Big Spaceplanes: Show me your biggest

[mattihase]

I'm trying to build a large scale cargo SSTO at the moment but my struts keep on getting sent to the cornfield. While I'm waiting for the game to unbreak itself, It'd be cool to see what everyone else has been able to throw together on the large side of things.

• What's the biggest thing you've managed to get off the runway and in to space?
• What's the heaviest payload it's carried?
• Single Stage, or assisted in some way?
• Have you build anything cool in orbit with it, space shuttle style?

I'd love to see what cool designs are out there.

[Socraticat]

 

I took a trip to laythe in a thing I called the "Pontoon". It carried another SSTO on it that is also Kerbin Capable. That cargo SSTO carried a "OneOscar" SG model.

[Jason_25]

You should build basically one piece at a time and see if it explodes after adding every piece.  Once you have enough fuselage pieces add some landing gear and send it down the runway without wings.  Then add wings and do a series of high speed taxi tests.  That is kind of the only way for large planes right now.   You cannot just build it all at once and then tweak a few things after a few tests like with KSP 1.  After several hundred or thousand iterations you will then have a flying example.  With that said, I am working on another flying wing that is as wide as the runway.

[Socraticat]

1 hour ago, Jason_25 said:

You cannot just build it all at once and then tweak a few things after a few tests like with KSP 1

I can't disagree with you more. You absolutely can. Especially after the latest update.

The craft I shared above was built before 0.1.2, and Rapiers were still bugged at the time (wouldn't reactivate after reaching vacuum).

[Jason_25]

This thread is about big spaceplanes though.  Of course you can build something small and have it work first time.  This is the intended way and what the developers have tested for. 

But for big spaceplanes, I just tried to build one without cheats and wings were 80 tons a piece causing the vehicle to fail instantly.  Also I was needing to make numerous strut connections between the "350" series hydrogen tanks before they would randomly stop exploding.  This is much more punitive than KSP 1 though it may be due to the weight of the parts being higher than typically used in KSP 1.  Modding the density of the wings cured the first problem and trial and error strut additions cured the second problem.  I am still faced with the standard "large space plane falls apart right at V1" but that is to be expected and something that we faced in KSP 1 and is going to require more careful wing strut additions and possibly control surface tweaks.  Each large vehicle in this game takes me at least 50 hours but I am trying to do this one in less than 20 hours.

[Socraticat]

29 minutes ago, Jason_25 said:

I just tried to build one without cheats and wings were 80 tons a piece causing the vehicle to fail

You tried and failed, and then you tweaked. You were able to do the thing, it's just not to your expectations. 

What do you consider to be large? Why do you need 80 ton wings? Are you willing to post your failure for criticism? How are we to believe it's game error and not user error? I help at least one person a week who admits they didn't know the game as well as they thought. I'm not saying this is you... but would you be willing to share your work? I'm curious how you "broke" the game.

Of course large planes take longer, they should. Yeah, it should be faster to get to your final iteration in 1.0, but saying you can't "just build" an SSTO and have it work is a bit of a stretch.

Every craft has it's own challenges. Add to that KSP2 will always feel different than KSP1. You can build a large SSTO and have it work. Especially if you know the parts and game well (that is to say you know it well enough in its current state).

The bigger issue for me is large vessels and the part lag. At 400 parts, doesn't matter what parts they are for me, the game starts to lag seriously; every iteration from that point (for now in Early Access) is an effort in trying to make the best choices to reduce the number of iterations before launch. It just takes too long.

[Jason_25]

I will try and post a screenshot on this thread when I am finished.  I do not like to post half-built or broken things.  Further, I have not posted the "cheatbirds" craft files in the past because they require mods to function correctly.  My mods edit the game files directly and those cannot be ethically posted so I would need to direct someone on modding the files manually which I do not mind doing.

Good question on why I need 80 ton wings - why are the default wings that heavy?  Every time I try to make a "large" wing larger than you can make with the "small" wing they turn out very heavy.  Though like I said modding the density was the key.  I tried to keep the game balance the same by modding the density of the small wings also but their initial weight is kept lower.  Now the same large wings weigh about 6-7 tons.

