SSTO cookbook.

[Mister Kerman]

Alright boys. I recently got into the technical challenge of designing MK2 SSTO's. I had great success with one of my early designs. I tweaked it to my best ability to be as efficient and useful as I can make it.

Since then I've tried making different designs but they don't seem to come close to what my first SSTO accomplished. A logical person would just use the one that works, but I prefer to experiment since I'm still very much learning. I'm toying with less weight, engines, intakes, drag, and fuel but it seems like everything I try falls short. (Very short.)

I can just about guarantee there's another thread with the info I'm looking for, but I am very lazy/at work supposed to be doing stuff, so instead I'm using my short amount of free time to simply ask for help. (And let's face it; everybody in this community loves to jump on a new thread and give that oh-so-satisfying answer before anybody else can, and I think there will be different answers coming from people that have different building styles too, which I'm looking forward to!)

I want some recipes for my SSTO cookbook. I'm starving for all kinds of SSTO's; whatever kind you guys like to cook up. I want a very generalized format just like the ingredients in a recipe for food.

My current working SSTO recipe is:

3 shock cone intakes

3 R.A.P.I.E.R. engines

11.08 Lift rating

23.1T Mass

1280 LF

880 Oxidizer

I'm not sure what info is most applicable to be honest so I'd like some help with finding the best "ingredients" for the recipes, but I'm sure you guys get it. You're all so smart.

EDIT: Here's my SSTO Spaceplane. 9th experimental craft - Halberd MK3

It's an album link. Sorry about that...

DFUaY

">Javascript is disabled. View full album

Edited September 23, 2015 by Mister Kerman

[Nothalogh]

Ditch the Structural Intakes, they're worthless.

Squad needs to delete them, or completely rebuild them

[ainamogel]

1) Build whatever you want. Make the total mass a few tons or less. Put some fairings around it.

2) stick it on an Orange tank.

3) stick it on a half orange tank.

4) stick it on a Mainsail

5) drive it up to orbit.

Voila, SSTO the easy way.

Ha ha.

(Perhaps Mainsails are a bit overpowered for the new atmosphere?)

Sorry for the diversion from your actual, legitimate question.

Ainamogel

[Wjolcz]

TWR and the max speed you can achieve at high altitudes are cruicial when designing an SSTO (don't forget about lift if it's meant to be a plane). At least for me. What I also do is estimate more or less how much liquid fuel I will need in the lower atmosphere, then empty those LF-only tanks and switch the engines/engines' mode. Then I look at KER. Set the alt and speed values and see how much dV and TWR I will have left after the air gets too thin for the air-breathers.

And fly a lot, of course. Always test your SSTOs in different conditions.

[capi3101]

Yeah, driving home ainmogel's point, you probably oughta specify that you're talking about spaceplanes. Otherwise you get jerks like us that will point out that SSTO can also refer to rockets...

But back to your question: DocMoriarty used to have a downloadable guide to answer your question, and its what got me "over the hump" and into the full plane jockey business prior to 1.0.x. I've just today seen him with a new design for post 1.0.x, so it's possible that guide has been updated or will be in the near future. I'll check. I myself have switched over to FAR at this point but I've tried to keep up with the stock jockeys and what they're rolling with; I'm sure one or more of them will come along eventually. I've got my own recipes for FAR that work, and I'll share them on request.

For stock:

1. Start with your payload. That's going to be anything that ain't fuel or engine for the plane.

2. Assume a 25% payload fraction - so multiply the payload's mass by four. That's your theoretical mass.

3. Add one turbojet per fifteen tonnes of theoretical mass, or one RAPIER per thirteen tonnes. If using turbojets, add ~100 kN of rocket thrust per engine (with the higher vacuum Isp the better).

4. For each air-breathing engine, add one intake (does not matter which). Add 150 units of LF per air-breathing engine.

5. For each ten tonnes of theoretical mass, add one unit of lift. (This one I'm shaky on; a stock jockey can and should correct me if this is wrong).

6. Add enough rocket fuel tanks so that your plane has approximately 1800 m/s of delta-V.

7. Balance the intakes to engines, make sure the plane's CoL will remain behind the CoM in flight (though not too far), and if possible try to keep the CoM from moving much at all.

8. Serve chilled, with a slice of lemon.

Edited September 22, 2015 by capi3101

[Wjolcz]

Yeah, driving home ainmogel's point, you probably oughta specify that you're talking about spaceplanes. Otherwise you get jerks like us that will point out that SSTO can also refer to rockets...

