Cargo SSTO, large payload in size and weight, trying to make it work under FAR

[fatcargo]

Are there any designs for a cargo SSTO for physically very large payloads that work with FAR, not just stock aerodynamic model ?

I've built good craft on older KSP versions using community-fixed B9 packs which worked quite well.

And now we have B9 v5.2.6 compatible with KSP v0.25 and all was great for me. Until i discovered that stock jets got nerfed after adding B9 pack (MM definitions included killed turbojets), so i had no other choice but to use SABREs.

I wish B9 did left stock jets to players who wish to have fun the kerbal way, and not try to turn KSP in another flight simulator. And this would not

make much impact on my designs except that i would like to share my crafts with community, so making custom engines just to circumvent yet another limitation is out of the question.

Then i added FAR hoping for "lifting body" and easier lifting forces to counteract nerfed turbojets, but instead was met with more limitations (like 1/2 thrust of all air-breathing engines, stalls, failures etc ...).

So, one of the questions is : are there any non-B9 packs that have wings with huge non-FAR lifting factors like HW21 Heavy Wings AND don't stomp over stock parts ?

Another question is about my newest SSTO version that i'm trying to make work under FAR.

Have a look at pics

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This behemoth stands at over 250 tons on take-off, but due to FAR giving me headache i can't even get payload up as it falls off craft on take-off. Craft can survive this but it either explodes (or if it survives lower atmosphere), can't build up enough speed with SABREs in air-breathing mode after 30km altitude. Hence the ridiculous amount of intakes and engines.

Also, does anyone know of any cargo bay that can be SCALED UP or at least is already large, much larger than what is offered as stock and B9 parts ? I'm growing tired of this SSTO business. I love SSTO idea of bringing payloads to LKO, but B9 and it's FAR requirements are killing all the fun out of KSP, condemning players to some puny kerbal/fuel transports

Edited November 9, 2014 by fatcargo

[Starman4308]

Rule #1 of designing in FAR/NEAR: if it doesn't look like a real-world aircraft or rocket, it probably is not going to fly, at least not at any great speed. For example: your bird is a biplane. No modern cargo aircraft or high-performance aircraft (SR-71, fighter jets, etc) are biplanes. It's gotta go: that second wing isn't going to generate much lift with FAR going, and it will contribute to drag. You should also attempt to make the fuselage much slimmer: it's too boxy to be efficient in FAR.

Rule #2 of designing in FAR/NEAR: Unlearn everything you learned, and start back over from small stuff. Trying to go straight to monster cargo SSTOs is not going to work.

Rule #3 of designing in FAR/NEAR: If ever confused, look at Wanderfound's designs, or pop him a message. Guy's great with SSTOs.

Also: Why did you ever install FAR if you wanted to avoid "KSP becoming a flight sim"? FAR is very deliberately attempting to emulate realistic aerodynamics.

[Wanderfound]

Wait a couple of months; Mk3 stock cargo bays are on the way.

In the meantime, if you're carrying external cargo, streamline it, use decouplers to stick temporary nosecones on the payload.

And, yeah, try to build something that looks like a real plane. The stock aero exploits don't work in FAR.

[Empiro]

If you're trying to build a craft that can lift 3 5m tanks into orbit, then I don't think any mods have parts that will be large and strong enough. You're better off trying to use procedural wings and tweak scale to try to get the parts larger, but it'll still be really hard. The wings are gong to have to be absolutely massive.

[Hodo]

Your biggest problem is your craft is going to generate to much drag by itself, without having to contend with the added weight of the cargo.

This is one of my old heavy lifters, it could haul 108 tons into orbit pretty easily.

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The design was a continuation of this design....

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This old design could take 72 tons into orbit.

[fatcargo]

Thank you all for a quick and detailed reaction, especially Wanderfound for gracing this thread with his comments.

Rule #1 of designing in FAR/NEAR: if it doesn't look like a real-world aircraft or rocket, it probably is not going to fly, at least not at any great speed.

Well i did manage on second try to make a flyable test SSTO with FAR that resembled realistic designs, it just did not do much except bring some fuel into 150x150 orbit and a couple of Kerbals in cockpit.

Knowing FAR's reputation of unforgiving physics i was damn surprised and pleased i got it working this quick.

For example: your bird is a biplane. No modern cargo aircraft or high-performance aircraft (SR-71, fighter jets, etc) are biplanes. It's gotta go: that second wing isn't going to generate much lift with FAR going, and it will contribute to drag.

Yeah i was afraid od that, the high lifting power to convert all that thrust into vertical force for low-

speed / thick-atmosphere isn't going to cut it in supersonic / stratospheric flight.

