Title: Reentry Guidance for Generic RLV Using Optimal Perturbations and Error Weights AIAA20056438
1Reentry Guidance for Generic RLV Using Optimal
Perturbations and Error Weights (AIAA-2005-6438)
- Dr. Ashok Joshi K. Sivan
- Department of Aerospace Engineering,
- IIT Bombay, Mumbai, India
AIAA Guidance, Navigation Control Conference,
Hyatt Regency San Francisco, 15-18 August, 2005
2Motivation
Reentry problem is important from the following
view points Dissipation of large energy without
violating constraints Large variations in
atmospheric/vehicular characteristics Highly
uncertain operational environment
3Current Status Needs
- Current Flight Proven Methods (Space Shuttle
HYFLEX) - Pre-computed drag acceleration profile
within corridor - In-flight updating to meet range-to-go
requirement - Bank angle to meet terminal range requirements
- Future Reentry Guidance Requirements
- Autonomous for providing mission
flexibility/adaptability - Explicit satisfaction of vehicle constraints
- No ground computations and mission
independent - Robust against large uncertainties
4Implementation Strategies
- Predictor-Corrector as the most suitable for RLV
applications - Models the vehicle environment as close to
the reality - Autonomous adaptable to different flight
conditions - Ground computations not required
- Aim of present study to make predictor-corrector
more effective - Judicious selection of control vector for
easy solution - In-flight measurements for improving
predictor model - Correct perturbation levels for sensitivity
computation - Weighting option for control vector update
- Explicit inclusion of path constraints
5Guidance Problem Definition
- Given Estimate u(t) subject to
- so that at tf, terminal constraints
is satisfied - without violating path constraints
-
-
-
6Overall Solution Methodology
Predictor
Corrector
7Control Vectors Range
Terminal constraint through definition of
Downrange Crossrange
8Predictor Algorithm
9Corrector Algorithm
10Computation Of Jacobian
Correct Sensitivity depend on proper
perturbation levels Present Study Required
perturbation level computed on ground
stored as function of VR
11Typical Dataset for Validation
- Nominal Reentry Interface
-
- h 120 km, f 0o, l 0o
- V 8086 m/s, g - 3.2o, Az 100o
- Target (at 25 km)
-
- f - 18o, l 45.3o
-
12Constraints Procedure
13 Perturbation Levels/Sensitivities
Range Sensitivities
Perturbation Levels
14Heat Rate Constraint Results
Heat Flux Profile
Range Profile
Control Vectors
15Heat Flux Glide Results
Heat Flux Profile
Range Profile
Control Vectors
16Results With CD Variations
Range Profile
Control Vectors
17Results With CL Variations
Range Profile
Control Vectors
18Summary
A modified Predictor-Corrector algorithm
presented Incremental angle of attack as
additional control vector Weighting matrix
for control vector correction More
appropriate perturbation parameter selection
Heat rate and equilibrium glide as explicit
constraints Strategy validated and robustness
demonstrated The proposed algorithm applicable
to wide variety of winged Vehicle configurations
RLV missions