# How feasible would it be to get to a planet orbiting directly opposite Earth?

Imagine that in addition to Earth, there was a second planet, say of one Earth mass, orbiting the sun - but on the opposite side of the Sun, and at the same orbital radius.

My question is - given today's technology, would it be feasible to try to launch something to reach that planet? A rover, a capsule, or something of the sort is what I have in mind.

There are a couple reasons I initially don't see a solution. First off, the escape velocity of the Earth is about 11.2 km/s. The Earth's orbital velocity around the sun is nearly 30 km/s. This means that if I were to launch a rocket in the opposite direction of Earth's orbit to reach this "second Earth", not only would I have to counter this 30 km/s orbital velocity, but I would have to provide enough thrust for double this velocity in order to maintain a stable orbit around the Sun at the radius that Earth orbits at - but in the opposite direction. I'm not quite sure if rockets can get up to velocities that high - I know that the Juno probe is moving at around 73 km/s, but I believe that was after a series of maneuvers involving a gravitational slingshot.

Perhaps there is another solution? One that popped into my head was to launch it at an angle to the plane of Earth's orbit, but I don't quite know how that would work out, given that unless some serious trajectory corrections were made, the rocket would not arrive anywhere close to the planet - as the planet would have moved in the time the journey took.

Maybe it involves taking a path that is closer to the Sun, and more elliptical? At this point I'm just throwing out everything that comes into my head.

Basically, I'm looking for some sort of general explanation here, with a rough idea that I could build on. And if it isn't possible with today's technology, what do we lack?

• "Imagine that in addition to Earth, there was a second planet, say of one Earth mass, orbiting the sun - but on the opposite side of the Sun, and at the same orbital radius." We can do better than just imagining it :-) Why would Hollywood's Planet X (at earth's L3) be unstable?
– uhoh
Commented Mar 7, 2020 at 10:53
• This question is perhaps better suited to Worldbuilding SE, where, in fact, there are already several question dealing with this : see this question and the linked questions on that page. Commented Mar 7, 2020 at 12:16
• There's some good info on Space Exploration: How much delta v does it take to get to the Sun-Earth Lagrange 3 point? Commented Mar 7, 2020 at 14:31
• Ignoring the fact that said planet cannot exist (the L3 point is unstable), there exists an infinite number of two burn solutions to reach the L3 point that have the spacecraft making $m$ orbits in $n+\frac12$ years, where $m$ is a positive integer and $n$ is a non-negative integer. How long are you willing to wait to reach a planet that cannot exist? The longer the wait, the cheaper it gets, at least in terms of delta-V. Commented Mar 8, 2020 at 5:56
• Similar question here. space.stackexchange.com/questions/32286/… Reaching a theoretical planet at L3 isn't that hard, just drift to a higher orbit or a lower orbit, and wait. After that, aero-break. Commented Mar 8, 2020 at 16:43