why are there people who stick more than one nuke on their ships?

[andrewas]

This is my reason, more nukes let you slow down a whole lot faster when you finally get to where you are going. Im wondering, would it be better to burn a single nuke on your way out and only turn on the others when you get there or have them all burning the whole time? I think all of them would be better but the math in my head has been wrong before.

If you must bring multiple nukes, burn them all every time. The shorter your burns, the more you get out of the oberth effect. The only time you should ever fire only one engine is when making a course correction burn, where oberth effect doesn't come into play and the lower TWR gets you more precision on your burn.

[Jarin]

I think the common answer to this thread is clear by now. "Because I want to, efficiency be damned", which I wholeheartedly agree with. Nukes let me design interesting, futuristic-looking ships with multiple engine nacelles, while still getting something resembling reasonable dV.

Also, the OP appears to have stopped replying.

[SpaceSphereOfDeath]

I use a maximum of 3, due to FUEL LINES BUGGING OUT AND DISSAPEARING WHEN I RELOAD THE FLIGHT *looks angrily at bug checking team* and I typically just use LV-909s, smaller and (I believe) a better TWR ratio, and much more streamline, half the length of your rocket isn't a engine!

[regex]

Because I don't build transfer vehicle with TMRs less than 0.3. If it takes eight or twelve nukes to get that, so be it, but no transfer within the system will take more than fifteen minutes to execute.

[csanders]

this is over-engineering.

and it's another issue... people just cant build smaller, more efficient craft.

How do you propose we build smaller more efficient fueling stations?

When moving large amounts of fuel, multiple LV-Ns makes sense. For other craft a lighter less efficient engine might get more dV. Some just like the look.

Like all things Kerbal, the answer is "it depends."

[jwenting]

A lot of people seem to be concerning themselves with how other people are playing their games...

yup. See the "suggestions" and "addons" forum for far more people trying to dictate how others enjoy their game (mostly claiming that any way except their way is wrong and nobody should be allowed to play different from them).

[nimbim]

I use at most 2 for design reasons (damn lander legs too short!). I also cringe when I see ships with 16+ nukes or 8 ions.

However, you can do almost everything with very inefficient designs. Best anyone can do is point it out to people who care and let others have fun with them.

[Anton P. Nym]

I use up to 4 LV-Ns on my craft... and one one of them 4 may not have been enough because the estimated burn time for a Jool capture burn is 27 minutes. (It's a carrier with two aerospace planes and two VTOL landers.) If the craft's dry weight is big enough, the added engines don't impact total delta-V much and the shorter burns make the mission more practical.

-- Steve

[Dirty Bob]

What is this efficiency thing everyone is talking about? Jeb tells me all that matters is size.

[Mobjack]

I often use at least 2 LV-N's because it creates a more stable ship to launch. Having to support your entire ship on top of a skinny LV-N with 500 struts as you lift off is no fun.

Using one LV-N is overrated for efficiency especially if you have a big ship. I see people who focus on one idea in making their ship efficient, while neglecting other areas. It doesn't matter how efficient your ship is if you make inefficient maneuvers. One gravity assists will more than make up for the extra LV-N's you are carrying.

[FellipeC]

I usually use they in pairs when attached radially, to keep center of thrust in right place, or when doing landers, sometimes needs more to TWR of the ship be > 1 on the planet I intend to land.

[Levelord]

What is this efficiency thing everyone is talking about? Jeb tells me all that matters is size.

It's not the size that matters but how you- ADD MOAR BOOSTERS.

[CreepyD]

I have used two on occasion if I want to keep using them to land with.

Having 1 at the back is no good because no lander legs are long enough, so I need to radially mount, which of course then requires two.

Personally I wouldn't go higher than two. If I need a higher TWR I'll use another engine.

[Boris_T_Roach]

3 is ideal

4 or more is a waste and 1 means a burn time in the days.

Attatch them radially on the bottom of a jumbo orange tank, with 3 FT400 tanks and you have an interplanetary drive system thats been the mainstay of my space program for over a year now.

Ok its been tweaked here and there with modifications such as an ejectable aero cap on launch and chucking on some single solar panels for when Jeb forgets to unfurl the main solar panels.

but it works pretty well, most burn times are between 10 mins and 20 mins, although for a heavy load (spare fuel tanks, some rovers, a largeish lander and some single shot probes) going to Jool, burn time may rise to 25 mins... but then its time for a bath/shower anyway.

KSP is all about having fun..... SSTO stuff and aircraft.. zzzzzzzzzZZZZzzzzzzzzzz Building a huge manned probe to investigate the strange formation seen at Vall

Boris

[Xacktar]

I do it just so I can cackle like a maniac behind my desk as the things burn.

[Caelib]

Once I discovered it's possible to do time acceleration during a burn (ALT + .), I only ever add one engine. Prior to knowing this, I mostly did it to reduce those extremely long 15+ minute burns.

[regex]

Once I discovered it's possible to do time acceleration during a burn (ALT + .), I only ever add one engine. Prior to knowing this, I mostly did it to reduce those extremely long 15+ minute burns.

My favorite part is putting enough nukes on a ship to reduce my burn times to less than 15 minutes and then physics warping so the burn isn't any longer than four minutes.

