KSat Stuttgart e.V.


MIRKA2-RX - a REXUS Flight Eexperiment in Preparation for the Atmosphere Entry CubeSat Mission CAPE
The progress of the CubeSat project CubeSat Atmospheric Probe for Education (CAPE) is presented. Furthermore, the results of the recent sounding rocket experiment “micro re-entry capsule 2 REXUS” (MIRKA2-RX) are discussed with regards to the later application in the CAPE mission. During this mission a flight prototype with full sensor setup was ejected from a REXUS sounding rocket at 78 km altitude. The ejection was recorded and qualified a specially designed ejection mechanism for the capsule. Unfortunately the capsule did not activate during ejection, but was later activated on impact and recovered. An electrical mirror system on the launcher was used as a backup, which allowed to qualify the electrical system during flight phase. The focus of this paper is the design process of MIRKA2-RX, its follow up projects and the lessons learned for the CAPE mission.


DLRK2016_420341: Aufbau des Elektroniksystems der MIRKA2 Mikrorückkehrkapsel und dessen Flugergebnisse auf REXUS 19
Diese Publikation behandelt das Design des Elektroniksystems der MIRKA2 Mikrorückkehrkapsel, einem System zur Erprobung von Hitzeschutzmaterialien im CubeSat Format. Des Weiteren werden die beim Flug auf der Höhenforschungsrakete REXUS 19 gewonnenen Ergebnisse im Bezug auf das Elektroniksystem vorgestellt.


CS01_3_199 Micro Return Capsule 2 – REXUS Experiment Results

The Micro Return Capsule 2 REXUS is a technology demonstrator for a CubeSat standard compliant return capsule with a maximum diameter of 10 cm. Such a capsule will allow for low cost atmospheric re-entry missions to qualify thermal protection systems and study of occurring high enthalpy flows. To qualify the flight behavior of such a miniaturized capsule, functionality of selected components, the communication ability and the overall design a sub-orbital sounding rocket experiment was performed with the capsule being ejected in the apogee. A specifically designed separation mechanism was used to eject the capsule and qualified for utilization in later missions in orbit. The capsule itself was equipped with several thermocouples, pressure sensors and a thermopile to measure future heatshield performance and parameters of the surrounding environment during descent. An IMU and a GPS receiver were used to determine attitude and position of the capsule and the data was transmitted via the Iridium satellite network to produce an estimated landing location of the capsule. The capsule was successfully recovered. An electrical mirror system of the capsule resided within the sounding rocket to generate additional reference data of the flight.



The Micro-Re-Entry-Capsule-2-REXUS (MIRKA2-RX) student experiment is a precursor project for the CubeSat Atmospheric Probe for Education (CAPE) at the Institute of Space Systems (IRS) of the University of Stuttgart. CAPE is a CubeSat system, which shall allow a miniature capsule to perform a re-entry to qualify new ablator materials and to assess a respective aerothermodynamic data base. MIRKA2-RX is intended for the validation of the capsule’s flight behaviour and to ensure the functionality of the electrical and communication system.
The experiment is segmented into three components: The first segment is the capsule, which is a version of the later flight model, containing pressure, temperature, acceleration and radiation sensors. A dummy heat shield will be used, as the expected temperatures will not exceed critical levels during this suborbital return.
The second segment is the newly developed ejection-mechanism. It is designed to perform a reliable and simple ejection of the capsule using pyro cutters.
The third segment is a replica of the electric system of the capsule, which will reside within the experiment in the REXUS rocket during the entire compartment flight. It is used as a backup system in case of communication malfunction and if the capsule is irretrievable. This data can be used to evaluate the performance of the electric system independently.
When the sounding rocket reaches its apogee, the capsule will be ejected. During its return to Earth, it will collect and transmit data generated by the sensors. After its impact, it is attempted to retrieve the capsule and to extract additional data stored on board.

IAA-B10-0706P - CubeSat Atmospheric Probe for Education
The CubeSat Atmospheric Probe for Education (CAPE) mission is a nano satellite project currently under development at the Institute of Space Systems (IRS) of the University of Stuttgart, Germany, and its partners. The primary purpose of CAPE is educational, enabling engineering/science students to participate extensively in the design, operation and scientific evaluation of a multifaceted spaceflight project, based on the CubeSat pico/nano satellite standard. CAPE comprises two individual, initially coupled vehicles. The Service and Deorbit Module (SDM) constitutes a 3U CubeSat, tasked with effecting a controlled gradual de-orbit manoeuvre while simultaneously performing atmospheric measurements. It also serves as a transport for the 1U Micro Return Capsule MIRKA2, which is to be released upon attaining a specific separation altitude. Both systems re-enter Earth’s atmosphere individually, with MIRKA2 surviving the critical re-entry phase and the SDM demising in full. This contribution presents a broad overview of the CAPE mission concept in general and its motivation. The major scientific and technological objectives are defined and discussed. In addition, potential future applications of the technologies developed for or qualified in the context of CAPE, as well as the relevance of scientific data obtained therewith are briefly explored.

