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Powering the mission to Mars

Powering the mission to Mars

. 3 min read

Edited by : Tareq Aljumylee

July 30, 2020

A United Launch Alliance Atlas V rocket with NASA’s Mars 2020 Perseverance rover onboard launches from Space Launch Complex 41, Thursday, July 30, 2020, at Cape Canaveral Air Force Station in Florida. The Perseverance rover is part of NASA’s Mars Exploration Program, a long-term effort of robotic exploration of the Red Planet.

Powering the mission will be done using RTG, so  what is RTG?

RTG stand for Radioisotope Thermoelectric Generator, it is an electricity generating device that uses an array of uniocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This generator has no moving parts.

It is worth mentioning that the efficiency of RTG barely ecced 7%.

Different radio-isotopes used as fuel , the selection is based on the mission life time as shown in the following table.

Table showing different candidates for fuelling RTG(Wikipedia)
RADIOISOTOPES – APPLICATIONS IN PHYSICAL SCIENCES -Nirmal Singh

General overview of RTG shown below, the radioactive source referred to as GPHS (General Purpose Heat Source).

Radioisotope thermoelectric generator

A breakdown view of the RTG shown below

@ABHISHEK KAPADIA

The following figure shows the location of SiGe Unicouple

Cutaway of a General-Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG). The Pu-238 fuel pellets are encased in the stack of GPHS blocks in the center. Source: NASA Radioisotope Power Systems

SiGe thermocouples in an RTG convert heat directly into electricity. Thermoelectric power generation requires a constantly maintained temperature difference among the junctions of the two dissimilar metals (i.e. Si and Ge) to produce a low power closed circuit electric current without extra circuitry or external power sources.[3][10]

A large array of SiGe thermocouples/unicouples form a thermopile that was incorporated into the design of radioisotope thermoelectric generators (RTGs) used in the missions Voyager, Galileo, Ulysses, Cassini, and New Horizons.[11] On these spacecraft, Pu-238 dioxide fuel undergoes natural decay. The SiGe thermocouples/unicouples convert this heat to hundreds of Watts of electrical power.[10]

Components of the SiGe unicouple(Wikipedia)

References:

https://mars.nasa.gov/internal_resources/788/

Powering Perseverance: NASA’s Mars 2020 Mission Fueled by DOE National Labs
Powering Perseverance: NASA’s Mars 2020 Mission Fueled by DOE National Labs