Rad+

[KvickFlygarn87]

What is RAD+, and how do I know where to burn towards it?

I've used MJ before to burn RAD+, in order to raise periapsis. Now I want to learn to play the game like the great Scott, so where do I find RAD+?

I asked this in my Duna thread, but I only got an answer I know is wrong.

Thankyou!

Edited September 6, 2013 by KvickFlygarn87

[Kimberly]

Radial-in (RAD+) and radial-out (RAD-) are perpendicular to your direction of motion, on the horizontal plane. Imagine you're in a perfectly equatorial orbit around Kerbin; in this case, radial-in and radial-out are towards Kerbin and away from Kerbin, respectively.

Edit: d'oh, seems I get them switched. RAD+ is away and RAD- is towards.

Edited September 6, 2013 by Kimberly

[blizzy78]

RAD+ is the "radial" direction. In a circular orbit around a body, that would be exactly towards the sky - away from the body.

[KvickFlygarn87]

Okay, thanks!

[Mr Shifty]

Note: burning radially to raise your periapsis is inefficient. Any energy that you use to change the direction of your velocity rather than changing the magnitude is wasted energy. Most efficient is to burn prograde at apoapsis.

If your orbit is circular, RAD+ will be the very top point on the blue half of the NavBall. If your orbit is not circular, to find RAD+, first point at your prograde vector, then follow that point's 'longitude' line on the NavBall toward the top-most point until you're 90 degrees from prograde. If you're heading toward apoapsis, this will be past the top-most point on the NavBall. If you're heading toward periapsis, it will be before the top-most point.

[Specialist290]

Another way to do it: If you go to the Map View and plot a maneuver node, the two "blue circle" knobs indicate the direction of the radial vectors at the point in the orbit where you set down the plot.

Likewise, the green / yellow markers are your prograde and retrograde, and the purple markers are your normal and antinormal.