There's no way for this SSTO to get into orbit, is there?

[XOIIO]

So, I've been trying to make a decent looking and functional SSTO for a long time, this is quite satisfactory, however, with the LV-N it just seems impossible to get it into orbit. It would be great for decent range operations but the jets can only get it so high, and it's far to weak to get into orbit itself (though I suck at flying them anyways). I tried with RAPIERs but they have so much little thrust it takes ages to get up to 100,/s, and would take way, way longer to get into the damn orbit.

I'm guessing it's just not feasible for a craft without four engines to get an LV-N into orbit :/

edit: there we go.

Also. Got it close to circularization, barely any fuel left, and got this annoying fking bug where the cockpit stays solid and the rest of the ship moves, it happens on multiple ships and is a real pain in the ass. Also getting a bug where I can't place the whole wing assembly back on it, if I do it just won't let me, I place it lower down off the ship, and suddenly it's part of the damn ship, and it will even go to the Launchpad with the parts spread out, but then falls apart/explodes.

Edited May 23, 2014 by XOIIO

[Rune]

So, I've been trying to make a decent looking and functional SSTO for a long time, this is quite satisfactory, however, with the LV-N it just seems impossible to get it into orbit. It would be great for decent range operations but the jets can only get it so high, and it's far to weak to get into orbit itself (though I suck at flying them anyways). I tried with RAPIERs but they have so much little thrust it takes ages to get up to 100,/s, and would take way, way longer to get into the damn orbit.

I'm guessing it's just not feasible for a craft without four engines to get an LV-N into orbit :/

http://i58.tinypic.com/k0j8ro.jpg

edit: there we go.

Also. Got it close to circularization, barely any fuel left, and got this annoying fking bug where the cockpit stays solid and the rest of the ship moves, it happens on multiple ships and is a real pain in the ass. Also getting a bug where I can't place the whole wing assembly back on it, if I do it just won't let me, I place it lower down off the ship, and suddenly it's part of the damn ship, and it will even go to the Launchpad with the parts spread out, but then falls apart/explodes.

Regarding bugs, you are running into the symmetry bug where clipped parts or parts with internal symmetry, make it misbehave by not showing as attached but placing bugged pats with each (failed) click. Try taking out the intake stacks before you move the tanks, or better yet, settle into a final configuration before clipping the intakes in as a final touch. It will save you hours.

As to the design itself, you are seriously lacking rocket power, or have an excess of fuel weight. May I assume some of the oxidizer is emptied? Because otherwise it's more dead weight. It could perhaps makeorbit if flown right (levelling off for a very long speed run so you transition to rocket at close to orbital speeds when you don't need T/W), but flameout thrust asymmetry will make that a pain in the ass. I would just add boost engines for the climb to orbit, something like two LV-909s or four Rockomax 24-77s. That way you still get to use the nuke while not lugging a prohibitive amount of engine mass to orbit.

But the engine configuration you have can also be made to work, you just need less weight in general. Check out the nuke version of the White Dart in R-SUV (link in my sig), you will also learn the Stabojetâ„¢ trick (which is not mine, BTW) to deal with asymmetric flameouts.

Rune. Hope that helps!

[Hodo]

Looks like you have 2 reaction wheels, you only need one at most on that craft.

You should be able to get to orbit with either craft, the RAPIER or the NERVA/Turbojet craft. If the design is about the same the one pictured then it is light enough with enough fuel. The trick I found is climb as fast as you can to 15-20km altitude, then bring the accent angle down to about 5-10deg, but make sure you keep climbing, I generally slow my rate of climb down to 10-20m/s. This way I am gaining as much speed as possible. By the time you hit 25km you should be going close to 1600m/s or about when your turbojets stop making power. At that point turn on the nuke and boost the rest of the way.

[XOIIO]

Didn't occur to me to remove some oxidizer, I'll give that a whack. I threw two reaction wheels and an SAS module because it was having a lot of troublee maintaining a stable heading at 45 degrees, or at any angle, it would always drop a lot.

[Hodo]

Didn't occur to me to remove some oxidizer, I'll give that a whack. I threw two reaction wheels and an SAS module because it was having a lot of troublee maintaining a stable heading at 45 degrees, or at any angle, it would always drop a lot.

Do you have a picture with the CoM and CoL on?

Oh and are you using FAR?

[XOIIO]

Do you have a picture with the CoM and CoL on?

Oh and are you using FAR?

I don't have ferram aerospace, would that help? I heard it makes SSTO design harder.

25 degrees seems to be the angle for me, otherwise I lose altitude, I dropped down to 18km, and only got to 1100 m/s, maybe higher up it will help, but this is just proving to be a huge pain. Can't remember how I got my previous SSTO into orbit :/

Too bad mechjeb can't handle an ascent profile for spaceplanes, that would be handy.

[Hodo]

I don't have ferram aerospace, would that help? I heard it makes SSTO design harder.

