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

[Mesklin]

Launch report

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[XOIIO]

Hmm, so the original can get into space, that would be ideal, I'm glad to know it can, plus it has a decent amount of fuel left (normally I see SSTO's almost empty). Guess I just need to work on piloting. I'll download that one and rename it and try on that.

I am a far way from making an SSTO that has an in line clamp o tron and advanced grabbing unit for asteroid exploration, that's for sure lol

[LordFjord]

Mesklin beat me on it

I used the craft file you posted (just removed the mechjeb part so I could load it).

Anyway, here's my attempt:

It wasnt easy to get to space, I did several sine-like drops (and 2 flameout spins) until I figured out what throttle settings (combined nuke+turbos at high altitude) finally got me past 32km altitude. From there it was just pulling up and let the nuke do the work.

Throttling back between 27 and 30 km altitude was the key.

If you have trouble with the transition to space, just add a pair of rocko 24-77s and use them to push it out of the athmosphere. From there you can use the nuke for efficient travel.

[XOIIO]

Got closer, but lost a load of fuel, problem is that the apoapsis keeps dropping really fast, so I can't set up a good node to circularize, I also wish I could take more oxidizer, I'll try moving it up a bit, the extra burn time would be a huge benefit. I also addedd those rockomax engines for a bit of help. I really wish mechjeb had an ascent guidance plugin for spaceplanes too. It would be nice and repeatable.

edit: strange, tiny screenshot)

Edited May 23, 2014 by XOIIO

[XOIIO]

Moved the oxidizer up to 126, got into orbit and was able to circularize, unfortunately I did not have enough fuel to make it to the refueling station, I'd need another minute to be comfortable :/ I don't know if I can make it up with everything full.

I also forgot how much of a lag monster it is, I'm only getting 6fps around it. (used infinite fuel to get there, I want to see how the range is once refueled, I'd like this to get people to and from both moons.

edit: I have around 26 minutes of fuel once everything is filled up, that's excellent, I just need to get to the refueling station now. I'll also probably make a smaller less laggy one at higher altitude that way I don't need to set up a phasing orbit (I hope)

Edited May 23, 2014 by XOIIO

[Redshift OTF]

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

Sure it is.

It might be that you are carrying too much weight though.

[XOIIO]

Well once I can get it into orbit and refuel reliably this will be a proud SSTO to have, with full fuel I can fly to minimus, explore around, I actually used up a decent bit getting to the couple bases I have, a few more RCS thrusters would let me fly on those alone.

Came on on basically a vertical reentry, but I pulled out of it no problem, I just threw on all the engines for a few seconds to get moving horizontally. Fun trip, just sullied by the brief bit of infinite fuel :/

[Northstar1989]

Well once I can get it into orbit and refuel reliably this will be a proud SSTO to have, with full fuel I can fly to minimus, explore around, I actually used up a decent bit getting to the couple bases I have, a few more RCS thrusters would let me fly on those alone.

Implementing the following changes will help:

(1) Build the wings in at an angle of at least 5-10 degrees (Shift+rotate in the VAB/SPH). This will allow you to point the nose closer to the horizon during your speed-run, so your intakes will bring in more air at the same speed. (by the way, did you clip multiple intakes together on the latest design? It kind of looks like it... Personally, I strongly oppose abusing part-clipping on intakes.)

(2) Replace the Mk1 Cockpit with a Mk2 Cockpit. The Mk2 has an attachment node on the front- use it for a third RAM intake (3:2 intake:engine ratio isn't unrealistic...)

(3) Angle the vertical stabilizers at the back horizontally by at least 15 degrees. This will provide a bit of lift at the cost of no extra weight. It will reduce your yaw-stabilization a bit, but you don't need as much as you have there... Modern aircraft designs such as the F-22 Raptor use inclined vertical stabilizers for a reason:

(4) Consider swapping down to just one Turbojet, and increasing to two LV-N's. A single Turbojet located centrally behind the Center of Mass doesn't have to worry about jet flameout, and on your speed run, you won't have enough IntakeAir to run two Turbojets at more than 50% throttle anyways. The extra rocket thrust should help you get to orbit, on the other hand, and LV-N's don't need to worry about flame-out.

