SSTO to laythe and beyond

[herbal space program]

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.

Hmm, have you actually done this in 1.0.3? At what velocity are you hitting Laythe's atmo? Because even from a high-AP Jool orbit, I'm exploding about 3 seconds after I hit Laythe's atmo, without even slowing down appreciably, regardless of my attitude. KABOOM! My whole ship is gone. Back in like 1.01, I seem to remember that by pitching a space plane up enough you could cheat the heat, but not any more I think. It seems like now you have to be coming in below 3km/s. i.e. from a fairly similar orbit to Laythe's, to stand a chance.

[Val]

...

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

That doesn't make sense. Angle of Incidence doesn't change during flight (unless it's a F-8 Crusader). Only Angle of Attack changes.

EDIT1:

By the way, most jets don’t cruise exactly level. I usually fly a B-777 and it cruises about 2 to 2.5 degrees nose high (as do most airliners I’ve flown) depending on altitude and cruise mach. This is likely the lowest drag attitude for the fuselage and might be due to that particular attitude providing a little profile lift to offset drag. Climbs at altitude will be a couple degrees more and descents will be a bit less. Basically, at altitude, the nose (attitude indicator) should always be between approx. 0 and 5 degrees.

...

This cruise angle becomes annoying to some pilots when trying to sleep in the bunk beds. The bunks are set up “head aft†(where the temp and entertainment controlls are). Some pilots will lay “head forward†because they are sensitive to laying “downslopeâ€Â. Hopefully, the 787 will have the bunks at a 2 deg angle to make them level in cruise (we’ll see how sharp those Boeing boffins are). For me, I sleep well either way. I love the plane. Anyway, this long example is to show you that we do fly a little nose high in cruise.

Capt BC

Doesn't mention Angle of Incidence, though. Edited August 25, 2015 by Val

[Nich]

Your right Val I was thinking of the AOA for the body. Not sure what that is called

Yes you are right all planes I can think of have an AOI so that when at cruse the body AOA is near zero (but slightly up). The AOI actually changes along the length of the wing to create more lift at the base (less bending moment) and better stall characteristics at the tips for control purposes. This change in AOI also helps with induced drag as more lift is produced in the middle and less at the tips

Doesn't really count but I am not sure how you would calculate AOI on a flying wing

Edited August 25, 2015 by Nich

[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.

Once I knew where I needed to put the encounter (thank you - I was ready for a spoiler on this), It was pretty straightforward to get it dialed in. I haven't actually put any of my ships through yet, but it looks similar to your picture. Trying to fine tune my approach from just before the Tylo encounter, I'm finding that if I come at Laythe's orbit from just outside and as close to the other side of Jool as I can, I get really long projected Laythe encounters that look like I'm almost getting captured directly into a prograde orbit. I'm tempted to believe that I can safely aerobrake directly in these encounters rather than swinging around to encounter Laythe again, since they look a whole lot slower than what I had before. That's what I'll try the first time through tonight...

Edited August 25, 2015 by herbal space program

[panzer1b]

Hmm, have you actually done this in 1.0.3? At what velocity are you hitting Laythe's atmo? Because even from a high-AP Jool orbit, I'm exploding about 3 seconds after I hit Laythe's atmo, without even slowing down appreciably, regardless of my attitude. KABOOM! My whole ship is gone. Back in like 1.01, I seem to remember that by pitching a space plane up enough you could cheat the heat, but not any more I think. It seems like now you have to be coming in below 3km/s. i.e. from a fairly similar orbit to Laythe's, to stand a chance.

Not in 1.03, but in 1.04 multiple times (my last stuff i aerobraked at laythe was a capital ship carrier thing, it was painful and i lost one claw on it, but it did brake with otherwise no damage to it fully in one try from interplanetary velocities (i dont rememeber what teh actual speed was, but laythe was going away from me and i bet the velocity was at least 4km/s as it was a direct kerbin->laythe shot.

