SSTO lifting a 7.7 ton payload to orbit [load o' pics]

[katateochi]

So after my first successful SSTO that could take a single kerbal to orbit I've been trying to make one that could actually do something useful, rather than just be a joyride for one Kerbal. I've been making a shuttle like thing that can lift a payload up to orbit and then return and last night (late last night) I managed to get a 7.7 ton payload to a 70km orbit!! So pleased!!

Here she is sitting in a (ruffly) 70km orbit;

It runs on 6 turbo jet engines, 10 ram intakes and 2 LF-A30 liquid fuel aerospikes as its rockets. Its wings are in 3 layers (so kind of a tri-plane) which does give it more lift, the single layered wing didn't cut it and wider wings became ungainly.

The craft (with 7.72ton payload) is 85.5tons. With that payload I can make a 70km orbit and have (just) enough fuel left to de-orbit and fly to the landing strip.

The mods used are TT's wheels, KAS, quantum struts and dammed robotics for hinges. It also has the TAC fuel balancer, but that is mostly for observing the fuel levels. I've now got the plumbing set to make the tanks drain in the order I want.

Oh and MechJeb (he says with hesitation for fear of being misunderstood/shouted at). I use it for info (as I don't use map mode during ascent/circularizing) and the SURF function and that is all. I'm getting RSI from flying planes manually! The SURF just allows a heading and (most importantly) a pitch to be set, but its my choice of heading and pitch, no auto piloting here! The engines, tanks, wings and control surfaces are all stock. Thou I will probably change some tanks for KW or NP tanks now, just to reduce part count.

The 6 turbo jets engines take it up to about 24km. The second I reach the point of flame out (just shortly after above right pic) I engage the 2 rocket engines and shut down the outer pair of turbo jets. Then the other 4 jets can stay on longer. When they start to flame out the next pair is shut down so it's on just the rockets and the 2 inner jet engines. Finally when there is no more air the last 2 jet engines are shut down and then its up to the rockets.

Getting up to speed before firing the rockets is important, I could climb to 24km in less time but be going slower, however that doesn't work out. I climb steeply (40-45 degrees) to about 18km, then start to level off and pick up speed. I keep adjusting the pitch to climb gradually and gain speed. The speed increase rams more air into the intakes so I can climb higher before firing up the rockets (when doing about 1200m/s) and this seems to be key to getting this flying bus of a craft into orbit.

By the time my AP is at 70, the PE is about -80 to -100 so it doesn't take much to circularize the orbit.

Now to release the payload; The cargo bay doors open to reveal the test payload; A small rocket.

Jeb then attaches KAS lines to the payload before it is released (and is generally just Jeb - grinning maniacly at stuff and looking cool)

One KAS line is used to hold the payload, the other is for Jeb to grab hold of so he can be (unceremoniously) yanked back to the main ship.

I want to use this to bring things down from orbit too. But not everything has the small docking port, so a larger one (attached via a hinge) can be folded up to cover the small one.

Once I'd released this test payload I had just enough fuel to de-orbit. After the de-orbit burn I had about 30l of oxidiser and 120l of liquid fuel left, just enough!

Darkness in space is one thing, darkness when getting near to the surface is something else altogether. Thankfully a crashed craft near the runway gave me a point to head towards.

But I came in to high and had to pitch down hard, almost lost control and nose dived towards the runway, but thankfullly I manged to level out, cut engines and glide in.

It was my most harrowing landing, mostly because it was dark, but its not an easy craft to keep level when empty. It wants to pitch up a lot, but then if I push the nose down a bit too hard it will suddenly go into a sharp dive.

Incase your wondering what the other stages are on this SSTO; stage 3 is the main engines, stages 2 and 1 are the emergency eject system and 0 is a set of radial liquid boosters mounted at the front, used to lift the nose up during take off. They are activated with an action key, but are on a different stage to keep them out of MJ's dV output for the main stage.

An eject system is more important on my planes than on my rockets, says something about my piloting skills!

It still needs some refinement, and as you can see from the size of the cargo bay, I'd hoped to be able to take more weight up with it. 7.7 tons is only just about useful, really needs to be able to carry more and ideally get a higher orbit. I think I'm pushing a boundary of fuel to weight with this design. Any ideas on how to improve on it are most welcome.

What else can I stuff in here?

Full set of images here

[NuclearWarfare]

You never cease to amaze me. You should make FRANK a brother that changes between a robot and a ion (Or rocket powered, your choice) fighter which you can then carry into orbit to destroy spy satellites and other enemy stuff

[katateochi]

You never cease to amaze me. You should make FRANK a brother that changes between a robot and a ion (Or rocket powered, your choice) fighter which you can then carry into orbit to destroy spy satellites and other enemy stuff

Thanks man!

