Trying my hand at a spaceplane-Having some issues

[DalisClock]

So during breaks at building pre-fab buildings/landers for my mun base, I've been messing with building a spaceplane to act as a crew transfer vehicle to my orbiting space-station. I've built something that will fly, glide and land pretty decently during atmo tests but I haven't been able to get it to orbit yet to test re-entry.

The biggest issue I'm having is getting enough thrust and dV to get it to orbit. My intial idea of attaching via a radial decoupler to one of my standard rockets ended...pretty poorly and I've been trying with various combinations of boosters to get at least up to the upper atmosphere. I'm not even trying to think about SSTO yet. I just want something that can get to space, dock and return. Half the spaceplane stuff I've seen seems to be SSTO and I'm wondering if nobody does the "piggyback on a rocket method", so advice would be nice, or at least a pointer towards a good tutorial.

The other issue is gonna sound weird and I haven't been able to find any reference to it on the forums yet. I'm okay at landing on flat ground(haven't been able to return to the KSP runway yet) but frankly, I want an alternate abort mode just in case there are no flat fields within flying distance upon reentry.

So I decided....why not parachute? My spaceplane isn't very heavy and several attempts land via parachute have been promising, but not great. I cut engines, use a drogue to slow down to a fairly slow speed and then deploy about 4 main chutes for the final descent. Unfortunately, depending on where I put the chutes, the plane will drift nose or tail first. A nose first approach and a water landing actually results in a fully recoverable aircraft with no damage, but not so much with tail first. Coming down on landare usually some damage but the crew survives.

Has anyone tried parachuting a space plane back to kerbin? I can't be the first person to have tried this and maybe someone has an idea how to properly center parachutes so the plane drifts down horizontally(instead of mostly vertical?)

I'll post pics tomorrow to help illustrate what I'm talking about

[mrclucks]

Have you tried parachutes on the nose and rear?

[DCWarHound]

It's possible to have parachutes to land a space plane but you will need to align them with your fuel tanks so it doesn't matter if they are full,empty or partially full.If you have cargo,you will either need to design it so it can either use parachutes with or without cargo,possibly having another action group for different payloads.

You can probably test it with a normal jet before using it on an SSTO.

[tbarcello]

Pàrachutes slightly behind CoM should work.

Khm .... RCS Alignment mod ... Khm

[Val]

...

The biggest issue I'm having is getting enough thrust and dV to get it to orbit. My intial idea of attaching via a radial decoupler to one of my standard rockets ended...pretty poorly and I've been trying with various combinations of boosters to get at least up to the upper atmosphere. I'm not even trying to think about SSTO yet. I just want something that can get to space, dock and return. Half the spaceplane stuff I've seen seems to be SSTO and I'm wondering if nobody does the "piggyback on a rocket method", so advice would be nice, or at least a pointer towards a good tutorial.

...

It is very hard to make a good piggy-back shuttle launcher, because of thrust alignment and moving Center of Mass.

Although it's from an older KSP version, there's a very good video from Scott Manley

.

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Has anyone tried parachuting a space plane back to kerbin? I can't be the first person to have tried this and maybe someone has an idea how to properly center parachutes so the plane drifts down horizontally(instead of mostly vertical?)

I'll post pics tomorrow to help illustrate what I'm talking about

The trick to parachutes on planes is making sure they are above where the CoM will be when you expect to deploy them. As always, CoM can move depending on your fuel load. You can either move fuel around to balance once you've deployed the parachutes, or do the much harder task of designing a craft that has CoM in the same place, both full and empty (Wet/Dry).

To help with that I can recommend RCS Build Aid. It's a plug-in for use in SPH and VAB, which among other things, can show both Wet and Dry CoM simultaneously, so you don't have to empty and fill all the tanks while building to see where Wet/Dry CoM is.

