My First Successful Attempt At An SSTO (3 Ton Capacity). Any Suggestions?

[MinorInconvenience]

This is my only successuly SSTO in 1.0.2. Can get 3 tons to orbit and come home (barely, but that is probably my fault as I am a bad pilot). Suggestions and commentary welcome.

The craft file:

https://www.dropbox.com/s/2c2gd1w7hc0jbnb/KR-72%20Kenture%20Star.craft?dl=0

[Version 2 is on page 2... much better...]

Edited May 5, 2015 by MinorInconvenience
1st: fixing typos. 2nd: noting changes on page 2.]

[Starwhip]

What's your flight profile like? For Rapier engines, you should fly level between 5,000 and 10,000 meters until you break the sound barrier, then start ascending again.

Or so I've heard, can't play 1.0.2 yet.

[MinorInconvenience]

That's about right. I ascend to 12k at about 30 degrees or so. Am about Mach 1 by then. Then I level out and slowly make my way to 20k. Usually about Mach 4.5. Then I switch over to rockets to orbit.

[Starwhip]

Sounds just about perfect!

[GusTurbo]

And people say that you can't make good looking spaceplanes in 1.02! This looks great!

[Mastikator]

Beautiful plane, but I tried it and it's really hard to steer, it flips over like crazy. I was gonna add a nuclear engine in place of the clamp-o-tron and do a flyby of the mun and maybe even flyby to minimus but I can barely get 10km without flipping.

[Redshift OTF]

It looks awesome! However the looks my be affecting performance. Wings create a lot of drag now and the Mk2 parts will probably create enough lift that you don't need wings.

[MinorInconvenience]

Beautiful plane, but I tried it and it's really hard to steer, it flips over like crazy. I was gonna add a nuclear engine in place of the clamp-o-tron and do a flyby of the mun and maybe even flyby to minimus but I can barely get 10km without flipping.

As designed, the center of mass is only a hair in front of the center of lift/pressure unloaded. With a nuke back there, I'm sure the CoM flips behind the CoL. Maybe try removing the front canard and setting both control surfaces on the large delta to pitch.

I never fly it without SAS, but don't have trouble with flipping when I do.

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It looks awesome! However the looks my be affecting performance. Wings create a lot of drag now and the Mk2 parts will probably create enough lift that you don't need wings.

I guess I'm just a slave to fashion... Seriously, however, I was under the impression that large wing surfaces help you stay in the high-altitude sweet spot where you build up to Mach 4+ before lighting the rockets for the final ascent?

[Redshift OTF]

You get an advantage by being able to shallow out a bit more but the drag on the wings is massive in this current version of the game.

[eddiew]

I guess I'm just a slave to fashion... Seriously, however, I was under the impression that large wing surfaces help you stay in the high-altitude sweet spot where you build up to Mach 4+ before lighting the rockets for the final ascent?

I think you've done exactly right to have the large wing area you've gone for. Wing drag increased in 1.0.1, but wing lift increased more so the l/d is now preferable to before. The more wing you have, the nearer to horizontal you can be while still remaining level, so the more thrust you can get out of your jets, so the sooner you go to space I've experimented with tiny wings in 1.0.2 and they simply don't work. The way that jet thrust is so tied to your angle above the horizon will cripple planes with smaller wings.

If I had any advice, it would be to choose what this bird is for. You list a cargo capacity, but it has a crew cabin. If it's a crew transporter, does it need 3T in the bay as well? If it's a lifter, you can add 2.5T capacity by dumping the crew tank. A 5.5T lifter is pretty good going under current stock, so I'd be inclined to remodel and specialise one way or the other. Or just have two variants for different missions

You also have the option to move the nacelles forward to solve your CoM vs CoL issues, since none of the jets are on a level with the wings anyway. Deciding on a single rear delta wing, or a mid-wing with a tail, will result in a clearer design plan and sort out your balance issues

[MinorInconvenience]

I think you've done exactly right to have the large wing area you've gone for. Wing drag increased in 1.0.1, but wing lift increased more so the l/d is now preferable to before. The more wing you have, the nearer to horizontal you can be while still remaining level, so the more thrust you can get out of your jets, so the sooner you go to space I've experimented with tiny wings in 1.0.2 and they simply don't work. The way that jet thrust is so tied to your angle above the horizon will cripple planes with smaller wings.

If I had any advice, it would be to choose what this bird is for. You list a cargo capacity, but it has a crew cabin. If it's a crew transporter, does it need 3T in the bay as well? If it's a lifter, you can add 2.5T capacity by dumping the crew tank. A 5.5T lifter is pretty good going under current stock, so I'd be inclined to remodel and specialise one way or the other. Or just have two variants for different missions

You also have the option to move the nacelles forward to solve your CoM vs CoL issues, since none of the jets are on a level with the wings anyway. Deciding on a single rear delta wing, or a mid-wing with a tail, will result in a clearer design plan and sort out your balance issues

I figured someone would call me out on the jack-of-all-trades design (like the US Space Shuttle, really). I think I'm going to fiddle with this tonight based upon your suggestions. Thanks.

