M. Sarigul-Klijn

Intelligent Flight Trajectory Generation to Maximize Safe Outcome Probability after a Distress Event

A flight trajectory generation method called the distressed-aircraft-recovery technique for maximum safe-outcome probability (DART_MSOP), based on integration of three new algorithms, is developed that maximizes safe-outcome probability after a distress event by incorporating an abort airport together with a model of current aircraft dynamics. Several abort-probability models are studied under various constraints. The first new algorithm, a statistical-based initial-turn-determination algorithm, is developed to advise pilots to a reachable best landing site immediately after the distress event and before using the second new algorithm, a high-fidelity flight trajectory generation algorithm. A third new algorithm determines the flight maneuver for guidance of a perpetual-turning-attitude aircraft to fly the trajectory generated by the second algorithm. The third algorithm is only used if the aircraft has stuck controls or a similar malfunction that generates a nonzero amount of bank angle and causes the aircraft to turn only in one direction. As a three-dimensional high-fidelity algorithm, the second algorithm considers the probability of an abort to increase overall survivability by minimizing expected flight-path length as it shapes the trajectory. The performance of this new intelligent flight trajectory determination method DART_MSOP is evaluated using a case study based on a hypothetical in-flight distressed transport aircraft in northern California. Numerical simulations include variable failure rates to simulate different in-flight distress conditions, and multiple fixes along the path to accommodate realistic trajectories. DART_MSOP intelligent flight trajectory determination method should increase aviation safety if these algorithms are implemented in aircraft avionics systems.

An Approach to Predict Flight Dynamics and Stability Derivatives of Distressed Aircraft

This paper presents an approach to predict the flight dynamics and stability derivatives of a structurally damaged transport category subsonic aircraft based on a spanwise full loss damage model. Stability derivatives are derived using basic principles and theoretical aerodynamics, resulting equations are tabulated for a distressed aircraft due to wing damage. We determined two new stability derivatives based on our theoretical derivations using a wing damaged aircraft model. Our new approach and the stability derivatives derived should prove useful in the evaluation of damaged aircraft systems as well as in development of flight simulations. A case study conducted includes prediction of changes in stability derivatives and coefficients with damage parameter using a digital C-17 Globemaster aircraft model. The newly derived damaged aircraft stability derivatives are validated using C-5 Galaxy aircraft flight test data available. Results show excellent correlation.

Vibration Mitigation Using Passive Active Tunable (PAT) System: Experimental Aspects

The objective of this paper is to test and model a single-degree-of-freedom vibration isolation system with a magnetorheological (MR) foam damper under harmonic and random excitations. The results of this research are valuable for understanding the characteristics of the MR foam damper and include the experimental design and results of vibration mitigations for frequency ranges up to 2000 Hz. Transmissibility and acceleration hysteresis experiments of the MR foam damper system with different levels of input current are discussed. A simple damper design that eliminates many of the constraints normally associated with fluid filled devices is presented. Constitutive equations of the Bouc-Wen model are used to validate and characterize the MR foam damper. The motion characteristics of the MR foam damper are studied. Experimental results reveal that the mechanical behavior of the MR foam damper is nonlinear and that the field-dependent behavior of MR foam damper is associated with the applied frequency and acceleration amplitude. Experiments demonstrate MR foam damper works well in controlling vibrations and can be controlled and tuned for specific applications.

A comparative analysis of methods for air-launching vehicles from earth to sub-orbit or orbit

Abstract A variety of air-launched sub-orbital and orbital vehicles are demonstrated and others have been proposed recently by different organizations. The purpose of this article is three-fold: (a) to identify benefits of air-launching vehicles for space missions; (b) to categorize airlaunched vehicles with respect to how they are integrated to their carrier vehicle; (c) to identify benefits and shortcomings of these methods. Our analysis study shows that air-launching provides mobility and deployment advantages over surface launching. It can also provide performance advantages over surface launching. However, many air-launch concepts proposed require advance technologies that are currently not available.

A Probabilistic Algorithm in Landing Site Selection of a Distressed Aircraft Including Effects of Failure Rates

An algorithm is developed that generates statistically optimal flight trajectory to a best landing site after occurrence of an in-flight distress condition using an abort probability model. The approach developed increases overall survivability by minimizing the expected flight path distance, given the abort probability model. An airport grouping strategy that clumps the airports logically prior to path derivation is also developed. The performance of this newly developed probabilistic trajectory algorithm is evaluated using numerical simulations that include variable failure rates to simulate different in-flight distress conditions, and multiple turns to accommodate realistic trajectories. The results show that it is possible by using this algorithm to increase aircraft survivability.Copyright

A Novel Probabilistic Approach in Determination of Landing Site for Distressed Aircraft

A flight path planning strategy based on a novel probabilistic approach is proposed and developed. The main goal is to increase overall survivability of an in-flight distressed aircraft by biasing the flight path closer to possible abort airports so that in the event of an abort, the aircraft has less distance to fly to reach the abort field. Probabilistic methods are used to derive an optimal biased path and to evaluate the efficacy of such a path in improving overall aircraft survivability. Simulation results show that this novel probabilistic approach to flight path planning increases survivability of an in-flight distressed aircraft.

Universal Long Duration Tug Concept

Current plans for manned missions to Moon, Mars and beyond involve launching very large and expensive launch vehicles. An alternative is to launch several smaller tugs and have them rendezvous in Low Earth Orbit (LEO). The tugs could dock nose to tail and form a train of stages that can provide the delta V for trips to the Moon, Mars, or other planets and act as a multi-stage launch vehicle that originates from LEO. Such staging can reduce the total mass required to be lifted from the earths surface and allow international participation, risk sharing, and cost sharing in human space flight missions. The tugs could also be pre-positioned in orbit around other planets and moons and provide the delta V for the trip back to Earth. This paper describes key areas of the proposed Universal Long Duration tug (ULD-Tug) concept.

Rotary Decelerators for Spacecraft: Historical Review and Simulation Results

The concept of a rotor-equipped spacecraft for atmospheric entry can be traced back to the early years of the Space Race, in which it was proposed for an Earth-entry manned capsule. Employing an unpowered rotor in autorotation can produce lift offering increased cross-range potential, enhanced maneuverability, and “soft” landing capability. It is estimated that a rotor recovery system would account for less than 15% of the vehicle’s landing weight. A literature review addressing the advantages of rotary-type decelerators for spacecraft is compiled in this paper. First, we cover industry development of rotors for decelerating dropped cargo and feasibility studies of operation in supersonic conditions. Then, the efforts at NASA and other research partners during the 1960’s are reviewed with an emphasis on results from analytical studies and wind tunnel testing. Next, we study solutions of previously derived equations of motion for the dynamic behavior of rotor entry vehicles under variable configurations. Finally, we review more recent rotor entry, descent and landing efforts in particular: the late 1990’s Roton project and rotor systems for atmospheric descent and in-situ exploration of planetary bodies.