From what i hear (i never actually aerobraked at laythe in 1.03) 1.04 uses a better more fair heating system that one, doesnt vaporize ships instantly when they tough outer atmo, and two, has 2 separate systems, max temp, and skin temp. Now, you can actually have weak components on your ship provided they are nowhere near the exposed part of the ship. Skin temps from experience never get above 2000 if i do it right, and the low heat tolerance components i tend to place inside bomb bays or other shielded areas (less drag, and well, you never want anything that has 1200 max temp exposed period as itll burn during the ascent from kerbin, parts easily get to near their frying point when im pushing 1500m/s at 20km to try and get as high and fast as possible before i need to waste rockets.

Also, in 1.0 i did multiple jool aerobrakes using fighter styled craft, it was quite possible despite over 8km/s velocities. It just took the perfect altitude, too low and boom, too high and it doesnt do jack when it comes to altering the craft's speed. Finally, while im not 100% sure, i belieev some of the planets atmosphere heights have altered, so that could also be burning you.

[Val]

You're right, Val. I was thinking of the AOA for the body. Not sure what that is called.

It is also called AOA for the fuselage.

Yes you are right all planes I can think of have an AOI so that when at cruse the body AOA is near zero (but slightly up). The AOI actually changes along the length of the wing to create more lift at the base (less bending moment) and better stall characteristics at the tips for control purposes. This change in AOI also helps with induced drag as more lift is produced in the middle and less at the tips

Doesn't really count but I am not sure how you would calculate AOI on a flying wing

Angle of Incidence is the angle between airfoil cord and the fuselage. And that doesn't change intentionally in flight (except for the above mentioned Crusader or if your wings are very elastic and you abuse the aircraft)

Source: General Aviation Aircraft Design: Applied Methods and Procedures, Page.327 (Edit2: fixed link)

But how to calculate AOA on a flying wing with geometric wash-out, as you describe. I don't know. It's easy enough for a wing with aerodynamic wash-out, since there's no difference from root to tip there. My guess is you'd use the wing root as reference, like you do for Angle of Incidence.

Edit: Actually, since you (or the aircraft's designer) know what the difference between root and tip AOI is, then it should be easy to calculate the AOA on an arbitrary point of the wing, if you know the AOA at either the root or the tip.

Edited August 25, 2015 by Val

[panzer1b]

I have a question to the pros:

Why does a very shallow ascent get you more dV in orbit then a less shallow one? Ive had the most luck with lighting the nuke at ~25km, and keeping a generally shallow angle of climb at ~15 degrees. It seems that unlike 0.90 or before, the drag more or less becomes so low above 30km that you can ignore it with a rather sleek and well made craft (provided you didnt go overboard on wings, radial stuff, ect).

Anyways, my example of this is my HK-201, ive gotten the best results with a approach where i go up to 15km asap, and then gun it without climbing to 1.5km/s, then increasing angle slowly until im at around 15 degrees up when i need to light the nuke, and keep this lateron as well. The craft is ~23t when it lights its nuke, so not the best TWR either, but i seem to do much better with the lower and faster approach compared to the usual 30 degrees up and get out of atmo asap approach most people suggest, any ideas why this is the case?

[Kaezan]

I have a question to the pros:

Why does a very shallow ascent get you more dV in orbit then a less shallow one?

You dont need to be a pro to answer that.

Kerbal atmosphere model is (at least trying) to recreate the real Earth atmosphere.

Check this wiki page, you should understand after that.

https://en.wikipedia.org/wiki/Gravity_turn

[panzer1b]

With weapons stripped off, it had 3000 dV remaining in the jool system.

having 5.4K dV in orbit sure is nice (is say 4.4K is the least you can afford to have in LKO if you want to go to laythe and get back to kerbin).

This was on a DMP server, had a friend flying alongside. Amazing craft if you strip the weapons off and ditch the docking gear (and even with that stuff it still has in excess of 4.6K dV if you do the ascent right).

[Red Iron Crown]

panzer1b, are you ever going to update the OP with the entries your challenge has received?

[panzer1b]

panzer1b, are you ever going to update the OP with the entries your challenge has received?