IAA-B10-0605 -CubeSat-sized re-entry Capsule MIRKA2
An experimental CubeSat-sized atmospheric entry capsule, designed to validate the behaviour of the Resin-Impregnated Carbon Ablator (RICA) heat shield is currently under development at the University of Stuttgart. To optimize the development effort, a shape resembling NASA's Re-Entry Breakup Recorder (REBR) is selected for the capsule due to its well-known flight behaviour, and scaled to fit CubeSat constraints. The capsule is to be deployed from a dedicated service and deorbit module (SDM) at a separation altitude of approximately 125 km. The heat shield behaviour is characterised using thermocouples, dynamic pressure sensors and acceleration sensors. Minimal communication equipment is used for data transmission.

IAA-B10-1006P - A Service and Deorbit Module for CubeSat Applications
A Service and Deorbit Module (SDM) based on a 3U CubeSat nano satellite is presented, which serves as a service module and platform for experiments and sensors for the CubeSat Atmospheric Probe for Education (CAPE) project currently under development at the University of Stuttgart. Its main objectives are to perform as a technology demonstrator for a Pulsed Plasma Thruster (PPT) based on the Institute of Space System's ADD-SIMPLEX propulsion system, to facilitate a controlled deorbit and atmospheric entry of the miniature re-entry capsule MIRKA2, and to perform extensive atmospheric in-situ measurements in the lower thermosphere over a wide range of altitudes.

An aerothermodynamic trajectory analysis for the planned Micro Return Capsule 2 (MIRKA2) in combination with a mission analysis for the whole de-orbit and re-entry system is presented. The picosatellite CubeSat Atmospheric Probe for education (CAPE) combines MIRKA2 and a Service and Deorbit Module (SDM) in a 3U+ CubeSat [1]. A micro-propulsion system and a separation mechanism on board the SDM enables a controlled de-orbit from the ISS orbit, followed by the separation and re-entry of MIRKA2. Utilising the IRS in-house code REENT [2], the trajectory of the re-entry probe is simulated. An aerodynamic model allows the computation of the capsule's drag coefficient in all flight regimes. Therewith, velocity, pressure, deceleration and heat loads at the stagnation point are calculated during the entire flight.
The findings reveal critical aerothermodynamic aspects of the re-entry of MIRKA2 and are the basis of detailed CFD analysis in order to qualify the vehicle.


A System Approach towards a miniaturized Pulsed Plasma Thruster for a CubeSat-Type Deorbit Module
A pulsed plasma thruster, based on a rescaled variant of the ADD-SIMPLEX thruster system developed at IRS, is considered for the primary propulsion system of the educational CubeSat mission CAPE (CubeSat Atmospheric Probe for Education), which is to perform atmospheric measurements and to serve as a cost-effective technology demonstrator both for high performance ablative heat shield materials and micro-propulsion systems. The system
comprises a Service and Deorbit Module (SDM) as well as a miniaturized re-entry capsule called MIRKA2 (Mikro-Rückkehrkapsel 2). The former is designed to progressively reduce the altitude from an initial level corresponding to that of the ISS and to then initiate a de-orbit manoeuvre once an appropriate separation altitude is reached. Atmospheric data from the lower thermosphere is collected during this mission phase, after which the return capsule is ejected from the SDM. The SDM then proceeds to burn up in Earth’s atmosphere following MIRKA2’s largely unscathed return. The benefits of employing a PPT for a CubeSat deorbit mission include the potential to dynamically alter the pulse frequency in order to efficiently adapt to the varying availability of electrical power depending on the respective orbital characteristics. Further benefits and also issues are identified and discussed. Suitable scaling laws are adopted and applied to the ADD-SIMPLEX configuration. A preliminary analysis approximating the performance, mass and dimensions of such a system is performed and evaluated within the context of the most recent CAPE mission specifications and system design.


ESMO Cold Gas Propulsion System
ESMO, the European Student Moon Orbiter, is the first lunar satellite to be designed, built and operated completely by students. Within this project, students of the ESMO Propulsion Teams at Stuttgart and Milan have developed a combined chemical and cold gas propulsion system. The system can provide a full 3-axis attitude control and the pressurization of the main tanks. The design baseline was driven by minimizing the costs at minimal weight using commercial off-theshelf components and already space-qualified spare parts. Considering these restrictions the challenge was to reach a high reliability and to fulfil all tasks with the required performance. This paper includes a description of the subsystem’s main components, and explains their test procedures in detail. How to implement as well as how to qualify a low budget system is described. A classification of this system is shown in a mass and cost assessment and finally the flexibility of the system is demonstrated on sample configurations.

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