AeroGav

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About AeroGav

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  1. I built a Manta-Ray shaped SSTO once, guess who ended up flying it ? https://kerbalx.com/AeroGav/Voodoo-Ray For those of you not familiar with Acid House music You can probably guess what I was listening to while flying that to orbit...
  2. OK, I returned to my liquid fuel mk3. Removed the cockpit, fitted a mk3 to 2.5m adapter, then a fairing, under which went the reaction wheels, probe core and RTGs. That's the heat largely taken care of, but it's no longer an entirely fuel-free fuselage since the adapter holds a bit. Normally, my liquid fuel only ships have even more wing than this, it's more tankage for the NERVs and it improves lift:drag in the upper atmosphere. Also, you run cooler on ascent because you rise into thinner air at lower speed. But, that would result in this looking like an AVRO Vulcan and it'd have too much fuel capacity for the mission. It's only supposed to go to orbit ! The other problem was it felt a little underpowered. We were sluggish getting from mach 1.3 to mach 4 and used most of our fuel here. 2 Rapiers really need 2 Panthers, but we didn't have the engine mounts. So, i swap the Panther for a whiplash. A whiplash weighs nearly as much as 2 panther, but they have a fatter power curve above mach 1. To my surprise, the ship needed no tweaking after both of these changes and remained balanced. In fact I put it on Kerbal X, considering the thing ready for prime time. https://kerbalx.com/AeroGav/Lusitania
  3. Something a little smaller, and less fugly (but still LF only). Takes 22 Kerbals to Minmus. Has a docking port, 5 Vertically firing Vernier thrusters for landing. Uses 2 Nukes , one Rapier and one Panther. I had to clip the Rapier and Panther together to solve asymmetric thrust issues. The rapier can be shut down and panther put in dry mode for economic atmospheric cruising. I've tried to make it look like some 4.5 gen fighters i like, which means i didn't get to cram on as much wing as i like to do. Makes the flight to orbit a little hot, but it gets us there. https://kerbalx.com/AeroGav/Coimbra-PA-X-LR
  4. Outside of industry, where a steady beam is preferred for cutting, etching etc, pulsed lasers are common. You can make a higher instantaneous power output because of discharging caps and because the emitter has time to cool between firings. In nuclear fusion research as well as weapon applications, i think the pulses are between a millionth and a thousandth of a second. In weapon applications , you have the problem that vaporising part of the target creates a cloud of plasma that is opaque to further EM radiation. The plasma cloud from the beam hitting you absorbs the heat of continued firing, so rather than burning a deep hole in you, you get a superficial flesh burn, then the little puff of vaporised flesh gets heated to extremely high temperature by the continued firing and expands explosively. Problem is , the force of the blast goes mostly outward so again not particularly lethal. This is why the bad intention research is into a short pulses that do the damage before the plasma forms then hit again as soon as it dissipates. Alternatively, if we can figure a way to make efficient UV lasers, the terminal ballistics guys will be happy. They are used in surgery because they don't burn or create heat. Each photon has just the right amount of energy to break the chemical bonds of your body, converting organic matter to CO2 and water directly rather than by just heating it up until it burns or vaporises. Therefore you get a nice deep non-cauterised wound from which the victim bleeds rapidly.
  5. A few months back i made this high altitude fighter - https://www.dropbox.com/s/npvt6gz6fxy4ymc/scion ssto.craft?dl=0 Rather than install BDArmoury, I decided to mount a pair of nukes under the wings instead. There's small chutes on each nuke pod so they can land intact and be recovered after separation. Hypersonic L/D ratio. Quite a lot more lift up here than i thought there would be.. FAR experts, how's my L/D ? Made it to space, I was a bit disappointed not to have enough fuel to go anywhere interesting, but Val liked the view anyway. BTW I tried "firing" the nukes as torpedoes at a space station, but they don't go straight. For re-entry I held full back stick. For a "fighter" this thing really lacks control authority. Massive lift in the middle atmosphere means we don't even start to fall down into the heating zone till below mach 4,5 I released the nukes into the water just outside KSP, thanks to the chutes they splash down without damage. Coming in over the threshold.. Looks like i grossly overestimated our stall speed. Floated down the runway, wasn't ready to land until we were nearing the hills on the other side.