You should also attempt to make the fuselage much slimmer: it's too boxy to be efficient in FAR.

And you pretty much nailed down my predicament : how to have large payload space when aerodymics dictate a flat craft ?

Rule #2 of designing in FAR/NEAR: Unlearn everything you learned, and start back over from small stuff. Trying to go straight to monster cargo SSTOs is not going to work.

Rule #3 of designing in FAR/NEAR: If ever confused, look at Wanderfound's designs, or pop him a message. Guy's great with SSTOs.

I already did read through it's posts in "Kerbodyne SSTO Division: Omnibus Thread" a must-have reference. I especially appreciate the info on FAR analysis during construction.

Also: Why did you ever install FAR if you wanted to avoid "KSP becoming a flight sim"? FAR is very deliberately attempting to emulate realistic aerodynamics.

Te repeat myself in more detail : i installed new B9 pack that is rebuilt by part pack authors for new KSP 0.25 and discovered that stock turbojets, my main source of power have been severely downsized. After reading through docs/comments by authors about switching to FAR i tried to add FAR, hoping to compensate for that loss and ran into even more problems and restrictions. If only they left the turbojets alone and not force players into anything, i would have my fun the kerbal way.

[fatcargo]

Wait a couple of months; Mk3 stock cargo bays are on the way.

In the meantime, if you're carrying external cargo, streamline it, use decouplers to stick temporary nosecones on the payload.

And, yeah, try to build something that looks like a real plane. The stock aero exploits don't work in FAR.

Thanks for the input, that's my problem with payloads : about the only way to send some non-aerodynamic (even assymetrical) structures is by shrouding them in aerodynamic shells. For that i tried using procedural fairings but never got them past design stage since they are not meant to be reusable.

If procedural fairings could be adapted / upgraded for reusability, it could be with hollow fairing bases with standard circular cross-section shapes for VAB designs and ellipse for SPH ones. And yes, i know about hollow parts woes, i've seen part designers circumvent this issue with multiple meshes and colliders (like the hollow structural hub in B9's HX parts).

My old SSTO based on stock-aero model is basically a HUGE flying box capable of holding and carrying two orange tanks side by side with much space to spare. It was so large, it could carry my first designed SSTO inside without problem.

Edited November 8, 2014 by fatcargo
typo(s)

[fatcargo]

Your biggest problem is your craft is going to generate to much drag by itself, without having to contend with the added weight of the cargo.

I try to reply to everyone individually too, trying to touch on as many separate details as possible.

All cargo bays i've seen in KSP are linear, there are no "wide" or "flat" shaped ones.

Oh yes i almost forgot : i've seen Scott Manley's youtube videos commenting on "flying body" designs with FAR, but they seem to be for older FAR version(s). Has the situation improved ? Is it possible to make a lifting surface out of non-wing parts ? In videos i saw him use various parts and in the end he simply stuck a wing under a test craft body, so i see it as a failure to make a body from structural components that can generate lift.

[fatcargo]

If you're trying to build a craft that can lift 3 5m tanks into orbit, then I don't think any mods have parts that will be large and strong enough. You're better off trying to use procedural wings and tweak scale to try to get the parts larger, but it'll still be really hard. The wings are gong to have to be absolutely massive.

Yep, i'm still looking for super-sized parts. As for procedural wings, i was dissapointed with their performance vs B9's heavy wings (in my opinion, those are in stock aero model an undisputed kings of lifting force). A few KSP versions back, procedural wings gave me much grief during construction with their dodgy CoL and somewhat imprecise shaping options (for example, there is no option to force lateral (ie front/rear facing) edge to be exactly perpendicular to main craft axis). I'll give it another try, hoping that FAR will keep CoL properly placed.

[BudgetHedgehog]

You could always delete the relevant lines on the B9 cfg that nerfs the jets - it's what I've done, never been a fan of the B9 engines so I don't want the only engines I like to be weak compared to something that doesn't exist as I deleted the B9 engines except the SABREs. If you really wanted, you could delete the relevant lines in the FAR cfg that nerfs the stock jets too, but then they'd be extremely OP for the much thinner (or rather, much less soupy) atmosphere.

Seems easier than trying to design a cargo SSTO around that fact.

Anyway, an SSTO doesn't necessarily have to be reusable. But if you really do want it to be, have an open air cargo bay and make the payload as streamlined as possible. Say you need to take a huge 3.75m tank to orbit - make the 3.75m decoupler the root part and design a craft that has a big enough hole in the middle to hold the tank (imagine a tuning fork). Strut the back together and take her up. Make sure the craft is balanced both with and without the cargo as well, v. important.

