SSTO to laythe and beyond

[Nefrums]

You managed to fly the "PLAD K-E-K-K-J route" without precise node?!?

The inclination change will cost a lot less if done at the AP of your kerbin orbit, after all PE kicks, but before the last ejection burn at the PE

[Red Iron Crown]

Hopefully the ~3.7km/s I have left on my initial Jool trajectory will be enough...

You should be fine, assuming you capture cheaply at Jool and Laythe with gravity assists/aerobraking. I see you saved some oxidizer, presumably for the Laythe ascent, that should make it trivial. Good to see you returned to the mission, I thought you might have abandoned it.

You managed to fly the "PLAD K-E-K-K-J route" without precise node?!?

Indeed. I couldn't get it to work even with PreciseNode. I really should try it again.

[Nefrums]

It get easier after you done it a couple of times. The trick is to get the flybys right on schedule. If you are more than a few hours of on the eve flyby it will be very hard to hit the last kerbin flyby.

[herbal space program]

You managed to fly the "PLAD K-E-K-K-J route" without precise node?!?

The inclination change will cost a lot less if done at the AP of your kerbin orbit, after all PE kicks, but before the last ejection burn at the PE

Why yes, yes I did, for four separate ships, flying every maneuver manually . However, I should really not act too smug, as I haven't actually gotten all the way to Jool yet. The last Kerbin encounter requires me to get right down to the top of Kerbin's atmo, so we'll see if I can actually manage it without burning any more fuel. It's one thing to have the maneuver node editor telling you that you'll reach Jool, and another to actually arrive there. I'll certainly need to make another correction both right before and right after the second Kerbin encounter to dial in my Jool approach. As to making the Eve ejection adjustment while still in Kerbin orbit, I agree that would have made it cost significantly less, but the maneuver node editor is so wibbly-wobbly that far out that it can be really hard to tell where you are. Nonetheless I could no doubt do it better the next time, but given the many hours I've already sunk into this go, I've no stomach for starting over.

Figuring out my Jool approach will be interesting. My initial plan is to try to set up a Tylo encounter that will slingshot me retrograde sufficiently to either get captured by Jool or alternately to send me into Laythe on an escape trajectory that is still slow enough that I wont burn up aerobraking there. I'm tempted to go through everybody's reports to see how they did it, but I want to try to figure it out myself first. I'm hoping I can maybe tag Pol or Bop on the way out too, but we'll see. My 0.90 Jool5 mission, which I unfortunately never posted before 1.0 came out, taught me quite a bit about slingshotting around the Jool system, so hopefully I can come up with something beyond just landing on Laythe.

Edited August 20, 2015 by herbal space program

[Val]

It get easier after you done it a couple of times. The trick is to get the flybys right on schedule. If you are more than a few hours of on the eve flyby it will be very hard to hit the last kerbin flyby.

That was not how I experienced it. I had no problem getting all the flybys to work, even when I was days late for the initial Eve flyby.

What became a problem for me, was that the Jool encounter got harder and harder. Either arriving 100s of days later than PLADs schedule and/or at such high speed that even with a Tylo gravity assist, I needed to burn to capture in Jool SOI.

Edited August 21, 2015 by Val
Convoluted sentences

[herbal space program]

That was not how I experienced it. I had no problem getting all the flybys to work, even when I was days late for the initial Eve flyby.

What became a problem for me, was that the Jool encounter got harder and harder. Either arriving 100s of days later than PLADs schedule and/or at such high speed that even with a Tylo gravity assist, I needed to burn to capture in Jool SOI.