  6. Caught on camera... What do you think the Euro-NCAP rating of this spaceplane should be?
  7. Hydrofoils are great, but the water drag is a bit unpredictable - it can be as bad as you get from floats, or it can be much better. The problem is the game's aero data functions only show drag from atmosphere not water which makes optimising very hit or miss. I got lucky with this spaceplane, it can take off from the sea, get to orbit and fly to another planet without refuel. https://kerbalx.com/AeroGav/K133--Curlew
  8. Liquid-fuel only spaceplanes are a popular niche these days, but they're mostly bitty little mk1s. I fancied trying something bigger, particularly in view of the fact the fuselage had no room left for oxidizer after I'd finished stuffing Kerbals into it. Gross Mass is 86,105KG Fuel Mass is just 24,000KG. That's about the lowest fuel fraction of anything I've ever seen make orbit. After working on this for 5 hours, I took these screenies from my first successful orbit. Now I need a lie down. Got there with 550 out of 4400 remaining, but I reached 103% of max cockpit temp on the way up. I could have pitched up or throttled back but i didn't want to run out of fuel again. In hindsight we'd probably have still made it if i had. I kept adding more strakes to this thing to increase fuel capacity, and lengthening the nose to try stop the cockpit burning up. Unfortunately the stuff you put on the front is much smaller diameter than the cockpit itself so doesn't give all that much protection. There's even a heat shield between the 1.25m nose stuff and the cockpit, but it doesn't seem to do anything. Power is 2 Rapiers, 1 Panther, and 4 NERVs. Relax, it may look like we've got draggy radially attached nacelles with a blunt front , but those were created with the offset trick. I've actually got a quad coupler on the mk3 engine mount's 2.5 node which the nukes hang off, and the Rapiers and Panthers were attached one at a time to the 1.25m nodes, then offset https://www.dropbox.com/s/5fbz39v4o6cmoco/SAAB Straken.craft?dl=0 edit - ok that's also a 41% payload mass fraction, if we take the passenger cabin and mk3 cockpit as "payload", which is higher than the winning entry of the recent payload mass challenge... .
  9. I've spent a few hours with the big one. The main problem is it is simply too heavy for the 2.5m tank to fuselage joint, even a 2g pitchup maneuver causes breakup, can't imagine trying to land the thing in one piece. You could just swap the side pods to mk3 fuselage sections, but i was able to take a lot of the weight out of the ship in my version. Regards to weight, you've got a classic case of too many rapiers (which weigh 2 tons each), meaning high dry mass causing low delta v, which you then add more fuel to compensate, then more engines when it won't go supersonic etc. Yours was coming in at 250t laden, mine was 110 with same cargo. My rule of thumb is one RAPIER per 50 tons or so, one nuke per 30 tons, and some booster engines with good low speed performance to help it over the sound barrier. My version of your ship had 4 nukes, 2 rapiers, and 3 panthers. A 1:1 rapier/panther ratio might have been better. To make such an "underpowered" ship work you need low drag. There were a few part attachment things causing excess drag on your design - The mk3 engine mount has a 2.5m attach node on the back which you are not using. Unused attachment nodes create huge drag, as do mismatched ones - attaching parts that are the wrong size for the node. Every node should end in something pointy. Jet engines (like Panther, Whiplash) are low drag, but rocket engines and rapiers are not because they have attach nodes behind them, which create drag if left empty. You can use the reverse cone trick to nix this drag from rapiers. No cones on back of Rapier engines - see above. Video here showing me apply reversed cones to my engines - Wings not angled up at 5 degrees. This means the whole body of the plane has to fly nose up to get lift, which greatly increases body drag. Note, if you angle the wings up (this is known as adding incidence angle) it is important to remember the lifting surfaces at the front must always have at the same or slightly higher incidence angle than those behind, otherwise you can end up with the rear wings stalling first and the plane going into an irrevocable deep stall. The second issue with the design was much harder to solve, it's what i spent most of my time on and sadly was only really able to Kludge it whilst retaining some elements of the original appearance. You see, those engines at the back designs look very sleek but don't really work out for a KSP cargo plane. Sure, on takeoff the fuel and cargo up front might balance out the heavy engines to the rear, but once