AeroGav

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Everything posted by AeroGav

  1. Only these screenshots. It's not very stable in yaw (not long fuselage, tail too small) and knowing what i know oow, I'd use Bg S strakes instead - more capacityy of fuel per mass and drag. airbreathers still attached getting on my nervs... a bit hot at mach 13. lost the small nose cone.. had to throttle back slightly at this point to avoid losing any more parts, but not too much or you don't make orbit. procedural faring for mk2 i think
  2. Yeah a lot of work goes into making something in FAR. A high speed airplane that can land at speeds the small retractable gears can survive ends up looking like my plane, lots and lots of wing parts, and sophisticated high lift systems. No way in hell of getting it under 30 parts nor of getting landing speed below 60m/s , which the fixed landing spats probably cant handle
  3. Can changes in the hardware of the pc running the game cause differences in behaviour like this ? If you're getting into rounding errors, then surely FPS differences will influence those ? Does the Unity physics engine take advantage of different code paths on different processors (AVX etc) which might cause differences in the way floating points get rounded up or down, different precision levels?
  4. Might be easier if the carrier is moving, since that means less speed difference between the carrier and the airplane.
  5. AeroGav

    FedEx CHALLENGE

    Damn, after rewatching that video i realised i took off with the parking brake set. Thought it was sluggish :-/
  6. AeroGav

    SSTOs! Post your pictures here~

    Mk3 cabins seem quite rigid. I think if you attach one pair of big S to every mk3 fuselage you'll be ok, but as you say there is a limit to how much force you can put through each wing/fuselage joint before it snaps. I have a non-nuke version of that long plane that is 30% heavier and has half as many wings, the force per wing is higher and when you pitch up to take off, it is very easy to snap the wing.
  7. AeroGav

    SSTOs! Post your pictures here~

    I;ve been busy the past two weeks https://kerbalx.com/AeroGav/Monstrosity-225L https://kerbalx.com/AeroGav/vagabond-ssto https://kerbalx.com/AeroGav/Sparrow Anyone need a 43 seater shuttle ? Probably not..https://kerbalx.com/AeroGav/Hammerhead5 https://kerbalx.com/AeroGav/SX-60L Of them all, the one that earned the most downloads and likes by far is the one below, a mod of someone else's bird. This is despite the fact it's probably the hardest craft to fly that i've posted on KerbalX in years. It seems looks really are everything, not handling, not capability, and even niche seem to affect that much. Finally , I'd like to showcase this Panther NERV Tier 7 career plane. Only needs the Tier 2 Research building. every component other than the nuke engines are the lowest tech items available https://kerbalx.com/AeroGav/Foxbat Kind of reminds me of a Flanker, except for the canards and lack of tailplane. The base version will reach 4million km ap and is easy to fly. Here's an example outfitted with drop tanks, which can explore cis-munar space https://kerbalx.com/AeroGav/Foxbat-with-drop-tanks https://i.imgur.com/qiq9vgr.jpg
  8. Another Tier 7 for you all, apart from the nuke i've tried to keep everything else as low tech as possible https://kerbalx.com/AeroGav/Foxbat It can be outfitted with drop tanks like so https://kerbalx.com/AeroGav/Foxbat-with-drop-tanks
  9. AeroGav