I never had any real trouble setting up any of the encounters before Jool either. What I found last night analyzing the projected Jool encounters of my fleet of 4 ships is that the timing of the second Kerbin encounter is critical. Since you have to be at a 2:1 Kerbin resonant apoapsis no matter what, your speed coming into Kerbin's SOI on the second encounter is pretty much fixed. That means that you have a very limited parameter space to maneuver in in terms of where you place your Kerbin PE and what your ejection angle is. Since you have to come from the inside, the closer you get to Kerbin the higher your AP will be, but also the earlier on Jool's orbital path. That means if your second Kerbin encounter is too early, you'll come in too far behind Jool with no way of correcting your course without burning anti-radially a whole lot. Presumably coming into Kerbin too late would put you out ahead of Jool, but that's actually quite a bit easier to fix since you'll be going so much slower than Jool when you reach its orbit. Anyway, all of my ships can get to a Jool encounter via Kerbin, but the earliest one to arrive there has such a rubbish encounter (>350dV to get down to Tylo's orbit) that I don't think it's even worth it to continue with that one. As it is KEKKJ was only saving me maybe 700dV over a direct Hohman transfer. Anyway, I believe that there is sufficient wiggle room on the first Kerbin encounter to allow you to place the second one where you need it, even if your Eve encounter is a few days off, for a fairly small price in dV. If you just put the second one in exactly the same spot on Kerbin's orbit as the first though, then exactly when you arrive at Eve really is crucial.

--Just a quick update. After posting all that I figured out that the best way to correct my second Kerbin encounter is inbound, as close to PE as possible but before the approach direction starts to change. From there, boosting prograde or retrograde will change the ejection angle so that you can move your Jool encounter ~150 days for ~150 m/s. So far my best ship is headed for a survivable capture at Laythe with a total of 1289 m/s expended from a 70X75km LKO, my worst ship 1457. So if I can land it near deadstick, I should end up on the ground at Laythe for 1300-1500 m/s, with 3.3-3.6km/s dV left -- in all cases significantly cheaper than I could have via a direct transfer. As it turns out, setting up captures at Jool was pretty easy. For three of the ships I was able to set up Tylo encounters that slingshot me retrograde into Jool orbit for just a few m/s over my ~90 m/s plane change correction for Jool. With another ~3m/s, I can adjust each of these so it should culminate in a survivable Laythe aerocapture. For the fourth, I couldn't get the needed Tylo encounter, but I was able to set up a swing around Laythe into a Jool orbit that re-encounters Laythe at much lower speed 4 days (2 Laythe orbits) later. Anyway, this is starting to look pretty doable now...

Edited August 23, 2015 by herbal space program

[Mesklin]

Turbojet is cool device - 1 (one) turbojet + 2 LV-N = 4563 m/c dV on Kerbin 100x100 km orbit with mass 22.6t. Start TWR is only 0.41 and start mass - 30t. Spaceplane is comfortable enough for piloting and has good space TWR on orbit - 0.54, more then start atmospheric TWR .

Note: dV was calculated by my Excel spreadsheet, KER dV calculation is incorrect (nonstandard fuel routing to LV-Ns from central tanks - less drag and mass then fuel duct).

[CaptainTurbomuffin]

Currently my only entry here.

http://forum.kerbalspaceprogram.com/threads/131070-The-weekly-spaceplanes

[panzer1b]

hey guys, im back (kinda forgot about this thread).

Anyways, how do you gusy deal with very low TWR in atmo?

My biggest issue is that i want to get ~25t into LKO with a single rapier, and i either end up having too many wings (and cant penetrate drag wall), or have too few and end up at some horrible angle and the drag becomes an issue since im not flyings traight.

So anyways, how do you guys get excessive tonage into the air with very low amount of engines?

This is my latest craft, it barely makes laythe (~4K dV in orbit), and with grav assists it could easily get to laythe and return, its just difficult to do normally when i need ~2100 to get to laythe (including orbital shift thats ~150dV after the usual ~1950 ejection). and then it is at a minimum 1200 to return reliably. that leaves me with at a minimum 500 dV to get back into orbit around laythe (which is more or less impossible even with the rapiers efficiency).

Yes, it uses excessive clipping, and i have a mod that lets me swap LFO into pure LF tanks (or vice versa), so it is my 1st legit craft that can get to laythe and return, although the last attempt was botched up so it failed, with some more careful flying (or grav assists) i think itd be doable. Ive gotten to the point that i dont give a crap about part clipping anymore, i used to be against excessive clipping, but ive realized its just impossible to get something to work without clipping and have the appearance i desire it to have. Yes many would consider this an exploity design, but compared to my last laythe SSTO in 1.01 (before batteries had mass) i edited a probe core to have the equivalent of 10 tons of batteries, and i crammed 30 medium ion tanks and 30 ion engines all inside a MK1 service bay (thats getting to the point even i cant call legit).

