best way to add dv?

[shand]

I find keeping TWR between 1.4 and 2.2 (stage full to burn out) is perfect. if you overpower your rocket a tiny bit (TWR 2 on the pad) you can throttle back as you go up.

as for increasing deltaV generally - nerva, as few as you can while still being able to carry out the acceleration you need.

Nerva is only the best if you are using more then 5 tonnes of fuel (or was it 3.5). less then that, use the small rocket or perhaps the aerospike depending.

[numerobis]

The absolute best engine is the turbojet, but it is somewhat limited by needing an oxygen atmosphere and all that. Next-best is the ion engine, limited by being low thrust. So for general deep-space purposes, the LV-N is very nice.

The ideal profile, if engines were weightless, would maintain terminal velocity all the way to space with the maximum Isp. At low altitude, a TWR just over 2.0 achieves that (because you're going slowly, terminal velocity doesn't grow very fast). But because engines have mass, it turns out to be better to be a bit below 2 at the beginning of your first and second stage, and slightly above at the end of the first stage -- and you have to compromise on the Isp. This tradeoff is an inexact science, and predictably people therefore have vigorous arguments over the best way to do it.

One thing that's fun on liftoff is to use two or three of the small radial engines to improve your TWR at the beginning of the first stage, then turn them off when the main (and more efficient) engines get good enough, then back on at the second stage, off at the end of that stage, then use them as the main engines for your third stage. This repeated use lets you shave a few hundred kg off engine mass at launch.

[UmbralRaptor]

I don't mean exactly 1.0 TWR either. More like 1.5 is appropriate.

A 50% difference is rather large...

I have tried with every other combo out there. If you insist on burning liquid in lower atmo, then you should def be using aero spikes and not not the horribly inefficient main sail engine. Most people use a solid booster stage to get them to thin air before ever lighting up a liquid rocket. In this game, that is passable because everything is free. Adding more fuel is seldom the answer unless your rocket is already way OP already and it has engines on it that are too heavy and costing you payload.

In an ISP sense, I'd argue that "lower atmo" ends somewhere around 2-4 km up. Though drag-wise, it can be considerably higher. Asparagus staging tends to leave me thrust-limited on upper stages, but with headroom on lower ones.

I am constantly putting 30 tons worth of mining equipment in orbit on around 4500ms of fuel and still have fuel left to go to Duna and perform orbital ops when I get there. One orange tank and six boosters can put 20+ tons into orbit if you know what you are doing. No need for all this 4+ orange tank business.

Please post pics and/or .craft files. Getting 20+ tonnes of payload on the equivalent of 1 orange tank worth of fuel, 6 BACC boosters, and some miscellaneous engines seems to imply a payload fraction of 16-19% (Possibly over 25% if you used RT-10s).

[Francesco]

Please post pics and/or .craft files. Getting 20+ tonnes of payload on the equivalent of 1 orange tank worth of fuel, 6 BACC boosters, and some miscellaneous engines seems to imply a payload fraction of 16-19% (Possibly over 25% if you used RT-10s).

I think he means liquid fuel booster, not solid.

WOW people getting all upset. Been playing this game for a while now. Near 1 does not mean exactly one. And no, 2.0 off the pad burning liquid is a massive waste of dV.

---

And yes my first reply perhaps wasn't worded clearly enough. Next time read what is there and not what you want to be there. I understand the youth are indoctrinated to ignore words such as Nearly, Virtually, Almost...Etc.

nobody got upset, but since we are on a public forum, and given that novice players may be mislead by incorrect or incomplete information, correction is in order.

we didn't ignore your words, what matters is the context: when talking about takeoff TWR, saying "near 1" is a lot different than saying "near 1.5".

Edited May 3, 2013 by Francesco

[Psycho0124]

Stop using terrible engines for lifting is one thing. I cringe every time I see a main sail. Use aerospike clusters for lifting.

I am constantly putting 30 tons worth of mining equipment in orbit on around 4500ms of fuel and still have fuel left to go to Duna and perform orbital ops when I get there. One orange tank and six boosters can put 20+ tons into orbit if you know what you are doing. No need for all this 4+ orange tank business..

20... tons? You're right, for tiny payloads like that, mainsails would be a terrible waste of delta-v. What you fail to realize is that not everyone tinkers with such small payloads. Mainsails are the only (cpu friendly) option for lugging huge loads into space.

185 ton refueling station (I like it full when it reaches orbit). This is my Laythan refueling station.

