lifting heavy payload to orbit

[JtPB]

i was trying to lift the jumbo-64 fuel tank(the heaviest payload possible, 36 tons! even the pre-assembled station core is pretty light relativly to this monster) with a docking tug which consist of:

- a large RCS tank

- a large inline remote control unit

- X200-8 fuel tank with 48-7S engine

- decopuled from the jumbo tank with large decopuling ring, for manuevering into the atmosphere to clean the orbit.

the decopule ring is remaining attached to the tug

i tried to lift this payload with the final staging attempt as described bellow:

stage 1:

asparagus of seven jumbo tanks with skipper engine each, symmetry 2 mode.

a large ASAS unit above the central tank, one BACC SRB attached to each of the peripheral tanks.

stage 2:

X200-32 tank with mainsail engine & large ASAS unit

stage 3:

X200-16 tank with poodle engine

the rest is the payload that described above

the launcher is falling & even dont exit the atmosphere no matter when i yawing to orbit.

i didnt put mainsail at 1st stage because when on full thrust its hard to control the craft.

ideas: i saw that SRB boosters have a nice dV when launched alone(more than the escape velocity of kerbin).

would i use mostly them when launching that heavy payload?

should i put mainsail on the central jumbo tank instead of skipper?

PS: also, if i wanna send a ion glider interplanetary(Eve or Duna), how would i do that?

thx for answering & help

Edited March 7, 2014 by JtPB

[Kasuha]

This is my lifter which I used to deliver orange tank (or some slightly heavier payloads) to orbit. What's below the tank is an orbital tug with enough dv and monopropellant to circularize, deliver the tank to ~1000 km orbit, attach it to orbital station, and return to kerbin. What's on sides are asparagus-connected stages to get the tug and tank out of atmosphere and on suborbital trajectory close enough to circularizing.

Edited March 7, 2014 by Kasuha

[Taki117]

You need more thrust in your 3rd stage, unless you plan to use some of your payload fuel. Generally speaking you want to keep your TWR about 1-2 for your orbital insertion. This will save you some burn time meaning that you don't lose as much vertical altitude per unit of horizontal distance. (Less important in space, but still important) I'd put a skipper, or possibly cluster some LV-909's for that stage. You could also use SRBs to give you an initial boost off the pad, but beyond that they aren't much good at all. You also want to keep your speed at just about or slightly above terminal velocity. Any lower and you are wasting dV fighting gravity, any higher and you are wasting dV fighting air resistance. A pic of the rocket would help in diagnosing any problems. I would also use a Skipper for your second stage, and use a mainsail on your first stage, adding winglets is 4x symmetry around the center stack (Or whatever symmetry works with your initial booster combination)

[Gravitas Shortfall]

If you're aren't opposed to mods, MechJeb will give you helpful stats in the vehicle assembly building, including the thrust/weight ratio for each stage. Very helpful for designing launchers.

Edited March 7, 2014 by Gravitas Shortfall

[Kasuha]

with a docking tug which consist of:

- a large RCS tank

That's way too much monopropellant. It's much more effective to get near your target using engines and only carry/use small amount of monopropellant for actual docking.

- X200-8 fuel tank with 48-7S engine

I suggest nuclear engines. They're heavy but with 40 tons of payload their weight is not that much and they're two times more effective than any other rocket engines.

stage 1:

asparagus of seven jumbo tanks with skipper engine each, symmetry 2 mode.

a large ASAS unit above the central tank, one BACC SRB attached to each of the peripheral tanks.

That should be capable of lifting it to orbit alone.

stage 2:

X200-32 tank with mainsail engine & large ASAS unit

Mainsails are too ineffective, too heavy and with this little fuel they actually make things worse. Get rid of this stage. If anywhere, use mainsails in the first stage.

stage 3:

X200-16 tank with poodle engine

I'd suggest merging this stage with the tug.

[Pecan]

This is my lifter ...

Apart from the central nukes are those T30s you're using Kasuha?

[celem]

It seems you have over staged this to be honest.

The 3rd stage with poodle is probably gutless, poodles are efficient but weak when compared to their weight, they are best as a payload engine rather than a launcher, use them for neatening up orbits and transfers to Kerbin's moons. The only time I would put this into a launcher would be a final stage for a really small payload like a satellite.

The 2nd stage with mainsail on a small tank is going to burn out so fast that its probably actually reducing your overall dV. Sure it does it's part, but the stage below has to lift that beast of an engine, I'd guess you lose more dV from stage 1 than you gain from stage 2, this is an ideal spot for a skipper.

The 1st stage with skippers seems pretty good. I would be tempted to put a mainsail on the centre core though, once it drops those asparagus tanks then you have a skipper lifting a full tank, plus stage 2, plus stage 3, plus payload. Thats a tall order. If a mainsail on the centre core makes the intitial climb unstable then throttle it back a bit, nobody said you have to 100% gun it off the pad.

