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Everything posted by AeroGav

  1. AeroGav

    Round-Kerbin Planes

    This one of mine can maintain supersonic flight in panther dry mode, the wings are angled up where they attach to the fuselage so it still makes lift when set to prograde hold. In fact this eliminates fuselage drag and serves as a type of autopilot, making it much more efficient. Also note, the very high cruising altitude. Fuel burn is very low at cruising altitude , so it can circumnavigate.
  2. So, I got thinking about making something that could do the job of Matt Lowne's old ship, Argus, in 2018. Requirement is 4 seats, 4k delta V in orbit, and at least a CRG-25 bay. The adapters either end of the cargo bay add waay more LFO tankage than i'd want (looks to be enough to add about 3-4 mach numbers to something this size), so i'll scale up to a CRG-50 right away and see where that gets us. The delta wing makes it look like it's doing 0.5C while parked, unfortunately the CoL is WAAY too far back. Yes, I accidentally clicked away, and lost, the front section, but it didn't move it forward much and unless i give it canards like Dumbo's ears we'll still be too far back. I really want the CoM to be in the middle of the cargo bay so it handles the same laden or not - and fuel needs to be distributed either side of our CoM too. I tend to build lower powered designs that compensate with low drag. But it will only have low drag if prograde hold keeps us within a degree or so of prograde throughout the the mission. One other problem with this sleek wing - I need to find a place to put on 2 RAPIERs and 4 NERVs. Once I add incidence to the wing, there won't be any place i can attach these to the body and not have the efflux impinge on a wing surface - unless i put all the engines at the back - which will put our dry CoM way behind the cargo bay. Anyway, I digress. Subject for tonight, Rhinoplasty. This reminds me of Sesame Street character, can't remember the name. Quack ! Ramp intakes, sloping inward. Hungry for Krill.... Ramp intakes sloping out. Pointy. Looks like i used some old parts off a Colonial Viper. Edit - craft name will change, don't worry. The pre-alpha had the cabins between the panther engines and rear tri couplers, it looked a bit medicinal, you could say.
  3. I had a play with this and tried to make a Tylo capable vessel as you said you were planning. The goal was "easy" flights to Tylo without complicated Eve/Kerbin Flybys (I can't do those!). It's not single stage but mostly re-usable - the two whiplash and single panther dropped are quite cheap. There's two seats and a small IRSU for refuelling on the surface. After the jets detach, the orbiter starts with 8177dV and 0.44 TWR, but it reaches a TWR of 1.26 as the tanks empty. Whiplash separation is cool and usually results in a nice explosion as they smack each other - I was watching a video while flying this and cut engines a bit late, hence the 135km PE. >6600dV in this wonky orbit and space for two (romantically inclined?) Kerbals who don't mind spending quite a few years together. Or who are just really really good at travel chess. So, you can probably reach Tylo with the thing, and probably land. Getting off again however... I emptied fuel tanks till it's TWR reached 1, at which point it's only got 1833 dV - not enough to complete orbit, especially with the losses its gonna have at that TWR. So, you might be able to land on TYlo then smash yourself into atoms at sub orbital velocity. If Tylo is possible at all (Without a fooking big rocket, or a large space plane carrying a tiny staged, disposable lander), i suspect some chemical fuel is needed. Maybe take out the centreline nuke for a chem engine and swap some tankage over to LFO. Then you are trading interplanetary delta V for more short term thrust.. the question is, can you make this chem engine last long enough to do any good, without swapping so much tankage over to Ox that your delta V goes into the toilet. Atm this design is good at bringing a fantastic portion of its original fuel reserves to tylo orbit, but it doesn't do much good as you plummet to the rocky surface. Another option is to dump the IRSU converter with a decoupler. It's only 1000 kredits, but weighs 1.25 tons. The biggest challenge looks to be taking off from Tylo surface with enough fuel to get back to Kerbin. You could leave some fuel in orbit before descent, but rendez-vous and docking are time consuming and require a lot of player skill. You could land on Pol home for a final top off before going home, but that's not an option if you ditched the converter. Maybe i could take advantage of the fact this thing has 5 RTGs (for the IRSU) and fit a ion engine, will save a bit on the transfer burns (admittedly, the lion's share of the burn is in the tylo descent and ascent, which must be at high TWR. That is why one does not simply walk into Tylo!) Use at own risk !
