Settling argument of periapsis once and for all

[Human Person]

Setting up Orbits with a defined argument of periapsis by doing a rendezvous with a ghost.

The idea:

the contracts for setting up specific orbits always say: "argument of periapsis: undefined" and i don't like that. Sometimes (especially when setting up a relay-network) you don't just want your satelite to be somwhere on a specific orbit, you want it to be at a specific time in a specific place on that orbit, eg. to fill the gap in a perfect triangle.

To do this, it would be helpful to use "ghost-crafts", which can be rendevoused with but only exist in the imagination of the tracking station. They don't need to be launched, they don't leave any debris, they are just place-holders for where (and when) we want to have our crafts.

What do you think? Good idea? 

Edited February 12, 2017 by Physics Student
Misspelling

[Red Iron Crown]

Argument of periapsis isn't what you appear to think it is. I think you want a specific mean anomaly.

[HebaruSan]

Looks like I'll get a lot of mileage out of this image today. Argument of Periapsis is the angle between your ascending node and your periapsis (not specifically highlighted in the graphic, but that's the idea). When it's zero, they're at the same spot. When it's π, they're opposite each other (meaning your Pe is at your DN and your Ap is at your AN). If a contract says "undefined," I would guess that's because the orbit is circular (i.e., the Pe and Ap don't really exist because the whole orbit has the same radius). Might as well just say 0 instead, since all the math would still work with any value in that case.

[Hotaru]

Whatever it's called, I do think this is a good idea. When contracts ask for a satellite in stationary orbit, they generally want it to orbit over some specific point on the surface--it would be very helpful to have a (preferably targetable) marker on the contract orbit showing the point on the orbit directly above that spot.

[paulprogart]

4 hours ago, Physics Student said:

the contracts for setting up specific orbits always say: "argument of periapsis: undefined" and i don't like that.

Are you playing with some kind of contract system mod?  I just looked back through my contracts and can't find any that say this (100% stock game).  If you're modded and getting contracts that say this you might want to report it in the appropriate mod thread.

As to the idea of ghost ships, I do like it.  Though I'd prefer if instead the map view would just dynamically show how far off you are from the target orbit (and position, when applicable).

Also (since nobody else has said it yet), welcome!

[Human Person]

2 hours ago, Red Iron Crown said:

Argument of periapsis isn't what you appear to think it is. I think you want a specific mean anomaly.

Yes, I meant exactly that. I'm sorry I should have looked it up before posting here.

[Human Person]

I'm sorry I got something wrong here:

Being at a specific time at a specific point in a specific orbit is not given by the argument of periapsis, it's the mean annomaly. I hope i'm not confusing anything else.

[George van Doorn]

6 hours ago, Physics Student said:

Setting up Orbits with a defined argument of periapsis by doing a rendezvous with a ghost.

What do you think? Good idea? 

 

Settling the argument of periapsis or the mean anomaly notwithstanding, I think it's fabulous, it's fantastic, it's a great idea.

So basically you want to arrive at the geostationary orbit and be above a certain point on the planet. Then, once you circularize, you will hold stationary position above that point. You know, there's a new type of sat position contract since 1.2 that asks you to do that. The way I do it is transfer from LKO to the geostationary orbit and ballpark it so that I arrive there kinda above that spot. It's not perfect of course. Then I put the satellite in a slightly lower / slightly higher orbit.  Eventually I catch up to that point and then I circularize. Takes a while, your idea would make this geostationary hold easier. So, in absence of that and if you don't wanna do some math on paper, this is the way to practically achieve that in KSP.

[Human Person]

2 hours ago, Hotaru said:

Whatever it's called, I do think this is a good idea. When contracts ask for a satellite in stationary orbit, they generally want it to orbit over some specific point on the surface--it would be very helpful to have a (preferably targetable) marker on the contract orbit showing the point on the orbit directly above that spot.

I'd go even further. I want to be able to set up these ghost-crafts myself to do fun things (apart from contracts) with them. So far, I used small crafts wich i edited in the desired orbit and then did a real rendezvous with them. It doesn't feel right.

[Hotaru]

29 minutes ago, Physics Student said:

I want to be able to set up these ghost-crafts myself

I agree; two situations I can think of where this would be extremely useful are setting up satellite networks and planning interplanetary transfers before liftoff.

[Martian Emigrant]

Hum....

I admit that it always annoyed me that the new satellite is just dumped in the orbit and Bob's your uncle.

Easy cash and you go on but....

How about having contracts to place a satellite above the KSC, Nye Island, ETC.

Either with a "Ghost" to rendez-vous with or maybe giving us a window of say 5 degrees of longitudes.

Of course satellites would drift so....

 

More contracts. "Reposition Geo-sat-one over Nye Island" (It's longitude anyway).

 

ME

[Tyko]

Sounds like some sort of navigation target. I can go into the tracking center and specify an orbit and a placement on that orbit. Once set, it shows up like a craft in that position. Then you can use rendezvous techniques to get your satellite placed properly.

It's a fun idea. Would also be useful for getting craft into perfectly 0 degree inclination orbits.

[Martian Emigrant]

21 hours ago, Tyko said:

It's a fun idea. Would also be useful for getting craft into perfectly 0 degree inclination orbits.

Hi Tyko.

Can't always be done (It depends on the planet). But.

Over Kerbin before I do a re-entry with a space plane with the intent of landing at the KSC.

I click the Mun as target. It is exactly over the equator.

So match planes with it and you are set to 0°.

 

ME

EDIT

Conversely you can use the planets own orbit to set a pretty good plane.

It you zoom out enough (On the map) you can see the oultine of the orbit.

Move the camera until you get a good intersection of your orbit and the orbit of the planet (or moon).

Put a manoeuvre node there. With a combination of zoom-in-out and tweaks you can get them matched.

Edited February 15, 2017 by Martian Emigrant

[Tyko]

1 hour ago, Martian Emigrant said:

Hi Tyko.

Can't always be done (It depends on the planet). But.

Over Kerbin before I do a re-entry with a space plane with the intent of landing at the KSC.

I click the Mun as target. It is exactly over the equator.

So match planes with it and you are set to 0°.

 

ME

EDIT

Conversely you can use the planets own orbit to set a pretty good plane.

It you zoom out enough (On the map) you can see the oultine of the orbit.

Move the camera until you get a good intersection of your orbit and the orbit of the planet (or moon).

Put a manoeuvre node there. With a combination of zoom-in-out and tweaks you can get them matched.

Yep, thanks for sending. I use similar tricks myself. Just calling out that being able to put a "target location" into the map view and then rendezvous with it would be a neat solution.