In general try not to put mainsails above skippers, engines should decrease in power as you go up the rocket as they are moving less weight.

You may also hit issues with the rocket snapping at the large inline SAS modules if you increase the thrust, these are quite weak parts and I try to keep them as high up on the rocket as possible. If they are lower down then they get crushed between the huge dead-weight above and the rampant launcher below.

edit: Kasuha also pointed out the excess RCS, excellent point. Very few craft need the full load of the 2.5m RCS tank. Try emptying half of the monoprop in the VAB, otherwise its just another 4.5tonnes to push up the hill.

Edited March 7, 2014 by celem

[DonLorenzo]

This episode of my RSS series focuses on the launch vehicle I use. It lifts about40tons to LEO. It's in RSS so LEO takes ~9-10km/s meaning that this will put those 30-40tons on a transfer trajectory anywhere in the stock game.

[Kasuha]

Apart from the central nukes are those T30s you're using Kasuha?

They're T45s, if I remember correctly. They're not less efficient and still produce sufficient thrust.

[capi3101]

Alright, OP. I've analyzed your craft from what you've described, and I think I know what problem you're having. Let's go over the analysis.

The payload you described is:

Large RCS (3.4)

Large RCU (0.5)

X200-8 w/ 48-7S (4.5 + .1)

Jumbo 64 (36)

Sr Docking Port (.05)

Total Mass of 44.55 tonnes. I'm not sure about the Docking Port but since it doesn't add a lot of mass, we'll leave it there. Also, if this is something you want to perform independent operations, you might consider adding something in the way of an electrical system, unless you're okay with it become debris while something else (with electricity, presumably) comes along to dock with it.

Now for your stages as listed. You've got a six stage rocket (assuming that "Stage 1" above is actually a four-stage asparagus). With the parts you've described, it breaks down like this:

Rocko / X200-16 / Poodle (0.5 + 9-1 + 2.5), Isp = 270 (12-4) ==> dV=404, TWR=0.39

Rocko / X200-32 /Large ASAS / Mainsail (0.5 + 18-2 + 0.2 + 6), Isp 280 (24.7-8.7) ==> dV=602, TWR=1.88

Rocko / Large ASAS / Skipper / J64 (0.5 + 0.2 + 4 + 36-4) Isp 300 (40.7-8.7) ==> dV=895, TWR=0.543

TT38-Kx2 / Skipperx2 / J64x2 (.05+8+72-8) Isp 300 (80.05 - 16.05) ==> dV=1127, TWR = 0.98

TT38-Kx2/ Skipperx2 / J64x2 (.05+8+72-8) Isp 300 (80.05 - 16.05) ==> dV=757, TWR = 1.17

TT38-Kx2 / Skipperx2 / J64x2 (.05+8+72-8) Isp 300 (80.05 - 16.05) ==> dV=572, TWR = 1.28

Total Delta V = 4,357 m/s

Your TWRs are appalling pretty much the entire way up. If your asparagus is set up correctly, you're going to start falling out of the sky after you've dropped your second set of asparagus boosters. You could kick those off early to light up the Mainsail but then you'd lose almost half of your available delta-V. No ifs ands or buts about it: this ship is not going to space today.

Forgive me for ignoring the SRBs - I see them as extraneous mass. They help you get into the air...which just means that you're going to be up higher when you drop your second set of boosters and start falling out of the sky.

So let's adjust this booster. 44.55 tonnes is actually pretty easy to launch as it turns out. For this I will turn to Temstar's Guidelines to Good Asparagus:

http://forum.kerbalspaceprogram.com/showthread.php/28248-Is-asparagus-the-best-staging-system-%28might-contain-science%29?p=346702&viewfull=1#post346702

So by his guidelines, you can launch a 44.55 tonne payload with a rocket that has an estimated mass of just short of 300 tonnes (putting through my calculator, it comes out to 330, but we'll let that slide). You'll want 1049-1115 kN of thrust in the core and 603-640 kN of thrust on the boosters (assuming six boosters). An engine cluster consisting of a central LV-T45 and four outboard LV-T30s will suffice for the core, while an LV-T45 and two LV-T30s each will suffice for the booster segments. A single orange tank per stack will do the trick (by which I mean a total aggregate delta-V of 4,972.415 m/s with a TWR no lower than 1.39 at any time). Try this setup; if it doesn't work, you're not setting up your asparagus correctly.

Incidentally, 44.55 tonnes is within the tolerance of what can be launched single-stage (though just barely). You'll need to turn on clipping, you'll need nine stacks with three orange tanks and an X200-8, each with a Mainsail on the bottom. And struts of course.

