Mars cycler campaign made safe with backup rescue cycler vehicle et cetera

[LocalFluff]

A Mars cycler has the risk factor of being a one shot chance for the crew launched from Earth or Mars to dock with it, because a cycler flies by at high speed (which has a good side too since travel time shortens). This requires lots of fuel for the ascent to it and the window it has to hit is narrow. I wonder if there are Kerbal, or other, ideas about how a mars campaign could be designed to minimize those problems. The great thing with cyclers is the reusability. A cycler is a permanent asset, like a railroad, which will always be improved upon and expanded.

I suggest the Mars cycler rescue vehicle. It would just be alot of fuel with a rocket engine. It would trail the real habitable Mars cycle transfer vehicle by a few days or so. If the crewed ascent vehicle misses the cycler, the rescue vehicle would consume its fuel to pick up the crew and still dock it to the habitable cycler. The rescue vehicle would only be consumed when it has to be used in an emergency, so it is economically semi-reusable.

Buzz Aldrin's Mars cycler is the luxury cycler, getting to and from Mars at every conjunction. But it is expensive since it requires orbital shift each time and arrives at high speeds. 7-year cycles, every third conjunction, are cheaper that way. Now, three of them probably isn't a smaller investment, but safer if one fails and the crew can stay an extra 26 months on Mars to await the next one. In the long run three 7-year cycles could be a better return on investment since it is cheaper to supply and has lower risk. In the beginning, crewed Mars missions probably won't be afforded more often than at every third conjunction anyway, so it could be a cheaper way to get started.  Two 7-years cyclers would be enough to do a Mars mission once every conjunction. One there, one back then wait. With SEP, more exotic cyler-like orbits are possible, but I think that it's difficult to calculate optimums for that so I just leave that out.

Crew launched from Earth should use a small capsule (like Orion, I think Dragon cannot sustain the crew for long enough in the following scenaria) on a super-heavy launcher to directly reach the relatively fast habitable cycler. When approaching Mars, a four stage vehicle should be used: Orion + aerocapture stage + landing stage + fully fueled ascent stage (might still need a approach speed braking chemical stage too). This vehicle would use aerocapture until in low Mars orbit. This would take almost as many days as the Orion can support the crew. When landing, it carries its ascent stage which makes it possible to abort back to orbit at any time during and after landing. In low Mars orbit, a fueled rocket stage has been preplaced. It could have a long-term habitable module as a safe haven if Mars' surface has to be left early and the next cycler awaited. The fuel of the preplaced orbiting stage would take the Orion to the cycler going home to Earth.

Before each mission, the two used cyclers are resupplied, the return fuel stage in low Mars orbit is replaced, as are any emergency vehicles consumed such as the cycler rescue vehicle or the habitat in low Mars orbit. All transported with economic SEP since there's no hurry without any crews onboard. Other upgrades of the cyclers and on Mars' surface are also ongoing during and between crewed missions.

So, what do you kerbals think of these ideas? Cyclers, rescue cyclers as backup, smallest possible crew transfer vehicles Earth-cycler-Mars-cycler-Earth, backup habitation in low Mars orbit. Landing on Mars with fully fueled ascent stage is expensive, but gives very valuable abort options during the most dangerous phase of the entire mission, and using aerocapture could cheaply shed the speed of even such a massive multi-staged spacecraft, I would think.

Has anyone tried any of these ideas?

Edited April 1, 2016 by LocalFluff
Fixing my typos

[superstrijder15]

Welcome aboard Fluffy,

I don't really know what you mean by your cyclers, but this is definetly now what you will do in ksp. Challenges is a place where you post a suggest for something to do, often hard. do you want us to do this? say more explicitly. no? than it should be moved to science & spaceflight.