25 degrees seems to be the angle for me, otherwise I lose altitude, I dropped down to 18km, and only got to 1100 m/s, maybe higher up it will help, but this is just proving to be a huge pain. Can't remember how I got my previous SSTO into orbit :/

Too bad mechjeb can't handle an ascent profile for spaceplanes, that would be handy.

FAR doesn't make it harder... it makes it so aircraft react like aircraft.

But in that picture I see nothing wrong with the design. It should work fine you have plenty of d/V, your TWR is high enough. Even you Nerva TWR is pretty decent. Other than perhaps a few struts needed to shore up the design so it doesn't come apart under high G maneuvers you should be fine. MJ is horrible for all things aircraft related. I love it for the information and making orbital burns but past that it is just an information display for me.

[XOIIO]

FAR doesn't make it harder... it makes it so aircraft react like aircraft.

But in that picture I see nothing wrong with the design. It should work fine you have plenty of d/V, your TWR is high enough. Even you Nerva TWR is pretty decent. Other than perhaps a few struts needed to shore up the design so it doesn't come apart under high G maneuvers you should be fine. MJ is horrible for all things aircraft related. I love it for the information and making orbital burns but past that it is just an information display for me.

I might give FAR a try then, I defenitely agree, mechjecb is awesome for orbital manuevers and long time burns, I use it for most of my rocketry, since it's hard to get an accurate burn time estimate without altering your orbit whereas mechjeb knows, but anything spaceplane related it does not work, tried the landging guidance a couple times, just dropped me into the ocean lol.

[The Destroyer]

Well, technically FAR makes things much harder. Due to the KSP aerodynamic model not counting supersonic transitions, wing sweep, etc.

[Northstar1989]

I might give FAR a try then, I defenitely agree, mechjecb is awesome for orbital manuevers and long time burns, I use it for most of my rocketry, since it's hard to get an accurate burn time estimate without altering your orbit whereas mechjeb knows, but anything spaceplane related it does not work, tried the landging guidance a couple times, just dropped me into the ocean lol.

MechJeb is actually great for precisely controlling your Angle of Attack with its ASAS function (in "Surface" mode), and fine-tuning your SAS torque (so you don't over-steer when delicate maneuvers are needed) with its Altitude Adjustment function...

I use it all the time for LONNNGGGG, relatively stable flights, such as the speed run on one of my Thermal Turbojet spaceplanes... (TTJ's are from KSP-Interstellar)

@XOIIO

Give MechJeb a try. It sounds like you might be setting too high an Angle of Attack- real planes achieve maximum lift at an Angle of Attack of around 20 degrees...

You might also want to try building the wings in at a 5 or 10 degree upward angle (use Shift + WASDQE to rotate parts 5 degrees) so that you can point the intakes and engines more level to the horizon during your speed run. That should raise your altitude ceiling under jet power quite a bit... (especially since intakes work best when pointed along the prograde vector)

Built-in wing angle also makes it easier to get off the runway on takeoff...

Regards,

Northstar

[Hodo]

Here is an album I just made of one of my newer SSTO space planes, it is based on an older design.

SVP-407 VTOL SSTO.

Javascript is disabled. View full album

If you look at the pictures I took them at key points during the accent to give you an idea of what the typical accent profile is for a space plane. This one was a bit more shallow and longer than most due to its cargo distribution but it is pretty much the same for all of my SSTOs.

[XOIIO]

I got up to 1300m/s, lowered the oxidizer more, going to try again, but when I got to 1300m/s and the jets gave out, I lost speed rapidly when I switched to the LV-N and I was at over 25km :/ Maybe I'm just a ****ty pilot. I'd like to get up with as much LV-N fuel as possible and I've read a couple times that some people can get a 100km AP with jets alone, that would be great, no clue how though.

https://www.dropbox.com/s/bd3lrz14eh6riv9/LV-N%20spaceplane.craft

Edited May 23, 2014 by XOIIO

[nli2work]

You can try burning the NERVA from ~15km along with the turbojets. That might help you get enough speed to generate lift to gain altitude. Also run fuel lines from the side tanks to the center so the NERVA can draw from those tanks as well. Otherwise the NERVA only draws from center tank.

I also recommend reconfiguring your wings this way for some extra lift surfaces.

Edited May 23, 2014 by nli2work

[The Destroyer]

Spam more intakes. Intake spam= longer the jets can run.

[eempc]

Just some suggestions: you can try draining some excess oxidiser for reduced weight, and instead of using the NERVA to get into the final phase of orbit you could try those little orange radial 24-77 engines.

Also that in line docking port is stupidly heavy compared to a regular open port stuck to the top.

[LordFjord]

1300m/s at 25km is not bad, you seem to hit a wall there and it sounds familiar to me, been there as well

The (probably) issue is, that you keep raising your altitude from there too fast. -> The air gets thinner as you climb, your speed raises (but not enough) -> sooner or later the turbos will flame out -> good bye.

Try to raise your altitude slower. It is perfectly fine to level out the flight at 25 km altitude to pick up more speed.

Throttle down a bit when the intakes provide not enough air, as long as you keep accelerating, things are fine.

