3
$\begingroup$

Pretty new to orbital mechanics and this question has been bugging me. How would the shape of the orbit be affected by a prograde burn at a location that isn't the periapsis or apoapsis ? For example at the arbitarary A below

Eliptical Orbit

In particular that would be the effect on the orientation of the major axis and the distances of the periapsis and apoasis.

Thanks !

$\endgroup$
  • 5
    $\begingroup$ You should play Kerbal Space Program to get a feeling for this, but I won't take any responsibility for a significant increase of your procrastination level. $\endgroup$ – koalo Feb 14 '18 at 22:23
  • 1
    $\begingroup$ There is a simpler program for mobile called Simple Rockets that can demonstrate this, too. Loads of fun. $\endgroup$ – Chris B. Behrens Feb 14 '18 at 22:31
  • $\begingroup$ Are you looking for more detail other than that the section of the orbit generally opposite the burn is raised, while the point at which the burn occurs remains unchanged? $\endgroup$ – Russell Borogove Feb 15 '18 at 0:17
  • 1
    $\begingroup$ Apoapsis also shifts in the direction of the point-opposite-burn, while periapsis shifts towards the burn point. $\endgroup$ – Russell Borogove Feb 15 '18 at 1:10
  • $\begingroup$ @RussellBorogove Thanks for the input , I suspected the shift would be what you described. And not to get super needy but some math to back it up would be swell if anybody could point me in the right direction. $\endgroup$ – thebmags Feb 15 '18 at 7:25
6
$\begingroup$

As a general rule of thumb, any prograde or retrograde burn establishes a new orbit tangent to the old orbit at the point of the burn. A prograde burn increases the length of the major axis, while a retrograde burn reduces it. To demonstrate, I set up a situation similar to yours in Kerbal Space Program, and had it draw the results of two proposed maneuvers. In both, the solid blue-green line is the initial orbit, the dotted brown line is the the result of the maneuver, and the star shape is the point of the burn.

enter image description here

A prograde burn at your proposed "point A" extends the major axis, raising both the periapsis and apoapsis, and rotating the major axis in the prograde direction.

enter image description here

A prograde burn on the other side of the orbit's major axis also raises the periapsis and apoapsis, but rotates the major axis in the other direction.

$\endgroup$

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.