Is there any reason to not use nukes for interplanetary anything?

[Technical Ben]

No, for interstellar I don't want TWR of more than 1... I generally want 0.2 to 0.10 for not too long burns (3k+ DV burn). I can get by on 0.05 at times (30mins to 60 mins, at perhaps 2x or 4x timewarp).

So, is the nuke the best? I don't see better DV for any other craft.

For launch? Well no, I don't use nukes... ever. I only use them on landers as I have some very special sub 30 part land/tug designs which allow me to max out transfer stage payload size (I can take things other than extra engines/landing stages).

[Sirrobert]

Not useless at all!

I have burns of an hour or more. (See the tutorial in my sig,)

All I need is enough thrust to blow out a birthday candle and enough fuel to do it for an hour and a half!

Right... Most of us don't actually want to babysit a manouver node for 90 minutes.

Really, there is only 1 thing I learned from this topic. There are people here that like watching a number tick down very slowly for 30 minutes. Well, have fun

[Brainlord Mesomorph]

Right... Most of us don't actually want to babysit a manouver node for 90 minutes.

Really, there is only 1 thing I learned from this topic. There are people here that like watching a number tick down very slowly for 30 minutes. Well, have fun

Well, that's not the point.

The point is getting a massive amounts of "payload" to where its going for a lot less "pay."

Granted, long burns are not the most exciting part of my KSP experience, neither are the endless hours the VAB, or the countless laps back and forth to LKO.

What is fun is solving the engineering problem. What is fun is arriving in the orbit of Jool with enough fuel will to do something when you get there. Like circumnavigating Laythee in a flying rover. Or several landings on Tylo.

Take my MegaTanker: 360 tons of space craft powered by four nuclear thrusters. TWR of around 0.06. My guess is it will require an hour-long burn even after perigee kicking. But it arrives in the orbit of Jool with over 200 tons of fuel, and it costs $500,000. Including launching it to orbit.

Now that’s fun!

Also I have a method for long burns: I keep one eye on the screen while I putter about doing light housework. It makes me feel better about wasting a day playing KSP if I get the laundry or dishes done.

Edited February 16, 2015 by Brainlord Mesomorph

[Superfluous J]

Granted, long burns are not the most exciting part of my KSP experience, neither are the endless hours the VAB

Actually that's some of the best fun for me

But you have a point about incessant launches to LKO. Each of those 10-minute trips I can cut out is worth 30 in the VAB in my opinion.

Also I have a method for long burns: I keep one eye on the screen while I putter about doing light housework. It makes me feel better about wasting a day playing KSP if I get the laundry or dishes done.

This is even easier to do now in stock with the "hold prograde" or "hold maneuver" markers. I hear Mechjeb had this already but I never played with it. It seemed to be among the more reasonable things for the game to do for you and am glad it's now stock. I've successfully unloaded and loaded the dishwasher during a Moho insertion burn

[cantab]

Right... Most of us don't actually want to babysit a manouver node for 90 minutes.

Really, there is only 1 thing I learned from this topic. There are people here that like watching a number tick down very slowly for 30 minutes. Well, have fun

Well you don't watch the number tick down. You stick a TV show on and keep half an eye on KSP, occasionally hitting a key or clicking something.

[Technical Ben]

My current attempt at stock interstellar gives me a 2 hour burn time with 4 nukes and ~12kDV and 0.05 TWR (until I ditch a fuel tank or two then it's 0.07). So I'd hate to do that on ion (would need 1000+ xenon tanks I'd guess! ).

Edited February 16, 2015 by Technical Ben

[Space Peanut]

cheers, will give structural fuselage it a go next time i load up the game. Had a terrible experience with an incredibly wobbly four nukes docked to the bottom of a big orange tank.

Because it was such a wobble-fest I had to be patient and do a burn to Jool at 1x speed... got bored and left the room to get a drink and came back to find the rocket De-orbiting!!!

[Rosco P. Coltrane]

Actually that's some of the best fun for me

But you have a point about incessant launches to LKO. Each of those 10-minute trips I can cut out is worth 30 in the VAB in my opinion.

