Stock ssto with 50 ton payload or greater?

[Camaron]

I think this will become a much more popular topic IF/ WHEN Kerbal parts costs actually begin to count against some kind of actual economy, and hopefully, simultaneously becomes capable of truly recovering safely discarded / returned to Kerbin parts. I would love to design huge liquid boosters with chutes and legs and a probecore solely to get all the components back. It would be an amazing challenge, and I hope something like that happens.

Judging from the parachutes on most of these designs, I am assuming that this is the intention.

Soon, hopefully! (Sounds like 0.24 is really pushing for the beginnings of something like that.)

But for now, I'll stick with blasting 1500-ton fuel ships into orbit because there's no existing mechanism to account for loss/waste.

[O-Doc]

The main reason I built those heavy lifters is my personal obsession with planes. I love building them as much as flying them. I don't get into the VAB much and KSP has mostly been the SPH experience. While my lifters can do long range, their primary goal is to drop off payloads inside the Kerbin system. For cargo hauling I will generally take a nuke engine attachment with a small fuel tank for space transit. Depending upon payload I'll drop off my cargo in LKO or do a return fly-by of Mun or Minmus and drop the attachment which, will do a capture burn or a slingshot maneuver for planetary transfer.

Your basic hard limits on payloads is definitely air intakes and wings. More mass means more wings and intakes which are complete part hoggers. There gets a point when the game slows down too much to get any pleasure out of flying a massive plane. Also, your judgement in the ascent starts to get thrown off when real life seconds are many factors more than game seconds.

BTW TeeGee, the Flyingfox puts 4 jumbos(equivalent) into orbit.

[TeeGee]

I think this will become a much more popular topic IF/ WHEN Kerbal parts costs actually begin to count against some kind of actual economy, and hopefully, simultaneously becomes capable of truly recovering safely discarded / returned to Kerbin parts. I would love to design huge liquid boosters with chutes and legs and a probecore solely to get all the components back. It would be an amazing challenge, and I hope something like that happens.

Judging from the parachutes on most of these designs, I am assuming that this is the intention.

Soon, hopefully! (Sounds like 0.24 is really pushing for the beginnings of something like that.)

But for now, I'll stick with blasting 1500-ton fuel ships into orbit because there's no existing mechanism to account for loss/waste.

...YET. The craft everyone has put together above are all 100% reusable AND can lift a LOT of weight. So everyone above has built cheap, fully reusable heavy lifters, and therefore will have very cost effective space programs.

Everyone here should be proud of what they've developed, and I look forward to seeing what people come up with next!

[TeeGee]

The main reason I built those heavy lifters is my personal obsession with planes. I love building them as much as flying them. I don't get into the VAB much and KSP has mostly been the SPH experience. While my lifters can do long range, their primary goal is to drop off payloads inside the Kerbin system. For cargo hauling I will generally take a nuke engine attachment with a small fuel tank for space transit. Depending upon payload I'll drop off my cargo in LKO or do a return fly-by of Mun or Minmus and drop the attachment which, will do a capture burn or a slingshot maneuver for planetary transfer.

Your basic hard limits on payloads is definitely air intakes and wings. More mass means more wings and intakes which are complete part hoggers. There gets a point when the game slows down too much to get any pleasure out of flying a massive plane. Also, your judgement in the ascent starts to get thrown off when real life seconds are many factors more than game seconds.

BTW TeeGee, the Flyingfox puts 4 jumbos(equivalent) into orbit.

4 JUMBOS! Wow!

I also spent most of my time in KSP designing SSTO's in the SPH. I have an enormous library of various ssto's, because I've always been fascinated with them. I stopped designing larger ssto's because of the mass payload fraction problem, as the heavier your craft gets, the less payload it can lift. I gave it up in pursuit of smaller ssto's that are purely used for passenger transport to LKO or Munar/Minmus orbit (I've posted them in other threads).

