A ballistic launch will produce an elliptical orbit, sure. Any satellite with mass will have an elliptical orbit, ultimately, due to torque. But, with current tech level, it seems like we can orbit satellites initially in near circular trajectory, and let other forces work from there. Generally, though, elliptical trajectories are planned on and executed.

Is it not energetically feasible to start in circular orbit?

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    $\begingroup$ If the mission of the satellite requires a circular orbit, it is inserted to one. But an elliptical orbit is not a less perfect orbit, some missions required it. $\endgroup$
    – Uwe
    Feb 23, 2018 at 10:12
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    $\begingroup$ Re Any satellite with mass will have an elliptical orbit, ultimately, due to torque. I suspect there's a fundamental misunderstanding on the part of the OP regarding orbits. $\endgroup$ Feb 23, 2018 at 13:21
  • $\begingroup$ @DavidHammen How so? A perfectly circular orbit is not possible. A planet makes the star wobble. The torque causes the orbit to destabilize over time. $\endgroup$ Feb 23, 2018 at 15:58
  • $\begingroup$ @MarsJarsGuitars-n-Chars I think what would be better to say is that even if a nominally circular orbit would be desired, no orbit is going to be perfect. In reality because the Earth is both oblate and "lumpy" both inside and out, real orbits will not even be true ellipses, and for LEO these effects are usually much larger than perturbations from the Moon, Sun, and other planets. $\endgroup$
    – uhoh
    Feb 25, 2018 at 5:42

1 Answer 1


Why wouldn't we?

More seriously, at the end of the initial boost a rocket is typically not high enough above the Earth's surface to enter a stable circular orbit, let alone an orbit suitable for say a telecoms satellite (which is much higher). So the initial boost puts it into an elliptical orbit with it's upper end (apogee) at the altitude of the desired final orbit. Then when it reaches that altitude, a further thrust (whether by turning the original rocket back on, or by using another one) increases its velocity until the orbit is circular.

For some applications, an elliptical orbit is actually better. For instance the Juno probe is in an elliptical orbit around Jupiter so that it can spend as little time as possible in Jupiter's radiation belts, while getting close up observations and having time to send data back to Earth. It also makes it easier to adjust the orbit to pass over different parts of Jupiter on different orbits.


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