  4. RCS build aid is really invaluable, I suspect you are having a problem because your engines are too heavy and when there is no fuel aboard the weight of the cockpit alone is not enough. The mod shows a red dot which is where your dry CoM is, so you can get that right first then place the fuel equally either side of it. Also shows torque induced by thrust, so you can center the engine better with offset tool if needed. As Snark said, try using the lighter Terrier, it sill has plenty of power for an airplane, and try pushing the jet engines forward. Again, four or six Junos may be easier to place forward than a pair of heavy wheeleys.
  5. I haven't been playing so much KSP recently, and the cut n paste nightmare of sharing crafts and pics is something i've been putting off. But I finally got the craft flying. Sadly it's not quite as sexy in the metal as its shadow appears. Though it does look quite sleek when viewed from behind as you're flying it. First few flights revealed undesirable handling characteristics, CG was too far aft, making it capable of acrobatics but hard to control precisely. Also, the Panthers were slightly above CoM and RAPIERs a bit below it. On takeoff, it would fly ok, but as it accelerated, Panthers were first to get the RAM air boost and by 249 m/s it was flying at -5 AoA hands off. If you fought past this, then the RAPIERs would get going and start pitching you up again. Not good. You need an airplane that does prograde when you set it to prograde hold, or your drag will be high. Had to put both types of engines on separate stages then tweak with RCS build aid , then do the same for the NERVs. Each time i move one set of engines, it effects the CoM so the first group of engines need redoing. After several rounds of tweaking though, such forces become negligible. So I made an orbit shot. First thing, we have far too much oxidizer capacity. These adapters are the lowest drag way to taper down from a mk3 cargo bay, so i suppose i just live with it. Maybe you could have a chemical lander in the cargo bay and use these tanks to refuel it. For now i just adjusted them down to 1/4 capacity. Next 3 panther is too much for 2 rapier. Initial subsonic climb was conducted with a TWR of about 0.55, same as an F-105E fighter bomber : Levels off to go transonic at 6.6km, 3 min 40 sec after engine start. TWR is 1.0 (like an F-15) at this point, increasing to 1.15 (Eurofighter Typhoon, F-22 Raptor) with nukes on. It only needed 30 seconds to accelerate from 260 m/s to 440 m/s, that's hot ! After Panther flameout, we're down to the TWR of an F-105E again. At 22km speedrun, the thin air drops our TWR to just 0.3 (twin engine jetliner at max takeoff power), so it took a further 7 and a half minutes to reach 1350 m/s. With the nukes on , we're back up to F-105 TWR. At 1600 m/s , we're turning into a Boeing again, so it's time to hit close cycle mode - while the oxidizer lasts, our TWR is 1.7. The Space Shuttle only had a TWR of 1.5 on liftoff, so this must give quite a kck. Next iteration of the craft I replaced the tricoupler for a bicoupler on the back of the fuselage to drop us to two Panthers. Yes, the tricoupler has the best ratio of engine nodes to drag, but sometimes you got to look at the bigger picture. I wanted to try keeping the triple node and replacing its panthers with nukes. Then either 2 panthers/2 rapiers either side of fuselage or 2 panth/2 rapier/2 more nerv on side pods. The latter option meakes an even bigger mockery of our oxidizer capacity, it would probably have more delta v with none loaded at all. Also, having the heaviest, as opposed to the lightest engines at the back, means the side mount engines will need to go a lot further forward which may result in a less sleek looking craft. Finally, I loaded the cargo bay with an FT800/spark probe (like on the Argus demo video) and 4 additional tanks of jet fuel. This version went transonic at 5km, and needed 8 minutes to get to 360m/s. TWR during transonic was only 0.5, and that's with nukes on too. But it actually has a smoother ride than the triple panther , not pitching itself up into zoom climbs when the engines go banzai, and bear in mind this is worst case scenario - it's fully loaded here. Over 4k delta V in LKO, with the probe onboard, 5 seats. Looks like it pretty much does what Matt Lowne's craft did, so I'm naming it the Agenor, who was the 3rd ruler of the ancient City of Argos after Argus :-) Available here - Working on a 3 nuke version right now, might have more delta V due to lesser dry mass.
  6. AeroGav