When I made the discovery of attaching airbreathing jet engines onto larger payloads and decoupling them in orbit, my ability to get massive payloads into orbit was finally realized with full reusable method AND low fuel amount. BUT just to show you what I was building before I started thinking differently, here is one of my largest spaceplane designs:

Edited April 14, 2014 by TeeGee

[O-Doc]

Nice plane! It takes a lot of work to put something fairly large into the air.

SSTO payload fractions? Realistically 50% for a functional heavy lifter SSTO. You have to start spending tonnage on structural stuff so it can survive landings and loss of control on re-entry. I have an SSTO with 60% payload fraction but, like you said, it's a smaller craft. It's payload is fuel for 7.3km/s dV but it can only achieve that with MASSIVE wing and intake spamming.

[Fellow314]

Of course you are! How much payload does she carry?

I think that thing weighs around 82t.

(Which is either just over or just under 50% of the launch weight depending on if you count the landing gear or not )

Edited April 14, 2014 by Fellow314

[LordFjord]

Nice plane! It takes a lot of work to put something fairly large into the air.

SSTO payload fractions? Realistically 50% for a functional heavy lifter SSTO. You have to start spending tonnage on structural stuff so it can survive landings and loss of control on re-entry. I have an SSTO with 60% payload fraction but, like you said, it's a smaller craft. It's payload is fuel for 7.3km/s dV but it can only achieve that with MASSIVE wing and intake spamming.

I have built a few heavy SSTO lifters before that could deliver 40 tons to orbit, but somehow I am struggling with my current design. And a payload fraction of 50% is something I can only dream about. I'd say I'm roughly at 33% -> I am doing something wrong.

Either with the design, or with the flight.

I have 1 turbojet for ~10tons of weight on the runway, maybe 2 intakes per turbojet. Lift should be enough, the AoA is ~15-20° when flying high.

My problem is that the heavier designs struggle to gain speed in high atmosphere. 25km altitude, maybe 1100 m/s before the engines flame out. That is way too slow -> nukes have too low thrust to help me get faster, I have also tried Aerospikes, those ran outta fuel before I reached orbit.

My previous designs also had these flaws, but compensated it by MOAR BOOSTERS -> orange tanks with skippers/mainsails.

This time I wanted to build it smaller and more efficient, without the 2.5m parts.

My goal is still to make a 2nd attempt at the affordable space program challenge with something that can haul the station science parts to orbit (up to 40 tons).

Will post some pics when @home...

Edited April 16, 2014 by LordFjord

[O-Doc]

I'd say I'm roughly at 33% -> I am doing something wrong.

33% is pretty awesome with no intake spamming. Payload fraction is mostly about how many intakes you are carrying. I think my lifters are around 10-15 RAM intakes per turbo jet.

I have 1 turbojet for ~10tons of weight on the runway, maybe 2 intakes per turbojet.

I calculate a bit differently based on my engine SSTO setups. I start with a basic/turbo/nuke stack as being able to lift 25 tons into orbit. This is my goto setup for anything in the 10-25T SSTO range. For heavy lifters where less time in lower/higher atmosphere is important to payload fraction I will add half as much to double that in extra turbos. But, that's just my play style. SSTO needs to be able to accelerate vertically at all times to be efficient.

In terms of flying, without doing a video it's hard to get into what you need to do to break through the atmosphere without having a ridiculous amount of turbos. On any new design/craft it's best to just probe your apogees on each engine and engine combination. Starting what you have turned on at take-off, see how high and fast you can get. Go through all the engine transitions you are going to use for your ascent profile and have a look at your absolute performance. Then, you can extrapolate an efficient ascent corridor from these numbers. I say corridor because there is always that point above 18km where you don't want to be putting anymore energy into vertical speed than absolutely necessary. It should be set before entering into your turbo peak so that your engines are maximising energy going into orbital speed when your engines are at their most efficient.

A great ascent will have a near constant vertical speed through the turbo peak power range. The longer that constant vertical speed is carried, even so far as into orbital speed, the better.

How long are your turbos sitting on or near the 225KN peak? This is where your play changes from just getting into orbit any way you can to getting the job done efficiently. Ergo, you're going to design some kick-ass SSTOs with killer dV@LKO. Establishing this vertical speed in the ascent corridor is why I use basic jets. They are exceptionally good at establishing the vertical component of the ascent and early on too. The orbital velocity I leave to the turbos.

