Engineering topics

Longuski, James M.

Publications and source records attributed to Longuski, James M..

10 records

NASA NTRS2015

Orbit Stability of OSIRIS-REx in the Vicinity of Bennu Using a High-Fidelity Solar Radiation Model

Solar radiation pressure is one of the largest perturbing forces on the OSIRISRex trajectory as it orbits the asteroid Bennu. In this work, we investigate how forces due to solar radiation perturb the OSIRIS-REx trajectory in a high-fidelity model. The model accounts for Bennu's non-spherical gravity field, third-body gravity forces from the Sun and Jupiter, as well as solar radiation forces acting on a simplified spacecraft model. Such high-fidelity simulations indicate significant solar radiation pressure perturbations from the nominal orbit. Modifications to the initial design of the nominal orbit are found using a variation of parameters approach that reduce the perturbation in eccentricity by a factor of one-half.

Williams, Trevor W.↗

NASA NTRS2005

A Dual-Use Ballute For Entry And Descent During Planetary Missions

An inflatable ballute system for aerocapture at the atmosphere-bearing planets and at Titan may provide significant performance benefits, compared to conventional propulsive capture and aerocapture technologies. Ballute simulations to date release the ballute at the appropriate instant and then ignore it to focus on the trajectory of the orbiter. The latest concept, which we pursue in this paper, is to employ the ballute to soft-land a small payload. Thus the same ballute can provide two uses (1) aerocapture of the orbiter and (2) soft-landing of the lander package, hence the term dual-use ballute. The dual-use ballute concept has the potential to dramatically alter the way we approach exploration of the atmosphere-bearing bodies in the Solar System. Cases investigated here include aerocapture and soft-landing at Mars, Titan and Neptune.

Medlock, Kristin L.↗

NASA NTRS2001

The Feasibility of a Galileo-Style Tour of the Uranian Satellites

Gravity-assist trajectories have been a key to outer Solar System exploration. In particular, the gravity-assist tour of the Jovian satellites has contributed significantly to the success of the Galileo mission. A comparison of the Jovian system to the Uranian system reveals that the two possess similar satellite/planet mass ratios. Tisserand graphs of the Uranian system also indicate the potential for tours at Uranus. In this paper. We devise tour strategies and design a prototypical tour of the Uranian satellites, proving that tours at Uranus are feasible.

Heaton, Andrew F.↗

NASA NTRS2000

Automated Design of the Europa Orbiter Tour

In this paper we investigate tours of the Jovian satellites Europa Ganymede, and Callisto for the Europa Orbiter Mission. The principal goal of the tour design is to lower arrival V_ for the final Europa encounter while meeting all of the design constraints. Key constraints arise from considering the total time of the tour and the radiation dosage of a tour. These tours may employ 14 or more encounters with the Jovian satellites. hence there is an enormous number of possible sequences of these satellites to investigate. We develop a graphical method that greatly aids the design process.

Heaton, Andrew F.↗

NASA NTRS1997

Mars Free Return Trajectories

For human missions to Mars, the top priority is a safe return of the crew to Earth. In the case of an emergency, trajectories that naturally return to the Earth with no intervention are preferred. In this paper we use automated design software to compute all possible Mars Free Return trajectories form 1995 to 2020, given constraints on the total time of flight and on the launch energy. The resulting data file contains all of the previouslknown types of returns.

Mars↗

NASA NTRS1993

Cycler orbit between Earth and Mars

A periodic orbit between Earth and Mars has been discovered that, after launch, permits a space vehicle to cycle back and forth between the planets with moderate maneuvers at irregular intervals. A Space Station placed in this cycler orbit could provide a safe haven from radiation and comfortable living quarters for astronauts en route to Earth or Mars. The orbit is largely maintained by gravity assist from Earth. Numerical results from multiconic optimization software are presented for a 15-year period from 1995 through 2010.

Byrnes, Dennis V.↗

NASA NTRS1991

Automated design of gravity-assist trajectories to Mars and the outer planets

In this paper, a new approach to planetary mission design is described which automates the search for gravity-assist trajectories. This method finds all conic solutions given a range of launch dates, a range of launch energies and a set of target planets. The new design tool is applied to the problems of finding multiple encounter trajectories to the outer planets and Venus gravity-assist trajectories to Mars. The last four-planet grand tour opportunity (until the year 2153) is identified. It requires an earth launch in 1996 and encounters Jupiter, Uranus, Neptune, and Pluto. Venus gravity-assist trajectories to Mars for the 30 year period 1995-2024 are examined. It is shown that in many cases these trajectories require less launch energy to reach Mars than direct ballistic trajectories.

Longuski, James M.↗

NASA NTRS1990

Error analysis for pulsed maneuvers of a dual-spin spacecraft

The Galileo is a dual-spin interplanetary spacecraft which is scheduled for launch toward Jupiter in October of 1989. The spacecraft has twelve thrusters, located on the rotor, which can be operated in continuous or pulsed modes. In this paper probabilistic error models are presented for the pulsed maneuvers which are used to change the spacecraft's velocity. These models take into account all error sources which might affect the maneuver accuracies, such as wobble, nutation, plume impingement, thrust level variation and misalignment, gyro drift, burn timing errors and mass property uncertainties. The analytic models are sufficiently general so that they may be applied to all spin and dual-spin stabilized spacecraft. When these models are applied to the case of the Galileo spacecraft, the numerical results demonstrate that the spacecraft can achieve the maneuver accuracies required in order to successfully reach Jupiter and perform its scientific mission.

Longuski, James M.↗

NASA NTRS1990

Automated design of multiple encounter gravity-assist trajectories

Given a range of initial launch dates and a set of target planets, a new approach to planetary mission design is developed, using an automated method for finding all conic solutions. Each point on the diagrams reproduced represents a single ballistic trajectory and is computed by modeling the trajectory as a conic section and solving the corresponding Lambert problem for each set of launch and arrival dates. An example which prescribes a launch period of 1975-2050 and target planets Uranus, Saturn, Jupiter, Neptune and Pluto is described whereby, all possible grand tour missions of this class are found, including the Voyager II trajectory. It is determined that this automated design tool may be applied to a variety of multiple encounter gravity-assist trajectories that are being considered for future missions.

Longuski, James M.↗

NASA NTRS1988

An analytic-geometric model of the effect of spherically distributed injection errors for Galileo and Ulysses spacecraft - The multi-stage problem

In previous work the problem of injecting the Galileo and Ulysses spacecraft from low earth orbit into their respective interplanetary trajectories has been discussed for the single stage (Centaur) vehicle. The central issue, in the event of spherically distributed injection errors, is what happens to the vehicle? The difficulties addressed in this paper involve the multi-stage problem since both Galileo and Ulysses will be utilizing the two-stage IUS system. Ulysses will also include a third stage: the PAM-S. The solution is expressed in terms of probabilities for total percentage of escape, orbit decay and reentry trajectories. Analytic solutions are found for Hill's Equations of Relative Motion (more recently called Clohessy-Wiltshire Equations) for multi-stage injections. These solutions are interpreted geometrically on the injection sphere. The analytic-geometric models compare well with numerical solutions, provide insight into the behavior of trajectories mapped on the injection sphere and simplify the numerical two-dimensional search for trajectory families.

Longuski, James M.↗