AeroGav

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  1. 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)
  2. 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,
  3. 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. https://kerbalx.com/AeroGav/MK1-Griffon-Deep-Space-Crew-Shuttle 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)
  4. 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.
  5. https://kerbalx.com/AeroGav/Andromeda 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 https://kerbalx.com/AeroGav/MK1-Griffon-Deep-Space-Crew-Shuttle. 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.
  6. AeroGav

    Inconsistent SSTO ascent

    This technique works ok with very high thrust aircraft and avoids having to make pitch corrections. In the stock game, without a good joystick or autopilot mod, or with an aircraft with poor handling characteristics, you are stuck with making "all or nothing" inputs that slam the control surfaces to max deflection or just leaving the nose locked on SAS . The above technique gets all the pitch adjustments done just after takeoff before speed has got high enough that you can loose a lot of velocity or cause structural breakup from it. But even within the stock aerodynamic model it's a gross oversimplification to call it "optimal". The problem with this technique is that if you climb too shallow, you will waste fuel fighting drag going too fast too low in the atmosphere. Of course, in jet mode you're still getting 4-10 times the ISP of rocket mode which lessens the impact, and fact if your SSTO doesn't have any nukes you want to use up all your excess jet fuel before switching to rocket mode or that leftover liquid fuel just becomes dead weight ! If you climb too steep you might never get supersonic, or climb out of the atmosphere and switch to close cycle mode prematurely before the air breathers have hit their top speed. For a version that's closer to "the truth" Keep your nose no more than 5 degrees above prograde. Drag increases very rapidly as angle of attack increases. Without autopilot mods, that probably means right clicking on the pitch control surfaces and lowering the authority slider for the flight to orbit, if you want to make small pitch adjustments that don't kick the nose far off prograde and cost velocity. Before landing, go right ahead and set them to full authority again so you can flare for touchdown properly. Whether you should skim just above the water after takeoff and go supersonic right on the deck or climb a bit first, depends on the design of your craft and how much wing it has. Climbing a bit, then levelling off to go supersonic in thinner air can work better if your craft can get enough lift to do that without the nose rising more than 5 degrees above prograde. If your plane is able to climb after takeoff without exceeding 240 m/s or letting the nose rise too far above prograde, let it! The thinner air will eventually rob it of lift and cause the flight path to level off, at this point, rather than fighting it by raising the nose further, let it level off or even fall slightly to penetrate the sound barrier. After 440 m/s, you are properly supersonic and can climb again, but it's best not to let her get too steep. If the nose goes much above 10 degrees above the horizon I set prograde hold on SAS to kill lift and minimise drag. Your aim is to level off about 20km for a speedrun to get as much velocity out of the air breathing engines as possible. I find it's a good idea to set prograde hold to begin the process of levelling off halfway between your supersonic acceleration altitude and your speedrun altitude. For example, it you went supersonic at 7km and want to speedrun at 21km, then set prograde hold at 14km to start levelling off at the latest. After engaging rocket engines, pitch the nose to 5 degrees above prograde and throttle back when AP goes over 70km. Unless your flying is absolutely perfect, it is normal to get slight porpoising or phugoids in the ascent profile (the sudden increase in thrust as you get supersonic is mostly to blame). Don't sweat these too much. They waste some time but only very little fuel, provided you don't make the mistake of making harsh corrections trying to straighten out your flight path or correct an overshoot - remember drag builds up severely when you get more than a few degrees off prograde, going way off prograde to make a harsh correction is counterproductive ! Zooming over 20km prematurely is also not a problem provided the RAPIERs aren't set to switch mode automatically - just let the plane come back down and the engines will relight. Piloting only really has two ways to hurt delta V By switching to rocket mode prematurely, before air breathing top speed has been reached By Climbing too steeply in rocket mode, causing cosine/gravity losses. You should be thrusting at (or close to the horizon) with a a climb angle less than 5 degrees. Let the wings do lift and engines do thrust. The OP got done over by the 1.4.1 fairing drag which no amount of piloting can overcome. Stock methods of "fine pitch control" Option One - Use Pitch Trim. https://kerbalx.com/AeroGav/Voodoo-Ray Craft file here with instructions. This video has annotations (turn on subtitles) that explains how to fly this to orbit using pitch trim and no SAS of any kind below the Karman line. If you're efficient , you can take this little plane surprisingly far. Method Two - Trim flaps bound to action groups Basically, fly the plane with SAS set to Prograde hold but have trim flaps bound to action groups that give you an amount of nose up trim that's good for an efficient climb as well as for the speedrun/supersonic acceleration. Example craft file here , with instructions https://kerbalx.com/AeroGav/MK1-Griffon-Deep-Space-Crew-Shuttle Note , this plane also has wings angled up as they attach to fuselage. So even when airplane itself is on prograde, the wings are still angled at 5 degrees to the airflow, making lift. You can use trim flaps to raise or lower the nose a couple degrees though when on prograde hold
  7. @herbal space program As well as not getting a Rapier engine snagged after jettison, I have another way to improve the design. I've been torn by the need to save weight and lower drag. The problem is there are no mk3 decouplers , so if you use some kind of mk3 to 2.5m adapter on both ends of the mk3 tank, you can only jettison the bits forward and aft of these adapters. Thus , a majority of the streamlining part mass is carried all the way to and from Tylo. But, if you offset the 2.5m nose cone so it's partially inside the mk3 to 2.5m adapter, after firing the decoupler, the 2.5m cone and mk3 adapter will be occupying the same space and this should trigger an explosion that destroys both. Ship is likely to flip out severely, but out of the atmosphere there should be plenty of time to bring that under control. Also, my design had 6 nukes. Dropping to the optimal 5 will give better delta V as well (after punching off 3 engines i gained 2k delta v in orbit)
  8. AeroGav

