Cycler Ships

[Laie]

If you spend all that dV to match the trajectory of the cycler and kill relative velocity, wouldn't it be basically the same as just launching yourself to mars with the same dV? Or is there something I fundamentally misunderstood here? I am not very knowledgable about astrophysics.

We've been over that twice in this thread: the cycler is effectively a satellite on a solar orbit, that will in recular intervals pass close to earth and mars. The idea is that the cycler consists of all the stuff that is heavy, bulky, and re-usable.

The *capsule* needs just as much fuel as if it was going directly to Mars. Actually, a bit more, and it will be constrained by the cyclers' timetable. The benefit is that you only need to send a small capsule with crew and supplies, pretty much apollo-style: no bunks, no showers, no nothing. All of that is on the cycler and remains there.

[Northstar1989]

Said it better than I could have Laie.

Actually, you could do it LIGHTER than Apollo-style, though. A Mercury-style capsule (or even better yet from a mass-perspective, an UNPRESSURIZED capsule, if you can convince an astronaut to sit in his suit with an O2 and H2O line hooked up and probably some small chewable snacks for 24-48 hours for the rendezvous+docking with the Cycler ship...) would be an even cheaper solution to get the astronauts from LEO onto the Cycler Ship...

Regards,

Northstar

[K^2]

Cycler transfers are going to be time-consuming. You don't want cycler to pass near LEO. In fact, you don't want it even clipping the Hill Sphere. So we are talking days if not weeks of transfer from LEO to cycler. Ditto transfer to a Mars station. So realistically, we're still looking at something like Apollo or even Orion capsule.

On the other hand, cycler isn't limited to just your typical orbital facilities. Since people would need to spend 7-8 months at a time on an Earth-Mars cycler, I'd strongly advise something with artificial gravity. Probably something along the lines of a living module connected by light, extendable walkway/umbilical/tether to a massive power and life support system. A small hub in the center can house solar arrays and a docking port/airlock. Not having to deal with drag and tidal forces gives a cycler a whole lot of advantages over an LEO station. Ability to spin without any problems is one of them.

[Bill Phil]

We should probably do something more sensible before cyclers though...

Maybe a station a la Skylab near the Moon (at a stable L-point)?

[Rakaydos]

We should probably do something more sensible before cyclers though...

Maybe a station a la Skylab near the Moon (at a stable L-point)?

the stable lunar lagrages (l4/l5) arnt exactly "near" the moon. they're as far from the moon as the moon is from us.

The L1 and L2 can have elevators, though, dealing with the instability by drilling into the lunar surface. L3 is pretty much useless.

Moving earth-crossing asteroids is a good prior step to cyclers, though. Why send the mass of a cycler into LEO, when you can redirect an asteroid into a cycler orbit, and build the cycler into it, using it for raw materials and heavy radiation shielding.

[K^2]

Even with boost to LEO, moving a simple station built out of light, modern materials feels like way less effort than shifting an orbit of asteroid of comparable size even a little. ISS is what, about 100m across? An asteroid of the same diameter would be well over 1M tons.

[Rakaydos]

Even with boost to LEO, moving a simple station built out of light, modern materials feels like way less effort than shifting an orbit of asteroid of comparable size even a little. ISS is what, about 100m across? An asteroid of the same diameter would be well over 1M tons.

How much radiation shielding do "light modern materials" provide? Considering this station is going to be all on it's own in the worst of solar storms, I would think an ion or solar sail gravity tractor to move an asteroids would be more effective, than a lifter that makes the SLS cry.

[K^2]

I'm picturing this cycler as a modular station, so it could be built with modern lifters, but SLS would make it easier.

Radiation shielding is a problem. But Solar radiation is mostly charged particles and gamma, which are much easier to shield from than, say, a nuclear reactor which produces a lot of neutron radiation. Having a few layers of scintillating and conductive materials should do the trick on shielding, I think. I should do the math on this at some point to be certain, though.

[Bill Phil]

Even with boost to LEO, moving a simple station built out of light, modern materials feels like way less effort than shifting an orbit of asteroid of comparable size even a little. ISS is what, about 100m across? An asteroid of the same diameter would be well over 1M tons.

