[WIP] R.E.L Skylon C2. Alpha Released. FAR config broken. (08 Dec 2014)

[CaptainKipard]

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[td]Reaction Engines Limited Skylon C2

Announcements

I'm currently waiting for KSP 1.0 so I can develop this further for the new aerodynamics model. resting my tired brain.

An alpha version for stock aerodynamics is now released

Download Skylon Alpha for Stock Aerodynamics

Released under the Attribution-NonCommercial-ShareAlike 4.0 International license

Extract KipEng to GameData. If you have any of my other mods windows will ask you to merge the KipEng folder.

Dependencies:

• Firespitter (plugin only)
  
• Community Resource Pack
  
• Kerbal Joint Reinforcement (Might not be necessary. If anyone wants to risk it let me know how it goes)
  

If you don't want the parts from Firespitter, you can delete all the files from that folder but keep the plugin directory structure the same just in case.

Recommended

• LoadOnDemand
  OR
  
• Active Texture Management.
  Not both.
  

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It flies well and can be used effectively, but is far from finished.

Showcase video by White Owl. Thanks!

White Owl's Module Manager file for the tweaks he made to various parts as mentioned in the video

Download

Usage:

Skylon Control Core 2 has an animation that allows you to change the "Control from here" vector between the Sabre engine thrust vector, and the orbital engine thrust vector. This will change where the navball is pointing to be in line with the corresponding engines. The Sabre vector is selected by default.

Skylon Control Core 1 is a regular part. Selecting "Control from here" on this part will let you control the craft easier with the RCS thrusters and reaction wheel since they are aligned with that part.

The included craft file has all the parts and action groups set up as follows:

• The control surfaces are set to use specific user input
  
• Main landing gear has the brakes on by default
  
• Sabre engines are set to Manual Switching.
  
• AG 1 set to change Sabre engine mode
  
• AG 2 set to toggle Sabre engines
  
• AG 3 set to toggle the Skylon Orbital Maneuvering Assembly
  

In order to perform a successful launch with the Skylon you need to do the following.

1. Load the included craft file and launch
   
2. Right-click on the Skylon Control Core 2 and click "Control from here".
   
3. SAS on, Breaks off.
   
4. Stage.
   
5. Towards the end of the runway pitch up as far as you can without destroying the tail.
   
6. As soon as you leave the runway, pitch up more to start gaining altitude and retract the landing gear to decrease drag.
   
7. Fly in air-breathing mode to about 20km and accelerate to about 900-1000m/s. Watch your IntakeAir.
   
8. Switch to rocket mode, and continue as you would with a rocket. The craft has enough resources to achieve an orbit of ~300km with a heavy payload.
   
9. If you want to use the SOMA engine you must change the vector on the Skylon Control Core 2.
   
10. If you have a dockable payload in the payload bay and you want to dock using RCS, you need to click "Control from here" on Skylon Control Core 1.
    
11. Remember to switch back to the correct core and vector before returning to Kerbin.
    

Current progress

• Modelling - 95%
  
• Colliders - 95%
  
• Unwrapping - 0%
  
• Rigging - 50%
  
• Animations - 70%
  
• Texturing - 50%
  
• Unity Import - 10%
  
• Config - 80%
  

To-do list (subject to change)

• Remodel control surfaces
  
• Unwrap everything again
  
• Re-do RCS placement
  
• Tweak the steering curve
  
• Configure the parts for FAR and DRE, and release MM configs
  
• Finish adding colliders
  
• Fix Main gear animation
  
• Configure intake animations
  
• Add solar panels to the cargo bay doors.
  
• Fix cargo bay mechanism and animation.
  
• Finish the texture
  
• Look into changing over to DDS format for textures
  
• Configure techtree placement
  
• Consider ModuleMirror for wings, canards and main gear
  
• Better engine FX
  
• Consider using LFO for the RCS.
  