    SpacePlane Reentry?

    This is the airplane and here is an exploded view of the mk1 fuselages attached either side of the main body On stock settings, unless you're re-entering at 5000 m/s from a Jool trajectory, only the Kerballed bits are at risk and the cockpit in particular. Clipping stuff inside the structural fuselages does not hide them from drag or heat, the game still sees them as radially attached stuff on the outside of the ship, regardless of how you offset. And that stuff will make huge drag btw. Just swap to an inline cockpit and if that's not enough, increase wing area so you can make more lift and drag on re-entry. Lift keeps you out of the thickest atmo till you've slowed up a good amount, and drag obviously reduces your speed and therefore heat too.
  9. AeroGav

    Planes for alien skies

    Helecopters can never manage a particularly high forward speed - possibly you are encountering "retreating blade stall" which is why it loses control. That said, if you can get up to 30-40km the ISP of stock engines dramatically improves. I built a NERV spaceplane that could make the ascent from these altitudes to orbit if hypereditied there. However, nuclear turbojets make it all much easier.
  10. AeroGav

    SpacePlane Reentry?

    I'd be interested to see what your design looks like @Lego_Prodigy I never use the pointy cockpits (like the one in your avatar pic) because the part at the front gets most of the heat and the cockpit is the most sensitive to heating. In 1.3 heating effects made pointy cockpits more or less useless for Spaceplanes, in 1.4 heating levels have been reduced but still the first thing i'd try is to swap to the mk2 inline cockpit with a mk2 to mk1 adapter in front then a nose cone or intake on the front of that. In fact you could even put a mk2 clamp o tron ahead of the cockpit. For re-entry profile, I usually come in pitched up moderately with the nose 10 degrees above prograde. That way you're not completely stalled and are still making lift, which keeps you in the thin air longer. You also have more control that way and can fine tune your arrival point by pitching up for more drag (if overshooting) or lowering pitch to 5 degrees for best glide ratio (if coming up short). This all works better when you have a lot of wing. I normally retro burn until my PE goes to ground level somewhere in the desert continent west of KSP, my planes have good / lift drag ratios and when they encounter significant atmosphere the impact point inevitably starts moving downrange. BTW, are you dumping your payload after launch and immediately re-entering, or are you orbiting in orbit a little while first? It is harder to re-enter if the cockpit is still heat soaked from the launch process. This video demonstrates the landing point aim process mostly - but you can see how even a mk1 design has no problems with heat when using inline cockpit. Make sure you have subtitles / captions enabled for the text (think that only works on a pc tho)
  11. AeroGav