Jeb seem to really like the view out here:

226 tons with no kethane probes/torpedos loaded. VTOL capable (low grav obviously) Kethane mining/refining ship. I also like this guy full when he reaches orbit. Places to go, kethane to mine, stuff to destroy ya know?

All tanked up and ready to drop back to Kerbin and Oberth out to Laythe to pay Jeb a visit.

Hehe.. Just ignore the mission timers... I was toying with dropping a probe from a very high solar orbit down into Kerbol at ultra-high speed. Forgot to load after all that time acceleration. Is there any way to reset those?

Edited May 3, 2013 by Psycho0124

[Payload]

Close enough for you?

That cluster is 4 aero spikes and one LV-T45 for gimbal.

There are actually 8 boosters on this ship. 4 large and 4 small. I'm 100% positive this would still orbit if I went with 6 large SRB's.

The wings didn't help either. In the launch orientation they are just extra drag. Also my gear were out and I didn't close the intakes either. Noticed after the circulation burn lol. I challenge you to do better with a main sail sir.

I'm not sure approaching 20% is even possible without jet engines. That is pretty close to 16% all conditions nominal. Different strokes for different folks yea?

Payload

Orbit

The rest of them

[shand]

i'm noticing a theme. Payload gets easily offended/self-victimised.

which is a shame, i tend to agree with them - and now they've clarified i do again! though i would reiterate Francesco's last sentence.

Eitherway, launch profile is a side issue here, the main topic is gaining delta v. not what you do with it!

OP i suggest downloading kerbal engineer redux (or mechjeb, but KER is better for delta v readings) that way you can fiddle and see.

but yes; add fuel sensibly; use high ISP engines appropriate for the mass of your craft; and reduce the mass of your craft.

And finally. KISS - the benifits of complex staging are THERE, but if you are struggling i suggest cutting back to basics. payload, upper, lower with SRB on the side. easily get 50tonnes of payload up in that fashion.

[Psycho0124]

..can put 20+ tons into orbit if you know what you are doing.

Are you touting your ascent flying skills... while using mech-jeb to fly you into orbit?

No need for all this 4+ orange tank business.... ...Not that I am accusing anyone here of that. Just that I am constantly seeing people launching fuel for fuel's sake which is not the way to do it.

Why not? The OP asked for more Delta-V didn't he? Check the Delta V on that station I posted.

Extra fuel adds flexibility and fun. It's also a fun challenge to get large quantities into orbit!

Also, with an orbital payload of only 14 tons, your space-plane was only 6% as massive as my Cruiser.

Edited May 3, 2013 by Psycho0124

[magnemoe]

The absolute best engine is the turbojet, but it is somewhat limited by needing an oxygen atmosphere and all that. Next-best is the ion engine, limited by being low thrust. So for general deep-space purposes, the LV-N is very nice.

The ideal profile, if engines were weightless, would maintain terminal velocity all the way to space with the maximum Isp. At low altitude, a TWR just over 2.0 achieves that (because you're going slowly, terminal velocity doesn't grow very fast). But because engines have mass, it turns out to be better to be a bit below 2 at the beginning of your first and second stage, and slightly above at the end of the first stage -- and you have to compromise on the Isp. This tradeoff is an inexact science, and predictably people therefore have vigorous arguments over the best way to do it.

One thing that's fun on liftoff is to use two or three of the small radial engines to improve your TWR at the beginning of the first stage, then turn them off when the main (and more efficient) engines get good enough, then back on at the second stage, off at the end of that stage, then use them as the main engines for your third stage. This repeated use lets you shave a few hundred kg off engine mass at launch.

The trashcan solid boosters are nice for increasing twr at liftoff.

And yes using turbojets as first stage work very well for small to medium rockets. feed them from an central fuel tank.

If you send off something with nuclear engines and the nuclear stage has decent trust its an idea to use the nuclear upper stage as center of the asparagus, for an small probe you might want to use an mainsail or jet first stage then use two 1.25 meter boosters with T30 with fuel lines to the nerva. The nuclear engine improve overall isp.

For an large mothership, put dropable booster engines on the ship to increase TWR you use the mothership as an second stage, it arrives with little fuel left so you have to refuel in orbit but its an easy way to get 200 ton or more motherships to orbit.

[Payload]

i'm noticing a theme. Payload gets easily offended/self-victimised.

I have to keep remembering that everyone on the internet automatically thinks you are always lying.