[ForScience6686]

Avoid piggy back or drop tank engines. Mount on top of rocket in a fairing. I use a rescue plane in this fashion so I can glide back to ksc. When placing parachutes, I go equal distance from com with no fuel left on board, as that is when it would be needed. Don't be afraid to overshoot ksc, just make a turn and approach from the other direction. I use this method when figuring out when to begin my descent from orbit. You have quite a bit of drag control with a plane to adjust your descent.

[The_Rocketeer]

I've built something that will fly, glide and land pretty decently during atmo tests but I haven't been able to get it to orbit yet to test re-entry.

The danger here is that what works in atmo won't necessarily work in space, for example a Boeing-747 airliner with rocket engines would just spin in circles if it ever made it to space because the CoT and CoM are out of alignment. As long as your CoT points directly away from your CoM you should be alright.

The biggest issue I'm having is getting enough thrust and dV to get it to orbit. My intial idea of attaching via a radial decoupler to one of my standard rockets ended...pretty poorly and I've been trying with various combinations of boosters to get at least up to the upper atmosphere.

If you can give us a screenshot it might help identify design issues you might be having. SSTOs are not as difficult as they might seem - this thread is full of 'simple' (some less so!) SSTOs that you can download and use, or just look at for design ideas. On the other hand, putting a small orbiter/glider on top of a rocket is also viable and fairly straightforward. Strut it all round and be careful of letting the control surfaces do too much of the steering on the way up (you might want to disable some of them).

I'm okay at landing on flat ground(haven't been able to return to the KSP runway yet) but frankly, I want an alternate abort mode just in case there are no flat fields within flying distance upon reentry.

Landing at KSC basically takes good timing and a little bit of piloting. For a spaceplane, you need to lower your periapsis to about 10km over the sea about half way between the KSC and the peninsula to the east. (You do this by making a retro burn at the exact opposite of this in your orbit). Then it's just a case of gliding in. RL shuttle astronauts practiced runway landings in sims dozens/hundreds of times before ever having to do it for real, so don't feel like a cheat if you use a quicksave to practice.

So I decided....why not parachute? My spaceplane isn't very heavy and several attempts land via parachute have been promising, but not great. I cut engines, use a drogue to slow down to a fairly slow speed and then deploy about 4 main chutes for the final descent. Unfortunately, depending on where I put the chutes, the plane will drift nose or tail first.

As others have said, your parachutes need to be placed symmetrically around your CoM so the drag they produce balances on the CoM in a similar way to the CoL. Mostly this is a case of best-guess eyeballing.

Another option is to use a stack separator to 'eject' the manned sections and just parachute them. Costly, but for an 'abort' situation, possibly the safest solution.

[DalisClock]

So here's pictures of my spaceplane as promised. Not the most original thing in the world but all I want it to do is go to LKO, dock with my space station and come back. I'll work on refining it once I get it working properly.

I've moved the parachutes around half a dozen times, this was just my latest attempt because the plane seemed to float down by the bottom this time.

[The_Rocketeer]

I see chutes on the CoM (fine) and chutes on the back of the wings, but nothing on the front of craft to balance against these. If you just deploy the ones on the CoM I'd expect it to descend nicely, but with those others it's bound to pitch down.

Also, with all your fuel mass draining from the back of the plane, the CoM will move even further forward, so then all the chutes will be behind it.

[GoSlash27]

DalisClock,

Here's a good discussion of the ins 'n' outs of piggyback- style launchers:

http://forum.kerbalspaceprogram.com/threads/132178-how-to-make-space-shuttle

Fair warning: They're much more difficult to make than SSTO spaceplanes.

Best,

-Slashy

[bigcalm]

I can see a couple of things wrong.

1) Those are terrier engines at the back? You want both air-breathing engines AND LF-OX engines. Your air-breathing engines get you up to a height of 20k and ~1000 ms, your LF-OX engines will get you from there to orbit. Or use RAPIER engines which can switch between the two modes.

2) The parachutes where they are will tip the nose forward. You want an equal amount of parachutes on the nose.

[Val]

I can see a couple of things wrong.

