Entente Heavy SpaceLifter (B9 HL Chassis)

[aphenine]

Um, so, ever since I got KSP I've been mainly interested in building spaceplanes. They're supposed to be the path of the future and, if we're ever to get out there into space, supposedly we'll need them as the stage between rockets and the space elevator, or at least, that appears to be the consensus in sci-fi.

Anyway, I've been playing around in KSP trying to build different versions of spaceplanes based on existing designs, to see how they would work and what's necessary to get a good spaceplane design. FAR has certainly made my life difficult, if instructive and I have decided that aerodynamics is officially evil. I've been looking around the forums drawing a little bit of inspiration from other people's designs and I thought that I'd post one that I haven't seen around the forums, which isn't to say it doesn't exist.

Entente

Inspiration:

Concorde: https://en.wikipedia.org/wiki/Concorde

The name comes from the squabble over Concorde's name. The English changed the name to the English spelling, Concord, over a perceived slight, but the science minister changed it back to the French, with the nationalist uproar dying down when he stated that the suffixed 'e' represented "Excellence, England, Europe and Entente (Cordiale)."

Stats:

Cargo Bay: 32m length

Max Rated Cargo Weight (to LKO): 95 tons (probably could do 100, but someone braver than me can try that, 95 was struggle enough)

Craft Weight: 276 tons

History:

I was trying to make a fuel tanker based on some successful delta-winged designs I'd made with a 16m cargo bay. Unfortunately, because fuel is very dense, the spaceplane wasn't long enough and the thing had not enough wing area, leading it to fall out of the sky at 10,000m, as well as not having enough mounting space for engines.

Initially, I tried to compensate by adding in structural sections in between the fuel tanks, giving me a longer design than I was used to, so I could have bigger wings and more lift. So I went looking for inspiration and realised Concorde had the same long slender body, so I could use the same wing plan as an inspiration for my design. Unfortunately, I couldn't build the right wing plan using the traditional parts from B9, but then I discovered Procedural Wings. The tanker was too heavy to ever fly, but I realised if I replaced the tanks with cargo space, I'd have an awesome cargo-lifter.

Craft:

https://www.dropbox.com/s/pjkunifucj4b0k2/HL%20Entente%20V1_1%28Cargo%20Lifter%29.craft

Mods required: B9 Spaceplane, Procedural Wings, MechJeb

Slight warning: It's a bit big, so it might stress older machines. Mine's about average and it struggles a bit when it's fully loaded.

Characteristics:

The nicest thing about this vehicle is the massive cargo capacity and the very stable flight and low drag at very high velocity and altitude. Unfortunately, this is belied by the thing's absolutely dismal low-altitude handling. It bucks and it drops like crazy. Apparently, Concorde had the same problem and they fixed it by using a phenomenon with delta wings, which involves a vortex happening at high angle of attack. This is why Concorde has the really insanely high front landing gear. This effect does seem to be modelled in the game. This spaceplane takes off at about 40m/s less than a similar but much more stable design I tried, and will hold well if held at an angle of attack through the whole lower atmosphere. Otherwise, though, I have to use flaps to land the thing along with full engines, as the drag seems to make the thing more stable.

In space, it's not very manoeuvrable and expends a lot of monopropellant. It has enough to rendezvous with a station if you want it and then come down. However, it's not really meant to be manoeuvrable and it's easy enough to push its cargo into orbit and then let a tug push the cargo where it is supposed to be. I haven't checked what orbits it can achieve, but it gets to 360,000km pretty comfortably with fuel to spare.

Flight Profile:

Take off: Take off speed is about 160m/s empty and it only goes up significantly if you really fill the cargo bay. It has a tendency to tail strike, so it's worth being careful on lift-off. If it's lightly loaded or empty, the engines are grossly over-powered, so be very careful of hitting high dynamic pressure. This happens almost immediately after take off, so the engines need to be throttled back, often to 30% if empty. 20-30 degrees lift is good for the first 10,000m, then reducing to 10 for the rest. Engines need to switch below 26,000 from air-breathing to rocket, although in practise it's rare to get the thing above 22,000m on air-breathing with any load, as the engines loose too much power and start to overheat.

Space: The big rocket engines cannot handle full rocket thrust for any length of time. Manually limiting them after take-off is a must whenever I've done any MechJeb manoeuvres. 66.5 works well.

