The only ESA mission

by guscost 12y ago

Wow, I just looked into it and it turns out the ESA actually hasn't used RTGs before, but planned to use one with this very mission[0:p78]. The only ESA mission I can find which used an RTG is the Cassini-Huygens probe[1], a collaboration with NASA. [0] http://www.ianus.tu-darmstadt.de/media/ianus/pdfs/arbeitspapiere/5-1998.pdf http://www.ianus.tu-darmstadt.de/media/ianus/pdfs/arbeitspap... [1] http://en.wikipedia.org/wiki/Cassini–Huygens http://en.wikipedia.org/wiki/Cassini–Huygens

acqq 12y ago
Where do you see that ESA actually planned to use a RTG for Rosetta mission? On the p78 is only "The consortium formed of leading institutes of Europe includes the scientific organisations of Germany, Finland, Italy, Hungary, Great Britain and Austria, which have not the technological capacity to manufacture RTGs. It was therefore decided to develop new high-efficiency solar cell for this deep space mission."
- guscost 12y ago
  Here's the passage as it appears on page 78 of the IANUS paper[0]: "Up to now there exists a number of projects developed by ESA which plan to use radionuclide power or heat sources. One of the most far progressed is the 'Rosetta' project." [Update: When this paper was written, it looks like they might have been only planning to use an RHU to heat the lander: "'RoLand' includes not only the solar power generator but also RHU on plutonium-238 of the RHU 'Angel' type. By the opinion of the project experts, the RHU use is the most desirable, sensible and reliable means for achieving the main goal of the mission."] [0] Energy supply for deep space missions: Risks of nuclear power in space and prospects for solar alternatives. From http://www.ianus.tu-darmstadt.de/media/ianus/pdfs/arbeitspapiere/5-1998.pdf http://www.ianus.tu-darmstadt.de/media/ianus/pdfs/arbeitspap...
  - acqq 12y ago
    Yes it's only RHU (Radioisotope heater unit) is mentioned, http://en.wikipedia.org/wiki/Radioisotope_heater_unit http://en.wikipedia.org/wiki/Radioisotope_heater_unit never RTG (Radioisotope thermoelectric generator). "While both RHUs and RTGs use the decay heat of a radioactive isotope (usually Pu-238), RHUs are generally much smaller as a result of omitting the thermocouples and heat sinks/radiators required to generate electricity from heat."
    - guscost 12y ago
      But then there seems to be a contradiction here. If the ESA was planning to use an RHU powered by plutonium-238, which resource (your word) or technological capacity (from the IANUS paper) were they missing that prevented them from using a plutonium-238 RTG? Money?
      - alexbecker 12y ago
        It would have made the lander heavier, thereby increasing the size and cost of everything else.
      - fbender 12y ago
        RHUs are in no way comparable to RTGs: They are basically very small amounts of radioactive material fully enclosed in a thermally conductive container. Think of it as an always warm pebble stone. They are unregulated sources of (almost) constant heat and have no other purpose. In aerospace engineering, they are used in just a few circumstances to augment the active heaters in a spacecraft: Heater lines, which are resistive heaters in a foil with a PI controller. You need active thermal control since your environment changes a lot (launch, preliminary orbit, transit, orbit) and thus its thermal parameters (some parts of a spacecraft may experience temperature gradients of a few hundred Kelvin within a few minuts). Most spacecraft designs have issues with overheating and thus RHUs cannot be used here. 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.

by guscost 12y ago

acqq 12y ago

Where do you see that ESA actually planned to use a RTG for Rosetta mission? On the p78 is only "The consortium formed of leading institutes of Europe includes the scientific organisations of Germany, Finland, Italy, Hungary, Great Britain and Austria, which have not the technological capacity to manufacture RTGs. It was therefore decided to develop new high-efficiency solar cell for this deep space mission."

guscost 12y ago
Here's the passage as it appears on page 78 of the IANUS paper[0]: "Up to now there exists a number of projects developed by ESA which plan to use radionuclide power or heat sources. One of the most far progressed is the 'Rosetta' project." [Update: When this paper was written, it looks like they might have been only planning to use an RHU to heat the lander: "'RoLand' includes not only the solar power generator but also RHU on plutonium-238 of the RHU 'Angel' type. By the opinion of the project experts, the RHU use is the most desirable, sensible and reliable means for achieving the main goal of the mission."] [0] Energy supply for deep space missions: Risks of nuclear power in space and prospects for solar alternatives. From http://www.ianus.tu-darmstadt.de/media/ianus/pdfs/arbeitspapiere/5-1998.pdf http://www.ianus.tu-darmstadt.de/media/ianus/pdfs/arbeitspap...
- acqq 12y ago
  Yes it's only RHU (Radioisotope heater unit) is mentioned, http://en.wikipedia.org/wiki/Radioisotope_heater_unit http://en.wikipedia.org/wiki/Radioisotope_heater_unit never RTG (Radioisotope thermoelectric generator). "While both RHUs and RTGs use the decay heat of a radioactive isotope (usually Pu-238), RHUs are generally much smaller as a result of omitting the thermocouples and heat sinks/radiators required to generate electricity from heat."
  - guscost 12y ago
    But then there seems to be a contradiction here. If the ESA was planning to use an RHU powered by plutonium-238, which resource (your word) or technological capacity (from the IANUS paper) were they missing that prevented them from using a plutonium-238 RTG? Money?
    - alexbecker 12y ago
      It would have made the lander heavier, thereby increasing the size and cost of everything else.
    - fbender 12y ago
      RHUs are in no way comparable to RTGs: They are basically very small amounts of radioactive material fully enclosed in a thermally conductive container. Think of it as an always warm pebble stone. They are unregulated sources of (almost) constant heat and have no other purpose. In aerospace engineering, they are used in just a few circumstances to augment the active heaters in a spacecraft: Heater lines, which are resistive heaters in a foil with a PI controller. You need active thermal control since your environment changes a lot (launch, preliminary orbit, transit, orbit) and thus its thermal parameters (some parts of a spacecraft may experience temperature gradients of a few hundred Kelvin within a few minuts). Most spacecraft designs have issues with overheating and thus RHUs cannot be used here. 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.