Done.

And i just managed to pull off a 6450m/s dV in LKO craft (although its not nearly as efficient as i was hoping for)

Made it to laythe in a upgraded version of me HK-201 and i was about to return to kerbin but game ate my save file and my last save was corrupted too (didnt want to redo the entire bloody return trip when im positive the craft would have survived reentry that i had done a hunder times already anyways from jool to kerbin).

I gotta get better with grav assists and perhaps i can even land on pol or bop while im at it since it has plenty of dV even with horridly inefficient return.

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This i actually believe has the dV to pull off a mission to Bop or Pol (or even both if i use PLAD's eve route to cut down the dV for the one way trip to near 0). I really need to get better with grav assists, its free dV i cant seem to use too well (mostly rely on luck and minor correction these days, cant seem to actually do a good grav assist thats lined up well with destination).

Edited September 7, 2015 by panzer1b

[Nefrums]

The rerun trip can be very cheep with the help of gravity assists. jool->kerbin can be done in less than 300 dv.

[Candlelight]

Nice!

I am so dumb i would never be able to even think of doing this.

[Nefrums]

The ship looks very nice. Are there a Nerv and 9 liquid fuel fuselages clipped into that cargo bay?

6450m/s dV in LKO is realy alot, one can do amazing things when clipping stuff into cargo bays to negate any drag.

Edited September 7, 2015 by Nefrums

[panzer1b]

The ship looks very nice. Are there a Nerv and 9 liquid fuel fuselages clipped into that cargo bay?

6450m/s dV in LKO is realy alot, one can do amazing things when clipping stuff into cargo bays to negate any drag.

Its powered by a nucler rapier drive (what i call a rapier with a nuke attached to the end node). The entire craft is ~30 tons (ive managed to get 35 in orbit on one rapier but its so painful its not worth it and the extra dV is negligible at that point). As for the bay, it has a massive stack of FLT-100s that have been swapped to pure LF capacity (using a mod that lets me pick fuel types and how much of what is in a tank). I know there are many that would consider this cheating, but i couldnt care less when i design mostly sci-fi inspired craft (notice how everything i make has rear cockpits, ive yet to see anything but prototypes in real life use rear cockpits), so i just dont care anymore. The toughest engineering feat right now is making good looking craft that ALSO fly well. I seem to be a fan of compact designs (this one is kinda inspired by my older M-Fighter line, just that i added a bomb bay and shortened the nose (used to be a mk1-2 short and mk1-2 long adapter + same cockpit/engine layout, with new aero no more external missiles ofc).

Actually now that i think about it, the primary reason i used so many small fuel tanks inside is because i absolutely refused to fly a craft that was unable to carry some weapons internally (even if the laythe version had weapons stripped off). The FLT-100 is the largest tank that will still let me drag 2 0.6m torpedoes to the sides of the MK2 bomb bay. Id replace those stacked fuel tanks with the 400 LF tanks, but i cant do that and have weapons inside as well. I might make a minimalistic design with edited fuel tanks in the future though, since i really like to have room in the cargo bay for more weapons (3-4 missiles in there would be so nice), but that is cheating even for me since you essentially get free fuel for no dry mass. The only part that would make me change my designs would be a MK1 bomb bay, that would be amazing even if it only carried 1 missile, i could actually make a super small fighter with internal weapons capabilities.

Im defenetely going to try to think of a new idea though for the HK-201S, ive already redone the wing layout (and swapped more wings for wet wings due to the free fuel in them for no added dry mass), and make it more maneuverable for less part count and still able to land on Duna albeit with difficulty due to the terrain being so bumpy. Sadly engines will stay the same as i see no viable alternatives that get you similar dV (ions will get you more but i refuse to fly anything that has less then 2Kn thrust per ton at a bare minimum (that is what, 30 bloody ion engines right there not counting any of the massive part count batteries and fuel tanks too). I may make a cheaty craft for use in fleet operations though by editing fuel tanks to have capacity based on volume i see (so the MK1-MK2 adapter would have in excess of twice it current capacity). Thats my usual solution to dealing with part counts, but it does give me more dV then normally since less dry mass by removing fuel tank weights, although wish there was a way to say edit the fuel tank weight without mods like you can fuel capacity in the craft file so i could have say twice the dray mass, twice the fuel in a single part (already i have a mod that lets me swap fuel amounts in game).

