33.46 Ton Lifter?

[ginsweater]

Huh, actually the LKO capacity of my "standard medium lifter" that I use all the time is just about 60 tons. You can see it in this album lifting a 54-ton spaceplane into a 350/90 elliptical orbit - those craft files are over in its thread if you want to see how it's put together. If I need a bit more capacity I can add another half-height tank to the seven main stacks and it still lifts off without trouble.

...yeah, I call it my "medium" lifter. Do I have a skewed view of these things? When 0.17 first came out and I assumed I would need insanely huge landers for other planets I built this 1200-ton tower of lag and explode which, on the rare occasions when it holds itself together for an entire launch, pushes 130 tons to solar orbit. (Not posting the .craft for that one because someone might download it and I don't think I could live with myself if that happened.)

[bsalis]

Well 33.46 isn't that much. However you will need to do a lot better than that if you want to get to Eve, land, then return. If your happy to use MechJeb to do the Ascent in order to deal with the lag, then you can lift a heck of a lot more. This craft of mine is 280 tons in LKO...

I recommend sticking with lateral-crossfeed staging. Asparagus style if your really keen, but it's not necessary. The buffed 1500s thrust Mainsails are your friend. Other than that, just follow good practices and apply struts where needed.

[Gunhed]

I don't use mechjeb. It's not installed, and never will be. Plus that looks like way more than is needed to get to duna, land, and get back.

I highly doubt, that you can go to Duna and back with 33-40 tons...

I always try to be on the save side, fuel wise.

Cheers

[Punk]

I don't use mechjeb. It's not installed, and never will be. Plus that looks like way more than is needed to get to duna, land, and get back.

http://i2.kym-cdn.com/entries/icons/original/000/007/508/watch-out-we-got-a-badass-over-here-meme.png

...you get the idea

[SpaceGibsy]

or you just take a look at my proofen eve-return craft. http://kerbalspaceprogram.com/forum/showthread.php/23491-EVE_M-%28madness%29-the-first-cpu-friendly-eve-return-design!-%28-howto-fly%29

it takes ~60tonns into LKO using only 7000kn of thrust.. according to my tables you should need not more than 4000 to get your 36 tonns up there

and by the way.. you are telling me you designed an craft that manages LKO->EVE->Return with 36tonns? I've tryed a lot and my smalest design for this counts 50tons. If you so far only checked your dV requirements - then im sure that they are wrong. After dozens of tests i came to the point that you need at least 7100m/s dV just to get an eve orbit. i hope that helps with your calculations.

Edited October 17, 2012 by SpaceGibsy

[EndlessWaves]

I highly doubt, that you can go to Duna and back with 33-40 tons...

We were having a discussion in the See Space on a Single Engine challenge thread about whether it was possible to land on duna and return on a single Aerospike engine (i.e. 16 tons or less) starting from the launchpad. It is remarkable close as to whether you can do it, r_rolo came up with a design he reckoned was only 200m/s DeltaV off but the challenge is still open.

33 tons from orbit should give you plenty of margin for error to do it.

[r_rolo1]

With 33 tons you can definitely go to Duna and back: I already done it with a combo of 2 aerospikes and a Lv-909 and a total weight below 30 tons IIRC ( definitely below 33 ).

Going and back one one engine is another beef though :/ Like EndlessWaves says I've been remarkably close of making it but I've been finding hard to get any better than being short by some hundreds of dV units

[Qumefox]

http://i2.kym-cdn.com/entries/icons/original/000/007/508/watch-out-we-got-a-badass-over-here-meme.png

...you get the idea

Yes. Yes we do. And?

I honestly don't care if other people use mechjeb or not. I don't, and I don't like being told it's needed. Also, craft that are stated to /require/ mechjeb to even get in orbit, likely aren't very optimised or reliable designs.

And 40t is plenty to get to Duna and back.

Edited October 17, 2012 by Qumefox

[AmpsterMan]

needs a parachute and asas (for us non-mechjeb users) the staging can be simplified since the first boosters and the first droptanks empty within a second of each other. so you can just hang on to the srb's for another second and dump them both at once.

