Help with Cargo Lifter SSTO

[Sleipnir]

Hey all,

really seems like SSTO's are the new "in" around here at KSP. I have build several of my own (mostly failures) but got one working one into orbit. I have also read a few things about them on the forums and looked at some designs, but pretty much all SSTO's are single seaters non cargo capable planes. I am more a man of functionality and am looking for a way to launch things into orbit (2m wide parts max) without creating any debris and SSTO seems to be the way to go. I just need a design that is capable of that and it appears to be impossible to do with stock parts.I have a few mods like B9 Aerospace Pack to help me out with cargo bays etc. But i am still lacking a good design.

So far what I have learned is to launch the SSTO vertically, that way i dont have to worry about C.o.M. and C.o.L. being unbalanced (which will happen as the cargo changes) as long as the C.o.T. is lined up with the C.o.M. Then once the payload is released It could land like a plane again. Thats pretty much all I got for designs, could anyone give me any more tips about larger sstos? I am still stumped about what engines to use, and whether I should ditch jet engines as they don't seem to do as well during vertical launches.

Any help is appreciated.

Dan

[bsalis]

SSTO Spaceplanes are not very good for lifting payloads.

[Van Disaster]

Well, they're quite good at efficiently lifting cargo, just not very much of it. If you're launching vertically you might as well just make it a straight up rocket, though - the advantage of a plane is using the wings to counter gravity drag.

[Sleipnir]

Can a rocket land vertically on kerbin just using its engines?? has anyone ever done that? I just want to limit the amount of debris I am creating and conventional rockets just don't do that. Plus it adds a challenge, I dont want to cheat anymore and have the "debris" slider set to zero anymore

[RoboRay]

Can a rocket land vertically on kerbin just using its engines?? has anyone ever done that? I just want to limit the amount of debris I am creating and conventional rockets just don't do that. Plus it adds a challenge, I dont want to cheat anymore and have the "debris" slider set to zero anymore

Indeed.

Any kind of SSTO design is always going to have limited cargo capacity, however, especially a reusable one that you return to KSC. Heavy cargo should be lifted with conventional rockets.

Edited May 1, 2013 by RoboRay

[Sleipnir]

Indeed.

That is AWESOME! what kind of cargo does it lift? Kerbals only or actual parts?

[Aladran]

Why would you want a SSTO for cargo lifting???

Heavy payload require an efficient vehicle, so having a large fuel tank required in SSTO result in a large dead weight once the fuel reserve drains out.

Ideally you want to jettison this dead weight to keep your TWR optimal.

SSTO is good for reusable vehicle, used for personal delivery, not heavy lifting.

[RoboRay]

That is AWESOME! what kind of cargo does it lift? Kerbals only or actual parts?

It's just for kerbals, hauling seven of them to orbit and back.

But if you dock it in orbit for refueling, it can get to Duna and back:

Mission Album: http://imgur.com/a/rvkwl#0

More details and the .craft file download here: http://forum.kerbalspaceprogram.com/showthread.php/26778-Pegasus-SSTO-inspired-by-the-McDonnell-Douglas-DC-X-Delta-Clipper

Edited May 1, 2013 by RoboRay

[Sleipnir]

Why would you want a SSTO for cargo lifting???

Heavy payload require an efficient vehicle, so having a large fuel tank required in SSTO result in a large dead weight once the fuel reserve drains out.

Ideally you want to jettison this dead weight to keep your TWR optimal.

SSTO is good for reusable vehicle, used for personal delivery, not heavy lifting.

That is true, but I want to minimize the debris i am creating, so an SSTO or atleast a semi reusable like a Space shuttle would do that. I know I could just edit the cfg file to delete debris but thats cheating and i dont want to do that

[Eric S]

If that's the only reason you want to use an SSTO, just make sure that any stage that will make orbit has a probe pod on it, and either enough left over fuel to dump it in the ocean or some sepratrons.

Personally, the only (reasonable) reason I'd consider a cargo SSTO would be to minimize per-launch costs in campaign mode, and I think I'd be rather tempted to go the SpaceX route for reusability. With Romfarer's addon to extend the physics simulation range, we might even be able to parachute the first stage back to earth.

[ThePsuedoMonkey]

You really need to design an SSTO around the payload you want to deliver. All of my successful SSTO designs have been spaceplanes that deliver small probes (<1 ton) before returning to KSC. For those, I keep my CoL a bit behind the CoM to balance between allowing a steep liftoff angle and a stable re-entry flight. The most difficult part is determining the appropriate amount of lift, which I pretty much just experiment with.

[PolecatEZ]

With proper wing balancing, you need surprisingly little lift factor total for your craft. I was told 1 "lift unit" per ton is optimal, but I've gotten away with about 40% of that. I see a lot of people just piling on the wings, but really it just needs a better balancing.

Payload fraction should be about 15% or so. I've gotten up to 40%, but its painfully slow to get to orbit like this and you have NO margin for error on your orbital vector climb - a single flight can take 30+ minutes just to reach orbit with some knuckle-wrenching level out periods. After this I just said "f-it" and went back to rockets for anything over 8 tons.