If anyone has any tips to improve my design id be glad to hear them, right now its more or less reached its maximum potential (i have managed at a absolute max ~6600dV using a ridiculous 35 ton build i miraculously managed to get into LKO no idea how though).

As for flight itself, the biggest problem for me are those grav assists, does anyone have a good guide or something for it? Like for example the last thing i wanted to do is to go from bop/pol and direct shot to kerbin. I actually managed to get to Bop surface and land near kraken (i accidentally smashed into it 1st time as i didnt realize it had a hitbox), and i had ~800 dV left after getting back into Bop orbit, more then enough to get to Tylo, but nomatter how many times i tried i couldnt get it to actually line up in a useful way to actually eject me to kerbin (always either wrong direction, or made my orbit smaller then larger).

Ive always been very good at getting to jool system, but returning is hard, VERY hard unless you have the fuel for a hohman burn.

I have done PLAD's route once before but that was relatively easy as its a matter of reverting alot of quicksaves and just leaving for eve at a very particular date/time, and then following the right procedure, but setting up a useful grav assist without timetables is tough. How do you do grav assists on the fly, (and can they be used to get a inclination close to a planet of interest?). I feel that i could easily pull a Bop and Pol trip alongside the usual laythe expedition, but i need some help with how to actually take advantage of grav assists as i dont have that much raw dV to hohman everything.

[Val]

...

If you ask me, the whole concept of a fighter with range to go to Jool/Laythe doesn't make sense to me. It takes years to get from Kerbin to Jool, even longer if you use gravity assist. Any threat that fighter is sent to deal with is likely to either have finished their business and gone elsewhere or had time to reinforce their position long before you get there. What you really need is a warp drive.

[panzer1b]

If you ask me, the whole concept of a fighter with range to go to Jool/Laythe doesn't make sense to me. It takes years to get from Kerbin to Jool, even longer if you use gravity assist. Any threat that fighter is sent to deal with is likely to either have finished their business and gone elsewhere or had time to reinforce their position long before you get there. What you really need is a warp drive.

I kinda envisioned it as a so called "universal" do anything fighter. That and im trying to recreate the glory days on 0.90 where i had a craft, the HK-303 "Tri-Fighter III", was the pinnacle of anything ive ever made, it had EVERYTHING, maneuverability, insane TWR, insane range, could land ANYWHERE (even Tylo with refueling in orbit), and had the dV to do a laythe roundtrip + land on minmus (all while carrying weapons). Yes i know those days are gone, and that you nolonger can pull off such a trip since you now actually need rockets to go orbital (ive managed to get 2-300km AP often with pure jets before), but this thing is my attempt at creating a new "universal" fighter craft that can do near anything.

Right now i have everything i want except low mass, but since nukes were increased by a ton, and jets in general are way heavier now, its hard to make lighter craft with such incredible ranges (was fun when jets were 1.2t and nukes 2t). Im still exploring options, but it seems that ions are the only way to make a super tiny craft. My much older MK1 fuselage craft was quite good, but it had no weapons (hence the requirement for the MK2 body now).

And yes, im quite aware there is no practical reason for anything i build, i just enjoy pushing the limits of the game (without blatant cheating, had i embraced going past the limits id have every craft running on a Kraken-Drive for near infinite dV in space). That and since im a military builder, nothing that leaves the hangar except a medical frigate or something like that is unarmed.