    Planes for alien skies

    Interstellar is a huge mod that takes a lot of supporting, and i think it has balance issues. But if you want to go to Eve, it has something you absolutely need for this - dual mode nuclear thermal engines that can function as nuclear turbojets (running off eve's atmosphere below mach 3.5) and then operating as a traditional nerv in close cycle mode. Use a 2.5m pebble bed reactor and hydrazine or ammonia fuel for best results ! Stock, I have various spaceplanes able to land on Duna. Pure aerodynamic lift like a Fieseler Storch - https://kerbalx.com/AeroGav/stol I have not actually flown this to Duna but I'd be amazed if it couldn't land there. As for getting there, it took off from the rooftop and got to orbit with enough Delta V to reach Duna, if not come back without some refuelling Here is a 5 seater IRSU plane that could straight shot Duna in 1.3. I haven't tried it in 1.4 since fairing drag is bugged, it might not go so well.... This one uses Vernier lift engines to reduce landing speed on Duna, as you can see from the first part of this video, you can also land on Minmus flats with them. https://kerbalx.com/AeroGav/Starsailor
  12. AeroGav

    kerbal SSTO program!

    I've played career games this way, but with standard difficulty it is harder to get tech than to get funds, and what funds are required are mostly spent on upgrading facilities than on vehicles. For any given mission, it requires a larger (more facilities) or higher tech vehicle to accomplish with re-use rather than 100% disposability. Plus, landing all those re-usable craft eventually becomes a chore in itself. Suggest you create a custom difficulty game and Lower Funds Rewards to 30%, as well as Funds penalties to 30%, then give yourself just enough starting tech to unlock aviation. Lowering Funds Penalties reduces cost of building upgrades , so they are no longer the major expense , and cuts down the grind. However lowering Funds Rewards means you get less money per contract and have to shoot for 100% re-use on most flights if your space program is to be profitable. As for the airplanes I use : Juno / Terrier https://kerbalx.com/AeroGav/Juno-basic-ssto 4 junos and a terrier, just gets to orbit with tight margins. Panther / Terrier Still rubbish payload fraction, but a lot less sweaty. Simple 30 part low orbit tourist ship https://kerbalx.com/AeroGav/Basic-Tourist-SSTO Something that can actually tow station components to orbit behind itself (no cargo bay) https://kerbalx.com/AeroGav/Aero-Tug-1 Panther and Poodle, self launching science lab - https://kerbalx.com/AeroGav/lowtec-flylab2 Panther / N.E.R.V Now you're in business. Worthwhile performance possible. Here's the basic Voodoo Ray https://kerbalx.com/AeroGav/Voodoo-Ray possibly able to put flags on Minmus, it will certainly do Munar flybys with ease. It is very stable aerodynamically and can be flown by non-pilot Kerbals. Here's a stretch version of the above, with larger wings and fuel tanks. A bit slower getting to orbit but enough fuel to get you to the Mun surface and back. https://kerbalx.com/AeroGav/Stretch-Ray I To reduce drag and to make the lower TWR easier to manage, the wings and control surfaces are angled such that you just use Prograde Hold in Surface mode for the flight to orbit, minor adjustments to climb rate can be accomplished by action groups 1-3 which deploy nose/up down trim flaps. Whilst none of the parts are higher tech than the basic Ray, it requires a trained pilot for the Prograde hold mode and that your Hangar supports custom action groups. The longer wingspan may not be launchable on the basic runway either. The final Panther/NERV jet is this dinky little mk2 with a small cargo bay. Can deploy small satellites but with an auxilliary fuel tank, could also get you to the surface of Minmus pretty easy (then drive it as a rocket rover over multiple biomes to max your tech tree) https://kerbalx.com/AeroGav/Firefox-I Whiplash / DART / N.E.R.V The NERV is a 500 tech point part, and overall i can do more with a Panther/ nerv than i can with a Whiplash/Terrier. But If you have both 500 tech nodes, you can make something nice like this - https://kerbalx.com/AeroGav/X949-Xanadu-B
  13. There's quite a bit more info to be found on academic papers on the internet than is currently to be found on Reaction Engine's website. The problem is, a lot of it goes over my head To keep things simple, the SABRE engine is like a jet engine, except it uses the supercold hydrogen fuel to chill the incoming air before feeding it to the compressor. This keeps the compressor light and compact and allows it to work to higher mach numbers than conventional jet engines. The combustion chamber and nozzle look a lot more like that of a rocket engine than a jet, but ultimately have the same function. This engine can run a little over mach 5, a significant improvement over the pratt and whitney j-58's "a little bit" over mach 3. What's the limiting factor? Is intake drag reducing net thrust to the point it'd be more efficient to go "closed cycle"? Or is it the old enemy, heat? In conventional jets, the incoming air stream gets compressed in the intake as it gets accelerated to the speed of the aircraft. This happens before it meets the turbine's compressor stage, and since gases get hotter when compressed, there is a temperature limit. You can make the compressor out of the same heat resistant materials as the turbine, but that adds a lot of weight (over aluminium alloys that would otherwise be used). Also , since the air is hotter before fuel gets burned, it will be hotter still after combustion, and you could then run into turbine limits , which are already using the most heat resistant materials available. The only options then are to reduce fuel added in the main combustor and burn more in the afterburner, or lower the engine compression ratio, both of which hurt performance and fuel consumption. An SSTO engine needs high TWR or it's going to add too much dry mass to the orbiter. Would it be correct to say that in the intake, as the air is sped up to the speed of the airplane, kinetic energy is being converted to compression and heat gain in the air. Theoretically, that energy gets returned back to kinetic as the gas flow expands through the turbine stages and back out the nozzle. But in practice there will be losses, which set the limits for air breathing propulsion of any kind. Apparently, at mach 8, the kinetic energy of the intake air is equal to the chemical energy that can be released by burning fuel in it to use up all the available oxygen of that intake air charge. So unless your ram compression/expansion is perfectly efficient, you can see how hard it is even for scramjets to make max thrust. Speaking of Ramjets, the SABRE has "bypass ramjets" surrounding the four combustors/bell nozzles. Apparently, more liquid hydrogen is used needed to cool the incoming air , than the main engine can use. So the excess hydrogen is burned in the bypass ducts. They are sometimes known as "bypass ramjets" but apparently the goal was "negative drag" not thrust. Even so, do they provide more power at higher speeds? I'd be interested to know how the power characteristics of the proposed engine would look. Certainly the Kerbal RAPIER has a mad 8x thrust multiplier at high speed. The only info i could find on the SABRE, stated that the core mass flow rate was pretty constant over the Skylon's flight profile, varying only by a factor of 1.6 or so. However it's possible these bypass ducts change the overall picture. Even so, it cannot possibly replicate the crazy power rush of the RAPIER, since apparently the Skylon would need 2 hours to compete the air breathing phase of flight, reaching mach 5.2 or so at 22km. One other little fact slipped out during a discussion about nozzle design - apparently combustion chamber pressure doubles when switching to close cycle. I don't know enough about rocket engines, but i suspect power increases at least that much - sounds like a real kick in the pants...
  14. AeroGav

