June 4, 2014

Heating Things Up: ESA’s Solar Orbiter Passes Heat Shield Test

Alan McStravick for - Your Universe Online

The European Space Agency (ESA) has recently announced the successful on-Earth testing of its Solar Orbiter's protective heat shield. The test, conducted at the ESA's Technical Center in Noordwijk subjected a 'structural-thermal' version of the craft's sunshield to an artificial Sun for a period of two weeks in their vacuum chamber - the largest in Europe. The results prove the shield will have no issue with the extreme temperatures present in close range to our parent star.

The Solar Orbiter is scheduled for launch in 2017 and is loaded with a plethora of instrumentation that will allow the craft to perform in-situ measurements and high-resolution imaging of our Sun. En route to its rendezvous with the star, the craft has been designed to deal with solar illumination, the cold of deep-space and its own internal heat sources. The outcome of this test ensures it will be able to maintain the perfect operating temperature for its mission.

The Solar Orbiter's mission will take it a distance equal to almost a quarter of the distance Earth is from the Sun. In doing so, the craft will suffer a full 13 times the intensity of terrestrial sunlight we experience on Earth. Temperatures around the Solar Orbiter are expected to reach almost 1,000 degrees Fahrenheit.

The shield is a multilayer of insulation foil measuring approximately 10 feet by 7 feet with a black-treated surface. In the shield are specially designed openings meant to allow different sensor equipment to protrude through. These sensors are protected by either protective glass or beryllium.

The ESA's testing facility subjected the shield to a simulated sunlight produced by 19 xenon lamps directed through a series mirror arrays to intensify the effect. At the same time, the chamber of the orbiter was chilled by liquid nitrogen to a temperature of approximately -300 degrees Fahrenheit. This temperature simulates the cold clime of space surrounding the craft.

To monitor the test, the ESA employed an infrared camera system that both monitored and measured the temperature of the front facing side of the heat shield in real time. Additionally, other heat sensors were glued in key locations on the multilayer structure.

One last camera, a photogrammetric camera, maintained its focus on the heat shield during testing. The purpose of this camera was to detect even the slightest movement on the front face of the sunshield during the testing process as the temperatures continued to increase.

Once launched in 2017, the mission of the orbiter will be dedicated to solar and helioshperic physics. The Solar Orbiter was selected as the very first medium-class mission of the ESA's Cosmic Vision 2015-2025 Program. According to the ESA, the orbiter is meant to address questions regarding the initial development of planets as well as the emergence of life and the origins and fundamental physics at work in our Universe.

Image 2 (below): Solar Orbiter’s sunshield structural and thermal model during thermal balance testing in ESTEC’s Large Space Simulator on 17 May 2014. The image on the left is an optical view; the image on the right is in infrared. Credit: ESA