i havent made any SSTOs since 1.0+ and i dont know how to do it now

[boxley]

in the old days it was all about intake spam pretty much, have as many intakes as possible to get as much speed from jets as possible and then you can jump into orbit easy enough, but this is totally different now.

I don't know what to do, drag still seems arbitrary, all jets have their thrust cut off at about 20,000 regardless of intake spam and the mk2 parts hold so little fuel that its honestly hard to make anything work. :T

are there new techniques for the concept now? ive done FAR which makes it easy enough but it seems like lack of fuel is the main problem now.

[Starhawk]

Check out this thread.

Also check out this tutorial.

There are many good examples in the Pro SSTO Builder/Pilot Challenge or in the K-Prize thread.

Happy landings!

Edited September 8, 2015 by Starhawk

[capi3101]

<snip /> ive done FAR which makes it easy enough but it seems like lack of fuel is the main problem now.

Which aero are you using these days?

Presuming you're talking about designing a spaceplane, you want to design it so that you've got roughly 1,800 m/s of delta-V during the rocket phase. This translates to roughly half the mass of your plane (or more) in fuel dedicated to that phase of the flight, depending on the efficiency of the rocket you're using. You're still good to go with a single Mk1 tank per Turbojet or RAPIER for the air-breathing portion of the flight (in fact, it was still good before it was redesigned to haul three times as much LF). Intake hogging is a thing of the past now - a single intake per engine will do just nicely, and there's really not much functional difference between the various intakes you might choose to work with.

There was a thread that went over guidelines just today; lemme put up a link. It'll help if you use stock air. If you use FAR, we can talk some more about guidelines - I fly FAR these days, but I like to keep abreast of what the stock fliers are going with.

EDIT: Starhawk beat me to posting the link by a good fifteen minutes. So in that regard...elderly ninja'd? Maybe? No?

Edited September 8, 2015 by capi3101

[Alshain]

So, pre-1.0 with FAR the method was to get up high (~25km), before intakes ran out and accelerate in the thin atmosphere to high speeds (1200m/s) before pulling back and switching to rockets. Even that isn't really possible anymore because the engines have changed to not have thrust at that altitude.

I've seen several suggestions. The one I see the most is basically the same as FAR but lower, you just have to put up with drag and heat at that level and you won't likely get 1200m/s. Even if you do, air breathing engines aren't as efficient so it doesn't save you much fuel that way.

I've gotten some small ones to orbit that way, I've also done it where the plane has a massive amount of Jet thrust so it is basically a jet assisted rocket with glide landing capabilities.

However, for the most part I've abandoned SSTO's. 1.0.4 has pretty much ruined them as far as I am concerned. My recommendation is learn to build shuttles, because while we have pretty much lost SSTOs, shuttles are much easier in the new aerodynamics package and we are getting a new engine for them in 1.1 as well (similar to the Badger in Ven's Stock Part Revamp).

[Starhawk]

EDIT: Starhawk beat me to posting the link by a good fifteen minutes. So in that regard...elderly ninja'd? Maybe? No?

I'm only 52! Not that elderly.

Happy landings!

[The_Rocketeer]

I'm only 52! Not that elderly.

Why is it old people always find it necessary to point out they're not that old?

[Starhawk]

Why is it old people always find it necessary to point out they're not that old?

When I was a teenager, 52 was practically death's door. I don't see it quite that way anymore and apparently feel the need to point it out.

Get off my lawn!

Happy landings!

[Alshain]

When I was a teenager,

You mean back when you walked to and from school in the snow uphill both ways?

(EDIT: I'm quickly approaching my 40's so I'm really not one to talk lol)

[FyunchClick]

I've seen several suggestions. The one I see the most is basically the same as FAR but lower, you just have to put up with drag and heat at that level and you won't likely get 1200m/s. Even if you do, air breathing engines aren't as efficient so it doesn't save you much fuel that way.

I've gotten some small ones to orbit that way, I've also done it where the plane has a massive amount of Jet thrust so it is basically a jet assisted rocket with glide landing capabilities.

I don't really see that. I've got a stock mk2 ssto, with a payload consisting of a cockpit, passenger cabin and MK2 inline docking port, that runs to almost mach5 around 20km if I start my run almost level at 10km (that's around 1400m/s I think). From there it's just a short rocket kick to orbit. Not as fast as you could get in 0.9 but then again I ran mach 7 with an ssto with an unshielded docking port as a nose there so that made no sense.

It's certainly not overpowered with a TWR that only goes over 1 when supersonic between 10 and 20km; it's got 3 rapiers to get 95% to orbit, and a single LV-N to get the rest of the way and have nearly 2km/s left to get to Mun or Minmus and back with ease. For fuel it's got a full pair of Big-S wings and strakes, an MK2 LF fuselage, and three MK1 LF fuselage, and for the rocket phase a short mk2 to 1.25 adapter and three flt400s, and air comes from 3 ram intakes. It even looks the parts of a supersonic jet.

