Space Travel:

Mathematics Uncovers an Interplanetary Superhighway

Possible Future Mission Trajectories

Lunar L₁ Gateway Station

A metro map representation showing hubs connected by gravitational passageways in the near-Earth neighborhood and beyond. More...

Let's say NASA desires to develop a robust and flexible capability to visit several potential destinations. The figure shows in "metro map format" some connections between hubs in Earth's neighborhood and beyond. It has been recognized that in addition to orbits around planets, orbits around the Lagrange points L₁ and L₂ in both the Sun-Earth and Earth-Moon system are important hubs and/or destinations.

In fact, the fortuitous arrangement of natural gravitational passageways in near-Earth space implies that Earth-Moon L₁ and L₂ orbits are connected to orbits around the Sun-Earth L₁ or L₂ via natural low-fuel pathways. A future Lunar L₁ Gateway Station at the Earth-Moon L₁ Lagrange point (between the Earth and Moon) has been proposed as a transportation hub beyond low-Earth orbit. Future deep space telescopes could be built in the micro-gravity environment of the Station and may be built in a lunar L₁ orbit and conveyed to the deep space environment of the Sun-Earth L₂ point with minimal fuel requirements.

The station would also be an excellent staging area for other deep-space missions, human or robotic, to the asteroids, Mars, giant planets, and beyond.

Multi-Moon Orbiters of Jupiter's Icy Moon

There has been much recent interest in sending a spacecraft to perform extended observations of several of Jupiter's moons. Europa is thought to be a place hospitable to life because of the vast, liquid oceans that may exist under its icy crust. Two other Jupiter moons, Ganymede and Callisto, are now also thought to have liquid water beneath their surfaces. A proposed mission to Europa, and perhaps also Ganymede and Callisto, would attempt to map these regions of liquid water for follow-on missions.

A "Petit Grand Tour" of the Jupiter moon system is shown in the animations. This is an example of a multi-moon orbiter mission in which a single scientific spacecraft orbits several moons of Jupiter (or any of the outer planets' moons). Using this approach, long duration observations are possible instead of flybys lasting only seconds. A multi-moon orbiter could orbit each of the planet-sized moons of Jupiter--Callisto, Ganymede, Europa, and Io--one after the other, using a technologically feasible amount of fuel.

Petit Grand Tour trajectory		Petit Grand Tour trajectory seen projected onto the orbital plane of Europa and Ganymede		Ganymede loop-de-loop		Europa orbit insertion