Big Mun Payload, Halp?

[Tripod27]

I'm getting a mining truck to the Mun, the truck itself is pretty big and my plan for insertion is to hover it's skycrane a few meters above the Mun, and eject the truck. This has the truck land face first on some supports that also make it angle and land on it's wheels afterwards while the skycrane with engines still on flies away without interfering too much (sometimes the engine exhaust pushes you around a tiny bit)

Now, my question is, how much thrust to weight do I need on the Mun, and how much fuel, while keeping the overall design still light enough to get there?

Currently the landing stage is about 24 tons. The truck itself is just over 12 tons. Is this too heavy to get into orbit?

The lander has four LV 909s and a large tank of fuel for each, for a T/W of 3.41 on the Mun and a full throttle time of 5 minutes. Should I swap out for four T-45s? (which are enough to land me on Kerbin if I wanted ) Would make it a bit "safer" having a T/W ratio of over 12 and gives me over a full minute of full throttle time. If the small engines are enough, should I take off some fuel to save weight?

Most important thing is still just getting it to the Mun, I generally have a lot of trouble getting large payloads up into orbit and when I do manage it, it's after using some of the transfer or lander stage for orbit, making the rest of the mission impossible. so, is this too heavy? if it's not, what rocket layout would you suggest?

The next truck I'm getting up there weighs almost twice as much, at that point would I require orbital refueling? (I don't have a station up or anything so far besides a few satellites for the remotetech mod to keep my scanner probe scanning)

Edited June 3, 2013 by Tripod27

[stupid_chris]

Alright, we'll take this point by point.

Landing on the Mun from low orbit is about 1000m/s, so if you don't plan taking off again, 1100m/s is more than enough. So you can easily half your fuel here.

Then, having a very high TWR isn't always good with skycrane as it makes the throttle very sensitive. He has emotions and he doesn't want you to mess with it. So when you just want it to hover lightly, it might just go "What?? You want to go back in orbit? WHAT ABOUT I SET US BACK ON AN IMPACT TRAJECTORY WITH KERBIN?" So yeah, a TWR of 3 Sounds good. Which also means, if you're gonna cut down the fuel by two, you're gonna up your TWR by two. So you might also want to cut your engines by two. This means, your design but with only one pair of engines here should be sufficient.

For the lifter now, 24 tons is a really low payload. If you have trouble sending this into orbit, I can recommend watching some tutorials on asparagus staging and how to make heavy lifters. If you make a transfer stage for this, you should have to send about 40 tons in orbit or so, and this can be done quite well with stock parts.

And for your next truck, if you design you launcher and transfer stage correctly, there is no need of a refueling station.

Observations I made: One tank of RCS should be plenty for a trip to the moon, especially if you have no docking to do. Also, an ASAS module on a rover isn't always healthy. I recommand putting the ASAS on the lander stage, and instead adding a normal SAS module to your rover, this will help it stay on its wheels a lot more. Lastly, I hope you're sure of what you're doing by dropping your rover like this!

Lastly, I offer my services to make your launcher. I could have it done in an hour if you send me the craft file. Just proposing though, I understand that you would like to design it yourself, but I'm good at heavy launchers and I like to help out.

Anyway, good luck! ^^

Edited June 2, 2013 by stupid_chris

[Tripod27]

Alright, we'll take this point by point.

Landing on the Mun from low orbit is about 1000m/s, so if you don't plan taking off again, 1100m/s is more than enough. So you can easily half your fuel here.

Then, having a very high TWR isn't always good with skycrane as it makes the throttle very sensitive. He has emotions and he doesn't want you to mess with it. So when you just want it to hover lightly, it might just go "What?? You want to go back in orbit? WHAT ABOUT I SET US BACK ON AN IMPACT TRAJECTORY WITH KERBIN?" So yeah, a TWR of 3 Sounds good. Which also means, if you're gonna cut down the fuel by two, you're gonna up your TWR by two. So you might also want to cut your engines by two. This means, your design but with only one pair of engines here should be sufficient.

For the lifter now, 24 tons is a really low payload. If you have trouble sending this into orbit, I can recommend watching some tutorials on asparagus staging and how to make heavy lifters. If you make a transfer stage for this, you should have to send about 40 tons in orbit or so, and this can be done quite well with stock parts.

And for your next truck, if you design you launcher and transfer stage correctly, there is no need of a refueling station.

Observations I made: One tank of RCS should be plenty for a trip to the moon, especially if you have no docking to do. Also, an ASAS module on a rover isn't always healthy. I recommand putting the ASAS on the lander stage, and instead adding a normal SAS module to your rover, this will help it stay on its wheels a lot more. Lastly, I hope you're sure of what you're doing by dropping your rover like this!

Lastly, I offer my services to make your launcher. I could have it done in an hour if you send me the craft file. Just proposing though, I understand that you would like to design it yourself, but I'm good at heavy launchers and I like to help out.