If you do this, though, move the side-fuselages as far forward as possible so your twin LV-N's won't move the Center of Mass too far back, and add a Structural Wingboard to the back of each of your delta-wings as a trailing edge to move the Center of Lift further back so your plane won't be too much of a tail-dragger (in this case, you won't be able to build your main wings in at an angle... Your front winglets and vertical stabilizers should still have a built-in Angle of Attack though.)

(5) Move that antenna (or whatever it is) at the tail-end as far forward as possible (I suggest just behind the cockpit). You will want a Center of Mass that is further forward to make your plane less of a tail-dragger and more stable at low speeds- especially if you switch to twin LV-N's as I suggested. You realistically would want your antenna as far from the nuclear reactors in the LV-N's as possible anyways... The same goes with any radial batteries (are those batteries at the rear- I can't tell) and engines you have on the fuselage- move them forward.

Regards,

Northstar

Edited May 24, 2014 by Northstar1989

[XOIIO]

Yeah, I still don't like spamming intakes :/ It's just ridiculously hard to get a good SSTO without that, I have four per jet.

I have a feeling if I swap it for two LV-n's it will be much harder to get it into orbit with the reduced thrust and added weight, plus I really like how this looks now and the LV-N is far enough in it's fairly easy tot ake off and land.

I did forget to adjust the wings again and tail fins after loading this old one, hopefully that will make it easier to get into orbit with the extra oxidizer weight.

I'm going to stick with this cockpit as the radar altimeter is super handy when landing on minimus and the mun by extention.

Edited May 23, 2014 by XOIIO

[Northstar1989]

Yeah, I still don't like spamming intakes :/ It's just ridiculously hard to get a good SSTO without that, I have four per jet.

Ugh, I would never resort to that. Then again, I have a lot more experience with spaceplanes, and play with mods like B9 Aerospace and Procedural Dynamics (procedural wings) that allow me to build precisely the spaceplane I want/need...

I have a feeling if I swap it for two LV-n's it will be much harder to get it into orbit with the reduced thrust and added weight, plus I really like how this looks now and the LV-N is far enough in it's fairly easy tot ake off and land.

You clearly don't understand how the jet engines work. Right click on them some time when you are above 20,000 meters, and look at their thrust. They produce less thrust the faster you are flying, and are limited by the supply of IntakeAir. What that means is, near maximum altitude, two Turbojets limited by IntakeAir supply will produce *exactly* the same thrust as one Turbojet- but with less weight and no possibility of asymmetric flameout. Additionally, because of the way jet flameout works, you can keep one Turbojet flying up to a higher altitude than you can two with the same number of intakes...

You will actually get MORE thrust with two LV-N's, because they won't be affected by your speed or altitude. And I would hardly consider two LV-N's to be spamming them...

I did forget to adjust the wings again and tail fins after loading this old one, hopefully that will make it easier to get into orbit with the extra oxidizer weight.

Make sure to build the tail fins and front winglets in at a pitch-angle, and a horizontal angle as well on the tail fins; and either angle the delta wings by 5-10 degrees, or add a Structural Wingboard to the back of each delta wing. Either one will raise your altitude ceiling under jet power alone.

Also, move the antnenna and any radial batteries as far forward as possible- it will improve your plane's stability.

I'm going to stick with this cockpit as the radar altimeter is super handy when landing on minimus and the mun by extention.

If you were playing with MechJeb, you could use the Surface Info function or a custom window for a radar altimeter. That would be visible without having to go IVA, and would free you to use the Mk2 cockpit and place an air intake on the front, so you wouldn't have to do as much part-clipping (in fact, though it will decrease performance of your spaceplane, I strongly encourage you to take the honorable road and remove all the extra part-clipped air intakes, so you only have 1 intake per node...)

