Session: 04-10-01: Impact, Damage and Fracture of Composite Structures

Paper Number: 70923

Start Time: Monday, 05:50 PM

70923 - Characterizing Potential Damage to Landers and Their Payloads Caused by Regolith Ejecta During Operations on or Near the Surface of the Moon, Mars, and Other Worlds 

This research establishes methods of conducting physical testing and analysis to characterize damage to a lander that can be caused by rocket-regolith interactions during powered lander operations on or near the surface of the Moon, Mars, and other worlds.

The damage of concern is caused by regolith ejecta propelled by rocket exhaust.  Rocks from the ejecta can impact and damage the landing gear, downward-facing surfaces of the lander, and attached payloads.  Dust in the ejecta can coat the surfaces of the lander, either by settling back after being lofted or by sticking to lander surfaces.  Simulated planetary regolith was used during testing to approximate possible un-improved landing sites on the Moon, Mars, or other worlds.

Testing was conducted in atmosphere using a scale model of a recent commercial lander design with functioning rocket engine analogues which used compressed gas as a propellant.  This enabled physical testing to be conducted in a very safe and cost-effective environment compared to operating rockets that burned fuel during operation.  While this testing must be conducted with an awareness of the effects of scale on the application of the test results and there must be an understanding that testing in atmosphere has certain limits when the intended landing site is at lower pressure or in a vacuum, this testing is an important and valuable step in a wider testing program.  This testing can identify key design revisions before incurring the expense and risk to equipment from testing rocket and regolith interactions in a vacuum facility.

During this testing, the methods of recording and quantifying the damage and dust coating caused by ejecta were established.  Foam witness plates were installed on the lower exposed structures to record the impact damage from rocks and abrasion caused by regolith blast.  Adhesive covers were placed on surfaces to record the potential dust coating that could originate from regolith ejecta.  The apparent color changes to the adhesive from the dust coverage were correlated to an established percent dust coverage, these color changes were then enhanced with a selective color process.  The information from the foam witness plates and the colorized dust coverage was overlaid onto virtual 3-dimensional models of the lander to produce maps that indicate more or less favorable locations for systems and payloads and needed ejecta shielding.

Tests were conducted using different engine thrusts during simulated lift-offs.  The test results and general recommendations for lander design, operation, and payload placement were presented in the discussion and conclusions.

While this paper is primarily concerned with small, single-engine landers, the same methodologies can be applied to multi-engine landers.  For all sizes of landers, this method of testing can be a useful step in finalizing lander designs and enable more effective use of expensive testing in facilities such as large vacuum chambers.

Presenting Author: Vincent Roux Saint Martin's University

Authors:

Vincent Roux Saint Martin's University
Shawn Duan Saint Martin's University