Help! How do I make a slow orbit?

[fenderzilla]

I've tried and failed many times to get my ships to dock in kerbin orbit. I know why - my space station is moving at over 2000 m/s orbital speed! in Scott Manly's vids, his orbital speed is like 50. I can't burn retrograde because it lowers my periapsis, and that makes me aerobrake and crash back into kerbin. how do I launch a station with a slower orbit?

[RogueMason]

Simple; move your station into a much higher orbit. Craft in higher orbits will move slower than in a low orbit due to the weaker gravity at the greater altitude. Try sticking some satellites in orbits of different altitude to see what I mean.

Edited July 31, 2013 by RogueMason

[Awaras]

It is impossible to be 'in a slower orbit'. If you are moving at 50 m/s you WILL fall back down to Kerbin.

What you probably saw in the Scott Manley video is the RELATIVE speed between the craft he was flying and the space station. To see the relative velocity you must first select your target in the map view and then click on the speed indicator on the navball until it reads 'target' instead of 'orbit'.

[Spartwo]

scott's moving at 50 relative to the station.left click on the velocity when you get close and it should change to relative velocity,you have to get that down to 0 at the closest point.A slow orbit would make no difference.

EDIT:orbit gilly

Edited August 1, 2013 by Spartwo

[Scotius]

What Awaras said. It does not matter how fast the station or your own ship is moving relative to Kerbin's surface. What matters is relative velocity between two ships.

[Dizzle]

The speed you saw in the vid, as others have said, is the speed relative to the target. When you have set a target, click the speed indicator and it will change between orbital, surface, and (relative to) target.

[air805ronin]

Its like when you're driving down the highway. The truck next to you is going 75. You're going 70. Relative speed is 5 m/s from one perspective.

[Whirligig Girl]

If you played Space Agency before KSP, it would be easy to make this mistake. two different circular orbits at the same altitude must be more or less the exact same speed., if you slow, you WILL FALL.

[MockKnizzle]

If you click on the velocity indicator, it will switch between Surface, Orbital, and Target modes. Target mode only works if you have a target selected.

They're all pretty self-explanatory:

-Surface mode tells you your velocity across Kerbin's (or another body's) surface, taking the rotation of the planet into account. In other words, the reference frame is rotating with the planet.

-Orbital mode tells you your orbital velocity around Kerbin, ignoring the planet's rotation. The reference frame is stationary.

-Target mode tells you your velocity relative to whatever target you have selected, be it another spacecraft or celestial body. Most rendezvous and docking procedures use target mode, and that's what you see in Scott's videos.

...And a little extra math because I feel like it.

We can figure out exactly what the difference between Surface and Orbital velocities on Kerbin would be Kerbin is 600km in radius, and rotates once every 6 hours, so the surface is rotating at:

[2 x 600km x (1000m / 1km) x 3.14159] / [6hr x (60min / 1hr) x (60s / 1min)] = 174.53m/s

...which is more or less exactly what you get when you switch the velocity indicator to Orbital mode when sitting on the launchpad

Essentially, your surface velocity is always going to be your orbital velocity minus the rotational speed of the planet, in this case 174.53 m/s.

Edited July 31, 2013 by MockKnizzle

[Tiron]

-Orbital mode tells you your orbital velocity around Kerbin, ignoring the planet's rotation. The reference frame is stationary.

Only relative to the planet itself. You're still going around the sun.

Luckily unlike the real world the Sun isn't moving within the galaxy, and the galaxy isn't moving within the universe, so that's all there is to it.

[MockKnizzle]

Well yes, you're correct, but since we're operating within Kerbin's SOI that's an unnecessary complication that I didn't feel the need to include. Judging from the OP, we're probably best starting simple and working our way up from there.

[fenderzilla]

mmm. I had no idea how dumb I was being. sorry.

[eurybaric]

Moreover, if you want to have a lower orbit speed, you have to go to a higher orbit, meaning you have to widen your orbit by doing prograde burns. A bit counter intuitive it may seem at first, but once you get the hang of it, it starts making sense.

For example, that's how geostationary (or keostationary in this context ) orbits are acheived: you orbit high enough, on kerbin its around 2868.7km, so that your speed matches the rotation of the planet ( roughly 174m/s as stated earlier ). In that way you are always above one certain point on the surface of kerbin, and the planet doesn't rotate underneath you at all.

Also, don't feel stupid for not knowing something hehe, it's part of the learning process

Cheers!

[Anton P. Nym]

mmm. I had no idea how dumb I was being. sorry.

No, don't feel that way... KSP doesn't come with an instruction manual, so unless you're a total rocket geek you're not going to know this stuff coming into the game. That's fine; that's what forums like this, and tutorials like on the YouTube channel, are for.

-- Steve

[austin4050]

Post moved to Gameplay Questions and Tutorials.

[FlamedSteak]

Just remember to set your target, it get's unimaginably easier to rendezvous and dock when you get your head around how to use the maneuver node and gimball markers .

[saik0]

Its like when you're driving down the highway. The truck next to you is going 75. You're going 70. Relative speed is 5 m/s from one perspective.

If there's a truck next to me going 70 m/s, rest assured I'll not be attempting a rendezvous. Jeb on the other hand...he'd be driving the truck.

[fenderzilla]

No, don't feel that way... KSP doesn't come with an instruction manual, so unless you're a total rocket geek you're not going to know this stuff coming into the game. That's fine; that's what forums like this, and tutorials like on the YouTube channel, are for.

-- Steve

I do consider myself a total rocket geek... now that i've played ksp so much.