Orbital Pegasus - Manual (Page 65)

Release 7.0 Apr 2010 54
Pegasus User’s Guide
Figure 8-2. Documentation Required by Orbital
for Commercial Pegasus Launch Services
8.2. Mission Planning Documentation
The available Pegasus documentation includes a
collection of formal and informal documents
developed and produced by Orbital. The number
of separate formal documents required for a
successful mission has been minimized by
consolidation of documents and maximizing the
informal exchange of information (e.g., working
groups) before inclusion on formal, controlled
configuration documents such as the payload ICD.
8.3. Mission-Unique Analyses
Mission analysis, which includes trajectory/GN&C
analyses and environment analyses, begins
shortly after mission authorization is received.
Orbital first generates an optimal trajectory design
to the desired target orbit, and this design is then
used to develop the MDL which contains all
mission sequencing, guidance, and autopilot
inputs required for the mission. The MDL, in
conjunction with the Orbital-developed Non-Real-
Time Simulation (NRTSIM), a high-fidelity 6DOF
simulation, is then subjected to a suite of tests
designed to verify robust autopilot stability margins
and compliance with all mission-specific
requirements.
8.3.1. Trajectory Analysis
Orbital performs Preliminary and Final Mission
Analyses using POST and the NRTSIM 6DOF
analysis tool. The primary objective of these
analyses is to verify the compatibility of the
payload with Pegasus and to provide succinct,
detailed mission requirements, such as payload
environments, performance capability, orbit
insertion accuracy estimates, and preliminary
mission sequencing. Much of the data derived
from the Preliminary Mission Analysis is used to
verify or refine ICD requirements and perform
initial range coordination.
Orbital also performs recontact and relative motion
analyses for post-separation events to determine if
a C/CAM is required. The analyses verifies that
sufficient separation distance exists between the
payload and final Pegasus stage following payload
separation and includes effects of separation
dynamics and of residual motor thrust.
8.3.2. Guidance, Navigation, and Control
Analyses
These consist of several separate detailed
analyses to thoroughly evaluate the planned
mission and its effects throughout powered flight.
The trajectory design, guidance, stability, and
control analyses result in a verified mission-unique
flight software MDL.
Guidance Analysis — Pegasus dispersions and
injection accuracies are determined using
predicted dispersions for motor performance,
mass uncertainties, aerodynamic characteristics,
and INS performance. These dispersions are
simulated to obtain estimated variability in perigee,
apogee, inclination, and argument of perigee at
orbit insertion. This data is incorporated in the
payload ICD.
Stability and Control Analysis — Using the
optimum trajectory from POST, Orbital selects a
set of points throughout Stage 1 burn for
investigating the stability characteristics of the