LANDING STATION & PROPULSION

Lander Propulsion

THRUSTERS

The function of the propulsion system is separated into two main functions. Translation thrusters and altitude control thrusters. For altitude control 4 pairs of thrusters were used. To maximize the torque the thrusters need to be place as far away from the center of mass as possible. The two set of thrusters are placed in opposite corners at the bottom layer as shown if Figure 2. Eight thrusters give 3-axis control in its orientation. A larger center translation thruster at the bottom is used to boost the lander as well as perform power-braking when landing on the moon.

Fuel

With multiple thrusters needed liquid fuel propulsion is chosen since it can easily be pumped to the peripheral thrusters from a central system. N₂O₄(Nitrogen Tetroxide) is used as the oxidizer and MMH (monomethyl hydrazine) for the propellant. Four spherical tanks with radius of 0.62m would be used to store the fuel. Helium gas pressure and valves are used to drive the flow of the liquid propellant to the thruster chambers as shown in Figure1.

Figure 1: Propulsion System Overview

Figure 2: Thruster location

Altitude Control

The altitude control system provide thruster firing commands for station keeping, control solar arrays and antenna orientation. Star scanner systems CT-632 from the Ball Aerospace Systems Division will be used for altitude control. The cost of a commercial one is approximately $500,000. To reduce the cost designing of altitude control system from sun sensors may be considered. More information on the CT-632 can be found HERE.