Landing: The awesome high-altitude characteristics and it's sharp ballistic profile make re-entry a joy in this thing. The steeper the better, and use the flaps to bleed off velocity. Then pull up when you've had enough plummeting through the atmosphere like a dropped stone. Unfortunately, this is balanced by it's absolutely dismal low-altitude handling. I could never get the whole thing to fly well at low altitude and the only way I can land the thing is by using the rear wing flaps (key 5), landing gear and the engines on full power. The increased drag seems to increase the stability of the flight and allows a successful coast over the runway. Adding the full flaps and bleeding off the power allows it to be brought in. I have landed it in one piece once using the keyboard, otherwise I tend to take the bottom engines out. I'm sure that could be fixed with a few extra wheels, but meh.

Keys:

1 - Switch Air-breathing/Rocket mode on the SABRE engines.

2 - Toggle cargo bay

3 - Toggle all flaps

4 - Toggle front flaps

5 - Toggle read flaps

6 - Toggle solar panels

7 - Toggle cargo bay lights

[AmpsterMan]

AMAZING craft dude! Thanks for sharing; I personally don't like using mods but for those that do, this thing would be great!

[Hodo]

I could give you some tips on the design. But I will start by saying it is an excellent design to start with and hard to improve on.

The things I would change is your landing gear layout, it looks like you have to many and they will impede your ability to rotate and get off the ground without running off the end of the runway.

You have more than enough power to get over 100 tons to space, your problem is mainly the way the added mass changes your CoM relation with your CoL.

I would also move the SABRE-S's on the top of the wings further back so they are not burning through your control surfaces as you use them.

Last thing I would do is add a pair of nuke engines to handle the orbital burn and orbital maneuvering, you don't need a high TWR in space just enough to get you around without burning through all your fuel.

I have built a few heavy lift SSTO space planes in FAR, and I have 2 that work quite well at moving 108 tons to space, one of them is only limited by cargo space.

[Voculus]

For anyone who has tried to build a very large SSTO, they will know what a difficult feat it is to pull off, and how awesome this ship is. Nicely done!

[aphenine]

Thank you AmsterMan, and thank you Voculus

Also thank you Hodo.

The things I would change is your landing gear layout, it looks like you have to many and they will impede your ability to rotate and get off the ground without running off the end of the runway.

The landing gear design isn't optimal, no. Unfortunately, it's the only way to spread the load enough. I wish there was some mod that created landing wheels in different sizes and shapes, but I haven't found one yet. However, if I went for a more traditional layout, this would create a lot of load on the runway. I know that KSP doesn't care about it, but I remember reading how the Skylon, a lighter craft with a traditional 3-gear system, has to have a reinforced runway to take off from with a 40 ton load. The Entente should not have this problem and should land and take-off on a commercial runway, which is good and important to me. I did experiment briefly, in another design, with playing with the steering on such a arrangement, getting the rear wheels to have their steering reversed and having the middle wheels respond to controls less than the front ones, much like lorries are designed to do and it was viable, although I don't know if it was practical.

Running off the runway strangely doesn't seem to be a problem and it is one of the better craft I've designed for travelling down and getting off the runway. I didn't think it would either and I don't know why. I think it might be that the nose canards. They have a permanent 5 degree angle of attack. So this might be enough to pull the nose up and then activate the delta-wing effect. But I would not swear to this.

You have more than enough power to get over 100 tons to space, your problem is mainly the way the added mass changes your CoM relation with your CoL.

Hmmm... I'd noticed the load moved my CoM forwards and that messed with the CoM/CoL arrangement, making the craft less responsive to pitch control. I had just written it off, but you might be right. *goes off and thinks* Thank you.

I would also move the SABRE-S's on the top of the wings further back so they are not burning through your control surfaces as you use them.

*Is guilty* That's my one major worry about the reasonableness of this craft and you noticed that. The game doesn't seem to mind at the moment.

Last thing I would do is add a pair of nuke engines to handle the orbital burn and orbital maneuvering, you don't need a high TWR in space just enough to get you around without burning through all your fuel.

I've never used nuclear engines. Why would I use them here? As you say, TWR doesn't have to be high in space and the craft works fine as it is, plus putting extra weight on there that I can't use is wasteful. So what's the benefit?

I have built a few heavy lift SSTO space planes in FAR, and I have 2 that work quite well at moving 108 tons to space, one of them is only limited by cargo space.

Yey! Awesome! Any pictures?

