[20/11/2014][0.25] FTmN Atomic Rockets

[Kommitz]

I haven't used Mission Controller so I can't say how well the costs are balanced compared with other parts. It is supposed to be expensive though, nuclear reactors are not cheap to build If I were you I'd just edit the .cfg with that in mind.

[wasmic]

So, kommitz, how is the FtMn-100 coming along? And are you still working on that other pack you had planned?

[NathanKell]

Sounds about right. In MCE, NTRs cost 4x what they "should" if they were non-nuclear of the same Isp. The NovaPunch NERVA is ~250k, and it has a slightly lower Isp.

Maybe I should change the multiplier to 2x, though, so they're not quite so dear.

[Kommitz]

So, kommitz, how is the FtMn-100 coming along? And are you still working on that other pack you had planned?

I post in my Work in progress thread more often.

The short of it is that I'm just diversifying the FTmN pack a bit by including a couple of similar-but-different styles to the engines. Here's what the 'FTmN' 160 should be looking like:

[Darth Lazarus]

oh my f***ing Kod !

i was looking for nuclear engines for my planned interplanetary mission, cause teh stock nerva is way to small ... and then i found this here. my heart jumped, now i can go to duna or even further with my planned vessel without using to much mod parts and still with cool and awesome looking engines.

you are my hero Kommitz!

[zakkpaz]

I haven't seen anything in the comments about this. are the engines supposed to keep firing for a bit after you throttle them down?

[Mihara]

I can't say if they're supposed to, but I can confirm they definitely do. I'm not sure if they're actually producing any thrust in this state, but this is kind of annoying.

[MOARdV]

I haven't seen anything in the comments about this. are the engines supposed to keep firing for a bit after you throttle them down?

I'm not the only one seeing that, then? I thought one of the plugins I added recently had messed something up. I swear they weren't behaving that way previously, but it's been a while since I used a nuclear engine on anything, since I'm mostly doing orbital and Mun/Minmus flights these days.

[Gaius]

They're definitely supposed to -- if you check the config files, e.g. from the new FTmN 280, you'll see:

        engineAccelerationSpeed = 2.5
        engineDecelerationSpeed = 2.0 
        useEngineResponseTime = true

So, yes, it takes 2.5 seconds for them power up, and 2.0 seconds for them to power down, if I'm understanding these parameters correctly.

[Kommitz]

It's a stock feature in the stock engine module that I activated!

I did it on purpose; reactors are supposed to take some time to heat up and cool down but I'll probably remove it from the standard config files when I update next time. (Although if you check the thrust when it's decelerating, the majority of the lag is at very tiny thrust so it shouldn't do much to mess with your burns).

You can easily delete this out of the engine module:

        engineAccelerationSpeed = 2.5
        engineDecelerationSpeed = 2.0 
        useEngineResponseTime = true

If it's really getting on your nerves.

I will put the feature back in my alternative fuel config when I've done the parts for that, as for it I'm working towards making the engines function a bit more like real nuclear rockets. Eventual goal of having a plugin to handle heating up, cooling down, multiple fuels and power generation loops all in a single part.

[Gaius]

I kinda like the effect, but I'm not sure if it's realistic. I know it must take time to heat up and cool down, but you should be able to stop pumping propellant instantly, no matter how slowly the engine cools, no?

[Kommitz]

Technically you should be able to stop pumping the propellant instantly, but the results of that are where a plugin would come in handy.

The propellant in a nuclear rocket is also the coolant and the engine can operate at the temperature that it does because the waste heat is dumped out the back. If you cut off the propellant flow before the reactor had cooled down I'd imagine the results would not be good.

I was on wikipedia last night looking at the relevant page about the power output of these things. The FTmN 280 should have a reactor core that can put out around 1200MW of thermal energy, which isn't something you just want to stop the coolant flow to imo

But anyway I'll revert the .cfgs back to how they were before when I finish the last engine & upload the pack again. I've taken the acceleration/deceleration thing out for animation reasons now.