But back to your question: DocMoriarty used to have a downloadable guide to answer your question, and its what got me "over the hump" and into the full plane jockey business prior to 1.0.x. I've just today seen him with a new design for post 1.0.x, so it's possible that guide has been updated or will be in the near future. I'll check. I myself have switched over to FAR at this point but I've tried to keep up with the stock jockeys and what they're rolling with; I'm sure one or more of them will come along eventually. I've got my own recipes for FAR that work, and I'll share them on request.

For stock:

1. Start with your payload. That's going to be anything that ain't fuel for engine for the plane.

2. Assume a 25% payload fraction - so multiply the payload's mass by four. That's your theoretical mass.

3. Add one turbojet per fifteen tonnes of theoretical mass, or one RAPIER per thirteen tonnes. If using turbojets, add ~100 kN of thrust per engine (with the higher vacuum Isp the better).

4. For each air-breathing engine, add one intake (does not matter which). Add 150 units of LF per air-breathing engine.

5. For each ten tonnes of theoretical mass, add one unit of lift. (This one I'm shaky on; a stock jockey can and should correct me if this is wrong).

6. Add enough rocket fuel tanks so that your plane has approximately 1800 m/s of delta-V.

7. Balance the intakes to engines, make sure the plane's CoL will remain behind the CoM in flight (though not too far), and if possible try to keep the CoM from moving much at all.

8. Serve chilled, with a slice of lemon.

1800m/s dV? That's not the right number for stock atmo. You need at least 3500m/s if playing stock. Unless you're talking about the dV after you are going fast enough and ready to switch to LF/O engines?

Edit: nevermind. It's late here and I need to sleep appearantly.

Edited September 21, 2015 by Veeltch

[Mister Kerman]

Yes... good points.

I'm mostly referring to spaceplane SSTOs, and I'm playing stock. Hopefully that nudges the thread in a more appropriate direction. Thanks for the replies so far fellas!

[Vegetal]

Most important of all: Drag is king.

[Mister Kerman]

Capi3101:

That's exactly the kind of thing I'm looking for. I'll have to do some calculating it sounds like, to figure out my DV. I usually just "wing" it. I usually just shove everything into space with an abhorrent amount of fuel and boosters.

Hope you guys have some other tasty recipes for me to try out. :]

Also Vegetal:

Not precisely sure what you mean by that. I'm trying to get away with as little as possible right now in every category without downgrading below MK2 size. I eventually want to get up to MK3 but I haven't the balls.

Edited September 22, 2015 by Mister Kerman

[Val]

...

I want some recipes for my SSTO cookbook. I'm starving for all kinds of SSTO's; whatever kind you guys like to cook up. I want a very generalized format just like the ingredients in a recipe for food.

...

Here's my SSTO Spaceplane. 9th experimental craft - Halberd MK3

http://imgur.com/a/DFUaY

As I understand it, you want to learn for yourself how to build spaceplane SSTOs.

If you're up for reading your way to knowledge, I can highly recommend the posts from GoSlash27 in this thread, "simple" rule to build spaceplanes? (There're are also some ramblings by me on later pages)

If you're more inclined to practical studies or want to supplement Slashy's knowledge, (shameless self-plug) then you can download and study my Mk2 2-RAPIER design. It's a little bit heavier than yours, but it is very powerful and well balanced.

If you do decide to download it. Read the Ascent Profile description, take it to orbit, to see how it performs. Maybe land it again.

Then go to the SPH and study it closer. Some important features to note:

• Using only parts with 2000^o or higher temperature rating for anything outside the cargo bay, including RCS pods.
  
• The only surface attached parts, outside the cargo bay, are wing parts, landing gear, RCS and tanks for mounting engines and intakes.
  
• No struts, except to secure cargo in the bay. (This also applies to all of my bigger designs, with a couple of exceptions)
  
• CoL position relative to CoM and Dry-CoM (All fuel removed from tanks) to keep it balanced at all fuel levels.
  
• Main Landing gear position below CoM to avoid wobbling and veering off the runway during take-off.
  
• Pull off the external tanks and Engines.
  
• See that the landing gear is mounted to the fuselage, also for increased runway stability.
  
• Notice how the wings and canards are mounted with Angle of Incidence. (Leading edge higher than trailing edge)
  This has several benefits:
  
  • Reduces drag from fuselage.
    
  • Decreases cosine thrust losses because the engines are pointing closer to prograde.
    
