First Steps in Experimental Investigation of Legged Lunar Lander Touchdown Dynamics

Paper number

IAC-08.A3.2.B9

Author

Mr. Robert Buchwald, EADS Astrium Space Transportation, Germany

Coauthor

Dr. Jochen Albus, EADS Space Transportation GmbH, Germany

Coauthor

Dr. Mark Kinnersley, EADS Astrium Space Transportation, Germany

Coauthor

Mr. Lars Witte, Deutsches Zentrum für Luft und Raumfahrt e.V. (DLR), Germany

Coauthor

Dr. Lutz Richter, Deutsches Zentrum für Luft und Raumfahrt e.V. (DLR), Germany

Year

2008

Abstract

The landing leg technology is one of the critical elements with low TRL in view of future European planetary exploration programs and a specific predevelopment program has to start early and has to run in parallel to the future mission project phases, to timely achieve the requested maturity and to mitigate the development risk. In particular numerical simulations and early breadboard testing with scaled models are to be planned to prove the functional concepts before in a next step of complexity test with a complete 1:1 Lander demonstrator can be done.
The experimental verification of the landing dynamics with scaled models was already one of the key issues in the NASA Apollo Moon Mission. Therefore, the proper understanding of touchdown dynamics, considering reduced gravity forces, model inertia, ground contact forces and landing leg geometry and functional characteristics (number of legs, kinetic energy absorbing system, e.g. aluminum honeycomb crash cartridges ) is a prerequisite to again safely land on lunar surface with future unmanned vehicles. The understanding of the vehicle touchdown dynamics will be gained by analytical and numerical simulation as well as by testing of scaled models.
A joint EADS Astrium and DLR Institute of Space Systems (both Bremen, Germany sites) cooperation aims for contributions to that field of engineering with new analytical simulations and experimental investigations using a Lander dummy based on the proposed NEXT Small Lunar Lander.
The experimentation environment is provided by DLR’s Landing and Mobility Test Facility (LAMA) currently being set up. LAMA consists of an industrial robot system moving alongside and above a realistic terrain in the form of a simulated planetary surface consisting of a 10 m x 4 m bin filled with a physical regolith stimulant and an offloading device to adapt the earth weight of the test object to the planetary weight under study (simulation of reduced gravity environment). This is demanded to realistically simulate touchdown dynamics and tip-over stability of a Lander spacecraft in the presence of terrain slopes, soil interaction and a lateral velocity component in reduced g environments. Simulations of the Lunar Lander touchdown dynamics will allow defining the landing leg geometry and functional characteristics, to ensure a stable landing on the lunar surface. These simulations shall verify the compliance of a baseline design with the functional and performance requirements, which are partly in contradiction. A soft landing, with low loads acting on the Lander requires low crash forces. Low crash forces will lead to high strokes within the crash elements. This might cause clearance problems with the ground.
The analytical and numerical models have to be validated by test. Therefore, a simplified scaled model of a baseline Lunar Lander configuration has to be developed. Numerical simulations will support the development of a scaled model, providing similarity for the main dynamic characteristics of the baseline Lunar Lander.
The tests, performed on the LAMA facility, will then allow for first steps in the experimental verification of such a Lunar Lander. This includes systematically assessment of scaled geometry, mass and inertia of a Lander as well as the change in soil properties simultaneously in a test. In particular, highly dynamic soil deformation processes such as occurring during touchdown of a planetary Lander are hardly amenable to reliable numerical simulations of landing leg dynamic and will benefit from validation by appropriate experiments.
The paper will provide an introduction in the activities linked with the numerical simulation and breadboard tests foreseen in the predevelopment of landing legs concepts as one critical technology for future European planetary exploration programs.

Abstract document

IAC-08.A3.2.B9.pdf

Manuscript document

IAC-08.A3.2.B9.pdf (🔒 authorized access only).

To get the manuscript, please contact IAF Secretariat.