Good luck,

me

[Rocket In My Pocket]

1 hour ago, superstrijder15 said:

Welcome aboard Fluffy,

I don't really know what you mean by your cyclers, but this is definetly now what you will do in ksp. Challenges is a place where you post a suggest for something to do, often hard. do you want us to do this? say more explicitly. no? than it should be moved to science & spaceflight.

Good luck,

me

To be fair this section of the forums is called "Challenges & Mission ideas."

This is most certainly a Mission idea, and quite an interesting one at that. Making a cycler to Duna would be quite impressive, and I'd love to see someone do this.

Maybe you should do some reading on the subject? https://en.wikipedia.org/wiki/Mars_cycler

[Jetski]

I want one. So the idea is a large luxurious ship on a permanent resonant orbit that intercepts Duna and Kerbin (Earth and Mars) in a predictable cycle with only tiny adjustment burns needed. No burns if we were real rocket scientists We use smaller high TWR intercept shuttles to catch it (kind of like meeting an asteroid) during flyby at both ends for crew transfers. Crew travels in comfort to or from Duna, and shuttles down at their destination. So we need 4 things for this to work:

The cycle ship, huge and packed with life support for the long trips

A fast Kerbin ground launched (recoverable?) rocket for crew

A Duna lander capable of catching the cycler and bringing them to and from Duna surface

Mining ops at Duna to keep everything fueled

 

You could even add a Duna orbital station and have a separate lander and shuttle craft, to meet there, then mine Ike for fuel instead

 

I love it. Make a leaderboard for most efficient (least dV crew from Kerbin surface to Duna surface) and a badge and you have a rad challenge. I'm happy to help if you need assistance. 

Suggest requiring a life support mod, and the usual no other parts mods or hyperedit ruleset. 

Edit: maybe also a bonus for largest mass cycler !

Edit 2: upon further reading, it appears the tug should dock to and travel with the cycler. And 2 cyclers would be better than one to shorted mission times. I'm doing this tonight. 

Edited April 1, 2016 by Jetski

[Jetski]

Got a rough start here.  Did some homework, and looks like the orbit needs to be something like this:

It puts me on a trajectory that is 5m/s from a Duna intercept, and 20m/s from a Kerbin intercept.  I think repeatable, but we shall see.  Probe in place now, next pass I plan to have my cycler catch up and meet with the probe!

As I see it , this is  a variation on what some of us have done with Grand Tours and ion missions: just don't burn down into the gravity well.  Main ship stays on a high elliptical orbit, and landers or tugs get down and dirty with the planet.  This is the same idea, but skipping even the capture burn or aerobrake into orbit.  Like the highest elliptical orbit possible

 

Edited April 2, 2016 by Jetski

[superstrijder15]

On 1-4-2016 at 2:50 PM, Rocket In My Pocket said:

To be fair this section of the forums is called "Challenges & Mission ideas."

This is most certainly a Mission idea, and quite an interesting one at that. Making a cycler to Duna would be quite impressive, and I'd love to see someone do this.

Maybe you should do some reading on the subject? https://en.wikipedia.org/wiki/Mars_cycler

I'm sorry, I thought that OP wanted to talk about if this is how we should organise or would organise future mars missions. The wikipedia page is kind of scientific, but I think I get the idea now. This would be a cool mission to execute, but I'm afraid it got to wait till I got a better cpu: ksp lags to 10 fps when I launch things with 150 parts 

[max_creative]

So it goes between kerbin and Duna with only small correction burns, and would be caught up with by using a small, very fast ship sorta like the Hermes in the Martian? And the shuttle would be the resupply ship? Ok... Can't be that hard right? And it would save a lot of Delta-V! Do we get extra points if we use this?

[wibou7]

This sound very interesting, I'm going to follow this thread closely.

Any hints on how to setup the cycler orbit, @jetski? Did you just bruteforce it or was it math involved?

