Norcalplanner

Just wanted to drop a note to say... WOW! NB, I've always enjoyed your mods thoroughly, and recommend them frequently to others. This is definitely kicking things up a notch. Thanks again for all the hard work you put into your mods. It shows.

Wumpus, Thanks for the post. While I agree that having a higher initial TWR off the pad is a good way to minimize gravity losses, it's not necessarily the best way to go when minimizing cost per ton to orbit. It can also introduce aero losses which begin to offset the gravity losses if you go too fast when still deep in the atmosphere. Especially when it comes to Kickbacks, thrust reducing the SRBs also has the benefit of making them run longer before burnout. I'll frequently find that the initial burn with thrust-limited Kickbacks lasts for the first 90 or so seconds of the launch, with a steadily increasing TWR that whole time. Nearly all of this tutorial was written based on 1.0.4 game physics, so it's definitely not a case of old aero. In terms of having a low TWR for your orbital insertion stage, that's primarily for serially staged LFO rockets where the low TWR stage only has to do 500 to 700 m/s of burn to achieve orbit. I've put the imgur album below which is the single time I had an insertion TWR of 0.42, which was for a payload mass fraction challenge that used cross-feeding. The orbital insertion stage only has to do the last 700 m/s to get to orbit, and the vehicle was already at 44 km with a speed of 1,700 m/s when that stage started to fire. I also note that 0.5 or 0.6 is likely more suitable for an orbital insertion stage, but also only for limited delta V requirements. If a craft needs 1,200 m/s for orbital insertion, then the TWR is going to need to be up around 0.8 or higher, and you'll need a more vertical gravity turn. TWR of 0.3 was intended to be the minimum for a transfer stage for a craft which is already in orbit (such as a Jool mothership) - I apologize if that wasn't clear. In running tests, I found that having a TWR of 0.3 was the minimum reasonably required to reach common destinations with a single transfer burn while still retaining a fair bit of accuracy from a 250 km parking orbit. Steering losses really start to mount when the TWR is down at 0.2 when you're going to Jool unless the ship's is in a ridiculously high parking orbit, which gives up a lot of Oberth effect. Your Kickback rocket design sounds interesting - any chance you could post a pic of it? Sounds like it may be similar in concept to Slashy's, where he had different levels of thrust limiting on the initial clusters of SRBs, but without any staging to minimize the expense.

Yep. Direct link to KerbalStuff KJR is here: https://beta.kerbalstuff.com/mod/53/Kerbal%20Joint%20Reinforcement

I'd echo those suggesting KJR. It really ought to be stock. I see a few issues with the design: 1) All the struts create a bunch of drag, which is slowing down your ascent and probably exacerbating any latent stability issues. 2) The TWR jumps down to 1.30 after the Hammers burn out, which is too low for that point in the ascent. A gravity turn in KSP needs to have TWR increasing for at least 50 or 60 seconds before ratcheting down to something lower. The next two stages also have a very low TWR. I've found that the first 2,500 to 2,700 m/s need to be at a TWR significantly above 1. 3) I also don't quite understand how your last stage with a Terrier has so little power. If you put a Terrier and an FLT-400 beneath a Mk1 capsule, you should have several thousand m/s of delta V and a TWR well above 1. What are you carrying up top that's so massive? Ideas and potential solutions: First, cut out any extra weight from the top of the rocket. Empty monoprop in the capsule, empty most of the ablator from any heat shield, see if you can lose a parachute, etc. An upper stage powered by a Terrier should have at least 2,000 m/s of delta V. Next, install KJR and remove all the struts. Also, relocate the fins so that they are on the cardinal directions of the rocket - it will make the gravity turn, as well as any other steering in atmosphere, much easier. Lastly, if you've unlocked the Terrier, you've likely also unlocked the Thumper. Consider ditching the radial stacks you have (Hammers and Reliants) and adding two or four Thumpers on radial decouplers instead. Have them fire at the same time as the Swivel in the middle. Put enough fuel on the Swivel for it to burn for at least two minutes. Thrust limit the Thumpers in the VAB for an initial TWR of 1.3 to 1.4 or so, making sure that the TWR after they detach is at least 1.2. Also, relocate the fins so that they are on the cardinal directions of the rocket - it will make the gravity turn, as well as any other steering in atmosphere, much easier. Good luck!