Why get one of equal size, when you can have an asteroid that's only a few times bigger than a bus...

[Northstar1989]

K^2 said:

Cycler transfers are going to be time-consuming.

Actually, not. They're faster than a direct Earth-Mars transfer, because a typical Earth-Mars transfer will take a longer (slower) transfer trajectory... With a Cycler, you actually *HAVE TO* take a shorter trajectory in order to create the correct resonance with the orbits of Earth and Mars.

Which means, more Delta-V to accelerate to the Cycler orbit than to accelerate the same craft to a typical (slow) Earth-Mars transfer-orbit, BUT you can accelerate with as low a TWR and over as long a period of time as you like, as astronauts don't have to be onboard during the initial acceleration, as the Cycler will swing back by Earth over a year later... Which means you can use things like ion engines and solar sails and take (potentially) YEARS to reach the initial Cycler orbit, if you want... (*IF* you time it right so that the spacecraft will reach the Cycler orbit at the correct phase/time for an Earth/Mars resonance- but space agencies are *VERY* good at timing the launch and burns of interplanetary ion-powered probes correctly, and this is extremely similar...)

K^2 said:

You don't want cycler to pass near LEO. In fact, you don't want it even clipping the Hill Sphere. So we are talking days if not weeks of transfer from LEO to cycler. Ditto transfer to a Mars station. So realistically, we're still looking at something like Apollo or even Orion capsule.

This is a classical trade-off situation. The closer the Cycler passes to Earth, the greater its trajectory-correction Delta-V requirements will be (although it is possible to orient the flyby such as that the gravity pulls the Cycler in a less disruptive direction to its orbit, not all directions of trajectory-perturbation being equal...) But the closer the Cycler passes to Earth, the smaller/lighter your interceptor-ships can be, and the less time your astronauts will have to spend in a cramped capsule with minimal amenities before reaching the (relative) comfort of the Cycler Ship...

Course-corrections can be made over time with things like solar sails and ion engines (provided the gravity of Earth doesn't pull the Cycler too far off-course), so in actuality it's not nearly as big of a deal to pass (relatively) close to Earth as you think. I'd imagine a Cycler passing by somewhere a bit beyond the Moon's orbit, so as to allow VERY small/light (possibly even unpressurized) interceptor-ships to be utilized- which it might make sense to have on standby in orbit of the Moon (so you can keep your astronauts in a slightly larger spacecraft/station before boarding the interceptor-ship), if you can time it right...

K^2 said:

On the other hand, cycler isn't limited to just your typical orbital facilities. Since people would need to spend 7-8 months at a time on an Earth-Mars cycler, I'd strongly advise something with artificial gravity. Probably something along the lines of a living module connected by light, extendable walkway/umbilical/tether to a massive power and life support system. A small hub in the center can house solar arrays and a docking port/airlock. Not having to deal with drag and tidal forces gives a cycler a whole lot of advantages over an LEO station. Ability to spin without any problems is one of them.

Indeed. I think having artificial gravity (and probably some greenhouses- both for regenerative life support and crew-morale, from being able to see something growing) goes without saying. As well as LOTS of probably very heavy radiation-shielding (which is where having to launch/accelerate the Cycler Ship only once comes in handy vs. a fleet of direct Mars-transfer vehicles), active cooling systems and heavy insulation for cryogenic fuels (which can be utilized on lightly-insulated vehicles that depart from the Cycler Ship: if you use a single-propellant propulsion system like a Microwave Thermal Rocket, it may even be worth transporting CARGO on the Cycler Ship, so as to be able to utilize Hydrogen for the Mars capture-burn rather than a heavier and more storable propellant with lower ISP...), and a much more spacious crew-quarters than you would want to accelerate to Mars on a ship that didn't get a free return to Earth...

The Earth-Mars transfer time is *ONLY 5 MONTHS* on an outbound (you need two: one inbound and one outbound, which have the same orbital parameters but differ in phasing angle relative to the Sun) Aldrin Cycler, by the way. Which is actually MUCH shorter than the transfer-times proposed for most Mars missions- and you only have to pay the Delta-V cost for that ONCE (and can do it unmanned with high-ISP systems like ion engines), but can use the Cycler Ship again and again...