    Panther NERV Career Spaceplanes

    Preamble Most people building Space Planes use RAPIER engines, however you are unlikely to see those till the very end of career mode, being Tier 9 (1000 Science points). While not as popular as RAPIER designs, Whiplash Space Planes aren't uncommon, but as Tier 8 engines, they have a Science cost of 550, which means you aren't getting them without a max level R&D building. And that's a hugely expensive upgrade, given that funds tend to be harder to acquire than science points. So, for 90% of our career game, the only realistic engine option is the Panther. It's a fine engine, but it's thrust output peaks at mach 2.5 and goes to zero by mach 3. Realistically, your space plane is not getting much above mach 2.5 on jet power, and that means your rockets need to add another 4.5 mach's worth of velocity to reach orbit. On chemical engines, this requires a very large fuel fraction that leaves little room for payload, and that payload fraction soon disappears altogether if you attempt to go beyond low orbit. However, you can get NERV engines with a Tier 2 science building, and with over twice the ISP you don't need to turn your craft into one big fuel tank just to reach orbit. These engines do have a miserable TWR of course - the measly LV-909 Terrier has the same thrust, but weighs just 0.5 tons instead of 3. Your vessel is never going to have a TWR > 1 or even close to it. For a rocket, this is a major problem. However , you have to remember that your spaceplane is an airplane and it does not need a TWR over 1 to fly. The engines will be thrusting horizontally to accelerate you to orbital velocity, the wings take care of gravity, to stop you plummeting to the ground. So long as your thrust exceeds drag, and the wings are making sufficient lift to counteract gravity, you will go to space today. Lift to Drag Ratio Angle of attack is the difference between where the nose is pointing and where the airplane is actually going. For wing and control surface parts, lift and drag are both zero, at zero angle of attack. As AoA goes above zero, lift increases rapidly, but is subject to diminishing returns. After 30 degrees , lift starts decreasing with further increases of AoA because you've stalled. Drag increases steadily with angle of attack, all the way to 90 degrees. Non wing parts also produce more drag with increasing AoA, however they still produce considerable drag even at zero AoA. They also produce little or no lift. The important things to remember from this - In supersonic flight, best lift to drag ratio happens at about 5 degrees ApA. Unlike real airplanes in KSP, the wing generates less than 20% of the drag your craft is producing. Some parts are very draggy. Solar panels, even deployable ones, need to be in a service bay. 1.25m bicouplers are meant for use on rocket stacks, and are very draggy on an airplane. Mk2 fuselage parts should be avoided, they make 250% of the drag of a mk1 part of the same length and fuel capacity. Mismatched attach nodes create massive drag. A 1.25m attach node should only ever join to another 1.25m node. If your fuselage is tapering down to 0.625m, use an NCS adapter to smooth the transition. If it's flaring out to a mk2 cargo bay, use a mk1 to mk2 adapter short. That second point is counterintuitive - people often reduce wing area thinking it will reduce drag, but you end up needing a higher angle of attack to get the same lift, or flying at a lower altitude where the air is thicker. When on jet power, a smaller wing can improve performance, because at lower altitudes your engine can make more power. Once you've staged in the nukes however, you are burning fuel rapidly and it's all about getting the best exchange rate possible when converting your precious forward velocity into lift. This means, angle the nose for 5 degrees above prograde. It doesn't matter whether prograde is showing a climb or a dive -- just point 5 degrees above where it is pointing. NERV in practice - Building an Airplane The basics aren't all that demanding One NERV for every 12 tons or so of airplane One Panther for every 2 NERVs About 30% of the craft's weight should be fuel. 2 MK1 liquid fuel tanks are enough to get a basic 2 nerv design into orbit. A lift rating of 7 to 10 per 20 tons is about right. There is a lot of wiggle room here, but in general more wing makes the NERV powered part of the climb easier, at the expense of the jet powered part. Avoid using mk2 parts due to their high drag, only if you must have a cargo bay. Mk1 parts are not as heat tolerant, so use an inline cockpit as it will be protected by the nose cone, intake or service bay in front. The majority of your effort should be in making sure the airplane is stable and easy to fly with precision. This will make the flight more enjoyable and allow you to maintain the angle of attack values where lift to drag is good. The major issue is balancing the heavy engines with non fuel parts, and keeping the fuel amidships, so there is no centre of mass shift between full and empty. For example, this works - Cockpit, Passenger Cabin, Engine Nacelle intake, 2 fuel tanks, then our Panther. The nukes are either side. RCS build aid is on , but you can't see the red ball because the dry CoM is in the exact same place as the wet one. We have 6T liquid fuel for a total mass of 17T. About 30% fuel so that's good, the engine to mass ratio is good too, leaning slightly on the overpowered side. Now we just add wings. Canard or Tailplane design is totally up to you, just make sure your wings don't get in the way of the exhaust plume. Since the first pic is of a canard version of this airplane, let's go with a tailplane this time. And there we go . As you can see, Kerbal Wind tunnel shows if your design has enough power to go supersonic, and what its top speed will be at every altitude. Note, it takes account of drag from landing gear, so you need to raise the gear before running this analysis, or just do it before fitting any like i did here. Note also that you can bind your nukes to an action group so you can turn them on between 300-400m/s if your design has trouble busting mach 1 on jet power alone. Note how the blue arrow is towards the back of the yellow ball. Centre of lft must be behind centre of mass, but excessively aft CoL will suffer excessive drag, because you need to generate a lot of force with the control surfaces to get the nose up to make lift. Large deflection angles on your control surfaces are draggy. That is why it is better to fit generously sized ones and use the "limit authority" slider than use tiny ones that are maxed out. Because we used RCS Build Aid to ensure that our centre of mass does not change as fuel burns off, we can get away with having CoL fairly close behind our Centre of Mass. Test Flight A complaint I often hear about spaceplanes is that you waste 20 minutes getting to altitude on every failed attempt. However, there is a lot you can learn without getting above 500m. Take SAS off, and attempt to stall the plane, how controllable is it? Throttle up and down, does the nose rise and fall, have you got a centre of thrust problem? Does it break mach 1 with one panther per 20 tons? If it can do so, without being ridiculously overpowered, then its not got any drag problems that will stop it from flying under NERV power. Of course , Kerbal Wind Tunnel will tell you this without even needing to leave the hangar. If all of the above is true, and you are flying a sensible profile, and have stuck to my recommendations regarding engines per ton and fuel mass percentage, it should make orbit !
  10. AeroGav

