Isotope60 — Radioisotope Batteries in Space =========================================== Radioisotope power systems (RPS), often called radioisotope thermoelectric generators (RTGs), generate electricity from the heat produced by radioactive decay. These systems are used when solar power is impractical, such as deep-space missions or permanently shadowed regions. How They Work ------------- 1. A radioactive isotope produces heat through natural decay. 2. Thermocouples convert the heat into electricity. 3. No moving parts → extremely reliable for decades. Common Space Power Isotopes --------------------------- Isotope Half-life Why It Is Used ---------- ------------ ---------------------------------- Pu-238 87.7 y High heat output, long mission life Sr-90 28.8 y Used in some early Soviet RTGs Po-210 138 d Very high power, short missions Cm-244 18.1 y Experimental high-power isotope Why Pu-238 Is Preferred ----------------------- Plutonium-238 is ideal for spacecraft because it: • produces large amounts of heat • has a long half-life • emits mostly alpha radiation • can be safely shielded Famous RTG-Powered Missions --------------------------- Mission Launch Year Destination ------------------ ------------ ----------------------- Voyager 1 1977 Interstellar space Voyager 2 1977 Outer solar system Cassini 1997 Saturn New Horizons 2006 Pluto and Kuiper Belt Curiosity Rover 2011 Mars Perseverance Rover 2020 Mars Typical RTG Output ------------------ A modern Pu-238 RTG generates: ~2000 watts of heat ~100 to 300 watts of electrical power Advantages ---------- • Works far from the Sun • Operates for decades • Extremely reliable • No moving parts Disadvantages ------------- • Limited fuel supply • Expensive isotope production • Lower efficiency than solar panels Notes ----- RTGs are not nuclear reactors. They do not sustain chain reactions and cannot explode like nuclear weapons.