How useful are geostationary space stations?

[CaptRobau]

What would the advantages be of a space station in a geosynchronous orbit around Kerbal? Would they make good refueling spots for missions to the Mun and beyond?

[Nibb31]

Not really useful. They are require too much fuel to get to.

The only real use of GSO is for communication, which is not implemented in KSP yet.

[El Coronel]

Yeah, only use I can think of as of now is RemoteTech mod.

[skykooler]

Yeah, only use I can think of as of now is RemoteTech mod.

Very useful for Remote Tech; but there is one more advantage, which is that if you launch a rocket your space station is always in the same place. This allows you to put it wherever is necessary so that you can launch directly from KSP into an intercept without having to wait several orbits for a rendezvous.

[acealeam]

Very useful for Remote Tech; but there is one more advantage, which is that if you launch a rocket your space station is always in the same place. This allows you to put it wherever is necessary so that you can launch directly from KSP into an intercept without having to wait several orbits for a rendezvous.

Geosynchronous orbit over KSC isn't the easiest thing. Correct me if I'm wrong but the only way to get there without waiting is to go straight up and not do a gravity turn.

[El Coronel]

Depends what you mean by waiting, but surely you only need to burn directly opposite KSC to bring ap/pe to 2678 (or whatever), then when you pass over KSC burn to circularise?

[Audiopulse]

Geosynchronous orbits at Kerbin? I thougt a deployed station or satellite would fall into moons SoI eventually?

[KerbMav]

Which you cant, because you will always start on a parable, the rotation of the planet adds to your flight vector at launch.

And even if you could go straight up, you would either shoot past/through your station real fast - or if you slowed down you would instantly start to drop back to the planet as you are not on an orbit but simply "throwing" your rocket in the sky.

Would be an interesting stunt (mechjob?? ^^) though: rising up, slowing to zero speed and docking just on your apoapsis/turning point.

Although I think this is still not correct.

But flying at a certain - accelaration dependent - angle you really would have a somewhat easier intercept i think.

[sanity]

the only way to geo synch above KSC is to go into orbit normally and adjust your timing so that you arrive at geosynch at the same time as you arrive above the KSC. if you go straight up KSC will rotate beneath you before you even get close to geosych orbit ranges.

geosynch is useful because you can position your station at a phase anle for a specific rocket so it can make a normal ascent straight into a rendezvous with the station every time

[Mr Shifty]

the only way to geo synch above KSC is to go into orbit normally and adjust your timing so that you arrive at geosynch at the same time as you arrive above the KSC. if you go straight up KSC will rotate beneath you before you even get close to geosych orbit ranges.

geosynch is useful because you can position your station at a phase anle for a specific rocket so it can make a normal ascent straight into a rendezvous with the station every time

Untrue. For RemoteTech, you have to launch your first satellite directly into geosync from KSC without orbiting. You can't burn on the far side of Kerbin because you will lose communication there. It's not critical that you be directly above KSC, just line-of-sight for communication. But, if you want, you can do a slight westward gravity turn for a nearly straight-up launch. It's not very efficient, but easy to pull off with a heavy launcher. I was able to stack three comm satellites on top of a NERVA-powered transfer vehicle and launch the whole assembly into geo-sync with a heavy lifter. Then I used the transfer vehicle to drop the satellites off in an equilateral triangle geo-sync configuration over Kerbin for full coverage and still had plenty of fuel to descend to 100km and dock at my space station there.

[Rickenbacker]

Which you cant, because you will always start on a parable, the rotation of the planet adds to your flight vector at launch.

And even if you could go straight up, you would either shoot past/through your station real fast - or if you slowed down you would instantly start to drop back to the planet as you are not on an orbit but simply "throwing" your rocket in the sky.

Would be an interesting stunt (mechjob?? ^^) though: rising up, slowing to zero speed and docking just on your apoapsis/turning point.

Although I think this is still not correct.

But flying at a certain - accelaration dependent - angle you really would have a somewhat easier intercept i think.

Not sure what the orbital speed of a geosynchronous orbit is here, but I have indeed done something like this on Minmus. Launched a ship straight up, just as the target was passing overhead. Since the orbital speed was so low (100m/s or so), I could simply match velocities with the target and dock instantly. Horribly inefficient, though, and probably not useful from Kerbin anyway.

[El Coronel]

Untrue. For RemoteTech, you have to launch your first satellite directly into geosync from KSC without orbiting. You can't burn on the far side of Kerbin because you will lose communication there.