Now, for your ion glider, getting it to go interplanetary is like getting anything else to go interplanetary; once it's in space it's payload just like anything else. You attach it to a transfer stage (just a big gas can and some nukes) and off you go. Something like this (second time I get to use this same pic this morning):

If you want specific details, we'd need to see your design and know what its mass is. We can work on that if you'd like.

Hopefully I've been of some assistance and haven't sounded too sarcastic or condescending - haven't had my coffee yet this morning. Not an excuse, just a statement of fact...

Edited March 7, 2014 by capi3101

[JtPB]

This is my lifter which I used to deliver orange tank (or some slightly heavier payloads) to orbit. What's below the tank is an orbital tug with enough dv and monopropellant to circularize, deliver the tank to ~1000 km orbit, attach it to orbital station, and return to kerbin. What's on sides are asparagus-connected stages to get the tug and tank out of atmosphere and on suborbital trajectory close enough to circularizing.

http://i.imgur.com/ulpxH99.png

Wow, thx. Ill try to copy that. If ill use skippers or mainsails on the asparagus' boosters it will still get to orbit?

If you're aren't opposed to mods, MechJeb will give you helpful stats in the vehicle assembly building, including the thrust/weight ratio for each stage. Very helpful for designing launchers.

Im not opposed to mods, at least not to mechjeb, but im relativly quite starter at this game. so for now im need to get expierence in vanilla...

That should be capable of lifting it to orbit alone.

*hmm, your lifter is built like that*

Mainsails are too ineffective, too heavy and with this little fuel they actually make things worse. Get rid of this stage. If anywhere, use mainsails in the first stage.

*so i should try to avoid using any mainsails as default?*

I'd suggest merging this stage with the tug.

*if this stage will be necessery at all*

Answer between the stars

Using jets or R.A.P.I.E.Rs will do help?

[Jouni]

For this I will turn to Temstar's Guidelines to Good Asparagus:

http://forum.kerbalspaceprogram.com/showthread.php/28248-Is-asparagus-the-best-staging-system-%28might-contain-science%29?p=346702&viewfull=1#post346702

So by his guidelines, you can launch a 44.55 tonne payload with a rocket that has an estimated mass of just short of 300 tonnes (putting through my calculator, it comes out to 330, but we'll let that slide). You'll want 1049-1115 kN of thrust in the core and 603-640 kN of thrust on the boosters (assuming six boosters). An engine cluster consisting of a central LV-T45 and four outboard LV-T30s will suffice for the core, while an LV-T45 and two LV-T30s each will suffice for the booster segments. A single orange tank per stack will do the trick (by which I mean a total aggregate delta-V of 4,972.415 m/s with a TWR no lower than 1.39 at any time).

I feel that those guidelines lead to overly complicated designs for marginal gain. You get essentially the same performance, if you use Skippers in the boosters and a Mainsail in the core.

[capi3101]

Well...lemme plug that in real quick then: Mainsail in the core, Skippers on the boosters, 44.55 payload. Orange tank per stack.

I come up with a 385.1875 tonne rocket that has 4,491.258 m/s of delta-V, launch TWR of 1.43 increasing to 1.99 with the third stage, falling off to 1.85 with the core stage.

You could still make orbit with that set of tweaks. The TWR is a bit on the high side, so you'd be losing a bit more delta-V to drag.

Still, that is a viable alternative, I will grant that. Maybe not quite as efficient. I suppose it depends on whether or not you want thrust or delta-V; 500 m/s of additional delta-V with my original design suggestions is not an insignificant amount after all, but if you're just going to turn around and toss it into the drink, there's nothing particularly wrong with moar thrust either.

Edited March 7, 2014 by capi3101

[Kasuha]

Wow, thx. Ill try to copy that. If ill use skippers or mainsails on the asparagus' boosters it will still get to orbit?

With skippers yes, though it may be harder. Engines used are as effective as skippers but provide more thrust (800 kN per stack rather than Skipper's 650 kN).

With mainsails only if you add more fuel I guess. It started as "classic" asparagus with seven orange tanks and seven mainsails anyway. Only through trial and error I found mainsails are unnecessarily strong and that with weaker engines I can do it with less fuel, too.

so i should try to avoid using any mainsails as default?

No, they are good as boosters. Especially if you need to lift something really heavy but need to keep number of parts down. I would just not recommend carrying a mainsail anywhere far up into the sky, similarly to SRBs. Once you left the ground you don't need that much thrust anymore and fuel efficiency starts to be the concern.

Using jets or R.A.P.I.E.Rs will do help?

It is possible to build a lifter using these and it is kind of fun, but it is slightly different category. In general - more parts, harder to get into orbit (you get to deal with flameouts etc). It's definitely worth trying and making up your own opinion though.

[Jouni]

I come up with a 385.1875 tonne rocket that has 4,491.258 m/s of delta-V, launch TWR of 1.43 increasing to 1.99 with the third stage, falling off to 1.85 with the core stage.