SO do you gusy have any tips on increasing performance while still keeping the same basic shape? I dont care too much about wing layout (although its current layout is designed for good maneuverability in atmo, alot of control surfaces), nor do i care about clipping or whatnot, but id liek to keep the shape or something close to the shape, and at the same time have this get even more range. Also, the missiles are ~2 tons extra, just trying to make this capable of wiping out a pirate station around laythe before landing.

Also, once i finish a few projects in KSP ill updsate the front page and give all the sccessful designs some points and list them there with links (so its easier to get to them and u dont have to navigate the whole thread).

[Red Iron Crown]

panzer1b: My advice for low-TWR ascents:

- Angle your wings a small bit so they have an AoA relative to your thrust, this keeps you from needing a steep AoA for the whole craft.

- Cut drag ruthlessly. Avoid open nodes, spike your Rapiers, use as few struts/fuel lines/other radially mounted parts as possible.

- Use the whole runway, and don't begin climbing until you reach high subsonic speeds.

- I had better results with a subsonic climb, though I know others prefer to go supersonic down low before climbing.

- Don't be afraid to trade some altitude for speed when punching through the sound barrier, then resume your climb afterwards.

- Related: Don't be afraid to light up the rocket if you need some extra thrust for the transsonic region.

[panzer1b]

panzer1b: My advice for low-TWR ascents:

- Angle your wings a small bit so they have an AoA relative to your thrust, this keeps you from needing a steep AoA for the whole craft.

- Cut drag ruthlessly. Avoid open nodes, spike your Rapiers, use as few struts/fuel lines/other radially mounted parts as possible.

- Use the whole runway, and don't begin climbing until you reach high subsonic speeds.

- I had better results with a subsonic climb, though I know others prefer to go supersonic down low before climbing.

- Don't be afraid to trade some altitude for speed when punching through the sound barrier, then resume your climb afterwards.

- Related: Don't be afraid to light up the rocket if you need some extra thrust for the transsonic region.

Ok, so by angling wings, does this cut down the drag in total? Cause the MK2 fulsegae seems a bit high on the drag end especially when not facing perfectly straight. Do wings that have a higher AoA have less drag then having the entire fuselage at a higher AoA, or not? Id like to know this as its beneficial in general for every one of my planes, is it best to have the drag on the wings vs the fuselage in general?

I avoid open nodes and the only thing i keep open is the back of nuke, although well you can put intake there, but it seems to be really bad in that area especially since you cant disable teh stupid automatic fairings (which can sometimes vaporize your ship especially if there is any clipping of the nuke like my ship has). Aside from that, the only parts exposed to teh air are intake in front, MK1 LF tank, 2 MK1-2 adaptors, cargo bay, cockpit, rapier, nuke. That and a few minor things like landing gear, ect, but i doubt those are that big of a deal (i always can stick the front gear inside the cargo bay to disable its drag is thatd help?). Fuel lines and struts and basically all other radial or utility parts that arent essential to fucntion are all internally in teh bay (and hence have drag disabled).

Also, what is the optimal wing area for a lowish thrust craft per ton? In teh past (and now too i guess) i tend to go very low on wings as its mass i dont want in orbit. But now i guess with such low TWR it isnt very practical to have dart builds, need to have some wings. that, and what are the best wings to use? i know to avoid ones with excessive mass, but does the shape affect drag at all, orientation, ect? Do certain shaped wings such as deltas have less drag then say a square wing? Or are wings given a flat amount of drag per a certain AoA at a given lift rating regardless of shape or orientation?

that said, what id give for a MK1 cargo bay (thats actually long enough to fit a bloody missile into). Thatd let me use Mk1 fuselage which seems to be the best in terms of drag. missiles mounted externally are just worthless as they make low TWR ascents impossible, and high TWR yu loose alot of dV on them too.

Edited August 22, 2015 by panzer1b

[Mesklin]

panzer1b - More advices for low TWR crafts:

1. use forward control surfaces - forward control surfaces increase lift when rotated in time of ascent vs backward control surfaces (minimum backward elerons/elevons - only for roll control, if possibly)

2. use minimal quantity of control surfaces and as far as possibly from CoM of craft - it is minimize control surfaces moving -> minimize drag

3. make CoL as much as possibly to CoM - it is minimize control surfaces moving -> minimize drag (but not exactly close for avoid problem with stability)

4. use wet wings, these wings have same lift to mass ratio as standard wings, but also have some fuel inside - completely free fuel

5. you can replace fuel ducts for side vacuum engines by "Small Hardpoint", this detail lighter then fuel duct and, what is more important, has much less drag (struts and fuel ducts produce enormous drag, be carefully with it).