• Create the Skylon Personnel and Logistics Module as the first addon for this mod
  

Current list of parts

• Nose/Core 1
  
• Core 2
  
• Forward Monopropellant tank
  
• Forward Hydrogen tank
  
• Cargo Bay/Oxygen tank
  
• Side doors
  
• Aft Hydrogen tank
  
• Aft Monopropellant tank
  
• SOMA (Skylon Orbital Maneuvering Assembly)
  
• Vertical stabiliser with rudder
  
• Wing with aileron (Left and right)
  
• Pre-cooler (Hopefully using the plugin from Interstellar)
  
• Intake
  
• Sabre engine
  
• Canard (Left and right)
  
• Nose gear
  
• Main gear (Left and right)
  

Edited November 7, 2015 by Cpt. Kipard
Progress Update

[tom1499]

I just read through the user manual and it seems that there is no information on RCS. Also good luck. I would love a Skylon!

[EatVacuum]

Cpt. Kipard,

I responded to your last post in the "[REQUEST] Skylon & Saber Engine - Reaction Engines Ltd" (sorry, I haven't figured out how to put in the URL to link the title to that thread), if you're good with it, I will join you here. Whether or not you agree, I do have a couple of thoughts;

I'm still barely into understanding how Unity works, but I believe that the actual orientation of the models does not control how thrust, lift or drag works, they are defined by transforms that are attached to the models and which you point in an appropriate direction. If so the thrust could be offset to align with the centre of mass, I'm pretty sure that since they will have to account for that in the real Skylon, it can be achieved in KSP. If nothing else, thrust vectoring might be able to compensate. I can look into that if you like, and if so, then you can make an accurate model. But if there is anyone out there who is more familiar with Unity who can explain this, and how to do it, I'd love to know for sure.

They probably haven't figured out the RCS yet, the images and videos published are promotional materials, Reaction Engines is, as the name implies, interested in building a hybrid engine. I would assume that the Skylon and LAPCAT images are just concepts to show what it could be used for. Where the thrusters will go is going to have to be based on where the Centre of Mass ends up. Some non-intrusive RCS units could be another thing to add to the list of models you'll need to build Skylon. Like the engines themselves, I'd love to have those - it offends my sense of aesthetics to make a sleek, well proportioned space plane and then have four objects that look like four-way lawn sprinklers sticking out where they would screw up the airflow.

Take a look at this image - http://ca.photos.com/royalty-free-images/space-shuttle-discovery-ov-103-nose-detail-port-left-side/150495422

As you can see, on the space shuttle the thrusters are streamlined, just holes in the fuselage, not "lawn sprinklers". I'm pretty sure that's the way they'll be going for the Skylon. If you look at some design images for the shuttle it should help you to figure out where to place them.

Hope this helps.

[CaptainKipard]

if you're good with it, I will join you here.

Of course.

I believe that the actual orientation of the models does not control how thrust, lift or drag works, they are defined by transforms that are attached to the models and which you point in an appropriate direction. If so the thrust could be offset to align with the centre of mass

If that's true then that will solve one problem, but that's only half of it. The other is that because Skylons Sabre and OMS (Orbital Maneuvering System) thrust vectors are both angled to intersect the center of mass (Sabres are angled down, while OMS is angled up because it's above the center) then the actual heading of the craft will NEVER be aligned to the prograde vector. Now I know that all pods and cores have a "forward" direction (it's what determines what you see on the navball), but I don't know if that's determined by the model importer or the cfg. If it's the importer then I have an idea for solving this particular problem. If it's cfg then that's your area. I'll keep a record of all the important angles and dimensions and if it's necessary then I can always tweak the model later when we start testing. Also if there's no way to change the "forward" direction of a single part at runtime then I'm thinking we might need to create two seperate control cores both with different "forward" directions and allow pilots to choose which one feeds info to the navball (by simply clicking "Control from here") depending on which engines are in use.

