Norcalplanner

It's also a viable idea to put some twitch engines up on the capsule itself, where they are fully occluded from reentry heating. My Bluebird crew transporter uses this design - I'll post a photo once I'm at my computer.

I sent a probe mothership to Mars in RSS, carrying four aerodynamic landers for Mars proper, two landers for Phobos and Deimos, and one monster polar satellite with every orbital sensor that I've unlocked in this career (including those from ScanSat and Dmagic). Time will tell if this is a successful trip or not...

As an aficionado of both complicated board games (ASL, Advanced Civ, etc) and computer games, my standing joke is that I should just tell people that I'm fishing instead of gaming. Think about it how much more socially acceptable the following statements are about fishing instead of gaming: I took a week off work to go fishing. I bought some new fishing gear. I subscribed to a fishing magazine. I'm watching a TV show about fishing. I'm reading up on how to get better at fishing. I'm talking to people online about fishing. I spent a year putting together my current fishing rig. I flew to another state to go fishing. And on and on and on...

I have hit the wrong key while docking, inadvertently creating debris which subsequently hit and damaged another part of the station. Oops.

I did one last set of runs before removing FAR and getting back to my career. For this set, the rocket was identical to the other FAR runs, with the SRBs set at 75% for an initial TWR of 1.53 for all runs - the only variable is the amount of tipover. I used the exact same technique used in the comparable stock aero version in an earlier post (30 m/s vertical, then tip to the east) to allow a direct comparison. As with before, MechJeb doesn't tabulate drag losses with FAR installed. A Degree Makes a Difference - 1.53 TWR, FAR Edition Turn Angle Gravity Losses Delta V to Orbit Delta V Remaining 5 degrees 1,357.7 m/s 8,787.5 m/s 1,550 m/s 6 degrees 1,419.2 m/s 8,846.7 m/s 1,490 m/s 7 degrees 1,253.0 m/s 8,694.8 m/s 1,641 m/s 8 degrees 1,196.5 m/s 8,657.9 m/s 1,680 m/s So the big shocker here is that 6 degrees is less efficient than either 5 or 7. I repeated the runs for 5, 6, and 7 degrees, and got comparable results each time. I'm honestly at a loss to explain this. The only thing I can think of is that shapes of the ascent curves for 5 and 6 degrees lie on either side of some crossover point in terms of drag, atmospheric density, critical mach number, or something else that I don't fully understand. If anyone well-versed in FAR or real life aero wants to weigh in, I'd love to hear what you think might be going on.

Tylo needs something in addition to whatever you're using on other moons. It could be drop tanks, asparagus stages, or a separate landing stage similar to the Apollo LM.

Streetwind, thanks for the props. The standard atmosphere in RSS was done by @OhioBob and it's supposed to be pretty good. Unfortunately, I don't know enough about it to speak articulately on the matter.

Any chance you could post a photo of your craft? It sounds like it's all LFO in the first stage. If so, you may want to try reallocating the mass distribution between the stages so that the upper stage has more mass. You could also try reducing your craft down to three or so engines, and adding some SRBs for the initial boost off the pad.

Symmetrical separation with either three or four segments, depending on the configuration of the rocket below. I like the look of clamshells, but I've had them caught up on my payload one too many times. Never had a problem with three or four segments.

