My first SSTO

[Azimech]

I've decided to learn the art of SSTO building. This is my first one. Yes, it's a taildragger.

The only control input needed: SAS, throttle up, engage engines, raise gear and cut throttle when you reach your desired apoapsis. After that circularise as usual.

It's got enough Delta-v to reach LKO only. Certainly not the most efficient SSTO but we all got to start somewhere. Action group 1 toggles the engines, action group 2 toggles between engine modes.

It's easy to fly and land, both with tanks full and nearly empty. Doesn't even need extra reaction wheels and has no struts. Mass: 25t. Parts: 35.

Action group 3 toggles the flaps, they're meant to point up. Touchdown can be a mere 25m/s, usually I just stall it above the runway and drop it.

Download link: https://kerbalx.com/Azimech/77I--My-First-SSTO

 

Edited November 30, 2016 by Azimech

[Frank_G]

Nice first build, congratulations!

Do you have an action group to close the air intakes? Closing them reduces drag on your way up and helps saving delta V.

[Azimech]

42 minutes ago, Frank_G said:

Nice first build, congratulations!

Do you have an action group to close the air intakes? Closing them reduces drag on your way up and helps saving delta V.

Thanks! AFAIK they've changed the mechanics on air intakes, the difference in drag is gone now, closing just prevents them from overheating.

[Dafni]

Its a nice looking craft, well done! Looking forward to see what other SSTOs you will come up with, as I am already a big fan of your other creations.

[Frank_G]

2 hours ago, Azimech said:

Thanks! AFAIK they've changed the mechanics on air intakes, the difference in drag is gone now, closing just prevents them from overheating.

I didnt know that. Thanks for pointing me there!

[OrbitalBuzzsaw]

Huh. Lose the tail connectors, go with more LF tanks and 2 nukes. Then you might be able to go to Minmus and back if you also make the big Mk2 tank LF only and use nukes to circularize. Also, shock cones are better than ramscoops and you don't need those radial intakes. Also, that tailplane is really draggy, SSTOs usually should be tailless. And have solar panels.

Edited November 30, 2016 by OrbitalBuzzsaw

[Azimech]

4 minutes ago, OrbitalBuzzsaw said:

Huh. Lose the tail connectors, go with more LF tanks and 2 nukes. Then you might be able to go to Minmus and back if you also make the back half Mk2 tank LF only and use nukes to circularize. Also, shock cones are better than ramscoops and you don't need those radial intakes. Also, that tailplane is really draggy, SSTOs usually should be tailless. And have solar panels.

Thanks for the advice. Nukes are on my list, at some point even ion engines. The control surfaces on the tail ... I'd like to keep them. I always have a lot of control authority on my planes.

[OrbitalBuzzsaw]

Just now, Azimech said:

Thanks for the advice. Nukes are on my list, at some point even ion engines. The control surfaces on the tail ... I'd like to keep them. I always have a lot of control authority on my planes.

Don't use Ions unless you are TurboPumped. Use the Tail Fins instead of the BigS elevons

[Azimech]

10 minutes ago, OrbitalBuzzsaw said:

Don't use Ions unless you are TurboPumped. Use the Tail Fins instead of the BigS elevons

Turbopumped? With rocket engines? The ions would only make sense in space anyway, I already tried. Better fuel economy when using together with fuel cells than the nukes but ... the patience involved.

I wonder if the tail fins will survive re-entry or even 1400m/s in lower atmosphere. I've chosen these parts because they're all in the 2400-2500K range while a lot of other parts have a max between 1200-2000K. On the other hand ... aerobraking in the upper atmosphere is easier than ever.

[OrbitalBuzzsaw]

Just now, Azimech said:

Turbopumped? With rocket engines? The ions would only make sense in space anyway, I already tried. Better fuel economy when using together with fuel cells than the nukes but ... the patience involved.

I wonder if the tail fins will survive re-entry or even 1400m/s in lower atmosphere. I've chosen these parts because they're all in the 2400-2500K range while a lot of other parts have a max between 1200-2000K. On the other hand ... aerobraking in the upper atmosphere is easier than ever.

TurboPumped is a youtuber who makes tiny SSTOs, sorry. The Tailfins are reentry capable, last I checked (1.13)

[septemberWaves]

Wait, did you say that this plane practically flies itself to orbit? And this is your first SSTO? That's one of the most incredible things I've seen on these forums lately. I don't know how you had the patience to make it semi-autonomous, that's difficult enough with rockets.

[Majorjim!]

Just now, eloquentJane said:

Wait, did you say that this plane practically flies itself to orbit? And this is your first SSTO? That's one of the most incredible things I've seen on these forums lately. I don't know how you had the patience to make it semi-autonomous, that's difficult enough with rockets.

LOL, at no point in the OP did he say it practically flies itself to orbit..

8 hours ago, Azimech said:

This is my first one.