You also have a staging issue where two of the top stage aerospikes are lighting in the first stage, and burning through the tanks below them.

after fixing said issues, I got it into a 100km lko with 902m/s remaining on it.

now to try some tweaks I think might help and try again.

launch 1: 902 m/s remaining - base design

launch 2: 928 m/s remaining - fired all four SRB's at launch instead of staggering them.

launch 3: 975 m/s remaining - above + replaced all the LV-T30's with aerospikes+engine housings (so they could be attached to the tri-couplers... stupid aerospikes)

Oh wow, you really broke it down didn't you? Thanks for that . I might not be the OP, but I have certainly learned quite a bit today

[Qumefox]

Yeah I expect aerospikes to change at some point. that or the LV-T30's to be improved somehow. I'm sure aerospikes not wanting to attach to tricouplers is intentional to reduce their usability for engine clusters, to try and give the LV-T30 a reason to actually be used. As it stands now.. you can stick an aerospike on one of the .3 mass engine housings, and get more thrust, better Isp, and still be able to stick them anywhere a LV-T30 can go... Actually more places, since you can stick the engine housings directly to the sides of things. All for only a .05 mass penalty.

Right now, at least from a performance standpoint for engine clusters. There's zero use for the LV-T30. About the only situation the T30 is superior, is when you need a single engine, and need it stacked in a vertical stage, and don't need thrust vectoring.

As far as the testing. I knew changing to aerospikes was going to help. I was actually kind of surprised it didn't help more than it did.

And on the SRB staging changes helping.. It was really just an experiment. I wasn't sure if it'd help or hurt.. After thinking about it. I think the reason firing them all at the beginning helps is due to the total delta-v added by them being relatively the same as the original staggered firing at the relatively low altitudes it happens, and most of the benefit actually comes from being able to lose more mass earlier in the flight when dumping them all at once, as opposed to two just being dead weight for the first stage.

Edited October 18, 2012 by Qumefox

[Temstar]

Right now, at least from a performance standpoint for engine clusters. There's zero use for the LV-T30. About the only situation the T30 is superior, is when you need a single engine, and need it stacked in a vertical stage, and don't need thrust vectoring.

That's a legit niche and it exists: engine for Apollo style CM/SM cismunar spacecraft. So basically parachute, 3 man pod, decoupler, big ASAS, big RCS tank, 1600L tank and LV-T30, with a sprinkling of RCS thrusters and long lander legs. For such a spacecraft:

Can't use one aerospike as you need booster underneath to get it into orbit. (Unless you only use parallel stage asparagus boosters) Can't use two or more Aerospike because that's too powerful/heavy

Can't use one LV-N because they are too tall for lander legs. Can't use two or more LV-N because they're extremely heavy and not worth it for the amount of fuel you are going to burn with them

Probably don't want to use Poodle because it's much heavier but only offers 20s better Isp. You don't need vectored thrust (see below)

No point in using LV-T45, as it's heavier and have worse TWR. You don't need vectored thrust because for a spacecraft that size command pod's reaction wheel is more than enough

And because LV-T30 looks better, it looks most similar to the SPS engine on Apollo SM.

[Qumefox]

When trying to figure out what to do with the 3 relatively useless 'test' craft I ended up in 100km lko from the other night's testing, I decided I might as well practice orbital rendezvous. Took a few hours, but I finally got all three into a parking orbit within 50m of each other heh.. With no mechjeb Matching the third ship to the other two, took considerably less time than than matching the second ship to the first. I didn't think I did to bad, considering these things have zero RCS on them.

Also. I disagree. For one. I wouldn't use RCS on that lander.. I'd dump it to save the weight, and go with the T45 with the vector thrust on it. For me, light craft just don't need RCS.. Like you said, the pod reaction wheel is perfectly capable of handling attitude control. Yes the T45 is heavier and has a lower TWR, but a lander with no RCS will be easier to cancel lateral motion with a gimballing engine than it will with a fixed motor. And you'll get MUCH higher delta-v without that heavy RCS tank, regardless of what engine is used.

Also. I might be alone in this camp, but looks don't really mean squat to me.. If i'm trying to do something, it's function over form.. always. I also have little interest in recreating any 'real' spacecraft.

