Northstar1989

That's actually a common misconception, and not true. Lumping fins and thrust vectoring in with SAS stabilization (assuming you meant that a properly balanced rocket will just fly straight up without any guidance), if you have none of these, and your rocket is perfectly symmetrical, your rocket will *ALWAYS* end up tipping over... Why, you might ask? Because of Kerbin's rotation. As a rocket ascends *straight up*, its effective period of rotation about Kerbin's center increases- giving it velocity relative to the surface. As drag appears to be calculated relative to surface speed rather than orbital speed (at least at low altitudes- a rocket with no horizontal speed just after liftoff experiences no horizontal drag, despite moving at an orbital horizontal speed equal to Kerbin's rotational velocity), this means that the rocket will start to experience drag pushing it in the direction of Kerbin's rotation, despite continuing to fly straight up. Assuming the rocket's Center of Mass isn't *exactly* halfway up the rocket, and that the drag coefficients of the parts above the Center of Mass aren't exactly equal to the drag coefficients of the parts below the center of mass (weighted for part mass, as stock aerodynamics uses something along the lines of Drag = Mass * Drag Coefficient * Velocity^2), this will generate torque in the rocket- either towards the direction of Kerbin's rotation, or against it. So a rocket with *absolutely NO* stabilization will ALWAYS tip over, even flying straight up... Whether this occurs quickly enough to prevent the rocket escaping the atmosphere is another thing- based partly on the rocket's TWR... Normally, this effect is trivial- and can easily be compensated for by thrust vectoring or the smallest probe core. But, in a rocket lacking any SAS, control surfaces or aerodynamic stabilization, or thrust vectoring whatsoever; a certain amount of torque on the rocket is almost inevitable, and could potentially lead to a crash... Regards, Northstar

Serene made an ion engine-only craft BEFORE the 0.23.5 update (see the Scoreboard). I highly recommend you check out her design to see how she did it... Regards, Northstar

FAR makes it possible to reach much higher speeds with hypersonic aircraft and rockets, but it's actually a profound disadvantage to subsonic aircraft like the propeller planes which have dominated this challenge so far- as it *increases* drag up until reaching Mach 1. Geschosskopf (the OP) made the right call in making it a bonus for this challenge- though for some other challenges (such as my own Heavy Lifter rocketry challenge) penalizing for FAR point-wise makes more sense... Regards, Northstar

I was also reading an article just last night (technically this morning- after midnight) that said that jamming of military-grade drones is definitely not something we would be able to rule out, especially in the future. (I think the article was on RocketManifesto, though don't quote me on that...) Given that autonomous drones would have to either be sentient (which creates its own problems), or imbued with programming that wouldn't necessarily enable them to carry out many of the advanced tactics and maneuvers that would be utilized by manned/AI ships; and as I read, RC drones could be jammed; I'm even more convinced than before that manned warships would have at least SOME role in space- although I can imagine a number of niches (such as low-action garrison duty) where unmanned craft would still be vastly superior... Regards, Northstar

I feel the need to chime in again on the lasers vs. railguns vs. missiles issue: I saw a post before about how kinetic weapons would probably be banned in populated/crowded space- because projectiles that missed their target (due to evasive maneuvers at long range, for instance) would be left shooting all over the system, and could easily set off some kind of Kesseler Syndrome... What do you guys think of that point? I think it's a very good argument in favor of beam-based weaponry (such as lasers- but also eventually including things such as controlled plasma streams), as such weapons wouldn't leave the dangerous mess of spent round zipping around the system at all sorts of highly elliptical orbits... Even if beam weapons were less effective than the alternatives (I can definitely see an argument for kinetic weaponry being superior at close quarters, and missiles at long range- but I think beams/lasers would dominate somewhere in the middle...), it would be very good argument AGAINST use of kinetic weaponry- and to a lesser degree missiles. It should also be pointed out that any round you fire off in orbit that misses its target will eventually come back to your firing location, given enough time, if it doesn't reach escape velocity. Given a large/complex fleet-style battle, I could easily imagine some rounds phasing back to hit the ship that fired them in a few hours or so if it didn't move from its position... If kinetics and missiles were allowed, I would imagine a hierarchy something like the following might develop, with different weapons systems being best at different ranges: Close Range: Kinetic weapons and unguided rockets (unguided rockets don't transfer nearly as much waste heat to the ship firing them as railguns, etc., for their final velocity) Medium Range: Lasers and beam weapons (beams can be swept across angles, creating interlocking boxes/triangles of fire that *cannot* easily be dodged. Lasers also move at the speed of light!) Long Range: Guided missiles and disposable parasite drones (the ability to maneuver around moons, planetary horizons, etc., and make course-corrections would be invaluable) It need not be said that at long range, lasers/beams would be superior to kinetics and unguided rockets, although inferior to missiles. I would imagine a strong preference for lasers/beams both in order to give warships range versatility, and to avoid filling planetary orbital space with dangerous dodged spent missiles and kinetics... Regards, Northstar

