Trajectory Options to Pluto via Gravity Assists from Venus, Mars, and Jupiter

Abstract

Analytic and numeric techniques are used to assess trajectory options for the Pluto Express sciencecraft for a launch early in the next decade. The constraints placed on the Pluto Express trajectory for this study are severe-total ight time to Pluto of 12 years or less using a Delta-class launch vehicle. In addition, no ybys of Earth are permitted. Suitable trajectories are found with launch windows before, near, and after the date of the baseline launch. All of these trajectories take advantage of a gravity assist with Jupiter, and all use two or three gravity assists with Venus before arriving at Jupiter. In two cases, a Mars gravity assist is used in conjunction with three Venus gravity assists. Several asteroid yby opportunities are presented for the baseline mission and for a backup trajectory, which launch in March 2001 and July 2002, respectively. For example, a yby of the asteroid Seraphina (which has a radius of 32 km) can be accommodated in the baseline mission for an additional deterministic delta-velocity of 0.12 km/s, well within the capability of the system. Nomenclature C 3 = V 2 1 , km 2 /s 2 g = standard gravitationalaccelerationon the Earth, km/s 2 I sp = speci c impulse, s m f = total injected dry mass ( nal mass), kg m i = total injected wet mass (initial mass), kg m p = propellant mass, kg m s=c = spacecraft mass (excluding propellant tanks), kg R J = radius of Jupiter r po = radius of circular parking orbit, km V V = velocity of Venus with respect to the sun, km/s V 1 = hyperbolic excess velocity vector, km/s 1V = magnitude of a change in velocity, km/s or m/s 1V NAV = navigation 1V , km/s or m/s 1V PL = deterministic postlaunch 1V , km/s 1V TPL = total postlaunch 1V , km/s ¹ E = gravitational parameter of the Earth, km 3 /s 2

Trajectories for Europa Flyby Sample Return

“…Attention is restricted to the classical VEGA, VVEGA, and VEEGA sequences, since previous work has shown these to be the most effective in reaching Jupiter, including better performance than ∆V-EGA. 10 Also it is reasonable to restrict the total number of encounters to six † , based on flight time considerations. The following assumptions are made: The primary search variables are the encounter epochs, but the type of Lambert arc (number of revs and fast/slow case) are secondary search variables.…”

“…The following feasibility conditions (or constraints) are enforced: † The VVGA sequence is eliminated since it is not possible to ballistically reach Jupiter using a two-flyby sequence not involving Earth. 10 5. Radial distance at the nodal intersection of the trajectory with the Europa orbit plane (referred to as the node radius) must be close to Europa's semi-major axis.…”

A study of trajectories to the Neptune system using gravity assists

“…In this way, the geometry of the trajectory VVEJGA provides one technique to double the gravitational assistance with Venus. Sims et al (1997) analyzed several trajectories to Pluto using a gravity-assist maneuver with Jupiter. They also analyzed a gravity-assist maneuver with Mars, in conjunction with three maneuvers assisted by Venus.…”

Multiobjective Design of Gravity-Assist Trajectories via Graph Transcription and Dynamic Programming

“…In fact, approximated Δ𝑣 manoeuvres at planetary swing-bys are generally assumed and the optimization routine, usually single-objective, looks for trajectories that reduce such Δ𝑣 to a trivially small number. For example, NASA's STOUR programme [10][11][12] considers the difference between the incoming and outgoing planet-spacecraft relative velocities (in magnitude) at the planetary encounter as a measure of the Δ𝑣-cost for a given planet-to-planet phase. ESA's GASP programme [13] employs the so-called powered swing-by model [14] to link successive legs of the overall MGA mission at each planetary encounter, assuming a Δ𝑣 manoeuvre occurs at the moment of closest approach during a planetary swing-by.…”