# Recent content by silkms

1. ### Possible to solve for the initial speed of a projectile?

Janus, works great. Thanks again!
2. ### Ellipse from 2 arbitrary points, tangent at P1 and focus

Just it's direction. Actually hoping to find it's velocity.
3. ### Ellipse from 2 arbitrary points, tangent at P1 and focus

Yup. I am using them to find the velocity for a projectile at p1, when both p1 and p2 are on the surface of the planet, but unfortunately my technique for finding the true anomaly (the angle between p1 and the periapsis), breaks when one of the points leaves the surface and is no longer...
4. ### Ellipse from 2 arbitrary points, tangent at P1 and focus

MENTOR Note: Moved this thread from a math forum hence no template Is it possible to find this? Really only need the semi major axis or even it's orientation. In the image below, elements in red are known.
5. ### Possible to solve for the initial speed of a projectile?

New wrinkle. If the position on the ellipse of the second point becomes arbitrary (i.e. not necessarily on the surface of the planet). How could you go about solving this? I have attempted to find q (the angle to the periapsis) with the new scenario but not having much luck there. Any ideas...
6. ### Possible to solve for the initial speed of a projectile?

Janus, thank you for the second breakdown. Went back and found the error in my initial setup and it is now working. Very much appreciated!
7. ### Possible to solve for the initial speed of a projectile?

Janus, Thank you for your very clear response. It has been very helpful! I've followed your reasoning and tried applying it, but am not getting the correct result. After looking at it a bit more, I don't believe that we can use the radius of the planet (Rp) as the distance from the center of...
8. ### Possible to solve for the initial speed of a projectile?

Nidum, A.T. Thanks! Looking into both.
9. ### Possible to solve for the initial speed of a projectile?

Is it possible to solve for the initial speed of projectile hitting a target given that we know the direction (vector) that it is released at and the point on a the surface that it is hitting? If so how would you go about finding an equation to solve for this? I realize that this is a...