Earthslug, I'm glad you found the guide to be helpful. If you have any questions as you move forward, feel free to ask.

I named my design philosophy - it's "Cheap and Cheerful". Click the link in my signature for my guide, which uses many, many words to fully describe it.

That might be a bit difficult - the first stage is only SRBs.

SpaceY is working right now and includes a bunch of 5 meter parts. SpaceY extended adds 7.5 meter parts if you're feeling particularly adventurous.

Just did a quick build showing what I described:

Lots of good tips and tricks are in my tutorial thread: Rules of Thumb for Building Cheap & Cheerful Rockets. For a mun mission, you can get a workable 2.5m rocket with a lot of delta V using the following simple formula: 1. Put any 1 or 2 man capsule on top of a Rockomax 16 with a Terrier on the bottom. Add bits and bobs to make it a lander, with several thousand m/s of delta V (enough to get from Mun orbit to the surface, back to Mun orbit, and back to Kerbin). Be sure to include a heat shield, but empty out 2/3 of the ablator in the VAB. 2. Put on an orbital insertion/ transfer stage consisting of 3/4 of an orange tank with a Poodle. Add a fairing to the top of this stage (below the decoupler) and enclose the lander. 3. Add a lifter stage with two or more orange tanks on top of a Mainsail. Keep adding fuel tanks until the TWR is just below 1. 4. Add two or more Kickbacks with radial decouplers and nose cones, then thrust limit them in the VAB to achieve an initial TWR in the 1.3 - 1.4 range. Make sure that the TWR of the center stack is at least 1.2 when the SRBs burn out. 5. Check staging and launch!

Not sure how to take that, but OK. gorebello, if you want to largely keep the rocket design you have, the easiest improvement you can make is to put more fuel on each of the radial stacks. Put an orange tank on each of the Twin Boars (with a nose cone on top) and then add a white tank and a nosecone on each of the radial Mammoth stages (after tweaking the struts a bit). Delta V should go up a lot.

Looks pretty overbuilt and unaerodynamic. All the scanning satellites appear to have LV-Ns, which is overkill for the small size of the fuel tanks - try a Spark instead. In terms of the lifter, your TWR is way too high. Arrange it so you have one central stack, with both it and all the radial stacks having at least two or three white tanks on top of each Mammoth. Here's a lifter I made a while back. It gets two white tanks (160+ tons) into orbit, which ought to be plenty to get a 36 ton payload to Jool. You can pick it up at KerbalX here: http://kerbalx.com/norcalplanner/200K-Fueler-LF-Mk11

Did this one a few months ago - goal was to land a 1,000 ton ship on the Mun, sent up in a single launch. My computer finally forgave me a week ago. Stock except for MechJeb. Ascent was manual. Descent used SmartASS to hold surface retrograde when coming in for a landing.

With docking ports and KJR, you can simply stack the satellites without any other reinforcement. Examples below.

Three letters - KJR

Meithan, Thanks for showing your ships and for the offer on the challenge. I'll try to carve out some free time to come up with a ruleset which will work. Then we can all start comparing apples to apples with our Cheap and Cheerful designs. :-) - - - Updated - - - Slashy, That's pretty much what I ended up doing - see the last part of the imgur album I posted. The last craft uses a 2.5 stage design where the last stage only has 600 m/s of delta V. Everything else is recovered with StageRecovery.

More StageRecovery Information and Examples I've assembled an imgur album showing a few different scenarios. Essentially, if you decide to use StageRecovery, recover everything you can. It's a net improvement of 250 to 300 funds per Kickback to place a Mk16-XL on top of each one instead of leaving them bare. Also recover your LFO tanks and engines if they'll be staged while the rocket is going less than 2,000 m/s in atmosphere. I created a rocket with a 167+ ton payload, similar to Alshain's, to use as a testbed. Without StageRecovery and without any parachutes, the lifter portion of the rocket costs 137,600 funds, for a rate of 820.3 funds per ton of payload to an 80 km orbit. For the StageRecovery rates, take a look at the album. Takeaway - StageRecovery is a gamechanger which will drastically reduce the cost to orbit if you choose to use it, provided you design and fly your rockets in a way that is compatible with the recovery mechanic.