    Some SSTO questions

    I've been playing Lord of the Rings online most of this year but came back to KSP because compared to learning a zillion boss fight dance moves, repeatable quest timers, and locations of all the vendor npcs, building airplanes in KSP is really accessible and something you can just drop in and out of at will. Also it has a pause button, KSP lets you pee. This is important. 3. For 30 tons, a lot of things work. One Whiplash two Nervs ? 2 Rapier 1 Nuke ? 1 Rapier 2 Nukes? All can do the job. My last endgame build was a 40 ton crew transport, 2 nukes, and one panther and one rapier clipped into each other to avoid asymmetry probs. That combo covers all speed regimes pretty well. Flight profile : I don't like thinking in terms of this pitch angle , that pitch angle. Pitch depends on your payload and TWR, the optimum changes throughout the flight. But the optimum AoA does not. For wings that is 5 degrees. For every other part it is zero (prograde). During the speedrun, you want to get as much velocity out of air breathing mode as possible. This means getting into level flight at about 21km, and holding that until acceleration starts to die away . You should be able to do 1400 - 1500 m/s, but engine thrust falls away rapidly thereafter. You are probably holding the nose down during the speedrun, to stop the plane climbing. Up to 21km thrust declines more slowly than air density (on the RAPIER) , which is why it's a good altitude for the speedrun, but after that it falls away more quickly than air density (drag). Once you've lit the nukes, it's time to forget about pandering to your jet engine's intake needs, the only thing that matters is lift to drag ratio - you maintain the AoA that gives best exchange rate possible. If the plane climbs, it climbs, if it then starts descending for a bit before heading back up again - let it. Just nail that AoA sweet spot to minimise drag loss. You can sort of see from this one, i'm holding the nose down a bit to maintain level air breathing flight at 21km till we reach 1500, then i start the nukes. At this point, i let the nose rise back to prograde again. The wings are angled up at 5 degrees so they are at 5 degrees making lift while the rest of the airplane is on prograde for low drag. I'm tweaking the deployed flap surface to keep the nose close to prograde. Now, when i stop pushing the nose down we end up with an excess of lift and immediately start climbing. In that video, I'm doing 1800 when i pass 30km, and am climbing at a three degree angle.
  7. AeroGav

    Matt Lowne's SSTO Emporium

    It's the gravity assists he pulls off that i could not possibly replicate. I did write a spaceplane tutorial last year. The Argus is an old design. Payload fraction / Delta V are what define SSTO "efficiency", the Argus has good Delta V (4300 from LKO) but it is mostly fuel, and doesn't carry many Kerbals for its size. Most of my ready made SSTOs are designed to carry lots of Kerbals to Minmus or Duna easily, but I think if you're going further afield it makes sense to do mining or have a refuelling stop on Minmus or Duna. 11 seats and 3000dv in orbit for 40 tons. I did make a version with 2 of the cabins swapped for fuel tanks SP.craft?dl=0 .. and an even more hopped up version for @septemberWaves and her rescaled solar system - the whiplash engines were jettisonable and it had >4k delta v in orbit with 0.6 to 1 TWR on its nukes in orbit. Why don't you spin this off to a challenge, to make a 2018 Argus replacement - state the requirements and let people submit their craft - presumably needs 4k delta v, at least 4 seats and a small cargo bay? As regard instructions , all my craft on KerbalX have them, and some have videos showing the launch process too. If you've not flown any of mine before, has detailed instructions and a video. It's quite forgiving too, but as a caveman tech design it hasn't got the performance you're after.
  8. AeroGav

    Landing Gear Weight limits.

