Basically its almost impossible to design a battery to withstand near absolute zero for this period of time (half a month). Nothing is 100%, i.e there is likely some high confidence interval that the batteries and capacitors etc involved could not survive this (found out during cold freeze research and testing etc) but there is some finite small chance worth checking for anyway just in case.
There was no RTG etc like say found on voyager space probes (to provide a steady residual minimum temperature to critical payloads), likely the mass and other budgets would cascade by that and was deemed not worth it.
i.e the thermal management was never designed by its basis to survive the lunar night (and the mission was timed to make full use of the lunar day before it with this in mind tool).
CE20 E13 Engine Hot Test for the Gaganyaan & 22t Thrust Qualification
September 25, 2023
ISRO successfully completed the CE20 E13 engine hot test for the Gaganyaan qualification and 22-tonne thrust qualification. The engine developed by the Liquid Propulsion Systems Centre (LPSC), Valiamala was tested at ISRO Propulsion Complex (IPRC), Mahendragiri on September 22, 2023.
The CE20 engine is a vital component, serving as the powerhouse of the Cryogenic Upper Stage (CUS) responsible for propelling the upper stage (C25) of the LVM3 vehicle. It has demonstrated its capability by successfully operating at a thrust level of 19 tonnes in six successive LVM3 missions, including the Chandrayaan-2, Chandrayaan-3, and two commercial OneWeb missions.
To enhance the payload capacity of the LVM3 vehicle, ISRO is upgrading the CE20 engine. The upper cryogenic stage is being transformed into the C32 stage with increased propellant loading capacity, and the engine is being modified to operate at a higher thrust level of 22 tonnes. To ensure the engine's readiness for critical missions, a series of ground hot tests were deemed necessary. The CE20 engine hardware referred to as E13 was selected for both Gaganyaan qualification and 22-tonne thrust level operations.
The journey to achieving a 22-tonne thrust capability began with E13 HT-01, a test focused on engine tuning, successfully conducted for a 50-second duration. This initial test set the stage for the upcoming trials. E13 HT-02 marked a significant milestone, conducted on August 30, 2023, with the engine operating flawlessly for an impressive 720 seconds. This test demonstrated the engine's reliability and stability.
The third hot test, E13 HT-03, was the pivotal moment in completing the CE20 engine qualification for the Gaganyaan program. On September 22, 2023, this test was conducted at the state-of-the-art test facility located at IPRC, Mahendragiri. During this test, the CE20 engine operated at the coveted 22-tonne thrust level for a duration of 670 seconds. Both the engine and the testing facility performed flawlessly, meeting all the performance parameters.
The successful completion of E13 HT-03 signifies the culmination of rigorous testing and the readiness of the CE20 engine for the Gaganyaan program. With all the necessary tests completed, the CE20 engine is now poised for the demanding requirements of the Gaganyaan mission and future endeavours.