OK, finally back at the computer. It was actually odd with the modified version of Slashy's rocket - whether I had no chutes or 8 chutes, I always seemed to get into an 80 km orbit with around 180 m/s left in the tank. I was flying everything manually, so maybe I was just getting better with that rocket - still, it seemed to be pretty insensitive to the additional 0.8 tons and additional drag in the first stage. Now the plan is to play around with both StageRecovery and the stock recovery mechanic, and try to get a better handle on when it makes sense and when it doesn't.

So here's what I did that caused me to change my position on recovering Kickbacks using StageRecovery. I took Slashy's rocket, the cheep31, and modified it a bit. The cheep32 simply removed the Rockomax adapter, to reduce cost a little bit. That rocket cost 46,956 funds, and didn't have any appreciable change in performance from the original version. A few iterations later, the cheep34 had eight radial parachutes on it, which added 3200 funds in cost, driving the price up to 50,156 funds. Recovery of the bottom stage (7 Kickbacks, Rockomax decoupler, 2 Delta fins, and the 8 parachutes) was 115.44 km from KSC. Terminal velocity from the 8 parachutes was 7.95 m/s. At that distance and speed using stock StageRecovery settings, the recovery percentage is 82.8%, or 10,710 funds out of the total value of 12,930. Net cost of the rocket after the recovery was 39,446 funds. That's 7,510 funds cheaper than the version without the parachutes. Clearly more research is warranted and photos need to be put up, but it's late and I need to get up early in the morning. More information (including photos) should be posted tomorrow.

STOP THE PRESSES! Breaking news story... It makes sense to recover Kickbacks using StageRecovery! More info at 11.

Alshain, That's my gut feeling too, but I'm still going to play around with it a bit to see if I can improve on any of the Rules of Thumb I've already come up with.

celem, Thanks for the feedback. Regarding your question, it's been awhile since I've used Stage Recovery - I'll fire it up and make sure it still works the way I remember it does, then amend that post as necessary.

Sanic, It works OK, but it's not as good as it could be. Any time you have an LFO engine that could be firing that currently isn't, you're giving up some efficiency. From a monetary standpoint, the cost of radial decouplers adds up quickly - if you're firing the SRBs first and then the LFO engine, save yourself some funds by making the entire first stage SRBs and then use a single stack decoupler. Doing it this way will also reduce drag caused by radially mounted decouplers and struts, and nearly eliminate any chance for SRB staging mishaps. If you want to post a photo of your rocket, I can probably provide some better comments. The next (and possibly last) main post is going to have to do with rocket geometry and numbers - TWR, ratio of solids to LFO, how best to arrange the various parts for lower cost and higher performance, etc. I'll make sure to include an example that compares stacked SRBs to radial SRBs.

TheXRuler, Sorry - I didn't realize I had left you hanging on something. The question in my mind would be "Is the reactor from KSP-I going to be used in any fashion to increase the score for the station (i.e., generating power for a modded engine to get it to a distant location, or powering an ISRU converter to create fuel which will increase the mass of the station before calculating the the final score)?" If the answer is no, especially if you're doing this in a career save and really want it for further development of your space program as opposed to pumping up your score, then I think it wouldn't be out of line to call the reactor cargo for the purposes of the challenge. Glaran, what do you think?