Here are the final versions of the runs using FAR. The only physical change made to the rocket is the addition of four small delta fins. Mass of the underlying rocket is kept the same (unlike the initial tests I mentioned a few posts ago). Data crunching was hampered by MechJeb not being able to capture the amount of drag losses with FAR installed, so all we're left with is gravity losses, delta V to orbit, and remaining delta V in the upper stage tank. I've summarized things in a table below. A Degree Makes a Difference - FAR edition Initial TWR Initial Turn Angle and Speed Gravity Losses Total Delta V to Orbit Delta V Remaining 1.18 5 degrees at 70 m/s 1,577.4 m/s 8,990.4 m/s 1,101 m/s 1.53 8 degrees at 35 m/s 1,253.8 m/s 8,695.6 m/s 1,641 m/s 1.87 12 degrees at 10 m/s 1,129.3 m/s 8,594.5 m/s 1,823 m/s While we don't have actual drag loss data, it's clear from the last row that drag is more of a factor with FAR. 12 degrees was the maximum tipover which made it to orbit, as compared to 14 degrees in stock RSS aero. Nevertheless, the data show that at least for this craft, only minor modifications were needed to function adequately with FAR installed. The 50% thrust ascent used identical settings as stock; the 75% thrust setting just needed 5 m/s of additional vertical speed before starting the tipover, and the 100% thrust setting required two degrees less tipover. It was also enlightening to see just how much drag was being shown on each of these craft - I was able to grab a screenshot right at Max Q during each ascent so you can see just how much drag was being generated. One final note - on a whim, I removed the two outermost SRBs, and gave the two remaining SRBs the slanting advanced nose cones. With the SRBs operating at full thrust at an initial TWR of 1.57, this smaller and cheaper version was able to get to orbit with an initial tipover of 7 degrees at 38 m/s. Doing so incurred gravity losses of 1,396.6 m/s, cost a total of 8,803.3 m/s of delta V, and made it to orbit with 1,097 m/s left in the tank. These numbers are comparable to the 50% thrust option, at a lower cost and weight.

I think you may be right. I'll do a few more runs with everything back where it was. TWR will be a little lower in the first stage due to the mass of the fins, but the upper stage will be identical.

Laie, The problem you describe with a rocket losing control during staging is one of the reasons why I've gravitated towards using SRBs in nearly all my rockets. It allows a larger first stage LFO core, so the gimbaled engine keeps firing and provides control during the first staging event (which is ditching the SRBs). When that center LFO core finally runs out a minute or two later, the atmosphere is so thin aero is no longer an issue. And what you're describing using the clickers with SmartASS is exactly what I'm doing. I'll wait until the vertical velocity is where it needs to be, then I rapidly click the minus button for however many degrees of initial tip I need. It smooths out the control inputs just a bit, as you mention. And I fully acknowledge that this test rocket isn't the most realistic - it has a crazy powerful upper stage, with an initial TWR of 1.87. Probably not the best example in hindsight, but it certainly helps keep the trajectory flat in the latter part of the ascent.

Thanks everyone for the kind words and interest in this. Just to post a brief update with FAR - I've spent the last few hours with FAR installed, stock settings, and aerodynamic failures enabled. I tried to replicate the results I was getting with the stock-ish RSS aero. Every single ascent I tried with that craft ended in failure and rapid unplanned disassembly. It seemed to "bobble" (for lack of a better word) while going transonic, drift off pro-grade, and disassemble. (Full disclosure - I'm also running Kerbal Joint Reinforcement, and am not running Deadly Reentry, Real Heat, or anything else which might contribute to my rocket breaking up.) However, I discovered an easy two-part solution, which works at least with this craft: 1. Add fins. I added six of the delta fins around the base of the LFO core. This turned the "bobble" into something which was barely noticeable. To keep the weight approximately the same for the tests with fins added, I emptied out the ablator and monoprop. 2. Reduce the initial tip eastward by one degree. This is enough to account for the greater drag down low imposed by FAR. That's it! With those two modifications, the craft got to orbit again just fine, with gravity losses only slightly greater than in stock RSS aero. I'll post some more images later tonight, along with additional data. Maybe some of the FAR-types can help translate all the numbers and colored lines which are in some of the screenshots. - - - - - Edit - As suggested by THX1138, I added back in the ablator and monoprop. The number of fins was reduced to four, and new runs were made. See the post a few below this one for more info.

I don't think these numbers are universal, so I wouldn't put a lot of stock in them for other situations. For example, this craft is pretty clean aerodynamically, with no fins, solar panels, struts, or other radially- mounted equipment. What I think IS universal is that altering your ascent profile to minimize gravity losses instead of worrying about drag losses is a good idea.

Check out the Cheap and Cheerful Rocket Payload Challenge I ran back in 1.0.5 for cheap disposable lifter ideas. Many of the entries were below 700 funds per ton of payload; a couple even got below 600 funds/ton. You can also find a lot of good ideas for cheap lifters in the tutorial linked in my signature.