    Fuels in KSP

    The Russians converted an airliner to run an engine off one, search for "cryoplane". Jet engines can run off any combustible fluid, I've seen some youtube videos from a Canadian guy who refurbishes old jets for use as ground power plants, if you want to run off Natural Gas, Gasoline, Kerosene, Diesel or even waste vegetable oil (how good would that smell) you just change the fuel injector nozzles to account for the viscosity of what you're injecting and that the engine gets the right amount of fuel. Certainly less involved than converting in internal combustion engine to run off a different fuel - lower octane ratio, would have to put a spacer between engine block and cylinder head to lower compression ratio, something with higher boiling point than gasoline? would need to worry about your carburettor failing to vapourize the fuel etc. Biggest problem with liquid fuel being hydrogen, is that you'd never get a worthwhile amount in big s wings and strakes like you can in game. Also with that huge surface area to volume ratio, boil off rates would be insane. also , ice forming on wings of aircraft is generally considered a bad thing, so filling the wings with cryo propellant probably not smart,
  15. AeroGav

    Fuels in KSP

    Most of the cost issue is down to people using NTR for deep space probes. Obviously if you're not recovering the part, the price hurts. That said, since the NTR will be on the upper stage, it really should be possible to recover the entire upper stage at the end of the mission , though the re-entry aerodynamics and parachute landing attitude will need careful design. I only really use them on space planes and shuttles, so the recovery of the engine is a given (and necessary delta v would be hard to achieve otherwise). Though some of these nuclear spaceplanes aren't SSTOs, discarding jet engines or riding up to 20km on SRBs
  16. AeroGav