This is even easier to do now in stock with the "hold prograde" or "hold maneuver" markers. I hear Mechjeb had this already but I never played with it. It seemed to be among the more reasonable things for the game to do for you and am glad it's now stock. I've successfully unloaded and loaded the dishwasher during a Moho insertion burn

Yes, MJ has that and also has a maneuver node executor that will do everything. So for the married guy, it's a lifesaver because it keeps the wife happy.

[MarvinKitFox]

... I had to be patient and do a burn to Jool at 1x speed... got bored and left the room to get a drink and came back to find the rocket De-orbiting!!!

Do you want a semi-realistic space sim, or do you want an adrenaline-overload arcade game?

Complaining about a 20 minute (4-minute under timewarp) burn!!!

We should make you do a real life ION engine burn, live!

3 months of waiting for the burn to complete would teach you what a slow burn is!

[panzer1b]

About burn times, ive personally found 1 nuke to be adequate for 20 tons. Its just enough to not require those crazy long burn times, but is as close to max efficiency i can deal with. Making a good ening for a 100-200t frigate is a bigges problem, but ive found 6 engine cluster on a 3.5m tank to work well. 6 nukes is 120t, with 12 engines being plenty for a 200t ship.

Now as for ions, i may be patient, but in not THAT patient. Id really like some stock ions that are a larger scale (such as 2.5m cluster or so). This would give us a capital ship (or large SSTO) engine, which has the ion ISP, has enough thrust to move say 20-30t at a reasonable rate, and not require absurd part counts. Then ofc we would need xenon tanks to match, but i think thatd be a minor issue.

Edited February 17, 2015 by panzer1b

[Technical Ben]

Currently testing a 2 hour burn with 15k (at an estimate) DV for a trial interplanetary craft using 10 nukes. Trial, as the game is crashing if I try to use a solar system mod... so hope I can get it working one day.

[Sirrobert]

Well, that's not the point.

The point is getting a massive amounts of "payload" to where its going for a lot less "pay."

Granted, long burns are not the most exciting part of my KSP experience, neither are the endless hours the VAB, or the countless laps back and forth to LKO.

What is fun is solving the engineering problem. What is fun is arriving in the orbit of Jool with enough fuel will to do something when you get there. Like circumnavigating Laythee in a flying rover. Or several landings on Tylo.

Take my MegaTanker: 360 tons of space craft powered by four nuclear thrusters. TWR of around 0.06. My guess is it will require an hour-long burn even after perigee kicking. But it arrives in the orbit of Jool with over 200 tons of fuel, and it costs $500,000. Including launching it to orbit.

Now that’s fun!

Also I have a method for long burns: I keep one eye on the screen while I putter about doing light housework. It makes me feel better about wasting a day playing KSP if I get the laundry or dishes done.

It actually IS the point.

The question was: 'is there any reason not to use nukes...'

The awnser: Yes, if you don't want to sit through super long burns, there are other engines that are better than NERVAs.

Please stop trying to argue your perception of fun as fact. Fine, for your specific desires, nukes are best.

Personally, I love buidling things. Those countless hours in the VAB, and docking stuf tougether, are my perception of fun in this game. I don't care if I need to spend a little more to get my stuf to it's destination. It's not like it's hard to get funds in this game

[Starwhip]

One word: Sanity.

You want to sit through a long burn, go ahead!

Another reason, though, is that long burns are inaccurate. A higher TWR gives you a better Delta-V expenditure, AND is better on your real-life time.

[Laie]

A higher TWR gives you a better Delta-V expenditure

Is that how it's called? But IMO, that's not an argument against nukes per se: the losses at TWR=0.2 (well doable with nukes) are negligible, on the order of 1%. However, it becomes progressively worse -- if you start saving on the heavy nukes, maybe even going to the extreme of equipping even the heaviest ship with a single engine, your transfer burn will be so inefficient that you end up burning more fuel, not less.