[MinorInconvenience]

Okay. I really tried to take eddiew's advice, however, Betty and Veronica (the "crew" and "cargo" versions I was developing) just didn't seem right to me... so I adjusted the original spaceplane and was able to get over 4.5 tonnes up plus the crew cabin (six Kerbals in all). This is the story of our nerve-racking mission:

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And the craft file of the new and improved KR-72A!: https://www.dropbox.com/s/w3ip5inpllvn8n1/KR-72A%20Kenture%20Star.craft?dl=0

Comments, criticisms, and such so very welcome!! (And I'm still trying to take eddiew's advice and make single purpose vehicles. I'm just a little stubborn and a slave to appearances... [My main problems with "Betty" and "Veronica" were that I had to get ride of the leading canard... and I so love the Su-33 "look"]).

[Tada]

Thats very, very, very nice! Looks just like something I was trying to make but failed Does it have docking port?

[eddiew]

Heh, well done on optimising it a bit It's rarely a bad thing to be able to carry a pilot, engineer, and scientist all at the same time - and you now know what to do if you need a 7 ton cargo lifting

[Rune]

Probably better to comment on it here...

Well, with that reference, you at least get a comment from me

It looks pretty, that's for sure, but there's no craft that can't benefit from a critical look, so... maybe a bit less thrust? As long as you can break Mach 1 at 10kms, you are fine, and each RAPIER you take out is a couple tons extra payload. I'm thinking maybe three could be enough for that weight class (my White Dart 1.0 is probably overpowered too by at least 25%).

Other than that, the control surfaces on the wings look to be really close to the CoM. Use them only for roll control, since they won't add much pitch torque and they will steal lift and increase drag when they try to pitch you up. Or just make the wing bigger and take them out, to get enough roll authority you can usually make do with the pod's reaction wheels. If you are lacking pitch authority (doubtful, the new aero system lets you get away with very little), canards should work wonders in a tail-heavy design like that one, and you can sink them into the cockpit for a flush look, that still works like before (occlusion is only done for stuff inside cargo bays and/or connected by nodes).

Rune. Hope that helps for the next one!

[MinorInconvenience]

One thing I am still struggling with is the ascent profile. In fact, I'm not quite sure how much better the second version is from the first. I might have just lucked out on the ascent--getting to that sweet, sweet spot (a touch over mach 1, altitude between 12k-14, and a very low angle of attack) where the RAPIERs just start running away. Right now I am trying to figure out if a more gentle ascent where I am already going Mach 1 as I hit 12k is best or if a steep climb to 14k-15k at subsonic speeds and then diving to break the sound barrier is better. Anyone have any thoughts?

[FlipNascar]

If you're not diving to hit Mach 1, you're not carrying enough payload?

[MinorInconvenience]

If you're not diving to hit Mach 1, you're not carrying enough payload?

I have thought of that, but I wonder if the extra fuel needed to go up, come down and go up again offsets any gains in payload as compared to just go up...

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Thats very, very, very nice! Looks just like something I was trying to make but failed Does it have docking port?

Two. One inline on top and one centerline rear (I have considered making this the "command module" of an eventual "grand tour" craft).

[FlipNascar]

I think it's more a case of what does it "cost" to add another Rapier... a) the weight of the Rapier and the LF & O additionally required... Can that be negated by adding an extra few units of LF and diving to push past the barrier... I don't know.

It's exactly this issue I'm trying to solve with my Porca... And perhaps time will tell and as we as the playerbase do more experimentation we'll have a more definitive answer. But at this stage, it seems fair to say that yes, it may well be favourable to do a short dive and take up an extra 1t-2t (?), than go through the hassle of adding an extra engine and the ancillary parts that that requires.

[MinorInconvenience]

With a better ascent profile (and some cheaty clipping), I now have an SSTO that can get 6 tons to orbit (76 x 76) with about 300 m/s left for manuevers while still retaining the same form (10.6% payload fraction... not including the 4 passengers it can take). I like this new aero...

I think this is the maximum I can do without adding engines (which would be even more cheaty). Thoughts?

Craft file: https://www.dropbox.com/s/mw6hzbv1z3yso10/KR-72.craft?dl=0 (All stock. Mechjeb and Protractor parts removed.)

Edited May 7, 2015 by MinorInconvenience
I always notice typos after posting....

[MinorInconvenience]

Smaller (Slightly) but just as good:

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Craft file: https://www.dropbox.com/s/jrxmbnmqlgi9jcj/XK-39%20Kangel%20One.craft?dl=0

Always refining. Thoughts? (I know it is a jack-of-all-trades master of none. Science + Cargo + Passangers.)