Some non-intrusive RCS units could be another thing to add to the list of models you'll need to build Skylon. Like the engines themselves, I'd love to have those - it offends my sense of aesthetics to make a sleek, well proportioned space plane and then have four objects that look like four-way lawn sprinklers sticking out where they would screw up the airflow.

Mine too. Initially i thought I'd build them right into the nose and tail, because that seems most realistic, but that has it's drawbacks when trying to balance a craft with a full cargo bay. And yeah if they haven't figured it out then i guess there's nothing wrong with allowing players to place RCS wherever they want. I'm thinking of making them somewhat similar to those flat B9 RCS units. The only drawback of doing it this way is they'll have to stick out a bit from the fuselage in order to be visible.

What I would like out of this project is to get out of it a Sabre-like engine to play with for general space plane construction. I'd like to be able to model not just the Skylon, but also the LAPCAT and many more plane or spaceplanes for that matter. So if you would please make both the straight and banana curved bodies, I'd really appreciate that. If you don't want to make both, how about making the intake, body and engine exhaust as three separate parts? That way people (not just me) aren't forced to use the curved one.

Actually I had a look at Lapcat before I even started and I think you're confusing two different engines. Skylon uses Sabres (which are hybrids), but Lapcat uses Scimitars. Scimitar (that's the straight one) is based on a Sabre but it has all the rocket parts taken out. It's just an advanced air breathing jet engine. I don't want to promise anything. I'd like to make a Lapcat one day, but let's concentrate on this first.

What do you think?

Also one last thing. I'm curious how you'll make the Sabre behave like a hybrid without programming a plugin. Does that functionality already exist in KSP? Because when I first decided to do this I though I'd just make it an addon for B9 and use his module(s) in the config file.

[Requiem762]

THANK YOU! I have been waiting the longest time for a skylon thank you for making one

[Mekan1k]

B9 Pack has skylon engines....

[CaptainKipard]

Hmm I keep hearing good stories about this...Bee(?).. Nein(?), is it? I should probably download it and see what that engine looks like before posting spammy messages about how I'm going make a realistic model.

LOL *sigh* I love useless naysayers like you Mekan1k. Decent entertainment, thanks. 0 for effort of course because vacuous comments are easy to make, but a solid 6 for attainment.

[DerekL1963]

If that's true then that will solve one problem, but that's only half of it. The other is that because Skylons Sabre and OMS (Orbital Maneuvering System) thrust vectors are both angled to intersect the center of mass (Sabres are angled down, while OMS is angled up because it's above the center) then the actual heading of the craft will NEVER be aligned to the prograde vector.

Just my opinion, but there is such a thing as too much realism... If KSP doesn't need the thrust vectors angled, there's no need to angle them in your model and create problems from thin air. Work within the system, not against it.

[CaptainKipard]

I take your point, and in other areas we'll definitely work to fit into KSP. In this case however we can't ignore physics, because KSP is based on it. If I don't angle the thrust, the ship will tend to spin out of control, or at the very least be extremely difficult to control in space. If you look at an image of Skylon you'll notice the engines sit below the center of mass. There's just no other way to make it work with the exception of redesigning the whole look of the ship, and I really don't want to do that. Not only would I have to raise the engines and wings, I'd have to lower the tail because the tail also has a pair of small orbital engines. The wings house the landing gear so now the gear would have to be placed somewhere else and redesigned. It's too much work. I'm no engineer, and REL have already presented a design that's workable. The only difference to KSP players will be that the nose will not be pointing prograde, but hopefully EatVacuum and I can figure something out to make this as painless as possible.

Edited September 14, 2013 by Cpt. Kipard

[EatVacuum]

Actually I had a look at Lapcat before I even started and I think you're confusing two different engines. Skylon uses Sabres (which are hybrids), but Lapcat uses Scimitars. Scimitar (that's the straight one) is based on a Sabre but it has all the rocket parts taken out. It's just an advanced air breathing jet engine. I don't want to promise anything. I'd like to make a Lapcat one day, but let's concentrate on this first

What do you think?.

