TITLE:
Automatic Approach and Landing Trajectory Planner for Unpowered Reusable Launch Vehicle
AUTHORS:
Fawaz F. AL-Bakri, Craig A. Kluever
KEYWORDS:
Entry Vehicle, Guidance System, Trajectory Planning
JOURNAL NAME:
Advances in Aerospace Science and Technology,
Vol.2 No.4,
December
7,
2017
ABSTRACT: A new guidance scheme for the approach and landing (A & L) phase of an
unpowered reusable launch vehicle (RLV) has been developed. The main advantage
of the new guidance is the use of glide-efficiency factor as the independent
variable to compute the geometrical flare parameters by a set of analytical
functions. The trajectory-planning algorithm generates its reference
geometry based on the steep and shallow subphases, respectively. During the
steep segment, the quasi-equilibrium glide (QEG) solution, which assumes a
constant dynamic pressure and flight-path angle during the flight, is used to
create the flight reference while the shallow segment is defined by polynomial
functions for altitude and dynamic pressure profiles. Standard linearization
methods are used to design a closed-loop command in order to track the QEG
profile. Furthermore, proportion-derivative (PD) control is used to modulate
the lift coefficient during the flare flight. Once the reference trajectory is
created, a closed-loop simulation is obtained to track the reference. Off-nominal
conditions, in terms of change in initial glide-efficiency factor, dynamic pressure,
flight-path angle, and altitude are tested using a Monte-Carlo simulation.
The simulated results demonstrate the effectiveness of the proposed algorithm
to land the vehicle successfully under large dispersions of glide-efficiency
factor.