Recovering parts from the Munar surface

[Fearless Son]

Okay, so I wanted to build a little funding before starting bigger ventures and I was in the mood to head someplace close to home, so I picked up a contract to rescue a Kerbal and their part from the Munar surface.* 

It looks like the part in question is a two meter by two meter object, so I am trying to think of the best way to get this thing secure and returned to Kerbin.  There will obviously be some Advanced Grabbing Unit shenanigans involved, but how exactly I will perform this recover is tumbling around in my mind.  

I want to crowdsource some potential solutions to this contract.  What ideas have you experimented with and found functional for contracts of this nature?

* Yes, I know contracts of this kind are not necessarily the most reward-efficient thing to do, but I thought it would be fun and give me some good practice for a future Mun base project I have in mind.

[Rocket In My Pocket]

Personally I like to recon the part in question with a small/cheap probe/rover to see what exactly it is I'm working with.

It's really hard to design a retrieval system for something when you don't know exactly what the shape of it is.

Once you've seen the part in person, I'm sure it'll all start to come together in your mind, it always does for me at least.

[Fearless Son]

18 minutes ago, Rocket In My Pocket said:

Personally I like to recon the part in question with a small/cheap probe/rover to see what exactly it is I'm working with.

It's really hard to design a retrieval system for something when you don't know exactly what the shape of it is.

Once you've seen the part in person, I'm sure it'll all start to come together in your mind, it always does for me at least.

Well, I do have a scanning satellite in a polar orbit.  It has some fuel left, I should be able to put it into a low enough orbit that I can get control of the local Kerbal and use them to report on the state of their part.

[harrisjosh2711]

19 minutes ago, Rocket In My Pocket said:

Personally I like to recon the part in question with a small/cheap probe/rover to see what exactly it is I'm working with.

It's really hard to design a retrieval system for something when you don't know exactly what the shape of it is.

Once you've seen the part in person, I'm sure it'll all start to come together in your mind, it always does for me at least.

When in doubt. Build a Big F***** Rocket......

 

[Tyko]

If you're using KIS/KAS you might be able to have a Kerbal attach a docking port to the object, then dock with it and take it home. Alternatively there are the winch/harpoon/magnet parts in KAS - I've not played with those enough to give a strong recommendation, but might be worth exploring.

It''d be really cool if you could hover over it, harpoon it and sky crane it away - does this work?

[Fearless Son]

1 hour ago, Tyko said:

It''d be really cool if you could hover over it, harpoon it and sky crane it away - does this work?

It would be cool, but I play stock.  I enjoy a more "pure" experience because it generalizes more widely when I share it with other people (like on this forum.)

My current tentative plan is to have a big cargo lander that deploys a rover with an attachment arm which will drag the part into the cargo bay and lift off.

[Tyko]

2 hours ago, Fearless Son said:

It would be cool, but I play stock.  I enjoy a more "pure" experience because it generalizes more widely when I share it with other people (like on this forum.)

My current tentative plan is to have a big cargo lander that deploys a rover with an attachment arm which will drag the part into the cargo bay and lift off.

Please post how your plan works. I'm wondering if a rover's wheels would get enough traction in the low-gravity environment. best of luck!

[Fearless Son]

27 minutes ago, Tyko said:

Please post how your plan works. I'm wondering if a rover's wheels would get enough traction in the low-gravity environment. best of luck!

I thought of that.  I equipped the rover with upward-thrusting RCS nozzles and some monopropellant tanks to give it some down force and increase the effective friction on the tires.  It has a pair of medium landing gear on the arm-sided end of it which can be raised to get the part off of ground contact.  A large reaction wheel should provide enough torque to help the rover manage the center of mass offset grabbing the part might cause (it normally has its torque disabled to mitigate accidental flipping.) 

And all of it narrow enough to stuff in a Mk3 cargo bay (just barely.)  If it can fit that, it can fit a two-meter wide part.

Edited December 21, 2017 by Fearless Son

[OrbitalBuzzsaw]

I'd do a lander with a Klaw on the bottom. Should work.

