Author Topic: Kerbal Space Program or "Rocket science is harder than it looks"  (Read 372742 times)

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Offline newman

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
I am having a huge amount of trouble trying to dock large craft (like the tugs that Newman's Eve lander used to get to Eve). Has anyone got any advice?

Actually, those tugs aren't even close to the largest stuff I dock to one another, and are fairly easy to dock. Without getting into discussions on whether mods are cheating or not (which basically depends on the mod, anyway), I will say that I don't use any mods in my craft designs and also don't use mechjeb, and I dock them just fine. While that laser mod might help, if you're having trouble docking mid-sized ships that suggests you're doing something wrong. While a mod might help you get around the things you're doing wrong, addressing those issues is always the better approach whether you end up using mods or not.

So let's get down to business. There are two major things that are important with docking; craft design and RCS maneuvering.

1) Craft design: half of your successful docking maneuver is done before you ever leave the ground, in the VAB (or SPH, depending on the craft). Efficient RCS setup is the key to controlling your ship efficiently once in orbit; those tugs of mine had a large monopropellant tank each, but that wasn't because they needed that much to dock to the Defiant (Eve lander) - 750 monopropellant is easily enough to handle a dozen dockings. It was rather because the Defiant was a pretty special case that needed to be able to keep it's nose straight up during the first few seconds of launch from Eve surface; in case it landed on a slope it needed lots of powerful RCS thrusters to quickly set it straight. This also meant that the Defiant was a fuel guzzler when it came to RCS fuel, hence the large tanks.

The tugs themselves were easy as dirt to dock. Neither of them used quad thrusters, and I would suggest not using them on craft that don't absolutely need quads for some reason - and those you'll just dock around in orbit don't. Use linear thrusters instead, and try to position them at equal distances from the center of mass. So basically, 4x symmetry side linear ports near the top and bottom on each side of the center of mass; these will provide sideways thrust. You'll also need to be able to thrust forwards and backwards, so put another 4 backwards oriented ones in the back, and 4 forward oriented ones in the nose. Give them a large RCS tank and with a little practice you can dock anything many times on a single large tank. Or save some weight and give them smaller tanks if you feel you won't need that much and are confident of your abilities. Either way, efficient RCS setup wins half the battle before it begins.

While on the subject, I'd also like to address the myth that RCS + ASAS is a bad combination. Indeed it can be, either on rather large ships, or on ships with a badly designed RCS setup. See, well placed RCS thrusters won't create much torque when you just want your ship to go sideways; if they do, ASAS will try to compensate by periodically firing thrusters on the other side to countermand the rotation produced by the pair you activated. Introduce some wobble and shaking of the ship and you got ASAS spraying your RCS fuel all over the place. But the solution to this problem isn't always to not use ASAS, but rather to make the ship not wobble / turn when you activate side thrusters. Design your RCS system well, and ASAS-induced RCS mess will be kept to a manageable minimum at worst, or won't be present at all at best.

2) RCS maneuvering.

This won't be that much of a problem if you've designed your RCS system properly. Remember to use the navball's information to your advantage. You have speed relative to target and vector relative to target, those two tools give you a lot to work with already, allowing you to kill relative velocity to your target by finding the retrogade icon on the navball (while in "target" mode), and burning prograde in it's direction. Melt your speed difference to your target to 0.0 and you'll seem to stop (again, relative to target) - it's a good idea to do this some 100m or so away from your target. Then take a moment to plan the final docking approach - select the docking port on your target you want to dock with, right click it and set it as target. This can be helpful with your navball, as your target indicators now point to that docking port and not the target's command module. Now take your time, and slowly position yourself so your nose is oriented and lined up to that docking port. Slow and steady wins the race here - go too fast and you'll spend up twice as much time lining up as you would have if you were patient. Use different camera views to line up your craft as best you can. Once done, lock your orientation with ASAS, give yourself a bit of forward motion towards the target (0.1 or 0.2 m/s is fine at this point) - this is just so your prograde vector appears in front of you. Now you can use the side thrusters to line up your nose with the pink target indicator on the navball (the pink target with a circle). If you have your nose, the pink target, and the yellow prograde icon all at the same place on the navball, it means your nose is heading straight for the docking port. This is good, assuming the docking port is actually in your nose - if not, adapt the method to the side of the craft the docking port is at :)

Whew, a lot of text. Hope that helped some.
You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here! - Jayne Cobb

 

Offline MarkN

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
No decoupler on the SSTO, the component below the capsule is the ASAS. the parachute is a drogue to make it easier to stay pointing up in the early stages of deceleration. The ship lands on it's tail using it's jet engines. I have been trying to make larger SSTOs (mainly to have some fuel in orbit to allow for docking), but the SAS stops being able to cope with the aerodynamic forces on the vehicle as it accelerates crabwise (pointing around 35 degrees from horizontal, but traveling only 10 degrees from horizontal). I think the ideal SSTO would be nearly symmetric vertically, so that the air resistance below the centre of mass equalled the air resistance above it, but have not managed to get a design like that to work.