9. Stage Recovery Recovery of dropped stages, up to and including SSTO rocket lifters, can reduce funds expenditures dramatically for your space program. It can also result in additional costs, both in-game and in real life. Here are the Cheap and Cheerful Rules of Thumb for Stage Recovery. RoT 9.1 - Recovery of lifter stages can reduce the amount of funds per ton of payload to orbit, but it isn't for everyone. Choosing to recover stages represents a conscious choice to move the needle closer to "Cheap" and further away from "Cheerful". It will require more time, patience, and piloting skill to achieve recovery success at a high level. Because each launch and recovery will take at least twice as long as a launch with a disposable rocket, it will reduce the amount of launches you'll be able to do during a KSP play session. (It's very similar to RSS in that regard.) Weigh the impacts to your sanity and your available KSP time before committing to a high level of recovery in your space program. RoT 9.2 - Recover your lifter parts as close to KSC as you reasonably can. If you're a reentry pilot extraordinaire and can land your recoverable stages on the launch pad or the runway, you'll achieve the lofty goal of 100% funds recovery for that stage. For the rest of us, it's better to just try to get within a couple of kilometers of KSC, which will get you 95% recovery with a much bigger target to aim for. This means that your lifter has to have enough stamina (particularly electricity) to orbit Kerbin at least once before landing. Including airbrakes on your rocket can you help fine-tune your descent (especially along the E-W axis) and achieve a landing closer to KSC. RoT 9.3 - Partial recovery is a viable option. Feel free to discard SRBs and only recover the LFO core. Recovery is not an all or nothing affair. It's generally more worthwhile to recover the core of your lifter, with the expensive LFO engines, than it is to recover cheaper parts like SRBs. (SRBs have an additional strike against them in that they nearly always go into a suborbital arc, landing far away from KSC for a lower recovery percentage.) Don't be afraid to split the baby and go with a partially recoverable rocket, which can move the needle back toward "Cheerful". Discarding SRBs without concern for recovery also allows for a better balanced, easier to fly rocket due to the TWR drop after staging. RoT 9.4 - Balance the cost of recovery hardware against the cost of the recovered stage. Consider the full cost of the required recovery hardware, including funds, weight, and drag, when deciding whether to recover a stage. We'd all agree that putting a Mk-16XL parachute (850 funds) on top of a Hammer (175 funds when empty) makes little sense. Even the largest SRB, the Kickback, is only worth 1,140 funds when empty. When combined with the need for a probe core if the stage will drop out of physics range while in atmosphere, along with the reduced recovery percentage for a stage that lands hundreds of kilometers from KSC, only the largest, most expensive stages (typically LFO cores and asparagus stages) are worthy of recovery. The only real exception to this RoT is when using Kerbal Construction Time, where there is additional value assigned to recovered parts (time saved in building the next rocket), no matter where they come down. RoT 9.5 - SSTO rockets can be appealing on paper, but they have drawbacks - and you have to stick the landing. A pure SSTO rocket offers the potential for the highest level of funds recovery, but there are some big drawbacks. They're more expensive to construct initially than a disposable or partially recoverable rocket, and have a lower payload mass fraction. It can be difficult to fly an SSTO rocket to orbit with an efficient ascent profile when there's no staging and a constantly increasing TWR. The lack of a heat shield means you have to have a shallow reentry profile, which can make accurate landings more difficult. And because SSTO rockets tend to be tall with a narrow base, it's imperative to land someplace flat (yet still near KSC). If the rocket tips over, it's likely that at least some of it is going to explode, which will negatively impact the economics of your lifter. RoT 9.6 - Mods can make recovery easier. Some mods, particularly Stage Recovery, can help recover stages that would otherwise be lost. They can also partially automate the recovery operation itself, so you don't have to go into the Tracking Station after every flight and manually recover dropped parts. Stage Recovery is especially useful when used in combination with Kerbal Construction Time - it's almost as if both of them were created by the same modder... - - - Updated - - - Slashy, I've downloaded your craft, and will give it a whirl soon. My own experiences with SRB-only first stages have been somewhat mixed, so I'm curious to see what you've come up with. - - - Updated - - - I looked too, and I didn't see one for the 1.0 era. The best match I could find is the 0.24 Cost-Effective Lifters Challenge, but that didn't have a very high level of participation. There was also the Heavy Lift Challenge a while ago, but that was about cheaply lofting a particular payload (orange tank plus some bits) than a pure funds/ton measurement for just rockets. If someone wants to run a 1.0.4+ Cheap and Cheerful Lifter Challenge, that would be fine by me. I'd even be happy to come up with the rules, but someone else would have to manage it and score the entries. My schedule is somewhat unpredictable these days with less free time, and people tend to get cranky when you don't score their entries for three or four days.