Need Help Building SSTO spaceplane and project

[Tylerd]

Recently made a ton of $$$ in my career mode (normal difficulty), from repeating missions on duna/ike.. and now have enough $$$ to sort of play around with. I have all aircraft/spaceplane tech unlocked except for experimental aerodynamics.

So im allocating around 4-5 million towards a project. My goal is to setup a mega space station in orbit around kerbin, a very large mining base on the mun, and lastly a small refueler/miner rover near the KSC runway, I think you guys can see where this is going. The SSTO spaceplane I want to build will need to be able to reach and dock with my space station where it can then be refueled, then de-orbit, land on the KSC runway and refuel there. However I cant design/launch my station until I know what my SSTO is capable of. So if anyone has accomplished a similar type of project, let me know how you did it.

[skip Here] Getting to the point of my question:

where can i find tutorials on building spaceplanes and SSTO's that are compatible with the latest version of KSP, most the tutorials and youtube videos i see are from earlier versions and those craft no longer work or arent able to survive re-entry heat. Kerbal engineer tends to get buggy when im building a spaceplane, like not showing accurate delta v data, or not showing anything at all which makes this a bit difficult.

Edited August 11, 2015 by Tylerd

[capi3101]

I've got something similar set up at the moment in my own career save. Caveats: I use FAR, I haven't upgraded from 1.0.2 and I haven't got mining technologies unlocked just yet. I also still recover the planes at the end of the flight rather than re-launch and refuel them, though I did a set up where I would haul a plane back to the start of the Runway with a crash cart and refuel it a couple of versions ago (0.24, IIRC). I would say that KAS (and KIS) would be essential mods if you're wanting to go with something similar. I've been led to understand that DRE handles heating better than stock at the moment, so that might also be one to consider.

Let's start with the basics: are you going to want your plane to handle passengers, payloads, fuel loads, or some kind of combination thereof? What kind of capacities would you like to target?

[Pecan]

If your station is in LKO then it'll take very little for a SSTO to de-orbit, so it's hardly worth refuelling it just to land again. It's easier to design for something that has the 'spare' dV in orbit to rendezvous, dock (RCS/monopropellant) and de-orbit all on its own. *grin* If you don't have that much, chances are you'll miss your docking and won't be able to refuel at the station anyway - life's like that.

Presumably you've got bored of SSTO rockets, which are much, much easier to build and fly, especially for any useful cargo mass - although harder to land accurately. The only spaceplane tips I have are i) use a rapier engine for your first ones, ii) start small, iii) make something that flies well as a plane first, then work on high and fast.

Here's one I made earlier:

The fuselage there consists of two FL-T400 fuel tanks, with a Mk1 Liquid Fuel Fuselage sandwiched between them. Wings are swept wing B and tail-assembly uses structural wing d. Building this yourself, the only 'trick' is that the landing gear is attached to the wings with cubic octagonal struts, to give them a bit more length. Flies very nicely, lands around 40m/s with 5-degrees of pitch.

ETA for below:

... ferrying Kerbals to LKO costs next to nothing with spaceplanes.

Good point - the design above cost 8k more to build than my best one-man SSTO rocket but the fuel costs 1.5k less per launch (assuming 100% recovery for both, which is a long-shot for rockets). Not only does that mean the spaceplane breaks-even after just 5 launches but it pays for itself completely after 21, if you're ever likely to launch anything 22 times ^^.

Edited August 11, 2015 by Pecan

[RexKramer]

Best advice for spaceplanes is to start small. Start with a goal of getting one Kerbal to orbit and back. Then start slowly building larger spaceplanes.

Although it is possible to deliver moderately large payloads to orbit with spaceplanes, it is fairly difficult. With 1.0.4's aero and engine performance, I find spaceplanes are useful for ferrying Kerbals to orbit and back, but not much else. There is definitely a financial advantage with them though, ferrying Kerbals to LKO costs next to nothing with spaceplanes.

[Fearless Son]

Like others said, start small. A truism with spaceplanes is that the smaller you can make them, the more efficient they can be. It may be tempting to load it up with fuel, but that will bite you if you try to carry too much. Making a functional spaceplane requires a lot of experimentation and tweaking, so be prepared for several attempts.