It's quite an odd concept to me. I just try what I read before I make any presumptions personally. I'm not personally offended. It's just a strange cultural phenomena. No worries chaps, I am not a gentile snow flake. Newzon seemed to enjoy the ride so much he forgot to do anything. Maybe he had to visit the water closet.

Psycho0124-Are you touting your ascent flying skills... while using mech-jeb to fly you into orbit?

Flying skills? No. Knowledge of what is wasteful perhaps... I remember doing this long before mech jeb even existed if that gets me out of the "ZOMG MJ is just about pushing buttons" Zone of insults. You still have to understand what the buttons do and I actually fly most of that profile without the use of MJ. He seems to not care which way my wings are oriented and that leads to early re-entry.

[ThatBum]

I feel this is a case of the old engineer attitude of "I am right and you are wrong and nothing in the universe can change that, ha ha ha!" Many people here are at fault because of this, including me sometimes. Let's just agree that everyone has their own way of doing things, and getting something large to orbit is an accomplishment in itself. If it works, you're doing it right. This is KSP after all.

Edited May 3, 2013 by ThatBum

[Psycho0124]

Flying skills? No. Knowledge of what is wasteful perhaps...

Are you.. touting your knowledge of wastefulness and efficiency... in a sandbox game where cost is irrelevant?

Oh, you're pretending that fuel and equipment costs have an impact an imagined budget and have set a goal for yourself of keeping that impact to a minimum and accomplishing missions! Neat!

I think you might have forgotten that not everyone shares your goal of cost efficiency (or is even aware of it).

You still have to understand what the buttons do and I actually fly most of that profile without the use of MJ.

It all looks pretty self-explainatory: "Prevent overheats, auto-stage, corrective steering, prevent flame-out, limit to terminal velocity, Ascent path editor". It looks like lots of 'win' buttons checked off in your screens to me but meh, who am I to judge how someone else plays right? It's your game!

Edited May 3, 2013 by Psycho0124

[Payload]

Are you.. touting your knowledge of wastefulness and efficiency... in a sandbox game where cost is irrelevant?

Oh, you're pretending that fuel and equipment costs have an impact an imagined budget and have set a goal for yourself of keeping that impact to a minimum and accomplishing missions! Neat!

I think you might have forgotten that not everyone shares your goal of cost efficiency (or is even aware of it).

It all looks pretty self-explainatory: "Prevent overheats, auto-stage, corrective steering, prevent flame-out, limit to terminal velocity, Ascent path editor". It looks like lots of 'win' buttons checked off in your screens to me but meh, who am I to judge how someone else plays right? It's your game!

You really seem to not understand what the point of my statements are at all. I'll bet the dV he needs is already in his ship if made more sensible choices. It's not about the size of the ship. The same concepts still apply. The inclusion of mechjeb is always more informative than just trying to explain what you are talking about. The information is there. All of the things discussed here by everyone will help for sure. I don't understand the need to be so combative.

[Direk]

20... tons? You're right, for tiny payloads like that, mainsails would be a terrible waste of delta-v. What you fail to realize is that not everyone tinkers with such small payloads. Mainsails are the only (cpu friendly) option for lugging huge loads into space.

185 ton refueling station (I like it full when it reaches orbit). This is my Laythan refueling station.

Jeb seem to really like the view out here:

226 tons with no kethane probes/torpedos loaded. VTOL capable (low grav obviously) Kethane mining/refining ship. I also like this guy full when he reaches orbit. Places to go, kethane to mine, stuff to destroy ya know?

All tanked up and ready to drop back to Kerbin and Oberth out to Laythe to pay Jeb a visit.

Hehe.. Just ignore the mission timers... I was toying with dropping a probe from a very high solar orbit down into Kerbol at ultra-high speed. Forgot to load after all that time acceleration. Is there any way to reset those?

Very cool Kethane mining/refining ship Psycho0124 . I was hoping you would be willing to share the .craft file, as I would have a use for a ship like that.

[foamyesque]

the tile saya it all. what is the most size efficent way to add dv to your rocket?

A lot of people are going to tell you a lot of nonsense, but the best way is to remove as much weight as you possibly can. Everything else is something you do after you've done that, because they're all strictly inferior options.

[Psycho0124]

You really seem to not understand what the point of my statements are at all.

No, it all seems pretty self-explanatory:

Stop using terrible engines for lifting is one thing. I cringe every time I see a main sail. Use aerospike clusters for lifting.

(Categorical 'my way or the highway' statement)

No need for all this 4+ orange tank business.

(another 'my way or the highway' statement)

Knowledge of what is wasteful perhaps..