    FedEx CHALLENGE

    I 'm rubbish at gravity assists. Had about 880dv left coming into jool system. a combo of aerobraking and grav assists should be possible, but i spent 4 hours bouncing back and forward. https://www.dropbox.com/s/tj0lq19a0njhyjv/POCKET BILLIARDS.sfs?dl=0 That's the save file if anyone can do better. Eventually did a laythe-tylo-laythe braking manoeuvre that drops my PE about 10km inside jool atmosphere and has my AP halfway out to Vall, used the cheezy technique of going to the reacking station when i didn't want more aerobraking off jool, and riding the plane when i did, gradually dropping my orbit bit by bit till finally got a laythe encounter at a speed i could aerorake into the atmosphere from. When it came to landing, i discovered this craft isn't really robust enough to land on uneven terrain with 60 tons of ore aboard. My designs usually have no problem setting down on laythe, but this took a dozen attempts and a bit of luck. I used hyperedit to bring a rover with a resource converter onboard to our airplane so as to unload the ore and refill the fuel, and set off for home. Without ore aboard, takeoff was easy and we still had 4800dv left after getting into orbit around Laythe. A simple direct burn back to Kerbin was done, upon entering Kerbin SOI we had over 2000 remaining. We were too fast to aerobrake all that off, and could only drop to 57km without damage, so i could have used a resonant orbit to get a second nibble at aerobraking at a more reasonable speed - but that would have added 20 years to the mission ! So I just retro burned shortly before dropping into KErbin's atmosphere, about 1000 m/s worth, which in turn let us drop deeper and aerobrake more without blowing up. 3 or 4 passes later, we get down. Will ad vids, but feel burned out by this . Edit - video Well, did the Krebin to Laythe leg in under 3 years and that was 60t of ore, (departed day 226 of year 2) but not really so practical, i should have used a mk3 airplane for this payload, and it wasn't all that much fun beyond constructing the aircraft ! Better luck for the rest of you!
  11. AeroGav

    FedEx CHALLENGE

    Because I think the OP does not want the cargo to be transferred. It stays in same vehicle from surface of kerbin to surface of laythe. Also my spaceplane doesn't have that much extra dry mass compared with a dedicated transport - 2 rapiers, 3 panthers, and a bunch of wings - but you'll need to add mass to the interplanetary ship to make it landable.
  12. I'm not sure they are OMNI, I have had problems when inadvertently mounting them backwards on a plane before (engine starts coughing once speed gets up). Intake air is based on two values, a static one and a ram air rating. The ram air rating goes up with increasing speed , though some of the low speed ones (radial supersonic intake , i'm looking at you!) start heading back down to zero again once you go past their peak. The static rating is fixed, and the pre cooler has the highest static rating of any intake, so it will work mounted backwards up to about 50m/s, then the negative ram air number overcomes the static rating and causes insufficient air.
  13. AeroGav