Anyway, good luck! ^^

Thanks, I already made one rocket for it, which does okay (I can use some fuel from the lander stage to get to the mun) but after I added one more pair of boosters on one of the asparagus stages to compensate for some extra fuel I put in the second last stage, the pair kept falling off. It was mounted just like the other two pairs, but my FPS was low due to all the parts. Is this causing the physics to cut down in complexity and forget that those last two parts were mounted?

Here's how it looks and the craft file (just take off the parts you don't want) BTW the truck was made in the spaceplane hangar and copy/pasted to the VAB manually, so it still wants to go back to the SPH when you click return to build menu

http://dl.dropboxusercontent.com/u/42951400/Mun Ferry 1.craft

If you replace the very top fuel tank before the lander with one half the size, and remove two of the boosters (and move the other 8 a bit further apart) you'll get the rocket I almost got into orbit. I was one second of boost away when the real orbit stage ran out, so I decoupled, switched to the lander stage, fired up the engines and crashed into the stage I just decoupled because I forgot the engines were on backwards

The first two rockets in the asparagus stage aren't actually used correctly anymore, because after I added the boosters, they wouldn't finish until just before the second asparagus stage was done, so I just kept the engines on (only affected the TWR for that stage by 0.01) until the second stage and then ejected both

As for the rover ASAS, I actually have no trouble keeping the rover stable. It's just there to extend the docking port a bit. You can try the truck out if you want, it's pretty good besides the front crash guard, where I accidentally used a small box support without checking it's impact resistance and attached a light and a small box support to guard the bottom from crashes. the small square does fine, but the small box only has an impact resistance of 7 instead of the 80 I thought it had, so if you hit something frontally it usually blows up and takes your bottom guard and light with it :/

Edited June 2, 2013 by Tripod27

[kahlzun]

That download link isn't working. Also, you've built a massive rocket there!

[stupid_chris]

Indeed, massive rocket, but I think I get why you have trouble getting into orbit! Your TWR is very low, you loose a lot of delta V fighting gravity.

And indeed, the link isn't working. Can you give me a download link for your rover in the SPH? I would like to try something

[Tripod27]

Fixed the link, I copied the name manually and forgot the space between the 1 and the word before it (it also had the kethane mod on it, you'll need that to load it. I removed the kerbal engineer part because it's not needed for anything but rocket data). I actually got the truck to the Mun in the meantime, using the lander to get to the mun, get in orbit, shrink the orbit down to about 30km, and then slowly get my speed down from there with still a bit of fuel to spare. that thing really is overloaded with fuel >_>. And that was with me just leaving the two boosters that fell off on load on the ground and leaving without them.

Still, the other truck is heavier, but also comes preloaded with some fuel and RCS (they're supposed to be empty until it converts the stuff I mine into fuel and RCS) so you can at least use the fuel it has onboard instead of it being total dead weight. The link for that one is here (that one needs the KAS mod though, since I use the cable to connect the truck to a ship that flies back to orbit) nevermind I just reuploaded without the two tiny KAS parts

http://dl.dropboxusercontent.com/u/42951400/Converter Truck.craft

btw thanks for the help guys, been having trouble with heavy lifting for a while:(

Edited June 2, 2013 by Tripod27

[stupid_chris]

Alright, I'll take a look.

Also, you could edit your quicksave file to remove the fuel if you want to. Or even modify the cfg file of the tanks to create empty tanks to stick on your rover. But you can keep it like this, it's doable ^^

Edit: Don't worry, I can take any mod you can throw at me, I have all the biggest mods on my KSP!

However, the earlier link still doesnt work :l

Edited June 2, 2013 by stupid_chris

[Tripod27]

Alright, I'll take a look.

However, the earlier link still doesnt work :l

Wat

Please don't tell me I actually have to add in capitals to the link...

ok, copy/pasted the name straight from the dropbox folder, this better work

[stupid_chris]

Alright, I have something for you.

I made you an example heavy lifter for your second rover ^^

Really it's usually that simple. This can get you into orbit, then the core stage has a probe core, meaning you can deorbit it. There'S a tug with enough Delta V to set you on a circular orbit around the moon and still have plenty to deorbit too, because it has too a probe core. And the landing stage can set you down nice and soft, using mostly the fuel in the rover, because why not. Sorry it was long, I had to go out and stuff.

Now for the launcher, I already set the action group 0 to cut off the gimbal on the outer engines, don't forget to do that before launching. Also, right before launch, right click the top dockinport and do control from here, else the controls will be inverted and everything goes wrong. It has 270 parts, but you should be good once you drop the two first stage of asparagus boosters.

