# Could asteroid 2012 XE$_1$$_3$$_3$ become a moon of Venus with the aid of rocket engines?

2012 XE$_1$$_3$$_3$ is an asteroid, classified as near-Earth object of the Aten group that is a temporary co-orbital of Venus.

It is following a transitional path between Venus's Lagrangian points L$_5$ point and L$_3$ point, and is also a Mercury grazer and an Earth crosser.

2012 XE$_1$$_3$$_3$ comes to within 0.05 AU of Earth periodically and will approach Earth at 0.0055 AU on December 30, 2028.

With a diameter of about 62 to 138 meters, could this asteroid be altered in its orbit with today's rocket engines in such a way that eventually it could become a moon of Venus ?

• The asteroid has a diameter of approximately 62 to 138 meters. We don't know its mass yet. For a very simple approximation, lets use a cube of 50 m with a density of 0.5. The volume is 125,000 m^3 and its mass 62,500 metric tonnes. That is several orders of magnitude above a mass we may "move" with rocket engines into an orbit. – Uwe Jul 9 '18 at 9:03
• @Uwe Luckily this asteroid is already into an orbit and many "moves" could eventually achieve the desired goal. – Cornelisinspace Jul 9 '18 at 9:23
• It is not possible using many small moves too, the number of moves will be much too high. – Uwe Jul 9 '18 at 9:39

If it reaches Earth and Mercury, then it already sounds like the delta-V requirements for Venus capture are beyond hope.

If it were to make close approaches to Venus, you might think of using Venus assist to "circularize" its solar orbit at same altitude as Venus around the Sun, putting it in a very elongated orbit, with apoapsis somewhere towards Sun-Venus L4, on non-insane delta-V budget. A minuscule nudge to generate just the right assist against Earth to get it into the trajectory of assist against Venus. Another small nudge during the Venus fly-by to turn the fly-by into a weak capture (its orbital specific energy is already nearly identical to Venus, 1:1 resonance spells that - so the total energy change would be really small), and we're done, Venus gets a moon in a very eccentric orbit. We could even drop the periapsis a little to give it some airbraking for a couple decades to get into more stable, lower orbit, then nudge it back up so that it won't fall down eventually.

The concept would be like this (obviously, all dimensions are exaggerated, eyeballed and generally wrong; it's about the idea, not details.

The red sections of the trajectory depict areas of maneuvers - first, against Earth, a small trajectory adjustment to make the flyby against Venus just right. Then against Venus - as Venus provides assist turning the orbit "outwards" - instead of towards Mercury, to one more along own orbit, the engine fires retrograde to prevent the asteroid from escaping Venus gravity. This would put the asteroid in Venus orbit. L4 is just marked for informative purposes - it doesn't actually play any role in this maneuver.

Unfortunately, Venus is not as conveniently located.

If $2012 XE_{133}$ passes the Venus orbit between L3 and L5, that means Venus is practically on the opposite side of the Sun from it, and so, the only thing that could circularize its orbit there left are rocket engines. And while the value of the specific energy is about right, the direction of the vector of velocity associated with the kinetic energy is way off. The entire circularization into Venus-like orbit would require an enormous, completely prohibitively expensive burn in direction normal to the trajectory. And then the asteroid would still need to catch up with Venus and be inserted into its orbit.

So, sorry, no.

• Thank you for your comment, although visualizing all the events is very hard for me. Would it be another case if it would orbit L4, like the 2013 ND15 asteroid ? en.wikipedia.org/wiki/2013_ND15 – Cornelisinspace Jul 9 '18 at 11:51
• @Conelisinspace: No, in the first scenario it would orbit Venus. Imagine two fly-bys: first by Earth, changing the trajectory very little, second qute near Venus, strongly affecting the trajectory. The second fly-by passes Venus "from behind" (approaching "from the outside", from Earth), and the asteroid overtakes Venus, its path curved by its gravity in such a way that it continues ahead nearly along the same trajectory as Venus, only faster. That would put it into an orbit with periapsis at Venus orbit, apoapsis somewhere above. But then we have both Venus pulling it back, and our engines.. – SF. Jul 9 '18 at 12:02
• ...giving it a braking push. As it crosses the Venus orbit to head out, away towards Earth, Venus gravity pulls it back - and so it swings "behind" Venus again, then leaves in the same direction as before - essentially a classic strongly eccentric orbit with major axis mostly tangent to Venus orbit. If you still have trouble visualizing it, I may try to draw it. – SF. Jul 9 '18 at 12:04
• If the 2013ND15 asteroid could have a chance orbitting Venus, i could, only with your permission, change my question toward that asteroid. – Cornelisinspace Jul 9 '18 at 12:26
• @Conelisinspace: I think that should be an entirely different question, as the involved orbital mechanics would be completely different. Anyway, I'll try to add the diagram. – SF. Jul 9 '18 at 13:00