While I was waiting for the next ship of my Duna Aramda to reach the Duna system (the Duna MagSat), I decided to browse the Tracking Station's asteroid function a little, and see what interesting objects I could come across... And then, by sheer chance, I found THIS: I have discovered a Class C asteroid on a DIRECT IMPACT TRAJECTORY with Kerbin- estimated to impact the planet in 2 months. I know this may not *seem* like a big deal, as Class C asteroids are "only" 7-10 meters- but if you do the math on its relative size to Kerbin's radius (600 km), vs. Earth's radius (6371 km), this equates to a 74-106 meter asteroid hitting Earth... Which would impact with a force of roughly 38 Megatons of TNT if it came in at a 45 degree re-entry angle... (according to estimates for a 100 meter asteroid on Wikipedia) THAT is a big deal... For comparison, the asteroid that caused the famous Tunguska event in 1908 was 60-190 meters, only entered Earth's atmosphere at a shallow angle with a LONG period of drag to slow it down (it most likely had what would initially be plotted as a periapsis in the lower atmosphere, rather than a direct collision course), and it detonated with a force of "only" 10-15 Megatons of TNT (low for an asteroid of that size) 5-10 kilometers above the ground. It flattened an area with a radius of between 55 and 70 kilometers, and generated a shockwave that would have registered as a 5.0 on the Richter Scale... Now imagine an asteroid impact more than twice as powerful (due to much steeper angle of re-entry). http://en.wikipedia.org/wiki/Tunguska_event http://en.wikipedia.org/wiki/Impact_event#Frequency_and_risk Clearly, an asteroid equating to a similar size range, of unknown composition (in real life, metallic asteroids are much more dangerous for their size, due to their higher mass and superior ability to penetrate the atmosphere), and on a DIRECT re-entry trajectory equating to what should be a steep re-entry angle of between 60 and 90 degrees into Kerbin's atmosphere CANNOT be allowed to impact. It would likely result in a TRAGIC loss of life should it impact a populated area... (it would cause greater devastation than Tunguska, but potentially in a populous area...) Therefore, I have commissioned a secret program known as "Project Amadeus", to avert potential tragedy, and distract myself from Duna for a bit. More on this later... Regards, Northstar

Nobody is posting their actual pictures to this thread. These are all links to Imgur, which displays the pictures here- but actually has them stored on the Imgur databases...

(1) Did you make use of the Cargo Throttle function on the Firespitter propellers and helicopter rotors? If you didn't, you should load back up the craft (assuming it's still on Duna) and make use of the Cargo Throttle to push up the altitude ceiling (it would have been best if you assigned Cargo Throttle, Normal Throttle, and Hover Throttle for the propellers each to an action group- but you can also change them all to Cargo Throttle while landed if you think you can still safely take off with the extra thrust...) You might have to keep the throttle down to avoid over-draining your batteries at the lower altitudes with Cargo Throttle, though it shouldn't be an issue near altitude ceiling (as the air becomes thinner, the propellers use less electricity...) (2) Have you considered redesigning the craft with the Multipanels mod? That's a LOT of solar panels on the wings- and you could definitely bring down the part-count that way, without altering the ration of Ec/s to tonnage *at all*... Alternatively, you could think about using a NearFuture nuclear reactor- which would allow you to fly just as well at night, for similar tonnage... (3) You stole the name of *MY* Duna Biplane from before! Didn't you see the post earlier on this thread where I presented "The Hummingbird"- a test model that I still haven't yet sent to Duna? (http://forum.kerbalspaceprogram.com/threads/50619-Flying-Duna-AGAIN?p=803139&viewfull=1#post803139) Though, I guess you can take the name- my "Hummingbird" will probably never make it to Duna anyways (it's a bit fragile to strap to the side of a rocket, due to the way the biplane wings were built...) Regards, Northstar