I tested it, everything works, and for your rover, it's a tad bit easy to tip over. So be very very careful on the Mun. I recommand disabling the motor and the steering on the rear wheels, else every time you try to accelerate you're gonna tip on your back. And be careful while turning too, I got it to tip over and never found a way to put it back up. And Don't use the break button, you're gonna tip on your nose. The best way to break is to reactivate the rear motors but deactivate the front ones and go backwards. Action groups would be useful.

Anyway, you can either take this or take it as an example and build it yourself! Anyway have fun!

Download link

PS: It's the "II" version because the first one I did was too powerful

Edited June 2, 2013 by stupid_chris

[stupid_chris]

I also took the time to revisit your other rover.

I made a rather simple launcher for it, and lighter lander/skycrane for it, while trying to keep your first design. I also added a transfer stage. Simpler designs are more often the most effective ones. This can get the transfer stage and the rover into orbit without touching their fuel, and still have plenty to deorbit. Because no one likes floating debris

I'll give you a download link so you can look at my design and take it apart. That's how I learned, by looking at other people's designs and by taking them down piece by piece to see how they work. It's much more educative than instructions in my opinion.

If you ever need help with anything, send me a message or anything and I'll be glad to help! You can also just drop a request on the Stupid Industries thread here and I'll do my best to help you!

Download link

Good luck! ^^

[gilflo]

With 6 asparagus big Rocketry tanks around 1 big rocketry, all seven with the most powerfull Griffon engine and those 6 Big Rocketry maintank surrounded by 12 asparagus (4 by 4) stock mainsail, each with the most powerful stock engine you can send up tu 200T in orbit around mun.

The asparagus stages are the 12 stock mainsails, followed by the 6 Rocketry.

Those can send a full equipped core station attached to the biggest Rocketry tank with 6 radial tanks and engines, 4 of them will be used for orbital manoeuvers and the last 2 will stay with the full main tank and the core station full equipped.

[stupid_chris]

With 6 asparagus big Rocketry tanks around 1 big rocketry, all seven with the most powerfull Griffon engine and those 6 Big Rocketry maintank surrounded by 12 asparagus (4 by 4) stock mainsail, each with the most powerful stock engine you can send up tu 200T in orbit around mun.

The asparagus stages are the 12 stock mainsails, followed by the 6 Rocketry.

Those can send a full equipped core station attached to the biggest Rocketry tank with 6 radial tanks and engines, 4 of them will be used for orbital manoeuvers and the last 2 will stay with the full main tank and the core station full equipped.

[rhoark]

From a munar orbit of 6km you need about 550 dV to break orbit and maybe 150 to arrest your descent - that's being generous. 3 TWR should be more than enough.

[Tripod27]

Didn't actually expect you to respond so I stopped checking the thread

Anyway, yeah the tipping is a problem, the issue is that the custom torsion bars I put between the wheels and the body are great at stopping the wheels from popping over bumps (like when you're messing around on the runway) but they make the actual springs on the rover wheels glitch up and stay fully out until enough force is applied to them, which is really hard to do on the Mun, and if you do apply it (generally by shifting weight left and right) you'll probably tip it

As long as I have the fine controls on, never go over 15 m/s and never turn while going over 8 m/s while on the mun though, it does okay. Thanks for the designs, seems like booster aren't the way to go? I'll be removing the nosecones (until they fix them so they're anything other than extra weight/drag) but hopefully with a bit of modification I can stick enough power on the top stage to get me to Duna (and if not, I have a refueling station up now anyway)

[stupid_chris]

Yeah I know nosecones are useless for now, but they look a lot better and they usually change below 10m/s of delta V and if it's significant and you really need it, you might want to change your thing because it's tight on fuel

And for the tipping problem, the best you can do to prevent it is to have a large wheel base and a low CoM.

And for the boosters, I rarely ever use SRBs. They're not often suited for large payloads. They would've been useful here if I would've needed an extra 200m/s, because other pair of orange tanks with mainsails would be overshooting. And your best bet while designing heavy launchers is to keep it simple and keep what you have above as light as you can. When working with stock parts, double orange tanks with the small 2.5m tank at the bottom to prevent the mainsails from overheating is the way to go. You asparagus stage them up to three pairs. Then if that isn't enough, you go for smarter designs: you change the mainsails for engine clusters, you add a bit more fuel depending on your TWR, you create a third upper stage for the high atmosphere, etc. If you want to aim for Duna, I recommend changing the tug to make it work on nuclear engines, you'll get a much greater reach.

So yeah, give me a shout if you need any more help!

[Tripod27]

Nukes on the tug would be good actually, most of the slowing would be done by a few parachutes I'll probably stick somewhere on the thing anyway

Thanks for the help, man!

[stupid_chris]

Watch out though, if you want to land on Duna, parachutes only won't be enough to slow you down, you'll have to do a half powered landing because here atmosphere is rarely thick enough to solely use parachutes!