Leonard David's INSIDE OUTER SPACE

Credit: Colorado School of Mines/Center for Space Resources/LILL-E Pad Team

GOLDEN, Colorado – Work is underway on a Lunar In-situ Landing/Launch Environment (LILL-E) Pad.

Analysis of Apollo mission video footage has shown that rockets will erode lunar regolith beneath landing vehicles by ejecting material at high speeds away from the rocket plume. In the Moon’s vacuum environment, this material will speed away on a ballistic trajectory for great distances. The resulting blast effect can sandblast surfaces of equipment, including the lander itself. Moreover, this issue is expected to be severe with 21^st century lunar landing systems due to their larger sizes.

Quantities of lunar dust being displaced by Apollo 15’s Falcon’s lunar lander exhaust.
Source: Apollo 15 landing video, converted by Gary Neff

For example, the Apollo Lunar Module (LM) mass was 5 metric tons, but the Artemis Human Landing System (HLS) is planned to be considerably larger at 40 metric tons.

LILL-E Pad is one of the awardees of the 2021 NASA BIG Idea Challenge on Dust Mitigation Technologies for Lunar Applications – a concept of the Colorado School of Mines with Texas-based startup ICON, along with Masten Space Systems and Adherent Technologies Inc.

The LILL-E Pad approach addresses landing dust prevention and mitigation on the Moon by developing a binder-regolith reinforced surface (making use of lunar topside material) and a landing/launch pad that’s made out of a carbon fiber fabric barrier anchored to the lunar surface.

Credit: Colorado School of Mines/Center for Space Resources/LILL-E Pad Team

Simple solution

“Large scale landing pad concepts using 3D printing and sintering systems have been proposed for future lunar outposts, but our proposed system provides a simple solution that could be implemented by 2026,” a team write-up explains.

Due to the high temperatures of direct rocket plumes hitting the lunar landscape, the central landing pad material will need to resist temperatures ranging from 3,000-4,000 °C. This material needs to also block most gas intrusion and be high strength in order to resist the force of the HLS as it lands and rests on the pad. Several materials were considered for this application, and carbon fiber fabric was determined to be the best type for this use, the team points out.

LILL-E Pad is a two-part arrangement that includes the POlymer Nozzle Distribution (POND) area that is made of polymer-hardened regolith using a binder distribution system, plus a central carbon fiber fabric Landing/Launch Pad (LLP) – the central landing “bullseye” — that will resist the most extreme area of the rocket plume.

The system is being designed to be deployed via autonomous, robotic operations.

Rocket engine plumes impinge upon the surface as landers touch down, creating craters, kicking debris and dust far away from the landing spot, and impacting the environment and spacecraft on multiple levels.
Credit: Masten Space Systems

Blaze the trail

“Overall the team is planning on spending the next semester on finalizing our design and doing initial testing,” explains Bailey Burns, the Systems Engineering Integration and Test Lead. “Our next milestone is a deliverable for NASA in May and we hope to have our polymer base – POND — design/analysis fleshed out and thermal load and vacuum chamber testing on the carbon fiber barrier done by then,” she told Inside Outer Space.

 “Later this year, our plan is to do an engine test partnered with Masten Space Systems so this semester will be our opportunity to conduct preliminary testing before that event.” Burns adds. The team will be using Masten Space Systems’ Plume Surface Interaction (PSI) test gear in Mojave, California. It includes an oxygen/methane rocket, along with data acquisition equipment for pressure and temperature, multiple video and photo cameras, a LIDAR scanner, and a thermal camera.

Credit: NASA

The team notes that, while laboratory testing has shown promise, there are still many unknowns, such as mixing/wetting mechanics, regarding the introduction of the LILL-E Pad system to a lunar environment. Additionally, temperatures at the lunar south pole will affect how materials respond to forces and how they may deteriorate over time.

The Center for Space Resources at the Colorado School of Mines has a number of available tools for the LILL-E Pad work, such as vacuum chamber test gear and a 12’x8’x2’ Lunar Testbed that is filled with JSC-1 – a lunar simulant.

 “We are really proud of the realistic feasibility of this project and hope our research can help blaze the trail for sustainability in future lunar missions,” Burns concludes.