The Crazy Lune

			The Crazy Lune

Power System

VES-180

Power System

Batteries are the primary storage component of the power delivery system for the Astronaut to RFID Communication Link. The batteries chosen for this application are Saft VES 180 (Very high specific Energy Space cell) which are space certified lithium-ion batteries. These battery systems are modular and scalable which gives us a lot of flexibility.

Lithium-ion batteries have one of the best energy to weight ratios and a slow loss of charge rate. We assume that the Astronaut will carry out his expeditions at night and these batteries can be recharged with the solar panels during day when there is an abundance of sunlight.

Some essential features of the Saft VES 180* Batteries are:

Figure 1. Saft VES 180 Battery

Li-Ion space technology
specific energy: 175 Wh/kg
Wh/kg, storage: 180 Wh each
Nominal capacity at C/1.5 rate: 50 Ah (4.1 V/3 V & 20°C)
Maximum discharge current at 25°C: 100 A (Continuous ~2 s pulse)
GaInP2/GaAs/Ge, BOL power: 289 W/m2
BOL efficiency: 22.5%
EOL power: 256 W/m2, 4%
Ideally suited to meet intensive charge/discharge cycles
Long life: 5 years storage,2 years integration and 18 years in orbit

The calculation for the number of batteries required to meet the storage requirements is shown below:

Where,

BR= 175 W-Hr ; Battery rating in Watt-Hour

PTAR= 65 W ; Transmission Power from Astronaut to RFID Tags

T1sec= 0.01 ; Duration of transmission in one second

nsec=1 ; Number of transmissions per second

ή = 22.5% ; Battery Efficiency

Ttotal= 10 Hours ; Total time period for which the system will work

PTAL= 5 W ; Power required for Astronaut-Lander Link

The total capacity of power required by for the Moon Walk will require lower than two Batteries. Hence, we will use two batteries to support both of the astronaut's communication links. However,the batteries must be heated to operate within the operating range of 0°C to 45°C.

Tuesday, December 8, 2009