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Recovering landed stages


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Hi everyone,

in an effort to cut launch costs (which crippled one of my earlier career games), I discovered I could cut Kerbin to orbit costs with mods like Stage Recovery, which allowed me to get refunds for some of my spent stages (For those who don't know, it calculates the landing zone and survival chances of decoupled stages once they leave physics range and refunds you based on landing location and predicted speed). 

Long story short, I started making entirely SSTO Rocket lifters, that I would then pilot back from LKO to KSC, however, either piloted by me, or by MechJeb landing and even with 4-500 m/s unspent deltaV I usually miss KSC by 20/60km. 

Sure, I'd still get 90% back or so, but still, when your rocket costs skyrocket because it has to be entirely returnable why accept less than perfect refund?

So I started building crawlers to go fetch the landed rocket, grab it with a Klaw and haul it back. (I used Konstruction for the large tank threads and Infernal Robotics for a few other things). 

This sort of works as I can have MechJeb do the boring waypoint piloting to the rocket and then drive it back to the landing pad . 

I had initially tried with grabbing the top half of the rocket and lowering it onto a flatbed of sorts with infernal robotics parts, however, they start bending uncontrollably and no level of parallelism or struts seems to help. 

So I'm stuck with carrying the rockets vertical over terrain, which forces my crawler to weigh at least twice the rocket to be relatively stable. 

So, I'm wondering, is there a way? should I be using IR differently? should I refuel the rockets and have them haul their big mass back to ksc on their own? I also considered sky cranes but I couldn't build one that reliably balanced and lifted 50 tons off the ground. Should I redesign everything and use FMRS so that my stages get flown back independently?

I'll post a couple of pictures of my 6Ton Lifter, 15 Ton Lifter and 30 Ton lifter and the crude crawler I got so far. 

Primitive Crawler: https://drive.google.com/file/d/0B0DB1_F3t7P7am10OFBPRTk2amc/view?usp=sharing (had stability problem and could have failing tracks due to load)

Primitive Crawler with 6Ton Lifter : https://drive.google.com/file/d/0B0DB1_F3t7P7RG51bFJneVdTOG8/view?usp=sharing

Better Crawler (I apologise for the lighting will take a better shot of it later): https://drive.google.com/file/d/0B0DB1_F3t7P7RS0tV1lOMFJINmc/view?usp=sharing

50 Ton Lifter back on the pad with the smaller crawler: https://drive.google.com/file/d/0B0DB1_F3t7P7Y2tPdlJBWWwtN1k/view?usp=sharing

 

So I guess the question can be shrunk to: How can I manipulate a 50 Ton object on Kerbin's surface with IR or other mods without twisting blowing up everything?

 

On a related note I am struggling to make an articulated docking port for an aerobraking tanker (With the 10Meter Shield to go around) so far I have to quicksave/load to stop the wobbles after docking. Oops can't find a picture of it right now. But basically it is a right angled IR robotic arm that extends out and forwards clearing the 10M heatshield.

 

Thanks in advance for any suggestion or comments 

 

 

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You've got IR working? I haven't managed to get IR working in 1.3+!?!?

In answer to your question...I don't have an answer. However there is a nifty little mod called Trajectories that really helped me with returning spacecraft accurately to the KSC:

It gets my rocket back to the KSC pretty much bang on everytime, and it's also useful for aerobraking.

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I run most of my mods from CKAN, however the version listed for my ksp version didn't work, but I found help on their github page, basically you download from there, remove a few files and you're good to go. 

Thanks for the tip on Trajectories, I do undestand that MechJeb landing can only go so far as it probably doesn't take the actual profile drag into account (It always lands short at 20Km if normally fueled, 60 if short of power or fuel during the descent).

I do understand the issue with IR is in the game engine and Unity but still the failure to handle loads reliably is a big downer, I might be giving the Konstruction hooks and winches a try ti see if they are less bendy.

Another Idea I have had is to drive a refueling rover to them but it feels cheaty.

Does anyone know of ways to strenghten or distribute load on IR equipment? (Always looking to grab and tilt the rocket onto a flat carrier.

 

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My suggestion would be to build your rockets cheap and not recover them at all since funds shouldn't be an issue on default difficulty settings but to each his own, you seem to find this way of playing fun.

Only piece of advice I can give you is upside down jet engines in the Rover (facing up towards the sky), will push COM down below the ground. You don't turn them on, just having them there is enough, the COM on the jet engine model is well ahead of the actual physical model to represent the piping and such that isn't shown. Placing enough in your rover will force it's COM down, even below the ground making it extremely stable and sturdy.

Best of luck.