    NASA SLS/Orion/Payloads

    Boeing is a private company. What NASA have been perfecting, for the past 30 years, is an arrangement that combines the very worst aspects of government institutions (conservatism, bureaucracy, make-work g) with and private greed (profiteering, doing the absolute bare minimum) on monopolistic, open ended cost plus contracts that reward failure. NASA should either do thing in house, "in source" like SpaceX is doing, or tender them out on dollars per ton contracts. I wonder where we'd be right now if the SLS and Constellation money had gone to SpaceX and Blueorigin instead.
  14. I just reread this. Up until the the bit about drag, the basics of centre of mass, centre of lift and thrust torque still stand. The drag stuff is now wildly incorrect. The stock aero model does not care about wing shape, Hypersonic wing vs subsonic wing can be the same shape. Just get your centre of mass / centre of lift right and avoid the part attachment mistakes that cause abnormally high drag.
  15. AeroGav

    FedEx CHALLENGE

    I'm struggling to stay focussed on this mission because at the end of the day it's just a flight to Laythe, but anyway. Here is footage of the NERV engine ascent to orbit. This thing is pretty underpowered, only 6 nervs pushing us. Fortunately , our lift to drag ratio is pretty damn good, over 3.5 to 1, which makes it all possible. The 2.5m crewed bits and ore tanks have surprisingly low drag, and wing parts tend to bring up the average too - and we got a few of those (!) After reaching orbit, we dock with my orbital fuel depot, which is resupplied from a Minmus ISRU operation. The place is called Gus' Gas, and like most truck stops they offer a few extra amenities besides fuel. Haldorf purchases one of the giant Terry's Chocolate Orange's and the 4 x 2L K-Kola Value Pack. Tramal takes the other Orange as well as a paperback called "50 shades of green", while Padorf uses his jetpack to obtain a series of periodicals from the top shelf of the magazine rack. Sadly for me the actual pumping gas part was no fun at all. I usually build self refuelling spaceplanes with their own mining gear, having to manually transfer to every damn strake on this airplane was a miserable job - and i've got to do it all again when i reach Laythe..
  16. So, NASA recently proposed the "Lunar Gateway" station as a payload for their SLS expendable megarocket, which has been under development in some form for the past 30 years, but is finally expected to fly within the next 2 - 3. In turn , Lockheed have used this as an opportunity to reveal their design for a re-usable lander, capable of ferrying astronauts from the lunar gateway to the moon's surface and back. Scott Manley simulated this vessel in KSP, with a few realism add-ons : Whereas Apollo used separate Ascent and Descent stages, a re-usable vessel needs to do the whole round trip in a single stage, and this seems to be a problem. Despite using Hydrolox , the mass ratio is miserable, 40 tons of propellant for one ton of payload delivered to the surface. If all 40 tons of propellant have to be shipped from Earth to Lunar orbit via expendable SLS rockets, I can't see re-using the lander working out any cheaper than a disposable design that needs less fuel (total mass shipped from earth) per trip. I'd appreciate feedback on that point, but my real question is, is there any possibility to IRSU oxygen from the lunar regolith , and how would that change the economics of this vehicle's operation ? The long term goal of lunar exploration is to find water ice that can be split into hydrogen and oxygen, but it is only thought to exist in permanently shaded craters near the poles. An extensive prospecting operation needs to be conducted first, then we need to set up a base with remotely located solar panels bringing power for our ice mining operation. Volatile and light elements are rare on moon, which has no atmosphere, magnetic field or strong gravity to help it retain such things, and the surface heats to several hundred degrees in the daytime. If you just want oxygen though, that should be much easier. The moon is 40% oxygen, by mass, most of it consisting of various metal oxides and silicates. Would it not be much easier to extract oxygen from these oxides (smelting metal ore in a solar furnace?) which exist practically anywhere, From what i understand, the LOX component of hydrolox propellant weighs 7 times as much as the LH2 itself. So, even if we still have to bring all the hydrogen for the ascent down to the surface with us, the ability to refill LOX will greatly improve the amount of payload that can be carried per trip, and if only liquid hydrogen has to be brought up from earth, that's far fewer SLS refuelling trips needed for our lunar propellant depot, per trip to the surface. Win/Win. Finally, if you've got unlimited oxygen, would there be any point playing with the fuel air ratio of the engine? I understand hydrogen rich gives better ISP and more stoich gives better thrust - in these unique conditions, would it even make sense to lift off from the lunar surface at a slightly oxygen rich ratio, gradually getting richer as time goes on (need for high thrust getting less, also KSP teaches us to burn our low ISP fuels first? ) Anyone know how the exhaust flame would look ? The Space Shuttle main engines ran only slightly rich of stoichiometric , and had an almost invisible, white flame. Hydrolox upper stages tend to run richer, and produce these beautiful blue colours ..
  17. AeroGav