EDIT: V simple example craft I threw together. It does fly, but only under RATO (courtesy of KWR). No idea if it can go to orbit though, I don't have the time to test right now. It probably doesn't have enough fuel, but it is stable and the CoM doesn't move very much.

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Edited November 8, 2014 by ObsessedWithKSP

[fatcargo]

You could always delete the relevant lines on the B9 cfg that nerfs the jets - it's what I've done, never been a fan of the B9 engines so I don't want the only engines I like to be weak compared to something that doesn't exist as I deleted the B9 engines except the SABREs. If you really wanted, you could delete the relevant lines in the FAR cfg that nerfs the stock jets too, but then they'd be extremely OP for the much thinner (or rather, much less soupy) atmosphere.

Seems easier than trying to design a cargo SSTO around that fact.

I too wanted to go that route but it's just killing me to do that because i also want to share the design. If anyone else used my craft with their unaltered B9/FAR there would be a nasty surprise.

Anyway, an SSTO doesn't necessarily have to be reusable. But if you really do want it to be, have an open air cargo bay and make the payload as streamlined as possible. Say you need to take a huge 3.75m tank to orbit - make the 3.75m decoupler the root part and design a craft that has a big enough hole in the middle to hold the tank (imagine a tuning fork). Strut the back together and take her up. Make sure the craft is balanced both with and without the cargo as well, v. important.

Hm you too arrived at the same solution as i did - a "flying box" closed with struts. My initial (very old) design was a catamaran-style (ie dual-fuselage) craft that later evolved into square frame (built from girders) with engines in back and wings/fuel tanks on sides. After that i tried adding more space/mass for payload by simply repeating that frame in two then three layers, with middle layer housing fuel tanks and engines. Part count sharply spiked to over 1300 parts, and my machine barely held it together during flight. When i tried to get even more payload space, length of girders was a limiting factor since too many parts lengthwise caused serious sagging/oscillation in middle. I wouldn't mind having 20m long girders.

Here is one example when i experimented with procedural wings and procedural tanks.

Next is another old craft using B9 (Was it back v0.23 ? Can't remember) and stock aero model.

You can see in center the Kerbodyne S3-14400 tank (about 80 tons) for size comparison. This thing could haul into orbit anything, from space probe to half-built space station. With this one i managed to assemble a 300t space station made of orange tanks. Each trip took 2 tanks at once + minor stuff like RCS fuel for tug fleet. Each tank was assembled into space station with four tug drones coupled to radially attached standard docking ports. After that i considered myself pretty much a docking expert.

And while on this older SSTO subject, please note a backbone "bridge" that both holds payload and adds rigidity to main body.

Now that i look back, these SSTOs are a design mess trying to balance out various problems. I may need to retire the idea of flying shoeboxes for good, sigh ... For now i'm tinkering with some other parts (i don't really care if some part is intended for a space station or a rover, if it can hold my SSTO craft together the way i want it, it will be included).

Edited November 8, 2014 by fatcargo

[Hodo]

I try to reply to everyone individually too, trying to touch on as many separate details as possible.

All cargo bays i've seen in KSP are linear, there are no "wide" or "flat" shaped ones.

Oh yes i almost forgot : i've seen Scott Manley's youtube videos commenting on "flying body" designs with FAR, but they seem to be for older FAR version(s). Has the situation improved ? Is it possible to make a lifting surface out of non-wing parts ? In videos i saw him use various parts and in the end he simply stuck a wing under a test craft body, so i see it as a failure to make a body from structural components that can generate lift.

Touhou Torpedo made a Mk3 wide body cargo bay a while ago, but it was never updated past .21. It worked until .24 but after that I cant tell you if it worked or not.

http://forum.kerbalspaceprogram.com/threads/29661-TT-s-Mod-Releases-Development-suspended-till-further-notice

I am not sure if I still have it anywhere on my computer at home, but I can look.

[Wanderfound]

I try to reply to everyone individually too, trying to touch on as many separate details as possible.

All cargo bays i've seen in KSP are linear, there are no "wide" or "flat" shaped ones.

Oh yes i almost forgot : i've seen Scott Manley's youtube videos commenting on "flying body" designs with FAR, but they seem to be for older FAR version(s). Has the situation improved ? Is it possible to make a lifting surface out of non-wing parts ? In videos i saw him use various parts and in the end he simply stuck a wing under a test craft body, so i see it as a failure to make a body from structural components that can generate lift.

Current Mk2 fuselages provide substantial body lift:

Most of the lift on that isn't coming from the wings.