Yep. It was that initial difference between 5 degrees and 6 degrees which was the eye opener. In exchange for losing 6.2 m/s to increased drag, gravity losses were reduced by 180.6 m/s, and the whole craft got to 250 km orbit for 191.6 m/s less delta V.

To give a better idea of where the title of the thread came from, here's some data from the runs at an initial TWR of 1.53. All ascents went straight up until 30 m/s was reached, and then an initial tip to the east was dialed in with SmartASS. A Degree Makes a Difference - 1.53 TWR Initial Turn Angle Drag Losses Gravity Losses Total Delta V to Orbit 5 deg 63.4 m/s 1,622.0 m/s 9,047.0 m/s 6 deg 69.6 m/s 1,441.4 m/s 8,855.4 m.s 7 deg 76.6 m/s 1,306.4 m/s 8,720.3 m/s 8 deg 84.2 m/s 1,208.3 m/s 8,627.4 m/s

SpaceY has SRBs in 1.875m, 2.5m, and 3.75m diameters, in a variety of lengths. When the center stack is 5m or 7.5m, then 2.5m SRBs look great.

Never give up, never surrender!

Based on an idea born in another thread, I decided to do some experiments in RSS (which I'm currently using as my career, with SMURFF - no RO) to look at TWR, drag losses, gravity losses, and ascent profiles. I created a basic rocket with four Kickbacks, then simply thrust limited the Kickbacks to 50%, 75%, and finally 100%. After an initial tip to the east, SmartASS would hold the craft on a surface prograde vector. Once the navball switches to an orbital reference, SmartASS changes to hold orbital prograde until the Ap is 250 km. MechJeb is then told to circularize at AP. After conducting 18 test runs, I've created an album with the best run at each thrust level, posted below. It was amazing that a single degree change in the initial tip can make a big difference - in one case, reducing gravity losses by over 100 m/s. It was also eye-opening to see just how small the drag losses are compared to the gravity losses. Conclusions based on all this: 1. Launch with an initial TWR between 1.5 and 1.9. 2. Don't worry about drag - gravity losses are much larger and more important. 3. Ignore the flame effects. 4. At higher thrust levels, crank it to the east immediately after launching, and be precise about it. 5. Try to keep vertical velocity below 800 m/s. If it's over 1 km/s, you're going to have noticeably higher gravity losses. 6. Getting a rocket to orbit in RSS for less than 9 km/s of delta V is very doable. Using less than 8.6 km/s is a harder but still achievable goal. UPDATE: After making all these ascents in RSS, I redid the tests in stock with a slightly different rocket (but same concept) to see what was the same, and what was different, You can find the stock version here. UPDATE 2: After editing this OP, the embedded imgur album disappeared. You can find the album here.

Poodle works great as an orbital insertion / transfer engine. But it is definitely overkill for most standard size landers, where the Terrier is more appropriate.

So I did a simple test using the readouts from MechJeb for gravity and drag losses. (These have to be selected manually and added to a window.) Full info is in the descriptions. TL;DR - Higher TWR and a more aggressive start to the gravity turn will result in lower delta V cost to orbit, and lower total losses from gravity and drag combined.

I'll usually put an upside down 2.5m to 4x1.25m adapter on top of the rocket, stack the satellites on top of the 1.25m attachment nodes with docking ports or decouplers, then put a 2.5m fairing beneath the adapter to enclose everything. I also like putting Jr docking ports on my satellites for the reasons you mentioned, plus you can use them in lieu of a stack decoupler. I've launched up to 8 satellites and probe landers in this fashion on a single rocket. If you wanted the carrier craft to be manned, I suppose you could put a 2.5m lander can in the stack also.

When bits of solar panel flutter away with your discarded fairing because you were trying to keep your fairing as small as possible.

The best I could do is just under 32,000 m/s with Buster. It was a challenge to see how fast you could go before leaving Kerbin's SOI, so the thrusts are all above 0.5. This was back in 0.90, so not much concern was given to aerodynamic considerations.