Regards,

Northstar

Edited February 23, 2017 by Northstar1989

[Rakaydos]

Hmm... if we built a lunar lagrange elevator through the L2 point, how high would it have to be to simply drop a payload from the end, into a mars cycler trajectory?

[Northstar1989]

Hmm... if we built a lunar lagrange elevator through the L2 point, how high would it have to be to simply drop a payload from the end, into a mars cycler trajectory?

"Simply Drop"??? I hope you mean how tall would it be to eliminate the need for a climb to that altitude, and the answer is dependent on how close to Earth the Cycler Ship was designed to pass. A closer pass by Earth would reduce the time needed to rendezvous- thus allowing smaller/light interceptor-ships to be used, but would also increase the Delta-V requirements for trajectory-corrections...

Regards,

Northstar

[Northstar1989]

Ummm, sorry for the necro guys, but has there been any news about cycler ships in-game recently? That is, has anybody actually attempted to build one recently?

Cycler Ships should be possible in KSP- you basically just need an orbit that leaves Kerbin, passes close to Duna, and comes back to Kerbin a bit further along in its next orbit with a small adjsutment-burn near apoapsis (not exactly the same as a Cyler Orbit in real life due to the restrictions of two-body physics, but close enough...) Is anybody crazy enough to actually give this a try?

 

Regards,

Northstar

Edited February 23, 2017 by Northstar1989

[Northstar1989]

This is still the most relevant thread to this topic- and a topic still worth discussing.  So rather than create a duplicate thread, I'm going to try to revive it...  Does anyone have any thoughts about Cycler Ships?  Have there been any attempts to create one in KSP?  I'm thinking this guy might be a good one to do it, as he already LOVES his gravity-assists:

 

Regards,

Northstar

 

Edited February 23, 2017 by Northstar1989

[Northstar1989]

So... as some reading this thread may know (I hope somebody reads this), O created a Mass Driver Mod for KSP a while ago, and recently got it updated for 1.2.2 and even expanded its scope:

 

Which got me thinking- a spacecraft designed to carry crew to Low Earth Orbit from a mid-sized Mass Driver (let's say one that can shoot craft above the atmosphere, but with less horizontal velocity than something like the StarTram Gen 2 design) actually shares a lot in common with an Interceptor Ship designed to rendezvous with a Cycler...

For one, both craft need a fairly high Thrust:Weight Ratio with a vacuim-optimized engine and a good chunk of Delta-V, but not enough to justify a second stage and the complexity/cost it adds.  A Mass Driver launched capsule needs to circularize its orbit when it ascends above the atmosphere, but it will still probably carry a reasonable chunk of velocity with it from the Mass Driver launch (StarTram requires less than 1 km/s to circularize, a less powerful, more economical Mass Driver might require 3-4 km/s to circularize if I were to guess...)  An Interceptor Ship needs to reach a fairly high-speed interplanetary trajectory, but probably would still only comprise a single stage...

Another commanality is the need to deal with fairly large amounts of heat- the Mass Driver fired capsule during its ascent, where it starts out at high-hypersonic velocities in the lower atmosphere (the 2nd Gen version of StarTram has an insane scheme for extending the firing tube into the upper atmosphere, but I'm assuming most actual, practical man-rated designs would look like their Gen 1 design- with a tube originating a bit underground and climbing/boring up the side of a mountain to fire near the peak...) an Interceptor Ship during Mars re-entry after detaching from the Cycler Ship (using the Interceptor Ship for this purpose would be simpler than having a dedicated lander, although a bit less mass-efficient)

Both craft need to be very compact in their design, and would optimally not be designed to support humans for a long period of time, but instead carry a crew of humans and perishable cargo a short distance very mass-efficiently (the Mass Driver capsule because unmanned vessels can be accelerated through the Mass Driver at much higher g-forces, and thus can be fired from a seperate, shorter, and much cheaper Mass Driver like the Star Tram Gen 1 design- or alternatively be fired from the same Mass Driver at a much higher velocity, and thus require less Delta-V to reach otbit) where they would meet up with unmanned craft to hold the crew long-term.