The Eagle Mk2, it turns out, can indeed manage to hurtle out of the atmosphere from the momentum of its Thermal Turbojet (which only works in-atmosphere) even after having descended to a normal flight regimen- in fact I took it all the way to a 148 x 25 km unstable orbit from an unpowered glide at 4 km... (after re-activating the Thermal Turbojet, of course) It's too bad I couldn't simply land the thing as was, and get the Kerbals out that way... However, while pondering over what to do with the Eagle and its crew before making this maneuver, a new thought struck me- why not just intercept the Eagle in an unstable orbit (like the one I subsequently achieved), and transfer some LFO mix over to the service module in the front of the plane to attempt to balance the extra uranium that magically appeared in the reactor at the rear? It's ONLY 30 days until the Duna Heavy Equipment Deployment Platform (DHEDP) arrives at the Duna system... I'll just leave the Eagle on rails until then, to prevent drag from slowing it down (I certainly wasn't going to keep it gliding/flying on Duna for 30 days straight- my computer would fry after a month of continuous running like that, or I would have to do it in maybe 100 or more quicksave/quickloaded sessions now that atmospheric F5/F9 is possible...) This is in fact necessary, as without the atmosphere to convect heat away from its radiator most of the time, its reactor would just end up overheating and entering emergency shutdown (which requires a full cooldown cycle before it can then be reactivated- which takes several game days or weeks if I remember correctly...) if I kept it loaded in unstable orbit like this, though I could at least make use of time-warp (while outside the atmosphere) to speed things up then, and occasional boosts from the Thermal Turbojet near periapsis to keep drag from pulling it back down towards the ground... I know it's not realistic to exploit the rails system like that- but as I've said before, neither is 100's of extra kilos of uranium magically appearing in the reactor of a lightweight plane in the middle of an interplanetary transfer... Hey, it certainly beats bailing the 2 Kerbals in the (relatively fragile) service modules out in orbit; to wait for a month without food, oxygen, or even protection from radiation; and crash-landing the remaining two (safely in their relatively resilient/reinforced cockpits) on the surface of Duna... In the meantime, the Duna Heavy Equipment Deployment Platform (DHEDP) inches towards the Duna system with its large cargo of supplies and tools to build a self-sufficient Duna colony (and originally also an Ike outpost for electrolyzing regolith- though I guess I'll just appropriate those supplies for other purposes now that, thanks to a KSP-I update since the DHEDP's launch, I can get all the Oxidizer I could ever want from electrolyzing water-ice on Duna...) When it arrives, I might as well appropriate some of the supplies to build a small unmanned LFO tanker- and use it to fuel up the Eagle's front service module to try to counterbalance the extra uranium in the reactor... The low elliptical orbit of the Eagle and powerful engine the tanker will require for an elliptical intercept (which would also be good for a suicide-burn) should also make an excellent starting point for a targeted landing of the probe at the site of my future Duna base- I will need plenty of fuel, and RocketParts (from recycling the tanker), for my colony after all... All I need do is throw some landing legs on the tanker and I'll be set. Regards, Northstar

Ahhh, frack it (BSG anyone?), I went ahead and gave re-orbiting the Eagle Mk2 a try. And, though it couldn't even get above 36k on Kerbin under its own power, Duna's low gravity and lower scale height were an absolute godsend for shoving the Eagle outside the clutches of the atmosphere: Now, I just need to decide what to do with it... Do I Hyper-Edit out the extra reactor fuel that magically appeared in the rear? (surely an exception can be made for cases of things appearing in a vessel due to updates to a mod's units system, that weren't there on launch?) Do I intercept it with a small fuel carrier probe with a KAS winch when the Duna Heavy Equipment Deployment Platform reaches the Duna system in approximately 30 game days- as can be seen in the Kerbal Alarm Clock potion on the screenshot below? (The DHEDP is a mobile orbital-construction platform, designed to carry all the supplies and construction equipment needed to establish a tiny self-sufficient Duna colony) Do I engage in both activities if both are allowed? Or perhaps do I just bail the Kerbals out at apoapsis, circularize their orbits by EVA jetpack (the higher the apoapsis, the lower the orbital velocity- and a Kerbal jetpack carries roughly 600 m/s of fuel...) and leave the Eagle Mk2 to its (wasteful) fate crashing back into the surface after drag eventually destabilizes it, if neither action is allowed... Regards, Northstar