You are right, they are different engines, a lot of shared technology but different. I'm not sure why the Sabre is curved the way it is, you'd think the airflow inside the engine would work better if it was symmetrical/straight. In any event, the geometry is going to make it challenging for you. The wings and engines do appear to be below the centre of mass, but I'm wondering if the downward tilt of the thrusters actually lines them up with the CoM. If they do, I think you are right that the Skylon will always be flying a bit nose down when it is in space. On another note, I'm a bit worried about the positioning of the wings and canard - I tried building a smaller but proportionate space plane using mostly stock parts, and with a canard that far forward, it dragged the centre of lift forward of the CoM, and that makes for an unstable plane. Of course, the stock model was only a rough approximation of the real thing but it is something I'll worry about until we can test fly.

I was thinking about scale of this thing - if you build the model true to real world scale, it will be enormous, the hull will be more than 5m radius, i.e. bigger than the Nova Punch rocket parts. On the other hand the Kerblanauts are less than half the size of a human, so maybe we should consider making the scale to be proportionate to the size of the Kerbals not to conform to real world measurements? I don't want to end up with something like the Buran and Canadarm in the Robotic Arms pack - they seem to be made to real world scale and the result is the Canadarm is taller than most of my rockets.

Also one last thing. I'm curious how you'll make the Sabre behave like a hybrid without programming a plugin. Does that functionality already exist in KSP? Because when I first decided to do this I though I'd just make it an addon for B9 and use his module(s) in the config file.

Right now I am frankly simulating Sabre by using an air intake to collect air and convert it to oxidizer. My engine is always burning oxidizer but I'll quote Aerospaceweb.org to justify this and then I'll explain the actual process;

"The purpose of both the jet engine and the rocket engine is to combust a mixture of fuel and oxidizer. This combustion process generates a high-pressure exhaust that creates thrust to push a vehicle forward. The fundamental difference between the two types of engines, however, is where the oxidizer comes from."

So in reality, a rocket can be thought of as a jet engine that gets it's oxidizer in liquid form, or alternately, a jet engine is just a rocket engine with a hole in the front that gets its oxidizer for free.

I'm using an air intake to produce and feed oxidizer to a rocket engine. How it is done is as follows;

1) The air intake, while open takes in air and converts it to oxidizer. This is purely a game mechanic, air is oxidizer, or to be accurate air is 20% oxygen and oxygen is by definition an oxidizer. The rate is such that one intake can feed one engine up to about 22km, after which it falls rapidly behind. At that altitude you should close the intake to reduce drag since the oxidizer collected is too little to be useful.

2) The fuel feed mechanism of KSP delivers the oxidizer to where it can be used, either to the rocket motor to make thrust or to a fuel tank.

3) The rocket engine is always burning oxidizer, initially the intake provides enough but eventually it has to start using the oxidizer stored in the rocket fuel tanks. I've modified the engine's atmosphere curve to be equivalent to the Sabre's - a jet-like Isp of 3240 up to about 22km and a rocket-like Isp of 420 from 23km up, with a brief transition between the two Isps in between.

A purist might point out that I'm really simulating a LACE-type engine (Liquid Air Cycle Engine), but the net effect is the same as if the air was actually being consumed directly. Sabre super cools the air to allow it to function at such height and speed, but it doesn't actually cool the air down to liquid like LACE does. If you compare the Isp and altitude numbers to those quoted for Sabre, you'll see I've cut them back by about 10%. Kerbin's atmosphere height and orbital velocities are smaller than Earth's, using the full values makes it more effective than I think it should be.