Looking at my design, the problem is likely to mostly be RCS positioning. I was using a lot of monopropellant for simple changes of orientation, and almost any manoeuvre was leading to the rocket rolling 

 

Offline Nuke

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Re: Kerbal Space Program or "Rocket science is harder than it looks"


been working on my parts back. it now has about 32 parts. im going to try to release it in a few days.
I can no longer sit back and allow communist infiltration, communist indoctrination, communist subversion, and the international communist conspiracy to sap and impurify all of our precious bodily fluids.

Nuke's Scripting SVN

 
Re: Kerbal Space Program or "Rocket science is harder than it looks"
After de-orbiting a lander pod that had been floating about for a while, I realized that even if I manage to land or splashdown really close to the KSC, there's no way for the Kerbals to actually get back to the center besides walking/swimming. So I spent a few days building a truck and a few boats.
The truck was easy and boring, but the boat went through many different versions before I found a design that floated and stayed intact and stable at high speeds (because going anywhere slow is not the Kerbal way!).

Behold! The Kerbal Aquatic Retrieval Transport (KART):


It seats a single pilot, has room for three more Kerbals in the hitchhiker pod, and most importantly, has a cruising speed of about 160m/s on calm seas, or 173m/s if you push the throttle as far as it goes. And of course plenty of fuel for long-distance travel, and many trips.

And then, just for kicks, I made a speedboat, designed only for speed:


Strangely, it only gets up to about 180m/s. Additional designing will certainly yield better results. I may have to resort to aerospike rockets.

The boat in between these two is a refueling boat with a docking arm at just about the perfect height to match up with the water-truck's rear refueling port. Strangely, when I tried to dock on the high seas, and again on dry land, the two wouldn't dock. Is that something that can only happen in space?

 

Offline newman

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
The boat in between these two is a refueling boat with a docking arm at just about the perfect height to match up with the water-truck's rear refueling port. Strangely, when I tried to dock on the high seas, and again on dry land, the two wouldn't dock. Is that something that can only happen in space?

No, I managed to dock stuff on surfaces of planets, though admittedly only on dry land. It should work when afloat too, are you sure you're using compatible docking ports? A small docking port can only dock to another small docking port, for example..
You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here! - Jayne Cobb

 
Re: Kerbal Space Program or "Rocket science is harder than it looks"
No, I managed to dock stuff on surfaces of planets, though admittedly only on dry land. It should work when afloat too, are you sure you're using compatible docking ports? A small docking port can only dock to another small docking port, for example..
The first test was regular size clamp to a jr on the sea, but the second test was jr to jr on land. I'll give it another shot, thanks.

 

Offline newman

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
I've done jr to jr on land and it worked just fine on my end.. In fact, that's how I refuel my mobile ramp tower so I can move it around.
You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here! - Jayne Cobb

 
Re: Kerbal Space Program or "Rocket science is harder than it looks"
Hmmm, OK. Just how close do you have to hit a docking clamp? I was dead-on laterally, but maybe 1/3 of a clamp-o-tron jr higher than the target and all I could do was push the other ship. And is there any special way to dock, or just to mash one clamp into the other?

 

Offline Ace

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
I tweaked the nine nuclear engine design to be a bit more fuel and tonnage efficient and decided to do landings on the two major objects in the system I haven't been to yet:
Dres and Eelo!

Next is a manned mission to the inner most planet (only did an orbiter, no touch down yet), and then the rover invasion...

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Ace
Self-plagiarism is style.
-Alfred Hitchcock

 

Offline Nuke

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
i just released my mod. part count is up to 32 download here. will put this on the space port as soon as i figure out how.

http://kerbalspaceport.com/half-meter-parts-and-other-useless-crap-r3/


going to jool, be back in a few years.
« Last Edit: February 05, 2013, 04:45:00 pm by Nuke »
I can no longer sit back and allow communist infiltration, communist indoctrination, communist subversion, and the international communist conspiracy to sap and impurify all of our precious bodily fluids.

Nuke's Scripting SVN

 

Offline Ace

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Although my nuclear puller design has been pretty good for sending single landers throughout the system, I decided to try to finalize some real spaceship construction.

The Discovery II.

Currently docked with 8 probes, and it can fit 4 landing craft and 1 resupply vessel.

Only non-stock parts are the central centrifuge.