Key for me was not to try and hug the edge of the atmosphere and squeeze every last m/s out of your airbreathing cycle as I did with pre 1.000, but build up your run between 10 and 20 km altitude and keep that momentum going on rockets as soon as the intakes cut out, then pitching up slowly as to not introduce to much drag.

Big ones aren't much harder, before this one I built a 160t MK3 with ISRU and all science equipment that flew out to Minmus for a refuel, and will go to Layte next transfer window. It gets to orbit with little trouble as well.

[GoSlash27]

So, pre-1.0 with FAR the method was to get up high (~25km), before intakes ran out and accelerate in the thin atmosphere to high speeds (1200m/s) before pulling back and switching to rockets. Even that isn't really possible anymore because the engines have changed to not have thrust at that altitude.

I've seen several suggestions. The one I see the most is basically the same as FAR but lower, you just have to put up with drag and heat at that level and you won't likely get 1200m/s. Even if you do, air breathing engines aren't as efficient so it doesn't save you much fuel that way.

I've gotten some small ones to orbit that way, I've also done it where the plane has a massive amount of Jet thrust so it is basically a jet assisted rocket with glide landing capabilities.

However, for the most part I've abandoned SSTO's. 1.0.4 has pretty much ruined them as far as I am concerned. My recommendation is learn to build shuttles, because while we have pretty much lost SSTOs, shuttles are much easier in the new aerodynamics package and we are getting a new engine for them in 1.1 as well (similar to the Badger in Ven's Stock Part Revamp).

haha you're too young to be this crotchety ya whippersnapper!

Why... back in my day we just puzzled out the changes and made it work! We went to orbit uphill both ways and we were thankful for what we had!

/ SSTO spaceplanes still beat the pants off of shuttles

// made both

/// get offa mah lawn

Best,

-Slashy

Edited September 8, 2015 by GoSlash27

[Merandix]

in the old days it was all about intake spam pretty much, have as many intakes as possible to get as much speed from jets as possible and then you can jump into orbit easy enough, but this is totally different now.

I don't know what to do, drag still seems arbitrary, all jets have their thrust cut off at about 20,000 regardless of intake spam and the mk2 parts hold so little fuel that its honestly hard to make anything work. :T

are there new techniques for the concept now? ive done FAR which makes it easy enough but it seems like lack of fuel is the main problem now.

You're likely overbuilding. You can get into space with fairly little fuel given an efficient design. I can promise you that as soon as you build your first one, you'll have a light-bulb turning on above your head.

It's also a bit more about flying now, though there are very simple designs around. Firstly, try to balance climb and acceleration. Up to about 5-6 km you will want to stay subsonic or transonic. In a lot of designs with lower TTW ratio's you then have to 'punch' through the transonic region. This sometimes even involves levelling off or dropping a bit in altitude! Ones the jets get their supersonic thrust boost, you can start climbing again. Maintain supersonic flight (doesn't matter if you hit mach 2) at around 10 km, then decrease rate of climb, and accelerate. Mostly 5-15 degree rates of climb, depending on how high your TTW is. You want to hit 1350-1450 m/s before kicking in the rockets, preferably at around 22 km, when your acceleration on airbreathers stops (maybe a little lower on turboramjets, I'm assuming RAPIERs here).

The rocket-stage will take a bit more fuel, but generally, I find that a typical Mk2 design is fairly easy to get up into space once you get the hang of it. I don't know about FAR, but stock has become a bit more challenging and a little harder. Don't count too much on interplanetary spaceplanes. They're certainly possible, but hard.

Proof that it's still doable: I'm a Kerbal all the way, I just eyeball it (with some rules in the back of my mind). No spreadsheets here. Basically, I'm an idiot at building rockets and spaceplanes. If I can do it, anyone can, provided a little research.

One thing that stood out to me is that at first you tend to overcompensate on the fuel, so your craft gets too heavy. Sometimes it helps recreating a simple design. Once you get the hang of it, it's as much fun as before!

[Sharpy]

So, pre-1.0 with FAR the method was to get up high (~25km), before intakes ran out and accelerate in the thin atmosphere to high speeds (1200m/s) before pulling back and switching to rockets. Even that isn't really possible anymore because the engines have changed to not have thrust at that altitude.

I can't tell much about FAR but in current stock the method is somewhat similar.

