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The L points are 'easier' but not any faster. A probe at an L point won't be able to get anywhere any faster than if it were launched from earth directly[1]. And sending a probe on a rocket to park itself at an L point wastes delta-v, as opposed to launching the same rocket directly from earth to the target.

[1] Excepting maybe a target that appears conveniently a the same L point.




The point is that you can't leave a rocket on the pad fueled and ready to go 24/7/365 because those pads are in use for other rockets and keeping them ready to fly is fairly labor intensive.

So the advantage of already being in orbit is that you don't have to go through all of the logistics of getting the rocket to the pad, prepping it for flight, getting launch permission, etc... That's a difference of a couple of weeks.


Here's a silly thought: why can't we put the spacecraft on top of an ICBM in a silo and launch when the next extrasolar object is detected? The American and Russian armed forces worked out 24/7 launch readiness in the 1960s.


Because an ICBM doesn't have anywhere near the power needed for such a mission. A timely flyby of an interstellar object would need something akin to the Saturn-V or Falcon Heavy, or perhaps multiple launches of said. An ICBM is a firecracker in comparison.


I see that now. With the two booster stages, the Ulysses spacecraft weighed > 15 tons in LEO, and the Dnieper rocket has a capacity of 4.5 tons to LTO. And you do need to get to Jupiter to turn the orbital plane of the spacecraft out of the ecliptic.


Nobody wants to pay for the personal needed to staff that silo.


ICBMs could only launch a very small probe into orbit and not even a sun centered one. They're meant for basically sub orbital ballistic trajectories for nukes and you don't need the power to put something into orbit for that.


Because launching it could trigger a response?




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