You could still make orbit with that set of tweaks. The TWR is a bit on the high side, so you'd be losing a bit more delta-V to drag.

I tried what I proposed before sending the original reply, and got the payload into a 100 km orbit, with 250-300 m/s to spare in the core.

The launch mass is pretty much the same as in your rocket. Your engine clusters have a total mass of 30.5 tonnes, while the engines in my rocket weight 30 tonnes.

The TWR is actually on the low side, ranging from 1.68 to 2.09 with three pairs of boosters, from 1.69 to 2.29 with two pairs of boosters, from 1.71 to 2.78 with one pair of boosters, and from 1.77 to 2.80 with just the core. During the ascent, I was never able to reach terminal velocity.

Your delta-v calculations are based on the atmospheric ISP of the engines, which is not that relevant. The actual ISP is already closer to vacuum ISP than atmospheric ISP at around 3500 m, or about 40 seconds after liftoff.

Apparently my payload was only 44.1 tonnes, or about 1% less than what it was supposed to be. That difference is probably not too significant.

[Cakeofruit]

launch it with a shuttle ^^

[Kryxal]

I've found jets to be a workable technique up to a point, you just have to remember a few things:

1) Your thrust is going to be at the lowest point on takeoff, be sure you can get off the ground. I actually used a pair of the small boosters to clear the clamps last time.

2) Once you're done with the jets, you WILL have to get them clear of you one way or another, and jets spool down not cut off. This goes double if you have anything overhanging the jets.

3) You might well be able to get over 20km up, but WATCH your intake air! Flameouts tends to mean "you will not go to space today".

4) Once your terminal velocity begins to skyrocket, this might be a good time to pick up as much horizontal speed as you can, you're more likely to run out of air than fuel.

Now that I think about it, I wonder if mounting the engines pairwise per fuel tank might be effective, I'd just have to be careful about CoM to help them clear...

[Vanamonde]

Here's a craft file you can download which delivers an orange tank to an orbit of 300km or more. It doesn't need a tug because it's a robotic ship itself. Use it, or take it apart to see how it works.

[JtPB]

launch it with a shuttle ^^

http://i.imgur.com/K7gidPs.png

Currentally i dont use mods, but thx...

It is possible to build a lifter using these and it is kind of fun, but it is slightly different category. In general - more parts, harder to get into orbit (you get to deal with flameouts etc). It's definitely worth trying and making up your own opinion though.

I've found jets to be a workable technique up to a point, you just have to remember a few things:

1) Your thrust is going to be at the lowest point on takeoff, be sure you can get off the ground. I actually used a pair of the small boosters to clear the clamps last time.

2) Once you're done with the jets, you WILL have to get them clear of you one way or another, and jets spool down not cut off. This goes double if you have anything overhanging the jets.

3) You might well be able to get over 20km up, but WATCH your intake air! Flameouts tends to mean "you will not go to space today".

4) Once your terminal velocity begins to skyrocket, this might be a good time to pick up as much horizontal speed as you can, you're more likely to run out of air than fuel.

Now that I think about it, I wonder if mounting the engines pairwise per fuel tank might be effective, I'd just have to be careful about CoM to help them clear...

I think ill use R.A.P.I.E.R only, not regular jet. I tried & succeed at gettting SSTO to orbit with only four RAPIERs(+high-altitude intakes) & one full jumbo, with a little help from boosters in the first seconds. I think theres a lot of hope in these engines...

It seems like you can now build a space shuttle without an external fuel tank(or at least not that huge as you though you'll need) with them!

Edited March 7, 2014 by JtPB

[SRV Ron]

Placing a orange fuel can in orbit is not that difficult, if you design efficiently. This asparagus design, using Skippers with a pair of Mainsails on the third pair, does so efficiently.

And, in orbit.

The core booster is designed for recovery along with the fuel can after it is docked and drained.

[SRV Ron]

After looking at attempts to place five full fuel cans at once in orbit, I designed this all stock launcher at 1,452 tons. Note, it only uses one SAS ring and one mono prop tank. The rocket has minor spin but is quite flyable.

Five full fuel cans and core stage totaled 216 tons in orbit. As you can tell, there is plenty of fuel in reserve to go to a much higher orbit.

[JtPB]

After looking at attempts to place five full fuel cans at once in orbit, I designed this all stock launcher at 1,452 tons. Note, it only uses one SAS ring and one mono prop tank. The rocket has minor spin but is quite flyable.

http://i.imgur.com/UgECGod.jpg

Five full fuel cans and core stage totaled 216 tons in orbit. As you can tell, there is plenty of fuel in reserve to go to a much higher orbit.

http://i.imgur.com/JspCvuz.jpg

thats useful if you want to build your station/base fast..