    My latest ssto was one where i went for the lowest tech option for every part except the NERVS - so i used 5 small landing gears instead of 2 medium and 1 small. I must say. it is very stable on the ground as a result. One wheel up front, one pair just behind CoM a little way out from fuselage, and the rearmost anti tail strike pair on the tips of the delta wing at the back. Coming back from space empty, touchdown speed is 25 m/s and it is immune from cartwheeling. You can land just about anywhere.
  9. AeroGav

    Spaceplane handling

    Stability wise, you are doing most things right. However, the mod "CorrectCoL" shows that your airplane is trimmed to fly about 5 degrees nose down when "hands off" ie with no inputs from you or SAS. I presume you are trying to correct this by using SAS in its default "stability assist" mode. The problem is SAS is a terrible fly by wire system. It just tries to hold the nose at the same angle (relative to the sun) that is was at last time you touched the controls. So, over time it "learns" how much nose up input to apply to fight the plane's aerodynamic tendencies, but every time you touch the controls (such as to roll the wings) it resets so the nose falls quite some way. Fix the excessive nose down tendency and stop using Stability assist mode as a crutch, everything else falls into place. This is my "minimally changed" version - Lifter MINMOD.craft?dl=0 What I did was use the fine rotation tool to reduce the incidence of the rear wing. It makes a bit less lift, but the front wing is at a bigger angle of attack, and starts to stall first when the airplane is at a high AoA. As a result the plane flies 2 or 3 degrees nose up with SAS off and no-one at the controls, but if you yank the stick back hard you can't get it to pitch more than about 10 degrees. It's a space plane, not a fighter, no need to pitch that much even on landing. Most of the time you'll probably use Prograde Hold SAS mode in flight, which cuts the AoA down to about 1 degree nose up. I made a more heavily modded version too. Lifter2.craft?dl=0 The original has a lot of empty tanks that are just making drag. Even the above version is crazy overpowered. Full nose up until it's climbing 40-45 degrees on takeoff to stop speed getting stupid down low, then go prograde, it levels off about 18k by itself, gets over 1500 m/s air breathing. In rocket mode, TWR is over 1.15
  10. For your climb rate to increase, your lit from orbital freefall effect + lift from wings + thrust component from engines thrusting downward has to be > weight of craft So if you're already at 70% of orbital velocity, a TWR of 0.8 will be more than enough to overpower the craft's remaining weight. Here is an example of one of my spaceplanes using these effects - TWR (2 nukes running) 0.44 1577 m/s so about 75% of orbital velocity Lift - 115kn Drag - 35kn Thrust - 120kn Weight is shown as 246kn, but since we're approaching orbital speed over two thirds of that is getting cancelled by the centrifugal force of hurtling around the the planet. Our climb rate is 147 m/s and increasing..
  11. AeroGav

    SSTOs! Post your pictures here~

    While uploading my plane, I spotted this mad thing on KerbalX. It's 1Straycat's only upload. Look at how many passengers this thing carries - and how much delta V it's got (nearly 6k!) yet the body is entirely given over to cabins. I thought making something so large out of mk1 parts and a welter of strakes would be a floppy noodle nightmare, but it actually flies good and is more robust than you'd expect. Well, of course I made my own version, liquid fuel only (apart from a locked FT100 for the Vernors). Went down from three Rapier to two, but added two Panthers to give it a bit more low speed umph. Added an extra nuke, deleted the oxidizer tanks. Overall mass down by 10T. It only has 4800 delta V in orbit, though TWR better in nuke mode. Once the RAPIERs quit, TWR drops to 0.21 - but the lift/drag ratio in hypersonic flight is so good, it continues to gain energy - slowly. Oh yes, and about the durability. I wanted to fly it into some KSP buildings, but when you chop the throttle on this thing it just floats and floats and sailed over the top of the thing i was trying to crash into. Eventually on the third attempt, I managed to hit the VAB with it.... The cockpit is still there, and I'm counting the same number of cabins as it had before takeoff. Crumple zones FTW. The VAB was totalled, fortunately it's a weekend so no Kerbals were in it. My version here
  12. AeroGav