Edited October 9, 2013 by Kommitz

[MOARdV]

It's a stock feature in the stock engine module that I activated!

I did it on purpose

In that case, I won't worry about it. And, you're right. Most of the power down sequence is at near-idle, and it hasn't affected my flights, AFAICT.

[Gaius]

Technically you should be able to stop pumping the propellant instantly, but the results of that are where a plugin would come in handy.

The propellant in a nuclear rocket is also the coolant and the engine can operate at the temperature that it does because the waste heat is dumped out the back. If you cut off the propellant flow before the reactor had cooled down I'd imagine the results would not be good.

Oh ho ho! Good point! I hadn't even thought of that. Obviously, I am not qualified to operate a nuclear reactor...

[Captain Sierra]

One thing I noticed is the FTmN 280 seems quite overpowered when compared to the alternatives. It is awesome to have such a powerful nuke, I do enjoy the speed at which I can execute interplanetary transfers, but it feels almost uberpowerful by nuke standards/

[p1t1o]

I kinda like the effect, but I'm not sure if it's realistic. I know it must take time to heat up and cool down, but you should be able to stop pumping propellant instantly, no matter how slowly the engine cools, no?

Not necessarily, propellant must be pumped under very high pressure and often the pumps are powered by the combustion in the rocket, for example, for this reason the F1 engines on the SaturnV could not be throttled. There may also be problems with closing a high pressure, high flow rate system too abruptly. It is the liquid engines here that spoil us, they arn't supposed to be this easy to turn off/on - not that I would have it any other way in KSP however.

[ROFLCopter64bit]

Not necessarily, propellant must be pumped under very high pressure and often the pumps are powered by the combustion in the rocket, for example, for this reason the F1 engines on the SaturnV could not be throttled. There may also be problems with closing a high pressure, high flow rate system too abruptly. It is the liquid engines here that spoil us, they arn't supposed to be this easy to turn off/on - not that I would have it any other way in KSP however.

Nuke engines aren't actually supposed to use liquid fuel, it's just a placeholder for the resources system that will come up in maybe 0.23 (The version numbers are getting big), so I guess it's just doing that for some realism with nuke engines.

[Kommitz]

One thing I noticed is the FTmN 280 seems quite overpowered when compared to the alternatives. It is awesome to have such a powerful nuke, I do enjoy the speed at which I can execute interplanetary transfers, but it feels almost uberpowerful by nuke standards/

Hate to break the illusion, but it's balanced almost identically to a bunch of LV-Ns working together

[Ratzap]

Hate to break the illusion, but it's balanced almost identically to a bunch of LV-Ns working together

Compared to the radial nuke from the Korda pack it's kinda flabby actually but generally it fits in with nuclear options available if somewhat to the heavier end of things. OP or unbalanced? No, definitely not. There are quite a few nukes around now and it wouldn't be hard to create a spreadsheet or graph of TWR for them. These would not be at the top.

[Captain Sierra]

Doing some quick math, still a little on the strong side.

[regex]

Doing some quick math, still a little on the strong side.

Please show your work.

[Gaius]

Doing some quick math, still a little on the strong side.

Stock LV-N thrust to weight ratio: 26.7

KSPX LV-NB thrust to weight ratio: 30

Fatman 280 thrust to weight ratio: 28.7

Captain Sierra: bad at math

It really should have a bit better t/w ratio -- if you can't make your bigger rocket have a better t/w ratio, there's no reason to use it, you'd use a cluster of smaller engines instead. For its size, it's probably a little on the weak side...

[sojourner]

It has higher ISP than the LV-Ns, plus reduced part count. Works for me.

It's also down right sexier to look at than a bunch of LV-Ns.

[Kommitz]

I rebalanced all the .configs for the next release, I think a bit of a buff in TWR for the larger engines seems fair.

Also got started on the colours for the middle engine (but currently I'm trimming a few more polygons off it):

[LameLefty]

Thanks for the updates, Kommitz. Your engines are indispensable to me and I love pretty much everything about them. And the artwork is perfect.