Regards,

Northstar

Edited May 23, 2014 by Northstar1989

[FleshJeb]

That's a beautiful craft, and I'm enjoying your process. Thanks for sharing.

You said earlier that you were having stability problems; I suggest that might be the canards. I have a really hard time designing small craft with them. Right now, you have more control authority in the front than the back.

Definitely add more wings--It'll lower your AoA so that you can get more speed out of the turbojets. My rule of thumb is 1 lift unit per ton of mass. To that end, my spaceplanes are "lifting bodies" with Structural Wing panels on the underbody.

Another fun thing to do (but ugly) is to put rover wheels on the nose of the craft. Place them higher than your extended landing gear, and you can truck around on planets by raising the nose gear.

[Hodo]

Implementing the following changes will help:

((3) Angle the vertical stabilizers at the back horizontally by at least 15 degrees. This will provide a bit of lift at the cost of no extra weight. It will reduce your yaw-stabilization a bit, but you don't need as much as you have there... Modern aircraft designs such as the F-22 raptor use inclined vertical stabilizers for a reason:

http://i.imgur.com/B87wTjn.jpg

I have to disagree with this.

The F-22A ©raptor has the vertical stabilizers canted for radar stealth reasons, not so much added lift.

The other option instead of using the LV-N rocket, you can use the smaller half ton rocket engines that generate 50kn of thrust each. They work great when in pairs, and are light enough that a single turbojet can get you fast enough and high enough that you don't need to burn a lot of fuel to get into orbit.

As for the intakes, Northstar is dead on, I have managed to get a SSTO into orbit with a 1:1 ratio of intake to jet engine. It was a bit harder but it is possible, granted I use FAR so I have the added benefit of air compression at higher speeds to make up for thinner air at higher altitudes. The one I posted on page 2 that shows my accent profile only has 18 intakes for the 10 air breathing engines.

Most of my current SSTO space planes use a 3:1 intake to jet ratio for ease of flight, which isn't bad and I can find documented cases of it in the real world.

There is a fine line for SSTOs and fuel balance. I prefer to use TAC fuel ballancer to let me ballance the tanks without having to worry about them mid flight.

There are 3 mods I consider core for building any SSTO spaceplane and I will not go without.

This is one using only stock parts, and it has 3 intakes per jet engine.

2 Radial intakes

2 RAM intakes

2 Engine Nacells

for 2 Turbojets

TAC Fuel Ballancer- helps keep your CoM where you designed it, and you can shift it slightly in flight by moving fuel around.

Ferram Aerospace Research (FAR)- Aircraft behave like aircraft, not like submersables at 10,000leagues.

Kerbal Enginereering Redux or Mechjeb- information displays are invaluable.

Edited May 23, 2014 by Hodo

[TeeGee]

I have a feeling it is your ascent profile.

After you reach 12km, pitch the nose down so that your vertical speed indicator is exaclty 100m/s. Keep it there all the way up until you have a apoapsis of 85km ish. Cut thrust engines to lower thrust and ride your craft up without losing the apoapsis. After MECO, shut down your engines, close your intakes, and turn on your LV-N. Don't thrust your engine up yet, coast until apoapsis and circularize.

If you are spinning out of control due to flame out, try putting your jet engines CLOSER to the LV-N, or try thrusting down once you reach specific altitudes when you'd normally flame out.

You're also carrying WAAAY too much oxidizer and liquid fuel. Remember, your crafts job is to make orbit, not fly from LEO to Duna! You can always refuel her in orbit if you need that extra fuel to interplanetary travel, but 1st you need to get into orbit. Make her as LIGHT as possible

Edited May 23, 2014 by TeeGee

[XOIIO]

I have a feeling it is your ascent profile.

After you reach 12km, pitch the nose down so that your vertical speed indicator is exaclty 100m/s. Keep it there all the way up until you have a apoapsis of 85km ish. Cut thrust engines to lower thrust and ride your craft up without losing the apoapsis. After MECO, shut down your engines, close your intakes, and turn on your LV-N. Don't thrust your engine up yet, coast until apoapsis and circularize.

