GoSlash27

I'll side with Hodo on this one. I do not recommend monkeying with AoA until *after* you've got static balancing and dynamic balancing down. It'll just complicate things while you're still learning the basics. Best, -Slashy

If memory serves, it was automated, but did not use "computers" in the modern sense. They instead used simple servomechanical systems to provide feedback for the control loop. Best, -Slashy

KristopherKerblumbus, Check out my SSTO spaceplane tutorial here: http://forum.kerbalspaceprogram.com/threads/102182-So-you-want-to-build-a-space-plane-%28-25-stock%29 If you need further help with how to design your spaceplanes to be not-lawn darts, just give a holler. Best, -Slashy P.S. If you're using FAR or NEAR, my tutorial won't actually work, since it's a turbojet/ booster design, but the aerodynamic and balance principles still hold true.

Your fuel tanks need to be in the middle of the plane. That way as the fuel drains, your CoM won't shift. If you have multiple tanks, stack them laterally, but not longitudinally. If you must stack tanks longitudinally, place the center of the junction of tanks in the center of the plane. The CoM will shift as the fuel drains, but will wind up back where it started when the fuel's gone. For 3 longitudinal tanks, (A-B-C from front to back) you can use fuel line to keep them balanced. A->B, C->B, and B-> engine. Use weight and balance to get the CoM right in the middle of the tanks. A large mass such as an engine can be counter-balanced by a lighter mass on the other side by moving the lighter mass farther away from center. Center of lift is right where your wings attach. Place them either exactly in the middle of CoM *at it's furthest aft point of travel* or just behind. If you follow these simple rules, you'll have a perfectly balanced plane every time. Best, -Slashy

This is also true. That energy loss must be paid for with additional fuel and tankage. This chart shows the point at which the penalty for low t/w in fuel and tankage offsets the penalty for high t/w in engine mass. Best, -Slashy

A lot of strong takes here. I'll go with USS Archerfish.

My multiengine tutorial example spaceplane http://forum.kerbalspaceprogram.com/threads/102182-So-you-want-to-build-a-space-plane-%28-25-stock%29 would net 10 points for orbit & dock =10 10 points for cost < 5k =10 (assuming I understand the rules correctly) 5 points for SSTO =5 3 points for medium docking port =3 5 points for manned =5 2 points per extra kerbal x25 =50 4 points for safe return =4 87 points. Best, -Slashy

The fuel tanks need to be in the center of the plane. That way, as the fuel drains the CoM doesn't shift. After that, it's a straightforward "weight moment" problem. You can counter-balance a heavy chunk (like an engine) with an equal mass at the same distance or a lighter mass at a farther distance. 1/2 the mass and twice the distance will balance perfectly, or 1/10 the mass at 10x the distance, etc. You multiply the mass by the distance for each part, then add and subtract these products to get zero. So without using the lift/mass markers (you should always use lift/mass markers), it's still possible to eyeball a balanced design. The wings provide lift at the point where they attach, so that's also easy to eyeball. If worst comes to worst, you can fulcrum- balance a design by building it without the wings and placing a control surface under the fuel tank to act as a fulcrum. Launch/ check the balance/ recover/ adjust until it balances. I used to do that for my ion gliders back in the day, which were extremely large and could not use control surfaces due to the rules. HTHs, -Slashy

I strongly disagree with everything said here (except for the last sentence). The XM-G50 radial intake is all- around the most effective and efficient intake in the game. Reference: http://forum.kerbalspaceprogram.com/threads/97615-0-25-KSP-air-intakes-compared And you really don't *need* to air-hog if you've properly matched the number/ type of wings and turbos to your spaceplane. My workhorse SSTO uses 4 XM-G50 intakes and a single turbojet and nets 50% payload fraction. A single ram or shock cone coupled with 2 XM-G50s is plenty sufficient to feed a turbo for an SSTO spaceplane. Best, -Slashy

arkie, Results are up for my study, and they're surprising in one sense, and not surprising in others: http://forum.kerbalspaceprogram.com/threads/105422-Ideal-T-W-ratios-for-airless-body-launch-%28KSP-90%29 For all engines on Gilly, lowest mass is achieved in the 2-3 t/w range, while for lowest cost they're in the 1-2 range. On Tylo, all these numbers drop considerably, with lowest mass in the 1.5-2.5 range and lowest cost in the 1-1.8 range. I didn't expect the numbers to work out so low, but the kicker is efficiency holds steady for optimal solutions on all airless bodies. An engine that yields the lowest stage mass at 92% efficiency on Gilly will also yield the lowest stage mass at 92% on Tylo. Just thought I'd pass that on and thank you again for all your work on this model! Best, -Slashy