    Fuels in KSP

    But Methane leads to soot deposits within the reactor doesn't it, which precludes us from using the engines the way we do in KSP (over and over with no maintenance, for decades on end, in an IRSU grand tour) The values given for Ammonia and Hydrazine as NTR fuels vary a lot depending on what source you're quoting and on the reactor temperature (degree of dissociation). Remember though, we're not comparing their values with Hydrolox, an Ammonia/Hydrazine NTR is competing against storable chemical propellants, that give between 310 sec (Space Shuttle OMS) and 375 (SpaceX Raptor, as yet unbuilt, if you treat mild cryo Methalox as "storables")
  17. AeroGav

    Buff Rapier vacuum Isp

    You can see why the RAPIER is such a good jet engine even if you're not using close cycle mode. The thrust multiplier remains above 3 till mach 5.5, given that orbital velocity (at stock scale) is about mach 7, you only need 1.5 mach's worth of rocket delta V. The Whiplash may have 20% better fuel consumption in the air breathing phase, but it drops to a multiplier of 3 by mach 4.5, which means you need 2.5 machs worth of rocket delta V. Even if you are using LV-Ns, rocket mode fuel consumption is 4x that in air breathing, so you can see why the Rapier's higher top speed always wins. Well, there are other fuels that an NTR can run off than LH2. For example, Ammonia (which can also be used in jet engines). Liquid ammonia is a storable propellant. It won't give you anything like the ISP of NTR / LH2 (though it does partially dissociate to hydrogen in the heat of the reactor) , but it's still heaps better than storable chemical propellants. The main thing is that large LH2 tanks mean drag, which is worse on a space plane than a rocket. BTW, in this game rocket engines correctly attached give very little drag, even if you don't clip nose cones into their rear attach nodes. The vast majority of the drag is coming from the fuselage, ie. the LFO tanks of your thirsty closed cycle RAPIERS. Sounds like the best compromise would be to give it the Vacuum / Atm closed cycle ISP values of the Dart aerospike, and to reduce this flow multiplier to 1.5. People will have to use a proper flight profile. You can still hit the same airbreathing top speed, but you'll need to do that in level flight at high altitude, not while passing through 8km in a steep climb. Flights to orbit will take a minute or so longer, but if you don't like flying, why are you building space planes. I'll have to redesign my craft to incorporate more RAPIERs, but will probably start using Oxidizer again and fit fewer NERVs/Panthers.
  18. AeroGav

    Buff Rapier vacuum Isp

    You are correct in that the SABRE, unlike the RAPIER, has a plug type nozzle that gives decent performance across a wide range of air pressures, purportedly not far below the state of the art in terms of vacuum isp. The problem is you are going to hard time attracting support from the community because it is already seen as one of the most OP engines in the game. You'd really have to package this up with a set of nerfs to address the following : The Rapier should require liquid hydrogen. LH2 has more heat absorption per KG than even water, no other fuel comes close in this regard. This means to have a RAPIER you have to deal with boil off and more importantly, very bulky (draggy) fuel tanks. Without LH2, the use of fuel to pre-cool the intake air - the thing that differentiates it from a Whiplash - is not viable. The Rapier gets this crazy ramjet boost to max thrust at high speed, peaking at over 8 times the static thrust rating at mach 3.7. This is not a feature of the real SABRE and seem to ignore flow limits of the intake/precooler/compressor systems, rpm limits of the turbines and max chamber pressures. This banzai surge from mach 1.5 - 4 makes possible the blatantly unrealistic flight profile of flying level after takeoff and accelerating to mach 4/5 at sea level, before pitching up and holding a constant pitch angle till clear of the atmosphere. The fact that thrust goes to near infinite levels, allows the massive drag to be overcome. In reality no aircraft has gone more than a hair over mach 1 at sea level. Any airframe that generates enough lift to get airborne before the tyres explode will be too draggy to push high speeds at sea level. At altitude, it's a different story. Same with the SABRE engine - the ram air effect of increasing speed compensates for the thinning air at altitude, but will not allow it to greatly exceed its sea level thrust due to choke limits. The pre-cooling deals with adiabatic heating, up to a point. Doing both of those would require major changes, but they should perhaps give the RAPIER a much flatter thrust curve in its config files, to at least acknowledge the above, if they're going to buff the vacuum ISP like you suggest. That will still break a load of legacy craft files, but then that's something with come to expect with version updates ! My preferred propulsion is now one Rapier , one Panther and two NERVs per 40 tons of craft weight. I don't use the close cycle mode at all. Can only see it making sense in edge cases like what Matt Lowne does with RAPIER SSTO lifting an ION system into orbit. I can get better payload fraction going liquid fuel only (mass of the nervs more than offset by absence of massive LFO tanks) but RAPIER only gives lowest dry mass, which enables the Xenon drive payload to get more delta V.
  19. AeroGav