I'm sorry to disappoint, but it looks like the Eagle Mk2 will *NOT* be able to complete the challenge successfully in its current state... (there *might* be one way for me to save the mission- scroll down to the bottom to give your opinion on that) Although it had no trouble getting to Duna, and reaching a semi-stable orbit (perfect for either a gradual re-entry or stabilization) despite an unplanned encounter with Ike: And can deploy/re-enter and reach stable flight in the atmosphere just fine, at a variety of altitudes (showing a superior non-ballistic altitude ceiling to any successful posted craft I've seen so far in this challenge- about 24k meters- sorry I've got no screenshots of the altitude ceiling, I was waiting on that until after a successful landing), although it took a couple tries to get a safe re-entry due to my own foolishness... (not to self: diving at orbital speeds to speed up re-entry is *NOT* a good idea) Ultimately, the Eagle Mk2 faced serious stability problems in the lower atmosphere (below about 8000 meters) due to the spontaneous, magical, and UNPLANNED re-appearance of a full reactor load of uranium in its KIWI Nuclear Reactor during the interplanetary transfer following an update to KSP-Interstellar. As a result, the nose could not be pulled more than about 7 degrees (6.8 was the most I could get without loss of control) off the horizon below about 5000 meters- making landing effectively impossible in Duna's hilly terrain (at least for a pilot as bad at landing as I am). All (30+) attempts ended rather like this: For those of you who don't understand (or didn't read my earlier posts on the Eagle Mk2), test flights of the Eagle on Kerbin revealed it faces *SERIOUS* stability problems (being far too tail-heavy) when equipped with a full load of reactor fuel and no cargo in any of its other fuselage modules. As such it was designed and launched (using either TAC fuel Balanced before liftoff, or tweakables- I can't remember if it was built before KSP-I reactor loadout became a tweakable...) with a PARTIAL load of uranium- only 10-15% of maximum. This served to reduce weight, raise altitude ceiling, and improve TWR of course- but its most important effect was to shift weight AWAY from the tail section of the ultra-lightweight fuselage design. Perhaps, if I hadn't quicksaved after finding a successful re-entry pattern and deploying the Eagle Mk2 on it the second time around (it took me about 3 tries to re-enter, the first two times crashing due to impatience and stupid mistakes trying to speed the process up), I could have saved the mission by adding some LFO as cargo to the front service module (or Monopropellant, if I had saved some from the transfer vehicle rather than wasting it all during Duna capture) to balance the magical new uranium load in the rear. Even so, I'm not sure that would have weighed enough. But now, I have no option to save the mission unless I want to try and intercept it to add front-loaded cargo during the extra-atmospheric portion of an unstable orbit, as it is designed with a high enough altitude ceiling (at least 24,000 meters, from my experiences on Duna) that its relatively weak Thermal Turbojet is capable of kicking it well out of the atmosphere on a ballistic trajectory... Actually, that might be worth a try- although the only vessel with the KAS winch to refuel it currently in the Duna system (the Duna Science Module) is touched down at the site of my future Duna base, and doesn't have the fuel aboard to make it back to orbit... Which means, cheaty as it sounds (and is), I would have to leave the Eagle on rails in an unstable orbit for at least 9 or 10 game days (until the arrival of the next vessel of the Duna Armada- despite all leaving in the same transfer window, the different ships all utilized very different ejection angles and transfer velocities...) I can't keep it loaded all this time, because the nuclear reactor would overheat and go into emergency shutdown (requiring about a month of in-game cool-down time before reactivation) without the atmosphere to convect heat away from its radiator over the majority of its unstable orbit, preventing me from counteracting drag without a means of thrust... (I could also leave it gliding for 9-10 days before leaving the atmosphere, with occasional bursts of engine power to counteract drag- it has enough endurance for roughly a year of that with the unplanned extra reactor fuel- but who wants to run a mission for 4-5 real life days at 2x physics-warp, having to quickload the mission from an atmospheric quicksave every time they play KSP?) So what do you guys think? Should I give ballistic interception (to load cargo in the front sections to counteract the extra reactor weight) a try? Or would something else, like Hyper-Editing (although I've never used HyperEdit, as a matter of principle) out the excess reactor fuel that was never supposed to be there (and is throwing way off the CoM) be acceptable? Regards, Northstar EDIT: OK, reading back over previous posts- maybe it's possible to land even with only 7 degrees of Angle of Attack flexibility... The Eagle Mk2 can get down to gliding at about 58 m/s at 3200 meters before I lose control or smash into a hill... I see that some landings were done at as much as 120 m/s- so maybe I just need to find a better landing spot... One with a LOT of flat space- since I can't imagine lining up a precision landing without being able to pull up/down the nose a lot further and quicker than I currently can!

Your debris is not slowing down (much) while it is at periapsis because it is actively falling lower while in the atmosphere, making up for any losses due to drag. However, it should be moving slower at each periapsis, as it is falling from a lower apoapsis each time... 85 km also isn't a terribly low periapsis, even on Eve. It's going to take a while at that rate to see measurable declines in velocity at periapsis at each pass...

