Micro-challenges for all! (Continuation of Newbie Central.)

[Dark Lion]

Reactions to @AeroGav 's entry:
Pic 1 - Huh. I though I over-engineered my entry...
Pic 2 - OH. I didn't. 
Nice. 

[AeroGav]

9 hours ago, Dark Lion said:

Reactions to @AeroGav 's entry:
Pic 1 - Huh. I though I over-engineered my entry...
Pic 2 - OH. I didn't. 
Nice. 

Is anyone else finding CG problematic ?  Can't put crew cabins too close to the front,   nervs need to go forward but their exhaust must clear the wings...

As Faith No More once sang,  in "A Small Victory"

Quote

"It shouldn't bother me (no)
It shouldn't bother me (no, no)
It shouldn't bother me
It shouldn't but it does

My demo live build video managed to solve this with a conventional enough layout when there was only one cabin,  but two  makes it hard ! 

My  entry for the actual challenge ended up as a bit of a Kludge,  and I felt unsatisfied.  Is there a more elegant solution ?

Today,  I tried violating my own house rule on biplanes, and made this,  the KAAB Friggen  (SAAB Viggen, geddit ?)

There is an equal number of strakes above the wing as below it, so it doesn't have large CoM changes as the fuel burns.   We have a bit of a tunnel, for our NTR exhaust, and it results in an incredibly compact vessel (still tips the scales at 25 tons though).

It's nicer to fly than the Me 163 Komet lookalike, though not quite up there with the Sparrow demo craft or the Vagabond SSTO conversion i did,  which automagically pitch themselves to 5 degree AoA when you take SAS off.   This thing wants to pitch down slightly at sonic speeds and i couldn't get 5 degrees (more like 2 or 3) without having excessive pitch up when subsonic, which messes with the ability to get supersonic in the first place.

I guess you have to actually fly the thing, damn.   Eventually i put a tiny trim flap bound to action group one,  with pitches the nose up slightly.   It's deployed by default to aid takeoff, but can be turned off for most of the airbreathing flight (you want the nose to stay down and go fast) then deployed again when you've started the nukes and no longer need to stay low enough in the atmosphere for the jet to get air.

https://kerbalx.com/AeroGav/KAAB-Friggen

Oh well,   keep searching for an elegant solution i guess.  Join the dark side and make a mk2 fuselage ship?  Noooo

 

[obney kerman]

22 hours ago, kerbalstar said:

Er... @obney kerman, @AeroGav?

No.

[sturmhauke]

Ok, I won't make the Atomic SSTO as an official entry then. But I'll probably still make one for great justice.

[Dark Lion]

2 hours ago, AeroGav said:

As Faith No More once sang,  in "A Small Victory"

You wanted out, but you can't help it.♫
So you go ham and "Friggen" land on Minmus to rescue my kerbal.

[AeroGav]

A couple of Hangar Queens, that have never seen the light of day

Might be too draggy.  Also NERVs clipped into fuel tank - naughty, naughty

.

Engines above and below the cabin, Genius !  I thought it would end up looking like a hammerhead shark, but that wing profile is kind of nice.   Unfortunately,  too few cabins for the amount of engines (it really is overpowered at this point).   Fuel fraction is too low, even before we add extra cabins.   And not enough wing area for weight, even before we add cabins and fuel. Particularly, not enough wing area forward.  I've been trying so hard to get my CG forward, and now that i succeeded,  i can't bring CoL far enough forward to match - this is gonna be a lawn dart.

So, to progress this unexpectedly aesthetic design, i've got  to hit it with the ugly stick and dump a whole load of extra strakes.   Could i clip them into the fuselage and handwave as wing/body blending (turns to the Dark Side of the force)....

[sturmhauke]

Well I made this monstrosity. It got to space well enough, but on landing it put a crater in the runway.

[AeroGav]

2 hours ago, sturmhauke said:

Well I made this monstrosity. It got to space well enough, but on landing it put a crater in the runway.

What if you add more strakes in place of cylindrical tanks, any way to get more lift without messing up CG?   Also what if you swap some rapiers for panthers (lighter)?

The Hammerhead design is finished.    About 1900dv.    Lift/Drag ratio is not amazing, doesn't go above 3 supersonic, maybe because of all the fuselage parts and the wings don't have an incidence angle on them.  But, it's got enough power and fuel to overcome that.   Now to see how far i can actually take the thing.  I'm rubbish at orbital maneuvering.

Edited October 5, 2018 by AeroGav

[AeroGav]

OK,  it turns out Minmus is about as far as it can go, fuel is very tight in fact, i wouldn't want to do it unless you got some orbital infrastructure for refuelling.  Getting there is easy enough, but getting back to Kerbin a bit doubtful.  Obligatory "clown car" shot, 43 seats.   This took a long time to do !