I was at first, but decided against it. These 2 moons represent the absolute max and min for these figures. All other bodies will have ideal t/w between these 2. And of course I can't model drag. Best, -Slashy

That it does. But in some cases the cost and/or mass of the wasted fuel is less than the cost and/or mass of the additional engines. This is especially true for heavy, expensive, and highly- efficient engines. Best, -Slashy

[TABLE] [TR] [TD][/TD] [TD] Gilly[/TD] [TD][/TD] [TD] Tylo[/TD] [TD=width: 86][/TD] [/TR] [TR] [TD][/TD] [TD] Mass[/TD] [TD] Cost[/TD] [TD] Mass[/TD] [TD] Cost[/TD] [/TR] [TR] [TD]LV-1[/TD] [TD]2.5[/TD] [TD]1.2[/TD] [TD]1.8[/TD] [TD]1.0[/TD] [/TR] [TR] [TD]LV-1R[/TD] [TD]2.5[/TD] [TD]1.1[/TD] [TD]1.8[/TD] [TD]1.0[/TD] [/TR] [TR] [TD]24-77[/TD] [TD]2.9[/TD] [TD]1.4[/TD] [TD]2.1[/TD] [TD]1.2[/TD] [/TR] [TR] [TD]48-7S[/TD] [TD]3.0[/TD] [TD]1.7[/TD] [TD]2.3[/TD] [TD]1.4[/TD] [/TR] [TR] [TD]LV-909[/TD] [TD]2.1[/TD] [TD]1.5[/TD] [TD]1.6[/TD] [TD]1.3[/TD] [/TR] [TR] [TD]Mk-55[/TD] [TD]2.3[/TD] [TD]1.8[/TD] [TD]1.8[/TD] [TD]1.5[/TD] [/TR] [TR] [TD]RAPIER[/TD] [TD]2.4[/TD] [TD]1.4[/TD] [TD]1.8[/TD] [TD]1.2[/TD] [/TR] [TR] [TD]LV-T30[/TD] [TD]2.5[/TD] [TD]2.1[/TD] [TD]1.9[/TD] [TD]1.7[/TD] [/TR] [TR] [TD]LV-T45[/TD] [TD]2.3[/TD] [TD]2.0[/TD] [TD]1.8[/TD] [TD]1.6[/TD] [/TR] [TR] [TD]Aerospike[/TD] [TD]2.2[/TD] [TD]1.4[/TD] [TD]1.7[/TD] [TD]1.2[/TD] [/TR] [TR] [TD]Poodle[/TD] [TD]2.2[/TD] [TD]1.8[/TD] [TD]1.7[/TD] [TD]1.4[/TD] [/TR] [TR] [TD]LV-N[/TD] [TD]1.4[/TD] [TD]1.1[/TD] [TD]1.1[/TD] [TD]1.0[/TD] [/TR] [TR] [TD]Skipper[/TD] [TD]2.7[/TD] [TD]2.0[/TD] [TD]2.0[/TD] [TD]1.7[/TD] [/TR] [TR] [TD]Mainsail[/TD] [TD]2.8[/TD] [TD]2.1[/TD] [TD]2.1[/TD] [TD]1.8[/TD] [/TR] [TR] [TD]KR2L[/TD] [TD]3.2[/TD] [TD]1.7[/TD] [TD]2.4[/TD] [TD]1.5[/TD] [/TR] [TR] [TD]KS25x4[/TD] [TD]3.1[/TD] [TD]1.7[/TD] [TD]2.3[/TD] [TD]1.4[/TD] [/TR] [TR] [TD][/TD] [TD][/TD] [TD][/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD][/TD] [TD][/TD] [TD][/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]0-10[/TD] [TD] inf[/TD] [TD]1.3[/TD] [TD] inf[/TD] [TD]1.0[/TD] [/TR] [TR] [TD]RV-105[/TD] [TD] inf[/TD] [TD]1.5[/TD] [TD] inf[/TD] [TD] 1.0 [/TD] [/TR] [TR] [TD]Linear[/TD] [TD] inf[/TD] [TD] 1.3[/TD] [TD] inf[/TD] [TD] 1.0 [/TD] [/TR] [TR] [TD][/TD] [TD][/TD] [TD][/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]PB-Ion[/TD] [TD]1.1[/TD] [TD]1.1[/TD] [TD]1.0[/TD] [TD]1.0[/TD] [/TR] [/TABLE] - - - Updated - - - All, This table shows the ideal t/w ratios for launching from airless bodies using each of the engines available. For obvious reasons, I didn't bother listing the solid boosters. Thanks to arkie 87's outstanding work on modeling DV losses on airless body launches, I was able to model each engine launching a suitably sized rocket and determine these crossover points. T/W for ideal vehicle mass: This is the point at which adding or removing engines to alter the t/w will result in an increase in overall launch vehicle mass. T/W for ideal vehicle cost: This is the point at which adding or removing engines to alter the t/w will result in an increase in total launch vehicle cost. These numbers should not be considered design targets in and of themselves, but rather show where the crossover point exists. You would not want to add mass or limit your throttle just to meet these ratios. A couple notes... *All modeled launchers assume the most mass- efficient tanks for their type and those tanks are assumed to be infinitesimally scalable. This is not true in real life, so these results will tend to the high side for small scale launchers. *The PB-Ion does not take into consideration the mass and cost penalties of additional solar panels and batteries required to support additional thrusters. Best, -Slashy