As far as failing, by that standard everything I have made is a failure.  I have a certain visual standard and look that I go for that as just as important as anything else.  In terms of performance I also push for 50k DV but I have had to settle for less since we have such bad technology right now.  For instance this Thunderbird Bomber with wings as wide as the runway has 33K DV (modded).  You only need like 3K DV to qualify for SSTO status.

On the subject of struts that is a tradeoff you make when you spend less time building a creation.  Sometimes less struts is better than more struts.  When you focus time on deciding exactly which strut is necessary or not you can trim the design down.  I cannot imagine a 400 part design could not afford to lose a strut here or there.  This Thunderbird Bomber is around 80 tons dry and 220 full with just around 160 parts and is quite huge.

I have completed some initial flight and orbital tests for this bomber.  I am now proceeding to make a multi mission module for the rear of the bomber that will hold extra fuel and engines for a vertical launch.  Then will come integration of 2 probe units and the vehicle will officially become a mission and go off to Jool.  The mothership bomber should have plenty of fuel to dip down into Laythe's atmoshere and look around for itself if necessary.

Since I have wrote an essay already I will include some thoughts I had while building this bomber.  Sometimes the wing control surfaces are worth very little.  The amount of flex and vehicle destruction they were causing was remarkable with this flying wing design.  I have resorted to setting the outer wing controls to be toggleable to allow more control at lower speeds and to be turned off near max-q to keep from destroying the vehicle.  I was having to make a gross tradeoff between vehicle stability and vehicle maneuverability.  It seemed an infinite number of struts was going to be required until I did the aforementioned toggle and limited the main inner wing to 7.5% authority, and added 10-20 of the largest SAS units from 0 before.  These SAS units thankfully took some of the wing loading off the vehicle making the partially SAS-induced aeroelastic flutter hopefully manageable.  I am also using modded small nuclear engines which lack gimbals making the previous issues with wing loading worse.  The woes of truly large vehicles.  It was however good to see no need to invert any flight controls this time either.

After thinking about it I suppose a large craft could be made with 5 tries or less.  Cockpit, fuel tank, large wings with struts top and bottom and engines balanced with weight and aero and of course landing gear.  That would be a challenge all in itself but I do not make ugly stuff so am not interested personally.  Would they be able to place just the right amount of struts at just the right place?

[Socraticat]

I am so curious to see what kind of craft you like to make in Kerbal.

On 7/5/2023 at 2:19 PM, Jason_25 said:

After thinking about it I suppose a large craft could be made with 5 tries or less. 

There ya go. It might not have all the parts you want or look exactly how you want it, but it's absolutely possible. 

This is not an SSTO, but it's the widest I've made in game. It took off on first launch:

Very few parts here. I think this was 0.1.0

[mattihase]

On 7/4/2023 at 9:39 PM, Socraticat said:

I took a trip to laythe in a thing I called the "Pontoon".

Oh that thing is delightfully industrial.

[Gummel]

The biggest thing I ever launched into space was my Kerbal mothership. This was launched fully fueled and in one piece into orbit. The total weight, without launch stage, is 505 tons.

The mothership has got almost 10000 delta v, so it can travel far into space without refueling.

All the different docking ports allow me to ad different landers and modules to send my Kerbals on different missions.

[Siska]

On 7/10/2023 at 8:50 PM, Gummel said:

The biggest thing I ever launched into space was my Kerbal mothership. This was launched fully fueled and in one piece into orbit. The total weight, without launch stage, is 505 tons.

The mothership has got almost 10000 delta v, so it can travel far into space without refueling.

All the different docking ports allow me to ad different landers and modules to send my Kerbals on different missions.

and how many parts if i can ask? weight is not a problem, parts no. is.

Making big planes and sstos is really frustrating. After the latest patch you are actually able to make a mk3 craft that it stays together. But still, aerodinamycs can break it almost instantly after takeoff. 

As far as i see it, you can do it with unbreakable joints only. 

Before last patch, mk3 wings just fell of the fuselage on runway every single time. like nobody would even test bigger plane parts before releasing.

[Gummel]

Hi Siska,

I checked my build and parameters are as follows:

Mothership and launch stage

parts: 539 pieces

total mass 1862,79 t

 

I play KSP 2 in the current patch version, no mods installed and structural rigidity unchanged. No settings like unbreakable joints activated.

After the latest patch came out I launched this ship into Orbit again and it worked fine. Nothing broke, no part fell off.