[Hodo]

I've never used nuclear engines. Why would I use them here? As you say, TWR doesn't have to be high in space and the craft works fine as it is, plus putting extra weight on there that I can't use is wasteful. So what's the benefit?

Yey! Awesome! Any pictures?

SP-409

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SP-406

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I use the nukes as manuevering rockets in space to cut down on the fuel needed.

As for your take off issues, you don't need to add more canards or angle them, the problem is your landing gear is keeping your nose from coming up. When you are pulling up to get the nose up it is pushing the rear landing gear down and keeping them from rotating propperly. I found that if you place your furthest back landing gear just before your CoL and just behind the CoM, the craft will rotate pretty well.

[aphenine]

Oh, wow, I recognise that craft. I saw it before on the forums and thought wow. I think I've seen some of your earlier designs too, back when I started my first HL chassis cargo lifter, because I think these are new, right? I think I had come up with something similar at the time, although I hadn't quite worked out a lot of things yet (it was my first craft with FAR and I was till getting over the fact that my lovely AN-225 style wings had peeled straight off at Mach 1), and it really helped to see a design that worked from someone else that was similar but more polished. It inspired me a lot! If you don't mind me asking, what did you use to create the black fuselage on the 2.5M nacelles? I've been using the 2.5m KWRocketry tanks in a similar nacelle-driven design and they don't look quite right, but those look awesome and I've been dying to know since I've seen it. Oh, wait, you'll have posted the .craft files. My bad. I'll go find them, I think I know where. Sorry. But thank you for commenting on my craft. That's awesome.

About the landing wheels. I know what you're trying to say. I know that you're right. I'm just trying to say that, despite that problem, it still lifts at 160m/s really well, even with the pivot effect. I have had other craft with the same wheel layout design and they do have the problem you describe, but not this one. Also, I created a similar craft but using a Blended Wing design. Because it was so easy to mount lots of landing gear, I could put them in straight lines clustered around the CoM as you said without buckling. Despite this, it still lifted at 200m/s. It was the most stable craft I ever sent down a runway, and took off the best, but still.... 40m/s faster take-off speed unloaded. I do not understand it at all...

[Hodo]

Oh, wow, I recognise that craft. I saw it before on the forums and thought wow. I think I've seen some of your earlier designs too, back when I started my first HL chassis cargo lifter, because I think these are new, right? I think I had come up with something similar at the time, although I hadn't quite worked out a lot of things yet (it was my first craft with FAR and I was till getting over the fact that my lovely AN-225 style wings had peeled straight off at Mach 1), and it really helped to see a design that worked from someone else that was similar but more polished. It inspired me a lot! If you don't mind me asking, what did you use to create the black fuselage on the 2.5M nacelles? I've been using the 2.5m KWRocketry tanks in a similar nacelle-driven design and they don't look quite right, but those look awesome and I've been dying to know since I've seen it. Oh, wait, you'll have posted the .craft files.

The black 2.5m fuel tanks on the SP-406 are from Stretchy Fuel tanks later Procedural Fuel tanks. It was a way to cut down on parts count. The craft file for the 406 is still out there but I am not sure how well it works now due to updates to procedural wings. Last time I loaded it, it gave me paper thin wings that I couldn't remove or adjust the size on. I have been tempted to recreate it because it was my best heavy lifter. But thats why the SP-409 came about, I haven't released its craft file yet, I am still tweaking and fine tuning it. I have big plans for it, and it is going to do most of my lifting duties in my current career mode and in .24.

But the SP-406 is my original 100+ ton lifter, I used it for quite a few things previously. Everything from moving 3 orange tanks to my space station for station refueling, to launching one of my interplanetary ships, and building a space station in orbit for a challenge. ((Which I did quite well at and could have taken the top spot if I had been so inclined to keep sending it up with fuel tanks. Something I could have done indefinately. But I achieved my goal of topping out over a certain person.))

The SP-409 is my current 100+ ton lifter, and it is going through its trial run right now, I am slowly tweaking, and fine tuning the design. It is currently experiencing a serrious case of "Mach Tuck" at mach 1. I have mostly fixed the problem, but I am still working on it. I also added some new features to the SP-409 which has become standard on all my vessels, and that is a crew escape system, to save the crew of the vessel incase of emergancy.

But feel free to ask me any questions, and I am highly honored that one of my designs inspired you to build this wonderful craft.