Pre-Phase A Report - Lisa - Nasa

146 Chapter 7 Spacecraft Design
Figure 7.3 LISA spacecraft attached to the solar electric propulsion module.
engine is for redundancy and balances the launch load.
For attitude and small orbit trimming manoeuvres, a monopropellant hydrazine system
is provided. It is a simple blowdown system with one tank and four 4.45 N and four 0.9 N
thrusters, requireing about 5 kg of hydrazine.
The propulsion module structure consists of a 1800 mm diameter central cylinder and two
interface rings for the separation system. The total height of the PM is 400 mm . The
cylinder is constructed as a Carbon Fibre Reinforced Plastic (CFRP) honeycomb structure
with a total thickness of 20 mm . The interface rings are made from aluminium.
The total nominal power provided is about 500 W. For initial acquisition, emergencies and
peak power demand, two non-rechargeable batteries are included. Also the pyro firing
currents for the RCS pyro valves and separation pyro’s are provided from the batteries
via a pyro electronics unit.
For initial rate reduction and during orbit manoeuvres, rate sensors are desirable. The
PM therefore also accommodates two Inertial Reference Units (one redundant) and their
electronics.
The total dry mass of the Propulsion Module is 131 kg. Mass and power budgets are given
in Section 7.4 .
7.1.3 Composite
Each of the three composites (Figure 7.3) consists of a propulsion module with a spacecraft
mounted on top. The total composite dry mass is 333 kg.
3-3-1999 9:33 Corrected version 2.08