Introduction & DeltaV Question

[bobinator133]

Hi, I'm bobinator_133 (as you may have somehow guessed already). I'm entirely new to the forums - don't worry though, I've already read all the important guides. 

Besides the introduction, I'm also here to ask a quick question about DeltaV. Specifically, I've been having a huge amount of trouble actually getting enough of it. The farthest-out mission I can consistently do is a flyby of a Joolian moon - MAYBE an orbit, but that's a one-way trip. Even then, I'm left with next to no fuel, and have had to literally push my rocket (using EVA packs) the rest of the way into Kerbin's atmosphere. Multiple times. And as if all that wasn't bad enough, I have the OUTER PLANETS MOD installed! Any tips to conserve and/or increase DeltaV would be greatly appreciated. Thanks!

[Geonovast]

Welcome aboard!

Without getting into anything specifically with your craft (as we can't see it), here are a couple generic things you can do:

• Reduce parts (therefore mass).  If you don't absolutely have to have it, get rid of it.  I see a lot of new players carry extra parts like large batteries and reaction wheels that just aren't required.
• If you have a lot of fuel tanks, set up the priority to drain them in sets and stage away the empty ones.
• Use more efficient engines.   But be careful with this, depending on the craft you can actually be better off with a slightly less efficient, but lighter, engine.  This is heavily craft dependent and can go either way.
• Reduce the ablator on any heatshields to the minimum you need.  You don't want to run out of ablator, especially if you're returning from Jool, but you probably don't need it all, either.
• If you don't need RCS, you can empty out all the mono-propellant from pods in the VAB.
• And, of course, bring more fuel.  This is probably the hardest solution and a lot of times isn't the best, either.

[Admiral Fluffy]

Welcome @bobinator133! 

To avoid some problems, I would recommend flying probes to the moons, rather than kerballed missions. That way, it doesn't matter if you get them back or not. Try using the terrier or poodle engines, as they have higher efficiency in a vacuum. You can also check the vacuum DeltaV in the VAB/SPH, by clicking the tab that has the dV symbol on it.

[bobinator133]

6 hours ago, Admiral Fluffy said:

I would recommend flying probes to the moons, rather than kerballed missions.

Thanks for the welcome! I've actually already landed four rovers (two for Kerbin's moons and two for Duna and Eve respectively), and I understand vacuum efficiency and how to see DeltaV. This is definitely a good tip, but one I've already figured out. Nonetheless, thank you!

[Vanamonde]

It's largely a conceptual problem. Start with the smallest payload which can do the job you need, then build stages under it until the aggregate has enough dV to perform the full mission. Never add mass to the final stage, because that makes every previous stage less efficient. If you do need to make the final stage larger, it might be advisable to delete everything below it and rebuild that from scratch. 

And welcome to our forum.

[bobinator133]

37 minutes ago, Vanamonde said:

It's largely a conceptual problem. Start with the smallest payload which can do the job you need, then build stages under it until the aggregate has enough dV to perform the full mission. Never add mass to the final stage, because that makes every previous stage less efficient. If you do need to make the final stage larger, it might be advisable to delete everything below it and rebuild that from scratch. 

I think that might work really well! I've just recently learned consistent methods of docking - needless to say, this is far more efficient than a direct ascent on Joolian moons. I'll probably make a (small) lander, then take your advice to create the transfer stage and all the stuff before it.

Matters are complicated thanks to the challenge I'm doing: I set my science gains in the difficulty page to 10%, so I haven't researched any engine stuff farther than the "Heavier Rocketry" node, but I think I can work something out.

Fortunately, it's an even simpler task to create a rescue vehicle for the three guys I left in orbit of Dres for nearly a decade while testing designs. 

[king of nowhere]

the tips i can give are

- use gravity assists to reduce deltaV required.

- send up the largest missions in multiple smaller modules that can be docked in orbit.

ultimately, while you can work on mass and efficiency, to get a high deltaV you need to use a lot of fuel and stages. not much to be done about it.

also, if your problem is the lack of science, you can mine the multiple biomes of mun and minmus for it. though i doubt that's what you want.

[Nazalassa]

Maybe use Xenon engines?

They are incredible in terms of ISP and delta-V

[Maria Sirona]

22 hours ago, Nazalassa said:

Maybe use Xenon engines?

They are incredible in terms of ISP and delta-V

...and horrible in terms of actually being fun. Regardless, welcome to the Forums @bobinator133! Hope you have a great time

[CFYL]

Some of my personal trial-and-error experience.

To save DV

1. An insertion aided by Jool's moons (Layth/Tylo, not the smaller ones) is possibly the easiest gravity assist in stock KSP.

2. To save more DeltaV, your ejection burn can be aided by the Mun, and then perform Kerbin flyby(s) to raise ap to Jool orbit.

IIRC there are dedicated challenges for only burning to Mun capture and then let gravity do the rest of the mission.

To create MOAR DV

1. MOAR BOOSTERS / MOAR ENGINES (not recommended)

2. Apollo style landing? seperate your lander into a landing stage and an ascent stage to dump excess mass on ascent. Very useful for bigger moons.

3. ALWAYS make a very lightweight payload. TWR doesn't matter in orbit, so NEVER use engine clusters for orbital maneuvers. For smaller moons it doesn't matter that much. For bigger moons, the size of Vall or bigger, an ending TWR of 1.2-1.5(local) is good enough for a fine-tuned descent profile. more engines = more dead weight. so use a single, efficient engine for orbital maneuvers. You can actually use the terrier for full-throttle TWR down to 0.05(Kerbin) (or lower, if you have the patience) in Kerbin orbit. Just burn "a bit" longer. (You have to seperate an ejection burn down to several parts with low TWR tho)

some of these are mentioned above by @Geonovast@Admiral Fluffy@Nazalassa and many more

Edited May 19, 2022 by CFYL