[Jetski]

The math has been done to a certain extent, but only for one type of cycler. Leave when Duna is 54.51 degrees ahead in orbit, and use 1491 dV from a 100k orbit. Juuuust miss a Duna intercept, and when you leave Kerbin soi you should be really near a kerbin intercept after 1 orbit. Easy so far. The trick is that the Kerbin intercept has to happen when kerbin is 54.51 degrees from Duna again, but advanced in orbit. Then you have to burn as you flyby Kerbin to get the same results again, using high TWR engines for precision.  You meet kerbin at a different place each time, but always at the same Duna transfer window. Try it with infinite fuel, a probe core and an engine to get the feel for it first. It's hard, and I'm not entirely pleased with my results. 

There is supposed to be a better orbit requiring no maintenance, or less at least, that takes longer. The synodic period is greater, so a more elliptical orbit. Maybe easier not to enter Kerbin SOI given ksp physics, but then you don't get a correction from gravity slingshot. I can't find math for the bigger orbit, but maybe someone else can...

Edit: upon a more careful reading of OP, this is the 7-year cycle @LocalFluff mentions.  So just meet back up with Kerbin every 7 years in the same spot I think.  Haven't tried yet, recently obsessed with Jool cycling

Edited April 7, 2016 by Jetski

[garthako]

hmm, so if you only have a rendevouz with kerbin, but no orbit, doesn't that also mean that you need to achieve the same delta-v as the cycler in order to perform a docking maneuver? I mean, it is a cool thing to do, but actually I cannot see where this would lead to saved resources.

Edited April 5, 2016 by garthako

[septemberWaves]

14 minutes ago, garthako said:

hmm, so if you only have a rendevouz with kerbin, but no orbit, doesn't that also mean that you need to achieve the same delta-v as the cycler in order to perform a docking maneuver? I mean, it is a cool thing to do, but actually I cannot see where this would lead to saved resources.

It doesn't seem useful at first, and it really isn't useful for transporting anything which doesn't have a constant drain on resources, but when playing with a life support mod this should be an incredibly good way of transporting crew. The reason is because you can have an enormous transfer vehicle containing enough supplies for decades (so you will only have to resupply it every couple of missions), and although putting it into the cycler orbit will take a lot of propellant, you only need to do that once (and with the ideal orbital configuration, correction burns should be minimal). Then you can use a crew pod without enough life support to make the entire interplanetary transfer, but plenty of life support for the much shorter amount of time that it takes to reach the cycler mothership.

This method of doing things means that instead of spending large amounts of fuel to get your interplanetary mothership in and out of several different planets' orbits, you only use the large fuel cost to get it into interplanetary transfer once, and then you use a smaller amount of fuel for a less massive spacecraft to dock with the cycler.

The cycler method is probably pretty pointless for anything uncrewed, but when you have a mod that makes your kerbals deplete resources constantly, it can be an incredibly cost-effective way of accomplishing large numbers of crewed missions. I'm thinking of figuring out a cycler orbit that I can use for my Jool 500 challenge when the necessary mods are updated, as it'll make the life support mods a lot cheaper to deal with.

[Jetski]

If you Google this topic, you will see nearly the same conversation on every thread, so let's get it out of the way.  This cycler orbit has no profitable application in stock.  Period. Too much dV to catch up, etc. It becomes valid IRL, and playing with a life support mod. Greenhouses, exercise rooms, heavy cosmic radiation shielding, and gobs of life support on the cycler make it very profitable to have all your infrastructure on a heavy ship, and light fast shuttles for transfers.  Kudos to anyone who does the math for Jool, I am also interested if using it for large scale transfer when 1.1 drops 

[max_creative]

If you have cargo, flotillas are the way to go. They don't have wobbly orbital assembly's or annoying docking like motherships. And they don't waste fuel with not effectine trajectorys. So for cargo, stock or modded, flotillas are the best. You might want will need KAC though.

[Jetski]

3 hours ago, max_creative said:

If you have cargo, flotillas are the way to go. They don't have wobbly orbital assembly's or annoying docking like motherships. And they don't waste fuel with not effectine trajectorys. So for cargo, stock or modded, flotillas are the best. You might want will need KAC though.