    Compare and Share!

    Ah sorry I didn't realise the discussion had moved on to Ferram Aerospace. IT is much more realistic, and avoids the drawback mk2 parts suffer in stock aero
  18. About a year ago I started a Ferram career game. Everything takes so much longer to design , looking it the craft files it appears i lost interest in the middle of designing a two stage to orbit panther/terrier spaceplane (panther gets dumped) Anyway this appears to be my Juno terrier ssto, i can't remember how it flies because i don't have a ferram install to hand... can't remember if its supersonic or not on jet power. If not I assume the highly swept planform was just to lower drag when running on Terrier power. TWR with the Terrier is only 0.49 to 1, so it needs to have good lift drag ratio in supersonic flight https://www.dropbox.com/s/fsnx3rcm6ikxcr6/Junovator.craft?dl=0 Obviously, high tech stuff like retracting gears and inline cockpits would disqualify it for the challenge.
  19. AeroGav

    Compare and Share!

    It's all there in the F12 menu The Big S Delta Wing is generating 15 times as much lift as the MK2 fuel tank, for half the drag. It is holding 75% of the fuel too, for half the drag. The MK1 fuel tank is about 40% of the drag for the same fuel capacity. Cylindrical tanks are best at holding fuel as far as weight is concerned. But, the thing which holds most fuel for a given amount of drag is the big S wing strake
  20. Then what do you think about Phobos and Deimos ? Better ?
  21. Alright, they seem to be avoiding making any direct claim of performance in the manner you describe. I don't know what your background in chemistry is, i don't work in a relevant field and only have my schoolboy chemistry to fall back on. I just know this has been touted as the ISRU process that is to take place on the moon, long before water electrolysis was mooted, since there are doubts about finding water ice, in sufficient quantity, concentration and sufficiently close to the surface, to be amenable to in -situ utilization. I presume those proposing oxygen extraction from regolith knew what they were talking about and weren't just trying to con gullible politicians for funding. Obviously the technology is not mature.... but it seems worthy of further development. I mean, if Orion and SLS are considered worthy of funding, so is this ? Or do you have some expertise in the field so you can say it is a waste of time ? Again, can you make your position clear on this ? Do you think this type of ISRU is a good idea ? a bad idea? or do you have no opinion? What about lunar ice ISRU? If you're not keen on this approach, what is your vision for space exploration - i presume you have one, given that you play KSP....
  22. According to the powerpoint i linked, they used temperature of 1600, and electrodes of iridium and molybdenum. The regolith has a composition of 47% Silicon dioxide, 17.8% Aluminum dioxide, 10% iron oxide. I think they were only bothered about reducing the iron ore, the rest can be thrown away. It's not like there is a shortage of Regolith on the Moon.. I'm noticing a pattern of naysayers which is fine, valid objections, but knocking something down is easy. If you think this is a daft idea, what do you propose we do instead? Is it any less plausible than a lunar gateway station, a reusable 62 ton lander, all supplied entirely from earth via the SLS ?
  23. AeroGav

    Compare and Share!

