I thought I knew all about the Lagrange points, but then JWST took up an orbit around what was supposed to be an unstable one, and all I thought I knew went out the window.
> Webb will need to conduct occasional small thruster burns for "station keeping" and "momentum management" to retain its proper location and orientation in space.
> should have enough propellant to allow support of science operations in orbit for significantly more than a 10-year science lifetime
https://www.space.com/james-webb-space-telescope-fuel-lifeti...
* escape from the solar system altogether? That requires a big change in velocity, about half as much again as what it took to get to its current orbit.
* chuck it into the sun? needs more change than escaping the solar system
* or just a different orbit to the current one with less chance of being inconvenient? then you may as well leave it where it is - there are already a bunch of Earth Trojan asteroids around the Lagrange points which pose a similar likelihood of becoming inconvenient and being much bigger pose a greater hazard.
In this case "outside of the Earth-moon system" is what I mean. As you say, other changes such as out of solar system or into sun will require massive changes in velocity.
In most cases "out of their original Low Earth orbit" is a good definition, but unusually, JWST isn't in LEO to start with. Most satellites can be easily or no-cost de-orbited (chuck it into the earth's atmosphere, allow the orbit to decay until same) from LEO, but with the JWST, I would guess that that would also be expensive.
There was a project and/or company that was looking into building a spacecraft that could make its way to geostationary satellites about to retire, latch onto them (by putting a docking rod into their exhaust for example) and act as its new engine, to extend their lifespans. Which is neat, and even though they may be 20-30 years old, they're still antennas that can transfer data around.
>Although the L4 and L5 points are found at the top of a "hill", as in the effective potential contour plot above, they are nonetheless stable. The reason for the stability is a second-order effect: as a body moves away from the exact Lagrange position, Coriolis acceleration (which depends on the velocity of an orbiting object and cannot be modeled as a contour map)[20] curves the trajectory into a path around (rather than away from) the point.[20][22] Because the source of stability is the Coriolis force, the resulting orbits can be stable, but generally are not planar, but "three-dimensional": they lie on a warped surface intersecting the ecliptic plane. The kidney-shaped orbits typically shown nested around L4 and L5 are the projections of the orbits on a plane (e.g. the ecliptic) and not the full 3-D orbits.
People don't choose adversity, they only like to dispense it.
Simulation is fun, it's a safe way of exploring danger.
However the hazards up on hills are more typically those of exposure, altitude and isolation, not incoming gravitationally-propelled objects.
"We don't."
In any case, it's not perfectly stable. Occasional perturbations are bigger than the energy needed to leave. So, things put there don't stay long without help.