[herbal space program]

So I finally managed to land all 4 of my ships on Laythe, all in (more or less) the same spot:

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I'll post a bunch more images when I'm all done. As it turns out, my plane was nearly impossible to land without knocking the center Rapier off, something I REALLY should have tested back on Kerbin . My stall speed was also alarmingly high, so it was quite difficult to set it down gently enough without any thrust. DeltaV from LKO to the ground on Laythe ranged from 1355 (based on nuke ISP) for my best ship to 1612 for my worst, in all cases significantly less than just getting to Jool's SOI on a straight Hohman transfer would have cost. I've gotten one of the four ships back to Laythe orbit with 1.8km/s left in the tank, which should allow me to hit some other destination. My best ship should have at least 2.1km/s left back in Laythe orbit. I'm tempted to try Duna, because the 2 nukes should be enough to lift me there, but we'll see. Transfer to a Tylo slingshot costs me only ~685 m/s by my estimates, so I should have a decent amount left to play with. Anyway, it's been quite a challenge, but I can't imagine any part of what remains will be as hard as landing those hastily designed planes on Laythe was.

Edited September 8, 2015 by herbal space program

[Val]

Very nice pics. Looks really awesome with all those planes. And quite the feat to land them all so close to each other. Well done!

... As it turns out, my plane was nearly impossible to land without knocking the center Rapier off, something I REALLY should have tested back on Kerbin ...

If you mount your wings with Incidence, then you don't need to lift the nose so high during landing. And it reduces fuselage drag, too.

BTW, those swept wings, you're using as wing tips, are twice as heavy as other wings. Any specific reason you're using them?

[panzer1b]

When it comes to knocking off engines, i like to have a landing gear in the back to prevent this (kinda like those tiny wheels on drag racers to keep em from flipping), i either mount my main gear in the back, or if that isnt possible, i just add a small gear there clipped into the rapier as a backup (its minor drag and it doesnt look bad).

Anyways, while i know this is COMPLETELY OVERKILL and 100% POINTLESS, im still continuing development of this bloody SSTL fighter that has now gotten 5500dV in LKO on my last attempt (with 1.5t of missiles onboard). Youd be surprised how much better it is with RCS systems removed (its harder but not impossible to dock due to nice reaction wheels and well, low enough thrust you can kinda just play with it until you line it up). I also swapped the medium docking port for 2 small ones (which double up as both docking ports for fuel transfer (provided mothership doesnt have a claw), and extra missile hardpoints for long term combat missions.

here it is ascending to orbit, notice the new docking ports on the front, and the redesigned wings (apparently delta-deluxes suck, this layout gets me better performance, less drag, and gives me much better maneuverability (its not gonna dogfight in atmo but its way less like a pig strapped to a SRB aerodynamically). With half fuel, i can actually do ground attack pretty well (fully fueled+weapons loaded is still a nightmare to fly).

One more thing that ive realized is that fuel lines (provided you dont mind some manual pumping) are useless, extra mass you dont want, and to top it off, they make craft laggier to some extent. Its a little tedious to have to shift fuel, but it lets me both be more precise with CoG (which i had to mess with before anyway), and well, its not like the nuke burns fuel so fast that i cant keep up with it.

Finally, does anyone have any tips for longish (~6-8 minute) burns. While i know you can do it in stages for max efficiency, when you burn in one shot, is it best to do it from a somewhat higher orbit, burn prograde, burn at the little target marker (the blue thing), low orbit, try to maintain your PE constant? I know low TWR will always lead to losses (unless you burn in stages using short bursts of dV here and there every time), but what is the least wasteful method to do such burns that are short enough to actually do in 1 shot, but are long enough to be impossible to do near the node quickly?

[herbal space program]

Very nice pics. Looks really awesome with all those planes. And quite the feat to land them all so close to each other. Well done!

If you mount your wings with Incidence, then you don't need to lift the nose so high during landing. And it reduces fuselage drag, too.

BTW, those swept wings, you're using as wing tips, are twice as heavy as other wings. Any specific reason you're using them?

