Transfer engine discussion

[Bigbootie]

Hello all,

I have a master plan brewing and was wondering what the rest of you use for transfer engines. Many times in the past I have made interplanetary transfer vehicles and always used the nuclear engines due to the efficiency. To hell with efficiency I say!! I like to drive, not stare at the screen while the numbers slowly tick by. What kinds of set ups for non-nuclear transfer engines are you guys using that get the craft started and "stopped" quickly and still allow for say....a medium manned lander with the transfer module in orbit and reusable(provided that it is refueled) and/or enough fuel to get anywhere from Kerbin and not necessarily come back? Pix would be great.

Unfortunately I am at work and far away from any gaming capable computer. However, I can participate in the forums and greatly enjoy reading them daily.

[Jarin]

Mainsails are great transfer engines. You just have to build big enough.

[Madrias]

The trick with nuclear engines is to use enough of them to be fast. At least, that's my strategy.

If I'm pulling a good old "Hang the efficiency, full steam ahead!" run, Mainsails or Skippers tend to throw you around quickly.

[Daze]

I think that a good compromise is the LV-45 or 909

[Moar Boosters]

I'm fond of the poodle. I know its more efficient to use 48-7S engines, but rockets using them normally look ugly. The poodle just fit better on my designs and I have absolutely no problem with it being inefficient, it just means the lower stages have to be bigger.

[Slam_Jones]

Well, I go for 390 ISP drives:

KR-2L if I want tons of TWR

LV-909 for lighter-weight ships

Poodle as a middle-ground

I've been planning a ship that will carry all three (KR-2L x1, Poodle x2, LV-909 x 8) and use action groups to switch between them as needed

I've also considered the Toroidal Aerospike for atmospheric landers and transfers due to the high atmo ISP

Edited December 11, 2014 by Slam_Jones

[Trentendegreth]

i note, nobody says "ion"..... LV45, poodle, skipper. depends on the size of the craft.

[Orionkermin]

I'm a big fan of the KR-2L as an interplanetary injection engine. I use the smaller stuff on the CSM to come back when there isn't so much mass left in the mission profile. Works great for Apollo style missions to the Duna or Eve systems. Been to Dress this way as well.

[Rune]

i note, nobody says "ion"..... LV45, poodle, skipper. depends on the size of the craft.

I would totally use them... if it wasn't for the ridiculously small fuel tanks. Part count jumps so high once you want to push a big payload, it's not funny anymore. That's one of the things I secretly want Squad to provide, a 1.25m xenon tank so I can consider absurd solar-powered contraptions that take hours to break orbit. I've done it before (Munar transfer of a multipart Mir-Style station), and I would do it again... if it weren't because a x4 lag is easy to get with the dozens of little tanks, and that multiplied by a 2h escape burn... not funny anymore. And let's not even contemplate the task of refuelling...

Other than that, I just go easy on the nukes. I do webbrowse a lot during burns, don't get me wrong. And no, I don't use mechjeb: the new autopilots will be a godsend.

Rune. Clusters of Ions? Totally workable. But the tanks? I want big stock ones!

[Trentendegreth]

I would totally use them...

Rune. Clusters of Ions? Totally workable. But the tanks? I want big stock ones!

Im with you there, or a stock version of Tweekscale. maybe not for every part but the tanks for sure.

[Norpo]

For serious missions, I go with nuclear engines. Top notch ISP, (and i'm normally using a big enough rocket that ion engines would be ridiculous at that point). Serious missions would be, say, a Jool-5 mission.

just-for-fun missions, either the Poodle or the Skipper. A duna lander and return would fall in this category.

For VERY fun missions, Kerbodyne engine clusters. Many of them. Never getting out of orbit and just watching the explosions would fall into here. (I tried to make a giant fuel depot, 289 parts and I was getting 1 fps a second, I was lucky when it exploded)

[GloriousWater]

I throw a KR-2L at every problem I have. After all once you start using 3.75m parts to lift the ship, you might as well use them on the transfer stage.

For the return stage I usually make something lightweight like a cluster of 48-7S on a short Rockomax tank with the command pod docked to it. The nuke isn't that appealing to me as I don't like the long burn times, but I still use it on some medium designs.

Although I have used KS-25x4s for part of my transfer once.... 50 second Eeloo burn anyone?

[John FX]

I tend to put a central NERVA surrounded by a few rings of the thruster just bigger than the ant one (the name escapes me right now) the 48-7S?

I put three rings of those controlled by action groups so I can get varying thrust/efficiency all the way from loads of thrust (TWR>1) to loads of efficiency when only using the NERVA.

This is my SSTO I built using the technique, it has funky docking port control fins. Engines are turned off in stages for the launch, increasing efficiency until the NERVA does the last bit on its own.

[Ikaneko]

I'm a sucker for Poodles in Mün and Minmus transfers. I guess I just like the immediacy of them due to their quite high thrust.

[Rolanvorxariat]

I typically use a KR-L2 for my one-way space probes for the short transfer burn, and it works with my KLS-Block III Heavy rocket, and my probes usually carry some other "Hitchhiker" craft like in real probes (Hyabusa-2, Rosetta-philae, Cassini-Huygens, etc), but since i consider NERVAs incredibly high-tech, i instead use the KWR 1.25m Vesta engine. But after further testing (hyperedited into vacuum), I concluded the vesta was more efficient, so i would use it for my current Kolonation-Duna mission(Constellation style), and later on, the INTEGRITY permanent laythe base mission (INTEGRITY is also the name of the mothership-module design based on the Endurance from interstellar, same as with the base, though the actual INTEGRITY ship configuration is somewhat different. For my unrealistic interplanetary missions in my old save that i made when i just started ksp (summer 2014, 0.23.5), i used the NERVAs. but now it's left to the KR-L2 and the Vesta clusters.