Or you could make life easier on yourself and have the first flight manned and drop off a satellite. Then you can burn on the otherside of Kerbin.

[Mr Shifty]

Or you could make life easier on yourself and have the first flight manned and drop off a satellite. Then you can burn on the otherside of Kerbin.

This is true:)

[Wayfare]

It's a matter of getting your head around things. When docking was introduced to KSP I raised the question of how it would handle wildly differing inertial momentum. My reasoning? Brace yourself...

Say I have a target craft in orbit. And I launch a rendezvous craft a good way ahead of it. I time stuff perfectly so just when my rendezvous craft hits Apoapsis, it encounters the target. Because my rendezvous craft is at nearly 0 orbital velocity at the top of its apoapsis, it should be able to dock in that split second where it encounters the target. And then what?

Well as I was soon explained, a lot of stuff would explode into a rapidly expanding cloud of expensive debris. Because the target would have a very significant orbital velocity, and this velocity would be relative to my rendezvous craft as well, given that it would still be at the planet's surface velocity when you look at it sideways. Three-dimensional thinking and all that. It would be a good old-fashioned collision and disaster.

When you think about it, this is similar to the problem posed by a target in stationary orbit right above KSC. My rocket goes up straight and encounters the target - but when it does, the rocket has a really high "upward" velocity (ie. straight up, needed for a straight vertical trajectory) while the target would be at a really high "sideways" velocity (needed to keep pace with the planet's surface). The result would be another rapidly expanding cloud of expensive debris.

Stuff in orbit is never stationary. It always has velocity relative to something and in some direction. A geostationary orbit is actually really fast - it's so fast it keeps pace with the surface of the planet even at a much higher altitude. To picture this, imagine how fast a race car would have to drive at 500 meters' distance to stay in your field of view while you're gently spinning your desk chair. It would seem "stationary" to your field of view, but it would most definitely not be standing still. And if you threw a brick ahead of it from your desk chair, you'd end up with a rapidly expanding cloud of expensive debris (and probably a dead driver, with all the resulting nasty manslaughter charges - don't try this at home).

OK. So where is it useful? It's not for straight vertical launches. But when you launch the exact same rocket into the exact same geosynchronous orbit every time, it will circularize at the exact same spot relative to the surface every time. If you put a space station into a geosynchronous orbit over that exact spot, you'll have a perfect encounter every time. It essentially gives you a launch window forever. This allows you to achieve encounters very easily. Unfortunately a geosynchronous orbit is really high and fast and you'll be able to build much smaller rockets if you just plan an orbital rendezvous instead.

In short, yeah it can work if you don't mind building ridiculously overpowered rockets

[Mr Shifty]

Unfortunately a geosynchronous orbit is really high and fast

Your description is awesome and nearly perfect. Just wanted to point out that a geo-sync orbit is actually slower than a lower orbit. At lower orbits, your vessels are actually travelling faster around Kerbin than fixed points on the ground below. Example: at a 100km circular orbit, your orbital velocity is 2246 m/s. At geosynchronous altitude (2869km), your orbital velocity is 1009 m/s.

[WhiteWeasel]

Geosynchronous orbits at Kerbin? I thougt a deployed station or satellite would fall into moons SoI eventually?

That's duna and ike.

[Wayfare]

Your description is awesome and nearly perfect. Just wanted to point out that a geo-sync orbit is actually slower than a lower orbit. At lower orbits, your vessels are actually travelling faster around Kerbin than fixed points on the ground below. Example: at a 100km circular orbit, your orbital velocity is 2246 m/s. At geosynchronous altitude (2869km), your orbital velocity is 1009 m/s.

You're absolutely right, the orbital velocity is lower - but I didn't want to complicate matters even more From a launchpad perspective, you need to put more velocity (delta-v, really) into a spacecraft to achieve geosynchronous orbit rather than, say, a regular 100km orbit. The weird thing is you need to put even more delta-v into a spacecraft to achieve an orbital velocity that is slower than geosynchronous. Orbital mechanics are weird!

[Jm419]

You're absolutely right, the orbital velocity is lower - but I didn't want to complicate matters even more From a launchpad perspective, you need to put more velocity (delta-v, really) into a spacecraft to achieve geosynchronous orbit rather than, say, a regular 100km orbit. The weird thing is you need to put even more delta-v into a spacecraft to achieve an orbital velocity that is slower than geosynchronous. Orbital mechanics are weird!