  • Allows you to take-off and land with the nose lower, to avoid tail strikes and better view from IVA.
    

  [*]All stack-nodes terminated with intakes, engines, nose or tail cones (green attachment nodes), reduced drag.

Then try to apply the above to your own design.

Hope this is useful.

[Mister Kerman]

As I understand it, you want to learn for yourself how to build spaceplane SSTOs.

If you're up for reading your way to knowledge, I can highly recommend the posts from GoSlash27 in this thread, "simple" rule to build spaceplanes? (There're are also some ramblings by me on later pages)

If you're more inclined to practical studies or want to supplement Slashy's knowledge, (shameless self-plug) then you can download and study my Mk2 2-RAPIER design. It's a little bit heavier than yours, but it is very powerful and well balanced.

If you do decide to download it. Read the Ascent Profile description, take it to orbit, to see how it performs. Maybe land it again.

Then go to the SPH and study it closer. Some important features to note:

• Using only parts with 2000^o or higher temperature rating for anything outside the cargo bay, including RCS pods.
  
• The only surface attached parts, outside the cargo bay, are wing parts, landing gear, RCS and tanks for mounting engines and intakes.
  
• No struts, except to secure cargo in the bay. (This also applies to all of my bigger designs, with a couple of exceptions)
  
• CoL position relative to CoM and Dry-CoM (All fuel removed from tanks) to keep it balanced at all fuel levels.
  
• Main Landing gear position below CoM to avoid wobbling and veering off the runway during take-off.
  
• Pull off the external tanks and Engines.
  
• See that the landing gear is mounted to the fuselage, also for increased runway stability.
  
• Notice how the wings and canards are mounted with Angle of Incidence. (Leading edge higher than trailing edge)
  This has several benefits:
  
  • Reduces drag from fuselage.
    
  • Decreases cosine thrust losses because the engines are pointing closer to prograde.
    
  • Allows you to take-off and land with the nose lower, to avoid tail strikes and better view from IVA.
    

  [*]All stack-nodes terminated with intakes, engines, nose or tail cones (green attachment nodes), reduced drag.

Then try to apply the above to your own design.

Hope this is useful.

Appreciate the tips Val. Although I've read a few guides and get the principals, I just want to start making better MK2s before I move up to cargo capable MK3s. I might try angled wings, but I'm not sure how that will affect my in flight behavior (AKA prograde node being just a hair higher than it should be I think? Maybe not?)

This format I chose was specifically to see the balance of other people's successful designs. I want to see if someone is using a "X-amount-of-tons" craft, how much lift and engine power it will need roughly, without forcing people to go into details or flight profiles. I welcome that extra information from people, but it's not exactly what I'm looking for. Just raw "ingredients" for successful SSTO spaceplanes.

EDIT: Just looked at you craft. I was trying to reduce size and in turn trade it for engine power and basically make an orbital bullet, but you craft seems to be heavier as well as having less engine power. Once again, I always try to shove stuff into space whre maybe I should try a lottle finess. Your plane is like a fat figure skater; graceful and large. Mine is more like a midget being fired from a cannon at a circus...

DOUBLE EDIT: I hate canards lol. Trying to avoid those regardless of how terribly useful they are.

Edited September 22, 2015 by Mister Kerman

[Val]

Appreciate the tips Val. Although I've read a few guides and get the principals, I just want to start making better MK2s before I move up to cargo capable MK3s. I might try angled wings, but I'm not sure how that will affect my in flight behavior (AKA prograde node being just a hair higher than it should be I think? Maybe not?)

This format I chose was specifically to see the balance of other people's successful designs. I want to see if someone is using a "X-amount-of-tons" craft, how much lift and engine power it will need roughly, without forcing people to go into details or flight profiles. I welcome that extra information from people, but it's not exactly what I'm looking for. Just raw "ingredients" for successful SSTO spaceplanes.

The link I posted has posts of the type "for x amount of cargo you need this much craft", covering both Mk2 and Mk3 designs.

I my opinion, flight profiles are just as important as design. SSTOs are very sensitive to how you fly, especially in the high speed regions above 10 km. Pitching up too hard, ascending too steeply, or going a 100 m/s slower can easily end up costing you a 1000 m/s of dV in orbit, if you reach orbit at all.

I might try angled wings, but I'm not sure how that will affect my in flight behavior (AKA prograde node being just a hair higher than it should be I think? Maybe not?)

You really should try it. Angling the wings puts the prograde closer to where it should be. Unless you try to go Mach 2+ at sea-level.