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Ace
Self-plagiarism is style.
-Alfred Hitchcock

 

Offline Enzo03

  • 27
Re: Kerbal Space Program or "Rocket science is harder than it looks"
Guess what game made it into PC Gamer's Sim-plicity feature this week?
Quote
Having retired from world-saving heroics, Christopher Livingston is living the simple life in video games by playing a series of down-to-earth simulations, though this week is less down-to-earth and more up-to-space as he attempts to create his own space program and learns that what goes up, might not come down. Ever.
:lol:
21:20:19   SpardaSon21: "hey baby, want to get a good look at my AC/20?
21:20:26   Spoon: I'd hit it like the fist of steiner

Some people are like Slinkies.  They aren't really good or even useful for anything but they always manage to put a little smile on your face when you give them enough of a push down the stairs.

 
Re: Kerbal Space Program or "Rocket science is harder than it looks"
I started using the Kethane mod on a new save.  I surveyed Kerbin, the Mun, and Minmus, before plopping a drilling platform down on a deposit on Minmus.

What's missing is the refinery.  The idea is that the drilling platform can return to orbit, where it will meet up with the refinery and offload its moon flatulence Kethane to be converted into whatever passing vessels may require.

Sadly, I seem to have made my refinery, not out of empty tanks and Kethane converters, but out of singularities.  The space-tug with which I've been moving everything between low-Kerbin orbit out to the moons is completely incapable of moving the refinery.  Docked to the empty refinery, the tug burned about a quarter of its fuel for a total delta-V of 0.0m/s.  Yeah....  I'm hoping that all I need is a bigger, thrustier (teehee!) space-tug

 

Offline pecenipicek

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
you didnt use the tiny gravity engines that kethane has, did you?
Skype: vrganjko
Ho, ho, ho, to the bottle I go
to heal my heart and drown my woe!
Rain may fall and wind may blow,
and many miles be still to go,
but under a tall tree I will lie!

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Offline Nuke

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
i find it was just easier to put a kethane converter and drill on every single landing capable ship that i built. you can pretty much planet hop through the system without additional fuel from kerbin. just save eve for last.

one thing i dont get was how it was possible to produce monopropellant (real world analog: hydrazine n2h4), oxidizer (lox/h2o2), liquid fuel (lh2/karosene), and xenon (do i need to say it), out of kethane (real world analog, ch ****ing 4). is this thing a damn fusion reactor with no net energy gain? is the periodic table not universal?
I can no longer sit back and allow communist infiltration, communist indoctrination, communist subversion, and the international communist conspiracy to sap and impurify all of our precious bodily fluids.

Nuke's Scripting SVN

 

Offline newman

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
one thing i dont get was how it was possible to produce monopropellant (real world analog: hydrazine n2h4), oxidizer (lox/h2o2), liquid fuel (lh2/karosene), and xenon (do i need to say it), out of kethane (real world analog, ch ****ing 4). is this thing a damn fusion reactor with no net energy gain? is the periodic table not universal?

Good questions, though I doubt the makers of the kethane mod bothered with them too much. Hopefully the official features doing the same thing will be better thought out.
You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here! - Jayne Cobb

 

Offline Ace

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
After getting the Discovery II all prepped I decided to build an automated rover that could dock with it and be deployed onto planets along with landers and its current probes.

It was easier to outright send the test rover to Duna than to bother with docking it first, so here's the first Rover!

The next step is the robotic invasion of just about every planetary body using the Discovery class ships, followed by building stations around each body.

Edit- My first Eve rover attempt successfully landed on dry land... and then flipped over after I put the parking breaks on when it was rolling down a hill.

RIP Eve Rover 1.

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« Last Edit: February 17, 2013, 02:49:38 am by Ace »
Ace
Self-plagiarism is style.
-Alfred Hitchcock

 

Offline Ace

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Operation Eve rover is now a success.

That's after the first landing where the rover flipped on its back after rolling down a crater and the second landing where the atmospheric drag brought its landing trajectory into the ocean instead of the coast.

The only hitch with this mission was that the solar panels blew off when they were deployed after landing, but it has a backup RTG for power.

[attachment deleted by a basterd]
Ace
Self-plagiarism is style.
-Alfred Hitchcock

 

Offline newman

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Eve surface can be pretty glitchy. Stuff that seems ok on landing will sometimes lurch into the air / tip over / fall part on load. Deployable solar panels are particularly susceptible. The only way to put a probe there you can safely reload is to do a floating one and deploy it in one of the oceans.
You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here! - Jayne Cobb

 

Offline Dragon

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
I stopped messing with interplanetary stuff for a while and focused on historical missions and modding:

The N1 in all it's glory...

And the payload.