I'd like to have a true jet/rocket hybrid, I've been looking at Careo's HydraEngineController which is in the B9 pack. Using it would give me a true dual mode engine, but I haven't found any licensing info for his stuff in B9 Aerospace. Until I do, I won't rip off his work, hopefully he'll be willing to let us use it in return for giving him credit.

[Patupi]

Will there be the visual effect of the cone matching up when the air intake closes? In the videos for Skylon that does look cool.

[B787_300]

The B9 areospace pack has SABRE engines...

[Patupi]

Oy, give him a break! He's talking about rendering the complete Skylon vehicle which B9 does not do. He's just talking about the engine right now.

[CaptainKipard]

I'm not sure why the Sabre is curved the way it is, you'd think the airflow inside the engine would work better if it was symmetrical/straight. In any event, the geometry is going to make it challenging for you. The wings and engines do appear to be below the centre of mass, but I'm wondering if the downward tilt of the thrusters actually lines them up with the CoM. If they do, I think you are right that the Skylon will always be flying a bit nose down when it is in space.

My knowledge of aerodynamics and physics is only at college level but I think I can explain this.

Green represents thrust vectors.

Orange represents prograde vectors

Fig. 1 just shows you which way the exhausts are pointing. The tail engines aren't visible in this particular picture, but higher resolution pics do show a very slight angle. The Sabre exhaust angle is larger. Given the relative positions of the OMS and Sabre engines it's easy to understand why they're angled the way they are, and it doesn't take a genius to work out that intersection of both thrust vectors must be where the CoM is. It looks to be almost in the middle of the plane, which is exactly what you'd expect.

Fig. 2 shows you the rough angle of attack and the prograde vector during the initial air breathing part of ascent. I'm assuming the angle of attack needs to be so large because the wings are relatively small, but I could be wrong. It doesn't really matter, what matters is that the intake cone must be aligned with the relative motion of air to get as much air into the engine as possible. That's why the intake cone is pointing "down". I'm pretty sure that at this stage the main force propelling the plane up is the lift generated by the wings.

Fig. 3 shows you what happens after the intake is closed and the engines go into rocket mode. By this time the angle of attack is not as important because the main force propelling the plane is the thrust of the engines instead of lift. Since that's the case then the prograde vector drifts "up" in relation to the nose of the plane. Of course the plane pitches up too to gain altitude quickly.

Fig. 4 shows you what happens during circularisation. The Sabres are not used for this (although I really don't understand why) instead we have the OMS, which has a different thrust vector, and now to move the plane in the right direction the nose must point up a bit. I suspect players wont bother changing engines for this but there's no really good reason not to include it anyway. If they do decide to use Sabres for circularisation then the nose will of course have to point down relative to prograde by the exact amount as in Fig. 3.

I was thinking about scale of this thing - if you build the model true to real world scale, it will be enormous, the hull will be more than 5m radius, i.e. bigger than the Nova Punch rocket parts. On the other hand the Kerblanauts are less than half the size of a human, so maybe we should consider making the scale to be proportionate to the size of the Kerbals not to conform to real world measurements? I don't want to end up with something like the Buran and Canadarm in the Robotic Arms pack - they seem to be made to real world scale and the result is the Canadarm is taller than most of my rockets.

Don't worry I'm not making it full scale. I posted this question before I started. Most people suggested I scale it down to 64%. I took the fuselage diameter from the Skylon manual (6.75m) and after scaling it I got 4.32m. Rounding it to a standard size I could have gone for 5m or 3.75m. I went for 5m because:

a) I wanted players to be able to lift 2.5m payloads into orbit. The way the Skylon cargo bay is designed doesn't actually use all the space in that cylinder. The space is smaller because you need some space under it for the rear landing gear. As it is right now there's space for a 2.5m part with some small radial attachments.

Skylon has gone through three designs that I know of. There was C1, C2 and D1. Each was larger than the previous one. I'm modelling it using C2 reference material because D1 is still a bit of a secret, and there aren't any images of it. But D1 is even larger than C2 so choosing 5m over 3.75m makes sense.