You always need a little extra liquid fuel for a spaceplane to power its jets before the rockets kick in, but you do not need much. An ideal solution are the air intake nacelle, structural nacelle, or engine pre-cooler, which carry a bit of liquid fuel inside of them. Not a lot, but unless your spaceplane is a serious gas guzzler, it should be enough.

Minimize drag. Cannot emphasizes this enough. Shock cone intakes are ideal for this, but do not go overboard on intakes. As long as you have enough air to power everything under your non-rocket flight ceiling, you should be fine. Speaking of flight ceiling, most planes will start to cut out at about 20,000 meters up. Try to get to 12,000 meters as quick as possible, then go into a gentle ascent from about 15,000 meters to 20,000 to build speed. Watch the thrust output of your jet engines. When they start to drop significantly and your acceleration begins to slow (but before it stops,) hit the rockets. If you have separate jets, leave them on even when the rockets go until they cut out.

Then ride that acceleration until your apoapsis clears the atmosphere. Make sure you have enough rocket fuel to circularize when you get up there.

[GoSlash27]

Tylerd,

There are lots of threads out there dealing with 1.04 SSTO spaceplanes. Check the "pro SSTO" and "K prize" threads for recipes.

What, exactly, do you want to accomplish with your SSTO?

Best,

-Slashy

[Zephram Kerman]

Here's my similar project, since you asked. The Kerbal Tourism Program is somewhat smaller than what you described, but could be scaled up with practice.

The SSTO uses Rapiers, but earlier designs actually did better with 2x Whiplash and 2x Thuds. Anyway, the idea is very similar to what you proposed:

• SSTO takes off from runway with four tourists;

• rendezvous and dock with Trans-Munar Shuttle already in LKO with partial fuel;

• shuttle has just enough fuel to reach Mun or Minmus and land there;

• refuel shuttle with a rover tanker from the mining base;

• shuttle returns to LKO to unload tourists with enough leftover fuel for the next trip;

• SSTO returns the tourists to the surface.

I use a variant of that same SSTO to cheaply launch satellites and probes, too. The trick is to keep the payload light enough that the whole thing can make orbit. Deorbit close enough to the right time to point it at the runway, and land for close to 100% recovery value. Sometimes the front solar panel overheats, but everything else has been totally safe.

[Tylerd]

Tylerd,

What, exactly, do you want to accomplish with your SSTO?

Let's start with the basics: are you going to want your plane to handle passengers, payloads, fuel loads, or some kind of combination thereof? What kind of capacities would you like to target?

has to be SSTO and can Carry at least 4 passengers to the station and dock. Idealy I would prefer to have my station pretty high above kerbin, but not higher then the mun. This spaceplane is simply for shuttling astronauts/tourists back and forth between kerbin and my space station.

Edited August 11, 2015 by Tylerd

[GoSlash27]

Okay, that's a start.

Low passenger count spaceplanes can be done very economically. We really need to pin down exactly how much orbital DV you'll be needing. Somewhere between LKO and the Mun is a pretty vague mission requirement. I always design my stuff for a LKO mission (75x75) and 150 m/sec reserve.

We also need to sort out which approach we're after. Minimum buy- in, low mission cost, high payload fraction, all- fuel, green, low tech... Each approach is different and requires a different recipe/ profile.

A couple different approaches that I've used:

Low tech

Low operating cost

*Edit* Reviewing "experimental aerospace", there's nothing there you need for this job. It's pretty open- ended.

Best,

-Slashy

Edited August 12, 2015 by GoSlash27

[capi3101]

has to be SSTO and can Carry at least 4 passengers to the station and dock. Idealy I would prefer to have my station pretty high above kerbin, but not higher then the mun. This spaceplane is simply for shuttling astronauts/tourists back and forth between kerbin and my space station.

Ah, okay. GoSlash27 has given you some good advice to follow there. Myself, I have a plane that'll haul six Kerbals at a time to LKO - the Raven 7 (of which apparently I don't have any screenies - which is weird, because I could've sworn I'd taken a whole bunch...). My main space station over Kerbin is orbiting at 85 kilometers and I do use it as a refueling depot and staging area for tourists. I designed the Raven with 1,800 m/s of rocket delta-V; if it's refueled in orbit, it'll make Mun or Minmus orbit easily enough and I have used the design for that purpose on a couple of occasions (that particular craft earned itself a name - Free Bird 7).

