Mod or not? I am trying to fix 4 rocket engines under that big orange tank

[fastbikkel]

I saw pics of people having 4 small engines under the orange tank.

But that does not work the way i thought.

I i choose snap angle (or not) and select quadruple (right next to snap angle) it will not put 4 engines on it.

It is either one, that fits on the green dot or none. Or i have to fit them on the side of the tank, but under it is not possible. It will not turn green to indicate it will fit.

Maybe people have a mod installed that enables that, i have no clue. It sure looked like stock.

( I am trying to get more take off power on a rocket without having to enlarge the rocket. KSP crashes if i make it bigger and it really is not big at all to begin with)

Now my attempt might not even give the expected result, but i want to try.

[Richy teh space man]

Try attaching one of the square frame thingamabobs from under the structure tab, then attach the engines to that.

[Dacsi]

You have to put the cubic thing (http://wiki.kerbalspaceprogram.com/wiki/Cubic_Octagonal_Strut) in the "Sctructural" tab and then under them attach the engine with 4x symmetry..

[Geschosskopf]

Taki117 made a nice video of how to do this with stock parts:

There are, however, mod parts especially designed for this purpose. The advantage of the mod parts is that you only need 1 of them instead of however many cubic octagonal struts, but of course you have to have a mod. Nova-Punch has them, and they've been copied into Near Future.

[fastbikkel]

Great ideas guys!! Thanks, i will try the suggestions.

My mind is not creative enough, that is clear to me. But i am improving.

[Tank Buddy]

Are you looking for this? http://forum.kerbalspaceprogram.com/threads/50983-Maybe-clustered-engines

[Streetwind]

Why not simply go for the quadcoupler or quad adapter? Should be under structural parts. Will give you 4 mid-sized mounting points below a large-sized one.

If you play Career you need to research them first. The quadcoupler is somewhere in the middle of the tech tree, and the quad adapter near the end.

[fastbikkel]

Why not simply go for the quadcoupler or quad adapter? Should be under structural parts. Will give you 4 mid-sized mounting points below a large-sized one.

If you play Career you need to research them first. The quadcoupler is somewhere in the middle of the tech tree, and the quad adapter near the end.

yeah but i thought the quadrupler does not have the possibility to cross fuel through it, this is the limitation in my mind the whole time. I keep discovering my mind thinks too hard of this.

I automatically assume i need to add fuel pipes and such. It also took me a while to realise i can fit lamps anywhere on the rocket and it automatically works if i have power.

[Streetwind]

I was worried about that at first as well. However, I found that if a part blocks fuel flow, it generally states so in its stats window (true for all stock parts, your mod experience may vary) in easy to see orange text. See a decoupler for reference.

My main workhorse rocket has used a quadcoupler with engines for a long time now, works quite beautifully. Not as much thrust as a mainsail, but the fuel efficiency is much better.

[Claw]

I will tack onto this. The stock part you are looking for is the quad coupler. It will allow fuel to pass through without fuel lines and you can run all four engines, assuming you are connecting it to the orange tank first, then affixing the four engines. Realize if you build it the other way, you might experience fuel flow problems.

One thing to note (there was a recent thread about this) is that some of the engines in a quad layout will cause the rocket to spin. So you'll have to design around that.

http://forum.kerbalspaceprogram.com/threads/68424-Question-about-slow-rotating-craft-%28gyro-reaction-wheel-what-is-gimbal-%29

If you have problems with spinning using a quad design, try reading this thread. Especially page 3 and on.

[Geschosskopf]

I will tack onto this. The stock part you are looking for is the quad coupler. It will allow fuel to pass through without fuel lines and you can run all four engines, assuming you are connecting it to the orange tank first, then affixing the four engines. Realize if you build it the other way, you might experience fuel flow problems.

The thing about all the stock adaptors is that they don't have an attachment point on the centerline for the cluster side. This can be a problem if you want a single stack underneath. So this way, the cubic octagonals and the mod cluster adaptors are better.

And yes, the stock quad adaptor has flow issues going in reverse. For instance, it won't do well as a way to airhog on SSTOs

[fastbikkel]

Hey guys,

Thanks again for the replies, i appreciate it.

I did fix a quadrupler onto the fuel tank, then added 4 smaller rocket engines. The result was very interesting, i noticed i needed more throttle on initial takeoff, but later on (above 14km) i had a substantial amount of fuel left, in comparison to the same rocket with mainsail engines.