    SSTOs! Post your pictures here~ A thread came up asking for Panther spaceplanes. To be honest I don't think you can do very much on a pure Panther / Chemical design, other than reach LKO with a small payload fraction. Maybe by going very large, you can make something that does a worthwhile task in career mode, but i've not much experience in "moar boosters". However, I know a thing or two about optimising hypersonic lift / drag, so if you add NERVs onto the caveman airplane tech, you can actually make a nice little runabout. I'm really pleased with the appearance. With a full tech tree, it's Big S strakes are pretty much the only aero surface you want to use, their advantages are just too great. But with them off limits, I get to use the modular wing parts and was able to create some nicer shapes - though overall planform was dictated by the need to get dry CoM, wet CoM and lift into the right places.
  13. @Vegvisir Not wanting to reinvent the wheel, I took something based on your craft to produce the next step - a Panther/NERV SSTO. I kept the basic fuselage layout (small cargo bay, mk1 cockpit and crew cabin) , but added more wings since we need good lift/drag ratio in hypersonic flight if your propulsion is as weak and heavy as a nerv. I'm quite pleased at how it ended up looking, those mk2 parts are certainly pretty, and i don't normally go for modular wings (preferring fuel containing big S parts) but doing so gives much more control over how the craft looks. By the time I added incidence, control surfaces, and tweaked wing locations for correct centre of litt it has lost some of its sleekness, but still looks better than what i normally make. That's the upside to enforced low tech ! Fuel ends up in pods either side of the cargo bay, which means no CG shifts as the fuel burns off. That means an airplane that holds closer to prograde throughout the flight, which means less drag - as well as being nicer to fly. Two Panther and Two Nervs. I was going to make it completely LF only, but that means not using the oxidizer tankage of the mk2 adapters. On Prograde hold mode, she does 0.65 deg AoA on Prograde hold, with no input from me. If you take SAS off and let aerodynamics do their thing, the nose rises a little more - to 1.4 degrees Around 8 or 9 km, there isn't enough lit even at this angle to maintain our climb. The inboard elevons are bound to action group 1, and push the nose down a couple of degrees when selected, which puts us in a low drag mode for crossing the sound barrier. After crossing mach 1, lift increases dramatically too, and i'm using this action group intermittently to try keep us from bobbing over 14km when the jets start to loose power. After porpoising up and down a few times , we eventually hit 750 m/s in level flight at 15km. I start the rockets and cancel the nose down trim. The oxidizer runs out about 1500 m/s. Eventually, after some imid course corrections and over corrections, we end up here - Plenty enough fuel to land and go back to Kerbin, though you need a horizontal landing vernier system for a really stylish rolling touchdown on the flats. Could drive to several biomes this way, it doesn't use much fuel on the ground ! file here !
  14. Glad to see you're making progress. For incidence angle, I'd go for 5 degrees rather than 2 - 5 is the optimum angle of attack for lift at supersonic & hypersonic speed, so that's what we care about. Rather than fly the plane with SAS on Stability assist mode, you can then try flying with it set to Prograde Hold. This will significantly reduce drag. Note, you've added incidence to main wing and the canards, but not the strakes inbetween. The strakes will therefore stall last, and being in front of CoM, will keep making lift when everything else has quit, and send you nosing up into a deep stall. Remember kids, stuff in front of CoM should have same or slightly more incidence than stuff behind it . If this makes her adopt too much of a nose up attitude in "hands off" flight, move the wings back a bit ! What's your flight profile? Top speed on the Panther will be in level flight at about 14km up. You should be doing at least 750 before starting rocket, though after 750m/s power falls away very fast. If you can't keep your AoA down while doing that speed at that altitude, you deffo need more wing. Ideally you should have enough wing to do that altitude on prograde , with only the lift from wing incidence. Your screenshots are tiny but it looks like you were getting lift to drag ratio of about 1.6 to 1 in the middle picture. That's horrible ! My "Stretch Ray" was getting 4.2 to 1 at 19km and 830m/s. AoA is mostly to blame. Can you put those solar panels in the cargo bay? You're only going to need them once you're in space, keep em out of the wind till then. Attach them to a cylindrical thingy within the bay, maybe your science junior. Likewise, you could stick it on the side of the science junior within the bay. Engine Nacelle intakes - minor thing, but it doesn't need that much intake area if you already got two circular intakes. A single mk1 liquid fuel fuselage on the back of the main fuselage would hold just as much fuel for less drag. MK1 rocket fuel fuselage short - behind the cargo bay. Like i stressed in my space plane guide, don't use mk2 parts unless you really need their unique capabilities. An ft-400 tank holds the same amount of rocket fuel for about a third as much drag.
