Why don't my SSTOs work?

[Jeb&Bob]

Hi

I'm currently about 15 hours into the game and I am struggling a lot with SSTOs. I keep trying to build SSTOs based on youtube video ones, mostly using MK1 parts. However, they never reach space (and don't nearly get anywhere near!). I'm not the world's greatest pilot and I struggle to use Nerv engines when there is no air (When I tried to download one of Matt Lowne's 'easy' crafts. Does anyone have any advice on how I can get going with SSTOs?

Thanks

[OrbitalBuzzsaw]

Pics?

Build some planes first to get used to aerodynamics

[monstah]

6 minutes ago, OrbitalBuzzsaw said:

Build some planes first to get used to aerodynamics

I agree! When I read your thread, the first thing I thought was:

26 minutes ago, Jeb&Bob said:

I'm currently about 15 hours into the game

There's your problem. SSTOs are (probably; some may disagree with me) the single hardest thing to do in this game. If you see videos of someone flying a SSTO in KSP and they make it look easy, just remember that most forum users are 100+ hours into the game, and many are at 1000+ or way more.

Which is not saying you should give up. Just keep playing, fly planes, master landing, master space, and, before you notice, you'll be a hundred-hour flying monster.

Myself, I'm at 1500 hours and I can't SSTO    I don't try to get better, tho, it's not my thing. If you keep trying you'll get there.

One thing I noticed tho; you mention you're using Mk1 parts. You're using jet engines first, and switching to rockets only when in space, right? Rockets are fuel-hungry, jets are more efficient and better to accumulate speed at lower altitudes. You'll need to get fast.

[Jeb&Bob]

Thanks so much

My friend managed to make and fly an SSTO 23 hours into the game. So far, I've only built planes and they are easily able to land and fly. I'm pretty confident with aerodynamics so far. I'd like to post pics but my rubbish mac is unable to do screenshots, even when I use the correct command (Cmd+Shift+3). And I use jet engines first, then Nerv engines, and I get to around 1000 km/h before switching. I try to follow guides on YT but they never work for me. 

 

[monstah]

6 minutes ago, Jeb&Bob said:

and I get to around 1000 km/h before switching.

Hm, that's not even sound barrier yet. Try more/more powerful jet engines for the air breathing phase.

Also, NERVAs are pretty heavy, and they lack the "OOMPH!" you'll want. They're good for hauling cargo from orbit to orbit, but not to reach orbital speed before you fall back down. Perhaps the 'easy craft' you downloaded is from a different version of KSP? Engine performance and aerodynamics have been adjusted here and there.

I think you need MORE POWER, both in the air breathing stage and in the vacuum stage (try some good ole' Reliants there, instead of NERVAs?).

[ScriptKitt3h]

As of now, you really want to start small with SSTOs, and work your way up to larger designs as time goes on.

In addition, understanding how the current stock aero models drag and so on will GREATLY improve your designs, as I've learned firsthand myself after not playing KSP in a while. An SSTO can look sleek on the outside, but it non-occluded parts inside the body are causing massive levels of drag while in-flight, it's not going to be a successful design.

Also, RAPIERs are by and far the best engine design for SSTOs (not the only viable option, but the simplest to implement and fly with), especially due to their massive power increase at high speeds.

[Jeb&Bob]

WOW. This forum is helpful. Thanks everyone for your advice so far! I'll post a craft that should be SSTOish soon, but i'm hugely grateful for the help so far.

[MKellerBR]

You have to consider that the game had great changes in the physics definitions, in the last updates.
Try to build on the craft of SSTOs made for version 1.2.x!

Many videos and tutorials made up to version 1.1.0 do not work correctly in 1.2.x

 

[Freds]

FAR and MK2 Expansion are a must-have for SSTO - The Sledgehammer' Air-Augmented Ramrocket in the expansion is very nice once you reach Mach 2.5 as 11000M.

First try to master aircraft design, then build a simple spaceplane, with droptanks for extra fuel, and, finally, go for full SSTO.

Almost all my designs are spaceplanes with droptanks - some of them are able to reach orbit without dropping the tanks, but with almost no DV left. If the mission is for Kerbin Orbit, the cost of 2 FL-T800 + decoupler are  almost nothing given the benefits, so, its pointless to have a SSTO in Kerbin orbit.

 I only use full SSTO for Laythe missions, so i can refuel in orbit and go for laythe again, but, in this case, the ship must be designed have enough fuel for  deorbit, travel, land and return to orbit (sounds dificult, but in laythe is very easy to get to orbit).

 

[Tex_NL]

5 minutes ago, Freds said:

FAR and MK2 Expansion are a must-have for SSTO

Complete and utter bull crap! FAR and Mk2X might make it easier but neither of them is a must-have. Stock SSTO's are still very much possible.