Here's the explanation why:

Like most of us, you were probably taught that lift works like this.

Pictures showing lift without Angle of Attack. It's not wrong, but it's not the full picture. At least 2 things are missing in relation to KSP.

1. Camber in wings only provide part of the lift, in most flight regimes.
   
2. KSP does not model cambered wing profiles.
   

So we all have a natural tendency to mount wings with zero Incidence. When really we shouldn't.

Wings in KSP always need Angle of Attack to provide lift. So if you mount wings with no Angle of Incidence, then the whole craft needs to be pointed up for the wings to lift it.

When wings are mounted with Incidence, the nose can be lowered closer to the direction of movement, reducing drag from the fuselage. Drag from the wings will of course remain unchanged, but that is usually much less than drag from fuselage.

And in real life even cambered wings are mounted with incidence, for the same reason.

"Wings are typically mounted at a small positive angle of incidence, to allow the fuselage to have a low angle with the airflow in cruising flight. Angles of incidence of about 6° are common on most general aviation designs."

Source

The amount of incidence you need depends on mass and wing area. I usually go for 5 degrees Incidence and a wing area 1/8th to 1/6th of the mass in t. (not counting wing area from Mk2 fuselage)

- - - Updated - - -

Just looked at you craft. I was trying to reduce size and in turn trade it for engine power and basically make an orbital bullet, but you craft seems to be heavier as well as having less engine power. Once again, I always try to shove stuff into space whre maybe I should try a lottle finess. Your plane is like a fat figure skater; graceful and large. Mine is more like a midget being fired from a cannon at a circus...

I actually firmly believe, my craft ends up going faster, even if it is heavier and has less engine. Yours will undoubtedly get off the runway faster, but mine will probably pass mach 2 first. For SSTOs low drag is King.

I hate canards lol. Trying to avoid those regardless of how terribly useful they are.

Canards are a design choice. To convert Canards to Elevators, you just have to move the main wings from slightly behind CoM to slightly in front. Then remove Canards and install Elevators at the back of the plane.

I think the reason Canards are so prevalent, is because fuselages are generally heavier in KSP relative to engines. And people tend to over-wing. So CoL often ends up further back and CoM further forward, than for a similar real world design. And because usually the nose is further from CoM than the tail which gives more control authority.

Edited September 22, 2015 by Val

[capi3101]

Going to mention that I saw a couple of typos in my original post this morning, and I wouldn't have said anything except that they were the kind of accidental prepositional substitutions that kinda changed what I intended to say. I've gone ahead and fixed them. Changes the "recipe" a tad.

I'll also add that having sufficient control of the craft is a thing; DocMoriarty used to recommend 1-2.5 rudders per engine (generally a Standard Canard or Tail Fin) and 1 aileron per ten tonnes theoretical mass (the old style large control surface; I think it got replaced by Elevon 3). Of course those were in the pre-1.0 days so I couldn't tell you if those figures are still good or not. Really, control surfaces are all about how far away they are from the Center of Mass and how big they are (i.e. how much leverage you can get from them). Pitch is the one that has generally given me trouble - ideally your elevators are not in-line with the main wing. If they are (say, with a tail-less delta design), that's the time to also consider a set of canards - ugly or not. And don't overlook the utility of SAS units - A) at some point your plane becomes a rocket and you still have to be able to turn the thing, and anything that can take stress of your control surfaces is generally a good thing. Don't overdo it, of course; one SAS unit is usually enough. DocMoriarty used to recommend 1.5 kN of SAS per theoretical tonne of mass; again that was in the pre 1.0 days and my experience there is that those numbers overdo it these days. But I'll throw it out there nonetheless.

Gear: forgot to talk about gear. One at the nose, two in line slightly behind the CoM, and the further apart you can put the two rear gear the better. If you can mount them on a Small Hardpoint on the wings, so much the better - especially if all you've got are Small Gear Bays. Avoid the bush plane gear for spaceplanes; they work okay for low-speed surveyor planes close to KSC though, and they can be used to good effect for low-tech jet-powered "rovers". Rear gear should be set for full braking torque and steering disengaged if possible; front gear should be steering engaged, brakes disabled. The heavier the plane, the larger the gear you're going to want. Don't be afraid to add more rear gear. If you have a problem with tail strikes, consider a set of "kickers" right at the tail; it's kinda cheatsy, but if it saves your plane, well......

[Mister Kerman]

Val:

You really know your stuff. I'm definitely going to reread these posts before I try designing another craft.

