Wcmille

Standard Lift Subassemblies

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1 minute ago, Wcmille said:

These are beautiful works of engineering! What is the flight plan, TWR (vac) and DV (vac) of the stages?

Wcmille,

 Thanks, but the form really just follows the function in these cases.
Flight plan: Standard gravity turn with 5° prograde kick at 80 m/sec velocity.
TWR (vac): If you mean initial TWR of the core when the boosters are released, it's 0.7G.
DV (vac): In the above context, 1,600 m/sec.

 I don't use KER, so some of my figures may differ or may not be able to wholly answer your questions.

@Nich did a KER analysis of one of my rockets:

zVmUeJW.png

If you need more info, I can kick you a .craft file to play with.

Best,
-Slashy

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Are all upper stage solid rockets in the staging list just sepatrons?

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31 minutes ago, Wcmille said:

Are all upper stage solid rockets in the staging list just sepatrons?

Wcmille,

 Aye. I did away with them in later iterations. Best,
-Slashy

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FWIW, I used to build payload-rated subassemblies, but I found that it tied me down to the mods I built them with. So I wrote a script that calculates the cheapest engine/fuel tank combination that can lift a given payload to LKO. My restrictions are 1.2 < TWR < 1.3, and dv > 3300. Also, every launcher I build is SSTO, so I prune all SRBs. Usually I require 1 reaction wheel of the same size per engine, and use at least 3x symmetry tail fins for stability. I launch them with the default mechjeb ascent guidance settings. 

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3 hours ago, drhay53 said:

FWIW, I used to build payload-rated subassemblies, but I found that it tied me down to the mods I built them with. So I wrote a script that calculates the cheapest engine/fuel tank combination that can lift a given payload to LKO. My restrictions are 1.2 < TWR < 1.3, and dv > 3300. Also, every launcher I build is SSTO, so I prune all SRBs. Usually I require 1 reaction wheel of the same size per engine, and use at least 3x symmetry tail fins for stability. I launch them with the default mechjeb ascent guidance settings. 

What cost/ton are you getting with that?

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9 hours ago, Wcmille said:

What cost/ton are you getting with that?

I checked my launch from last night and it's $3000/ton; I'm not really min/maxing cost though, just making sure that I am using the cheapest engine / engine cluster that can go SSTO and has enough thrust to get the job done. Also, the payload was very small, only 3t. 

Edited by drhay53

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33 minutes ago, drhay53 said:

I checked my launch from last night and it's $3000/ton; I'm not really min/maxing cost though, just making sure that I am using the cheapest engine / engine cluster that can go SSTO and has enough thrust to get the job done. Also, the payload was very small, only 3t. 

Why SSTO? Is that so you can deorbit the launcher?

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11 minutes ago, Wcmille said:

Why SSTO? Is that so you can deorbit the launcher?

yes, I use stage recovery to recover ~50% of the cost of the LV, also, I like to keep debris super clean for FPS reasons, so I don't like to have a bunch of junk to clean up. 

I am going to do a better test of my cost/t, using the NRAP test weight and some larger payloads. I think the $3000/t for a small payload is a bit of an overestimate. 

edit: also, it's super fast to build SSTO's, vs. playing around with the TWR and delta-v by hand when using SRBs. I just find it much faster to build rockets using SSTOs with my program that tells me which rockets and tanks to use. 

Edited by drhay53

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My standard "sub-assemblies" are reusable spaceplanes. The biggest I made was capable of carrying 80 tonnes to orbit and the cost per tonne was incredibly low. 200ish credits per  tonne if not less. The  only cost was fuel since the plane landed back on the runway. Very economical and 80 tonnes to orbit was more than plenty for my career at the time.

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The thing that has kept me away from spaceplanes is just that it takes way longer to launch and recover. A big thing for me in KSP is that time is a resource; I want to spend more time assembling space stations and bases, and doing science, instead of launching/landing spaceplanes. I have strongly considered using a fleet of spaceplanes from KerbalX though, and I probably will do it again at some point :)

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30 minutes ago, drhay53 said:

The thing that has kept me away from spaceplanes is just that it takes way longer to launch and recover. A big thing for me in KSP is that time is a resource; I want to spend more time assembling space stations and bases, and doing science, instead of launching/landing spaceplanes. I have strongly considered using a fleet of spaceplanes from KerbalX though, and I probably will do it again at some point :)

I can definitely see where you're coming from. It does take much much longer to launch and land, however for me (I know everyone has different tastes), the piloting aspect is just as fun as the orbital assembly, collecting science, and faffing around in rovers, etc...