And finally, both craft need to be capable of docking and loading/unloading its crew and cargo, including fuel.  A Mass Driver capsule because the entire architecture of a Mass Driver system relies on firing lots of small spacecraft very frequently, to limit the size and power of the Mass Driver needed to accelerate spacecraft to a suborbiral trajectory, and amortize the costs of the Mass Driver over many launches (so an ideal Mass Driver capsule would probably only carry one or two people- just like an ideal Interceptor Ship approach would be that of a "swarm of ants"- both to allow launch of the Interceptors on smaller rockets, and to provide an abort-mode if one Interceptor should experience a failure and require rescue before reaching the Cycler Ship...) an Interceptor Ship, well, because docking with the Cycler Ship is its entire purpose.  Neither ship type would work well as an all-inclusive design that carries out its entire mission without needing to ever dock with another spacecraft.

 

So, all of this leaves me wondering- would there by synergy between the two technologies? (Mass Drivers and Interceptor Ships)  I can certainly imagine engineers designing a rocket that meets the operational requirements of both missions.  And in some ways, the requirements on a Mass Driver capsule are actually harsher (higher atmospheric heating, higher g-tolerances required from the structure, potentially greater Delta-V requirements, and more need for reliability: as engine-failure on a suborbital trajectory means smashing into the ground or burning up during re-entry before you have time to attempt any fixes to the problem)

At the very least I would think that a Mass Driver launch system could make ALL space exploration more affordable and provide a cheap way to launch the pieces of a Cycler Ship in many modules (a Cycler Ship would look a lot like a space station in design and construction, as the ability to accelerate it to its orbit with ion engines neans that it would experience VERY low g-forces after each piece reaches Low Earth Orbit.  In fact there's theoretically nothing stopping you from strapping an ion propulsion stsge to the International Space Station and using *IT* as a Cycler Ship...)  In a best-case scenario a capsule designed to carry crew to LEO with a Mass Driver would also make an ideal Interceptor: although admittedly so would something like the Orion Capsule...

In fact, all this me an idea- what if NASA tried to go to Mars with nothing but what they had in the next 10-12 years?  I mean what if they *LITERALLY* evacuated the ISS of all crew, strapped a VASIMR or large cluster of existing ion engines to it and accelerated it to an Aldrin Cycler Orbit over the course of a few years (including maybe some gravity-assists from the Moon and Earth), and then used an Orion or a modified Red Dragon (SpaceX's coming Mars capsule) as an Interceptor Ship to rendezvous with it the next time it passed by Earth? (the Red Dragon, at least, should have enough fuel to orbit Mars and then return to Earth- the Orion would probably have to limit itself to establishing orbit and then docking with a return-vessel waiting around Mars: perhaps one of the Orion variants NASA was looking at using for a Mars flyby sent unmanned via a transfer-stage so it had enough fuel to return to Earth...)  A silly idea I'm sure (what would be the point?  This seems like it would be a waste of the ISS), but amusing to imagine nonetheless...

Anyways, to return to my discussion from before- I can imagine a lot of potential synergies between  Mass Drivers and Cycler Ships.  Not the LEAST of which would be to someday in the distant future be able to set up a Mass Driver powerful enough to send an Interceptor Ship on an escape trajectory (or at LEAST a very high suborbital trajectory with an apoapsis close to the Moon...) in the general direction of the Cycler Ship when it swings by Earth...

 

Anyways, try not to hate on my insane, crazy-big ideas here.  At least I KNOW these are crazy, nutso ideas compared to anything I suggested before (like classical Cycler Ships, which are an idea that goes all the way back to before Buzz Aldrin- and are actually in many ways EASIER to implement as a mission-architecture to get to Mars than something like the Mars "Constellation" misdion plan, for instance, with its many more highly-specialized vessels and longer Mars transfer-times for the crew...)

 

Regards,

Northstar

Edited February 27, 2017 by Northstar1989