I also have a refuel plane that I use to top off the station's tanks when they become depleted - the Vulture 7:

I tried using it to refuel the Mun space station once; it's coming back from there in this picture. Did the mission reasonably well.

So planes then. You're working with stock air, right? General guidelines for stock air are to assume a 25% payload fraction and either 13 tonnes per RAPIER or 15 tonnes per Turbojet and around 200 kN of rocket per jet (I use Aerospikes - despite the lack of gimbal, they have reasonable thrust and relatively high Isp - the high Isp in turn lets me get away with carrying less rocket fuel. Another decent choice are pairs of Thuds). Your payload in this case is going to be your cockpit or control module, the docking port and the hab module, plus you're going to need a source of RCS fuel (two roundified RCS tanks in a cargo bay would be plenty), a couple of solar panels and a battery or two. Put that together, note the mass and multiply the result times four - the result is how heavy you can expect your plane to be, and from that you can determine how many engines you're going to want to include.

I really like Slashy's designs...I wonder how they'd fare in FAR...and I still wonder why I don't have any screenies of the Raven; I'll have to remedy that.

[Tylerd]

Okay, that's a start.

Low passenger count spaceplanes can be done very economically. We really need to pin down exactly how much orbital DV you'll be needing. Somewhere between LKO and the Mun is a pretty vague mission requirement. I always design my stuff for a LKO mission (75x75) and 150 m/sec reserve.

We also need to sort out which approach we're after. Minimum buy- in, low mission cost, high payload fraction, all- fuel, green, low tech... Each approach is different and requires a different recipe/ profile.

*Edit* Reviewing "experimental aerospace", there's nothing there you need for this job. It's pretty open- ended.

Best,

-Slashy

as far as payload goes, I use KAS and KIS, so id like to have the capability of carrying one containers worth of supplies in a service bay, and probably a retractable solar panel in there to. ill probably be going with the mk2 cockpit + mk2 crew cabin, so total of 6 passengers. Im not worried about mission cost, im allocating 4-5 mill for this project, and the shuttle program will be the cheapest part of it. My main issue right now is simply figuring out how to pilot these things efficiently (how fast and what angle should i be going at which altitude), de orbiting and landing on the KSC runway will be another challenge, but im figuring it out.

thanks for everyones responses, Will get back to this in a few days, and hopefully complete the project, i plan to screencap throughout the whole process and create a thread for it.

[GoSlash27]

Tylerd,

I'm looking forward to it. Lots of knowledgeable and helpful people in the KSP spaceplane community, so you'll have plenty of assistance when you need it.

Best,

-Slashy

[Edax]

Adding to some earlier advice, I would test the airworthiness of the plane first. If the airframe is stable enough to land on the island runway, take off again and land at KSC, then you have a stable craft and can then begin testing to see if it can go into orbit. That way you don't try deoribiting in an uncontrollable death trap.

[KerikBalm]

I've got a crew ferry SSTO that will haul 6 kerbals to Mun orbit, Minmus orbit... or escape Kerbin, then return for getting extra XP for kerbals.

I'm pretty sure it could manage a Minmus landing as well... I don't know about the Mun though...

Just getting to a space station.... that is a pretty easy task.

SSTOs may seem daunting now, but you should quickly find that you've set the bar rather low.

[ajburges]

Adding to some earlier advice, I would test the airworthiness of the plane first. If the airframe is stable enough to land on the island runway, take off again and land at KSC, then you have a stable craft and can then begin testing to see if it can go into orbit. That way you don't try deoribiting in an uncontrollable death trap.

Airworthiness is complex to test.

A full fuel landing tests both your structural integrity and abort options.

Pulling out of a high Mach dive tests (with heavy load) wing loading. It's important to know what your wings can handle so you know when it is safe to begin aerodynamic fight after reentry.

Finally and hardest, you want to judge low lift stability. Drag is a significant force for much higher than lift. Some craft are aerodynamically stable only until a certain height. A mistake while it is in unstable phase can put you into a flat spin. Thankfully this often is high enough that recovery can be done easily, but it still mucks your trajectory up.

Of course it is also important to tune craft performance. Space plane ascent is more involved than rockets. If it is a pain to fly, you won't.

