Overview

Atmosphere from space © NASA

During the flight external temperature might drop below -70 degrees celcius. The nearspacecraft hull must prevent the internal components from cooling below their rated temperature. At the same time the hull must be very lightweight and widthstand landing and high velocities during the first stages of descend.

The nearspacecraft hull will also function as solar reflector preventing excessive surface heating. Temperature difference between shadow and light at high altitudes can be significant due to low atmospheric pressure.

Thermal insulation

The nearspacecraft hull © ANP

The polyimide film coating provides excellent thermal insulation and reflective properties and EPS gives strong and light weight structural support while still contributing to insulation.

The nearspacecraft has three layers of thermal insulation:

• External surface - polyimide film (polyimide face visible, aluminum coating inside)
• Internal surface - polyimide film (aluminum coating visible, polyimide inside)
  
• Internal structure - Honeycombed EPS giving form, mechanical structure and additional insulation.

Additionally inside temperature will be maintained with chemical heater packs which provide +60 degrees celcius temperature for the most critical components of the nearspacecraft.

Mechanical structure

Another important function of the nearspacecraft hull is to provide rigid structure for other components such as avionics and payload. Only components outside hull in the nearspacecraft are antennas, parachute, ECD and balloon.

The hull has been divided to two removable segments allowing easy access to avionics, batteries and payload equipment. During flight these segments are joined and sealed with multiple locks and thermal insulation.