  15. Panther Terrier 30 part ship - 3 seats to LKO. On a technicality , this also counts as a "pre whiplash SSTO". Liquid fuel only panther/nerv thingy that can go a bit beyond LKO actually. Beyond the NERV motors, the rest of it is pretty much caveman. BTW, I like plenty of wing, especially when you have TWR < 0.5 in upper atmosphere thanks to NERV engines. Hypersonic motor glider, that is what you are building. 4 Star Euro NCAP Rating too, protect your most experienced Kerbals !
  16. Perfectly acceptable on my Ivy Bridge Desktop I5, though I've been watching the World Cup on my second monitor and the calculations make that stutter (thread priority?). Despite which I seem to do a better job spotting fouls than the V.A.R., but that's another topic. @linuxgurugamer very glad to see you're continuing the work, I thought it was a dead project because Google only brings up the old thread. You must have fallen out of favor with the Illuminati
  17. OFF-TOPIC but someone really needs to come up with a replacement for @Boris-Barboris 's CorrectCoL mod. Andromeda has the noob error of insufficient pitch stability, especially when empty I'm ashamed to say. For me, we need something that takes account of drag from non-wing parts, and was also a big fan of the static stability graph. You could see at what AoA the airplane has neither a pitch up or pitch down moment, by where the line crossed the X axis. I was aiming for a very small positive AoA, being the one it would fly at with no hand on the controls. You can see whether the plane's nose down tendency gets stronger as the node continues to rise, or if it reverses and goes flip happy because the front wing stalls first. I've had to manually correct Andromeda by making countless test flights 1. move engines forward a bit , move fuel tanks aft a bit so that hopefully CoM doesn't shift when fuel burns off (have as much fuel behind CoM as in front of it) 2. Now make flight after flight , shifting the wings around so it's stable with the new CoM position, then dialling in the right amount of built in angle on the surfaces so it holds a small positive aoa with no input 3. tweak trim flap deployment angles so you get about 5 degrees +- with SAS off and +- 1.5 degrees with it on I've now got it so the plane flies at +1 AoA with SAS off and trim neutral, with trim up action group, it's 5 degrees nose up with SAS off and 1.5 with it on, -5 with nose down set and -1 AOA with nose down set on prograde hold. Full back stick gives about 15 degree nose up. That took 2 hours, would have been 5 minutes without test flights if i still had correct CoL. That's just the testing with full tanks. To do empty, i need to manually empty all those strakes by the same amount, or leave the nervs running with parking brake set on the runway for 20 minutes. I've updated the craft file just now and might do it again if i get time for more ksp next week.
  18. Yes, that describes things :-) Kick ass mod, first time i've seen a flight envelope in KSP. Do try adding that orbital freefall thing though. You wrote this mainly to deal with the problem of getting supersonic , at such low speeds its not a factor and in any case, lift does not have to = weight when crossing mach 1, you can always go prograde for that bit of the flight even if it sends you arcing into a dive. During the speedrun, most of my planes, Andromeda included , have a bit too much wing, and especially when empty, trying to maintain 20km for the speedrun is like trying to hold a polystyrene block underwater. The graph doesn't really show this. Once you are done with airbreathing, i go prograde for best L/D ratio and the excess lift results in a positive rate of climb. It starts to run out of lift by 35km, but you're over 2000 m/s at that point which causes the climb rate to start increasing again.
  19. It is a liquid fuel only cargo ssto. First stage starts both panther and both rapier together. Second stage starts the nukes. The rapiers are only ever used in air breathing mode and the oxidizer tank at the front is empty. But it can still put a full orange tank in LKO :-) I suspect the drag values are far too high - is it getting confused about whether the cargo bay is open or shut , or does the wing incidence upset things?
  20. @Booots Awesome, the game really needs something like this. Sorry for not seeing the thread earlier but i haven't played KSP in a couple months. Anyway, I decided to see what it made of my last ship, Andromeda . In many ways, this is throwing your mod a curveball, it has two Rapiers and two Panthers, and the wings are angled up with 5 degrees incidence wrt to fuselage. Part count is quite high (look at all them strakes!) too. According to the flight envelope it cannot bridge the gap to supersonic flight, though i think you can see the two sweet spot islands of excess thrust thanks to the two engine types.. In fact, if you care to download the craft, it goes supersonic at 8km in level flight with 2x as much thrust as drag = and that's without using its nukes. Lift drag ratio also seems a little off. The actual value depends on how close to prograde you can keep, since the wings are angled. However, at mach 6 and 30km+, on nuke power, it holds only about 0.25 degrees above prograde when sas is set to prograde lock (when empty.. payload distribution can effect this). At that AoA, I was getting over 3.7 to 1 lift:drag ratio in hypersonic flight. Also, does the flight envelope take account orbital freefall ? At the sort of velocities people are going closed cycle, over half the weight is being cancelled out by this, which reduces the amount of lift needed. With a payload onboard, it doesn't hold prograde as accurately.. but still getting decent hypersonic L/D/
  21. AeroGav