I'd like to have a true jet/rocket hybrid, I've been looking at Careo's HydraEngineController which is in the B9 pack. Using it would give me a true dual mode engine, but I haven't found any licensing info for his stuff in B9 Aerospace. Until I do, I won't rip off his work, hopefully he'll be willing to let us use it in return for giving him credit.

Ok I'm sure he's a nice guy but it might improve our chances if we wait until I post some decent progress pics before we ask.

Will there be the visual effect of the cone matching up when the air intake closes? In the videos for Skylon that does look cool.

I don't see why not, it's just a simple animation.

Edited September 15, 2013 by Cpt. Kipard

[EatVacuum]

The pictures and explanation are great, that helps a lot.

I'm assuming the angle of attack needs to be so large because the wings are relatively small, but I could be wrong.

You just hit another big concern, those wings are tiny compared to the size. I haven't figured out exactly how lift works, but getting this thing off the ground on the existing runway might be a challenge. To add to it, KSP rocket fuel tanks are heavy foor their size, this thing (and a lot of the new rockets) are using hydrogen which is very light compared to kerosene and the other historical fuels. Compare the relative size of the Skylon's hydrogen and oxygen tanks here (expand the picture next to the "Material Construction" title) with that of the Saturn Five where the oxygen tanks are double the size of the RP-1 (Kerosene) fuel tanks, here. Admittedly part of that huge difference is because so much of the oxygen needed (about 250 tons) is used in the air-breathing stage, but you can look at other hydrogen-burning rockets to see.

Note to self - in the .cfg files put in a lot less fuel than usual for the equivalent size, and also, don't use the usual 11/9 ratio.

Fig. 4 shows you what happens during circularisation. The Sabres are not used for this (although I really don't understand why) instead we have the OMS, which has a different thrust vector, and now to move the plane in the right direction the nose must point up a bit. I suspect players wont bother changing engines for this but there's no really good reason not to include it anyway. If they do decide to use Sabres for circularisation then the nose will of course have to point down relative to prograde by the exact amount as in Fig. 3.

I am intrigued by the OMS system - from the description it doesn't sound like just a typical RCS system (which is generally a single propellant gas under pressure or a hypergolic mixture), sounds more like a lower thrust conventional rocket motor. The blurb describing it, found on the Skylon link above says;

"Whilst in orbit the main propellant tanks are vented and allowed to warm to ambient conditions. Propulsion and attitude control are provided by the Orbital Manoeuvering System (OMS) or Reaction Control System (RCS). This uses a common LH2/LO2 propellant storage which is heavily insulated and cryogenically cooled. This system can remain operational on orbit up to 7 days. The RCS employs gaseous propellants supplied by the Gaseous Propellant Supply System (GPSS). The GPSS also supplies reactants to the fuel cells and the auxiliary power turbines."

The second sentence makes it sound like the OMS and RCS are the same system, but then the third and fifth sentences imply they are separate. From the point of simulating it in KSP, I think we need to treat them as separate. It's also interesting that the main tanks are allowed to vent, it may be that only the auxillary fuel tank, which is very small, will have fuel for deorbit, unless it's cold enough up there that they still have some usable hydrogen and oxygen after it comes up to ambient temperature (and presumably vaporizes). That also implies a completely unpowered landing, which is pretty hard to do in KSP. Powered space plane landings are challenging enough.

Don't worry I'm not making it full scale. I posted this question before I started. Most people suggested I scale it down to 64%. I took the fuselage diameter from the Skylon manual (6.75m) and after scaling it I got 4.32m. Rounding it to a standard size I could have gone for 5m or 3.75m. I went for 5m.