5 minutes ago, Freds said:

Almost all my designs are spaceplanes with droptanks

Purely by definition a plane that drops tanks is NOT an SSTO.

Edited December 20, 2016 by Tex_NL

[Freds]

23 minutes ago, Tex_NL said:

Complete and utter bull crap! FAR and Mk2X might make it easier but neither of them is a must-have. Stock SSTO's are still very much possible.

its your opinion X my opinion. There is even a sample SSTO included in the game (i think is the aries... dont remember now).

I prefer MK2X and FAR, you prefer stock. One can simply put a big fuel tank, a big engine and a MK1 cockpit and lots of parachutes and call it SSTO..... 

"Purely by definition a plane that drops tanks is NOT an SSTO.". Ok, but, if the plane can reach orbit without dropping the empty tanks, can it be considerated an SSTO?

Edited December 20, 2016 by Freds

[Tex_NL]

25 minutes ago, Freds said:

its your opinion X my opinion. There is even a sample SSTO included in the game (i think is the aries... dont remember now).

I prefer MK2X and FAR, you prefer stock. One can simply put a big fuel tank, a big engine and a MK1 cockpit and lots of parachutes and call it SSTO.....

No, this is not a matter of opinion. You say it is a 'must-have' As in 'it is vital' or 'you must have it otherwise you can not do it.' I use neither FAR nor Mk2X and still I build SSTO. Therefore your statement simply can not be not true.
And if YOU can not build SSTO's without FAR or Mk2X that's YOUR shortcoming. Do NOT assume your shortcomings are true for everybody else.

25 minutes ago, Freds said:

"Purely by definition a plane that drops tanks is NOT an SSTO.". Ok, but, if the plane can reach orbit without dropping the empty tanks, can it be considerated an SSTO?

SSTO: Single Stage To Orbit. If it does not stage off anything (like tanks and or engines) and reaches orbit then by definition it is an SSTO. No matter if it CAN reach orbit on a single stage, as soon as it drops anything, by definition it is no longer a SINGLE Stage To Orbit.

Edited December 20, 2016 by Tex_NL

[Freds]

I got your point. now i see that i should have wrote "Should" instead of "Must" ^^ Let's not fight due to a grammatical error

[Slam_Jones]

You would have liked 0.90... or as I like to think of it, the Halycon days of SSTOs (basically before they changed the aero).  Those were the days you could get up to 2000m/s on jet engines alone, and finalize with a tiny chemical engine.   Far from realistic, sure, but heck, I thought it was fun

However, these days, they are much harder.  I honestly haven't made an (efficient) SSTO yet in the newest version, as I always end up with too little fuel, or not enough speed.

Either way, if you can master SSTOs, then you will make a lot of progress!  Good luck to you!

Edited December 20, 2016 by Slam_Jones

[Rune]

12 hours ago, monstah said:

I agree! When I read your thread, the first thing I thought was:

There's your problem. SSTOs are (probably; some may disagree with me) the single hardest thing to do in this game. If you see videos of someone flying a SSTO in KSP and they make it look easy, just remember that most forum users are 100+ hours into the game, and many are at 1000+ or way more.

Which is not saying you should give up. Just keep playing, fly planes, master landing, master space, and, before you notice, you'll be a hundred-hour flying monster.

Myself, I'm at 1500 hours and I can't SSTO    I don't try to get better, tho, it's not my thing. If you keep trying you'll get there.

One thing I noticed tho; you mention you're using Mk1 parts. You're using jet engines first, and switching to rockets only when in space, right? Rockets are fuel-hungry, jets are more efficient and better to accumulate speed at lower altitudes. You'll need to get fast.

Well, I am one of those forum monsters, having played at this game for literal years, but I would still say SSTOing is not impossible for "newbies", if they ask a bit around and approach the subject with some scientific mindset and stamina. Basically, try to figure out what is going on and what the indicators mean, and be prepared for a lot of trial and error, and you can't go wrong! I know I had a bit of a leg up because of my studies, but I got into SSTOs fast.

9 hours ago, ScriptKitt3h said:

As of now, you really want to start small with SSTOs, and work your way up to larger designs as time goes on.

In addition, understanding how the current stock aero models drag and so on will GREATLY improve your designs, as I've learned firsthand myself after not playing KSP in a while. An SSTO can look sleek on the outside, but it non-occluded parts inside the body are causing massive levels of drag while in-flight, it's not going to be a successful design.

Also, RAPIERs are by and far the best engine design for SSTOs (not the only viable option, but the simplest to implement and fly with), especially due to their massive power increase at high speeds.

