AeroGav

What's the most common one you use on your designs / what'd you recommend for a NEWB? All RAPIER Pros - fully reusable, fuel always drains evenly, good (best?) payload fraction to LKO, high thrust weight ratio Cons - low ISP in space , not optimal for missions beyond low orbit 2 RAPIER 2 NERV Pros - fully reusable, can fly to space without oxidizer. Symmetrical layout. Decent delta V. Once fuel type for air breathing and rocket engines. Cons - one nerv can only lift 15 tons whereas a single rapier can do twice that, at a pinch, so you are carrying one more rapier than you really need - and those suckers are heavy. 2 tons each. Also the NERVs drain fuel front to back of the stack like a rocket , so won't take from wing tanks and try their hardest to mess up CG 1 RAPIER 2 NERV https://kerbalx.com/AeroGav/Astrojet-Citation Pros - fully reusable, can fly to space without oxidizer. Symmetrical layout. Good Delta V Cons - poor performance when subsonic, hard to bust through the sound barrier. Swapping RAPIER for Whiplash improves this at the expense of a little delta V though lower airbreathing max speed. 1 RAPIER 2 NERV 2 disposable panthers (coupled to rear of NERVs) Pros - solves the poor subsonic performance of the above layout, nice controllable climb not as banzai as a pure RAPIER/Whiplash design at high speed. Cons - not fully reusable, though Panthers are only a third of the price of a RAPIER and enable to sort of missions you'd need a pretty big rocket for. https://kerbalx.com/AeroGav/K211-Tundra-Goose NERV + disposable whiplash on decoupler behind NERV Pros - very high delta V, can go to Duna and back, since you're not dragging the dead weight of air breathing engines once they outlive usefulness. Cons - not fully re-suable, though still only 2000 kredits a pop https://kerbalx.com/AeroGav/whippynerv NERV + disposable RAPIER https://kerbalx.com/AeroGav/Astrojet-Citation-X The last word in performance. Re-using engines is for peasants.