You can also try to start the nuke instead of throttling down, but try to keep the jets going as long as possible.

You NEED to get to ~35km altitude with a speed of ~2000m/s, from there you can pull up a bit and try to go on the nuke alone.

I'll give your craft a go when back @home.

[XOIIO]

1300m/s at 25km is not bad, you seem to hit a wall there and it sounds familiar to me, been there as well

The (probably) issue is, that you keep raising your altitude from there too fast. -> The air gets thinner as you climb, your speed raises (but not enough) -> sooner or later the turbos will flame out -> good bye.

Try to raise your altitude slower. It is perfectly fine to level out the flight at 25 km altitude to pick up more speed.

Throttle down a bit when the intakes provide not enough air, as long as you keep accelerating, things are fine.

You can also try to start the nuke instead of throttling down, but try to keep the jets going as long as possible.

You NEED to get to ~35km altitude with a speed of ~2000m/s, from there you can pull up a bit and try to go on the nuke alone.

I'll give your craft a go when back @home.

Alright, I'll give that a try, it's proving difficult to get the angle just right, too low and I drop, too high and I guess it's too fast. That's where I'd like mechjeb to be able to hold a specific angle to try stuff out and get the best one.

Also, I do have fuel lines leading from the external tanks to the internal one so that I can run the rocket engine longer.

[XOIIO]

Got closer with a 15 degree angle but engine power started cutting out, I'll add another set of intakes (have to move the jets back), couldn't get much above this speed though.

I always see people fly them and when they get up to speeds like this the ap point manages to get pretty far up but I can barely get it any further than my current height. I could aim straight up and burn but then my speed dies and it gets unstable.

[Othuyeg]

Try this: put some of your air intakes into action groups. Toggle them off at takeoff and turn them on when you are starting to hit thinner air. When they are off they will not produce the massive amount of drag they do when they are on.

[nli2work]

2 intakes per engine is more than enough to keep them from flame out before 30km. More intakes will add more weight and drag and won't help you much in gaining thrust. You are not getting enough lift at the highest speed you can go at a given altitude with your TWR. Even thought it's close to 3 to 1, that's good for vertical ascent, for horizontal acceleration is not good enough to get you enough orbital speed.

[XOIIO]

2 intakes per engine is more than enough to keep them from flame out before 30km. More intakes will add more weight and drag and won't help you much in gaining thrust. You are not getting enough lift at the highest speed you can go at a given altitude with your TWR. Even thought it's close to 3 to 1, that's good for vertical ascent, for horizontal acceleration is not good enough to get you enough orbital speed.

I might swap the jet engine tanks with half size ones and engine nacells or maybe liquid fuel then to try and drop the weight down. I really want to keep the in line clamp o tron, it looks a lot better.

[XOIIO]

Got the weight down to 16.442 tons, I was able to get up to speed better but when I had to turn the jets off I started losing speed, then altitude, couldn't break into orbit :/

[Othuyeg]

Those Engine Nacelles are very poor air intakes. They give you alot of extra weight. I would simply ditch them. You don't need them. Also try adding more wings. Either a pair of delta wings or swept wings onto your current wings. Or both.

It adds drag but you'll need the lift in thinner atmosphere.

I would even try and add a pair of wings to the front.

Wings = goood!

[Mesklin]

Brilliant, you are already on the half way to the space. From this point on nuke and set pitch to 30, then gradually down throttle (best way is using options "Prevent jet flameout"). Next climb till throttle reach 1/3, off jets and full thrust, set pitch to 50-55. Next wait for stopping decreasing vertical speed, wait some time and start gradually decrease pitch (I recommend do not overshot 100 m/s for vertical speed). Congratulation, you are in space today

P.S. Your original spaceplan from post also can reach orbit, I checked it

Edited May 23, 2014 by Mesklin

[Claw]

For a stock design you look like you're on the right track. If your AoA is that high, you probably need a little bit more wing area. That will help keep your AoA down, which will reduce your drag and increase your intake efficiency. You're getting up to pretty high speeds, but you should get a little higher in altitude too. Your picture of 1400+ m/s at 21km is great, you just need to get up a bit higher and you'll continue to accelerate. I think having a little bit more wing area will help with that.

To me, it looks like you have enough intakes and you have a high enough engine/mass ratio.

It's good to level out and accelerate at 25km like you did, but you need to then get above ~32km and your orbit will start to stretch out. If you can get your orbit stretched out then you can work your altitude a bit higher. Eventually you should be high/fast enough that you can fire up the rocket and point upward a bit more to get above the rest of the atmosphere. That will then buy you some time to use the LVN to finish the orbital insertion.

I find with dual TurboJet designs, it's tough to get a really good atmospheric circularization due to the asymmetric thrust issues. It just gets tough to really eek out the engines at the end. Although realize you can run the TurboJets and rockets at the same time. TurboJets will still provide some thrust (if you control the asymmetry) to add to your rocket.

(EDIT: Yeah, what Othuyeg just said... )