Thanks! Lining them all up wasn't so hard, but not knocking off the center engine was so difficult that when one of them rolled to a stop in one piece a few hundred meters away, I decided to call it good enough. As to your design advice, I actually spent yesterday evening trying to use all the stuff I learned from you and others in this thread to improve upon that plane, and this is what I came up with (SSTO14):

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It has significant positive AOA in the wings (all wet) relative to the fuselage, and uses what seems to be the most efficient configuration, 2 Rapiers + 1 nuke. It thus has only 3 fuselages vs. 5 to further reduce drag and uses all winglets and canards to steer. I used the small hardpoint to center-attach the fuselages, mounted the rear wheels lower and further in, and added two pairs of struts front and back to increase the rigidity of the airframe. The resulting plane flies much better than the previous version. It weighs 41.4t on the runway, 13.4t empty, and as you can see from the pictures, it reached orbit on my first successful try with almost 5.9km/s deltaV left, a number I think I can still improve slightly upon. I believe this is close to the best one can do without resorting to cargo bay or part clipping abuse, but I haven't really scoured the forum for better performance. As to the swept wings, I just didn't notice they had worse numbers than the others. It looked to me like they were all the same, so I stopped paying attention. Anyway, it's been fun learning! I'm tempted to run this new plane through the challenge, but I only have so much free time...

Edited September 9, 2015 by herbal space program

[Val]

... It has significant positive AOA in the wings relative to the fuselage.

The angle between wing and fuselage is called Angle of Incidence (AoI)

... the most efficient configuration, 2 Rapiers + 1 nuke. ...it reached orbit on my first successful try with 5.9km/s deltaV left.

That is extremely impressive. Well, done. It's such an awesome feeling when a design turns out to be great.

And I agree, that the 2:1 engine layout probably is the most efficient. I just couldn't deal with the low TWR, which is why almost all of my designs are multiples of 1:1 or 3:2. The highest dV I got was 5.7 km/s, but I never ran it through the challenge.

It'll be interesting to see if you can break 6 km/s with a non-clipped design.

[panzer1b]

The angle between wing and fuselage is called Angle of Incidence (AoI)

That is extremely impressive. Well, done. It's such an awesome feeling when a design turns out to be great.

And I agree, that the 2:1 engine layout probably is the most efficient. I just couldn't deal with the low TWR, which is why almost all of my designs are multiples of 1:1 or 3:2. The highest dV I got was 5.7 km/s, but I never ran it through the challenge.

http://i.imgur.com/YUWgoPl.png

It'll be interesting to see if you can break 6 km/s with a non-clipped design.

Ive managed to get ~5.7km/s dV with a 99% legit design (stack of fuel inside a mk2 bomb bay), but that craft carried 1.3t of missiles into LKO as well and was ~29 tons total on the pad.

My absolute maximum ive pulled off with a bloody 35 ton craft pushed by one rapier was ~7000dV. That was one bloody pain to fly though as 35 tons takes FOREVER to accelerate to supersonic, although once past the drag wall it actually doesnt fly that badly.

[herbal space program]

That is extremely impressive. Well, done. It's such an awesome feeling when a design turns out to be great.

I hate to admit it after you said all that, but I had my dry wt. wrong in both my spreadsheet and my OP. Actual dry wt. is 13.4t, I had 13.1 in the sheet, so dV on LKO was really only 5852 . Anyway, I still think I can improve on that, so 6km/s is not out of the question. As to the low TWR, I agree it's a drag. It limits where I could land after Laythe, for example I don't think Duna would work with only 1 nuke. It also makes getting to orbit quite a bit more difficult, to the point where adding the extra nuke significantly (but not quite fully I think) offsets its own weight by letting you burn less LFO on the way up. I feel like with a 2:2 setup I could make it with almost no LFO burn at all, but of course the higher dry weight knocks off quite a bit of dV at the back end.

Update -- after tweaking the ship a bit and making a few more attempts last night, I was able to get on LKO with 5917m/s, with 75 units of Ox left in the tank. The plane also lands quite well back on Kerbin, even mostly full. I could probably push this just above 6km/s if I replaced some the oxidizer with LF, but I want to keep that in case I need more power than the nuke can give. With that amount of dV on LKO, I think a Laythe-Duna-Kerbin return tour is feasible. I might just have to try it now...