    Need help with Lathe Space Plane

    I hadn't considered that. You could make the fuel depot itself have only one tank (lock any others and just click on the transfer OUT button, but i agree it'd be easier with less tanks on the shuttle)
  22. AeroGav

    How many Nukes?

    I build a lot of liquid fuel only SSTO space planes and they generally have 0.4 to 0.5 to 1 TWR in orbit, after the fuel used getting to orbit has burned off. A 2k DV burn to Duna or similar can take 8 minutes according to the maneuver node planner, so i start my burn 4 minutes early. As a result you do half of your burn before the maneuver node and half after it , so overall the burn happens "on time" more or less, and the craft takes the expected trajectory. Of course, if your burn times are long this can get in the way of making your burn close to PE to maximise Oberth effect. So it's generally better to do split burns - make a 900 m/s burn a few orbits before the ejection maneuver at PE, and do the rest of the burn at PE when the transfer window comes up - a much smaller burn is needed to put you on the interplanetary trajectory, since your AP is already on the verge of going out the system. For a single mk3 liquid fuel fuselage (long) I would use between four and six nukes,
  23. AeroGav

    Need help with Lathe Space Plane

    That airplane has a massive, heavy fuselage and relatively small wings, of course it will have a high landing speed, though as you've not shared the craft file i can't check if problems with centre of mass and control assignments are making the problem worse. That front wing only has a small elevon on it, so you're either not going to be able to pitch up much, or if you do achieve large pitch angles it will be from the much larger elevons on the rear wings, however these get the nose up by pushing the tail down, and actually subtract from total lift. One other thing, wings have a much . much better fuel capacity to drag ratio than fuselage tanks. They also provide lift. Whilst they have a bit more dry mass than cylindrical tanks of the same capacity, the lower drag means less engines, which means less weight overall. With generous wing area you can climb subsonic after takeoff into thinner air before levelling off to bust the sound barrier, which allows you to reduce the number of engines still more. Matt Lowne tends to make extreme delta V flights (unrefulled to Eeloo, Moho etc) with negligible payload. Most of the fuel is burnt out of the atmosphere, and he usually has just a single nerv pushing the 100 ton ship around in space. So his priorities are different. Have a look at my crew shuttle, the Griffon. Two NERVs, one rapier and one panther clipped together. No oxidizer required. Has 11 seats and makes orbit with over 3000dv when flown correctly. Has an inline clamp o tron and extra reaction wheels, but as it lacks RCS you're probably best off treating it as the passive partner in the docking maneuver and letting your orbital crew transfer vehicle/fuel bowser do the maneuvering. 42 m/s stall speed with full tanks on Laythe. Note that you can make large spaceplanes with good landing characteristics, but part counts get very high as you'll need to join lots of small wing parts together. Note 2 - I'd not taken this design to Laythe before and as expected, it would work better with a few small changes. Firstly, the trailing edge wing panels can bust off on landing if you pitch up any more than this. Maybe fit one of the small retactable landing gears at the back of the fuselage to prevent tail strikes, or a pair of them as outrigger wheels at the trailing edge near the wing tips. Second, there's not much sunlight out on Jool, so instead of solar panels in the service bay, fit an RTG (though in practice it has enough battery to handle re-entry , with the panels stowed and engines off, just fine. But its nice to have a bit of juice left to run the landing lights at the end of it)
  24. AeroGav