1) Those are terrier engines at the back? You want both air-breathing engines AND LF-OX engines. Your air-breathing engines get you up to a height of 20k and ~1000 ms, your LF-OX engines will get you from there to orbit. Or use RAPIER engines which can switch between the two modes.

2) The parachutes where they are will tip the nose forward. You want an equal amount of parachutes on the nose.

He's not building a SSTO spaceplane. It's a Shuttle type spaceplane.

[DalisClock]

I see chutes on the CoM (fine) and chutes on the back of the wings, but nothing on the front of craft to balance against these. If you just deploy the ones on the CoM I'd expect it to descend nicely, but with those others it's bound to pitch down.

Also, with all your fuel mass draining from the back of the plane, the CoM will move even further forward, so then all the chutes will be behind it.

That's one of the problems I've noticed. I've tried draining most of the fuel before deploying chutes(tanking off from the KSC runway and flying a little ways out to see drains the tanks nicely), but so far it hasn't worked. I'll try just deploying the ones over the COM and see if that works.

DalisClock,

Here's a good discussion of the ins 'n' outs of piggyback- style launchers:

http://forum.kerbalspaceprogram.com/threads/132178-how-to-make-space-shuttle

Fair warning: They're much more difficult to make than SSTO spaceplanes.

Best,

-Slashy

I'll take a look at this.

I'm seriously leaning towards either mounting the plane on top of a rocket or just trying for SSTO at this point. The shuttle concept seems much more trouble then it's worth.

[The_Rocketeer]

That's one of the problems I've noticed. I've tried draining most of the fuel before deploying chutes(tanking off from the KSC runway and flying a little ways out to see drains the tanks nicely), but so far it hasn't worked. I'll try just deploying the ones over the COM and see if that works.

...

I'm seriously leaning towards either mounting the plane on top of a rocket or just trying for SSTO at this point. The shuttle concept seems much more trouble then it's worth.

The key with arranging the parachutes is to use the dry CoM (the CoM when all the fuel is used/tanks are empty) and not the wet CoM (when the tanks are full). Without using mods, u can find this by manually setting the tanks to empty in the SPH/VAB (right click and reduce fuel bar to 0) and then seeing where the CoM ends up.

Then it's a matter of placing the parachutes around the CoM so it looks something like the '5' side of a dice, with all the chutes equidistant from the CoM in the centre. It doesn't need to be a perfect square, if the front chutes have to be close together that's fine so long as they're as far from the CoM.

It is more trouble than it's worth building a shuttle/piggyback launcher, if you don't find the process of developing the thing fun in itself. If you do, it can be one of the most rewarding things you can do in KSP!

Edited September 13, 2015 by The_Rocketeer
typo

[GoSlash27]

I'm seriously leaning towards either mounting the plane on top of a rocket or just trying for SSTO at this point. The shuttle concept seems much more trouble then it's worth.

DalisClock,

What The_Rocketeer said. If you just want a working spaceplane, a piggyback spaceplane is just about the worst way to do it. It's much easier to make an SSTO spaceplane.

The easiest design I've found for a vertical lift spaceplane is to sandwich the spaceplane between 2 boosters like this:

The drag of the tailplane and wings tends to stabilize the rocket this way. If you put the spaceplane on top of the stack, then you need more wings in the tail to make it stable.

Best,

-Slashy

[Vegetal]

Send pics of it with the launch vehicle attached (launch config).

With a shuttle so small you don't need a large and complicated launch vehicle. I have one that is just a single stack with a mainsail for main power, and 2 of those radial white engines at the nose, pointed in a way to neutralize the torque. This one doesn't even need thrust limiter correction to get to orbit, but that's a rare thing.

But making a piggy-back style plane IS harder than an SSTO spaceplane.

[DalisClock]

Send pics of it with the launch vehicle attached (launch config).

With a shuttle so small you don't need a large and complicated launch vehicle. I have one that is just a single stack with a mainsail for main power, and 2 of those radial white engines at the nose, pointed in a way to neutralize the torque. This one doesn't even need thrust limiter correction to get to orbit, but that's a rare thing.

