Help, interplanetary transport net idea which I cant remember.

[AngelLestat]

2 years back or more, someone post an article about an interplanetary net-web made by many different transfer ships in particular orbits which purpose was reduce deltav, increase launch windows and short travel time.

It accomplish this by a combinations of circular and eliptic orbits which join in their periapsis / apoapsis (where transfer between ships happen).

The orbits was sincronize to match the period of the ships to change between orbits.

So to go from earth to venus or mars, you just needed to travel using these crafts in orbits and jumping between them until you reach destination.

Sorry that I can not provide more info, I will find it my self if I could.

Someone remember this?

I remember an animated graphic showing all the process.

Edited February 9, 2015 by AngelLestat

[Redjoker]

I'm not sure if this is what you are looking for: http://en.wikipedia.org/wiki/Interplanetary_Transport_Network

[UmbralRaptor]

Aldrin Cyclers, maybe?

[AngelLestat]

none of those.

Imagine like 10 or 12 space vehicles always in the same orbits, a combination between elliptical orbits, lets imagine 4 orbits around the sun which join in its apo with earth orbits (or not, i dont remember the right config), 4 orbits around the sun that join with venus orbit, then 4 orbits alround the sun that joins the other 8 orbits.

In each orbit there is a transfer ship, their periods sincronize between them, so you can do transfers between ships and orbits when this happen.

So you end it with a transport system with a lot extra time windows and lower deltav.

It was an animation showing all the orbits and its ships. maybe 2 ships by orbit, not remember.

I was looking by images or different keywords and nothing.

[*Aqua*]

Why should that lower the energy requirements? Two orbits which intersect at the apoapsis of the first and the periapsis at the second don't have the same speed at that meeting point. You need to accelerate/brake to transfer stuff. That requires at least the same energy you'll need for a direct approach.

[moronwrocket]

I think I've heard of a similar idea, that used rotating space stations to match delta-V. Basically, the station maintains an edge rotational speed to align with the transfer speed at the node. So if a traveller is coming up at a relative speed of 100m/s, the station changes the rotation speed to align with the incoming traveller, and "captures" it at a low relative speed on its surface. Obviously, with this you would need precision maneuvering and timing since you only have one chance, so no humans need apply. The long travel time between nodes would be spent accelerating/decelerating the rotation to match the destination requirements.

I don't think it would work long-term because of perturbations though. And if you have the capability to launch a giant space station into such an orbit, you could easily do a direct injection anyways.

TANSTAAFL, so the station would still have to expel mass to stay aligned with its orbit after capture, but perhaps it could do that more efficiently than a smaller vessel. Unless you really got fancy and launched *two* matched-mass travellers, one caught on each side of the ring at the same time and matching the rings velocity. Left as an exercise for the reader.

[*Aqua*]

Left as an exercise for the reader.

Because of the greater mass of the station-with-two-docked-vessels the orbit will change. So now you have to move an even greater mass to correct your orbit. And you have to expend energy to adjust the rotation speed.

I still can't see any benefit in doing this.

[AngelLestat]

*Aqua*: I dont remember how the mechanism was, that is why I wanted to see it again so I have a better opinion.

It can be as moronwrocket said, a rotating station, you dont need to waste propellant to increase or decrease your spin rate, just electricity.

You can distribute masses on the rotating space station so the capture does not produce destabilizations.

Of course you need to bring with you all the resources that you will consume in the whole trip.

Even if you need to bring the proppelent to acomplish all deltaV changes. It will be lower, because you just need to have a tiny ship to move from one station to the other, so you avoid spent propplent in the confort habitat aspect.

I am not saying that it will have sense now, but in the future you can not transport normal civil in cans.

But I will like to see again this orbit pattern and animation, it may have uses for other things.

It was posted in the forum, but the forum had a wipe long time ago.

I remember that some players wanted to copy that orbit net in ksp

[KerBlam]

If I'm not mistaken, the orbits would have to be exactly the same size, around bodies the same size (unless the orbit is perfectly circular, which I imagine defeats the purpose) and travel in the opposite direction from each other, the apoapsis would have to line up exactly or it would drift.