Edited September 10, 2015 by herbal space program

[panzer1b]

I hate to admit it after you said all that, but I had my dry wt. wrong in both my spreadsheet and my OP. Actual dry wt. is 13.4t, I had 13.1 in the sheet, so dV on LKO was really only 5852 . Anyway, I still think I can improve on that, so 6km/s is not out of the question. As to the low TWR, I agree it's a drag. It limits where I could land after Laythe, for example I don't think Duna would work with only 1 nuke. It also makes getting to orbit quite a bit more difficult, to the point where adding the extra nuke significantly (but not quite fully I think) offsets its own weight by letting you burn less LFO on the way up. I feel like with a 2:2 setup I could make it with almost no LFO burn at all, but of course the higher dry weight knocks off quite a bit of dV at the back end.

For Duna ive managed to land and takeoff ~20 tons of craft with a single nuke (and unpowered landing can be done with some difficultly based on skill and where you choose to land).

As for Duna it really depends on your wing area, ofc if you have barely enough to fly on kerbin you are forced to parachute land or burn on the way down, but otherwise it shouldnt be too big of a deal (my current HK-201/S has ~9 lift rating total and ive landed that on Duna with nearly full fuel (~25 tons) with no power. try to aim for the valleys, they are less bumpy, easier to land in (although lower altitude so you need a hair more dV to get back to orbit).

As for extremely low TWR, i agree with you that going excessively low can actually kill your effective dV due to teh sheer time you need to burn (one thing ive learned is that with very heavy loads pushed by bad TWR, bringing some oxy despite its horrible inefficiency yields more dV in orbit as you dont spend so long burning at low alt). Most of my SSTLs have room for ~500 oxy (so i can have a boost from mid gravity worlds without an atmo that would let wings do the work), i normally use ~100-200 for ascent, and if i know ill be landing on a tough planet i dont bring as much LF and bring extra OX to help near the ground (this has saved my arse multiple times from badly timed suicide burns). Heck, even for interplanetary burns a thrust much less then 2 kN per ton of ship drags out your transfer burns so much that you loose alot of benefits from the whole planet gravity at a low PE. I think that the lowest one can go within reason and not be severely limited (or wasteful with dV) is ~1-1.5kN/ton. That means that you need at a bare minimum 1 ion engine per 2 tons of mass, or 1 nuke for 40 tons. Myself, i like to have 1 nuke for ~20-25 tons (although i have gone with less TWR then that for long range designs), since it lets me get decent range, and at the same time it lets me land/takeoff from the majority of planets/moons aside from Tylo, Eve, kerbin (unless jets ofc since single stage from teh launchpad), Jool, Kerbol, and possibly Moho (although ive yet to actually get there in a single stage aircraft style build).

Im now working on a new ship, a SSTE (single stage to eeloo) which will HOPEFULLY be able to get to eeloo, land, and get back in orbit without any refueling (although the dV requirements to even get there arer so high there is no way to make a roundtrip without grav assists since you need to burn both ways, no aerobraking availeable). Im gonna try to use my 7K dV version to build off of (and i need to reduce dry mass since 7K isnt gonna cut it).

Also, i know that this isnt really as great an accomplisment as your designs (since its super heavy on clipping), but hey, how is 7329m/s dV not incredible from a NUKE ONLY vessel? All that with reasonableish TWR considering how heavy the craft itself is. That and its actually my style (it took forever to balance it right so its stableish and all, rear cockpits are just so hard to work with since you have nothing to really offset engine weight with).

Unless my math is crap, it has 7329dV in a ~80km orbit. This is SO being sent on a trip to visit laythe, bop, pol, and possible minmus if i can squeeze out that dV.

Btw, if i plan to visit Bop and Pol alongside laythe, what is the most efficient order to do this in? Is it best to go to laythe 1st since i can do a direct laythe aerobrake from kerbin trajectory? Or is it best to leave laythe for last when im lower on fuel and hit the other planets 1st?

Edited September 10, 2015 by panzer1b