I don't use NEAR, but sounds to me like your vertical tailfin is too small and not far enough back. Best, -Slashy

There's no real point to this, but since this contest inspired me, I figured I'd share it here. http://wikisend.com/download/176042/silliness.craft This little toy plane doesn't do anything useful, but it's fun to bomb around the KSC with. Set trim to 4 down, hit space bar to launch, and release the hounds! http://i52.photobucket.com/albums/g13/GoSlash27/KSP/silliness4_zpsd294db4e.jpg altitude 288m, distance 15.5km

Ladies and gentlemen, we have a winner! All stock 2 Kerbals doesn't break at warp lands/ takes off safely and easily in rough terrain no infiniglide (it doesn't have any control surfaces!) goes well over 2km/sec at 36 km altitude no cheats or part clipping achievements: Long range biome hopper safe to fly Part count 14 cost $12,032 http://wikisend.com/download/259628/lil' plane.craft This little bugger's *got* to be useful for something! Best, -Slashy

I've downloaded the new version, but since I've already begun my work by doing a hatchet job on v1.0, I think I'll stick with that. So far, all of my t/w recommendations for Gilly are in the 2-3 t/w range for minimum mass and 1-2 range for minimum cost. I'll be checking all engines on all airless bodies to see how they affect the results. Thanks again! -Slashy

My suspicion is that in all cases a 2 stager is preferable, but I haven't confirmed that yet. It has a lot to do with how you approach the descent stage. If you're using a zero descent rate profile, then clearly you're interested in absolute minimum mass for all phases of the mission. There may be some cases where ditching the empty tanks is cheaper than a decoupler, but I don't know yet. If, OTOH, you're running with a suicide burn or reverse gravity turn, then you're willing to expend more mass in the descent stage. And in that case, why would you *not* dump that extra weight for the trip home? This may not be a question that can be answered mathematically; may just come down to player preference... Best, -Slashy

One major factor: Spaceplanes have a large safety factor in the event that something goes wrong during the launch/ climbout. A spaceplane can usually fly (or at least glide) to dry land, thus recovering most of the funds and *very importantly* not killing Kerbals. A vertical lifter... you can separate the cargo and recover the launcher, but the payload itself is a write- off.

This is actually part of the question I'm researching right now. Neglecting cost, it comes down to mass. I don't have any definitive answers just yet, but I should within the next couple weeks. Best, -Slashy

^ This is all true. The STS did everything it was called upon to do; probably more in terms of raw tonnage and numbers than most other launch systems combined. Not the most economical or efficient system, but it was definitely effective and admired. Best, -Slashy

All of this. If I'm just doing a one-off launch, I'm not going to bother building an expensive reusable launch system for it. Makes more sense to slap together a cheap, disposable rocket. A vertical mass lifter like what I've shown here is really best for chucking outsized and massive structures that don't conveniently fit in a spaceplane. This would be stuff like chunks of space stations/ ships/ etc. A spaceplane is generally preferable for moving supplies and Kerbals to/from orbit. It doesn't operate quite as cheaply as a vertical mass lifter, but it gives you a lot more safety options if something goes wrong during the launch, whereas with a vertical mass lifter the payload would be doomed. Plus it lands on the runway. Needless to say, my Kerbals are forbidden to ride anything into orbit other than spaceplanes. Best, -Slashy

Kartoffelkutchen, Sure thing. It's actually much easier than what you've put yourself through. 12.5/4.50= 2.78 <-- wet/dry ratio now take the natural log of 2.78 ln(2.78)= 1.02 Now multiply that by 9.82 and your Isp 1.02*9.82*390= 3,910 m/sec. (rounded to 3 digits) That's really all there is to it. Best, -Slashy

wanderfound, A little background: He was trying to build a spaceplane according to my tutorial, not realizing that while it would be just fine in stock, it wouldn't work for FAR. That's why I asked you to help out; you're the FAR spaceplane guru. Best, -Slashy

No problem. Glad you're on the right track! To change the thread to "answered", just edit your OP in advanced mode. It'll give you the option to change it. Best, -Slashy