Heavy lifting

[MPDerksen]

I need to put a larger payload in orbit around Mun.  My design looked reasonable, with 6 SRB and a Mainsail in the middle.  I crashed almost right away.  So, I waited to engage the mainsail until I got some momentum for the fins.  Again, as soon as I try and turn over on the slightest gravity turn, I lose control.  Do I need some additional reaction wheels?  How do I even begin to evaluate the proper build for this launch?  Perhaps I need a smaller payload and just dock it all together in smaller pieces?

[Geonovast]

As with almost all questions about rocket design, we're going to need to see some pictures of the craft you're working with.  Based on what you're saying, you have way too much drag up top, which is grabbing the air and whipping the rocket around.

Impossible to say without pictures though.

[Aegolius13]

Yeah, pics would definitely help.  Are you saying in your second attempt, the rocket crashed before you turned on the Mainsail?  In general, a Mainsail ought to have more than enough control authority to keep a rocket heading the right way., so I doubt the problem is there.  But if the Mainsail is off entirely, that  be an issue.  However, reaction wheels tend to be the least effective attitude control option in dense atmosphere, vs. gimbaling engines, RCS thrusters or moveable fins.  

My main suspects are:

1. Your craft is aerodynamically unstable because, as @geonovast points our, your craft is too draggy at the front.  

2.  You're going too fast, too low.  Do you know what your TWR is in the early stages of launch (you can also look at the g-force indicator).  Assuming the SRBs are Kickbacks, six of them plus a Mainail is quite a lot of thrust, and SRBs really pick up thrust as they burn out.  

In any event, it's safe to say the issue is not that your payload is too big and needs to be split up.  It's feasible to launch much, much larger payloads (with oodles of Mammoths, for example), and still have decent stability.  

[bewing]

If you don't feel like redesigning anything -- then lock SAS on vertical and launch straight up. That's almost always a lot more stable than trying a gravity turn. You can begin a turn once you are up to 20 or 30km or so. Yes, it's slightly inefficient, but it's sometimes better than tearing your hair out.

[MPDerksen]

Here is what I'm trying to launch, and below that is the tech tree that is currently unlocked (so you can see what parts I have to work with.
As soon as the mainsail gets triggered, I get loose.  If I try and turn over at all, it goes crazy.  I'll try Bewing's idea.  I am happy to construct smaller payloads, but I'm stuck not really knowing how to piece things together with the limited parts I have currently unlocked.  Maybe I need some additional Mun landings to collect more science, bigger parts, and then I can build the station?

 

[MPDerksen]

Tried it.  Using ONLY the SRB I can go almost completely straight up.  I can turn it a little, but stays in control.  I get an Ap of about 65K before burn-out.  As soon as I engage the Mainsail, I start flipping end over end.  I kill the engine, and the flipping just keeps going and never even slows down.  I tried with a Poodle instead and got the same result.

I’m going to try to remove part of the mass up front and see if I can reduce the issue, but I would really like to get this part in orbit, since it’s the biggest part of the station I want to construct.  Once I get this up, I think the rest will be easy.

[FleshJeb]

• Take the upper fins off, unless you're trying to land the central core later..
• Use different fins. Those are the weakest ones.
• Reduce the gimbal range on the Mainsail to 50%. Excessive gimbal can kill you.
• Reduce the thrust on the SRBs to 50%
• Offset the SRBs/radial decouplers down until the rocket rests on them. They're draggy.
• Strut or Autostrut the payload. You might have bad payload wobble.
• Launch with the both the SRBs and the Mainsail on. The mainsail will help control. You can always throttle back if need be.

FYI, those are NOT docking ports attached to the side.

Also, THIS is heavy lifting (and it's an SSTO)  : 

 

Edited March 23, 2019 by FleshJeb

[MPDerksen]

10 minutes ago, FleshJeb said:

• Take the upper fins off, unless you're trying to land the central core later..
• Use different fins. Those are the weakest ones.
• Reduce the gimbal range on the Mainsail to 50%. Excessive gimbal can kill you.
• Reduce the thrust on the SRBs to 50%
• Offset the SRBs/radial decouplers down until the rocket rests on them. They're draggy.
• Strut or Autostrut the payload. You might have bad payload wobble.
• Launch with the both the SRBs and the Mainsail on. The mainsail will help control. You can always throttle back if need be.