Not bad for a first attempt dude. It's ugly as hell though, but most first SSTOs are! I'm happy to see you are starting to actually build flying stuff rather that things that have to be hyper edited into orbit.

[septemberWaves]

6 minutes ago, Majorjim! said:

LOL, at no point in the OP did he say it practically flies itself to orbit..

" The only control input needed: SAS, throttle up, engage engines, raise gear and cut throttle when you reach your desired apoapsis. " That is practically flying itself to orbit, as far as spaceplanes go. Or at least flying itself as far as a useful apoapsis.

Edited November 30, 2016 by eloquentJane

[Azimech]

6 minutes ago, eloquentJane said:

Wait, did you say that this plane practically flies itself to orbit? And this is your first SSTO? That's one of the most incredible things I've seen on these forums lately. I don't know how you had the patience to make it semi-autonomous, that's difficult enough with rockets.

Ehm ... 5, maybe 6 retries. Using a taildragger helps a lot, I've noticed this because I tend to build taildraggers a lot, my turboprops need it or I'll get a prop strike. The fun part is: if you don't touch the controls before taking off, the SAS will do it's best to keep the initial angle the same. Once you touch the controls yourself, all kinds of nasty things start to work. Suddenly you need to worry about vibrations (especially with turboprops!) and other stuff, and you end up controlling your crate all the way.

It's like the SAS says to us: "Leave it to me, I know what is best."

But after touching the controls it's like: "You didn't trust me. You're a douche. I'm not going to invest any more of my CPU cycles, you're on your own." and after that it's like controls are given to some 5 year old who's happy to help daddy.

Oh dear ... I think I've had too much of some dark-red coloured beverage already. It's 21:30 over here guys, don't worry.

[septemberWaves]

2 minutes ago, Azimech said:

if you don't touch the controls before taking off, the SAS will do it's best to keep the initial angle the same.

I have never thought about this before. I'm going to have to look into using taildragger designs for SSTOs. I thought initially that the downwards-angled wings (relative to the body) might make it a bit of a pain to fly, though with that explanation they make a lot of sense.

Or are they downwards-angled? The first image makes them look like they are, but the last image makes it look like they're aligned with the body of the plane.

Edited November 30, 2016 by eloquentJane

[Azimech]

 

9 minutes ago, eloquentJane said:

I have never thought about this before. I'm going to have to look into using taildragger designs for SSTOs. I thought initially that the downwards-angled wings (relative to the body) might make it a bit of a pain to fly, though with that explanation they make a lot of sense.

Wait ... uhm ... my wings are anhedral?

I must admit, I don't fully understand "downwards-angled wings (relative to the body)" because the wings on mine are straight.

 

Ah ... edit. Yes, optical illusion. I've had Dutch Roll in the past. Don't like it very much :-)

Edited November 30, 2016 by Azimech

[septemberWaves]

What I mean is that in the first picture it appears that the body of the plane is pointing up, whilst the wings are level with the runway. It could be an optical illusion though, due to the shape of those large wing segments.

Edited November 30, 2016 by eloquentJane

[Majorjim!]

Just now, eloquentJane said:

" The only control input needed: SAS, throttle up, engage engines, raise gear and cut throttle when you reach your desired apoapsis. " That is practically flying itself to orbit, as far as spaceplanes go. Or at least flying itself as far as a useful apoapsis.

LOL I do see what you mean, although you must not have flown many SSTOs these days. Getting them up is so easy now.

 

Just now, Azimech said:

Ehm ... 5, maybe 6 retries.

Huh? Retires at setting SAS and sitting back letting it fly into orbit? As what you are saying implies input after take off which may imply an inefficient ascent if so. If not, what's to try?

 I don't follow your SAS comments, go to bed, you are incoherent. 

[Azimech]

22 minutes ago, Majorjim! said:

LOL, at no point in the OP did he say it practically flies itself to orbit..

Not bad for a first attempt dude. It's ugly as hell though, but most first SSTOs are! I'm happy to see you are starting to actually build flying stuff rather that things that have to be hyper edited into orbit.

I have a torrent of new things coming, today I celebrated my 200th upload to KerbalX so I decided I'd go to space again for a little while. And they all have their own launch vehicles.

[septemberWaves]

1 minute ago, Majorjim! said:

LOL I do see what you mean, although you must not have flown many SSTOs these days. Getting them up is so easy now.

Not in 1.2.x, no. I've been working more on shuttles lately, since they are better suited to my early-game and early-mid-game infrastructure, and therefore I need them to work sooner. Speaking of which, I'll be launching one soon in my career thread as soon as I can get the docking system properly figured out.

[Majorjim!]

Just now, Azimech said:

I have a torrent of new things coming, today I celebrated my 200th upload to KerbalX so I decided I'd go to space again for a little while. And they all have their own launch vehicles.

Glad to hear it. You have wayyy too much free time dude..

[Azimech]

12 minutes ago, Majorjim! said:

LOL I do see what you mean, although you must not have flown many SSTOs these days. Getting them up is so easy now.