It seemed more fuel efficient. I did not run into a lot of overheating problems.

Now the frame rate dropped dramatically because of the increased amount of engines.

Tonight i will continue testing some other suggestions. I am definately improving, i just need to let go my reallife logic when it comes to KSP sometimes.

[fastbikkel]

...... is that some of the engines in a quad layout will cause the rocket to spin. So you'll have to design around that.

http://forum.kerbalspaceprogram.com/threads/68424-Question-about-slow-rotating-craft-%28gyro-reaction-wheel-what-is-gimbal-%29

If you have problems with spinning using a quad design, try reading this thread. Especially page 3 and on.

Excellent tip, i had seen that yes. Now i did not notice spinning with my quadruple setup, i did notice it in my mainsail config, but i seemed to deal with it.

[Streetwind]

I did fix a quadrupler onto the fuel tank, then added 4 smaller rocket engines. The result was very interesting, i noticed i needed more throttle on initial takeoff, but later on (above 14km) i had a substantial amount of fuel left, in comparison to the same rocket with mainsail engines.

It seemed more fuel efficient.

This is true. The mainsail is not very fuel efficient.

You can judge rocket engine fuel efficiency by looking at the value named I_sp (meaning specific impulse). It is a measure of how "hard" the engine throws its reaction mass out the back, and thus, how much forward momentum you gain from it doing so. Engines with a high specific impulse can get you more total acceleration (and thus a higher final speed) out of the same amount of fuel than those with low specific impulse ratings. Therefore, I_sp is functionally identical to a car's "gas mileage" spec.

Do not confuse this with thrust, however. Total acceleration is one thing, but thrust describes how quickly you get it. Engines with high I_sp (like the LV-N) tend to have low thrust, and engines with high thrust (like the mainsail) tend to have low I_sp. In your case, you benefit from switching to smaller, higher I_sp engines because you apparently did not need all the thrust the mainsail provided.

Thrust and I_sp are interrelated when determining actual fuel consumption. You pay X amount of fuel per second for every kN of thrust, and the X is determined by I_sp. If you have two engines with exactly the same I_sp, and one generates 200 kN of thrust while another does 400 kN, then the second one will consume exactly twice as much fuel per second as the first. But if the second one had a lower I_sp, as high thrust engines usually do, then it would have to spend more than twice the fuel.

Generally, rocket engines have two I_sp values: "ASL" (atmospheric sea level) describes what you get on the launchpad, and "Vac" (vacuum) describes what you get outside the atmosphere. The second value is always larger because the presence of an atmosphere causes backpressure on the rocket engine's exhaust which lowers its efficiency.

[CalculusWarrior]

I like to put the small fuel tanks between the main tank and the engines, just so that I can have fuel crossfeed without any major headaches (plus I feel they look nicer)

[Streetwind]

That requires enabling part clipping via the dev menu though, doesn't it?

[Claw]

And yes, the stock quad adaptor has flow issues going in reverse. For instance, it won't do well as a way to airhog on SSTOs

Not true for air intakes, they work fine.

Why? Because intake air acts like electricity and monopro. It doesn't matter what the intakes are connected to, so long as they are there.

[Claw]

The result was very interesting, i noticed i needed more throttle on initial takeoff, but later on (above 14km) i had a substantial amount of fuel left, in comparison to the same rocket with mainsail engines.

It seemed more fuel efficient.

I am definately improving, i just need to let go my reallife logic when it comes to KSP sometimes.

Improvement is great!

By the way, there is noting illogical with what you said above. If you replace a mainsail with four LVT-30s (or 45s), you're going to experience exactly what you said.

LVTs are more fuel efficient (higher ISP) than a mainsail, so you will end up getting better gas milage for a given flight.

4 LVTs also have less thrust than 1 mainsail. So you will need to have a higher throttle setting to have enough thrust to takeoff. You could also run into the problen where 4 LVTs can't lift your rocket, but 1 mainsail will. The total thrust outpu is different.

EDIT: Oops, sorry for the repeat info. I'm using my phone and I missed Streetwind's comment.

Edited February 14, 2014 by Claw

[Poynting]

I enjoy using the tail sections. Totally worth the extra mass for the asthetics

[Claw]

That requires enabling part clipping via the dev menu though, doesn't it?

