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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

by 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

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.