    Fuels in KSP

    Monopropellant Hydrazine fits the bill, unless anyone can think of a reason to look further Liquid Fuel It's far too dense to be Hydrogen It doesn't give nearly enough ISP to be Hydrogen (450 top end chemical, over 1000 NTR) It can be stored indefinitely It does not cause soot clogging of NTRs with prolonged use (so not Methane or Kerosene) It can be used in jet engines Not particularly explosive. No sustained ground fire when the container is destroyed My theory is that it's Liquid Ammonia. This stuff can burn in air in air breathing engines (though it only has half the calorific value of kerosene) and it can be reacted with storable oxidizer in a chemical rocket. In an NTR, some of it dissociates to hydrogen, giving moderately high ISP. In a crash, you really don't want be breathing the vapours of this stuff, but then the same goes for Hydrazine. It probably helps our little green friends wear space suits, but then again they seem to be made of strong stuff all round. Oxidizer Storable Nitrogen Tetroxide?
  20. AeroGav

    Made a table for wing effectiveness [WIP]

    Max deflection does not come free. The higher the angle of attack of the control surface, the more drag it produces. Eg. Airplane is at 3 degrees angle of attack Wing is mounted to fuselage with 5 degrees of incidence Aileron on wing deflects 10 degrees That aileron is now at 3 + 5 + 10 = 18 degrees At small angles, you get mostly lift, but after a point lift starts to max out but drag goes up exponentially. This is especially important with regard to ailerons because the drag at the wingtip torques the nose away from the direction you're trying to turn in (adverse yaw/sideslip). Of course, you can take a surface with a low max deflection angle and crank its "authority limiter" slider up to 150% if you want to turn it into a highly deflecting one, or take a highly deflecting surface and turn the authority right down. I love Big S wing strakes, i try to keep all my fuel there if i can. Orange tank to orbit on a really dinky liquid fuel lifter - ...and yes, if your computer can bear the part count, don't use real tail fins, mount big S strakes vertically like in the above example then put elevons on the end for the active part of rudder functions. Here's another convert to the Way of the Big S Strake p
  21. AeroGav

    How do you get a bunch of kerbals around?

    This is overall the best spaceplane i've built so far, tested in 1.4.2. https://kerbalx.com/AeroGav/MK1-Griffon-Deep-Space-Crew-Shuttle 11 Seats and 3000dv in low kerbin orbit. Has an inline clamp o tron and twin reaction wheels, but it wouldn't be particularly easy to dock to a station. Since i'm bad at docking, i'd probably put some kind of tender in orbit next to the station, some non aerodynamic thing with docking ports and 4 way rcs blocks to move the crew the last 100m from the station to the airplane. You could try to improve the docking maneuverability of the airplane but RCS ports add a lot of drag - if you must do this use one Vernier or linear RCS port for each axis, mounted on the CG, not the draggy and melty 4-ways. Even then , the inline clamp o tron makes it better as a thing to be docked to , rather than a thing doing the docking. Yes, people put shielded clamp o trons on the front of spaceplanes but that adds even more drag. You can overcome that drag with the raw power of a chemical fuelled ship where every engine is a rapier, but then running out of fuel becomes the issue. SSTO rockets are a few minutes quicker to orbit than a space plane, but it ultimately turns into a race against your fuel gauge the margins are so thin.
  22. I built this Andromeda class SSTO the other week, the intended use being space station components, which are bulky but light. I tested it with a 2.5m Xenon powered ship as the heaviest plausible payload (18t), because if your lifter is NERV powered, why would you go back down to chemical ISP for the deep space part? But the gold standard for a mk3 SSTO is an orange tank (36T) , so it had to be done... A design like this lives or dies by it's lift/drag ratio, namely you must stay as close to prograde as possible to minimise drag from the cargo bay. Aerodynamically, it's designed to do that when empty, and i've added trim flaps on action groups 1-3 to nudge the angle of attack a few degrees higher or lower so you can adjust the flight path. However, the positioning of the cargo can upset this. The orange tank caused it's AoA in Neutral trim to shift to almost 2 degrees nose down , due to the cargo being slightly too far forward. I was able to work around this by operating with nose up trim most of the flight and tweaking the deployment angle of the trim flap, as i'm sure you could if you had the luxury of an analog stick ! In future though, i'd recommend test flying with the payload before shooting for orbit, and see where the natural AoA goes to so you can see if the cargo needs to move at all. Or just get a fancy-ass analog joystick ! https://kerbalx.com/AeroGav/Andromeda Is it the smallest thing to ever lift an orange tank?
  23. AeroGav