I tried to make FRANK a set of wings that he could drive into and dock with, like Optimus' flight tech, but, well, I lost a couple of FRANKS (well over 10 in fact) in the process and gave up.

I'd not done any space plane stuff when I tried that thou. I might do better at it now I've made some viable planes, may return to that one later. I'm still trying to improve the lifting capability of this SSTO. I can't believe it but only just a few hours ago I realised that you can shut the intakes and reduce the drag!! doh! With 10 intakes on that thing it makes quite a difference and I was able to take the same payload up to a 150km orbit. Hard to believe that small difference in drag made such a difference really. I think I flew it better too, makes working out what design change results in what difference sometimes!

[Vanamonde]

Look, we've discussed this. I've been trying to build SSTO spaceplanes for MONTHS longer than you have. You're not supposed to be better at it than I am! Seriously people, this guy was asking me how to build these things 2 weeks ago, because he'd never tried it before.

[pa1983]

I know the feeling getting the first useful SSTO up there, did that last year and have worked on SSTO spaceplanes ever sens.

Few good tips for a good design.

Avoid stacking fuel tanks if possible and place them in parallel at the center of CG. That way CG wont shift.

Place wings last to get Center of Lift close to CG. If you use oddly angled wings SPH wont tell you the truth about center of lift relative to CG so test flying is the only way to check that on advanced designs.

Place all intakes as fare back as possible. Preferably behind the fuel tanks but infront of the engines.

Use MANY intakes. You should retch like 40km altitude before going over to rocket power alone and at least 1800ms, 1900ms+ is preferable that will cost you only a few hundred or so liters of oxidizer for a 100 ton SSTO to get to orbit.

Good tip is to gain this speed at a level flight at 32-34km altitude sens the air gets thiner over 32km and you can get those speeds.

Also using NV-1 will save you a lot of fuel. A LV-30/NV-1 combo could work to.

4x NV-1 can get 110 ton ssto to orbit or even more.

Airospikes are HEAVY and at the altitude you need them even LV-30 have good ISP and its light and powerful and the NV-1 is even better. Can use mechjeb to figure out Delta V and often airospikes are useless sens you just fight gravity with them for longer wasting fuel. Never use them my self sens they are in my opinion nurfed to uselessness.

ASAS should be placed as close as possible to the engines, behind or in between if possible to minimize any self oscillating. Having it in the nose is asking for wobble and trouble.

Last tip is WINGS. LOTS and LOTS of wings. Drag is low at high altitude so wont effect speeds much but it will help you climb the first 15-20km. Its more a concern if you go to other planets sens it dead wight but wings save fuel and increases cargo capacity and reduces the number of engines required to get up to speed and most of all climb so using heavy engines like NV-1 is not a problem with lots of wings.

Another tips or well bug or odd behavior I noticed is if that ALL engines are placed on girders, say you use the 375Kg one for a main mounting surface then a 1kg one for a mounting point, this will for some reason allow you to get down to 0.01 intake are before flaming out so its very easy to shut engines down in stages with actionkeys this way but ALL engines must be mounted this way for that to work. Its a bit odd.

Just use fuel lines to supply them with fuel.

Edited May 2, 2013 by pa1983

[Scottiths]

Very nice! I can't seem to get a cargo SSTO. Part of the problem is I can't deal with things much over 200 parts (computer just stops). I do have a high capacity Kerbal ferry though. Seats 12 plus 3 pilots for trips to and from orbit to rotate out crew or bring tourists to Kerbal Space Palace.

Docked to Kerbal Space Palace (KSP)

https://www.dropbox.com/s/bivq9jzn1b48plq/screenshot107.png

Heading in for a landing:

https://www.dropbox.com/s/l3j53wnzmfvde4m/screenshot109.png

Back home safe:

https://www.dropbox.com/s/oav9mycazv4k8xu/screenshot112.png

[Tw1]

Awesome looking SSTO, and the systems inside are so clever.

How high an orbit can it get to?

[joppiesaus]

Well that's a SSTO!

[Akalaël]

WTH of an airplane !

When I think I NEVER achieved a 100 meter-long fly, this SSTO makes me nervous.

Congrats'

[Kottabos]

.... wow ... just wow. I can barely get mine off the ground and you're lifting payloads. gotta admit I'm a bit jealous, but hey nice work man that is simply amazing.

[sokid2k]

If I flew that I would get roughly....1FPS.

[toric5]

have you tried ker? it is more accurate them mj

[StormyCrafter]

This is one of the best SSTO's i have ever seen!

[EternallySlaying]

I'm curious how testy your SSTO is to how the payload is stored. Have you tried putting the payload in the back of the bay to force your CoG back?

[katateochi]

I know the feeling getting the first useful SSTO up there, did that last year and have worked on SSTO spaceplanes ever sens.

Few good tips for a good design.