Hear hear! There is a lot of stuff to be said about SSTOs, but there are really only three things to have in mind under 1.2 rules:

-The engine for SSTOing is the RAPIER. Accept no substitutes. Nukes are fine if you want to go farther, but nothing beats the payload fraction of a RAPIER design. RAPIER=easiest=most efficient (in stock).

-The flight path for the engine is crucial. With a RAPIER, you basically want to do a straight line to orbit, pitching up/down only slightly, or not at all (10º over the horizon is climbing rapidly if your speed is 1,000m/s, and kerbin curves under you), and getting to ~400m/s near sea level, in order to "wake up" the engines.

-Sleek, sleek, sleek. For a winged SSTO, drag is your single worst enemy. Things that create lots of drag: unused nodes, not-pointy parts sticking out of cargo bays, intakes. Have as few intakes as you can get away with, as few nosecones, and absolutely no uncapped nodes.

 

Rune. The rest is just making a plane that flies and figuring fuel/payload ratios by trial and error.

Edited December 21, 2016 by Rune

[Vanamonde]

I'm currently about 4.5 years into the game and I am struggling a lot with SSTOs. 

[sardia]

This is a 100% stock craft 3 engine SSTO.  Note the features or lackthereof that the posters above describe. No unnecessary draggy stuff like RCS, or tails, or ladders.  I focused on minimizing drag first, then the TWR. There's options for this craft, you could either increase the cargo capacity, or fuel, or lighten the craft. It doesn't really need the 2 shock cones, I just did it because that cockpit has the most heat resistance.  There's plenty of room for improvement here.

Note below the high Thrust to weight ratio. Note how I kept my center of lift inside the center of weight.   This is a little unusual since I have so much more engine power than normally is expected.  The flight profile is to take off, nose up 45 degrees, and light up the nerva engine once the speed stops increasing.

Spoiler

 

If you need a little more oomph to get you into orbit with a SSTO, I recommend getting the mod KR&D. It lets you increase marginally the performance of any and all parts in your space program.

 

Edited December 21, 2016 by sardia
elaborated details.

[Rune]

11 hours ago, Vanamonde said:

I'm currently about 4.5 years into the game and I am struggling a lot with SSTOs. 

Which is something that has always weirded me out, since you are a veteran that understands that rocketry is all about ratios.

Let me throw a few numbers to help you next time: A balanced RAPIER design has around 0.5-0.7 TWR (going by KER or the static thrust), and it is about equal parts payload (the payload could always be extra fuel and/or high Isp propulsion systems for extended range, of course), fuel for the ascent (around ~400kgs per RAPIER of LF for the airbreathing part, and the rest plain LFO), and everything else (engines, wings, cargo bay, control point, landing gear and miscellaneous systems like docking stuff).

Other than that, build a sleek plane that looks awesome, and follow the right path to orbit. That last bit is important, RAPIERS are easy as dirt to fly, if you only remember to skim the surface until you get them into their operating speed. With the right TWR (~0.5) and a slight positive angle off the runway, you can actually manage an input-free ascent, just pushing buttons while SAS flies you to orbit.

 

Rune. That last bit is kind of a pain in the ass to engineer, so something to strive for.

Edited December 21, 2016 by Rune

[Tex_NL]

10 hours ago, Vanamonde said:

I'm currently about 4.5 years into the game and I am struggling a lot with SSTOs. 

When it comes to SSTO planes you're probably a lot like me. They need to look plausible in real life AND be useful.

There are plenty of examples all over the forum but for me they all trigger the same responds: 'You build a nice plane but what does it do? Yes, it can get to orbit but it can't DO anything. It doesn't carry cargo. It doesn't carry science equipment (or VERY little). It can't transfer crew since it doesn't have a docking port. All you've build is an inefficient way to burn fuel. A very elaborate and expensive piece of orbital debris.'
And, no offence, @sardia's little critter two posts up falls square in the middle of that category. It can go up. It can come down. That's it. Completely useless. (Again sardia, nothing personal. It's just that your craft is the easiest and quickest example.)
Just building an SSTO is pretty easy. Building a useful SSTO plane can be hard.

Edited December 21, 2016 by Tex_NL

[sardia]

20 minutes ago, Tex_NL said:

When it comes to SSTO planes you're probably a lot like me. They need to look plausible in real life AND be useful.

There are plenty of examples all over the forum but for me they all trigger the same responds: 'You build a nice plane but what does it do? Yes, it can get to orbit but it can't DO anything. It doesn't carry cargo. It doesn't carry science equipment (or VERY little). It can't transfer crew since it doesn't have a docking port. All you've build is an inefficient way to burn fuel. A very elaborate and expensive piece of orbital debris.'
And, no offence, @sardia's little critter two posts up falls square in the middle of that category. It can go up. It can come down. That's it. Completely useless. (Again sardia, nothing personal. It's just that your craft is the easiest and quickest example.)
Just building an SSTO is pretty easy. Building a useful SSTO plane can be hard.