Lots of ways to move cargo. This is specifically for a nearly 0dV transfer orbit that can be reused indefinitely without burning more than tiny corrections once the orbit is set up. Ship can get as big and wobbly as you want, even add more stuff each resupply transfer.  Exciting stuff

[Jetski]

OK, after some research on this, I've found at least a semi useful application for this on Jool transfers.

1.  Take the big life support ship, burn at a normal transfer window to Jool (transfer window planner or eyeball it).  
2. Get your intercept like normal, plan for a nice gravicapture or aerobrake once the big heat shields are available in a week.  
3. A good ways out, (however long your small shuttle life support can handle), detach and coast.  
4. Once you have separation, do a small correction burn with the cycler (the further you are out the less dV of course) and watch your post-Jool orbit.  
5. Try to move it around with a manouver node until you have a Kerbin intercept ABOUT 10 EARTH DAYS (or 15 degrees) FURTHER ALONG IN KERBIN ORBIT THAN WHERE YOU DEPARTED*.  (*see math below). This sets you up for a Kerbin flyby, and you are positioned at the optimum Jool transfer window again.  I used a 2 year orbit (quite fast) but you could make it slower and get the same results.
6. Again, about 5-10 days out from Kerbin, adjust your flyby to use Kerbin's gravity assist to lob you back to Jool intercept.  You may have to burn at Pe if you can't get the right intercept, so swing by close to Kerbin.
7. Once you have your flyby set up, look at the orbit, and launch your shuttle, and set up your meeting like an asteroid meetup.

 

*OK, so the math as I see it is fairly straightforward.  Note these are Earth Days, not Kerbin Time

• Kerbin orbits Kerbol in 106.5 earth days.  
• It has a synodic period with Jool of 116.8 days. From Britannica: The synodic period of a planet is the time required for the Earth to overtake it as both go around the Sun—or, in the case of fast-moving Mercury or Venus, for the planet in question to overtake the Earth. 
• This means, Jool is at a similar window to Kerbin every 116.8 days, call it 82.1 degrees ahead, best time to transfer (ignoring inclination)
• As long as you keep intercepting Kerbin when Kerbin is 82.1 degrees trailing Jool, you always catch the same transfer window
• So you should try to meet Kerbin 116.8-106.5 = 10.3 Earth Days after the point in orbit which you left.  This is very roughly 1/10th of an orbit, or 15.8 degrees unless my math is off.

Bear in mind this is very Kerbal math, and rough at best.  You won't get a magic cycler that doesn't need adjustment.  But you will get a permanent trajectory that keeps intercepting both in a useful manner with only tiny correction burns, which appears to be a practical application of this concept. I welcome any corrections to this math, or this whole concept clarified.

An extremely clever pilot could even do the following: enter Kerbin->Jool transfer windows into the Transfer Window Planner (amazing mod BTW) and plan a larger orbit to meet back with Kerbin only at the truly ideal transfer window, instead of just this rough estimate.

 

Also synodic period calculator available here.  Wasn't comfortable converting to Kerbin time, so all this is in Earth days.

 

 

Edited April 7, 2016 by Jetski

[septemberWaves]

I'd like to add that in examples of cycler orbits I've found, theres a few things that seem quite common:

1. The orbits often account for both transfer windows (e.g. Kerbin ==> Duna and Duna ==> Kerbin).
2. The cycler orbit tends to have a higher apoapsis than the outer planet and a lower periapsis than the inner planet, to allow it to fly by them at transfer windows in both directions.
3. The transfer windows usually aren't the normal Hohmann transfers; instead they are slightly less efficient transfer windows to enable the previously mentioned conditions, and also to reduce the time the crew would spend in space.
4. Perfect cycler orbits have an orbital period that is an exact multiple of the synodic period of the two bodies the cycler transfers between.