At first, my attempts at landing the Eagle went pretty smoothly: However, attempts to actually touch down all ended like this: The Eagle had suffered greatly from updates to KSP-Interstellar nuclear reactors that had occurred since its design. The main issue was that a change of the scale of units for the nuclear fuel (so that consumption could more easily be observed) had led to the nuclear reactor's fuel load resetting to a *FULL* uranium load while en-route to Duna. This was a MAJOR issue because The Eagle was designed to work with a PARTIAL uranium load. This wasn't just for keeping the TWR up and weight down- extensive testing on Kerbin had revealed that with a full reactor load, the plane was far too tail-heavy, and had major control issues in upper atmospheric pressures comparable to Duna's lower atmosphere at speeds slow enough for landing... (at even higher altitudes, the atmosphere would become thin enough for SAS to compensate, at even lower altitudes the atmosphere was thick enough for the control surfaces to compensate even at landing speeds) Short of Hyper-Editing the reactor load back to a 10-15% reactor load, which would break all my reservations about HyperEdit and probably disqualify the craft for the Flying Duna Again challenge, I don't see any conceivable way to fix this issue. However, experiences during the re-entry attempts revealed that it was possible to kick the craft into a highly elliptical (but decaying) orbit with the Thermal Turbojets as long as the velocity did not fall too low... (I am unsure of the Eagle's ability to achieve an extra-atmospheric apoapsis once it has reached normal flight velocities- though it is probably possible on Duna, unlike on Kerbin, due to the weak local gravity well and shallow atmospheric scale-height...) So, I will probably at least "save" the Kerbals by setting a high extra-atmospheric apoapsis, and having the Kerbals bail out on EVA (the higher the altitude, the lower the orbital velocity- meaning it is easily possible to circularize or at least stabilize an orbit via jetpack on EVA with a sufficiently high apoapsis...) This isn't at all "realistic" to have the Kerbals wait in orbit with no spacecraft to protect or feed them, etc.- but neither is having hundreds of extra kilograms of uranium magically appear in the back of a lightweight plane during an interplanetary transfer... The (abandoned) Eagle itself will probably be left to crash back into the ground on Duna- or perhaps I will have one brave Kerbal stay behind as a pilot to make a controlled crash-landing near the future location of my Duna base, to later be rescued by the Hornet Helicraft and ferried to the base facility (while safe touchdown proved impossible, in most of my 30+ crash-landings at least 2 or 3 of the 4 Kerbals passengers survived the crash. In one case of an almost-successful landing, the only part to break off at all was the Atmospheric Intake...) It would probably be possible to save the mission with a sufficiently skilled pilot- but over 30 attempts have revealed that pilot just probably isn't me... (I'm actually pretty good with flying planes in KSP, but I'm terrible at landings...) I'm sorry to have to break my promise to you guys. I *REALLY TRIED* to make a successful landing with the Eagle, knowing that after just one touchdown I could use TAC Fuel Balancer to dump (technically, to "Edit" out- the "Dump" function doesn't work with reactor fuels or SRB propellant) the excess reactor fuel that magically appeared in the Eagle during its interplanetary transfer. But alas, I couldn't get it safely onto the ground without any parts breaking off, due to my inability to (safely) pull the nose more than a few degrees away from the horizon... Regards, Northstar

OK, long story short, the first attempt didn't go so well... It was working BEAUTIFULLY until somewhere during my descent I decided it was taking too long to glide down to the surface (I was running our of sunlight, and didn't want to attempt a night landing)- and that it was a good idea to attempt a dive at near-orbital speeds... The Eagle didn't have nearly enough torque between its controls surfaces and SAS to manage that, and, well, if you want to see how it ended just look at the last screenshot. The third-last screenshot was the last one of The Eagle in stable flight: Thank God for the wonder of F5/F9! Next time around, I'll be keeping the rocket attached through the first pass without any of the fancy space shuttle-style high-altitude turns. That way, it can benefit a little from an additional aerobrake too- I want to set this future piece of space junk (the transfer vehicle) in a nice, low orbit so it has room to phase with the rest of my armada and the site of my future space station (which will probably be my first step in colonizing Duna- consolidating all my orbital assets into a single gargantuan space dock in the Extraplanetary Launchpads style- which requires large construction crews to be effective...) Regards, Northstar

OK, so maybe I spoke too soon... I promise though, eventually you guys WILL hear (or rather, read) "The Eagle has landed!" First, there was the deployment phase for the Eagle Mk2: This worked out quite beautifully. The Eagle was set up for a lower periapse by its transfer stage, released via the decoupler without a hitch, and then the pilot had no trouble getting out and re-activating the nuclear reactor which would power the Thermal Turbojet (remembering the bugginess of the collision boxes on the Raven Mk2 before, I decided to have the pilot perform this action- since there were more winglets around the navigator/co-pilot's seat that might have posed issues for him getting back inside the Eagle afterwards...) You might even have noticed my checking the function of the landing gears, checking the function of the solar panels, checking the function of the heat radiator, and even renaming the vessel as the "Eagle Mk2 Duna Plane" in the final two screenshots... Everything worked out beautifully. Next, I began my first atmospheric pass. Taking a page from the real-life space shuttle program (and Scott Manley's video on his own space shuttle-style spaceplane), I decided to turn the Eagle's wings perpindicular to the direction of movement (keeping the long axis parallel to the horizon to prevent potentially dangerous head-over-heels tumbling which might turn out unrecoverable in Duna's lower atmosphere) to provide extra drag, and theoretically spread out re-entry heat more evenly. This *DID* work (even the stock aerodynamics module allows it) from the extra drag perspective, but it still wasn't enough to bring the Eagle's apoapsis down inside the atmosphere... Things you might notice include my checking the inkerbolation (in real life, we use the term in-sol-ation for exposure to sunlight, as Earth's sun is called Sol) of the solar panels, the (steadily rising) temperature of the heat radiator, and just taking a look at how close yet how far away I am from the probable site of my future Duna base (although, due to one of the more, IMHO, inane requirements of the "Flying Duna Again" challenge, the initial landing has to be at over 2500 meters altitude- in my opinion it would have just made more sense to allow sea-level landings from orbit, followed by a requirement for subsequent landings at over 2500 meters. Anyways, I won't be landing there initially...) In fact, at the current rate, I estimate it will take at least THREE atmospheric passes before the Eagle can finally attempt a landing. This is going to take a while... Regards, Northstar

