Putting monsters into orbit??!

[Der Anfang]

Just how does one get a 90+ tonne vehicle into LKO and beyond? I mean, I've managed to get a few 80-90 tonne payloads in previous versions, but since they are so large, the rocket tends to be extremely unstable and requires something with a lower profile. (i.e: asparagus staging) I use the asparagus approach... but it's almost impossible to push away any of the stages from the central kerbodyne tank without the use of seperatrons, but they heat up the central rocket and cause it to explode. If I don't use seperatrons, the shed tanks just crash into it, and the push-away wing approach isn't sufficiently strong enough to push away such heavy spent tanks.

What methods are people using to get these monsters into orbit? I can't seem to go beyond 70 tonnes before I start running into launch stage design complications.

[Randazzo]

Just how does one get a 90+ tonne vehicle into LKO and beyond? I mean, I've managed to get a few 80-90 tonne payloads in previous versions, but since they are so large, the rocket tends to be extremely unstable and requires something with a lower profile. (i.e: asparagus staging) I use the asparagus approach... but it's almost impossible to push away any of the stages from the central kerbodyne tank without the use of seperatrons, but they heat up the central rocket and cause it to explode. If I don't use seperatrons, the shed tanks just crash into it, and the push-away wing approach isn't sufficiently strong enough to push away such heavy spent tanks.

What methods are people using to get these monsters into orbit? I can't seem to go beyond 70 tonnes before I start running into launch stage design complications.

I once commissioned a highly educated and thoroughly well-recommended artist to draw up a technical diagram demonstrating how to get around a very similar problem, and I think it may apply here.

You may need extra boosters to push heavier tanks away due to the angle of thrust.

Also, if you're not opposed to mods, you can tweakscale to create 5m diameter parts or larger, or use a mod that has parts in the larger sizes such as SpaceY Heavy Lifters. This allows you continue building vertically instead of having to rely too heavily on boosters on top of boosters.

Edited July 28, 2015 by Randazzo

[Spartwo]

Keep the centre of lift behind the centre of mass throughout the flight(with many fins)

[Camaron]

The game calculates the damage or engine exhaust in a single, perfect beam, so you only need to miss the core tank by a very slight amount.

Edited July 28, 2015 by Camaron

[Pecan]

Coincidentally, I've just made a 100t+ launch vehicle for someone who seemed to need something really simple:

It's a SSTO and MJ flies it perfectly with standard settings (although I recommend 75km orbit)

3 stacks of

5 x S3-7200

S3 KS25x4

nosecones and fins to taste (I just have basic fins at the north/south of the side-stacks and east/west of the centre stack)

(batteries and RGU on centre stack, SAS units on side-stacks).

Edited July 28, 2015 by Pecan

[Vanamonde]

Moved to the subforum for how-to questions.

[Superfluous J]

There are several working strategies. My personal favorite is to set up a mining operation on Minmus, and bring the fuel down to LKO for a huge refueling station. Then, you can use all the fuel tanks that you're going to use to get wherever you're going to also get into LKO from the surface. You can even then use those same tanks get to Minmus (after an LKO refuel) to refuel AGAIN, before heading out. Not only does that save you fuel and tanks (and the fuel and tanks to lift them as well) on launch, it makes the resultant ship smaller due to the 700ish free m/s of dV you get from refueling at Minmus (if you go that route, it's frequently not necessary).

I have a 147 ton ship I'm sending to Jool. The total mass on the launch pad is 340 tons. The extra 193 tons is 8 solid rockets and 4 disposable fins to help get the behemoth into LKO, and everything else is going to Jool, after a stop at Minmus. That's a 43% payload ratio, and (more importantly in career) an 84% cost ratio (The payload is 182,965 funds while the extra stuff costs 34,928 funds).

[Warzouz]

Make it simple and add fins at the bottom of the rocket.

15 to 300T cheap LKO stage. I even did a quick and dirty 600T.

http://forum.kerbalspaceprogram.com/threads/123195

[xtoro]

Instead of seperatrons, use fins at the top of the stages angled 5* from vertical, outwards. The lateral lift will pull the stages away from the rest of the ship.