If you are spinning out of control due to flame out, try putting your jet engines CLOSER to the LV-N, or try thrusting down once you reach specific altitudes when you'd normally flame out.

No problems with flameout, but 12km to go horizontal? I've always heard 18/20km, that seems pretty low, unless it will let me get faster and therefore throw my AP out to 85km easily.

Edited May 23, 2014 by XOIIO

[Northstar1989]

No problems with flameout, but 12km to go horizontal? I've always heard 18/20km, that seems pretty low, unless it will let me get faster and therefore throw my AP out to 85km easily.

It all depends a lot on the design. Some spaceplanes do best just climbing with a nose angle of 30 degrees, activating their rockets when their trajectory starts to level out- like this one...

XOIIO, I designed an all-stock spaceplane for you to show you exactly the concepts I was talking about before. I used MechJeb and TAC Fuel Balancer with it, but they didn't really let me do anything I couldn't do unmodded (except quickly move some fuel out of the central tank- which could have easily been accomplished with fuel pipes or careful manual transfers). I was also running KSP-Interstellar, but not using any of its parts- but that actually nerfs the design by causing the Turbojet to overheat if I don't shut it off by around 32 k... (KSP-Interstellar allows stock precoolers to counteract this- but I didn't want to show you an example craft with what would for you be a worthlesss part)

You can have the craft file for reference or use if you want, if somebody can just remind me how to post craft files to the forum (it's been a long time since I last did so...)

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I took a LOT of screenshots to show you every step of the ascent profile, though I forget to take ones showing the drop-off of Turbojet thrust at high altitude (due to limited IntakeAir)...

Also note the following:

(1) The canted canards, like I suggested to you before. This was accomplished with a combination of the default large-increment angles and Shift+rotation to design the largest cant I felt would look presentable... The spaceplane had plenty of vertical stabilization, and I had no issues with yaw control.

(2) The 10-degree built-in Angle of Attack. This allowed me to point the nose closer to the prograde vector- maximizing the effectiveness of both the air intakes and the engines (Oberth Effect means you get more energy if you burn along your prograde vector). It also helped a lot with getting off the runway, by greatly reducing its liftoff speed- since the twin LV-N's made it rather heavy... Even so, it used most of the runway getting up to speed...

(3) The presence of only 1 centrally-positioned Turbojet. As you can see from the screenshots, at high altitude there was just barely enough IntakeAir for the single Turbojet. Multiple turbojets would have just produced the same thrust with more mass and drag at high altitude. It did mean that a speed run wasn't practical though, since the altitude ceiling on turbojet-only power was so low... (at the turbojet-only altitude ceiling of around 4200 meters, the same 3 intakes could have run 5 or 6 turbojets...)

(4) The increased wing size vs. your spaceplane design. Your design had entirely too high of a wingload, which was greatly hampering its performance. I forgot just how little lift the stock wing parts create- even this design has a rather high wingload considering its heavy load of rocket fuel and LV-N's...

(5) The lack of reaction wheels- with properly-designed wings and control surfaces, you don't actually need any SAS torque to keep your spaceplane stable in atmospheric flight. This also allowed me to strip out any extra batteries, and get by with a single Ox-STAT solar panel for generating electricity outside the atmosphere... (you could easily get by with no solar panels, and just be VERY careful with use of the cockpit's SAS torque if you wanted...)

(6) The increased wing area towards the rear. Nose-dragging designs (ones with their Center of Lift behind their Center of Mass) are almost always more stable than tail-draggers: and actually improperly named, as in powered flight they tend to stabilize towards the horizon...

Regards,

Northstar

Edited May 24, 2014 by Northstar1989

[Northstar1989]

I have to disagree with this.

The F-22A ©raptor has the vertical stabilizers canted for radar stealth reasons, not so much added lift.