Edited by Rocket In My Pocket
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I love reusable rockets! I normally have an ssto lifter and then I'll strap some solids on if I have to get that extra delta v. Then I'll leave the first stage in orbit until I rendezvous or finish my primary mission. Then I'll pilot the first stage down and I can normally land on the KSC peninsula, but sometimes I land in the desert. I do recommend trajectories, and other than that, just practice a whole bunch.

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Thanks for the Jet engine advice, I will try it out for sure :) 

Yes I can usually manage peninsula landings, but the odd highland landing gets tricky for vertical rocket carrying.

I even tried the grid fins but they only seem to work as airbrakes strangely enough.

I will also try the wings idea, maybe deployable wing might do the trick in gliding and not overrunning KSC.

Yes I know that I could build cheaper staged rockets, but I always found them temperamental compared to Monolithic lifters, the costs wouldn't be prohibitive per se on a mission based approach, but I often get carried away, I surely have contracts running for a Million credits under way, but then I hear of fuel depots around minmus and so a mining operation is born, Mining bases are landed, stations delivered in chunks to Minmus orbit, Fuel Shuttles from MinMus base to Orbital Depot are conceived and tested , aerobraking tankers with retractable docking ports for the odd refuel in LKO are tested, scrapped due to krakens, improved and a million spent credits later that probe to Duna is still waiting for it's launch window while funds ebb away.

For example since antenna range has become part of the gameplay I started building relay networks along major planets and stuff, it's costly and if I can limit launch cost to the fuel and the payload I find I can roleplay fun/tedious parts like vehicle recovery, aerobraking and refueling those three years before a launch are never empty if sometimes time consuming. 

I get carried away by side projects while waiting for launch windows and so I end up spending a lot doing infrastructure (I do the same in Minecraft btw). 

This is the orbital station in minmus orbit (Still lacking the fuel storage facilities which will fit top at the end of a modular truss network) for example (With a Fuel Shuttle and fuel station componet tugs attached):  https://drive.google.com/file/d/0B0DB1_F3t7P7R1dJRTMxNm1WQ1k/view?usp=sharing

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I personally use Trajectories and FMRS to land my 1st stages. I also use Kerbal Reusability Expansion for legs and grid fins. When doing a landing Space X style, as in without wings, you want to make sure that Trajectories is set to retrograde, otherwise it might display incorrectly. I also intentionally don't make orbit with my first stages so that my return velocity isn't so high.

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I am using the reusability expansion as the larger falcon style legs look great (and make for solid stable landings even on hills and minmus ). I look forward to trying FMRS because I'd be happy to be manuevering lighter stages and enjoy the challenge of multiple reentries. Yes the retrograde thing does seem fundamental. Weird it's not included in the MechJeb landing computer. (I wouldn't like you to think I only rely on MechJeb, but sometimes, it feels just right to have a landing taken care of the computer while I go off to get tea, or if I've grown annoyed with a buggy manuever node.

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I do powered landings, so I definitely have left over fuel after reaching apoapse. I use trial as error to figure out how much I need and I prefer to have a dedicated tank for the return and landing burns so that I can lock them and don't have to pay attention to my fuel while climbing through the atmosphere. I also tend to be in space when I detach my payload/second stage. 

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Oh I see, so you basically drop backwards into KSC, I see, yes, it makes sense to lock tanks. Once I forgot to lock tanks on a docking port attached satellite booster for twin commsats to Eve, and it drained half the fuel on the booster during ascent, bad thing was I only realized this after the ejection burn to Eve... :( when I only had a few m/s left. Luckily I had excess fuel in the Xenon tanks on the actual sats and they were able to make injection and orbit burns on their own with a little to spare.  

It still sucked as I was hoping to leave the booster and what was left in a long orbit around eve with the spare fuel if a future mission needed it.

A pair of unsupecting commsats on the trek to Eve: https://drive.google.com/file/d/0B0DB1_F3t7P7YjkyY0FSWGV5Mzg/view?usp=sharing

Edited by morganchane
typos
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8 minutes ago, morganchane said:

Very Interesting, fixed wings or deployed? By the way, KSP would 100X tougher with realistic reaction wheels, all hail spinning weights!

Just fixed wings on the top, like New Glenn, but just alot bigger, compared to its size.

Blue_Origin_New_Glenn_2016-Sep_Introduct

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21 minutes ago, morganchane said:

That looks fantastic!!! :) Will try it out tonight!

Okay! Maybe i could post a screenshot. Im pretty sure you can ajust your trajectory good enough that you can land everywhere in a 50km+ range from orbit. From a pretty steep suborbital flight i moved 5-15km. 

