Wyatt Johnson

The Morpheus Lander is a vertical takeoff and landing test bed vehicle developed to demonstrate the system performance of the Guidance, Navigation and Control (GN&C) system capability for the integrated autonomous landing and hazard avoidance system hardware and software. The Morpheus flight control system design must be robust to various mission p...

Two piloted simulations were conducted at NASA's Johnson Space Center using the Cooper-Harper scale to study the handling qualities of the Orion Crew Module capsule during atmospheric entry flight. The simulations were conducted using high fidelity 6-DOF simulators for Lunar Return Skip Entry and International Space Station Return Direct Entry flig...

Mars landers have been able to land only within tens to hundreds of km of a target site due to uncertainties in approach navigation, atmospheric modeling, and vehicle aerodynamics; as well as due to map-tie error and wind drift. The Mars Science Laboratory mission will improve this to 5 - 10 km using optical navigation and entry guidance. To achiev...

The automation of a Mars aerobraking vehicle that uses reaction wheels for attitude and angular momentum control during atmospheric flythrough is investigated. In a previous study, single-axis control laws were developed for minimum onboard instrumentation to compensate for large variations in entry time and atmospheric density. Modifications of th...

Aerocapture using a towed, inflatable ballute system has been shown to provide signifi-cant performance advantages compared to traditional technologies, including lower heating rates and accommodation of larger navigational uncertainties. This paper extends previous results by designing a ballute aerocapture separation algorithm that can operate in...

Using an inflatable ballute system for aerocapture at planets and moons with atmospheres has the potential to provide significant performance benefits compared not only to traditional all propulsive capture, but also to aeroshell based aerocapture technologies. This paper discusses the characteristics of entry trajectories for ballute aerocapture a...

SIM (Space Interferometry Mission) is a mission scheduled to launch in 2010 and will be the first spacecraft to use interferometry to measure the positions of stars to within 1 micro-arcsecond - a degree of precision never before achieved in space. The flight hardware required to achieve this level of precision is very sensitive to its external env...

The equations of motion for an aerobraking spacecraft are nondimensionalized. This process yields three dimensionless parameters that intrinsically describe the capability of a reaction-wheel controller to manage angular momentum during an atmospheric drag pass. These parameters, namely aeromoment, desaturation speed, and equilibrium momentum, comp...

Conventional aerobraking requires propellant to dump the spacecraft's angular momentum and to maintain attitude control during the atmospheric flythrough. We consider how reaction wheels can be used to control the spacecraft's pitch during each atmospheric flythrough and to reduce angular momentum simultaneously. Control laws are developed for mini...

We investigate the automation of a Mars aerobraking vehicle that uses reaction wheels for attitude and angular momentum control during atmospheric flythrough. In a previous study, single-axis control laws were developed for minimum onboard instrumentation to compensate for large variations in entry time and atmospheric density. In this paper we tes...

Aerogravity-assist trajectories are optimized in the sense of maximizing DeltaV obtained by the flyby, maximizing aphelion, minimizing perihelion, and minimizing the time of flight for a particular destination planet. A graphical method based on Tisserand's criterion is introduced to identify potential aerogravity-assist trajectories. To demonstrat...

An aeroassisted mission uses atmospheric forces to effect a spacecraft delta-V, which could allow for substantial propellant savings. This research focuses on aero-maneuvers useful for interplanetary flight. The aerogravity assist maneuver uses aerodynamic lift to achieve a greater delta-V than with gravity alone. Aerobraking and aerocapture both u...

In this paper we investigate using bank modulation of a lifting body to capture a spacecraft into orbit in a single atmospheric flythrough. Aerocapture without lift is difficult to achieve because ballistic flythroughs are highly sensitive to the atmospheric entry angle. Lifting bodies are more robust and provide a simple means of control through b...

In this paper, we find the optimal atmospheric trajectories for a spacecraft dur-ing an aerogravity-assist (AGA) maneuver. These trajectories are optimal in the sense that departure V ∞ is maximized, with a given atmospheric turn angle constraint. The trajectories are found by using the Euler-Lagrange equations, setting up the necessary conditions,...