# Search results

1. ### How calculate semi-latus rectum of parabola or hyperbola?

I looked into the Orbiter manual once again. We have semi-major axis = - G * major body mass / (2 * orbit specific energy), eccentricity = sqrt (1 + 2 * orbit specific energy * h^2 / (G^2 * major body mass^2)) Hence semi-latus rectum = semi-major axis * (1 - eccentricity^2) = - G * major body...
2. ### How calculate semi-latus rectum of parabola or hyperbola?

@jarmonik, this is correct if eccentricity = 1. This is what I meant, sorry.
3. ### How calculate semi-latus rectum of parabola or hyperbola?

Oh, now I saw the formula But to compute the right hand side, I only know the formula which also seems to be undefined in the case of a parabola. So I still have no idea what to do in the case of a parabola.
4. ### How calculate semi-latus rectum of parabola or hyperbola?

Thanks for your replies! So if I have a hyperbola, I can also use the formula and the semi-major axis is then negative, whereas it is positive in the case of an ellipse, right? And that yields the same formula for the semi-latus rectum, i.e. no matter if we have an ellipse or a hyperbola. But...
5. ### How calculate semi-latus rectum of parabola or hyperbola?

The semi-latus rectum is necessary for the formula However, if we refer to Wikipedia, we need to know the semi-major axis to calculate the semi-latus rectum. But the semi-major axis is only defined for circles and ellipses, if I am not getting it wrong. So assume I am in a parabolic or...
6. ### How calculate the minimum Delta v necessary to change one given orbit into another given orbit?

Ok, so no simple solution? :( Only the energy-mass-ratio of an orbit is certainly not enough since we can have very different orbits with the same energy. But yes, maybe combining it with angular momentum will yield something meaningful, so thank you for that idea! Actually I want to land on...
7. ### How calculate the minimum Delta v necessary to change one given orbit into another given orbit?

And how would you do it?
8. ### How calculate the minimum Delta v necessary to change one given orbit into another given orbit?

If the planes of the two orbits are different and if the orbits intersect only at the nearer node, then it might be cheaper to do the plane alignment at the further node and then to match the orbits at the next intersection. So even if we are in the one-spherical-body model and if there is an...
9. ### How calculate the minimum Delta v necessary to change one given orbit into another given orbit?

The question is to be understood in the idealized model where I have only one point mass and a vessel with neglectable mass in orbit, Newton mechanics. Thanks for your help!
10. ### API Question Get name/mass of a CELBODY (and what if it is NULL?)

Do you mean that the bodies without ephemeris data are calculated by Orbiter only for those times, which are necessary, as if they were vessels?
11. ### API Question Get name/mass of a CELBODY (and what if it is NULL?)

But oapiGetGlobalPos/oapiGetGlobalVel do not accept time as argument.
12. ### API Question Get name/mass of a CELBODY (and what if it is NULL?)

Hi, thank you so far. @n72.75, I would like to obtain the locations and velocities for all bodies, for different times. The names are only necessary to map them correctly. Now I have seen that pGBody is NULL only for Vesta, the Neptune moons and one of the Uranus moons.
13. ### API Question Get name/mass of a CELBODY (and what if it is NULL?)

I want to get ephemeris data of all bodies. So I do the following: unsigned int nGBodies = oapiGetGbodyCount(); for (unsigned int iGBody = 0; iGBody < nGBodies; iGBody++) { OBJHANDLE hGBody = oapiGetGbodyByIndex (iGBody); CELBODY *pGBody = oapiGetCelbodyInterface (hGBody); ... }...
14. ### Flight Question What is changing Phobos' orbit?

Is it maybe the fact that Mars it not a perfect ball?
15. ### Flight Question What is changing Phobos' orbit?

But none of these fluctuations is created by Deimos, is it? So what is then the reason and how can we calculate the same Orbit externally?
16. ### Flight Question What is changing Phobos' orbit?

Oh, thanks, what are the x- and y-axis in the diagram?
17. ### Flight Question What is changing Phobos' orbit?

1.14 seconds per second because, for instance, Orbit MFD shows ApT=64.52 and one second later ApT=63.38 (the difference is 1.14).
18. ### Flight Question What is changing Phobos' orbit?

Hey, do you know why the orbit of Phobos seems to change so fast? When it approaches its apoapsis (on 2021-12-01), in Orbit MFD, the "ApT" value of Phobos decreases at 1.14 seconds per second, meaning that the apoapsis location is moving about 0.14 seconds (295 meters) backwards every second. If...
19. ### TransX How to restart TransX when buggy?

Sometimes, my TransX has a bug, so I want to restart it. Simply cancelling all plans, going back to stage 0 or restarting Orbiter does not seem to work. A frequent bug is (I don't know how to trigger it) that changing the velocities in manoeuvre mode stops influencing the orbit in the next stage...
20. ### TransX Creating escape plan from Earth to Moon while on ground

The opportunity to create an escape plan in TransX while standing on the ground, instead of going to orbit first and then creating the plan, may be important in order to minimize the time in earth orbit. This is no problem when going from Earth to any other planet: I set the "select target"...