Long manuver nodes

[Kev1n8088]

So, I've been trying to make an extremely efficient probe. The issue is, the TWR is insanely low (0.01 or worse), so most of my burns would have to be hours long. I would prefer to do a countinuous burn to the target, and then burn retrograde at the half mark, sort of like the types of burn in "The Martian". Is there a good mod that can help me plan such a burn? 

[Bej Kerman]

There's no mods I know of that can help you with this. You can try creating multiple maneuver nodes to simulate a continuous burn, although you'll be creating nodes for a while. PersistentThrust and KSP Interstellar Extended have engines that can burn for a very long time, but no continuous thrust nodes. You'll have to wait until KSP 2 for this, or ask a modder in addon suggestions.

[Kev1n8088]

Thanks for the help anyway!

[RoninFrog]

I think it was @Laie who did something like this with like a thousand maneuver nodes.  Let's see if he has any advice.

[Laie]

13 hours ago, RoninFrog said:

I think it was @Laie who did something like this with like a thousand maneuver nodes. 

That would be this:

On 6/16/2020 at 2:20 AM, Kev1n8088 said:

I would prefer to do a countinuous burn to the target, and then burn retrograde at the half mark, sort of like the types of burn in "The Martian".

None that I'm aware of.

However, in first approximation you can get to your destination by pointing. Hold on, this reminds me of something...

Quote

‘How do you navigate this thing?’
‘Point.’
‘Point?’
‘Get to the general volume and then point in the right direction.'
'Secret is plenty of power. Delicate finessing of delta-V is sign you haven’t really got enough power.’
‘You can do a lot by just pointing.'
'If you’ve got enough power.’
‘Though sometimes you have to sort of allow a bit for deflection.'
'That’s a technical term.’

-- Ian Banks, The Algebraist

0.01g is plenty acceleration for moving between the planets. Going to Duna should take something like 50 - 100 hours, perhaps? Just a guess, but I fully expect it to be in that ballpark. So, just point for where you expect Duna to be in a few days' time and go for it. Nevermind if you're not exactly on target, you can fix it by the time you get there.

Question is, do you have enough propellant to run the engines for a few days?

The other problem is leaving Kerbin in the first place. The easy method is to have a more powerful booster to get you on your way; the more complicated method is the one pictured above. Sufficiently educated people could probably solve it by maths alone, but I had to resort to brute force: I wrote a kRPC script to plot lots and lots of maneuver nodes.

That's easy and fast at first, but gets progressively worse with the number of nodes. I got the first 100 nodes in five seconds, 50 seconds for the next hundred, 3 minutes for another hundred nodes. kOS may be faster, though I doubt it.

That spiral represents a constant 0.4m/s² acceleration, by the way.

With your vessel being even slower, it may be no longer worthwhile to time the start of the burn. Just get into a sufficiently high orbit around Kerbin, with a period of ten days or so, and then... point.

[wumpus]

On 6/15/2020 at 8:20 PM, Kev1n8088 said:

So, I've been trying to make an extremely efficient probe. The issue is, the TWR is insanely low (0.01 or worse), so most of my burns would have to be hours long. I would prefer to do a countinuous burn to the target, and then burn retrograde at the half mark, sort of like the types of burn in "The Martian". Is there a good mod that can help me plan such a burn? 

First, that's not necessarily efficient.  For a trip from Kerbol to Duna, you would want to Pe kick [Mangalyaan manuever] from low Kerbol orbit to nearly escape velocity (900m/s), then burn the last (~100m/s) in roughly one last orbital pass (you might have to raise your orbit for the last pass).  Killing your velocity at Duna might take a long time, but you certainly shouldn't be burning (either way) at the half way mark.

If you are using ions, then you will likely be stuck with continous burns, but still you will stop far before the half-way point.  The halfway flip and burn is the hallmark of torchships, which are the antithesis of efficiency but as fast as possible.

Kerbal alarm clock is probably the most important mod you will need, and I'd augment it by using multiple fuel tanks set up to only use a set amount of fuel (you'd need to calculate the delta-v you want and pump that much fuel into the tanks set to supply fuel).  Then set physical warp to maximum and wait for your alarm clock to ding.  Note that this works better with the ion/continous burn.  Multiple pe kicks are going to be even more boring.  KSP doesn't really want to reward efficiency, even though that appears to be an overall goal...

[Kev1n8088]

19 hours ago, wumpus said:

If you are using ions, then you will likely be stuck with continous burns, but still you will stop far before the half-way point.  The halfway flip and burn is the hallmark of torchships, which are the antithesis of efficiency but as fast as possible.

 KSP doesn't really want to reward efficiency, even though that appears to be an overall goal...

1. Yep, I know the halfway flip is inefficient and all, since you would never need so much speed. Although I do have Karbonite+, soo..... TORCHSHIPS IT IS! lol

2. Yeah, I realize that. Even a burn a couple of minutes long is inaccurate by a dozen or so meters per second at best. The "encouraged" TWR of ships in KSP is quite high, even in orbit. Like, most people would rarely purposefully build ships with a TWR below 0.2 if they could help it, even though most ships IRL have incredibly low TWRs. The apollo CSM had a TWR of just over 0.1, and lots of ion probes have TWRs lower than 0.001