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1 minute ago, Leafbaron said:

I can definitely see where you're coming from. It does take much much longer to launch and land, however for me (I know everyone has different tastes), the piloting aspect is just as fun as the orbital assembly, collecting science, and faffing around in rovers, etc...

I get it, totally. I just tend to autopilot as much as possible for the routine type of stuff. I never really have gotten my HOTAS setup for KSP, perhaps if I did that, I would use spaceplanes more. I've just found that if I want to get some flying in, I prefer other games with more consistent framerates.

So I did some more testing of my SSTO strategy; I think ~$3000-4000/ per ton, before Stage Recovery, is probably going to end up being the true number. I'm still fairly early in a career though, so my engine options are somewhat limited; I don't have Mainsail's yet, for instance. 

Stage Recovery shaves off ~$1000/t; if I try to optimize where it re-enters so that it's closer to KSC, I think I could increase the number. But normally I just do the de-orbit burn wherever I reach orbit. 

So let's say for now my method costs $2000-3000 / t, but costs me a very small amount of time, and is flexible to any mods (I simply keep ascii files with the available tanks and engines, and then my code runs easily). So I'm paying a little premium for speed and flexibility.

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4 hours ago, Leafbaron said:

My standard "sub-assemblies" are reusable spaceplanes. The biggest I made was capable of carrying 80 tonnes to orbit and the cost per tonne was incredibly low. 200ish credits per  tonne if not less. The  only cost was fuel since the plane landed back on the runway. Very economical and 80 tonnes to orbit was more than plenty for my career at the time.

Leafbaron,

 Yeah, there's that, too. :D

 I use spaceplanes to lift "stuff" and boosters to lift "things". Boosters are a lot more tolerant of size/ shape variations of their payloads. Spaceplanes make nice containers for supplies and crew that must be transferred across docking ports.

 Also... I like to use the payload to help itself to orbit whenever possible. If it has fuel tankage, I'll use that to feed the stack. If it has engines, I'll use them on the way up, etc. It's very economical to refuel something in orbit using spaceplanes.

Best,
-Slashy

 

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I've been trying to focus on reusability in my current game.  As someone above points out standardised boosters have their limitations when you start on odd sized/shaped payloads, but they do the job for quite a lot of stuff.

I've been using this SSTO to put up to 45 tonnes in to an 80-100 km orbit.  Landing it on the grasslands between the KSC and the mountains recovers 97.5% of the parts cost, meaning it's a very cheap launch, but I've not got the figures on me.  The only non standard parts on it are the landing gear which are replicas of New Shepards legs from the Kerbal Reusability Extension mod.  The booster is bulky enough it doesn't seem to need fins unless it's a really odd shaped payload.

siErktS.png?1

I don't always manage to land it quite this accurately though :D

It's taken a while to work out the right descent profile as too steep or too shallow can result in the Mainsails overheating and exploding.  From 80km I give it a 200m/s de-orbit burn and position the impact trajectory about in line with the island to the north of equator east of the KSC.  In theory I aim long and use the airbrakes, drogues and parachutes to shorten the landing as appropriate to get it as close the KSC as possible, I really thought I was going to overshoot on this one though. 

For heavier launches I've strapped disposable boosters on the side, but I've not yet built a heavier fully reusable one.

 

ETA:  Works out at about 550 kredits per tonne I think

Edited by RizzoTheRat

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I steer a middle course between prebuilt subassemblies and build-to-order.

For each standard diameter (for me, 1.25, 1.875, 2.5, 3.75, and 5.0... of course you can see I have some mods in there), I have identified one or two best-in-class engines for (A) the launch stage and (B) an upper/second stage; I put one long fuel tank on each and add fins (launch stage) and parachutes (StageRecovery...) and save them as subassemblies.  I did this after noticing that I was continually going back to similar configurations for similar-sized/weight payloads, so it just made sense.    Once I've built the payload, based on the radial size and overall payload weight, I start out with a 'standard' upper stage and launch stage and see how close that comes to what I need-- then start refining (adding/subtracting fuel, trying different engine combinations, etc.)  So it isn't totally pre-fab.

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