I'm aware that the reduced radar profile was the main motivation, but the extra lift was also a definite advantage.. (especially considering how high the wingloads are on most fighter jets- and as it would have allowed even more weapons or extra fuel to be loaded)

The other option instead of using the LV-N rocket, you can use the smaller half ton rocket engines that generate 50kn of thrust each. They work great when in pairs, and are light enough that a single turbojet can get you fast enough and high enough that you don't need to burn a lot of fuel to get into orbit.

The LV-909's definitely work, but would force him to cut a lot tighter on the Delta-V during ascent and refueling. Their ISP is less than half that of LV-N's, so they have less than half the burn-time for the same number of fuel tanks. LV-N's are more forgiving of mistakes made during the rocket-powered ascent to orbit, and allow greater range after refueling...

As for the intakes, Northstar is dead on, I have managed to get a SSTO into orbit with a 1:1 ratio of intake to jet engine. It was a bit harder but it is possible, granted I use FAR so I have the added benefit of air compression at higher speeds to make up for thinner air at higher altitudes. The one I posted on page 2 that shows my accent profile only has 18 intakes for the 10 air breathing engines.

Most of my current SSTO space planes use a 3:1 intake to jet ratio for ease of flight, which isn't bad and I can find documented cases of it in the real world.

I'm glad we're in agreement about the intakes. I think the 8 intakes he stacked into his design (with part-clipping) might have been part of the reason he was having trouble making orbit- as they add a LOT of drag to the aircraft...

There is a fine line for SSTOs and fuel balance. I prefer to use TAC fuel ballancer to let me ballance the tanks without having to worry about them mid flight.

There are 3 mods I consider core for building any SSTO spaceplane and I will not go without.

This is one using only stock parts, and it has 3 intakes per jet engine.

2 Radial intakes

2 RAM intakes

2 Engine Nacells

for 2 Turbojets

http://i.imgur.com/iynuTTm.jpg

Interesting design, but like somebody pointed out before, Engine Nacelles make for extremely inefficient intakes (their primary purpose is actually supposed to be increasing fuel flow, and thus thrust- but the code isn't in place for that yet- much like precoolers currently have no function in the stock game).

I also always recommend new players stick with single-Turbojet designs, as that way they don't have to worry about asymmetric flame-out, and can focus on learning the other principles of spaceplanes. With sufficient lift, such a design also grants huge range and a high altitude ceiling to most planes- but it's hard to accomplish that in the stock game, as the lift coefficient doesn't increase for multi-part wings like it does for the bigger wings in mods...

(that number in the SPH/VAB labeled as "lift" is actually lift coefficient in the same manner as drag coefficient- the game multiplies the wing's mass by it and factors in Angle of Attack to get actual lift... It took some testing for me to determine this- I compared modded parts with low mass but high lift coefficients vs. much heavier wings with medium lift coefficients to confirm this.)

TAC Fuel Ballancer- helps keep your CoM where you designed it, and you can shift it slightly in flight by moving fuel around.

Ferram Aerospace Research (FAR)- Aircraft behave like aircraft, not like submersables at 10,000leagues.

Kerbal Enginereering Redux or Mechjeb- information displays are invaluable.

Those are some great mods, and I'm planning on implementing FAR in my next career game myself... (after the release of 0.24 and update of necessary mods, as well as when I reach a shopping-point in my current save) I'm starting to wish I had just started with FAR from the beginning, so I actually would recommend it to new players...

Regards,

Northstar

P.S. Many players may be interested to know that the current stock aerodynamics model actually uses essentially the same formula to calculate lift as to calculate drag, right down to multiplying mass by a coefficient and factoring in speed- only with an additional term for Angle of Attack.

P.P.S. In real life, lift coefficient increases with wing size- though there are also effects of shielding and increased drag on the wingtips that prevent this from becoming nearly as important of a factor in real-life or with FAR as with stock aerodynamics and B9 Aerospace or Procedural Dynamics, for instance... And due to mach-effects, while bigger wings are still much better on subsonic aircraft, the same holds true to a much lesser degree (and actually becomes harmful much sooner) on supersonics with FAR or in real-life...