The Eagle Mk2 and its transfer rocket have arrived safely at Duna, and are now in a low (decaying) orbit, preparing for deployment of the Eagle Mk2 onto a re-entry trajectory into Duna's atmosphere! But before we get to that, a quick update. The second LiquidFuel Tanker that I launched towards Duna made its mid-transfer course-correction, and is now on an encounter trajectory with Duna, much like its sister tanker. Here's a screenshot of its finishing its burn: Don't I just love teasing you guys. Now, anyways, here are the screenshots I'm sure you guys REALLY want to see- those of the Eagle Mk2 making its capture into Duna orbit (complicated slightly by an encounter with Ike- which forced me to lower the periapsis back into the atmosphere) Had enough? Haha, OK, here are the pictures for REAL though. First, the approach and Ike encounter. Notice my use of RCS to make small adjustments to the periapsis (I could have used the NERVA engines, but I figured I'd use surplus Monopropellant first to maximize my total Delta-V, as the RCS has lower ISP...) And the aerocapture (actually not too many G's pulled here, surprisingly) I included several shots here showing my total loss of control of the vessel shortly after periapsis, due to running out of electricity for the SAS wheels (the sun went behind the horizon, cutting off electricity to the solar panels). Fortunately, the rocket + plane combo had enough momentum to still exit out of the atmosphere despite the wings often facing at a perpendicular to the direction of movement (and may have actually served a useful purpose in increasing drag)- but I was worried the whole time that the plane might tear free from the rocket due to the forces on the wings (thus placing it in a potentially fatally steep re-entry orbit), or snap in half like its sister did during ascent from Kerbin... Neither happened, though, and you can see me regaining control with the RCS after exiting the atmosphere in some of the later screenshots. The fun wasn't over yet, though. The periapsis still had to be raised, and rather than waiting entirely until apoapsis, I decided to use the rest of my surplus Monopropellant to raise it as much as possible shortly after exiting the atmosphere, by thrusting radially inwards towards Duna. This also had the desirable effect of lowering the apoapsis and thus reducing the time until apoapsis- which was great, as the phasing was already looking good for a direct re-entry on the next pass (the periapsis was on the light side, closer to the dawn horizon than dusk), and I didn't want to miss the opportunity while the Eagle Mk2 languished at apoapsis... Also, as you can see, at first I left all RCS ports active- but soon I discovered that the placement wasn't ideal anymore, with shifting of the rocket's Center of Mass towards the engines due to fuel consumption. The lower RCS ports now were located close to the Center of Mass, whereas the forward RCS ports exerted strong torque effects. Therefore, rather than having the forwards ports thrust in both directions at once in order to maintain heading and stability, I soon took to switching the RCS ports on and off depending on whether I wanted thrust without rotation, or torque... Finally, I decided to save the rest of the orbital adjustment for apoapsis as I started to run out of RCS fuel, and saved the last of the Monopropellant for a turn of the craft to face its solar panels into the sunlight (all of which are located on the plane module- the rocket originally was shaded by planes' wings on both sides, leaving few goods spots for panel placement- and it has enough electrical storage to stabilize orbit before it goes dead after the final plane module detaches...) I was then able to utilize the SAS to orient for a prograde burn at apoapsis (also using the last fumes of the RCS before activating the NERVA engines), and then a retrograde burn at periapsis to bring the orbit down on the opposite side to a point where the vessel will undergo eventual re-entry if I do nothing. The point in the last screenshot is where I made my quicksave. This will allow me to experiment with a variety of re-entry profiles for the plane module, although my first attempt will involve bringing the periapsis down a bit further... I hope you guys enjoyed this! My likely next words will be "The Eagle has landed!" Regards, Northstar