I would have thought 50% would be the scale, based on Kerbals being 1m tall, here's good ol' Bill standing next to a 1.25m tank and Jeb's Big stick (a measuring tool someone made). The thinner lines are .1m, the wider one second from the top is the 1m mark. Bill comes up to the 8th 0.1m line, but there's about .2m below the stick. So definitely 1m tall, but I guess most people aren't 2m (6'6") tall which 50% scale would make Bill if we rescaled him. But on the other hand 64% only makes him 1.56m (5'1"). I guess 64% is good, and if it seems to be the standard, it works for me. Once you have built the models we could always use scale and rescale in the configs to make 3.75M version, or even smaller.

And related to your ponderings on where to put the thrusters, there is a convention described in the Wikipedia article on RCS;

"Location of thrusters on spaceplanes

The suborbital X-15 and a companion training aero-spacecraft, the NF-104 AST, both intended to travel to an altitude that rendered their aerodynamic control surfaces unusable, established a convention for locations for thrusters on winged vehicles not intended to dock in space; that is, those that only have attitude control thrusters. Those for pitch and yaw are located in the nose, forward of the cockpit, and replace a standard radar system. Those for roll are located at the wingtips. The X-20, which would have gone into orbit, continued this pattern."

If we find out otherwise, we can correct, but I don't think we will go far wrong is you go with this as a basis. So, I am thinking the fuselage itself should break down into six components, from the bow back - small nose cone w/rcs, big forward fuel tank, cargo bay, big aft fuel tank (including RCS fuel), a thin aft tail section w/RCS, a small OMS rocket. There'd also be two more wingtip RCS units. The more I look at this, the more I realize how huge a job modelling this is going to be, what with animating the cargo bay doors, retractable under carriage etc. I guess I do have the easy part

[DerekL1963]

And related to your ponderings on where to put the thrusters, there is a convention described in the Wikipedia article on RCS;

"Location of thrusters on spaceplanes

The suborbital X-15 and a companion training aero-spacecraft, the NF-104 AST, both intended to travel to an altitude that rendered their aerodynamic control surfaces unusable, established a convention for locations for thrusters on winged vehicles not intended to dock in space; that is, those that only have attitude control thrusters. Those for pitch and yaw are located in the nose, forward of the cockpit, and replace a standard radar system. Those for roll are located at the wingtips. The X-20, which would have gone into orbit, continued this pattern."

That sounds suspiciously like an opinion... doubly so since the NF-104 was a USAF aircraft and wasn't developed until years after the X-15 program had been transferred to NASA. You'll also note the claim is unsupported by cites or sources.

FWIW, the Shuttle was always intended to dock, and while the early versions of the final design featured wingtip RCS pods they were ultimately deleted.

[CaptainKipard]

... how lift works ...

Lift is just an arbitrary number in the cfg; it has nothing to do with the shape of the wing luckily so you can cheat a little there if you need to.

... using hydrogen ...

I'm pretty sure adding a custom resource is relatively easy. There's some info about it in the tutorial thread, but if you have a problem you can always post a question.

... OMS system ...

Well some materials refer to an auxilliary fuel tank so it must be a rocket. It's actually a pair of double exhaust rockets but that's not important for implementation.

... unpowered landing ...

Good point. We should allow a powered approach and when we do then there wont be a need for a seperate auxiliary fuel tank. I'm sure players wont care about details like that.

... we could always use scale and rescale ...

Looks like a plan.

... where to put the thrusters ...

... wingtip RCS pods ...

Since Skylon is meant to be capable of docking, then simple attitude control is not enough. Like I said before I think adding some seperate RCS parts is the best way to go. I've seen Skylon animations showing propellant being ejected from both the nose and the tail but the docking animation doesn't show anything. It's not that important. When we release the pack then in the craft file we can just add some surface mounted RCS thrusters which I'll also make. The RCS Build Aid mod will be helpful for positioning them, and also making sure wet and dry CoM is in the same place. I don't really want to do it that way; I would rather have them built in, but it's going to be too much work getting the whole thing balanced enough to translate without changing attitude.