Edited May 24, 2014 by Northstar1989

[Darth Lazarus]

very intersting disscussion about the SSTO. i have some similar troubles to get my first SSTO into orbit. after some trial and error (and watching some youtubevids) i replaced a single LV-N with a pair of two Rockomax 48-7S. but i think with the ideas here, i might get a LV-N into orbit which would dramaticly increase the rnage of my SSTO.

here is it in the current configuration. rockets are hidden inside the turbojets

[TeeGee]

No problems with flameout, but 12km to go horizontal? I've always heard 18/20km, that seems pretty low, unless it will let me get faster and therefore throw my AP out to 85km easily.

No. What I do is takeoff and go into a steep vertical climb until I reach 12km then level out until I decrease my vertical speed to 100m/s and keep ascending with that vertical speed. The point of that is to maximize horizontal speed and keep ascending just enough to allow your engines time to push the craft to her top speed.

If you go higher FASTER, you are going to flame out/drop your thrust because of less air available before your engines can spend time at their max thrust altitude.

[Rune]

No. What I do is takeoff and go into a steep vertical climb until I reach 12km then level out until I decrease my vertical speed to 100m/s and keep ascending with that vertical speed. The point of that is to maximize horizontal speed and keep ascending just enough to allow your engines time to push the craft to her top speed.

If you go higher FASTER, you are going to flame out/drop your thrust because of less air available before your engines can spend time at their max thrust altitude.

While you are kinda right, "12kms and 100m/s" is more of a rule of thumb for your engine configurations (and 100m/s ascent rate seems high for attaining top atmospheric speed). If you have KER, it's a better idea to keep an eye on the "terminal velocity", and make sure you maintain the same geometric relation (totally dependent on your T/W and L/W ratio), ideally close to 1:1 for well designed SSTO's (at any height you are ascending at maximum rate while still going at terminal speed). But you know, whatever works for you and YMMV. SSTOs are the one of the "art-iest" vessels in KSP... that is, it takes a lot of practice (and explosions) to get them right.

Rune. If you want to go technical.

[TeeGee]

While you are kinda right, "12kms and 100m/s" is more of a rule of thumb for your engine configurations (and 100m/s ascent rate seems high for attaining top atmospheric speed). If you have KER, it's a better idea to keep an eye on the "terminal velocity", and make sure you maintain the same geometric relation (totally dependent on your T/W and L/W ratio), ideally close to 1:1 for well designed SSTO's (at any height you are ascending at maximum rate while still going at terminal speed). But you know, whatever works for you and YMMV. SSTOs are the one of the "art-iest" vessels in KSP... that is, it takes a lot of practice (and explosions) to get them right.

Rune. If you want to go technical.

What's KER?

Well I keep it at 100m/s because I am a little impatient and the longer I spend in atmo, the less liquid fuel I have in space. I find that my spaceplanes reach 100km apoaps + with that ascent profile on airbreathers alone, so my goal is to not only reach orbital speed, but to minimize my time spent in drag producing atmo.

[nli2work]

What's KER?

Well I keep it at 100m/s because I am a little impatient and the longer I spend in atmo, the less liquid fuel I have in space. I find that my spaceplanes reach 100km apoaps + with that ascent profile on airbreathers alone, so my goal is to not only reach orbital speed, but to minimize my time spent in drag producing atmo.

Kerbal Engineer Redux. Information mod, without the automation parts like MechJeb

[TeeGee]

Kerbal Engineer Redux. Information mod, without the automation parts like MechJeb

Yeah I already have that.

[XOIIO]

Screw it, spaceplanes are awesome, but I can't fly them for ****, it would take too many attempts to get into space for it to be worth time compared to a rocket. Until mechjeb can fly my spaceplane into orbit I'm just stickign with rockets :/

[Cupcake...]

Oh well... If all else fails you could always lose the wings completely.

Cupcake...

Edited May 25, 2014 by Cupcake...

[XOIIO]

That's a badass SSTO, I have thought of trying that sort of a design next, probably much easier.