Orbital Pegasus - Manual (Page 22)

Release 7.0 Apr 2010 11
Pegasus User’s Guide
guidance strategies that are designed and tailored
to meet specific mission objectives. These
strategies fall into several basic categories:
(1) Minimize Insertion Errors. Using this strategy,
the guidance system manages the excess
vehicle energy by implementing out-of-plane
turning during Stage 2 and Stage 3 burns as
required, and by adjusting the timing of
Stage
3 ignition. This “energy-scrubbing”
strategy results in the smallest possible
insertion errors for both apogee and perigee
altitudes.
(2) Maximize Insertion Altitude. Using this
strategy, excess vehicle performance is
conserved to maximize the altitude at
insertion. This allows the customer to achieve
the highest possible circular orbit altitude
based on the actual vehicle performance while
minimizing the eccentricity of the final orbit.
(3) Maximize Insertion Velocity. Using this
strategy, excess vehicle performance is
conserved to maximize velocity at insertion.
This allows the customer to use the excess
guidance reserve to increase the expected
apogee (non-insertion apse) altitude while
continuing to maintain a precise perigee
(insertion apse) altitude.
(4) Some Combination of (2) and (3). Options 2
and 3 represent the two endpoints of a
spectrum of potential guidance strategies that
can be combined and tailored to achieve
mission-specific guidance objectives. Both
insertion altitude and velocity may be
maximized to achieve the highest possible
Figure 3-3. Pegasus XL Without HAPS Performance Capability