Trade Studies

Ever since the 60's, many satellites (particularly those going where sunlight is scarce) have run on RTGs. Think of missions like Voyager one and two, Cassini, even the mars rovers Curiosity and Perseverance are running on Nuclear energy. What material is used varies differently however based on the mission type. Above here you can see a Trade Studies diagram, which compares and contrasts the different available materials for running the RTGs, each of which have their own pros and cons. Based on the criteria chosen of Abundance, Safety, Radiation Shielding, Power Density, Cost, and Half-life, each material was rated on a scale of one to five, with one being the material was not good for this criteria, and five meaning it was great or even phenomenal for its criteria. An example could be Americum-241, which scored very low with its power density(only 0.114 w/g), but scored exceptionally well for its exceptionally high half life(of 432 years). Each score was weighted based on its importance to the mission, then added up to create the total score. While this score is a great representation of a material's effectiveness, it is not necessarily the deciding factor, as is seen here. Americum-241 has the highest total score of all four materials, yet is ranked second. This is because when the material is considered for practical application, it has an unnecessarily long half-life along with an abysmal power density, which is unsuitable for the Tiger's Ebb mission.

The material that was ultimately decided upon to power the Tiger's Ebb mission, was Plutonium-238 due to its adequate abundance, high safety margins, its relatively low required shielding, its high power density(0.54 W/g), its adequate cost, and its great Half-life(87.7 years). Plutonium-238 should serve as an ample power source when used in a multi-mission radioisotope thermoelectric generator (MMRTG) or something similar. Another possibility that comes with using both Nuclear Propulsion and Nuclear power, is the possibility of combining the subsystems, at least for the satellite to save on space, similar to how a car engine provides power to the batteries to power the car.