[UmbralRaptor]

I'm guessing that AngelLestat is slightly misremembering things. Next attempt: skyhook or some related momentum transfer system

[AngelLestat]

I remember something very clear, some of the orbits were very elliptical.

About how the trasfer ships looks like I dont really care.

The thing I want to see again is that particular orbit net pattern with synchronized periods.

And to be clear, are not Aldrin Cyclers.

There was not gravitation assist in them.

[Rakaydos]

And to be clear, are not Aldrin Cyclers.

There was not gravitation assist in them.

That pretty much elimiates everything.

[B787_300]

techically Aldrin Cyclers do not rely on gravitational assists

An aldrin cycler would move between orbits with very little to no fuel needed and just drop modules at the destination

[Rakaydos]

techically Aldrin Cyclers do not rely on gravitational assists

An aldrin cycler would move between orbits with very little to no fuel needed and just drop modules at the destination

Aldrin Cycler is a specific mars cycler orbit that DOES use gravity assists, in order to change it's orbit to intercept both earth and mars at every conjunction.

The most basic, no-slingshot cycler only intercepts the conjunction every 7 conjunctions, because the other 6 happen elsewhere in solar orbit.

[Damien_The_Unbeliever]

I'm just not understanding how this is meant to work. If you have two objects in (approximately) the same location at the same time, and with the same velocity, then they are in the same orbit. You can't have one of them be in an elliptical orbit and the other in a circular orbit.

If two objects are close together at the same time but are in different orbits, then to move from one to the other, you need to expend the same delta-v as would be required to detach from one object and then to alter your orbit to match the second object's orbit, whether or not it even existed.

Edited February 10, 2015 by Damien_The_Unbeliever

[Stargate525]

I can see what he may be talking about. Yes, you need to expend the same amount of dV to get out to wherever your destination is, but you'd only have to spend dV to move yourself, your cargo, and a minimal transfer vehicle.

Instead of the life support and habitation to last you the whole length of the journey. It's like the cyclers, but linked up into a sort of interplanetary rail network.

[AngelLestat]

Well, I give up, I cant find it.

I already try with all these keywords and combination:

orbits, transfer, interplanetary, system, station, transport, net, network, venus, earth, pattern, launch windows.

Nothing, I dont remember the name, but I know that it was posted in KSP forum long time ago, before the wipe.

I made a graphic trying to remember the pattern, but I fail.

I know that it dint look like this, it was different, not sure how, but I post it anyway to see if someone has a flashback and remember something.

The real picture was animated, it showed how a ship move it between the elliptical and circular orbits, until find the shortest route to the planet. The transfer time was the same I guess, but you find it multiple launch windows.

It was all syncro between the planets movement and the orbit stations.

I guess it was only with venus earth, because mars eccentricity is not good enoght to this.

[Nibb31]

That looks like a variant of a series of Aldrin Cyclers.

Still, however you turn it around, transferring from one orbit to another requires at least as much dV as you would spend to get to that orbit in the first place. If the cycler is just a dumb hab, it still needs supplies, spares, and propellant, and you still need to accelerate all that stuff to the dV of the first orbit, and then the second orbit. It's wasteful.

[AngelLestat]

I dont see any comparison Nibb, also take into account that honestly, I dont remember how the shape pattern was.

It was explained many times in this thread that you only need to use deltav for a small and light transfer vehicle, which only duty is to carry people and provisions.

Lets imagine that the transfer vehicle mass that jumps between stations is 2 tons, meanwhile the space stations are 20 tons.

Also if the space station are rotating, you dont need extra deltav, but you need more accuracy.

You have more time windows to launch, and you can chose the orbits you want to reach the planet in less or at least the same time than a normal transfer in perfect time windows launch.

This has sense in the future, because you can not put normal people in cans over 100 or 150 days.

[Nibb31]

I dont see any comparison Nibb, also take into account that honestly, I dont remember how the shape pattern was.

It was explained many times in this thread that you only need to use deltav for a small and light transfer vehicle, which only duty is to carry people and provisions.

Lets imagine that the transfer vehicle mass that jumps between stations is 2 tons, meanwhile the space stations are 20 tons.