FYI, those are NOT docking ports attached to the side.

 

done.  Flipped over at 300m, less than 100m from the surface.  Immediate failure.  even with a reduced payload.  Scratching my head here, since I'm not really understanding the WHY part, so just throwing random ideas out.

[FleshJeb]

@MPDerksen I just realized the Cupola is probably the control point. It's upside-down, so your controls are reversed.

[Aegolius13]

1 hour ago, MPDerksen said:

I’m going to try to remove part of the mass up front and see if I can reduce the issue, but I would really like to get this part in orbit, since it’s the biggest part of the station I want to construct.  Once I get this up, I think the rest will be easy.

For stability, you WANT as much mass to be up front (i.e., at the top of the rocket) as possible.  And you want sources of drag to be as far back as possible.  Think of an arrow or dart - heavy front, fins at back, stable in flight.  

See also:

https://en.wikipedia.org/wiki/Pendulum_rocket_fallacy

I'd keep the fairing regardless.  That transition to the cupola module is going to generate quite a bit of drag, as do the RCS thrusters and docking ports.

Also, those curved winglets have no controllable surface area, so if you're looking for more control authority they're step down from the Delta Deluxe.  You can right-click on parts to check this state.  The AV-R8, canards, tail fins and elevons all have more.  But as mentioned above, when the Mainsail is running, you should have plenty of control authority without needed help from fins.

 

23 minutes ago, FleshJeb said:

@MPDerksen I just realized the Cupola is probably the control point. It's upside-down, so your controls are reversed.

That sounds quite plausible.  If the navball shows brown instead of blue at launch, then it's upside-down.

[MPDerksen]

Well, I just modified about everything.  I went with a near duplicate of Orb8ter's Station tutorial.  Except I used 6 boosters in Asparagus staging instead of just 4.  I got the 2 modules you see here around Mun, and docked together.  I need to create a central hub, or earn enough science to unlock the HubMax, then position it between these 2 points and add more hab space.  The mission requires 15 seats.  I have 7.  Still, a significant amount of progress tonight.  Looking forward to landing, getting a little more science and putting those Kerbals to work in the lab.

[MPDerksen]

It’s still a bummer that I have zero control on the dark side with a probe core.  I can’t fire the engine at all once I lose CommNet. I guess I need a relay in synchronous orbit?  Otherwise I’ll need a pilot for dark side science.  Should I be planning on taking the science jr. on my biome hops?  Or is the fuel not worth it?  Maybe that’s more appropriate when I move on to Minmus.

[Aegolius13]

52 minutes ago, MPDerksen said:

It’s still a bummer that I have zero control on the dark side with a probe core.  I can’t fire the engine at all once I lose CommNet. I guess I need a relay in synchronous orbit?  Otherwise I’ll need a pilot for dark side science.  Should I be planning on taking the science jr. on my biome hops?  Or is the fuel not worth it?  Maybe that’s more appropriate when I move on to Minmus.

You don't necessarily need relays in synchronous orbits.  I'd say it's more common to just have 3-4 at some arbitrary altitude.  The more important factor is that their orbital periods match, so they don't drift out of position over time.  

 I would take the Science Jr. if your ship has the fuel for it.  It's bulky but not really that heavy.  And it gives pretty hefty science returns.  Plus, it's always a pain to have to go back later to the same biomes to take new readings (though that's often necessary once you get advanced instruments like the gravitometer).

[bewing]

3 hours ago, MPDerksen said:

It’s still a bummer that I have zero control on the dark side with a probe core.  I can’t fire the engine at all once I lose CommNet.

Yes, as I recall you do have partial control with your settings. You can change SAS modes on your probe cores, and you can go to full throttle with the Z key. During half your orbit you have full control, so you can set the thrust levels of your engine very low, and then you can perform dockings or many other manuevers by just going to "full" (reduced) throttle.