Capi3101:

Also very helpful. About reaction wheels; I would like to use them, but it seems like everytime I use the MK2 size SAS unit, the thing blows up. I mostly use it because of the battery, but like you said more control is never a bad thing.

Everyone else:

Most other things I have a pretty good handle on. Mostly focusing on trying to make my craft minimalistic as possible without sacrificing performance. I don't want unnecessary drag or weight etc. So if anyone else has some craft "ingredients" they'd like to share, that'd help show some trends!

[Val]

Val:

You really know your stuff. I'm definitely going to reread these posts before I try designing another craft.

...

Thank you. Your praise is much appreciated.

Just remember that my way of doing it is not the only way. I have certain preferences for looks, what parts should be used and how the game should be played, and it probably influences the advice I give. You (and others) should definitely also pay attention to GoSlash47. He has many counterpoints and alternatives that are just as good or better than what I come up with.

[tseitsei]

Yep Val and GoSlash both know what they are talking about. Those are the 2 guys that I have learned most of my SSTO spaceplane building knowledge

[capi3101]

Also very helpful. About reaction wheels; I would like to use them, but it seems like everytime I use the MK2 size SAS unit, the thing blows up. I mostly use it because of the battery, but like you said more control is never a bad thing.

I usually stick with the Inline Stabilizer no matter what size plane I'm building; admittedly, I haven't had much use for the Large ASAS Module as yet - haven't tried building any 2.5 or Mk3 planes lately. Usually house them in either a Service Bay or short Cargo Bay, sometimes with batteries as well depending on if there's room. If I'm sticking them in Cargo Bays, I try my best to leave the sides of the bay clear - the front and back ends of the bay make great mount points for fore-and-aft (i.e. prograde-and-retrograde) firing RCS ports, something a lot of good plane designs lack. They only work if their thrust doesn't hit other part of the plane, of course. Speaking of RCS - if you ever need RCS control for a plane (say, you're building a passenger or fuel ferry and need to be able to dock the thing), stick to the linear ports (the kind that only fire in one direction); use blocks sparingly, if at all.

The RCS Build Aid mod is worth its coder's weight in gold bricks - even if you don't use it to help you build a balanced craft that doesn't exhibit unwanted torque from RCS thrusters, it's useful for seeing how far/in what direction your CoM shifts as you fly (see my first post for the importance of that particular phenomenon).

[Starhawk]

A general set of values to start from might be:

1 Rapier per 20 tonnes of spaceplane

1 Shock Cone per Rapier

5 lift per 20 tonnes of spaceplane (many excellent builders use much less)

5 tonnes of excess fuel/cargo/passenger compartments

1 command pod

landing gear

the rest of the weight is fuel for your ship - I like to start with the tanks full of liquid and half-full of ox and tweak from there

add control surfaces, airbrakes, batteries, solar panels, and reaction wheels to taste

edit: Oh yeah, Drag is King!

Happy landings!

Edited September 22, 2015 by Starhawk
forgot intakes!

[Nothalogh]

your plane is like a fat figure skater; graceful and large. Mine is more like a midget being fired from a cannon at a circus...

And now I'm dying of laughter

[The_Rocketeer]

EDIT: Here's my SSTO Spaceplane. 9th experimental craft - Halberd MK3

It's an album link. Sorry about that...

http://imgur.com/a/DFUaY

FWIW, you can embed imgur albums by using [ imgur ] and [ /imgur ] with the code at the end of the URL (bold above).

[panzer1b]

I usually go with

4000-5000 LF

100-200 OX

1.5t payload (2 missiles or bombs)

~35-37 tons

~10 lift rating total

1 rapier

1 nuke

all the other misc stuff to make it functional (landing gear, RTG, cockpit, ect).

This (if done right) will get you to laythe, bop, and pol, then back to kerbin ALL WITHOUT REFUELING! (provided you dont bring missiles, with missiles the most ive ever pulled off is 7K dV in LKO).

[Mister Kerman]

Capi3101: That RCS ports in the cargo bay is genius.

StarHawk: I usually reserve a short tank of LF specifically to get into orbit. Everything else is LFO tanks. Any oxidizer I bring back down with me just gives me a gauge of how efficiently I got myself into orbit. Thank you very much for your SSTO breakdown! Also... what is this "drag is king" nonsense? :}

Panzer: Whooooooah. That's a serious SSTO. I don't think I'll be able to pull off any wizardry like that for a while yet. Very cool stuff.

Edited September 24, 2015 by Mister Kerman