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Not at all :) 

Yes the thread deviated a bit from the original request, but the insights into returnable stage design will be very useful into making Cheaper and more cheerful rockets, and Robotized Stage Recovery easier. I will probably ask about the IR / Konstruction tips in a separate thread for more specific advice against bending and ghost forces in Robot design :)

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  • 3 weeks later...

I didnt bother to read the rest of the responses due to a time constraint, but I felt like giving my 10 cents anyway. My first thought was a Vtol Drone with the Klaw in the center that lifts the rocket from the top then flys it back to the KSC using jet engines. Do with it what you will, I guess.

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Hi, 

I finally managed to get back with some results. 

I haven't yet perfected a New Glenn Style launch (I currently have trouble with reversing course on the first stage). But I have taken up and experimented with Trajectories mod and have to say it's nothing short of fantastic. (Apart from the occasional game crash upon clicking on prograde - retrograde but I run a very heavily modded game so I take crashes into account with frequent saves during manuevers).

I have moved from MechJeb landing in the 20-50 Km range west of KSC to consistently within 10 Km, often better still. 

I have also found out that unbalanced RCS (i.e at the top of the rocket rather than on CG) works wonders for reentry attitude control, winglets would probably be better still but I need more time to test. 

 

Regarding the recovery aspect, I have experimented some more, and for smaller stuff, PAL Konstruction cranes do the job nicely (Read, command pods, but those are cheap anyhow), but they are a bit light on the pull for 50 Ton rockets. 

I have experimented with Heli quads with a Klaw but find that I cannot mate them reliably without crashing or toppling the landed stages (Perhaps that could work if I landed the stages sideways but their cg on liftoff would be a nightmare.

I also tried Kerballoons, turning a few on after landing so that the rockets just glides on the surface and have a single electric prop pull it off to KSC, but it takes ages and feels cheaty. 

 

I stil hope someday the problems of Infernal Robotics with Klaws and Docking Ports get solved it would be so much easier (Even for orbital operations).

 

I am also trying to redesign towards smaller boosters with first stage SRBs recovered with Stage Recovery, but they only shave a little weight off given if your are lifting 30Ton out of the atmosphere skippers just won't cut it and soon your mainsail kerbodyne assembly weight around 70-120 Tons again. 

I'll post a few pics of a much happier me (invisibile in picture) thanks to trajectories mod and your suggestions.

A happy Kerbal close to home; https://drive.google.com/file/d/0B0DB1_F3t7P7SEppaV9qeFNLRlk/view?usp=sharing

The smaller components Konstruction Rover + Crane : https://drive.google.com/file/d/0B0DB1_F3t7P7WTBNLTBKMzZXZTA/view?usp=sharing

The last one in a line of improving reentry targeting skills: https://drive.google.com/file/d/1MI2rHIMmrDD4hJoD-OrTPbFekvV6GkRN/view?usp=sharing

 

Still looking for deployable wheels and wings but I guess those must be unfeasible in the game engine.

(The other thing I'm looking for is a multisize docking port as making tugs for stuff with standard and senior docking ports is a pain, especially when you notice your mistake after rendezvous (rarely, luckily))

 

PS. I have noticed that in my game, on Kerbin, MechJeb landing predictions and projected lines are off by a couple kilometres even on vertical drops, for exaple if i ask for  KSP launchpad it projects a line off in the ocean 6-10 km out, I am not running planetary mods (except for graphics stuff), and it doesn't appear to happen on Mun or MinMus where it can generally make pinpoiht landings and follows the red line it draws. Any cue? Should I post it to their github issues?

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Have you tried using quantum struts to stabilise the parts after docking with the IR arm?

I tend to have a bunch and turn them on when required.

I also use them to hold robotic parts still when I’m not using them, it is important to remember to turn them off before you move the part though or the arm will tear itself apart.

They only effect the vessel they are on so can be great when you dock as they will automatically grab or detach to make everything rigid.

 

Deployable wheels and wings do work with IR, but due to the amount of stress on them they need to be strutted or they will just get ripped off.  Obviously normal struts are no good but either robotic struts or quantum struts work well.

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Not sure about infernal robotics, but you mentioned trying to build a skycrane. Perhaps one of these could work for your purposes?

https://kerbalx.com/letmeparkthatforyou/Kermansky-K-1200-Sky-Krane

https://kerbalx.com/EpicSpaceTroll139/E-24A-Champion (might need to add a claw to this one)

It might take some testing to find where the COM of your booster is and thus the best place to attach it by, but these rotary wing craft should be able to haul a booster back to the KSC faster than any crawler. (You did say it was ~ 50 tons right? Both should be able to haul twice that, but lighter = faster & easier to maneuver)

Edit: I might add a version of my bird with a claw already equipped since it might be hard to find the right place to put it.

Edited by EpicSpaceTroll139
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