[Jouni]

I used to care more about efficiency. Then I realized that ships that are easy to fly are more likely to complete their missions succesfully and efficiently. Because of that, my current designs have more engines, more RCS, more SAS modules, more batteries, more solar panels, more RTGs, and basically more of everything than could be justified by theoretical efficiency considerations.

[nholzric]

At the risk of feeding the troll, this is why people use more than one LV-N. As a million people have already said: more LV-N's reduce your burn time but also the larger the craft the cheaper it is to buy that reduced burn time.

This is for a craft with three Rockomax X200-32 Fuel Tanks (1440*3=4320 units of liquid fuel). The different colored lines represent the total mass of the craft when starting a 1000m/s burn. This is approximately as large as my "There And Back Again" style interplanetary craft, but these are small compared to the behemoths many people post pictures of.

[Epthelyn]

Once I discovered it's possible to do time acceleration during a burn (ALT + .), I only ever add one engine. Prior to knowing this, I mostly did it to reduce those extremely long 15+ minute burns.

Any interplanetary craft built in orbit will almost certainly suffer from unexpected and spontaneous deconstruction when physics warp is applied, if not before.

It is the same large vessels upon which multiple nukes make things bearable.

[LostElement]

I modified the Nuke slightly to be slightly more efficient and reduced it's mass from 2.5 to .975. Why? Because it's my gameplay.

[Skorpychan]

Because I'm hauling things behind it, and so need a non-centerline engine. So, I use two nukes. This ALSO brings down my TWR to the point where burns happen in minutes and not hours while hauling a space station around the inner system.

Going further will probably require three or four nuke engines. Or possibly a 'get me the heck out of here' stage with a couple of Skippers on sidepods.

[Silverchain]

I've done some testing to determine the tradeoff between loss from added mass and gain from using the Oberth effect from Kerbin orbit.

Test craft Regenbogen Oberth in 150km x 150km LKO.

It is fitted with five LV-Ns, four of which are discarded here to carry out a burn using only a single engine.

(Strictly speaking, each LV-N has a docking port attached, so they're slightly heavier than normal; I could've discarded them but it's nice to have a stock in orbit!)

By save-scumming I started it from more or less the same point each run (the orbit is near circular anyhoo), and flew the best path I could to raise the orbit to a close approximation to 40Mm x 40Mm, slightly inside the orbit of Minmus.

I was flying manually, but it wasn't particularly complicated. It would be interesting to repeat with an autopilot. I made two runs for each config and chose the better.

This is what happened flying with 1, 3, and 5 engines:

1 engine: used 1185 dV from a total budget of 7085 dV.

3 engines: used 1121 dV from a total budget of 6236 dV. (+64, -849 vs base)

5 engines: used 1109 dV from a total budget of 5576 dV. (+76, -1509 vs base)

In short, while there is a saving to be made from the Oberth effect, it's eclipsed - for a ship of this type and for this run - by the loss of total dV budget entailed by the extra mass. You need less dV to get to the same place, but you have much less to begin with.

I expect, though I won't try right away, that starting from a lower orbit (say 75km x 75km) would increase the gain from the Oberth effect more for the multi-engine rigs, and generally reduce the dV requirement to reach 40Mm x 40Mm for all configurations.

I expect that starting with a more massive ship (say if I stick another Big Orange on the front) would do the same thing.

I expect that starting from Eve or Jool orbit would do the same thing, and anywhere else would reduce the gain.

Thoughts?

Edited January 22, 2014 by Silverchain

[-Velocity-]

Why are there people who put more than one nuke on their ships? If you're actually wondering this, then I've got a question for you-

Why are there people who think I want to wait 14 hours to make a 2000 m/s delta-V change while a single LV-N producing 60kN of thrust accelerates my 1500+ ton interplanetary supertanker at 0.04 m/s^2 (0.004 g)? Oh and, 14 hours would be a best-case scenario; in reality, the sim slows down to 1/3 speed so that it would really take around 2 days real time to make just a 2000 m/s delta-V change.

No thanks. I just put four NovaPunch 2.5 meter NTRs (1.2 MN, acceleration = 0.8 m/s^2). It can still take hours to do some maneuvers, but at least it's doable. I can go read a book or work on a paper or programming project while making my burn to whatever planet needs more fuel, a fresh crew, and new equipment

Edited January 22, 2014 by |Velocity|

[Clockwork_werewolf]

Thanks Silver chain and Nholzric for providing what is most important if we are arguing numbers which is DATA!

Silvers tests are helpful and should be a warning against using too many nukes on a small ship (I'm guessing that one is about 50 tons?) in a high starting orbit. I would say that I would expect the numbers to be different with larger ships and lower starting orbits. My guess is that your craft doesn't even get to half the starting mass of Nholzrics graphs so although VERY useful data it doesn't answer the debate.

This being said delta V equations are nothing to do with my reasons 1,2,3,5,7 and only a little to do with 6.

Oh and someone else hit on another reason, which is landing gear. With two side nukes you can put on reasonable landing gear.

Oh also I ALWAYS try and return my Kerbals from everywhere and never leave them stranded. I have done Duna and back with under 50 tons but I think EVE and back would be impossible with probably under 100 tons.