[Kerbal7]

23 hours ago, Fearless Son said:

 

Cool Picture!

[Plusck]

I don't think you can ever get "kerbal plus part" recovery contracts for any part that isn't crewed, so that should narrow down the options. The dimensions given in the contract should be quite precise, so (assuming the OP was approximative) that probably means Mk1-2 pod or science module or hitchhiker can.

I've done a couple of part-recovery-from-surface contracts and swore I'd never do one again. I tend to end up with hugely complicated designs.

The worst thing is getting something that can reliably grab, but can also then lift off from the surface. That means either huge (so that the added recovered part... potentially over 3 tons... doesn't make the craft impossible to control) or balanced (so that the part goes in the middle. Just for kicks, I built this to show you what I would do. I know it's awful...

Spoiler

Two grabbing rovers to land and set on either side of the part. They then should be reasonably balanced for return to Mun orbit, where they return to the orbiting heatshield assembly. The rovers navigate to the orbiter, then the orbiter docks to them (let's call the side that gets docked "rover A"). Then both rovers disgorge fuel to the orbiter, the body of rover B gets dumped by manually disconnecting the docking port on the grabber, then the remaining recovered part (+roverA + rover B's grabber) separates from the orbiter again to turn around and redock via rover B's grabber base. The now-useless and unfuelled rover A + grabber is dumped, and the orbiter can ungrab and regrab the part to get it aligned with CoM, before heading back for home.

Horrendous and complicated, I know, but the Mun's gravity is just a touch too high to comfortably send a single hovering part-grabber down there, and any sky-crane-like device that can also drive around is going to be huge.

 

[Cpt Kerbalkrunch]

@Fearless Son; been insanely busy this week, so I haven't been able to post, but I saw your question earlier and haven't been able to get back to it 'til now. I've done the "pick-up module from surface" contract a couple of times; both on Minmus. This is the rocket I used.

 

 

The little rover below becomes the lander and makes the pickup. It has both horizontal and vertical probecores. The vertical was for launch, obviously, but I made it part of the rover for balance. The horizontal then becomes the control point for landing, take off, and return to Kerbin; at which point the engines and tanks are dumped. You can see the heatshield on the opposite end of the Klaw. Didn't really need the shield but, again, I needed to balance out the mass a bit on the return.

 

 

 

 

 

It just functions like a normal rover on the ground, with the rovemate and the Klaw as the control point. It actually worked really well. You have to jostle the module a bit to get a good surface connection, but it wasn't too difficult. To keep it from dragging the ground I just drove toward and slammed on the brakes to make the weight dive forward. This way you grab it low, and then it lifts up when the rover rocks back to normal. Then you just take off. If your part is heavier, you'll need a larger rover (not to mention the higher gravity on Mun), but the concept is the same.

I tried using the sky crane method, which I often use for dropping modules, but it wasn't working for me. I can land close enough to a module to knock the solar panels off, but vertical docking always ends in failure. I haven't tried it in a while, so I might be able to pull it off now, but this worked just fine. And it was kinda fun.

Edited December 22, 2017 by Cpt Kerbalkrunch

[Human Person]

I would send 2 rovers with grabbing units so you can attach them on opposite sides and launch the thing to a low mun orbit, where a 3rd craft grabs it that has a large heatshield and parachutes for recovery.

[Tibrogargan]

On 12/21/2017 at 11:57 AM, Fearless Son said:

It would be cool, but I play stock.  I enjoy a more "pure" experience because it generalizes more widely when I share it with other people (like on this forum.)

My current tentative plan is to have a big cargo lander that deploys a rover with an attachment arm which will drag the part into the cargo bay and lift off.

Not sure why playing stock disallows a skycrane harpoon (as long as by "harpoon" he means a grabbing unit).  Maybe I'm crazy, but I built my entire 5 or 6 section Mun mining base with a reusable skycrane that is pretty much 6 terriers in a hex shaped arrangement balanced around a coupler.  I use a docking port as my coupler, but no reason the port couldn't be replaced with a grabbing unit.  Would definitely be relatively easy to pick up something under a couple of tons and get it into orbit.

