Objectives: Expected Significance to NASA

Waveriders/Gliders: The Next Critical Step. Waveriders or gliders, such as the X- 43A, offer the potential for significant improvement in performance, reliability, flexibility, and cost with respect to the state-of-the-art (SOA) [4].

• Performance: Improved Lift-to-Drag Ratio. When properly designed to “ride” the oblique shock wave that they produce, waveriders can yield unprecedented lift-drag ratios, greater range, and substantial improvement over the state-of-the-art.

• Reliability, Flexibility, Cost. Next Generation Launch Technology Program (NGLTP) studies show that (i) current state-of-the-art reliability for launch vehicles is approximately 1 in 50 [4] (or 2% loss) for expendable launch vehicles and that (ii) air-breathing propulsion offers improved reliability over rocket-based propulsion [4]. Air-breathing propulsion also offers more flexibility and lower cost per pound to orbit [11], [18], [21], [36]-[42].

Consequently, waveriders represent the next critical step toward reusable air-breathing Highly Reliable Reusable Launch Systems (HRRLS), High Mass Mars Entry Systems (HMMES), global reach vehicles, and quick, reliable, cost-effective space access (e.g. two-stage-to-orbit).

Focus and Control Challenges. The focus of the proposed “advanced adaptive control initiative” [2] is on the development of a systematic design methodology for the development of hierarchical control (Hi-C) systems for unpowered and powered hypersonic lifting-body waveriders/gliders such as the X-43A [5]-[21], X-51A (2010), and SOAREX (Sub-orbital Aerodynamic Re-Entry EXperiment, 2008, 2010; unpowered) [4] as depicted within Figure 1.

Figure 1: Targeted Waverider/Glider Vehicle Types: X-43A (top), SOAREX (bottom left), X-51A (bottom right) - NASA DFRC

Challenges and Issues. Critical challenges for these vehicles include:

Because of the above formidable challenges, the following are relevant concerns to NASA:

Main Objectives of Proposal. Given the above, the main objectives of this proposal are as follows:

Proposed Work. To address the above, the proposed work will address modeling, analysis and design as follows:

• Modeling. Aero-thermo-elastic-propulsion modeling [28]-[42] will focus on uncertainty characterization based upon first principles, finite-element analysis, as well as available data (e.g. X-43A flights [5]-[21], 2008 SOAREX flight, wind tunnel, computational fluid dynamics (CFD) and finite-element analysis (FEA)). The latter will facilitate interaction and future knowledge exchange between control system and aero-thermo-elastic-propulsion researchers.



• Analysis. Analysis will focus on determining worst-case operational scenarios and assessing fundamental performance limitations [216] in order to develop reasonable specifications.



• Design. Control system design will rely on four tools:
  
  
  1. Classical Sequential Loop Closing [223] (as was done on X-43A [6]-[7]) which will be used as the starting point and will provide insight for the selection of design parameters associated with our modern approaches (2)-(4),
  
  
  
  2. Modern Gain Scheduling based upon the quasi-linear parameter varying (LPV) framework [61]-[80] which directly exploits the nonlinear characteristics of the system and for which efficient convex optimization algorithms exist,
  
  
  
  3. Constraint Enforcement Methods [187]-[199], [213] will be used to ensure that critical variable constraints are enforced (e.g. Mach number and angle-of-attack for scramjet propulsion efficiency [11], [18], [21], [36]-[42]),
  
  
  
  4. Generalized Predictive Control (GPC) [171]-[184] which uses optimization and (in principle) can do both (2) and (3).

Deliverables, Collaborations, and SOAREX 2010 Milestone. The above will result in interactive modeling, analysis, and design software modules that will be delivered to NASA in a timely manner in order to meet the following important milestone:

SOAREX 2010 unpowered aero-controlled glide.

Efforts will also focus on developing modeling, analysis, and design tools in a timely manner so that the Advanced Control Methods team can apply the tools to data gathered from the planned 2008 SOAREX flight. The PI will work closely with two collaborators/consultants who are experts in the field as well as with NASA advance control personnel. Over the proposed 3 year grant period, the PI will facilitate collaboration with NASA by spending 1.5 months each summer at the NASA Ames Research Center (ARC, Dr. Marcus Murbach, lead on Advanced Control Methods).