    ssto questions

    The most important thing is not to pitch the nose more than 5 degrees above prograde, because drag starts to get really bad when you do this If you're asking what altitude to go supersonic at, it depends. The two factors are 1. At altitude, there is less drag. 2. But, higher up, there is less lift and if you have to pitch the nose more than 5 degrees above prograde to get enough lift, then you need to stop climbing and go supersonic instead. So , a heavy plane with small wings might as well just fly level after takeoff and get supersonic first, before trying to climb, because if it tries to climb at low speed it will have to pitch the nose up excessively and that will create a lot of drag. Otoh something with more wing area relative to its weight will be able to avoid a bit of atmospheric drag by climbing a few km first, if you're patient. Whatever method you use, the main thing is that you reach hypersonic speeds (at least 1350 m/s) before switching to rocket mode. Very powerful airplanes might be able to bust that in a steep climb, others might not. For this reason I like to level off at 18-22km and fly level to make sure we hit our top speed. As @bewing says, making flight path changes at high speed like this can create major losses when using "all or nothing" keyboard control inputs. You need to make your corrections gentle, only moving the nose a few degrees away from Prograde. Probably the easiest way is just to set SAS to Prograde hold when you're halfway between your "supersonic" altitude and the 20km speedrun. For example, say you went supersonic at 6km altitude and started climbing steeply when the RAPIERs go nuts. 20km - 6km = 14km of climbing halfway point = 14km / 2 = 7km therefore at 6km + 7km = 13km, go to PRograde hold and the airplane should gradually start levelling off. In theory it will reach level flight somewhere near to 20km, as it levels off, go back to SAS attitude hold mode to stop this turning into a dive. My preference is RAPIERs and PANTHERs in a 1:1 ratio At mach 3.7, RAPIERS give 8x as much thrust as when static. Panthers have nice power at low speed and weigh half as much as a RAPIER. They loose power very abruptly after mach 2.5 but by that point the RAPIERS are boosting hard and it doesn't matter. Rule of thumb - One RAPIER, One Panther and Two NERVs will take a 50 ton spaceplane to orbit if it is very streamlined, has plenty of wing area, and is flown correctly. With mediocre aerodynamics, the same engine combo would only be good for a 25 ton airplane.
  25. Indeed, this mk3 cargo plane can put an orange tank in orbit with 2 rapiers and 2 panthers. It climbs to 5-7km (depending on weight) , then when the air is too thin for efficient subsonic flight, levels off to accelerate through the sound barrier. The Panthers cut out at mach 3, but by then the RAPIERs are really going some and bear in mind you can pretty much have two Panth for the weight of one RAPIER. In level flight at 20km it can still get 1400 airbreathing, after which I start up all 5 NERVs and off we go I reckon the combo of one Panther and one RAPIER can comfortably get 50-60 tons of well streamlined spaceplane up to hypersonic speed. Of course, that means either mounting them in pairs or clipping the panther onto the RAPIER to avoid thrust asymmetry problems. @dra321 Main thing - Don't use mk2 parts for fuel storage if you can help it. A mk1 LF tank holds the same fuel as a mk2 short LF tank, but has less than half the drag. However, wing parts are better still. The real champ is the Big S wing strake - 5 of them have the same dry mass and lift rating as a Big S delta Wing, but hold 500 fuel instead of 300. Now, wing parts do have more dry mass than LF tanks for a given capacity, but the difference is pretty tiny, and the lower drag means you need less engines , which weigh (literally) tons. So, build your wings and strakes out of fuel holding parts, and get rid of as many tanks as you can, especially the draggy mk2 sort. Also, you can construct tail fins out of strakes. Have a look at this one if you like Note that the cargo lifter i linked in the first pic uses no oxidizer, and keeps all its liquid fuel in strakes - the only fuselage tank is the adapter at the front, which you have to have. Minor thing - it looks like you're not doing rapier cones correctly. The rear attach node on the RAPIER is 1.25m in diameter, so you need to use a cone with a 1.25m attachment node. It looks like you're using 0.625m cones. Obviously , if you put a 1.25m cone on the back of the engine, that blocks the exhaust, but if you use the offset tool to move it forward, when the game checks the path of the engine's plume it will not see any obstructions. Sounds cheaty but all it does is reduce engine drag to be the same as an engine without a rear attach node, like a Whiplash.