(I probably should have just built the crane with the AGU in the first place, it could have just refueled by landing on the base)

[Fearless Son]

19 hours ago, Tibrogargan said:

Not sure why playing stock disallows a skycrane harpoon (as long as by "harpoon" he means a grabbing unit). 

He was speaking in the context of the KAS mod.  A skycrane with the grabber unit is a good stock option though.

[Fearless Son]

Okay, so I completed this mission.  Here is how it went down.  

Getting this vessel into orbit was more like launching a shuttle than a rocket, except the shuttle used none of its own engines.  We needed a careful balance of thrust and mass due to the unavoidable asymmetry.  Thus, we employed a Mammoth and a Mainsail, side-by-side, with four Kickbacks and a couple of drop tanks.  I found that during ascent, the shifting flow of fuel would make control more difficult, unless I progressively reduced the thrust output of the Mammoth to the point that the SAS could compensate for it.  Fortunately this was not too difficult as I could generally make the adjustments between burns.  

There was an extra fuel tank inside the cargo bay.  Since that space would be needed later in the mission for the part we needed to recover, I figured it was a nice place to stick a drop tank we could burn off to make our Munar transfer.  Once we were on an impact course for the Mun, the empty tank was dropped, then the engines made a fine adjustment to put us into low Munar orbit, while the tank sailed on to be safely disposed of by high velocity impact with the regolith.  

While I had closed the cargo bay hatch after ejecting the drop tank, I was a little worried because by the time I got to Munar orbit the batteries were nearly drained.  It turned out that because I had adjusted the placement of the solar panels so they would fit more flush with the surface of the bay, their center of mass was technically inside the bay walls, and thus the panels were inoperable while the bay was closed.  Thus, the bay spent most of its time open.  In the picture above, the craft has been met at the Mun by a refueling drone because while I had planned for enough delta-v to get to the Mun and back again, I forgot to account for the fact that the place I needed to land had a big inclination adjustment and was getting nervous about fuel levels.  

I forgot to get a picture of the lander coming into land, but it has a set of four Twitch engines on each outboard pylon.  Not much thrust for this amount of mass, but good enough for the final descent into a belly landing.  The landing was successful, a few hundred meters from the target, and it was revealed that Lizke Kerman was there with her Hitchhiker Storage Container.  She planted a flag to mark the occasion of her rescue, and the rover undocked from the cargo bay and headed out to meet her.  

Fortunately, the rover easily grasped the Hitchhiker, and Lizke hopped into the passenger seat, ready to get out of here.  I was a little worried about the rover carrying all that, but it handled it easily.  Having that big reaction wheel under the seats (and set to SAS only) helped go a long way toward compensating for any center of mass issues brought on by oddly shaped cargo.  

The moment of truth was getting the rover back into the cargo bay and docked in place, and it worked perfectly.  Rolled right up the ramp. connected to its docking port, cargo container still snugly grabbed with the AGU.  Lizke went into our spacious passenger compartment, grateful to get some fresh snacks and a chance to strip out of her space suit and towel off for the first time in days.  Okay, time to get out of here.  Doing the pre-flight check, stowed cargo, check, crew strapped in, check, electrical systems, check, engine activation, check, fuel tanks... -uh oh.  

"This is Mun Recovery One, Kerbin, we have a problem..."

Turns out that even with my refueling, the craft no longer had enough fuel to make it back to Munar orbit.  It could only manage a hop, at best.  The earlier miscalculation was worse than we expected.  The craft would need to make an on-surface refueling, which is much more complicated than an orbital rendezvous refueling.  The engineering team at Kerbal Space Center flew into action, and slapped together a probe on wheels which could land itself, drive up to the lander, and refuel it from below.  It was promptly put in a launch vehicle and sent to the Mun.