1. The thrust output of jet engines in this game is modified by two factors a) atmospheric air density and b) speed. As the air gets thinner you loose power. On the other hand, you get faster engine output increases , up until a peak, then starts to tail off again. There's a lookup table inside the engine's config file that tells it how much thrust to loose as air density falls off . For the RAPIER engine it's pretty shallow up to 10km. From 10km to 20km it looses thrust more quickly, if you start getting well supersonic at these altitudes then the thrust gain from the additional speed offsets the loss from thinner air, as does decreasing drag. Above 20km things start weakening rapidly no matter what. In terms of speed, the RAPIER peaks at Mach 3.75 , or 1130m/s. If you push on to mach 4.5, or 1380 m/s, thrust falls back to 80% of maximum. After that there's a sharp kink in the curve and the decline is rapid - thrust falls to 0 by mach 6. 2. More intake will not help. You have 2 adjustable ramp intakes and 2 pre-coolers, one pre-cooler is sufficient intake for a rapier and an adjustable ramp intake almost enough for 2 engines. Lack of intakes does not cause a gradual loss of thrust, it causes the engines to splutter and surge, pop and bang. When the engines splutter, it only affects one engine at a time, making your craft weave from side to side. 3. You've got the right general idea in climbing up a bit before trying to go supersonic. The exact altitude it's best to do that at depends on how much lift and drag your design has - the more lift and drag, the higher up you should be before trying it. For example, most of my designs are incapable of going through the sound barrier below 7.5km. Below that altitude, drag rises faster than engine thrust with increasing speed. So, I pitch up to stay below 260 m/s. However, if I go much above 12km subsonic, two problems arise. As the air gets thinner, there is less lift, normally the speed also goes up to compensate, but if you're not getting faster, the only way to keep sufficient lift is to raise the angle of attack (nose up angle). Beyond a certain point this leads to a lot of drag. The other problem of course is that your engines are loosing power because you're getting into thinner air without also getting faster to give some ram air effect. Generally when I'm having to raise the nose 8 degrees above prograde just to get enough lift , is when it's time to go supersonic. Drop the nose angle and light the nukes till i'm over 400 m/s, then i gently raise the nose again, and cancel the nukes. 4. I think you should talk in terms of Angle of Attack rather than pitch. Angle of attack is the difference between where the nose is pointing and your direction of travel. So if you have the nose pointing up at 13 degrees but the prograde marker shows an 8 degree climb, this means you have an angle of attack of 5 degrees. Pitch is just the angle of the nose. Telling me you have 15 degree pitch could mean - A) you have a really overpowered ship and are climbing at almost 15 degrees, at a high airspeed and a low angle of attack, not struggling for lift at all or B) you are are hardly climbing but are struggling badly for lift and are wallowing along in a very inefficient slow flight regime not much above stalling speed or C) you are actually descending at 15 degrees or more and have in fact already stalled Generally I fly targeting an AoA rather than a pitch angle. Manual flight with pitch trim I make a few test flights to find out how much nose up pitch trim (alt + s to add more, alt + w to reduce) is needed for my airplane to settle at about a 3-4 degree AoA if left to its own devices with SAS off. I set this before takeoff. I also use Alt F12 to open up the debug menu, go to the physics tab, check the "display aero data gui" box. Keep an eye on your lift:drag ratio as well as total drag and total thrust as you climb. I generally find that 3 degrees AoA gives highest lift:drag ratio below 160 m/s. Above that 4 degrees, supersonic we're talking 5 degrees, possibly more as you near orbital velocity. Above 200 m/s I start adding more pitch up trim to keep speed below 260. However, when the only way to keep the speed down is to increase AoA beyond 8, it's time to go supersonic instead. I toggle the nukes on briefly with an action group and remove the extra pitch trim, maybe even set prograde for a few seconds on SAS too. After that you're hanging on to the tiger by the tail. Try to level off at 18-20km to accelerate to 3.75 mach (1130m/s) , maybe even 1300 if you can do that without overheating (a shallow cilmb to 21-22km for this speed is ok). After that trim the nose up to gain altitude without getting any faster. When you can no longer get a worthwhile rate of climb without loosing airspeed, toggle the nukes back on. Note that above 20km most planes start get a bit squirrely, and tend to bob and weave. At this point it's acceptable to just lock in a good nose angle with SAS. SAS holds a nose angle but doesn't take account the curvature of the earth, so your nose will gradually rise. A quick tap on the W key if it starts rising faster (say more than 1 degree above your optimal AoA) than you want. With Mechjeb this is the easy way. watch this... https://www.youtube.com/watch?v=b6Ja7B2TCmE (note, mechjeb can't fly some planes off the runway, some of my other designs i need to take off first before engaging autopilot) Finally a quick word on your SSTO It looks nice, but is there too much fuel? Maybe that is why you can't get enough lift at only 10km, and why your are having trouble getting through the sound barrier. You need one NERV for every 15 tons of weight, and one jet engine for every 30 or so. Therefore take fuel out of your design till it weighs less than 30 tons and see how it goes. In a NERV spaceplane it's really hard to have more than 50% of it's mass as fuel and still be nice to fly, or even make orbit at all. At the other extreme I've flown stuff up there with only a 30% fuel fraction and been disappointed not to have much delta V left once in orbit. Air breathing engines are heavy btw (2 tons each) so putting them on decouplers can help if you're struggling. If you're taking that approach it's probably best to use whiplash rather than RAPIER since whippy's only cost 2000 each instead of 6000...

