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ok, here goes.

 

2. is the "reach mach 1, reach 10 km, reach orbit" or the "reach mach 3 at 150 meters or below, pitch up to 10 or 15 degrees, reach orbit" ascent profile better for heavy cargo ssto?

5. is 1 whiplash and the rest nuclear engines and rapiers better than just rapiers and nuclear engines

all help is appreciated :).

Edited by EndTraveler
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About the Item 2, it depends more of the engines you are using.

RAPIERs use a lot of fuel, but have excellent thrust at high speeds. So, if you use them, it's better to reach the maximum speed you manage to get without barbecuing your vessel at low altitude (where it's easier to get the oxidizer from the atmosphere), and then pull up - taking full advantage of the engine on ascension.

On item 3, the best way is to use Kerbal Engineer. It shows you that on the screen.

On item 4, it helps more in order to prevent the landing gear to be torn out due dynamic pressure or blown due temperature. I didn't noticed a serious drag on the stock gears - but, granted, I didn't tried enough.

Now, about the X-Wing design, it's a somewhat wild guess, but the W-Wing when extended would be nice for having tons of lift, as they used on the biplanes (besides a bit being "wasted" as the wing are twisted, and a fraction of the force vector is not used to lift up - but would help on turns). High speeds don't need so much lifting-surface, and surely don't like the extra drag. But since the X-Wing can folder the wings, halfing the surfaces and so , the drag, I think that the X-Wing could be a good design for a atmospheric vessel - if one manages to get gears and motors strong and light enough. :-)

Edited by Lisias
better phrasing
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26 minutes ago, Lisias said:

About the Item 2, it depends more of the engines you are using.

RAPIERs use a lot of fuel, but have excellent thrust at high speeds. So, if you use them, it's better to reach the maximum speed you manage to get without barbecuing your vessel at low altitude (where it's easier to get the oxidizer from the atmosphere), and then pull up - taking full advantage of the engine on ascension

Now, about the X-Wing design, it's a somewhat wild guess, but the W-Wing when extended would be nice for having tons of lift, as they used on the biplanes (besides a bit being "wasted" as the wing are twisted, and a fraction of the force vector is not used to lift up - but would help on turns). High speeds don't need so much lifting-surface, and surely don't like the extra drag. But since the X-Wing can folder the wings, halfing the surfaces and so , the drag, I think that the X-Wing could be a good design for a atmospheric vessel - if one manages to get gears and motors strong and light enough. :-)

I use mostly rapiers and 1 whiplash

 

also plz provide a w-wing example

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4 hours ago, EndTraveler said:

ok, here goes.

 

1. is an X-wing design good for reaching high speed?

Wings in general create lift and drag. If you are going to be flying level for a long time, then they support the weight of the plane while you do that. So if you are going to be doing an extended "speed run" to build up velocity at 20km altitude during your airbreathing phase, then wings can be good. Since they always create drag, they will always slow you down a bit. Since they create lift, they will save fuel while they create drag. So it's a tradeoff. The exact wing geometry makes almost no difference. Wings produce basically the same lift no matter how you place them.

If, on the other hand, you are going to be doing any "pitching up" stuff, then no -- you almost certainly want to be going for the absolute minimum wing surface possible.

4 hours ago, EndTraveler said:

2. is the "reach mach 1, reach 10 km, reach orbit" or the "reach mach 3 at 150 meters or below, pitch up to 10 or 15 degrees, reach orbit" ascent profile better for heavy cargo ssto?

Depends on your piloting skills, the types of parts you choose, and how carefully you work to minimize drag. Although you almost never want to reach mach 3 at sea level. You want to get past mach 1, and then get yourself into a climb as gently as possible. The harder you maneuver, the more of that initial speed you are going to waste doing your maneuver.

4 hours ago, EndTraveler said:

4. does tucking the landing gear "casing" help with aerodynamics and drag?

all help is appreciated :).

No. Landing gear is only shielded if the majority of it is inside a cargo or service bay (or sometimes a fairing) -- and you are willing to watch the extended wheels clip through the fuselage.

If you don't do that, then the drag on any radially attached part is always the same, no matter where you place it. Clipping parts together does not shield them from anything.

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I think the X wings design is too draggy. My SSTO design philopsopy is as little wing as possible. Just enough for taking it up to speed and a controllable glide back to landing. I also found that a medium size winglets and upward slanted canard will improve performance during reentry. Of course, there's this saying "Given enough engine power, even a brick can fly".

Edited by Fadly
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1 hour ago, bewing said:

Wings produce basically the same lift no matter how you place them.

Can you explain this a bit more?

I haven't started building anything serious with planes but that sounds important.

They dont create more drag/lift at all no matter how i place, angle or rotate them? Or you meant something else?

 

Edited by Boyster
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2 hours ago, Boyster said:

Can you explain this a bit more?

Lift and drag of a wing section are based entirely on the Angle of Attack to the airflow. There is no tip loss, Venturi or Coanda effects, or any other clever aerodynamic effect. If you build incidence into the wing when you attach it, that only changes the performance of the wing as it applies to changing the AoA. So basically what I'm saying is that there is no special clever wing arrangement that will work much better than any other wing arrangement. X or W or whatever.