OK, one more distraction. I decided to a little landnav with my Mun Rover... Eventually I'll have to find the time to get it over to one of the major craters, but my experience showed it's going to take several hours of real-life time to get it anywhere... (it took almost an hour just to move past the rim of one small crater) Regards, Northstar

More impactors! More science! This will have to tide you guys over for now. Soon, the Eagle Mk2 will be arriving at Duna, however. Regards, Northstar

In different words, isn't that what I just said? I never said that the TWR necessary to keep terminal velocity goes up (although the time it takes to catch up to terminal velocity from stationary does- meaning that a higher launchpad TWR is desirable), only that the balance between atmospheric and gravity drag changes- making atmospheric drag relatively less of an issue, and making the fuel savings from reaching orbital velocity faster more important... Regards, Northstar

Also, for those of you curious, since the potential energy you can gain or lose from a gravity assist is determined by the orbital velocity of the moon around the planet it is orbiting itself (or planet relative to the sun it is orbiting), you can actually gain slightly more energy from a gravity assist around a body with an elliptical orbit when it is at periapsis than when it is at apoapsis... This makes little difference for the moons and planets in the stock game, which all have relatively circular orbits, but can make a HUGE difference if you are playing with Krag's Planet Factory- which adds a "planet" called Ascension which is in a comet-like trajectory around Kerbol... You can gain a LOT more energy relative to Kerbol if performing a gravity assist around Ascension at its periapsis with the sun than at its apoapsis- which helps if you are trying to reach Kerbol escape velocity... Regards, Northstar

A passive gravity assist *IS* affected by your periapsis relative to the gravitational body, first of all. The closer your approach the body, the greater the average effect of the body's gravity on your craft during the time you are in its SOI... Think of it this way- the closer your periapsis, the greater the possible effect on your trajectory heading relative to the gravitational body. And certain exit trajectories represent a greater increase in final energy relative to the body the moon (or planet, for a gravity assist relative to Kerbol) is orbiting, whereas others represent lesser increases in energy or even a decrease in energy. In the most extreme case, exiting a moon's SOI moving precisely retrograde relative to its velocity would decrease your kinetic energy by the most relative to the body the moon was orbiting (assuming you came in at a different angle) whereas exiting moving precisely prograde would increase your kinetic energy by the most relative to the planet... Exiting moving precisely prograde gives you the most KINETIC energy, but doesn't give you the most TOTAL energy. This is because TOTAL Energy = Kinetic + Gravitational Energy. This is most obvious for a moon with a large SOI and strong gravitational well relative to the body it is orbiting- such as Ike relative to Duna. You *could* exit Ike's SOI moving precisely prograde, at the same altitude as Ike's orbit around Duna, for instance. Or you *could* exit Ike's SOI moving at a 30 degree altitude to prograde, radially outward, at a HIGHER altitude relative to Duna. In the 2nd case, you exit with the EXACT same velocity relative to Ike as in the 1st case, and thus the same Kinetic energy, but with greater Gravitational potential energy relative to Duna- as you exit at a higher altitude. I *HIGHLY* recommend seeing the tutorials on the KSP Wiki about gravity assists (http://wiki.kerbalspaceprogram.com/wiki/Gravity_assist). A gravity assist that will provide you with the MOST increase in energy relative to the body you are orbiting (because unpowered gravity assists *CAN* increase your total energy- by increasing your gravitaitonal potential energy relative to the planet without hurting your kinetic energy relative to the moon) is one where an imaginary line drawn perpendicular to your periapsis with the moon passes precisely along the prograde vector of the moon's orbit relative to the planet, and your periapsis is as close to the "retrograde" side of the moon as possible without impacting its surface... Please note that gravity assist CANNOT provide you with kinetic energy relative to the MOON they are around in KPS's current physics model, but they CAN provide you with kinetic energy relative to the PLANET the moon is orbiting around. This is because any degree you are moving SLOWER than the moon relative to the planet in the direction of the moon's orbital trajectory actually counts as moving FASTER relative to the moon within the frame of reference of the moon. Therefore, you can exit the moon's SOI with both more Kinetic AND Gravitational Energy relative to the planet than you entered the moon's SOI with... Regards, Northstar P.S. Where does this extra energy from an unpowered gravity assist come from, you might ask? In real life, it comes from the moon itself- which either gains or loses an equal amount of energy to that lost or gained by the craft passing nearby to it. A moon is usually much more massive than a spacecraft, however, so the change in the velocity of the much more massive moon is very small compared to the change in velocity of the much less massive spacecraft...