Here's a NERV/Whiplash ship flying from 18km to orbit. It carries 5 crew and is pretty loaded with extras like docking port, lifting engines etc. You can see that the NERV easily produce enough power though those airliner wings aren't really suited to this kind of thing and get pretty hot. It actually goes all the way to Minmus and back - although the fuel reserves look mostly depleted by the end of the video, the gauges only show what's in the tanks the NERV directly connect to. On part 3 you can https://www.youtube.com/watch?v=3nI-n0J262I see the remaining fuel get transferred in for the interplanetary leg. And yes, there is 55 units of oxidizer on this thing. It's for the Vernier engines only , which enable horizontal touchdown like this - https://www.youtube.com/watch?v=w6ZxVtZswh0 The above craft can be downloaded here - https://kerbalx.com/AeroGav/Astrojet-Citation A "hotter" version that sheds it's airbreathing engines for extra delta-v (enough for a return trip to Duna for 5 kerbals, with a bit of flying around on the red planet). https://kerbalx.com/AeroGav/Astrojet-Citation-X A minimalist staged nerv/whiplash airplane (from 1.05, landing gear may need an upgrade?) https://kerbalx.com/AeroGav/whippynerv ....and finally, uploaded just a week ago, a rapier/nerv spaceplane that can fly from the surface of Kerbin to the surface of Duna and come back. The only oxidizer is for the lifting engines https://kerbalx.com/AeroGav/Astrojet-Lancer

1:1 is not the same thing in an airplane as a rocket though. Less than 1:1 in a rocket means you start falling back to earth. In an airplane, TWR needs to be better than lift/drag ratio, that's all. So if lift drag ratio is 3 to 1 then so long as your TWR is better than 0.333 to 1 you can keep climbing. Or to express another way, thrust just needs to be higher than drag while in steady flight (one that isn't ballistically arcing downwards) Can you improve your L/D ratio by adding more or less wing? Adjusting AoA or your ascent profile? For supersonic flight 3:1 is great, but at 200m/s you should be seeing 6:1 or better. At 100m/s you can get over 10 to 1

Something that's worth discussing is the whole cargo SSTO concept. Now, if you use your space plane to launch a probe, and the probe explores space, then you aren't dragging air breathing engines, landing gear, wings etc. any higher in Kerbin's gravity well than low orbit, so that's a saving. But , mk3 cargo bays are incredibly heavy, very draggy, as are mk3 nose and tail sections/adapters/cockpits. These days I just prefer to have the space plane itself explore the Kerbol system. It already has wings (useful on laythe and duna), NERV engines, strong landing legs, and large capacity for storing liquid fuel. Multiple Big S wing sections can enable a design to be both efficient at high altitude flight, landing at a safe speed on Duna, and have plenty of LF capacity in its wings. Refuel your spaceplane after reaching kerbin orbit either by docking another spaceplane/fueller rocket with it, or fly it up to your Minmus In Situ Resource Mining station. If you are using IRSU, it doesn't really matter that your space plane is carrying uneccessary mass on an interplanetary journey, since you can mine over 2000lf per day with one small drill and converter. The only time you need rockets is for Tylo (a lightweight, chemical rocket fuelled shuttle required with high TWR) and Moho (astronomical delta v requirement means very pared back ship). In both cases these are likely to be minmalist vessels that would fit in a mk2 cargo bay however. Duna lander

The only manned vehicles I sent to duna - https://kerbalx.com/AeroGav/Astrojet-Lancer It's rather cramped but can actually fly itself from the surface of Kerbin to the surface of Duna and return, with no external support and only the cost of fuel. If you prefer a little more luxury, an earlier design - https://kerbalx.com/AeroGav/Astrojet-Citation This is a 5 seater. It cannot quite return from Duna to Kerbin without some refuelling , though it could take off again and reach Duna orbit. Fortunately it has a docking adapter port. I also built a "hotter" version of this ship, with disposable booster jets and drop tanks, with enough delta v to come home again https://kerbalx.com/AeroGav/Astrojet-Citation-X