[LordFjord]

33% is pretty awesome with no intake spamming. Payload fraction is mostly about how many intakes you are carrying. I think my lifters are around 10-15 RAM intakes per turbo jet.

It didn't make it to orbit yet - but I hope I can keep it above lets say 25%.

Thanks a lot for the hints, I will try to add more intakes. It seems I will need a whole lot more than I thought.

Another mistake I think I did that I did not level out my flight to gain more speed, I kept ascending and whenever the flameout happened, I switched to rockets.

I see I have a long night with SSTOs ahead

I will try to write down the altitude / pitch° / speed values.

And to keep this on topic, here are some old old prototypes that actually got ~40 tons to orbit. Might have been able to handle 50 tons as well.

This one's ugly as hell, lagged like hell and never survived a reentry due to spinning/disintegration - but made it into orbit...

This one looked great, but I lost the file at a reinstall. If i remember correctly then it was also unable to return in one piece...

But those are a few month old - now I want to build something reliable.

A first good sign was that after running dry on fuel at ~40km altitude, the whole thing could still land in one piece, including the 40 tons payload.

[O-Doc]

That second design is cool! I did dispense some advice about heavy lift SSTOs in this thread. The tl;dr is: I found out that reliable heavy lift design is as much about figuring out a solid engineering process rather than, throwing together some parts and hoping it will fly.

[TeeGee]

33% is pretty awesome with no intake spamming. Payload fraction is mostly about how many intakes you are carrying. I think my lifters are around 10-15 RAM intakes per turbo jet.

I calculate a bit differently based on my engine SSTO setups. I start with a basic/turbo/nuke stack as being able to lift 25 tons into orbit. This is my goto setup for anything in the 10-25T SSTO range. For heavy lifters where less time in lower/higher atmosphere is important to payload fraction I will add half as much to double that in extra turbos. But, that's just my play style. SSTO needs to be able to accelerate vertically at all times to be efficient.

In terms of flying, without doing a video it's hard to get into what you need to do to break through the atmosphere without having a ridiculous amount of turbos. On any new design/craft it's best to just probe your apogees on each engine and engine combination. Starting what you have turned on at take-off, see how high and fast you can get. Go through all the engine transitions you are going to use for your ascent profile and have a look at your absolute performance. Then, you can extrapolate an efficient ascent corridor from these numbers. I say corridor because there is always that point above 18km where you don't want to be putting anymore energy into vertical speed than absolutely necessary. It should be set before entering into your turbo peak so that your engines are maximising energy going into orbital speed when your engines are at their most efficient.

A great ascent will have a near constant vertical speed through the turbo peak power range. The longer that constant vertical speed is carried, even so far as into orbital speed, the better.

How long are your turbos sitting on or near the 225KN peak? This is where your play changes from just getting into orbit any way you can to getting the job done efficiently. Ergo, you're going to design some kick-ass SSTOs with killer dV@LKO. Establishing this vertical speed in the ascent corridor is why I use basic jets. They are exceptionally good at establishing the vertical component of the ascent and early on too. The orbital velocity I leave to the turbos.

I have 4 intakes per jet.

Keep these designs coming guys, the larger the payload the better!

Edited April 16, 2014 by TeeGee

[LordFjord]

Thanks for the help folks, it helped a bit but Jeb still didn't go to space yesterday.

I don't want to clutter this thread with it. I made another topic for that here.

Keep the designs coming, they are inspiring!

[Overfloater]

here is one of my largest spaceplane designs:

http://i.imgur.com/P6FH4SX.png

http://i.imgur.com/G4n4APa.png

so... THIS is the plane you once mentioned to me! I've been searching through all of your posts and couldn't find it... xD

This is very aesthetic!

[TeeGee]

so... THIS is the plane you once mentioned to me! I've been searching through all of your posts and couldn't find it... xD

This is very aesthetic!

It's an overdesigned piece of poop. But thanks for the nice complement!

I don't know what I was thinking building that thing.