This one I supposed I don't follow. Wasteful. How do you define waste in this case? Do you consider an asparagus staged liquid booster, dropped when emptied a few seconds after launch, to be waste? What constitutes waste in a lifter by your definition?

The inclusion of mechjeb is always more informative than just trying to explain what you are talking about. The information is there.

Kerbal Engineer mod provides lots of info too, sans the auto-pilot functions. I installed it this evening to see how much all my cringe-inducing, orange-tanked monstrosities weigh.

I don't understand the need to be so combative.

Sorry, I have a compulsive debate problem. It kicks into high gear when I see someone making categorical claims about subjective subjects.

[UmbralRaptor]

Close enough for you?

Absolutely. If I'm counting correctly, that's an 18.5 tonne payload on a 110.01 tonne launcher. You also exposed an inaccuracy in my system, since I tend to treat payloads as entirely inert, while this supplied the last bit of ÃŽâ€V to reach orbit.

I'm afraid that my Mainsail-based response tops out at ~14% payload. And I've never bothered to fix that it potentially kills a Kerbal each launch.

You finally got me to stop dinking around so much and set up a (hilariously overbuilt) Moho orbiter.

in-VAB:

In-orbit. Then I accidentally throttled up

Still some fuel.

...

Just a 37.1 tonne test payload. MJ is used as a ?V recorder due to curiosity.

In-VAB:

Orbit established:

Fuel:

Hand-flown below 4.4 km/s? o_O

Edited May 3, 2013 by UmbralRaptor
Let me use my unicode!

[ThatBum]

The rest of my rocket:

[Payload]

Absolutely. If I'm counting correctly, that's an 18.5 tonne payload on a 110.01 tonne launcher. You also exposed an inaccuracy in my system, since I tend to treat payloads as entirely inert, while this supplied the last bit of ÃŽâ€V to reach orbit.

I'm afraid that my Mainsail-based response tops out at ~14% payload. And I've never bothered to fix that it potentially kills a Kerbal each launch.

You finally got me to stop dinking around so much and set up a (hilariously overbuilt) Moho orbiter.

in-VAB:

In-orbit. Then I accidentally throttled up

......

Still some fuel.

.......

...

Just a 37.1 tonne test payload. MJ is used as a ?V recorder due to curiosity.

In-VAB:

.............

Orbit established:

...................................

Fuel:

.................................................

Hand-flown below 4.4 km/s? o_O

Awesome! Can I name it?

ThatBum, I always imagine rockets like that falling apart on scene load on the runway. Probably because I'm just crap at making them. Also, those tail sections are looking nice and I considered using them for clustering. They weigh a whole lot more that the structural ex-docking ports. If you can't tell, money is tight over here at Payload Space Industries. Why do you think we are down to launching Newzon Kerbal? Talk about the wrong stuff.

Oh did I forget to mention. That space plane can get to orbit by itself from the runway. So why don't I fly it that way? Because it takes for ever and it's boring.

Jeb and Bob haven't been putting in hard hours on the mun moving all that kethane for nothing.

Edited May 3, 2013 by Payload

[ThatBum]

Oh yeah! I didn't even think about the dummy docking port parts, I'll try using those instead of the aero tail pieces next launch. Still need to get used to all these crazy new parts.

Also it's actually remarkably stable. Rock solid attitude throughout the ascent. The cross struts really improve structural integrity. With that much gimbaling it executes the gravity turn very quickly. I calculated it so the 3rd stage (the one before the nuclear stage) has just enough fuel to get it to 100km, then it's jettisoned and the nuclear stage circularizes, to avoid debris. Actually, it has a little fuel left in case of heavier than usual payloads, but still, not much Dv is wasted.

[Payload]

Seeing just how far I can take this in five minutes. Insert a few OP parts here and there. Like H.O.M.E. radial aero spikes.

73tons start.

31tons to orbit.

I didn't even adjust the flight profile which really should have started quite a bit earlier. Lost tons of dV there.

[RoboRay]

A lot of people are going to tell you a lot of nonsense, but the best way is to remove as much weight as you possibly can. Everything else is something you do after you've done that, because they're all strictly inferior options.

Yep, absolutely. If you're building enormous, heavy spacecraft simply for the sake of having enormous, heavy spacecraft, you've already discarded all pretense of "optimizing" your craft for fuel efficiency and maximum delta-v.

Diminishing returns on added mass are critical in rocketry. Any mass beyond the absolute minimum required for a mission is counterproductive.

Edited May 3, 2013 by RoboRay