you've burned your fuel off and unloaded stuff, it's going to be dramatically more tail happy for re-entry and landing. You either end up too nose heavy to fly efficiently (or at all!) on launch, or too unstable on the way back. Ideally, you want to balance the plane so its CG is in the middle of the cargo bay when empty. This is done mainly by shifting engines around. With CG centred on the cargo bay, there will be no shifts after unloading cargo. Then, add fuel tanks fore and aft, so that there are no changes with either oxidizer or jet fuel burning off. If you're really thorough you'll check each separately, especially on a beyond low orbit design with a lot of LF. Strongly recommend RCS build aid for this, there's an unofficial beta version that supports KSP 1.3 Anyway, with my version of your plane, i had a struggle. I reduced the number of nukes and pushed them as far forward as i could without completely getting away from your layout. I had to find ways of getting more fuel in the back of the plane, without pushing the heavy engines any further back. Hence, the tail fins that are made from big-s strakes. I couldn't get fine enough control over fuel capacity fore/aft by adding mk3 tanks, so i just added more cargo bay and put jet and rocket fuel tanks within those. That's wasteful of volume, mass and drag but i suppose the only alternative, other than making another Skylon clone, is to leave tanks partly filled, which has the same drawbacks. Note that the panthers look like they are radially attached, but they are in fact on the mk3 engine mount's 1.25m nodes. I used the offset tool to make them look like nacelles (boeing 727 forever!). There's a 2.5m bicoupler on the central 2.5m node, which gives me two more 1.25m nodes on which to hang the rapiers, which are coned. https://www.dropbox.com/s/zurf48yy6udppt1/Duna Shuttle Aerogav2.craft?dl=0 Action group 1 - toggle nukes. Action group 2 - rapier switch mode Action group 3 - turns off the rapiers and nukes, switches panthers to non-afterburner mode. Useful if you need to fly around a bit after re-entry. Flight profile - climb subsonic to 5km, it will start to level off naturally at this point unless you yank the nose up to a draggy degree, so just hit the prograde assist and let it go through the sound barrier. Probably best to keep it on from that point anyway. At 1300m/s, start the nukes. At 27km, switch mode on rapiers. At 35km, remember to change Navball back to Surface mode to avoid flying with a negative AoA. After re-entry, I test out the rough-field landing capability (IOW I CBA to aim for the space centre)
  10. No one has mentioned this yet, the most important factor is how close the cockpit is to the front of the ship. The mk1 cockpit may have a low heat tolerance, but this one often shows no heat bar at all on re-entry - https://kerbalx.com/AeroGav/Stretch-Ray The mk3 actually gets quite close to exploding, because you've got no choice but to put it right at the front. Another important factor is wing area relative to weight. Glider-like designs like the above ship generate a lot of lift, and tend not to fall out of the upper atmosphere till you're below mach 4. This reduces the heating rate. If you re-enter this plane with a low AoA it will glide all the way around Kerbin, and willl briefly show a heat bar as it passes through 1200-1100 m/s due to the prolonged heat soak, but that's about it. I also did a video explaining how to target KSC (need to have annotations turned on, there's no talking) Edit - there is another advantage of pushing the cockpit back. Sometimes, we make only "good" landings instead of excellent ones. To wit - KSC landings are generally easier due to the thicker atmo (lower speeds) but if you're not perfectly lined up with the runway, an inline cockpit can lead to a better outcome -
  11. I generally go with one jet engine per 30 tons of gross takeoff weight, a mix of Whiplash and Rapier . The Whiplash fatten out the bottom end of the power curve making it easier to get supersonic. The max top end speed you can get is soft capped by the engine velocity curve , meaning that adding more engines to get faster than 1400 m/s air breathing runs into diminishing returns hard If your craft does not have any part attachment issues causing excess drag you should be able to get through the sound barrier easily. Generally I use up to 20% of my fuel getting to air breathing top speed. From 1400m/s, you need another 900m/s velocity to make low orbit. My designs have a low thrust-weight ratio so gravity/drag losses mean my delta V (as reported by Kerbal Engineer System) has fallen by up to 1200 or so by the time we reach orbit, but you shouldn't see losses worse than that. Nukes, I generally bring one per 15 tons if I'm making