The air is thinner and the engines lose lots of thrust so high, so you accelerate at 10-15km instead of 25. You reach 1100m/s on turbojets or 1400m/s on rapiers, then climb - steepness depending on TWR of your chosen closed-cycle engines, and once air-breathers cease to accelerate you, you fire the rocket engines to bring apoapsis high enough and circularize.

If you choose only nukes as your rocket engines, your climb will be very shallow as you can't afford to lose lift and plunge into thicker atmosphere that will slow you down. With other engines you can afford more or less steep profiles that lift you above the atmosphere for long enough to circularize.

While thrust of jet engines was nerfed, it was only nerfed enough to match the new air density - they are about as efficient as they used to be, for all practical applications. One MK1 fuel tank per engine makes sense for a lengthy atmospheric flight after reentry - you'll hardly use up half the MK1 tank in air-breathing mode on ascent.

This is a tiny drone capable of SSTO flight, that uses just one turbojet and one nuke clipped into a single MK1 tank.

Flight profile:

Take off at 100m/s, hide the wheels, climb nearly vertically to 10,000, level down to some 20-30 degrees and keep going until your speed stops rising. Then fire the nuke and level down to some 10 degrees. Keep burning until you get the desired apoapsis, it takes a long while and even then needs some corrective burns before you escape the atmosphere.

That's the minimalistic core design of something that can achieve the orbit, return, and about nothing more. You take it from there - add other engines to shorten the ascent, add fuel and payload, cockpit, multiply the engines, play with wing profiles and so on. Lots of room for improvement, but this is the very skeleton to build upon.

[capi3101]

I can't tell much about FAR but in current stock the method is somewhat similar.

The air is thinner and the engines lose lots of thrust so high, so you accelerate at 10-15km instead of 25. You reach 1100m/s on turbojets or 1400m/s on rapiers, then climb - steepness depending on TWR of your chosen closed-cycle engines, and once air-breathers cease to accelerate you, you fire the rocket engines to bring apoapsis high enough and circularize. <snip />

A FAR ascent profile these days is pretty much the same as this - you get up to 10k as fast as you can manage, then level your flight out to 5-10 degrees above the horizon and begin accelerating; if you get heat warnings, you steepen up the rate of climb if you can. Turbojet engines will start losing significant power by 20,000 and will flame out in the neighborhood of 26,000; I typically switch over to rockets at 25k. Speed's still more important than altitude - case in point, the other day I launched a plane that got up to 25k but only going about 800 m/s; it ran out of fuel before making orbit. On the second attempt, I got it up to 1050 m/s at 19k and lit the rockets early - she made orbit with fuel to spare.

Big thing I've noticed between the two (stock and FAR) aero models is that FAR's actually kinder these days; the recommended maximum launch weight per engine these days for stock (as per the other thread) is about ten tonnes. With FAR, you can easily do 24-30 tonnes per jet engine. Plus you have all those nice, somewhat-more-than-mildly intimidating stability tools that tell you if your plane is gonna wig out on you or not...

[Sharpy]

http://i1031.photobucket.com/albums/y379/jorreholland/screenshot14_zpsejv2tqjv.png

I love how you clipped that cockit, but that ladder...

[Alshain]

I can't tell much about FAR but in current stock the method is somewhat similar.

The air is thinner and the engines lose lots of thrust so high, so you accelerate at 10-15km instead of 25. You reach 1100m/s on turbojets or 1400m/s on rapiers, then climb - steepness depending on TWR of your chosen closed-cycle engines, and once air-breathers cease to accelerate you, you fire the rocket engines to bring apoapsis high enough and circularize.

If you choose only nukes as your rocket engines, your climb will be very shallow as you can't afford to lose lift and plunge into thicker atmosphere that will slow you down. With other engines you can afford more or less steep profiles that lift you above the atmosphere for long enough to circularize.

While thrust of jet engines was nerfed, it was only nerfed enough to match the new air density - they are about as efficient as they used to be, for all practical applications. One MK1 fuel tank per engine makes sense for a lengthy atmospheric flight after reentry - you'll hardly use up half the MK1 tank in air-breathing mode on ascent.

This is a tiny drone capable of SSTO flight, that uses just one turbojet and one nuke clipped into a single MK1 tank.

https://dl.dropboxusercontent.com/u/3152580/sshots/2015-07-07_00012.jpg

That's the minimalistic core design of something that can achieve the orbit, return, and about nothing more. You take it from there - add other engines to shorten the ascent, add fuel and payload, cockpit, multiply the engines, play with wing profiles and so on. Lots of room for improvement, but this is the very skeleton to build upon.

OK, but look at the TWR on that thing. Why bother with wings? You have to ask yourself if you are really building a plane or a rocket that just looks like a plane. That is a jet assisted rocket, take the wings off and launch vertically, same result.

Edited September 9, 2015 by Alshain