Optimal Leg Height of Landing Legs to Reduce Risk of ‎Damage from Regolith Ejecta by Retrorocket Exhausts

Abstract

Over the past decade, there has been a rapid increase in rocket launches. 2022 was a record-breaking year for the ‎aerospace industry, with 180 successful rocket launches into orbit, 44 more than the previous year. Reducing as ‎many risks as possible is essential as interplanetary rocket launches and reusable booster landings become more ‎frequent. One such risk occurs when a rocket/booster lands. During the landing process, the retrorockets spray debris ‎from the loose ground, which may damage the rocket/landing module. Retrorockets are rocket engines that provide ‎a thrust opposing the spacecraft’s motion, causing it to decelerate. This paper studies the effect of landing leg height ‎on ejecta velocity, the volume of debris ejected, and ground surface temperature change.  Four landing leg heights ‎were tested with an Estes® E-16 consumer model rocket motor: 0 mm, 50 mm, 75 mm, and 100 mm. The ‎experiment suggests that the optimal height above the ground’s surface for a simulated landing module based on ‎the volume and velocity of the ejecta is 50 mm. Landing legs that elevate a model rocket this height create an ‎average crater volume of 610.5 mL and a max crater diameter of 10.34 cm. After determining the optimal height, a ‎landing leg system was developed. This system was attached to an Aerodactyl TS® model rocket and utilized ‎landing legs that elevated the rocket to a height of 50 mm above the ground at landing.‎‎