[Red Iron Crown]

I use KR-2Ls for huge stuff, LV-Ns for normal-sized stuff, and ions for tiny stuff.

I would love a stock engine with ~600s of vacuum Isp and twice the TWR of an LV-N. I've made something close with a cluster of 4 LV-Ns and 1 LVT-30, gives 597s and a TWR of 4.5. But that is really bulky and part-count heavy, plus it's not suitable for smaller craft as it has 455kN of thrust.

[Laie]

To hell with efficiency I say!! I like to drive, not stare at the screen while the numbers slowly tick by. What kinds of set ups for non-nuclear transfer engines are you guys using that get the craft started and "stopped" quickly and still allow for say....a medium manned lander with the transfer module in orbit and reusable(provided that it is refueled)

Well, what kind of TWR do you have in mind? How heavy is a "medium manned lander"? How long is a piece of string?

"MOAR NUKES" works to a large degree, usually you can have accelerations on the order of 2-3m/s² without compromising much on delta-v.

Don't even bother with Poodles and the likes. You can get better TWR and delta-V if you use more nukes.

Assuming that a medium-sized lander doesn't warrant a KR-2L, Skippers are the next best; they tend to be better than aerospikes. If you want interplanetary range, TWR will still be slow at first, but improve quickly -- about half the fuel will be gone by the time you leave Kerbin SOI. For re-usable, I'd suggest to cook up designs where you can couple two or three, but only one actually flies to the destination; the other(s) immediately turn around and return to LKO.

[KevinW42]

Well according to this, for high mass, high TWR ships, the most efficient engines are either the KR-2L, or clusters of 48-7S if you don't mind a parts count out the wazoo.

[EndOfTheEarth]

Well, if you're in it for the kick and to heck with efficiency, my past few interplanetary missions have allowed me to bring a huge upper stage consisting of a KR-2L and S3-14400 into space along with my interplanetary tug (the part that usually does all the hauling with the LV-Ns and a big fuel tank). This way, when I dock my lander to the tug, I can transfer any remaining fuel from the lander launcher to the S3-14400, then I deorbit the lander launcher with any backup RCS, leaving me in orbit with the lander, the tug, and the upper stage.

Then, I get lined up for my burn, and boy is it a burn.

Usually, the upper stage conks out and gets dumped before I finish the actual burn, but the end total of this is that I can get the tug and lander to Jool still 90-some% full of fuel...and the tug itself is a S3-7200 surrounded by four Fl-T800s, mind you, so by the time I start needing to burn again to target a moon, I still have oodles of fuel to play around with.

Of course, the rockets to put these things into space in the first place are obscene, but hey! No budget, no efficiency control, no problem!

[Rune]

Well, what kind of TWR do you have in mind? How heavy is a "medium manned lander"? How long is a piece of string?

"MOAR NUKES" works to a large degree, usually you can have accelerations on the order of 2-3m/s² without compromising much on delta-v.

Don't even bother with Poodles and the likes. You can get better TWR and delta-V if you use more nukes.

Assuming that a medium-sized lander doesn't warrant a KR-2L, Skippers are the next best; they tend to be better than aerospikes. If you want interplanetary range, TWR will still be slow at first, but improve quickly -- about half the fuel will be gone by the time you leave Kerbin SOI. For re-usable, I'd suggest to cook up designs where you can couple two or three, but only one actually flies to the destination; the other(s) immediately turn around and return to LKO.

(emphasis mine)

You also took a page out of Von Braun's book?

Rune. WiP. Cookie for whomever guesses what it is!

Edited December 12, 2014 by Rune

[Majorjim!]

You can use what ever gets you there..

If you are impatient, use a powerful motor, if you are making a replica then use what ever engine fits the design and make it work.

Personally I don't have a preferred method. It depends on the overall design of the craft. Having said that, the nukes are generally the best choice for long missions.

They are just that bit more frugal with your fuel.

@RUNE, for whomever guesses what?

[LABHOUSE]

I use ions for stuff on the small side of normal unless it is past eve or duna systems, nukes for normal sized stuff usually (if not on the smaller side of normal) and lv 909 engines for large stuff, exception is a mission sent to past eeloo (way past), normal sized, I used a mainsail.

[Rune]

@RUNE, for whomever guesses what?

What it was I was showing, and why it fit with the Von Braun comment. But I think you already know what it is yourself... it's been months in the making now, on and off.

Rune. And most ships I build in a day or two.

[LethalDose]

I'm a big fan of the KR-2L as an interplanetary injection engine. I use the smaller stuff on the CSM to come back when there isn't so much mass left in the mission profile. Works great for Apollo style missions to the Duna or Eve systems. Been to Dress this way as well.

Ditto. For big payloads, its hard to beat the KR-2L. It has a very good vacuum ISP (380) and the best TWR in the game by a good margin.

Poodles and 909's are good for IP transfer upper stages for smaller payloads.

EDIT: Rune's post is the project rho or whatever, a proposed nuclear vessel with radiation shielding for the payload.

Edited December 12, 2014 by LethalDose

[Majorjim!]

What it was I was showing, and why it fit with the Von Braun comment. But I think you already know what it is yourself... it's been months in the making now, on and off.

Rune. And most ships I build in a day or two.

Yup I know what it is. No cookie for me.