But making a piggy-back style plane IS harder than an SSTO spaceplane.

I don't have one yet. I've been trying to build one that works and so far had really limited success.

I've also been dividing my KSP time between this and sending a series of landers to the Mun to form the core of a mining colony/base there. After some tinkering, I've managed to get most of my modules into a muner intercept trajectory but been having a hell of a time getting my rovers(a tranport/exploration/cargo rover and a drilling/ore storage rover) into orbit.

[ForScience6686]

Do you have fairings yet? Put a shell over that and strap it on a rocket with enough fins for control. I would also guess that you have to much wing on that small guy. Smaller wing will allow it to hit in a smaller shell and make it all much easier. I would do all designing with empty tanks as you don't plan on flying in atmosphere, just glide return correct? I have a very similar shuttle I could get you pictures of later on to compare. Or add me on steam to see them all, screen name For Science.

[Vegetal]

GoSlash's method simplifies the shuttle concept a LOT, I used it a lot myself.

It is a little more wasteful though, if you don't need that much power from 2 mainsails. You can then put a decoupler behind your shuttle with it, and fuel lines from the tanks, that way you just have one engine. It's a good method especially in career mode, as engines are expensive.

[Merandix]

Replace those LV909's with a single RAPIER, and I guess this plane will get you pretty darned close to getting to space/orbit already as an SSTO; on that point you're not far off. If you don't have RAPIERS yet, an SSTO doesn't need to be much bigger than this to work. However, you do need the turboramjets at minimum.

I have tried non-ssto rocket launched spaceplanes. I failed at them. Trust me on this one: SSTO's are actually easier.

Also, and that's my personal opinion which in no way should tell you how to play the game, but why build a plane if you launch it by rocket and land it by parachute? You're missing out on all the fun from flying planes. I mean, that moment you land your plane for the first time on the runway, and EACH time you land exactly centreline at KSP... Among others.

[DalisClock]

Replace those LV909's with a single RAPIER, and I guess this plane will get you pretty darned close to getting to space/orbit already as an SSTO; on that point you're not far off. If you don't have RAPIERS yet, an SSTO doesn't need to be much bigger than this to work. However, you do need the turboramjets at minimum.

I have tried non-ssto rocket launched spaceplanes. I failed at them. Trust me on this one: SSTO's are actually easier.

Also, and that's my personal opinion which in no way should tell you how to play the game, but why build a plane if you launch it by rocket and land it by parachute? You're missing out on all the fun from flying planes. I mean, that moment you land your plane for the first time on the runway, and EACH time you land exactly centreline at KSP... Among others.

The Rocket thing was because I thought SSTO was really hard, and I already know how to attach things to rockets(slapping boosters on a rocket is easy), so I figured how hard could it be? It turns out, really hard.

Parachutes was more of a lark for me, and because I wanted a backup option in case I wasn't gonna have a long flat piece of land to land on. I've never been able to hit the runway in KSP, let alone land at a pre-determined spot on an atmospheric planet(every time I've tried the drag pushes my landing spot down and I haven't done enough testing to figure out how to fix the problem). I've been trying to keep as many kerbals alive as I can.

But yeah, I think I'm gonna refocus on an SSTO. I actually swapped the LV-909s with RAPIERS and nearly got to orbit on my first try. Unfortunately, my oxider ran out before I completed my circulation burn, so I need to look solutions for that.

The parachute thing works now. I just put them really close together around empty CoM. So if I can figure out how to get the thing into orbit with some fuel/oxidizer to spare, I'll be good to go for now.

Edited September 15, 2015 by DalisClock

[Vegetal]

If you just used that same plane with 2 Rapiers, you are very overpowered. Just removing one of them could make it orbit. If not, and you said you were very close, just adding a little bit of extra fuel should make it.

If you want the possibility to field land the plane, consider using just one chute at the rear. You activate it as soon as you touch down, and it makes you stop very quickly. I used this method a lot in my survey plane.