I don't know about this specific example, but the editior lets you get away with a lot for the little 100 tanks. Radial attach them to the side and rotate. The editor is pretty liberal with nose cones too (rightfully so0.

[Red Iron Crown]

Engines with high I_sp (like the LV-N) tend to have low thrust, and engines with high thrust (like the mainsail) tend to have low I_sp.

A note on this: This is only true in KSP for game balance reasons. In the real world, thrust and Isp are orthogonal. It is entirely possible to make engines that are both high Isp and high thrust.

In particular, the LV-N is a nerfed version of the real NERVA, which had excellent TWR and high Isp, both in atmosphere and vacuum. But if the LV-N was like that it would quickly displace all the other engines. Real nuclear rockets are just plain superior to chemical ones in every respect other than public acceptance.

[Geschosskopf]

Not true for air intakes, they work fine.

Why? Because intake air acts like electricity and monopro. It doesn't matter what the intakes are connected to, so long as they are there.

Nope, the 3x and 4x stock adaptors are bugged when it comes to intakes. Only the 2x adaptor works correctly with intakes.

Consider the RAPIER engine with automatic switching and not using adaptors. If you have 1 intake per engine, it will flame out about 23km. If you have 2 intakes per engine, it won't flame out until 30km or so. In both cases, the flameout occurs with the Resource tab shows IntakeAir at 0.

Now, suppose you put the intakes on adaptors. With the 2x adaptor, you get the same as above, flameout about 30km at 0 IntakeAir. If you use the 3x or 4x adaptors, however, things are different. The Resource tab shows the huge amount of IntakeAir you'd expect from all these intakes. HOWEVER, the engine will only use 1 of the intakes. Thus, the engine will flame out at 23km even though the Resource tab still shows like 2.5 IntakeAir remaining.

[Jouni]

Now, suppose you put the intakes on adaptors. With the 2x adaptor, you get the same as above, flameout about 30km at 0 IntakeAir. If you use the 3x or 4x adaptors, however, things are different. The Resource tab shows the huge amount of IntakeAir you'd expect from all these intakes. HOWEVER, the engine will only use 1 of the intakes. Thus, the engine will flame out at 23km even though the Resource tab still shows like 2.5 IntakeAir remaining.

I could not replicate this. I built a simple SSTO with a probe core, a fuel tank, a RAPIER engine, and four ram air intakes attached to either a quad-coupler or a quad-adapter. In both cases, the RAPIER switched to closed cycle at 34 km, when surface speed was 1600-1700 m/s and vertical speed around 200 m/s.

[Claw]

Nope, the 3x and 4x stock adaptors are bugged when it comes to intakes. Only the 2x adaptor works correctly with intakes.

Consider the RAPIER engine with automatic switching and not using adaptors. If you have 1 intake per engine, it will flame out about 23km. If you have 2 intakes per engine, it won't flame out until 30km or so. In both cases, the flameout occurs with the Resource tab shows IntakeAir at 0.

Now, suppose you put the intakes on adaptors. With the 2x adaptor, you get the same as above, flameout about 30km at 0 IntakeAir. If you use the 3x or 4x adaptors, however, things are different. The Resource tab shows the huge amount of IntakeAir you'd expect from all these intakes. HOWEVER, the engine will only use 1 of the intakes. Thus, the engine will flame out at 23km even though the Resource tab still shows like 2.5 IntakeAir remaining.

I'm not in a position to test this at the moment so I will double check, but I recall using quad adapters with intakes and it didn't have this problem.

I'll try it in several configs tonight.

[Geschosskopf]

I could not replicate this. I built a simple SSTO with a probe core, a fuel tank, a RAPIER engine, and four ram air intakes attached to either a quad-coupler or a quad-adapter. In both cases, the RAPIER switched to closed cycle at 34 km, when surface speed was 1600-1700 m/s and vertical speed around 200 m/s.

Well, I'll take your word for it.

KSP is a wonderful thing in that it lets us do actual peer-reviewed Science! Different results for different users, just like in real life. So like I can't get the Kraken drives to work for me even when I download ships that I've seen work perfectly in videos and I do the same maneuvers with them, now you can't reproduce my results. This makes everything a venture into at least a partial unknown, which helps keep the game from getting boring .