Also if the space station are rotating, you dont need extra deltav, but you need more accuracy.

You have more time windows to launch, and you can chose the orbits you want to reach the planet in less or at least the same time than a normal transfer in perfect time windows launch.

This has sense in the future, because you can not put normal people in cans over 100 or 150 days.

It can't be "only 2 tons", because it needs a massive amount of fuel to transfer from one orbit to the other. 2 tons is barely enough for just the pressure shell and avionics. The IXV that we are all watching now is 2 tons, and it's bareley big enough to carry some instruments and a small RCS system. If you want to carry a few people and the supplies to keep them alive for the journey, we are talking about at least 20 tons (which is basically what Orion weighs). To that, you have to add the weight of the propellant for the transfer, and the extra propellant that you would need to refuel the cycler for station keeping and orbital adjustments.

Rotating stations don't make things easier, because we are talking about thousands of m/s of delta-v between the two orbits.

Edited February 11, 2015 by Nibb31

[*Aqua*]

@AngelLestat

Now I understand what you are up to. That station is used as a reusable "hotel" or "taxi" so that you don't need that much life support on the transfer vessels from and to the station. Using this principle you don't need a fully featured space cruiser everytime you send people over interplanetary distances which then will be abandoned at the end of the mission.

I'm not sure if that makes a transfer cheaper over time. The station has to be resupplied and it's not really in an easy to reach orbit. The course correction is also pretty difficult (large mass, change in mass on docking, precision needed, etc.) Also machines wear down. How long can a space station survive like that? Afaik the radiation is a big problem.

[AngelLestat]

It can't be "only 2 tons", because it needs a massive amount of fuel to transfer from one orbit to the other. 2 tons is barely enough for just the pressure shell and avionics. The IXV that we are all watching now is 2 tons, and it's bareley big enough to carry some instruments and a small RCS system. If you want to carry a few people and the supplies to keep them alive for the journey, we are talking about at least 20 tons (which is basically what Orion weighs). To that, you have to add the weight of the propellant for the transfer, and the extra propellant that you would need to refuel the cycler for station keeping and orbital adjustments.

Rotating stations don't make things easier, because we are talking about thousands of m/s of delta-v between the two orbits.

2 tons is the dry mass..

which do you prefer? a deltav change of 3,2km/s on 22 tons dry mass or a deltav change of 5km/s on 2 tons drymass?

We are talking of comfortable transfers.

Also we are talking on future, that is why the dry mass of the transfer vehicle is 2 tons and the dry mass of the space station is only 20 tons.

About food for the whole trip, that is almost imperceptible.

And remember that I dont know how the real shape and orbits are. If someone find the animation that I am talking about, we can take sides, maybe I will notice that the idea is trash or not.

So not sure of the deltaV changes.

About the rotation speeds of the space station, if your space station radius is 10 meters, with 9m/s in tangent speed to get 1G on artificial gravity, if you have wires that extend to 2 km, the tangent speed there is 2000m/s

@AngelLestat

Now I understand what you are up to. That station is used as a reusable "hotel" or "taxi" so that you don't need that much life support on the transfer vessels from and to the station. Using this principle you don't need a fully featured space cruiser everytime you send people over interplanetary distances which then will be abandoned at the end of the mission.

I'm not sure if that makes a transfer cheaper over time. The station has to be resupplied and it's not really in an easy to reach orbit. The course correction is also pretty difficult (large mass, change in mass on docking, precision needed, etc.) Also machines wear down. How long can a space station survive like that? Afaik the radiation is a big problem.

Space stations does not need to be resupplied, if they need, arejust small things, anything you will consume over your whole trip from station to station (which can not be recycle in this one) it will be carry in the transfer vehicles.

You dont need to carry water and oxygen because these can be recycle almost at 100% in the space stations.

Solar panels or anything to sustain an ecosystem is not needed.

You just need to carry your food and proppelent, human wastes can be use it to produce proppelent that will keep the station in perfect orbit.

But I need to look in the real idea to have an opinion if can work or not.

Edited February 11, 2015 by AngelLestat