My typical playstyle is to try to get the job done using as few parts as possible and have it be fairly reliable.. I.E.. not have to deal with it randomly exploding 5 times for ever one good launch.

Edited October 18, 2012 by Qumefox

[Temstar]

Also. I disagree. For one. I wouldn't use RCS on that lander.. I'd dump it to save the weight, and go with the T45 with the vector thrust on it. For me, light craft just don't need RCS.. Like you said, the pod reaction wheel is perfectly capable of handling attitude control. Yes the T45 is heavier and has a lower TWR, but a lander with no RCS will be easier to cancel lateral motion with a gimballing engine than it will with a fixed motor. And you'll get MUCH higher delta-v without that heavy RCS tank, regardless of what engine is used.

I'm indifferent to RCS vs no RCS. I like it and I find it invaluable for small final adjustment weather it's powered descent or docking. That said I've also done both powered landing and docking (those two dockings were nailbiters) with only main engines so I agree that if you feel confident doing them the weight saving is great.

However, I disagree that LV-T45 is a better lander engine because it's easier for lateral motion cancelling. When you're using main engine to cancel lateral motion you are using it much like a helicopter pitching around to stop to a hover. LV-T45's vectored thrust in no way help this process since you should only be firing your engines in bursts in a fixed direction against the direction you're moving laterally (and diagonally up of course, to not come crashing down). You're not going to be leaving your engine on and pitching and yawing all over the place with that lander like they did in that Apollo 13 movie. If you do that you'll introduce lateral movement to other direction while you adjust pitch and yaw. Since you're not yawing or pitching while the engine is firing and command pod reaction wheel by itself is powerful enough for pitch and yaw control while engines are not firing LV-T30 have the advantage of being lighter and more powerful.

[AmpsterMan]

I used LV-30 in the first stage because I always assumed that aerospikes were not supposed to be tricoupled. That is why I didn't use the workaround you described. As far as the LV-30 goes as a niche, I have used it before as a transfer stage engine to mun and minmus and it worked. But my latest design philosophy to getting to those moons has been to do away with the transfer stage all together and just use the lander stage as a transfer stage as well.

As fat as a lander goes, I have used the LV-909 almost exclusively for those. On my heavier landers (like a prototype Duna lander I have) I use the poodle.

I used to use RCS for help with landing more precisely on Mun. Don't really use them any more TBH.

[Stevenator1]

I used LV-30 in the first stage because I always assumed that aerospikes were not supposed to be tricoupled. That is why I didn't use the workaround you described. As far as the LV-30 goes as a niche, I have used it before as a transfer stage engine to mun and minmus and it worked. But my latest design philosophy to getting to those moons has been to do away with the transfer stage all together and just use the lander stage as a transfer stage as well.

As fat as a lander goes, I have used the LV-909 almost exclusively for those. On my heavier landers (like a prototype Duna lander I have) I use the poodle.

I used to use RCS for help with landing more precisely on Mun. Don't really use them any more TBH.

RCS has become incredibly outdated, requiring crazy numbers of RCS thrusters to actually work on large rockets. Gimballing is all that is really needed now.

[Qumefox]

RCS is still useful for attitude control on REALLY large craft where timings are critical. And for low delta-v changes in space where it's useful to be able to traverse the craft on any axis without changing it's orientation (i.e. docking). Beyond those two scenarios, RCS is pretty much a waste of mass.

[CleverWalrus]

After plenty of testing i managed to build up a good looking launcher able to bring to LKE about 50 tonns.

There are 3 stages:

1) 5x Large engines taking fuel from 6x lateral tanks (up to 3/4 km)

2) 3x Large engines taking fuel from 3x tanks each engine (up to 15/20km

3) 1x Large engine with 3 tanks.

I did extensive testing using asparagus staging but the 3x engine burn for longer time seems to be more effective at delivering the payload.

During the end of stage 2 the TW ratio become very impressive, reaching about 3, be sure your payload can handle it or throttle down.

In the screenshoots you can see the launcher with just a 3m capsule on top of it, craft file attached too, no mods required.