[mrclucks]

As long as you have a stage that has a ~1 twr, you'll be able to more or less maintain velocity and probably even accelerate. You'd need srbs to push through the first 10-15 km, but that's why we have srbs.

Your rocket can have a wide fat front, as long as the bottom is just bigger. Use that and make sure you have an engine that can gimbal and/or RCS(but if you have to use up alot of monoprop, then you should consider redesign) along with some big enough fins to make sure the more draggy ends face retrograde.

You should also consider doing a less than perfect gravity turn if you're not tight on dv and have trouble getting your angle at 45 degrees when you're at 15km. Space is much much more forgiving with aerodynamics than kerbin is since there is none. If you use up some of your payloads fuel, you can always refuel in orbit via a docking port or the klaw (the klaw is our master! The klaw chooses who will go and who will stay).

Back to your original problem of tanks bping into and exploding, if you have the tanks positioned with its CoM near or right on the decoupler, then it should just slide right off. You should be able to see its CoM by selecting the decoupler as the root part and emptying the tanks, and moving the tank vertically till it sitting fairly close to the decoupler(havnt actually done that before, but I've gotten pretty good at eyeballing it due to my refusal to work with sepertrons). If you're willing to install a mod, space y have two decoupler that have sepertrons built in so that when you decouple, it will basically shoot the tanks out, but balancing can be a problem if it's far from the CoM.

[Edax]

The best way to combat separating your boosters is to just make your launch vehicle simpler. Just make the LF+O boosters x-large enough to take you into LKO without any staging, and use solid rocket boosters to get the TWR so that you can lift that extra fuel off the ground (but of course dump the solid rockets when their empty). Separating boosters is a lot simpler when you do it in orbit. I also use TT-70 Radial Decouplers attached to the payload plus a strut on that to put distance between the payload and boosters, and I'll place the LF+O boosters symmetrically around the payload. They'll simply put me in space and once there, I drain the extra fuel from the boosters and have low-power sepratrons detached the boosters safely away. That'll usually be enough to at least get me to Minmus.

This is my heavy booster system using only size 2 fuel tanks and engines. The payload is very tall, and has 8 engines, none of which are used on the assent.

Edited July 29, 2015 by Edax

[Norcalplanner]

Pictures would help a lot. What does your rocket look like? How wide and/or unaerodynamic is the payload?

[Korizan]

Kind of hard to answer as the design and the shape dictate how you get it into Orbit.

For example

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This was a test for the center piece of a refueling station.

It weights in at 240 Tons with fuel. The total rocket weight on takeoff as you can see is 1,593 tons.

As this is a 2 stage to orbit I only needed the seperatrons to push the old stage away and they are angled straight down instead of out.

Edited July 28, 2015 by Korizan

[Starwaster]

Jump to image #15.... that's a large assembly encased in one of e-dog's Procedural Fairings (with the non-detachable fuselage) with 4x 3.75m KWR boosters. Also skip past that to the station core I put up in one piece with the same technique. (that one's more detailed in its space operations but skips most of the launch)

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[Snark]

Regarding the booster-collision problem:

I've never had any problems with laterally-mounted boosters (e.g. asparagus tanks) colliding with the central rocket. The main thing is to make sure that you attach the booster as low as possible on the radial decoupler (i.e. the radial decoupler's attachment point on the radial tank is as high above the radial tank's CoM as possible).

When the decoupler fires, it will naturally tend to make the radial tank rotate slightly away from the main body of the ship (since it's applying the repulsive force above the tank's CoM). Even a tiny bit helps, because the airflow against the side of the (slightly) tilted tank will tend to pry it further away from the main body of the ship.

Add to this the fact that the central ship is continuing to accelerate (because it's got its own engine firing), and it just works.

On another note:

If your monster is headed beyond LKO (e.g. if you're going somewhere else that will require a lot more dV than just LKO): You can make your life easier by not trying to do it all in one go. Just give your monster enough dV to make it to LKO, so that it ends up there intact, but nearly empty of fuel. Then you can launch refueling missions to top it off before it heads out into the great black beyond.