Posting a picture of the rocket might help. If the rocket is built in perfect left/right symmetry (or 3-way or 4-way or whatever symmetry) using the VAB tools, then the Center of Mass should lie directly over the Center of Thrust. So your problem is more likely that your rocket has too large or too small of a gap between the Center of Mass and Center of Thrust. You might also try adding more SAS force and control surfaces, and making sure your existing SAS wheels and winglets are as far from the center of Mass as possible to maximize their potential torque... Regards, Northstar

Also, all of this assumes you're not playing with a revised aerodynamics module like FAR If you're playing with FAR, and have a long, thin rocket with fairings; then your terminal velocity goes WAY up, and as a result the ideal TWR rises as well, since atmospheric drag is less of an issue, but gravity drag is still just as big a deal... Regards, Northstar

Maybe 100, 120 Delta-V at the most vs. a rocket with a TWR of 2 all the way up (achieved by lifting off with a TWR of 2 and then staging and throttling to keep it from rising higher)... No idea how that compares to a TWR of 1.7. But remember, with a really large rocket, that sill represents a LOT of fuel and lost potential payload mass... So not more than 3% Delta-V savings at a maximum. I mostly use this knowledge as a guide for where to stage my disposable rockets- i.e. shortly before my gravity turn so that my TWR declines at this point... Regards, Northstar

A lot of math in earlier posts here, but I think the ultimate question was what was the most efficient TWR, no? It's an interesting question, but players debating this point always miss one key point- lift. Many rockets are equipped with tail fins, which are capable of providing a small amount of lift, and a great deal of drag once the rocket begins its gravity turn (until the prograde vector points at less than 45 degrees to the horizon, the majority of force on the tail fins will be retrograde-horizontal rather than upwards). Additionally, the same tail fins increase drag if the player points even slightly off the vertical during their initial ascent (that is- they increase the effect of steering losses). Both factors act to increase the relative effects of atmospheric drag, therefore, the ideal TWR during ascent is actually less than 2 once terminal velocity is achieved. Another factor KSP players typically forget in this discussion though- the ideal TWR is actually infinite (the higher the better) until the rocket manages to first achieve terminal velocity (most rockets start out stationary). Up until that point, you are moving at less than ideal speed (terminal velocity), and the faster you can catch up to terminal velocity the better. Finally, your ideal TWR goes down AGAIN once you start your gravity turn, if atmospheric drag is non-negligible at that altitude (otherwise, you will end up moving through the atmosphere at a speed greatly exceeding terminal velocity, and your path-length through the atmosphere has also increased vs. a "straight up" ascent). And you SHOULD start your gravity turn early (by around 12500 meters), and make it very gently/slowly, rather than attempting it all at once higher up (which poses both control issues and efficiency issues) Therefore, a BETTER TWR PROFILE (than TWR = 2 all the way up) would look more like this: Launchpad: TWR = 3 (best achieved with short-lived SRB's, such as custom ones from ProceduralParts mod with very low burn-times) 1000 meters TWR = 2 (terminal velocity should be nearly achieved by around this point- SRB's should be shed slightly before terminal velocity) 3000 meters: TWR = 1.92 (steering losses are going to cause a rocket to exceed terminal velocity, and create excessive drag from the tail fins) 5000 meters: TWR = 1.94 (steering losses become less of an issue as the rocket has more momentum in the proper direction) 8000 meters: TWR = 1.96 (steering losses less important still, thinning atmosphere having less impact on tail fins) 10000 meters: TWR - 1.98 (trends continue) 12500 meters: TWR = 1.94 (at this point, you should begin your gravity turn: so ideal TWR declines) 15000 meters: TWR = 1.84 (gravity turn becomes steeper, so TWR necessary to maintain terminal velocity declines- especially with lift from tail fins) 20000 meters: TWR = 1.72 (by this point, your should be burning at a rather significant angle relative to the vertical, in order to make your gravity turn) 25000 meters: TWR = 1.76 (gravity turn continues to deepen, but atmospheric drag is becoming much less of an issue) 30000 meters: TWR = 1.84 (atmosphere has become extremely thin, and rocket has reached a significant fraction of orbital velocity in the horizontal- assisting climb) 32000 meters: TWR = 1.96 (atmosphere continues to fall off, rocket continues to gain speed horizontally) 48000 meters: TWR = 2.04 (atmospheric drag is almost negligible, rocket should focus on achieving orbital velocity) This is a rather low-resolution and approximate sketch of an ideal ascent profile, and HEAVILY affected by the size of the tail fins and any other aerodynamic surfaces relative to the rest of the rocket. It is backed by extensive experience from my own rocket launches, however. All that being said, personally I prefer much higher TWR to reduce my play-time to orbit, a more important factor for me. I've also been known to make use of much lower TWR to reflect the real-life balance between fuel cost and engine cost (engines are MUCH more expensive than fuel tanks and fuel, therefore it is usually preferable to launch with a lower TWR than aerodynamics would suggest- although real-life aerodynamics dictate entirely different ideal TWR than in KSP...) Regards, Northstar