 

Huh? Retires at setting SAS and sitting back letting it fly into orbit? As what you are saying implies input after take off which may imply an inefficient ascent if so. If not, what's to try?

 I don't follow your SAS comments, go to bed, you are incoherent. 

Oh no it's much simpler than that. Just moving the landing gear a bit up or down so it won't splash when driving off the runway, and won't climb too fast so the Rapiers can't achieve max thrust. A pitch angle between 2 and 2.5 seems to be okay.

 

Who ara yoi celling incahurent? *HipS*

8 minutes ago, Majorjim! said:

Glad to hear it. You have wayyy too much free time dude..

I build fast

With my current job ... easy. The next one ... bit more difficult but okay, my best friend and I seem to have to create an internal revolution over there. Yes, I've got the job but boy ... they're slow with the paperwork!

Somewhat different:

Won't happen but I wouldn't mind working for Squad.

 

10 minutes ago, eloquentJane said:

Not in 1.2.x, no. I've been working more on shuttles lately, since they are better suited to my early-game and early-mid-game infrastructure, and therefore I need them to work sooner. Speaking of which, I'll be launching one soon in my career thread as soon as I can get the docking system properly figured out.

Docking system? Got problems with that?

Edited November 30, 2016 by Azimech

[Rune]

2 hours ago, Azimech said:

Ehm ... 5, maybe 6 retries. Using a taildragger helps a lot, I've noticed this because I tend to build taildraggers a lot, my turboprops need it or I'll get a prop strike. The fun part is: if you don't touch the controls before taking off, the SAS will do it's best to keep the initial angle the same. Once you touch the controls yourself, all kinds of nasty things start to work. Suddenly you need to worry about vibrations (especially with turboprops!) and other stuff, and you end up controlling your crate all the way.

It's like the SAS says to us: "Leave it to me, I know what is best."

But after touching the controls it's like: "You didn't trust me. You're a douche. I'm not going to invest any more of my CPU cycles, you're on your own." and after that it's like controls are given to some 5 year old who's happy to help daddy.

Oh dear ... I think I've had too much of some dark-red coloured beverage already. It's 21:30 over here guys, don't worry.

Yeah, that's a plane with a lot of control authority and not enough rigidity in the longitudinal axis, then SAS can be a handful because your controls can invert/overcorrect when the torque on the plane is big enough. In those cases, lowering your control input will usually help. Another thing that helps is a CoL very close to the CoM, so the control torque can be kept to a minimum (you also save on drag quite a bit). Of course, for that you need a CoM that either stays in place or moves forward, but with the new fuel flow rules that is easy to do.

As to the SSTO, nice-looking first try. Now go about finding the limits! Payload fraction, dV on orbit, lowest drag... that kind of stuff. Oh, and a couple of tips:

Tip#1: shock cones have the least drag per intake area, and a single of those can feed two RAPIERs. Less intake area=less drag. Drag is king in SSTOs.

Tip#2: With enough streamlining, 0.4~0.5 TWR designs can perfectly well go supersonic at sea level in less than a minute and basically run a straight line to orbit form there. And of course, low TWR=low engine mass=more mass for other stuff.

2 hours ago, eloquentJane said:

I have never thought about this before. I'm going to have to look into using taildragger designs for SSTOs. I thought initially that the downwards-angled wings (relative to the body) might make it a bit of a pain to fly, though with that explanation they make a lot of sense.

Or are they downwards-angled? The first image makes them look like they are, but the last image makes it look like they're aligned with the body of the plane.

Taildragging is just letting him settle into a climb without touching SAS on takeoff, meaning the plane never goes outside of it's neutral point and it applies less control torque in a steadier fashion. Which lets him get over the real issue, which is that the plane has too much control authority for its rigidity, and starts 'swimming' like a salmon as soon as you apply serious control input, throwing SAS into disarray. A solid, stable-but-not-too-much design with just enough control authority to turn a few º/s, and most importantly enough structural rigidity, and you'll actually be able to maneuver with ease, which is much better.

 

Rune. It's an entertaining rabbit hole you got yourself into.

Edited November 30, 2016 by Rune

[septemberWaves]

2 hours ago, Azimech said:

Docking system? Got problems with that?

No, I just needed to figure out what was best for my shuttle design. I got it working though.

This shuttle is designed as a low-tech crew transport for my long-term career, hence the low-tech docking system and general low-techiness of the vehicle. It was actually planned to work in conjunction with the Janus 4, but I can work with what I have. I prefer the shuttle anyway despite its lower crew capacity - it even works with MechJeb's autopilot, which made the launch vehicle an enormous pain to configure correctly.

[Azimech]

My second SSTO. This one has a small cargo bay and can land on Minmus and back at KSC. Same procedure as the other one except I need to press one key extra: switch from Rapiers to nuke.

After parking I had 82 units of fuel left. Haven't tried with cargo yet. And I need a lot of radiator panels with this cockpit.