Thrusting forward in EVA

[sevenperforce]

So Jeb's on the surface of Minmus, and his capsule is in an eccentric orbit, about to pass directly over his head. The capsule has no probe core, so it's up to Jeb to make the rendezvous on his own. He should definitely have enough RCS monopropellant to get back to it, since he deorbited and landed using less than half of his RCS propellant.

I can get Jeb into orbit easily enough, but I'm having a lot of trouble with the controls. I can't seem to get him to thrust prograde in the same direction as the navball marker. I can set the capsule as target and (apparently) line it up, but I always end up thrusting slightly off-angle, and by the time I make the corrections I'm out of propellant.

What am I missing? Is this doable?

(edited)

Edited August 23, 2017 by sevenperforce

[bewing]

As you orbit, the direction of prograde constantly changes -- and kerbonauts on EVA have no SAS control. But it should be efficient enough if you use small puffs, or if you constantly reset as close to prograde as you can by hitting space. However, I'm going to bet that you can save more than enough propellant by just having jeb climb a mountain before he goes zooming back to orbit. Of course, he should get to orbit by thrusting pure prograde, right?

 

[sevenperforce]

10 minutes ago, bewing said:

As you orbit, the direction of prograde constantly changes -- and kerbonauts on EVA have no SAS control. But it should be efficient enough if you use small puffs, or if you constantly reset as close to prograde as you can by hitting space. However, I'm going to bet that you can save more than enough propellant by just having jeb climb a mountain before he goes zooming back to orbit. Of course, he should get to orbit by thrusting pure prograde, right?

Wow, I completely messed up what I meant to say.

I said prograde, but I meant pro-heading. Like, if I want to match orbital velocity with my target, I'll line up the navball heading indicator with the target-retrograde marker. But what do I do then? If I press W, the target-relative speed starts to drop, but then the marker starts wandering. I think I'm thrusting off-axis...maybe because I can't control pitch?

[bewing]

If you are trying to get to orbit, thrusting target-retrograde is a very fuel-inefficient way to do it. Which is why you are running out. You need to get to low orbit efficiently by thrusting prograde, before you start using target-based maneuvers to actually dock.

[sevenperforce]

23 minutes ago, bewing said:

If you are trying to get to orbit, thrusting target-retrograde is a very fuel-inefficient way to do it. Which is why you are running out. You need to get to low orbit efficiently by thrusting prograde, before you start using target-based maneuvers to actually dock.

How can I thrust prograde from EVA, when my thrust vectors are all plane-dependent?

[WanderingKid]

There's a couple of indicators you can use as you take off.  First, if you've got the default skybox, there's a band of stars about level with the orbital plane.  Use that as a guide for equatorial aim for prograde/retrograde.  Also, you want to turn the camera so Minmus is just barely on screen, use spacebar to orient that way, then thrust forward.  It's not exact but it gets you close to pro/retro.

For the above, thrusting prograde basically means get a bit off the ground and then run horizontal with most of your propellant to achieve orbit with just your EVA pack.  From there, you figure out your rendezvous.  Don't try to rendezvous directly from ground, you'll want to do it from orbit, like any other rendezvous, just with a lot less clutter like SAS, thrust controls, etc... XD

It's totally doable, but a direct intercept with your ship in orbit means that you go straight up to try to catch it, then suddenly you have to get ~180 m/s sideways speed.  It's much, much easier to achieve orbit and then rendezvous.

[sevenperforce]

5 minutes ago, WanderingKid said:

There's a couple of indicators you can use as you take off.  First, if you've got the default skybox, there's a band of stars about level with the orbital plane.  Use that as a guide for equatorial aim for prograde/retrograde.  Also, you want to turn the camera so Minmus is just barely on screen, use spacebar to orient that way, then thrust forward.  It's not exact but it gets you close to pro/retro.

For the above, thrusting prograde basically means get a bit off the ground and then run horizontal with most of your propellant to achieve orbit with just your EVA pack.  From there, you figure out your rendezvous.  Don't try to rendezvous directly from ground, you'll want to do it from orbit, like any other rendezvous, just with a lot less clutter like SAS, thrust controls, etc... XD

It's totally doable, but a direct intercept with your ship in orbit means that you go straight up to try to catch it, then suddenly you have to get ~180 m/s sideways speed.  It's much, much easier to achieve orbit and then rendezvous.

After I finally figured out exactly what North/South orientation my Kerbal was holding, I was able to make it work:

 

[BjM]

On 23/08/2017 at 2:12 PM, sevenperforce said:

I said prograde, but I meant pro-heading. Like, if I want to match orbital velocity with my target, I'll line up the navball heading indicator with the target-retrograde marker. But what do I do then? If I press W, the target-relative speed starts to drop, but then the marker starts wandering. I think I'm thrusting off-axis...maybe because I can't control pitch?

Sorry if I misunderstand it, but shift and ctrl go up/down on eva.

[sevenperforce]

2 hours ago, BjM said:

Sorry if I misunderstand it, but shift and ctrl go up/down on eva.

Doesn't help with your heading.

When you're in a suborbital trajectory, you can only thrust straight up, straight down, or parallel to the surface. This means that it doesn't matter what direction you try to point your Kerbal; his or her RCS thrusters cannot angle at all and thus cannot perform any sort of gravity turn. Either you're thrusting directly parallel to the surface, or you're thrusting straight up or down. If you try to thrust at an angle by pressing W and Shift and the same time, you end up with huge cosine losses...maybe not problematic in most cases, but bad if you're trying to reach orbit from the surface.

Once you're orbital, your orientation system changes, and now your up/down axis is aligned with the ecliptic. If you happen to be in a perfect equatorial orbit chasing a target in a perfect equatorial orbit, great...but if you have inclination to deal with, then it becomes categorically impossible to thrust "prograde" or "retrograde" to change your orbit. 

[Palaceviking]

Use view/camera 'free'

[Draalo]

3 hours ago, Palaceviking said:

Use view/camera 'free'

This.

To be more precise: Set your camera to mode "free" with the key "V".

Orientate your view, press spacebar (yes, sounds crazy for a KSP player, doesnt it?), the kerbal will now look right into the camera angle.

Repeat till the marker is in the center of the NavBall.

Then just accellerate, if needed correct the angle a bit.

Edited October 5, 2017 by Draalo