Engineering topics

Allan, Brian

Publications and source records attributed to Allan, Brian.

4 records

NASA NTRS2017

Flight Dynamics of Mars Helicopter

Starting with the first attempted flybys of Mars in the 1960s, human exploration of the Red Planet has evolved through ever-more sophisticated means, with the use of orbiters, stationary landers, and more recently rovers that have traveled over distances of tens of kilometers in search of new knowledge. Yet, despite discussion since the early days of space exploration, no mission has so far attempted to unlock the aerial dimension of Mars exploration through the use of atmospheric flyers. This could be about to change, as NASA is currently considering sending a small helicopter to the Martian surface as part of a future mission, as a technology demonstration to verify the feasibility and utility of using helicopters for future Mars exploration. The use of helicopters promises to bridge a resolution gap in current Mars exploration capabilities—betweeen orbiters providing large-area imagery at low resolution, and rovers that provide detailed imagery limited by line-of-sight from the current rover location. Paired with a rover, a helicopter can act as a forward reconnaisance platform, helping to identify promising science targets or mapping the terrain ahead of the rover. Looking further ahead, helicopters may one day carry their own science payloads to areas that are inaccessible to rovers.

San Martin, Miguel↗

NASA NTRS2017

Flight Dynamics of Mars Helicopter

Helicopters have the potential to transform Mars exploration by providing a highly mobile platform for forward reconnaissance as an aid for ground-based systems. Helicopter flight on Mars is challenging due to the extremely thin atmosphere, which is only partially offset by a reduction in gravity. NASA is considering the possibility of sending a small helicopter to the Martian surface as part of a future mission. In this paper we focus on flight dynamics and controllability issues for the proposed Mars Helicopter, in particular the areas in which the dynamics departs from typical behavior on Earth. We discuss insights gained from modeling and simulation, as well as system identification performed with a test vehicle in the relevant atmospheric condition, culminating in the first demonstration of controlled helicopter flight in Martian atmospheric conditions in May 2016.

San Martin, Miguel↗

NASA NTRS2010

Optimal Flow Control Design

In support of the Blended-Wing-Body aircraft concept, a new flow control hybrid vane/jet design has been developed for use in a boundary-layer-ingesting (BLI) offset inlet in transonic flows. This inlet flow control is designed to minimize the engine fan-face distortion levels and the first five Fourier harmonic half amplitudes while maximizing the inlet pressure recovery. This concept represents a potentially enabling technology for quieter and more environmentally friendly transport aircraft. An optimum vane design was found by minimizing the engine fan-face distortion, DC60, and the first five Fourier harmonic half amplitudes, while maximizing the total pressure recovery. The optimal vane design was then used in a BLI inlet wind tunnel experiment at NASA Langley's 0.3-meter transonic cryogenic tunnel. The experimental results demonstrated an 80-percent decrease in DPCPavg, the reduction in the circumferential distortion levels, at an inlet mass flow rate corresponding to the middle of the operational range at the cruise condition. Even though the vanes were designed at a single inlet mass flow rate, they performed very well over the entire inlet mass flow range tested in the wind tunnel experiment with the addition of a small amount of jet flow control. While the circumferential distortion was decreased, the radial distortion on the outer rings at the aerodynamic interface plane (AIP) increased. This was a result of the large boundary layer being distributed from the bottom of the AIP in the baseline case to the outer edges of the AIP when using the vortex generator (VG) vane flow control. Experimental results, as already mentioned, showed an 80-percent reduction of DPCPavg, the circumferential distortion level at the engine fan-face. The hybrid approach leverages strengths of vane and jet flow control devices, increasing inlet performance over a broader operational range with significant reduction in mass flow requirements. Minimal distortion level requirements are met using vanes alone, avoiding engine stall and increasing robustness of this hybrid inlet flow control approach. This design applies to aerospace applications needing flush-mounted boundary-layer-ingesting inlets.

Allan, Brian↗

NASA NTRS2009

Development of a Large Field-of-View PIV System for Rotorcraft Testing in the 14- x 22-Foot Subsonic Tunnel

A Large Field-of-View Particle Image Velocimetry (LFPIV) system has been developed for rotor wake diagnostics in the 14-by 22-Foot Subsonic Tunnel. The system has been used to measure three components of velocity in a plane as large as 1.524 meters by 0.914 meters in both forward flight and hover tests. Overall, the system performance has exceeded design expectations in terms of accuracy and efficiency. Measurements synchronized with the rotor position during forward flight and hover tests have shown that the system is able to capture the complex interaction of the body and rotor wakes as well as basic details of the blade tip vortex at several wake ages. Measurements obtained with traditional techniques such as multi-hole pressure probes, Laser Doppler Velocimetry (LDV), and 2D Particle Image Velocimetry (PIV) show good agreement with LFPIV measurements.

Jenkins, Luther N.↗