8
TH
EUROPEAN CONFERENCE FOR AERONAUTICS AND SPACE SCIENCES (EUCASS)
Conference on “Reusable Systems for Space Access”. July 1–4, 2019, Madrid, Spain.
Overview of Flight Guidance, Navigation, and Control
for the DLR Reusability Flight Experiment (ReFEx)
René Schwarz
1⋆†
, Daniel Kiehn
2‡
, Guilherme F. Trigo
3†
, Bronislovas Razgus
4†
, Andreas Wenzel
5†
,
David Seelbinder
6†
, Jan Sommer
7§
, Stephan Theil
8†
, Markus Markgraf
9¶
, Michael Dumke
10†
,
Martín Reigenborn
11 †
, Matias Bestard Körner
12†
, Marco Solari
13†
, Benjamin Braun
14¶
, Dennis Pfau
15§
†
German Aerospace Center (DLR), Institute of Space Systems
Robert-Hooke-Str. 7, DE–28359 Bremen, Germany
‡
German Aerospace Center (DLR), Institute of Flight Systems
Lilienthalplatz 7, DE–38108 Braunschweig, Germany
§
German Aerospace Center (DLR), Simulation and Software Technology
Lilienthalplatz 7, DE–38108 Braunschweig, Germany
¶
German Aerospace Center (DLR), Space Operations and Astronaut Training
Oberpfaffenhofen, DE–82234 Weßling, Germany
⋆
Corresponding author
Abstract
This paper gives an overview of the proposed GNC architecture for DLR’s Reusability Flight Experiment
(ReFEx), which is split into two main subsystems: The Guidance and Control (G&C) subsystem, which
determines the desired trajectory from the current flight state to a designated target and issues the neces-
sary commands to the actuators (canards and rudder, as well as a reaction control system for flight phases
outside the atmosphere) by calculating the necessary forces and torques based on the required changes of
velocity and attitude for following this trajectory; the Hybrid Navigation System (HNS), which is respon-
sible for estimating position, velocity, attitude, angular rates, and other parameters of the flight state. It
does so by real-time fusion of measurements of inertial sensors (accelerometers and gyroscopes) with the
measurements of GNSS receivers, Sun sensors, laser and radar altimeters. The requirements and boundary
conditions set by the mission, the current design baseline for both subsystems, the stability analyses for
flight control, the basic guidance strategy chosen as well as the navigation performance assessment through
covariance analysis are described and discussed.
1. Introduction
The German Aerospace Center (DLR) is studying future Reusable Launch Vehicles (RLV) with horizontal landing ca-
pability. For this purpose, DLR is developing the Reusability Flight Experiment (ReFEx), which is a sub-scale demon-
strator representing a winged first stage of an RLV. It has a mass of around 400 kg and is approximately 2.7 m in length
with wings spanning about 1.1 m. The mission shall enable the development of key technologies necessary for future
RLV applications, culminating in their demonstration with a controlled autonomous return flight in a representative
scenario.
In order to bring such space systems back to Earth, determining and actively controlling the flight state, i. e.,
position and attitude, is essential. These capabilities are usually provided by Guidance, Navigation and Control (GNC)
Revised paper as of July 1, 2019
1
E-Mail: rene.schwarz@dlr.de, ORCID: 0000-0002-8255-9451
2
E-Mail: daniel.kiehn@dlr.de, ORCID: 0000-0001-7383-0740
3
E-Mail: guilherme.trigo@dlr.de, ORCID: 0000-0001-8173-9592
4
E-Mail: bronislovas.razgus@dlr.de
5
E-Mail: andreas.wenzel@dlr.de, ORCID: 0000-0002-4370-1291
6
E-Mail: david.seelbinder@dlr.de, ORCID: 0000-0003-4080-3169
7
E-Mail: jan.sommer@dlr.de
8
E-Mail: stephan.theil@dlr.de, ORCID: 0000-0002-5346-8091
9
E-Mail: markus.markgraf@dlr.de
10
E-Mail: michael.dumke@dlr.de, ORCID: 0000-0002-5587-7884
11
E-Mail: martin.reigenborn@dlr.de
12
E-Mail: matias.koerner@dlr.de
13
E-Mail: marco.solari@dlr.de
14
E-Mail: benjamin.braun@dlr.de, ORCID: 0000-0002-0193-6607
15
E-Mail: dennis.pfau@dlr.de
Copyright © 2019 by the German Aerospace Center (DLR). Published by the EUCASS association with permission.
DOI: 10.13009/EUCASS2019-739