 

[MPDerksen]

Pretty excited about this.  I had to built my own hub, and based this off the Orb8er design.  I have it in LMO, waiting for the existing station to catch up.  I still have 90 of mono, and 1028m/s for maneuvering.  Around it, there are 2 docking ports, and 2 Jr. ports.  The rocket is connected to another booster, but I'm hoping to save it there as a fuel source for my lander(s), since it has no probe core for control once I decouple it.  The plan is to get in a parking orbit, then separate the existing station in 2, and re-dock them with this hub.  Once I finally send up more seats in the hitchhiker launch, the mission will be complete.  I also need to calculate the electrical requirements of the Science Module and make sure to send enough solar.  I haven't unlocked the XL yet.

[MPDerksen]

That was pretty easy.  Of course, you have to remember to take the core out of hibernation for it to actually function so I can dock.

Now a question:  Jeb got 10 science by taking a Crew Report on the way up.  I transferred him to the science module, but there is nothing there to process?  How do I move the data to the lab?

[bewing]

1 hour ago, MPDerksen said:

I transferred him to the science module, but there is nothing there to process?  How do I move the data to the lab?

For experiments gathered by Kerbals, they get stored in the pod where the Kerbal boards the craft. Experiments gathered by devices are contained in the devices.

There are only two ways to move experiments around from their original containers:

Either you can use a Science Container's "Collect All" button to move one copy of every experiment on the combined ship into the Science Container.

Or, you can send a Kerbal out on EVA, float over to the container/pod/device that contains the experiment, open the context menu of that container/pod, use the Take Data button to gather all those experiments into the Kerbal's pockets -- then float over to a new pod or container and either board it, or open its menu and use the Store Data button.

Moving a Kerbal around inside a craft does not move any experiments.

 

However -- that is not how you use a Mobile Science Lab. To use a Lab, you must have a scientist in the Lab. Then you open the context menu of any science container/pod on the entire craft and select the "Review Data" button. As you examine each experiment, it will have an additional yellow button: "Process Data". Click that. Doing that will convert your experiment into some Data Points in your Lab. (Note that the experiment is destroyed when being processed.) You can load your Lab up with 750 Data Points. Over time, those data points get converted slowly into Science points. After you have some Science points, you transmit them by hand back to KSC through an antenna. It takes quite a bit of EC to transmit 1 science point. So you have to have a lot of EC stored, or a gigantor panel in full sunlight.

Edited March 24, 2019 by bewing

[MPDerksen]

Got it.  when you said it was slow, I had no idea!  Is there any harm in just time warping a few years?  This thing become nearly useless, since by the time you can get it somewhere, you are advanced enough in the tech tree to need 300+ to do anything.

[bewing]

The only harm is if you have accepted contracts that expire in the near future. If they expire, you get penalized.

[Kryxal]

Also, if you fill the lab with data to be processed, it tends to cap out on science to transmit after a few days.  Best you have sufficient battery reserve for the transmission, and enough panels to sustain operations.

[MPDerksen]

15 minutes ago, bewing said:

The only harm is if you have accepted contracts that expire in the near future. If they expire, you get penalized.

nice catch.  hadn't thought of that.  Thanks.  I think I'll wrap up the Station contract on the next launch.  I need 7 more seats.  If I put a small hitchhiker on top of an MK2 pod, that's 7.  Then, land, grab science (and the the points for "plant a flag on the Mun" contract), come back up, refuel and go home with the extra pilots I have at the station.  
The next part won't look pretty, but functional.

3 minutes ago, Kryxal said:

Also, if you fill the lab with data to be processed, it tends to cap out on science to transmit after a few days.  Best you have sufficient battery reserve for the transmission, and enough panels to sustain operations.

I watched it in 1000x mode.  The batteries are dropping to near zero as I pass the dark side, but fully recharge before sunset.  So yeah.  More of both would be a good plan.  a few extra ports on the next section for just that is the plan.