TESTING OF EXPERT NOSE MATERIAL AND SENSOR HEADS IN THE DLR ARCJET FACILITIES

Abstract

The EXPERT program is a re-entry mission to gather in-flight data of the aerothermodynamic environment. The EXPERT NAP (Instrumented Nose Assembly) is a sub-system of the EXPERT vehicle. The nose is the essential hot structure component at the front of the EXPERT vehicle to protect the vehicle internal from aerothermodynamic heat loads. The ceramic matrix composite (CMC) nose cap system, which has to withstand the extreme thermal loads during re-entry, is designed and manufactured using DLR’s C/C-SiC material. The behaviour of this material and especially all NAP components out of this material had to be tested under the EXPERT trajectory conditions. The RESPECT (payload of the IRS, University Stuttgart) and RAFLEX (payload of HTG) payloads are using ceramic sensor head (SH) bolts. These bolts will be positioned in the ceramic nose cap and are exposed to the plasma in the stagnation area. In the centre of the bolts is a hole that serves the purpose of pressure measurement (RAFLEX) and optical access to the plasma (RESPECT). System samples were integrated into a wind tunnel probe for testing them in the LBK plasma wind tunnel facility. The LBK facility at DLR in Cologne was used to create the required test environment. During various tests the behaviour of the material as well as the influence of hole and bolt edge was investigated. With the measured data, especially the ones of the RAFLEX system samples, a discussion will be performed focussed on the effect of a drill hole or a circular edge on the nose and the payload performance. The paper presents test data like the calorimeter temperature, pressure, surfaces temperatures etc. measured during the tests.