[problemecium]

Aside from impatience, there is another reason: very small probes. A tiny probe (less than a ton) can be moved around with ion engines without too much frustration, and those have triple the Isp of LV-Ns. For slightly larger craft up to about 2 tons, the Rockomax 24-77 can actually provide more delta-V due to its very small mass. Sad that this will probably be nerfed in 1.0, but at least it works for now ^^

[Montag]

I did three Minmus exploration contracts in one go with a manned Mk1 capsule, 4 solar panels, 1 battery circular battery, 1 parachute, 4 landing struts 1 ion engine with 4 fuel tanks. I had crazy 7000 dV in Minmus orbit. I had plenty of thrust and just had to watch the time of Minmus day to make sure I would not run out of power. I could not continuously run at full tilt.

edit: To clarify, the upper stag had the ion engine. Chemical engines got the upper stage to Minmus orbit.

[Renegrade]

the Rockomax 24-77 can actually provide more delta-V due to its very small mass. Sad that this will probably be nerfed in 1.0, but at least it works for now ^^

I think you mean 48-7S here.

I used to make that mistake too (although I called them the 24-7S and the 48-77. Really clear names, eh?)

[wasmic]

If you're only going to Duna or something, not a lot of Delta-V is needed (~1700 m/s for the orbiter if doing Apollo style), so the extra weight of the nukes might actually be more of a hindrance than the increased Isp is a gain. For anything further than Duna or Eve, though, you'll want to use nukes in all circumstances.

[SpaceHips]

(or a cluster of them)

You don't understand efficiency very well, do you?

The most of them you should ever need is two, any more is a waste.

The point of a NERVA engine is to be as efficient as possible, and if you're dragging extra mass in the form of more engines around with you, then you're counteracting that.

[Laie]

The most of them you should ever need is two, any more is a waste.

The point of a NERVA engine is to be as efficient as possible, and if you're dragging extra mass in the form of more engines around with you, then you're counteracting that.

A common fallacy. A very low TWR will cost you more than only time. Just compare the delta-V spent to what it should have been according to the node.

[Superfluous J]

You don't understand efficiency very well, do you?

The most of them you should ever need is two, any more is a waste.

The point of a NERVA engine is to be as efficient as possible, and if you're dragging extra mass in the form of more engines around with you, then you're counteracting that.

If 2 nukes is efficient for (say) 100 tons, 4 is efficient for 200 tons. 2 is not a magic number. Either it's 1 (because you can't go smaller than that) or the number is fluid.

I personally add a 2nd, 3rd, 4th, etc LV-N and check what KER says. If it doesn't look like I'm sacrificing too much dV for the added TWR, I go for it. If it doesn't seem worth it, I don't.

[-Velocity-]

A common fallacy. A very low TWR will cost you more than only time. Just compare the delta-V spent to what it should have been according to the node.

Most of the time you can plan ahead and break your nodes into multiple separate burns that all occur at the optimal point (especially if it's a Hohman transfer) and this no longer applies.

Though I think that the people who never put more than like two NTRs on their interplanetary ships are causing themselves a lot of hassle for very minimal gain. You don't lose a lot of delta-V by adding more, and you greatly reduce the tedium of very long burns. I've built interplanetary ships that weigh in excess of 1000 tons before, do you really want a ship that accelerates at only 12 cm/s^2?!

Edited February 18, 2015 by |Velocity|

[Laie]

A very low TWR will cost you more than only time.

Most of the time you can plan ahead and break your nodes into multiple separate burns that all occur at the optimal point (especially if it's a Hohman transfer) and this no longer applies.

Try as I might, I can only split the first 900m/s or so. If you can divvy the entire transfer into small chunks, I'd like to know how you do it.

[Technical Ben]

As said, I scale up and ditch Nukes with fuel tanks to keep a twr of around 0.20 to 0.10 or at least 0.05 when wanting a LOT of DV. I'll have to run through my current biggest ships, but they have around 20k dv... ok, I might be building them too big!

[tater]

More nukes is a mostly nod to the gameplay problem of tedious, long burns (or places where thrust is actually desirable like circularizing, as the burn time is limited by impending reentry). Ions cannot be compared to real ions at all, as they need constant acceleration trajectories in RL

Modern, real life NTR designs usually have multiple engines, though this is partially a nod to safety through redundancy I think.