The refueling drone had two tanks worth of rocket fuel to deliver, making the final stage of its descent on a quad of Puff monopropellant engines.  I have no idea how two of the tires got blown up while in flight (I certainly made sure they were intact at launch) but fortunately it was built with redundant tires in mind for just such a situation.  The two small ore tanks on top of it are simply ballast, intended to adjust the center of mass both for the sake of the launch vehicle and to make the landing controllable.  They can have their content jettisoned once it reaches the surface, but the extra weight helps add friction to the tires.  

Unfortunately, it turns out that the engineering team at KSC assembled this refueling drone a little too quickly.  It was not able to wedge its refueling port under the lander to meet the refueling port on its bottom.  The crew of the lander are now grumbling about shoddy government work and lack of standardization, wondering what they are expected to do with a set of badly needed fuel they cannot actually connect to.  Then one of them gets an idea: the rover they brought along is designed to dock with literally anything because they did not know exactly what they would have to recover.  The rover itself has no rocket fuel tanks, but it is designed to connect to the lander with an arbitrary object docked to its other end.  They spring into action!

They roll the Hitchhiker Storage Container back out of the lander and gently set it down out of the way.  Lizke Kerman volunteers to stand downhill beside it and make sure it does not go rolling away.  The rover rolls out to the refueling drone and neatly grabs it.  The turning radius is pretty wide with this docked setup, but it moves over the Munar surface more easily than the refueling drone alone did.  

Getting the drone into the cargo bay while attached to the rover was a challenge.  I had to let the AGU freely pivot so it could handle the change in incline of the ramp, but it made it in.  It hung out the back, but the rover was able to dock without losing its connection to the drone.  From there, it was just a matter of manually transferring the fuel into the lander.  Once the drone had fulfilled its mission, it was rolled back out, its brakes engaged, and its type changed to "debris" though I expect it to still remain technically "active" so long as it gets sunlight.  The rover connected back up to the Hitchhiker Storage Container and brought it back in again.  The whole crew sighed with relief: they can finally get out of here.

We had enough fuel now to aerobreak at Kerbin.  Sadly, it was not enough fuel to put us down right next to the KSC, but we were not exactly in a position to be picky.  The cupola module very nearly overheated during the first pass, to the point I evacuated the pilot to the crew module behind it in case it blew up, while the autopilot system (which was technically mounted in the docked rover so it could operate autonomously if necessary) kept it going.  I threw it into a spin to shed heat, which seemed like just enough to keep the cupola from exploding.  Future passes were done rear-end first, which was able to better handle the atmospheric compression.  It had just enough chutes to bring the whole thing just under 10 m/s when fully deployed.

Touchdown!  We have returned to Kerbin and are ready for recovery.  

Recovery contract complete.  That was actually pretty fun!

Edited December 25, 2017 by Fearless Son

[Atkara]

For me, it starts with the following lander:

It departs from it's assigned station in LKO, gets to either of Kerbin's moons and lands near the stranded pod (20-30m if I'm in a good day, 150-200 if not). Then I get it to hover, lock radial out once close, then use RCS to guide the claw above the pod. Once there, I cut throttle and capture. If the legs don't get to touch on the ground, the large reaction wheel will do it's best not to let it tip over.

Obviously, it doesn't have the fuel to get back to Kerbin. So, once it reaches orbit, the following ISRU equipped miner comes in:

The miner isn't there for surface recoveries. It's typically used to complete mining contracts and supply an orbital refinery with ore.

Anyway, once fueled up, the lander gets back to Kerbin, where the following type of spaceplane is waiting, shown below in station assembly configuration:

In debris recovery configuration, it has a grabbing unit attached inside the cargo bay. It also carries a maneuvering unit, also equipped with a grabbing unit, shown below in station assembly duty:

Once the lander and the spaceplane meet up in LKO, the maneuvering unit grabs the pod and secures it on the grabbing unit inside the MK3 cargo bay, which has been set as the spaceplane's control point. The lander departs to meet up with it's assigned station and the spaceplane lands at KSC:

For small pod recoveries, I use a MK2 spaceplane, but I won't bore you with more shots