    There is only 40kg difference in dry mass between mk1 liquid fuel fuselage and mk2 short liquid tank. The problem is drag and drag alone.
  24. I did a bit of reading around, and used some rocket equation numbers from this site - it's a nice little online calculator that saves you from having to understand the math, you just plug in any three of the four relevant variables, and it calculates the one you left blank ISP Delta V Starting Mass Ending Mass http://www.quantumg.net/rocketeq.html Apparently, the best ISP for hydrolox engines comes when you burn 4.8 tons of LOX for every ton of Hydrogen. The space shuttle main engine ran less rich at 6 tons of LOX per ton of H2, and gave up a percent or two ISP for a less bulky and draggy LH2 tank as a result. Stoich is 8 to 1. The RL-10 engine has experimentally been run as lean as 13:1 , and did not take any damage. Apparently, it's all in the boundary layer cooling, if cool enough, the engine is protected even if the boundary layer itself is lean. Variants of the RL-10 are capable of adjusting mixture ratio in flight and this was done on later Apollo missions, though not to such an extreme degree. https://yarchive.net/space/rocket/fuels/fuel_ratio.html So, if the lander weighs 19T empty and needs 2500dv to go from the surface to LOP-G, it will use 14.5 tons propellant for the ascent. I ran the calcs for 6:1 (SSME ratio) and got 2.07T LH2 and 12.4T LOX. Not having to carry that ascent oxygen all the way from the lunar gateway is potentially another 12.4t payload , or if we're only carrying 1T down, then it only has to depart the gateway with 18.9T of fuel instead of tanks brimmed to 42T. Of course, that assumes you're topping off the oxygen tanks at the lunar gateway as well as on the surface, which you probably wouldn't do. If the lander gets all its oxygen from the surface facility and all its hydrogen from earth, then basically each tank is having to go the full 5000dv between replenishments, and our mass and payload ratios go back to the starting point - 1 ton of payload for 42 tons fuel used per trip. However, at 6:1 fuel ratio, that means we're shipping only 6 tons of propellant from Earth (Falcon Heavy in Re-usable mode?) instead of 42 (expendable SLS block b?) As regards to the process of extracting oxygen from regolith, https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090018064.pdf Molten oxide electrolysis looks the lowest risk - basically melt the lunar soil, then electrolyse it to separate gaseous oxygen, and you end up with molten metals (mostly silicon and aluminum, some iron) as a byproduct. It looks like this process can scale down to pretty small sizes, but to make the amounts of oxygen this monster lander needs would take substantial plant - or a lot of time. Given the putative SLS launch cadence of once every 2 years however, maybe that's not such a big deal. As for what @DerekL1963 said, yes ISRU is only useful to repeat visits to the same place. As I understand it, the plan is to prospect the moon with robotic rovers, then send manned missions to investigate any promising sites they uncover. So, that makes it sound like we'll not be doing repeat manned missions to the same spot , until such a time as a full base is established with lunar ice ISRU. Or will we ? If Ice is proving elusive, does there come a point where we just go with this setup to tide us over ? Or after finding a promising crater, is there going to be a substantial period of time before a base is established and ice harvesting gets going - perhaps several manned missions would be needed by base architects, and a multitude of cargo missions while the base is actually constructed. This kind of operation could make those flights considerably more efficient.
  25. AeroGav

    FedEx CHALLENGE

    If the theme is Fedex, that means commercial trucking ops, meaning an emphasis on rapid transit, low costs (as much re-use as possible, or the cheapest expendables possible), and you would expect infrastructure (truck stops) to exist. So, would an SSTO, with a gas station at Minmus and another in the Jool system be ok? I started to build an SSTO with 4 ore big ore tanks (60T) but it has quite a short body, and it's going to look a bit ridiculous if i keep attaching more Wing strakes to add fuel. 40% fuel fraction on an oxidizer free design should get us there nonstop, but makes for a v big ship edit - hmm just test flew this thing, only gets to orbit with 550 m/s left. It's just a bit small for what it's carrying - Dry Mass 49.5 Tons Ore 60 T Liquid Fuel 49.5 T Gross 162.5 Delta V with full tanks is just a hair over 2800, so even if I top it off in Kerbin orbit, it's not got a huge amount to spare for the Jool Transfer burn. Hmm.. should i keep going with this airplane or scrap it for something with a longer wheelbase? https://www.dropbox.com/s/woyypbun7fegshs/Rita Orer2.craft?dl=0 Definitely needs more Strakes...