Very true. I use ssto for the same purpose that slashy does, a CHEAP way to get kerbals into orbit. 'a glorified school bus'. With some op mods, I can justify action beyond low kerbin orbit, but that's really a stretch. That's the easiest, and most common use. The original poster needs to learn to walk before he runs a space plane to lathe. 

You don't use EVA to transfer or rescue kerbals?

I'm not a fan of using a space plane for docking, because it requires draggy rcs. I suppose I could mess around with the uni directional RCS. Heard those are less draggy. 

Edited December 21, 2016 by sardia

[Tex_NL]

17 minutes ago, sardia said:

You don't use EVA to transfer or rescue kerbals?

OK, you've got me there. I wasn't thinking about rescue contracts at that moment.

17 minutes ago, sardia said:

I'm not a fan of using a space plane for docking, because it requires draggy rcs.

Properly placed RCS ports will only add a very small amount of drag.
Again with your craft as an example add a single RV-105 RCS Thruster Block  and a single Place-Anywhere 7 Linear RCS Port on each side of the CoM. (You can even clip them inside each other to make a nice looking 5way RCS port.) The torque from the cockpit should be enough to hold you steady and monoprop contained within it should suffice for docking if you know what you're doing.
If you need more monoprop add a single Stratus-V Roundified Monopropellant Tank. A MK2 Drone Core is great when you need more torque with the added benefit of extra electricity and full probe control.

Edited December 21, 2016 by Tex_NL

[Rune]

1 hour ago, Tex_NL said:

When it comes to SSTO planes you're probably a lot like me. They need to look plausible in real life AND be useful.

There are plenty of examples all over the forum but for me they all trigger the same responds: 'You build a nice plane but what does it do? Yes, it can get to orbit but it can't DO anything. It doesn't carry cargo. It doesn't carry science equipment (or VERY little). It can't transfer crew since it doesn't have a docking port. All you've build is an inefficient way to burn fuel. A very elaborate and expensive piece of orbital debris.'
And, no offence, @sardia's little critter two posts up falls square in the middle of that category. It can go up. It can come down. That's it. Completely useless. (Again sardia, nothing personal. It's just that your craft is the easiest and quickest example.)
Just building an SSTO is pretty easy. Building a useful SSTO plane can be hard.

I completely and heartily disagree. I launch way more SSTOs than anything else, since they are the cheapest way to put stuff in orbit in stock, reliably. Only when somethign doesn't fit the cargo bay of a Claymore do I consider slapping chemical rocket SSTOs to the sides. Granted, not easy at the level I do it, because I have been doing this basically forever. But building a Big Red SSTO is just a matter of knowing it takes about six RAPIERs, and following the rules I laid, and should be something anyone could do if their put their mind to it and seek some guidance when they hit snags. Here, some examples of incredibly useful SSTOs that take roughly 1/3rd their takeoff weight (usually quite a bit more) to orbit. Note that the Claymore is leaving that station after dropping about 45mT of ore fuel, some commsats, and a few other odds and ends:

And just to show that there is another whole kind of SSTOs that people totally disregard (we should have been saying airbreathing SSTOs all along), this is nowhere as cheap, but still cheaper than a disposable rocket:

 

Rune. Mostly what it takes is the desire to do it.

 

Edited December 21, 2016 by Rune

[Kryten 2X4B 523P]

Im nowhere near Rune's level at dealing with spaceplanes, but Im at the point where theyre usable to launch sats / interplanetary probes for nearer bodies, or crew transfer / recovery. As Rune has said, its all about ratios, as I found with trial and error.

If you really want to go through the process, start with a single rapier powered craft, keep it minimal and when youre successful, work out the ratios of lift  / mass & fuel per rapier, and go from there.

My latest career isnt at that level yet, but when I tested this design in 1.2 pre, it performed even better than in 1.1.3

[Vanamonde]

I think my issue is more a matter of piloting ascent profiles than craft building, but yes, I only wanted to make planes that can actually do something useful, not just go up and come back down.  

[Jarin]

16 hours ago, Rune said:

 Things that create lots of drag: unused nodes, not-pointy parts sticking out of cargo bays, intakes. Have as few intakes as you can get away with, as few nosecones, and absolutely no uncapped nodes.

No longer true for intakes. Data from testing here shows that shock cones and other intakes are among the least draggy nose components; regardless of open or closed. (for a while the shock cone was apparently better than anything else, but it's now on par with other nosecones)

Not that airhogging does you any good anymore, so there's no reason to spam intakes or anything. But they're not something that needs to be avoided, either.

Edited December 21, 2016 by Jarin