... fuselage itself should break down into six components, from the bow back - small nose cone w/rcs, big forward fuel tank, cargo bay, big aft fuel tank (including RCS fuel), a thin aft tail section w/RCS, a small OMS rocket. There'd also be two more wingtip RCS units. The more I look at this, the more I realize how huge a job modelling this is going to be, what with animating the cargo bay doors, retractable under carriage etc. I guess I do have the easy part

You forgot the control core. Actually it's even more complicated than that. I'm working on the mid section right now and it's proving to be deceptively difficult. It looks simple and the overall shapes kind of are, but I have to constantly keep in mind that I'm going to break things up into sections later. It's a bit of a balancing act. e.g. the wing base extends beyond the ends of the cargo bay in both directions. Now in order to make the wing mesh look smooth I can't just slice the whole thing exactly where the cargo bay ends. I'll have to cut a bit further. Luckily the Skylon cross sections show that's where the oxidiser tanks are so I'm thinking the cargo bay part should double as an oxidiser tank. And there's still the issue of the heading/prograde discrepancy. I have one idea for that but it's a bit of a hack. I was hoping there's a more elegant solution by using something in the cfg. Could you look into that too?

Here's how I see it.

-Nose/Core 1

-Core 2

-Forward Monopropellant tank

-Forward Hydrogen tank

-Cargo Bay/Oxidiser tank

-Aft Hydrogen tank

-Aft Monopropellant tank

-OMS

-Vertical stabiliser

-Rudder

-Left wing

-Left aileron

-Left intake

-Left "precooler" (Just a structural part)

-Left engine

-Right wing

-Right aileron

-Right intake

-Right "precooler" (Just a structural part)

-Right engine

-Canard

-Nose gear

-Left rear gear

-Right rear gear

-One or more RCS thrusters (depending on how they will be placed)

[Hyratel]

uh.. guys?

ModularFuelSystem allows for proper fuel setups. HHHO___OHHH tanks on both of those

[CaptainKipard]

Are they SSTOs? That first one only has 2658m/s of dv.

[Guest]

Skylon doesn't need big wings, because it's a lifting body design. Essentially, the whole body functions as a giant wing. Unfortunately, KSP doesn't simulate that.

[CaptainKipard]

Can't I just add deflectionLiftCoeff to every part?

[CaptainKipard]

Current progress

[image Removed]

Edited February 16, 2015 by Cpt. Kipard

[EatVacuum]

That sounds suspiciously like an opinion...

Definitely, but there's a couple of obvious ways to do RCS, depending on the geometry of your space craft.

For a relatively short shape like a sphere or a relatively stubby cylinder like an Apollo service module, you can just stick a bunch radially around the middle/waist, usually four works well because of our tendency to think up/down. left/right, forwards/backwards - it's how we define space and how our controls tend to work, from joysticks on up. Four RCS allows them to work in balanced pairs for most of the combinations of rotation and translation, except for forwards/backwards and roll where all four can be used.

Something long and thin like Skylon has a higher moment of inertia (don't flame me if I'm using the wrong term, university physics was a long time ago) for yaw and pitch. So it makes sense to have sets at each end to give you more leverage to rotate the thing. Given that the Skylon is proportionately much longer and thinner than a shuttle, it's pretty much going to have to have RCS at the ends. On the other hand, those wings are stubby, so you'd think that if the Space Shuttle didn't need wing thrusters, then Skylon wouldn't either. But there's a couple of heavy engines going on the ends of those wings, which is going to increase the roll inertia, which wasn't the case for the shuttle. So I'd think that Skylon might need them after all. That's my opinion, but it's based on some consideration and analysis, your mileage may vary. It's likely that the wing RCS are going to be implemented as separate components, based on Cpt. Kipard's parts list earlier in this thread, so I guess you will have a choice in any event.

[Requiem762]

Model looks great so far

[dizzysaurus]

This looks awesome so far