*snip*

Thanks for all your tips man. I could prob stick more intakes on it, but I wanted to not be too air-hoggy and aesthetics is an important aspect for me. It only has intakes on the front of tanks, without using splitters to double up the numbers. I might add a couple more in but only if I can keep it looking ok.

To get around the COG shifting as fuel drains I have quite a protracted network of fuel lines in there which forces the order that the tanks drain. The COG stays pretty level as they drain. I do also have the TAC fuel balancer mod on board, I manly use it to have a overview display of the fuel levels in all tanks, but I can use it to auto balance the fuel or shift it around as I need. When coming in to land and its mostly empty I need to shift the fuel forward to keep the nose down.

Very interested by your advice re engines. I started out using LV-30s and LV-45s, I also used the BearCat from on of the mods (NovaPunch I think) but I wanted the main frame and drive to be stock. In the end after many attempts the aerospike seemed to be best choice. It was similar on paper to the BearCat, just heavier. No way could I get it to work with the NV-1, but I guess that if I had more intakes and got higher before needing rockets that might work better. It's just so heavy, even heavier than the aerospike.

All my SAS is near the front and seems to work ok. might try moving it back and seeing if that helps.

Yeah, wings!! MOAR wings! I found that to be very true. Was really struggling to get throu the first part of the atmo, then I tripled with wing area by making it more of a tri-plane and it was much better. Might even add some more wings in. Part count is getting a bit high thou.

Anyways, thanks again for your advice, I'll incorporate it into my next one.

Very nice! I can't seem to get a cargo SSTO. Part of the problem is I can't deal with things much over 200 parts (computer just stops). I do have a high capacity Kerbal ferry though. Seats 12 plus 3 pilots for trips to and from orbit to rotate out crew or bring tourists to Kerbal Space Palace.

*snip*

that's a nice looking one. Like your Space Palace too and the way it docks inside it. What mod are you using for the passenger sections?

Awesome looking SSTO, and the systems inside are so clever.

How high an orbit can it get to?

On this first trial I was jumping up and down with joy cos I'd got to a 70km circular orbit. But I'm managed to improve on that quite a bit without any design changes. The only thing different is I (only just) realised you can shut the intakes a low alt and reduce drag, that a some better piloting and I can make 150km orbit no probs.

If I flew that I would get roughly....1FPS.

I get about 10fps with it. I'm going to try and reduce the part could by using some different tanks to try and improve on that thou.

have you tried ker? it is more accurate them mj

do you mean the kerbal engineer mod? I've not tried that yet. I hear good things, just I've been using MJ for so long I'm kinda used to it.

I'm curious how testy your SSTO is to how the payload is stored. Have you tried putting the payload in the back of the bay to force your CoG back?

I recently took a different payload up, three sections of a satellite. one part mounted to the front and the other 2 sections mounted to either side closer to the back.

It made very little difference, but that was a slightly lighter payload overall. The main craft is pretty heavy compared to it's payload capacity and its COG is slightly behind the center. I'm yet to try bringing a heavy payload down when the main craft is low on fuel. that will be more interesting I think.

I've updated it to use the new version of the KAS mod. VERY VERY cool stuff, go check it out.

Thanks for all your comments guys! I'm prob going to make a vid of this soon. I'll post that here when I do.

[pa1983]

I have over 200 intakes on my biggest SSTO and yes its BIG in terms of size and engine numbers so not as bad as it sounds.

You cant see the intakes ithere. I use the flying body concept. Advantage over that is maximum lift for minimum area. Fuselage parts are quite useless realy. Its important to try to use as high lift vs area wings as possible. Delta wings is in theory optimal then.

You can check out my designs here and download the craft file if you want to see how I hide intakes. They are all 100% stock.

http://forum.kerbalspaceprogram.com/showthread.php/25918-Versatile-SSTO-Spaceplanes-with-no-need-for-refueling

And sure intakes causes drag but engines wont run with out air so and as long as you have them behind CG your craft should stay stable. If not it will nose up and flip over usually.

I realy only notice heavy drag on intakes during reentry at 4500-5000ms but then you need all the drag you can get to slow down

Having the fuel tanks in parallel is realy reliable and runs all stock with out mods and you realy want to keep the part numbers down as capable SSTO spaceplanes requires a fair share of parts. No need to manage fuel usually with that but you probably see the advantage of that in the future when you build even greater spaceplanes I can tell that your just getting started but it looks good, if you keep it up your soon land at Duna and returning. I was where you are about 6 months ago so I can tell you theres a LOT an SSTO spaceplane can do if you want it to. I often felt I reached the limits but then I realized some better way of doing stuff and got more range.

So what I realized is, if its more effective in the end you usually let practicality and necessity govern the design. Basically all my crafts are built the way there are by necessity not because I like them to look like they do even if I add some trimmings to them

Edited May 3, 2013 by pa1983