[panzer1b]

Thanks for all the tips guys, i FINALLY DID IT!

My 1st fully laythe capable SSTO that is 100% legit (in my opinion, yes there is part clipping to no end and i used a mod to swap LFO tanks for LF only, but at least i didnt use any true hacks such as editing a probe core to have near 20t of batteries equivalent charge). Its ~26.4t heavy on takeoff and had 4000 dV before i realized i accidentally had 2 RTGs for some stupid reason (i mustve used symmetry despite only wanting one), so it was actually heavier then the final version i have now. The whole angle wings helped ALOT, for some reason angled hull (even angled a little bit) is terrible, and yet higher AoA on the wings seems to have helped. Also the tip about control surfaces on the nose was helpful too, made liftoff way easier, and seems to have no real negative impact on drag or maneuverability. I had to switch to lighter missiles, as 2 tons was a little overkill to drag up there, although the absolute maximum of payload i have tested it is 5 tons, ofc it wont go much more then LKO as u gotta drain the equivalent of fuel, but it will actually get 5 tons of ordinance into orbit provided the weapons are no larger then 625mm caliber. It is rated right now at ~1-1.5t ordinance without draining a drop of fuel. Without missiles, i feel this might very well be comparable to some of the other 4K dV craft ive seen here as that extra 1.5t of dead weight (provided you arent actually going to use them to shoot stuff) is just not helping one bit at all. that, and it has full docking abilities, so its very much multi-role. It most likely can land on duna too (as one of my older versions did).

Only thing im still unhappy about is that i cant seem to get a working SSTO to laythe that doesnt use outright exploits (such as giving yourself near infinite electric charge capacity in a pod) and is below ~25 tons mass. Id really really like a lightweight ~10-15t fighter (the thing i have now feels like a F35 with a cesna engine on it, cant glide, unstableish, and just slow even with the engine on full power, cant climb at all unless ur above 500m/s where it actually becomes useable, and, in space it feels worse then flying a capital ship, but hell, IT ACTUALLY WORKS.

Btw, is there any way to get lower mass then ~20t and still get to laythe and back direct route without grav assists (you can get just about anything in KSP to jool using grav assists well). My last question in this thread, is it even possible to make a 100% legit craft below 15t with no staging at all or refueling that can get ~4-4.5K dV after achieving LKO and allow a direct route to laythe, land, and get back, or is this just some sort of dream that will never come true without mods and or cheats? What id do for a craft that could do that, and atop of that carry at least 1 ~.75 ton missile, thatd be the best fighter ever.

And here are some pics of my new AKSTechnologies HK-201 V3 prototype. This one is most likely going to be put into full scale production. After removing an intake off the back of teh nuke (apparently having that node open is less total drag), removing that useless 2nd RTG, and cutting a few struts that werent really needed inside the cargo bay in the 1st place, i managed to get into LKO with 4350 dV (a little more as i always estimate a little low on what the dV is. It get 6500 dV fully fueled with no oxy loaded aboard, which is enough to get to near anywhere. Finally happy with this thingy.

Javascript is disabled. View full album

Edited August 23, 2015 by panzer1b

[Val]

...

The whole angle wings helped ALOT, for some reason angled hull (even angled a little bit) is terrible, and yet higher AoA on the wings seems to have helped.

...

The reason "angled wings" help, is because wings need AoA to provide lift. It's not because of some magic, low drag property angled wings. Wings are always angled to the airstream (AoA), because that is how wings create lift.

What actually happens, when you angle the wings relative to the fuselage, is that now only the wings are at a high angle in the airstream. That is why it reduces drag. Because the rest of the aircraft no longer has AoA. And therefore less drag.

And that is why real airplanes do exactly the same thing.

"Wings are typically mounted at a small positive angle of incidence, to allow the fuselage to have a low angle with the airflow in cruising flight. Angles of incidence of about 6° are common on most general aviation designs."