Finally: For really big craft, you can assemble them in orbit, using docking ports. Of course, the problem with this is that docking-port joints are very floppy, and your craft will tend to wobble all over the place. However, if you're willing to use Kerbal Attachment System, this becomes much simpler: it includes "strut sockets" that you can mount on your craft, so that after you dock, your kerbal can go EVA and attach struts to stiffen things up. Works like a charm.

[Jett_Quasar]

I've found that having nose cones on large rockets tends to cause them to collide with your craft on ascent. I had that problem launching one of my large starships so I removed the nose cones - problem solved.

JR

[Der Anfang]

Instead of seperatrons, use fins at the top of the stages angled 5* from vertical, outwards. The lateral lift will pull the stages away from the rest of the ship.

As I have aforementioned, the fins at the top with sufficiently larger booster tanks just don't generate enough force in time before they bump into the central stage.

Also, @everyone else, thank you for your help and further assistance is appreciated. When I get a moment, I will share pictures. F1 and F2 still work even in VAB/SPH, no?

Edited July 28, 2015 by Der Anfang

[sgt_flyer]

I could direct you to my Chaos star series of launchers if you want to launch something truly huge (they were designed in 1.02 - they should still work, but might require more throttling down through the ascent)

The key for such large vehicles, is to share the load across the elements through careful strutting. (On those Chaos star, struts connect the payload to the whole upper stage)

(One good way to strut side boosters is to use soyuz style strutting : you strut the top of the booster to the core stage, and the lower part is an x-shaped horizontal strutting)

http://forum.kerbalspaceprogram.com/threads/115732-V1-02-Chaos-Star-Series-1500-1200-and-500-tons-to-LKO-launcher-maximum-fairing-diameter

Here's the Chaos star 500 - and it's the smallest of the series at 500 tons of payload to LKO

(There's a 1200t and a 1500t of payload version too )

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Edited July 29, 2015 by sgt_flyer

[Fisk02]

Add more boosters

[Sharpy]

Cygnus RR-300 - 300 tons of payload to LKO in a single fully recoverable stage.

If 300 is too much, you have smaller versions, for 15, 32, 50, 75, 100, 125, 150 and 200 tons of payload.

If your payload is draggy or otherwise difficult, use a "notch higher" version for launch.

[Kryxal]

For a simple solution specifically for the big SRBs, just add a nosecose (basic one's fine) and a separatron at the FIRST point that it shifts off-vertical. The thrust is mostly down and a bit out, and I only use that as a boost to an asparagus layer so there's never anything above to hit anyway.

[match]

I do something similar and only rarely have issues.

I flip the Sepratrons upside down with just a tad of angle toward the main stack. And I don't stage unless my Angle of Attack is low (within the prograde indicator on the Nav Ball).

If you want the spent stage to be away from your main stack, then thrust it in the opposite direction of travel. While it is only a nudge, the remaining engines do the real work and keep accelerating out of harm's way. No sense trying to control where that stage is going once released, much more sensible to put the trouble behind you.

[Pecan]

For the original 'how to' question, there is one solution that a lot of people use but that we haven't mentioned - because it's always someone else that did it: Hyperedit.

[Norcalplanner]

I've never used hyperedit, but I have used and abused both SpaceY and KJR to loft some pretty darn big loads, including large unaerodynamic space stations.

Launched this 700 ton station in just two parts. Only has four struts.

Edited July 30, 2015 by Norcalplanner

[Padishar]

You can launch some pretty un-aerodynamic vessels without too many problems in 1.0.4 as long as you accept some extra drag losses and/or fly a steeper ascent than usual. I stuck this in orbit yesterday, 389 parts and > 3500 t on the pad and no fins or nosecones in sight. The payload is > 400 t and there is still a stage and half of fuel left in the launcher...

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Each booster has a single sepratron at the inside top edge pointing upwards and slightly inwards to give them a little push away. It didn't need them in versions before 1.0 but the boosters tend to knock engines off when they slide away without them now...

Edited July 30, 2015 by Padishar