an oxidizer free ship. A minimal amount of oxidizer allows you to halve that number of nuke engines. Wings - I prefer adding more wing to my designs, but a lot of it is down to individual preference. After takeoff, I prefer to climb to a higher altitude where drag is less, before levelling off and attempting to penetrate the sound barrier. However, as the air gets thinner you need more wing to support the craft at the comparatively low speed, without having to yank the nose more than 5 degrees above the prograde vector, which generates drag. At a minimum, you want enough wing area that you can fly around at 7km altitude , subsonic (under 250m/s) without having to yank the nose more than 5 degrees above prograde. I did try the other method of getting supersonic, by just doing it at sea level , flying level after takeoff till over 440 m/s with tiny sub wings. But I found this used a lot of fuel, drag is huge at zero altitude, it's partly disguised by the massive amount of power your engines have down there but the fuel flow rates are scary. Liquid fuel only SSTO need even more wing area in my opinion, motor-glider levels of lift:drag ratio help a lot when getting a craft to orbit with relatively low thrust (this is a low tech panther/nerv ssto that can go to the surface fo the mun and back)
  12. I'd say the OP simply has centre of mass a bit too close to the centre of lift, he needs to allow a greater margin of safety given that the centre of lift indicator of the stock game is not 100% accurate (doesn't calculate aero forces from parts that don't have a lift rating in their description). Deleting the canard removes some lift from the front of the ship but you'd get the same overall effect just moving the wings back a little. The jet fuel tanks are slightly in front of CoM so it's possible the plane's becoming unstable from the slight shift that occurs towards the end of the jet powered phase as most of the jet fuel is used. If you're having issues making the craft sufficiently stable in some phases of flight, while not sufficiently controllable in others, you're better off putting the cargo bay right over the CoM, instead of ahead of it as he has here. Might run into issues with not taking off with a full cargo bay and flipping out on an empty one. Also, the main fuselage is a mk2 but it's transitioning straight into a mk1 sized reaction wheel at the back, without an adapter. Need a mk2 to mk1 adapter or you end up with a ton of drag.
  13. OK, I had a go at recreating the craft from the picture. I didn't realise you had a cargo bay, instead of a fuel tank immediately behind the cockpit. This means you have a similar amount of fuel ahead and behind CoM, it doesn't move all that much and actually goes forward as it burns off (red dot) But, my CoM ends up much further aft than yours, which is halfway between the two short rocket fuel tanks. You must have a heavy payload in the cargo bay, and once you unload it, the ship becomes tail heavy. My "copy" had no cargo.
  14. Problem 1 - CG moves aft as fuel burns away Let's briefly add up the major dry mass items of your plane - Ahead of CG (by approx 2 long mk2 fuselage sections distance) = cockpit , 2 tons Behind CG (by approx 2 long mk2 fuselage sections' worth of distance) = NERV, 3 tons Behind CG (by approx 0.5 long mk2 fuselage sections' worth of distance) = 2 x 1.8 ton whiplashes Behind CG (by approx 075 long mk2 fuselage section's worth of distance) = 2 x 2ton rapiers You can see that you have far more dry mass behind CG than ahead of it. On takeoff, this is countered by having most of your fuel stowage in front of CG. But once that burns off, your CG will move aft. The easiest way to avoid falling into this trap again is to get RCS build aid, it shows a red dot which is where your CoM will move to when the tanks are empty. Problem 2 - Blue indicator not allowing for aero forces on non-wing parts Even with your CG/CoM at its furthest forward position, before the fuel burns off, you have 66% more fuselage length in front of CG than behind it. The stock blue indicator only takes account of wing and control surface parts. I strongly recommend you get CorrectCoL mod installed so it takes account of aero forces acting on every part, including the fuselage. Makes airplane design much less prone to trial and error. I suspect your CG is way further forward than you think. RCS build aid and CorrectCoL are very small mods with a tiny memory footprint that won't affect loading speed, because they don't add any new parts and therefore have no extra textures to load on startup. .
  15. Well, the RTGs are coming back to Kerbin so money is not an issue. With the fuel cell, you're going to want to more efficient big converter or you won't come out ahead, correct?