Method for calculating spacecraft longitudinal motion parameters during landing on the surface of a small celestial body

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METHOD FOR CALCULATING SPACECRAFT LONGITUDINAL
MOTION PARAMETERS DURING LANDING ON THE SURFACE
OF A SMALL CELESTIAL BODY
V.P. Kazakovtsev, Chen Danhe , V.V. Koryanov
Bauman Moscow State Technical University, Moscow, Russian Federation
e-mail: ;
The article describes a method for calculating longitudinal motion parameters of a
spacecraft during landing on the surface of a small celestial body. The method takes
into consideration the reaction applied to the movable legs from both the surface soil
and operation of the thrusters. The article discusses application of the method for
dynamic analysis of the spacecraft motion during its landing on the surface of the
Moon, taken as an example. In case of the vertical landing, the optimal value of the
force in shock absorbers is selected, which makes it possible to obtain reasonable
angles of struts after the landing with moderate forces of soil response on the legs.
The authors estimate the impact of the angular orientation of the spacecraft relative
to the Moon’s surface on the change of the legs position, as well as the impact of
soil response normal forces on the legs, and shock absorbers deformation during
landing. The article contains graphs of the spacecraft longitudinal and vertical
velocities, which are calculated considering the influence of legs motion during the
non-simultaneous contact with the soil.
Keywords: landing on small celestial bodies, method for dynamics analysis of
spacecraft motion, evaluation of influence of disturbing factors, conditions for safe
landing.
The program of research into different celestial bodies of the solar
system implies spacecraft flights to these bodies in the coming decades. In
some cases, gathering information about a celestial body implies landing
of a spacecraft on the surface of the body.
Small celestial bodies without atmosphere and with a sufficient
gravitational field are of particular interest. The bodies of this type are
asteroids such as Ceres, Pallas, and other satellites of the planets (the Moon
near the Earth, Io and Europa near Jupiter, etc.).
At the conceptual design stage of a spacecraft, designed to landing
on the surface of a small celestial body, there is a need in a method
for calculating spacecraft motion parameters and estimating loads on the
landing gear. The method would allow determining the main characteristics
of the landing gear and parameters of the shock absorbers, as well as
estimating the conditions of a safe landing on the surface of a small celestial
body.
The previous publications [1–6] showed that during landing on the
surface of the Moon, the most dangerous case is a longitudinal motion of
the spacecraft with a lateral velocity component when one landing gear
leg is touching an ascending slope of the surface. Therefore, the method
for calculating landing parameters during the longitudinal motion of the
spacecraft can be used at the early stages of the project definition phase.
26 ISSN 0236-3941. HERALD of the BMSTU. Series “Mechanical Engineering”. 2014. No. 1