Source

Edited August 23, 2015 by Val
Sentence structure and emphasis

[astrobond]

Hi all

Just wanted to try Val wings advices.... works very well !!!

LiquidFuel only, Less than 19t., 4818dV left in LKO

Here is the craft: Laythe Mini SSTO FL.craft

Description:

1 = Toggle Rapier/Intake

2 = Toggle LV-N

Kerbin ascent;

Keep front tank closed until orbit to have a good COM

Full trottle to 400m/s (auto lift off)

15° to 8000m

5° to speed up to 1400m/s

(SAS Hold until 25km, nose max 15° up)

When speed stop accel, press 2

When Rapier stop, press1

4818 m/s left at 75kmx75km LKO after moving wings fuel in center tanks

And som pics of a ksp orbit and return:

Javascript is disabled. View full album

Fly safe with Val

Edited August 23, 2015 by astrobond

[herbal space program]

What actually happens, when you angle the wings relative to the fuselage, is that now only the wings are at a high angle in the airstream. That is why it reduces drag. Because the rest of the aircraft no longer has AoA. And therefore less drag.

And that is why real airplanes do exactly the same thing.

Omg, I can't believe that never occurred to me. At last now I know why I can't get close to your tons/Rapier numbers! Back to the drawing board...

Edited August 24, 2015 by herbal space program

[Red Iron Crown]

It's not just drag reduction as a benefit of angled wings (though that is certainly true), it also means your engines are thrusting closer to the prograde direction, which means lower cosine losses.

[herbal space program]

Well I must say this challenge has given me more than I bargained for at every turn. I thought I had it made slingshotting retrograde off of Tylo into Laythe for my approach to Jool, but after many tries my velocity at Laythe has always been such that any attempt at aerobraking was instant death. It's cheap to get captured into Jool orbit, but all the orbits I seem to be able to get off of Tylo are so eccentric that I can't intersect Laythe at a reasonable velocity. I seem to be having better luck swinging around Laythe on my first go, but the jury is still out. I think my cheapest strategy is probably to get captured into an on-plane orbit with the highest possible AP, then raise PE to Laythe orbit from there and set up an encounter. If I hit Laythe's orbit at my PE, I seem to be able to set up encounters that put me in near-circular orbits around Laythe's altitude without having to put my toes in the atmo.. At any rate, like every other part of this mission this is not trivial...

- - - Updated - - -

It's not just drag reduction as a benefit of angled wings (though that is certainly true), it also means your engines are thrusting closer to the prograde direction, which means lower cosine losses.

It took some tweaking of other aspects of the design, but after messing around for maybe an hour with my wings tipped up a few degrees, I'm getting my SSTO12 on LKO with a good 400-500 m/s dV more than I ever could with everything in one plane. I can probably do better with a little more practice. It just helps at every turn.

Edited August 24, 2015 by herbal space program

[Nefrums]

You could do a tylo gravity slingshot followed by a laythe slingshot. Even without aerobraking that should put you in an orbit close to Laythes.

Note that you should try to hit Tylo (and Laythe) when it is a perpendicular position in its orbit compared to the direction your ship is going. So that you ship is going the same direction as Tylo

With this approach I got captured at laythe after a gentle aerobrake at ~2.6 km/s.

Edited August 24, 2015 by Nefrums

[Red Iron Crown]

You could do a tylo gravity slingshot followed by a laythe slingshot. Even without aerobraking that should put you in an orbit close to Laythes.

That's the method I used, with a small burn near Ap of the final orbit to set up the second Laythe encounter (though I suppose I could have waited a few orbits for it to occur naturally).

The Tylo and Laythe slingshot capture:

The second Laythe encounter, just after completing the burn:

Note that I use an outward slingshot of Tylo rather than an inward one, it is much easier to set up the Laythe encounter that way.

[Nich]

So the reason angled wings work is because the lift to drag ratio is better for the wings then the lifting bodies

Real airplanes use cambered wings that produce lift even when they are parallel to the flow however they have a rotational moment that makes them more difficult to stabilize.

[Val]

So the reason angled wings work is because the lift to drag ratio is better for the wings then the lifting bodies

I'd say, in KSP, yes. In RL, not sure.