[Wolf Baginski]

Engines and air intakes have a high-power stage that you need to be in to get into orbit. It usually starts showing at about Mach 1.5 and if you can get into it the spaceplane will work. The air-breather combination also affects how high you can go, and you can get over 1200 m/s at 20,000 m. How fast do you dare go? You're going to lose some of that deltaV as you climb to 40,000m, but there is a trade-off between time and temperature.

I use MechJeb, and there's an acceleration-limiter option, applied generally. Once you get into the super-thrust speed range, using that will show you, by the throttle setting applied, if you could raise the nose some more. But as you close 20,000m drop the nose and go for speed. I keep the Ascent Guidance window open, since that gives me decent gidance for the rocket stage of the flight. Check the shape of the ascent curve at the start, you want to avoid a sharp pitch change in the transition as it's both a huge burst of drag and, potentially, a disaster for stability. In effect, it's as if you started the gravity turn very early. You can be doing a zoom-climb to bring the nose up before the transition to MechJeb Ascent Guidance.

Anyway, the Ascent Guidance window has a toggle for the acceleration limiter. which applies whether the autopilot is active or not. And it had settings for the target orbit.

What I sometimes find it that there is a surprisingly long coast to the edge of atmosphere (you're in sub-orbital flight with the right apoapsis) followed by a long circularization burn. A pure rocket might not go quite so fast in the atmosphere and, by the edge of atmosphere, have lifted the periapsis more.

I'm inclined to the view that a good spaceplane looks way over-powered. A light single-RAPIER setup can work well, but if you can't get frightening acceleration through the sound-barrier it's going to be tricky to get enough speed.

Test flights matter. It feels like a bit of a trick, but transfer the craft file from your career game saves to those for the sandbox. Do your testing there. Is that any different from NASA testing a design in a flight simulator? Some of what MechJeb does you can see in the same light. That acceleration limiter is a way of testing the climb angle. But you have lift; you can sustain a high climb angle, but climbing with lift works better for fuel consumption.

It depends on the design but I would consider reduced throttle and a relatively shallow subsonic climb to 6,000 m, full power to boost through to Mach 1.5 (about 450 m/s) and then you're in the bat-out-of-hell stage that takes you to the transition altitude and "excessive speed".

The sandbox is the flight simulator for your designs.

[Vegvisir]

Okay, that's a start.

http://i52.photobucket.com/albums/g13/GoSlash27/ProBuild1_zpsyxdac06t.jpg

I've literally spent days trying spaceplanes to orbit again and again....decided to dl your craft and give it a go. Well, first go and it performed best so far (no surprise really haha you know what you're doing! ) Barrage of questions time....What flight profile do you use? I used 20deg early on and about 10deg from maybe 11-12K up. What would you say is ideal vertical speed for varying altitudes? And when jet thrust starts dropping off, around what kN do you actually shut them off and close intakes? I've been doing that at 20 or so.

Edit. Shoulda looked here some time ago

Scott Manley. 1.0.4. Spaceplane. No rapiers. Winning. Edited August 14, 2015 by Doslidnyk

[GoSlash27]

Doslidnyk,

The profile varies greatly with the t/w and engine type. That one's a heavy-ish jet, so there's a slow climb (20° or so) to 10km. The plane should go supersonic at 10 km and exceed 360 m/sec before resuming the climb. Reduce pitch to 5° at 16 km altitude and build speed as you work up to 20km. Speed of this example tops out around 1100 m/sec.

When acceleration stops, engage the rockets but leave the engines running and intakes open.

I don't close intakes anymore. I haven't seen any benefit in doing that.

Best,

-Slashy

[Vegvisir]

Thanks for the tips Slashy

For what I want to do, I think heavier ones will be the go for now, with passengers and such. But I did it! Gonna refine my design so 1) doesn't run out of fuel so soon, if possible and 2) perhaps build variants for probe deploys and debris missions. I dunno if I can make fuel missions work, doubt I'd have enough left over for it to be worthwile.

[GoSlash27]

Doslidnyk,

Congrats and glad I could be of assistance.

Fuel missions are do-able in the same fashion, but you want to scale way up to make the trip worthwhile.

This one does 30t of fuel and oxidizer to station in LKO.

Best,

-Slashy