 

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The X shape impacts the direction of the lift vectors, though, and as a result has higher induced drag for the same net lift. A flat bi-wing layout, like an equals sign (=) is more efficient if you need more lift than a single wing can give you (because of warping, floppy joints, fairing restrictions, ground obstacles, etc).

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I finally diagnosed that problem on my KSP Installment. So, let's go.
 

On 4/29/2018 at 6:37 PM, EndTraveler said:

also plz provide a w-wing example

There's no engine nor fuel on KSP that would allow us to build a X-Wing that would be at the same time trustworthy in shape and performance, so since there's no way to build a minimally decent and somewhat scaled X-Wing using pure Stock, I built this indecently. :-)

It's a X-Wing with the wings locked unfolded, in X. This configuration has LOTS of lifts and the 4 RAPIERs engines give it a very decent thrust - you can do orbital flights! So I had to put some RCS on it. But using monopropellant would be dumb, as the thing have some LiquidFuel/Oxidizer, so I choose Vernor that use it and it's more powerful (this is a fighter after all).

I cheated shamelessly: edited the craft and manually changed the MK1 Fuel Tanks from 400 Liquid Fuel to 180/220 LFO. =P

I did this stunt on the NCS Adapter too and on Engine PreCoolers (shamelessly using them as normal MK1 tanks). There's no other way of doing an minimally functional and near sized X-Wing using stock parts except by cheating in a way or another - some other vessels needs to activate the infinite fuel cheat, or a lot bigger when scaled with a Kerbal. =/

Since we would be flying without engines that generates electricity, instead of just adding batteries I hid a Fuel Cell Generator on the front Small Nose Cone. It's where the Vernor thrusters were put (and on wings too, obviously).

Another problem is the landing gears. It's not that bad, but the read wheels I put to avoid hitting the engines on the runway on take-off will blow up on reentry. Well, tt will work for now. :-)

There's a mk0 fuel tank emulating a R2 Astromech (and adding a bit more fuel).

The screenshots that follows were taken with the Aerodynamics Vectors being drawn - use Alt-F12 to do that on your machine. You will learn *A LOT* by analysing these vectors.

First, buttons configurations:

  • 1 : Turn on/off the upper engines
  • 2 : Idem for the lower engines
  • 3 : Close air intakes (important to avoid blowing up engines on reentry) and engage closed cycle mode.
  • 4: Turn on/off the Fuel Generator - remember todo it before taking off, or you can end without electricity.
  • B: There's Air Breaks on this thing, click on the Break Button on GUI and see.
  • G : "Landing Gears" (bleh :-) )
  • R : Turn On/Off RCS (do it in space to control your craft, as the wings are useless there)

This is pure Stock. No mods needed (just the cheats I cooked on the craft file). Taking off if tricky, due that crappy landing gears. Sorry. Landing this thing is almost impossible, good luck! :-D There's no VTOL on this thing. Turn SAS before engaging the engines, or you will be kicked out of the runway.

This is a screenshot of the Force Vectors for this vessel. Remember: blue for lifting, red for drag, yellow for control surfaces and cyan for the "extra" lift from hull and others surfaces. Observe how the blue lines as angled - this means that part of the lifting force is being "wasted" to the sides, instead of "pulling" the aircraft up. Also note that every wing has a nice =P red line, what means drag - that stole part of our thrust: the lesser red lines you get, more efficiently you fly.

WCnww-8QaCpAfPSBGqTGSRHRgAWhEOMiForucQDx SrKDnoOnjYhqiaAYwV6v1ozUTBshjM1QFcp2QYoQ

The vessel is extremely maneuverable and, so, unstable. Use SAS all the time and use ALT+WASD to adjust the trim. Besides cheating on the fuel tanks, I didn't had need any other cheats to get into a 100Km orbit, and then back (but I landed almost without fuel - RAPIERs burns an awful lot of fuel...).

I tried to upload the thing into KerbalX, but probably my hacking blew something there, as the site returned me a HTTP 500 while uploading. =D

So, here is the download file from google drive. And here some random screenshots (go to the end of the list).

In time, I have a "cheat-free" version of this craft with Whiplashes. Fly very nicely on atmosphere, and with some skilled piloting, you can kick it into low space for a small sub orbital flight. I'll try to upload this on Kerbal X and them update here.

EDIT: Here, the "cheat free" craft. Well, almost - there's some clipping on it but nothing compared to that stunt of mine on the last vessel. :-)

Edited by Lisias
cheat free link, small detail on instrucions
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On 4/29/2018 at 6:37 PM, EndTraveler said:

also plz provide a w-wing example

You are talking this one, right? (old school star-war fan - last time I saw a movie, Y-Wings were still being used! =P)

Do you have a good picture of this thing? Next a X-Wing, if possible - so I can infer the scale.

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29 minutes ago, EndTraveler said:

I meant that just the wing geometry, not the resemblance to the star wars craft

Understood... But I got on this, and wanna make a companion for that contraption of mine! :-)

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On 4/29/2018 at 9:03 PM, EndTraveler said:

ok, here goes.

 

2. is the "reach mach 1, reach 10 km, reach orbit" or the "reach mach 3 at 150 meters or below, pitch up to 10 or 15 degrees, reach orbit" ascent profile better for heavy cargo ssto?

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.

 

 

Quote


5. is 1 whiplash and the rest nuclear engines and rapiers better than just rapiers and nuclear engines

all help is appreciated :).

 

 

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.          

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