Enough wing - open up the aero data GUI during an ascent, alt f12 then physics tab to show the option. Watch your AoA and lift drag ratio. Tune your AoA for best lift:drag ratio. If you find yourself having to pitch up to AoA that give significantly worse lift:drag than optimal to avoid getting too fast too low and overheating (or exceeding the best speed of your airbreathing engines while still deep in atmosphere) you need more wing. re: tiling big S wings It can be done, though it might be better to install B9 Aerospace procedural wings since it gives freedom to pursue the aesthetic you want. It's not your fault the game didn't include stuff that's right size. Struts - try to avoid attaching wings to wings or too deep in the "tree structure", try to keep them higher up the node. eg. attach each wing to it's own fuselage piece and offset it. If you need to attach wings to wings for outer sections, putting heavy masses like engine pods on the join can stop this joint flexing up when lift is created. Again though procedural wings are your friend. I also recommend GPOSpeedFuelpump, since manual transfers become unmanageable in larger craft. Eg. you can transfer fuel from multiple wing tanks to a single rocket engine feeder tank in the fuselage, but if you have multiple pod mounted rocket engines you can't run simultaneous transfers

Looks like a few of you have a working SSTO at this point, but I'll share this as a data point, my attempt at a Juno Spaceplane. I've decided to call it the Icarus, can't think why https://kerbalx.com/AeroGav/Icarus One terrier, 3 ft 400 tanks and , wait for it, 14 Juno engines ! I did start off with 10, but was unable to bust the sound barrier, I added another pair, but then the engines hung unevenly off the wing, it must have an odd number of engines each side so that the engine which is coupled to the wing has the same number of neighbours hanging off it's left as it's right side. So, 14 it was. This gets me to mach 1.5 at nearly 15km airbreathing.

Welcome to the wonderful world of front / top first fuel drain. Real rockets don't become bottom heavy as the fuel burns off, because each stage has one large fuel tank at the top and one large oxidizer tank underneath and they drain together. So you could install a mod like TacFuelBalancer or GPOSpeedFuelPump (both extremely tiny memory footprint since they add no parts or textures). Or you just work around it as a rite of passage like experienced Kerbalizers. Your boosters are 2 tanks tall, when the top is empty and the bottom is full , coupled with engine mass your centre of gravity will be rather low down. As soon as you go off prograde, everything ahead of the yellow circle is generating body lift that is trying to pull the nose further out of line. Everything behind it is generating lift that's trying to kick it back in. The problem with the CG so far down the rocket, is that you have far more working against keeping it straight than helping. IOW it is unstable. You can try mounting the largest possible wing surfaces as low down in the rocket as possible to counter this - the further behind the CG they are, the more lever arm they have to work with. Or rework your fuel system so you don't have large shifts taking place. Swap the smaller tanks in the core stage for FT800 but make the boosters only one tank tall? slide them down the rocket whilst adding fins?

Let's try and break this down in a more scientific way. Whilst most people use an LV-N to replace a Poodle, the Poodle is a 2.5m engine with 250kn thrust. In the sort of interplanetary application for which you'd consider a Poodle anyway, the lower thrust of the LV-N isn't an issue, but let's take a more direct comparison - the terrier. Both are 1.25m motors and both give 60kn, but are useless in thick atmosphere. The Terrier weighs 500kg and burns 20kg fuel per second*( i am including tank mass here too) The LV-N weighs 3000kg and burns 8.59kg fuel per second. The break even point is 3 minutes and 40 seconds, or an FT800 LF/O tank. If you are running your terrier for longer than that, or carrying more fuel than that per engine, you'd be better off switching to an LV-N. Now, a very light ship that's pretty much capsule only, gets 4k dV out of that much fuel so a terrier is a good choice to go anywhere. OTOH if it's a big heavy payload, a 4 minute Terrier burn might not even get you a Munar flyby.