[Sleipnir]

With proper wing balancing, you need surprisingly little lift factor total for your craft. I was told 1 "lift unit" per ton is optimal, but I've gotten away with about 40% of that. I see a lot of people just piling on the wings, but really it just needs a better balancing.

Payload fraction should be about 15% or so. I've gotten up to 40%, but its painfully slow to get to orbit like this and you have NO margin for error on your orbital vector climb - a single flight can take 30+ minutes just to reach orbit with some knuckle-wrenching level out periods. After this I just said "f-it" and went back to rockets for anything over 8 tons.

Thanks for sharing your insight man, yeah i am going back to rockets as well. As someone else suggested i am gonna attach a probe and then deborbit any stages that way that are in a permanent orbit. I have been trying for a while now to replicate the Venture Star which irl should have been capable of lifting decent sized loads, but currently in the game I can't find an engine that meets the thrust and efficiency requirements

[Dictator Dan]

If you dont want to create debris, and are going to a low orbit, (<100km) a probe core, and maybe a battery or solar panel, if you are going to leave it for more than a few minutes, and 40 RCS fuel on Rockomax 64 tanks can deorbit, allowing you to send asparagus staged rockets up. If you dont like the thought of having to control stuff other than your main rocket, asparagus stage is still the way to go for cargo, just make sure to dump the last stages with your periapsis under 10,000 meters, this will ensure that those stages are destroyed in Kerbins atmosphere.

SSTOs do not lift a large amount of weight, relative to their size, and I find them best for crew delivery and return, as opposed to sending stuff like fuel or station modules up.

[Aladran]

That is true, but I want to minimize the debris i am creating, so an SSTO or atleast a semi reusable like a Space shuttle would do that. I know I could just edit the cfg file to delete debris but thats cheating and i dont want to do that

I understand, what you can do to avoid having to many debris, is to jettison your your last big stage before your orbital insertion, so it will fall back on kerbin. And you use your orbital stage to circularise.

That's what I aim to do to avoid debris.

[Daze]

Or you can but a probe with a RTG on the last stage, so you can de-orbit it after the circularization

[capi3101]

I minimize debris any more by putting a probe chassis on the part of my booster that gets my payload into orbit. Once the payload's detached, I just shift control over to the booster, turn it around and fire retrograde to de-orbit it. That strategy does require you to have a little bit of gas left in the can when you finish boosting the payload, but I find that's usually the case more often than not. Make sure you stick some batteries on the probe at a minimum; it does no good for it to power down before you can affect a de-orbit.

[Van Disaster]

I have a ( FAR ) heavy lifter spaceplane that'll take 25t to Kerbin orbit ( I'm not actually sure how far it'll take it, I never get the same ascent profile ), weighs 74t fuelled but otherwise empty. That's a reasonably old design & I'm sure it could be bettered, but it works and I don't really want to touch it. I very much doubt I can get that fraction of payload in orbit with a rocket...

Can't really go much bigger though without combined parts, it's already sluggish as it is.

[Sleipnir]

Or you can but a probe with a RTG on the last stage, so you can de-orbit it after the circularization

That is what i am going to do from now on. Altough i have to say the B9 Aerospace pack allows you to build spaceships of monstrosity size with relative low part count so I might try again to build some "Mothership" SSTO capable of Carrying heavy stuff

[rosenkranz]

I've gone both ways with this. I've got a tri-column setup that will take 60t to orbit and return to KSC. I just cant get it any higher with out boosters. Lately i'm using 100% recoverable stages (w/parachutes and all) to get 100t or better out.

[tavert]

Jet engines work fine with vertical takeoff, you just need at least 1 per ~10 tons total mass. If you spam intakes, you can get within 100 m/s (or less) of orbit only on jets. If you have more than one though, you will likely lose control if any of them flame out. Using MechJeb2 to fly can avoid that.

Example: http://imgur.com/a/Hdew6#0

[frozenbacon]

The total weight of this thing was about 120 tons (with the cargo it was about 128)and it got into space using FAR.

http://i.imgur.com/hdN8Nhv.jpg

Don't know how the hell I did it that time, though, I cant seem to do it again after removing those side VTOL engines that weren't even turned on the entire ascent. Seems to be recurring theme in all of my planes... it works and I change one tiny thing like move the wings one mm backwards and it ends up breaking the plane forever. For some reason it refuses to pitch up at really high velocities even though the COM is way behind the COL.

Edited May 4, 2013 by frozenbacon

[Van Disaster]

FAR moves the CoL rearwards with speed ( I suspect more specfically when you go supersonic, as it should ) - I made some hinged wingtips to cope with that on one aircraft, I just make heavy use of TAC fuel balancer usually. Thankfully if you mess up at 25km you have a long time to get out of your spin

Posted somewhere before: the big one with the Mk4 fuselage is obviously the heavy lifter. Not sure if it can lift more than 25t if I added more fuel, I suspect it might be near a thrust threshold - maybe with some alternative rocket engines.

B9 mod lets you do ludicrous stuff:

I think that used 50t of fuel or so getting into orbit . Was a tanker, had some horrible issues on re-entry and needs a total rebuild with recent B9 versions, but it's possible to make some gigantic winged lifters.