Well, it makes sense if you view it from a perspective of kinetic and potential energy.

For example. Let's say that at a certain altitude, a spacecraft has 10,000 m/s of combined energy. (Yes, I'm aware energy is in units of Joules - let's just simplify matters and call it m/s; a Joule is really a [kg(m²)]/s². It's just how how much velocity had to be put into each kilogram to get it to where it is now.) This 10,000 m/s is combined energy, both kinetic and potential. Kinetic energy can be looked at as energy an object has while it's moving; it's how much force would be needed to make it completely stationary. Potential energy can be looked at as how high the object is from the ground; a plant on your top shelf would have more potential energy than the same plant on a lower shelf - it would be more likely to break if it got knocked down. As an object falls, that potential energy is converted into kinetic energy using the conversion 1/2 v² = gh, where v is the velocity when it hits the ground, g is the force of gravitation, and h is the starting height of the object.

Ok. So that 10,000 m/s is our combined energy, both kinetic and potential. Let's assume the fuel tanks are empty; there's no stored chemical potential energy. So, if your ascent took 5,000 m/s of delta v and you're in a stable orbit, your craft is going 5,000 m/s. If your ascent took 8,000 m/s, and again, you've achieved a stable orbit, your velocity would only be 2,000 m/s. Even though your kinetic energy is smaller, your potential energy is higher, so the delta v required to get there is the same.

In short, just because the spacecraft is moving more slowly doesn't mean it needs less delta v. If it's in a higher orbit, you need more delta v to get it there, even though your velocity is going to be much slower upon arrival.

[skykooler]

OK. So where is it useful? It's not for straight vertical launches. But when you launch the exact same rocket into the exact same geosynchronous orbit every time, it will circularize at the exact same spot relative to the surface every time. If you put a space station into a geosynchronous orbit over that exact spot, you'll have a perfect encounter every time. It essentially gives you a launch window forever. This allows you to achieve encounters very easily. Unfortunately a geosynchronous orbit is really high and fast and you'll be able to build much smaller rockets if you just plan an orbital rendezvous instead.

That's exactly what I meant. Thanks for clarifying that!

[Lexif]

Untrue. For RemoteTech, you have to launch your first satellite directly into geosync from KSC without orbiting. You can't burn on the far side of Kerbin because you will lose communication there.

Not untrue. You can also launch a string of sats to a lower orbit, so that you have communications on the far side of Kerbin for your injection to a geostationary orbit above KSC. That's how I deployed my network, using three smaller comsats for incomplete coverage until the permanent sats were deployed to their geostationary orbits. Timing is critical, of course.

I also use two satellites on highly elliptic polar orbits for extra coverage that spend most of their time high above Kerbin's poles. They have a period of six hours, too. So I could imagine first putting a small temporary satellite into a low orbit, then using that at the right time to launch a polar sat that gives you full coverage for all higher equatorial orbits when it's above the poles (most of the time). Your third launch could then proceed to a geostationary orbit.

[AustralianFries]

Putting something into geostationary orbit is just like putting something into a 70km orbit. Since there isn't really a point for satellites yet, it's pretty much all the same. Geostationary just takes a bit more Delta V, and it looks way cooler.

[Fried]

this guy is very useful for getting to duna as the stage that burns me iitnto orb (if big enough) can be used to get partly to duna if refueled by him.

geostationary is actually the ideal place for it. (P.S. I built it then moved it from a 80km orbit took forever)

[rock3tman]

I use mine for an interplanetary staging point. I dock a big booster + lander/probes and fuel up then take off for other worlds.

Lemme tell ya, it was a pain getting 20+ tons of fuel up there and docked.

[lacedemonian]

What would the advantages be of a space station in a geosynchronous orbit around Kerbal? Would they make good refueling spots for missions to the Mun and beyond?

Okay, i am TERRIBLE at docking. Mostly because of my inability to cancel my relative velocity in time. But, if the object i want to dock with is geosynchronous, then i will actually approach the same spot with the same velocity with a ship to dock with as the original object, removing the guesstimation from docking.

[lacedemonian]

Geosynchronous orbit over KSC isn't the easiest thing. Correct me if I'm wrong but the only way to get there without waiting is to go straight up and not do a gravity turn.

You don't need to go right over KSC. Orbit as it comes naturally, then when you launch another rocket, your natural orbiting maneuvers will get you to the same spot.