Edit: Personally, I build my Mk2s with just the wings angled. So I only get benefit of the lifting body effect at low speed/high AoA. Take-off, landing, attitude changes, and re-entry.

Real airplanes use cambered wings that produce lift even when they are parallel to the flow however they have a rotational moment that makes them more difficult to stabilize.

True, but barring a few aerobatics airplanes with symmetric airfoils, I've never seen a RL aircraft that did not have AoI.

And modern supersonic airfoils have very subtle camber compared to subsonic, in my experience. I could be wrong, though, wasn't able to find much info either way.

Anecdotal evidence, I know.

Edited August 24, 2015 by Val

[herbal space program]

You could do a tylo gravity slingshot followed by a laythe slingshot. Even without aerobraking that should put you in an orbit close to Laythes.

Note that you should try to hit Tylo (and Laythe) when it is a perpendicular position in its orbit compared to the direction your ship is going. So that you ship is going the same direction as Tylo

http://i.imgur.com/ft8tYTk.jpg

With this approach I got captured at laythe after a gentle aerobrake at ~2.6 km/s.

Ahh. All my initial Tylo encounters had me coming in from the top with Tylo around 10:30 o' clock, then sending me close by Jool to a Laythe encounter on the other side. This always left me in highly eccentric orbits after both encounters, from which I couldn't seem to set up a circularizing slingshot of off any moon. Come to think of it, my second ship has a Laythe-Laythe trajectory that looks like it will work, and it hits Laythe right around 9 o' clock like your Tylo encounter. I should have realized that would work better for Tylo as well, but getting a Tylo encounter just where you want it is not as easy as it is for Laythe. I guess what I need to do is back up my initial set-up to my Jool midpoint through the magic of alt-F5 and try again...

Edited August 24, 2015 by herbal space program

[panzer1b]

Ahh. All my initial Tylo encounters had me coming in from the top with Tylo around 10:30 o' clock, then sending me close by Jool to a Laythe encounter on the other side. This always left me in highly eccentric orbits after both encounters, from which I couldn't seem to set up a circularizing slingshot of off any moon. Come to think of it, my second ship has a Laythe-Laythe trajectory that looks like it will work, and it hits Laythe right around 9 o' clock like your Tylo encounter. I should have realized that would work better for Tylo as well, but getting a Tylo encounter just where you want it is not as easy as it is for Laythe. I guess what I need to do is back up my initial set-up to my Jool midpoint through the magic of alt-F5 and try again...

Ive always found hitting laythe directly from interplanetary to be the easiest and least fuel hungry method provided your craft doesnt burn up (if you point radial/antiradial then the drag goes through the roof and you can usually slow down more then enough to get a laythe capture without frying). using this tactic ive pretty much got capita ships to laythe with very little fuel useage. really only with very weak ships that aerobraking is completely out of the question do i use the tylo method, its harder to set up, and always uses some fuel to get the encounter perfect, vs aerobraking direct only uses a bit of fuel once uve dragged ur owrbit down to what you want and need to circularize.

Then again, i have no idea why 90% of my ships have no issues aerobraking? Anything with wings can aerobrake super well, and even wingless capital ships still brake effectively if you go in pointing radial/antiradial, or normal/antinormal, exposing the largest cross section to the air.

[Nich]

I'd say, in KSP, yes. In RL, not sure.

Edit: Personally, I build my Mk2s with just the wings angled. So I only get benefit of the lifting body effect at low speed/high AoA. Take-off, landing, attitude changes, and re-entry.

True, but barring a few aerobatics airplanes with symmetric airfoils, I've never seen a RL aircraft that did not have AoI.

And modern supersonic airfoils have very subtle camber compared to subsonic, in my experience. I could be wrong, though, wasn't able to find much info either way.

Anecdotal evidence, I know.

Yes it is the same way in real life. A barn door has an L/D ratio but it is not nearly as good as a wings. I believe 8:1 was the breaking point that made powered flight possible

Supersonic wings have less camber and tend to be thinner (sharper on the front) to help transition through the transonic reagon.

<wrong>All modern commercial AC are designed to cruse with an AOI of less then 1. Climb and descent will of course departure from this.<wrong>

Edited August 25, 2015 by Nich