    Landing Gear Weight limits.

    I seldom economise weight on my space planes, with the NERVs I like to carry, a few kg for the landing gear seems moot, though i focus hard on drag. The limiting factor for me is elimination of tail strikes. Even the big S wing part has quite a short span - in order to get enough area, I find myself mounting two back to back in a double diamond or attaching strakes. The wing root therefore runs most of the length of the fuselage. When you add 5 degrees of incidence, this means the trailing edge is often the lowest point of the aircraft and it's right at the back of the plane too, raising the tailstrike risk. You can't shift the whole wing upward because fuel is stored there and that results in centre of thrust issues/CoM shifting as the fuel burns off. So, even my smaller designs tend to use medium main landing gear legs. 40 tons gross weight on that thing - probably doesn't NEED mediums https://kerbalx.com/AeroGav/MK1-Griffon-Deep-Space-Crew-Shuttle
  24. AeroGav

    Cost effective LKO cargo vehicle?

    You said in your original post that you didn't have mk3 cargo bays unlocked. Fairings are bugged in 1.4.2 so can't be trusted. Also, it sounds like you are experienced in building rockets but have little or no expertise with aircraft. In KSP, it is far easier to access funds than endgame techs, so taking all these things together you're probably best off just sticking with throwaway vehicles, just concentrate on making them cost effective. There is no reason you can't recover the upper stage actually , but there is no easy way to pull off a SpaceX in stock KSP so use Kickback SRBs for the lower . They give the most thrust per unit of cost. Rocket SSTOs have awful payload fractions, even lower than spaceplane ones. You'd need something monstrous to launch what you need. Space shuttles are a nightmare to build in KSP. Harder than SSTOs and they perform worse by just about every metric. We only build them for the challenge and for "rule of cool". I can't give much advice on rocketry beyond "use cheap SRB lower and recover the upper". For airplane type systems, I wrote a long tutorial thread The main reason people go wrong building space planes is that the game shows mass of parts in the craft editor, but no drag info. It offers no clues that leaving open attach nodes is bad, and that parts end attached must be joined by attachment nodes of matching diameters - if not use an adapter. Aerodynamic (according to KSP) - 2 rapiers and 2 panthers get it to mach 4.7. 5 nervs do the rest. https://kerbalx.com/AeroGav/Andromeda If you want to try spaceplanes but don't feel ready for SSTO, instead of trying to build a space shuttle, I'd recommend making a spaceplane with droppable booster engines. Whiplash/Panther motors are quite cheap, if you hang them off the wingtips near the CG, jettisoning them will not upset the aircraft. https://kerbalx.com/AeroGav/Learstar-A2
  25. AeroGav

    Fairing broken?

    Are you aware the 2.5m fairing is currently generating huge amounts of drag? It shows 0 drag itself, but the part it is mounted on gets an extra 400kn Note , the front mk3 mount has Dart aerospike engines mounted on the small nodes, which are rotated 180 degrees to thrust downwards and offset outward to clear the fuselage. This is the same in both pics. The first pic has a mk2 command pod on the big node, and the second pic has a 2.5m fairing instead.