[Hodo]

Current Mk2 fuselages provide substantial body lift:

http://i1378.photobucket.com/albums/ah120/craigmotbey/Kerbal/Challenges/Akademy%20Awards/Kerbodyne%20Dropbear/screenshot34_zps307d30fa.jpg

Most of the lift on that isn't coming from the wings.

As Ferram once said to me after one of my designs flew that I didn't think should. "If you get anything to go fast enough it will generate lift."

Actually that design has quite a bit of lift to it. You have quite a few wing on that craft without factoring the body itself. But the lifting body is helping.

[Wanderfound]

As Ferram once said to me after one of my designs flew that I didn't think should. "If you get anything to go fast enough it will generate lift."

Actually that design has quite a bit of lift to it. You have quite a few wing on that craft without factoring the body itself. But the lifting body is helping.

Yeah, it was just the first thing that came to hand. These might be a better examples:

[fatcargo]

Current Mk2 fuselages provide substantial body lift:

http://i1378.photobucket.com/albums/ah120/craigmotbey/Kerbal/Challenges/Akademy%20Awards/Kerbodyne%20Dropbear/screenshot34_zps307d30fa.jpg

Most of the lift on that isn't coming from the wings.

AAhh ok, now another (a more under-the-hood-of-game-engine) question : does part need to have a defined lifting factor for FAR to include it into overall lift force calculations ? For example structural panels don't have lifting factor but a Mk2 fuselage does.

I just need a concrete answer like "yes, structural panels can generate lift".

Edited November 8, 2014 by fatcargo

[Tex_NL]

I just need a concrete answer like "yes, structural panels can generate lift".

As Ferram once said to me after one of my designs flew that I didn't think should. "If you get anything to go fast enough it will generate lift."

With FAR/NEAR yes. Stock no.

[Jimbimbibble]

Here's an example of a heavy lifter you can try (with craft file). I entered it in Wanderfound's spaceplane challenge recently.

http://forum.kerbalspaceprogram.com/threads/93779-SSTO-Spaceplane-Airplane-Design-Contest-II-Akademy-Awards?p=1506865&viewfull=1#post1506865

You should also check out the other competitors. There are some pretty good spaceplanes that have been entered. Here's the link to the first page of that thread.

http://forum.kerbalspaceprogram.com/threads/93779-SSTO-Spaceplane-Airplane-Design-Contest-II-Akademy-Awards

[Hodo]

With FAR/NEAR yes. Stock no.

He is using FAR/NEAR.

[Wanderfound]

AAhh ok, now another (a more under-the-hood-of-game-engine) question : does part need to have a defined lifting factor for FAR to include it into overall lift force calculations ? For example structural panels don't have lifting factor but a Mk2 fuselage does.

I just need a concrete answer like "yes, structural panels can generate lift".

Go test it; make a basic plane, then remake it with some wing bits replaced with structural panels. Look at the aero analysis screens, then test-fly and compare. Turn on the FAR lift/stall/drag visualisation toggles while flying and look.

For the FAR visualisation tools in action (as well as some other mods), see

[fatcargo]

I wanted to hold off new SSTO craft i made today until i made certain it could complete takeoff, orbit and landing. Problem is i could not land it due to high dynamic pressures from too much speed (goes kaboom in mid air).

I made it by trial and error, on a "feel". It is severely undersized, all parts in main body are tweakscaled to 0.625m, but main "wings" are 200% oversized Advanced Canards. Whole thing weighs about 1.6 tons.

It can carry 1 astronaut, has a probe core for unmanned flight so its kind of single seater "taxi" to/from LKO.

Flight profile is :

0m = unstable on takeoff, must take care not to flip over, i even re-tweaked the probe core back to 0.5kN torque to keep it from excess wobble

0m-6km = roll and yaw instalabilites and sideslips, you can drive it into minor stalls, do not go over 250m/s in lower atmo, slowly increase AoA to 45deg, throttle up gradually to max

6km-21km = slowly lower AoA to about 10deg, pickup speed

21km-31km = just keep piling up speed, sabre will start to cough on leftover air and drop thrust to meager <10kN, situation starts to look quite bleak

31km = switch sabre to rocket mode and point to 20deg above horizon, it will start to eat through oxidizer like a piranha, BUT PAY ATTENTION TO APOAPSIS ! AP can easily jump to 300km, this thing just shoots out of atmo like a bullet, doing Mach 7.5 like it's dull rainy thursday afternoon

somewhere after 31km = turn off sabre, wait to escape atmo, circularize as usual

To summarize : looks can be deceiving, in lower atmo its tame and unsecure, but once it goes over 30km its inner speed demon comes out.

Preliminary pics until more testing and design are done.

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Edited November 9, 2014 by fatcargo