They are good for spaceplanes because they don't need as much thrust/weight ratio as rockets, also it's really nice having one fuel type for both your jet and rocket engine. Especially so when you can put liquid fuel in a lot of the airplane essentials - intakes,NCS nose cone, wings, strakes. You'll need one LV-N for every 15 tons of airplane mass, lots of lift and very low drag, also having a fuel balancer mod like GPO SpeedFuelPump + ModularFuelTanks makes design a lot easier. 30 ton spaceplane with 2 nerv and 1 whiplash, takes 5 kerbals to minmus and back - And here's how the Space Shuttle might have turned out, had the military not insisted on a cargo capacity that made the carrier plane too big/expensive to develop.

Honestly not had much problem since the update. In fact the Medium gear seems rather tough, though you guys taking off above 100 m/s (200 knots?!) are going to need strong landing legs. The usual cause of a landing going bad is one wheel hitting first causing the plane to flip and some part of the structure to dig into the ground. It seems there's more traction now and the fact there's some suspension means it's less likely to ricochet out of control or cause the wing to flex/break.

I finally managed it, a spaceplane that can SSTO to Duna and back. https://kerbalx.com/AeroGav/Astrojet-Lancer It started life as a replacement for the Astrojet Citation, which worryingly vulnerable to aerodynamic heating with its airliner wings. Using a larger amount of smaller wings means we can no longer afford to run fuel ducts, so it's manual transfers into a feeder tank scenario. The game is confused by multiple transfers, necessitating a single core/engine design. note - i have GPOSpeedFuelPump installed but am not using it for this flight. note 2 - you have to stop the transfer before the tank fills completely, or it will drain unevenly from the wing tanks and make inbalance. note 3- it took almost 28 minutes to raise our AP out of the atmosphere. It was also somewhat reluctant to cross the sound barrier, i don't think you could increase the fuel fraction much more than this. Finally in orbit. The calculated dV is wrong because we still have all this fuel in the strake tanks the nuke cant access, it's not being added to the total. After landing on Duna, we take off to orbit again. This time our fuel reserves are small enough to all fit inside the fuselage tanks, which means the dV reading is accurate. It's enough to get us back to Kerbin though, if you're any good with launch windows

I finally finished my stock Duna SSTO, and got to find out if it can land. Along the way, I met the Kraken, and forgot which action key opens the service bays, which one unfurls the ventral radiator, and which one deploys the dorsal solar array, to much amusement. A bit cramped, but Kerbals don't seem to mind.

You can pack in a small ion powered upper stage, like so - In orbit around Moho, the Kerbal takes a seat in the lander section.. Well, it seemed like a good idea at the time..

It is asking for a decryption key :-/ If you can't get that site to make your files accessible to all, try sharing it on https://kerbalx.com/

The ultimate answer is of course a rover, since they use no fuel and can drive indefinitely, but they are difficult to construct and bringing one to your destination isn't easy. On the other hand you could just pack a bit of extra fuel on your regular rocket based lander for biome hopping, the problem being that the required extra fuel is huge. This is why i quite like my interplanetary space planes - the landing gear allow you to taxi huge distances for less than a tenth of what a single vertical takeoff would cost. Of course, if you actually have an atmosphere and can fly there, so much the better. ..you can see how little friction there is on Minmus - resulting in very good MPG across the surface.

In my experience, landing gear are actually pretty stable in 1.1. Here we have gear attached to a wing - oh noes ! ..and this is us coming in to Minmus. Used to be more skittish, liable to skid and flip over, than it is now in 1.1. Braking action still very poor though, but what do you expect on a planet made of ice cream.

OMG what kind of aerial Winnebago is that supposed to be Eagle? Think of all the mass you're wasting on that engine, surely a Separatron or two would do the job?

Honestly I don't think the wheels are that much of an issue. The Icarus has a radial decoupler on the bottom of each wing, to which is attached a mk0 intake/lf fuel tank/juno. The fixed gear are attached to the bottom of this engine nacelle, and three more juno pods are attached to the central one left and right of it, for a total of 7 engines per wing. Let's just repeat this - the gear are attached to a mk0 fuselage, which are attached to a decoupler, which is attached to the wing, which is in turn attached to the fuselage. With 14 junos, 1 terrier and 3 ft400 tanks of rocket fuel i was convinced it would blow up without ever leaving the ground - but in fact it takes off fine, just set pitch trim to obscure the "I" on the "Pitch" axis display , start your engines, and it will fly itself off. Misaligned gear, not using angle snap and absolute rotation mode is what is causing much of these problem.s

I thought this might be the case, so quickly put together a test vehicle with the same double delta wing and leading edge elevons with authority set to -100% (ie reversed) acting as elevators. Mechjeb was able to fly this normally. So, it's just a Kraken, nothing to see here, please move along. The good news is that the design is viable. The bad news is I have to build it over from scratch to not have whatever bug snuck into the craft file and mess with MJ. The prospect does not exactly thrill me and i've been putting it off all day.

An SSTO rocket is trivial from tech 1? Well , rockets aren't really my area of expertise, but there is no way i could build an SSTO rocket with just flea boosters. I did make a flea powered vehicle that could "escape the atmosphere" but it needed so many fleas, decouplers and fins to get working/keep stable it made the Icarus look cheap. Then again, I've never tried an SSTO rocket. The weakness of the Icarus is the 14 Juno engines that are discarded, along with their fuel tanks and intakes, every flight. Perhaps if you replace them with underwing solid rocket booster pods, you could make the cost per flight competitive with disposable rockets. The Junos take the Icarus up to mach 1.5 and 15km before igniting the Terrier, then get discarded at about 17km mach 1.9 when they flame out. At this point it becomes a type of space shuttle, using solid rocket boosters and a liquid fuelled upper stage. Where it differs (and improves upon) the NASA STS is that the wings are not merely payload on ascent, they actually produce lift and allow a lower TWR, also the fuel tank is not discarded. Remember that not every spaceplane is an SSTO , and not every SSTO is a spaceplane. I'm quite willing to throw stuff away if it makes the spaceplane easier to fly or improves its useful payload/range. As you can see from the video the Icarus does not require godlike piloting skills and got to orbit despite some errors. That launch video was the first flight of the final design and also the first flight to go supersonic (all the others were aborted due to inability to cross sound barrier - had to keep adding more junos - or due to discovering staging errors etc. soon after liftoff).

i can hand fly this airplane however. Why is MJ applying full left rudder from the moment i enable it (before engine start) resulting in plane going off course and crabbing through air? It is also making roll inputs I never asked for . As far as pitch is concerned, as soon as there is a discrepancy between requested pitch and AoA, in the first video MJ applies full inputs to achieve the desired angle. In the second it more or less ignores me selecting +30 nose up in response to the terminal dive. https://kerbalx.com/AeroGav/astrojet-sapphire craft file of the airplane in the second video. craft file of the airplane in the first - https://kerbalx.com/AeroGav/Astrojet-Citation moving the centre of lift further aft and adding a conventional control surface like the first airplane has does not help at all

Ladies and Gentlemen, I present the Icarus.. https://kerbalx.com/AeroGav/Icarus Something this basic raises the question, "what is a spaceplane?" I'd say a spaceplane is something that can make orbit uses airbreathing engines at some point uses lift rather than thrust to overcome gravity at least half of it comes back Not really economic though. The Panther/Terrier "Hermes" on my KerbalX page is less wasteful, has better margins, and can bring a few tourists

Alright, I'm only a recent convert to the ways of Mechjeb, but was able to use it on my space plane like an autopilot, able to precisely command AoA , sideslip and roll angle in single degree increments. You can see from this launch video how well it works. On my newest design however, Mechjeb simply makes insane control inputs. Sometimes it applies full aileron and rolls us over and over till we crash. In this example it puts in a bootfull of rudder and has us constantly sideslipping, but appears to command pitch very loosely. Tried removing then reattaching the mechjeb module, orientating it differently. What's going on?