On re-entry, i managed to stretch the glide all the way across the desert and reach the space centre.   We're only gonna get one shot at the actual landing though

Well,  we were a bit too high to land directly but didn't quite have enough for a circuit.   Cut the circuit short and tried heading straight for the space centre and, you can say we definitely got to the space centre.  In fact this is much shorter walk back to the astronaut complex,  those that could still walk  

Anyway, time for me to stop cluttering this thread !  Finished vessel https://kerbalx.com/AeroGav/Hammerhead5

Edited October 5, 2018 by AeroGav

[Alchemist]

Yeah, this isn't something I'm experienced with. I once had a series of RAPIER-powered SSTOs, but then that got nerfed. Jets + NERVAs? Let's see what can be made useful... maybe something based on the crew shuttle?

Well, it works. May require a few ascent profile optimizations, but it gets up there and can carry 36 Kerbals.
I'm naming this vessel Ku-104 (ever heard of the element Kurchatovium? no? I've seen Mendeleev's tables with it. Yup, made in USSR)

first I've tried to build a transport shuttle SSTO and couldn't get satisfactory performance (may get to orbit, but not much capacity to carry anything left), so I tried applying the tech to a crew shuttle design - and it just worked straight away

[sturmhauke]

I've tried that arrangement of Big-S wings before, but they seem to fall off too easily with just autostruts. I had to use hard struts, which looks bad and adds drag. Is there some trick I'm missing?

[Alchemist]

BigS wings falling off Mk3 hull at minimal load, at least if landing gear is on them - that's likely some sort of nasty bug (could be clipping related). Ran into it quite a few times.

Anyway, on this ship I haven't even autostrutted the wings (and they don't even tend to flap). Other than the fact the piece that is connected through 2 other pieces (the one with the innermost elevon) is the one carrying the landing gear (which, to think of it, may also be preventing the gear-on-wing bug)

 

[sturmhauke]

I've mostly seen it happen when I attach one Big-S to another, especially when it's a couple layers deep.

[Alchemist]

Also, an excessive amount of struts (both normal and automatic, and in addition to normal connections) if pretty much in the same plane may actually be making things worse, they may even try to reshift the structure out of plane in a new 3d shape creating massive structural failure. BTW, the bug I've typically encountered has often resulted in the first structural failure logged being halfway across the vessel

[AeroGav]

1 hour ago, Alchemist said:

Yeah, this isn't something I'm experienced with. I once had a series of RAPIER-powered SSTOs, but then that got nerfed. Jets + NERVAs? Let's see what can be made useful... maybe something based on the crew shuttle?l, it works. May require a few ascent profile optimizations, but it gets up there and can carry 36 Kerbals.
I'm naming this vessel Ku-104 (ever heard of the element Kurchatovium? no? I've seen Mendeleev's tables with it. Yup, made in USSR)

first I've tried to build a transport shuttle SSTO and couldn't get satisfactory performance (may get to orbit, but not much capacity to carry anything left), so I tried applying the tech to a crew shuttle design - and it just worked straight away

Very good !   If you want to optimise it further,  my only suggestions would be (in decreasing order of importance)

1.  Those mk1 tricouplers are extremely draggy.  They are light but have many times the drag of a 2.6m tricoupler

2.  As far as i can tell,  you're using a mk3 engine mount on the back of the fuselage (space shuttle style).   You have a 2.5m quad coupler attached to the central , large 2.5m attachment node and you aren't' using the three 1.25m engine mounts.  Empty attach nodes  generate the same drag as a missing nose cone on the front .  Also, the quad 2.5m adapter has twice as much drag but only 33% more engine than the triple, which is why my preferred mk3 arrangement is this -

I am using all 3 1.25m attachment points,  and the central big node as a 2.5m tricoupler with another 3 engines.         Maybe do this and get rid of the horrible 1.25m tricouplers you have either side of the main fuselage?

You could angle the wings up a bit (https://en.wikipedia.org/wiki/Angle_of_incidence_(aerodynamics)    this enables the craft to fly on Prograde hold like in the picture above,  and it greatly reduces the drag from the fuxelage (which is most of the drag in Kerbal Space Program).   However, this can make it difficult to fly the correct flight profile - you end up fighting the airplane's tendency to climb when trying to get max speed out of your jet engines

4.  "Small Beer"  - bearing in mind what i said about empty attachment nodes generating drag,  that is why i attach nose cones to the back of my NERVs then offset them inside the engine so as not to block the exhaust.  This is probably quite minor compared with the drag from that big fat fuselage.   Sometimes I skip this step to keep part count down 

5. "Very Small Beer" - Could a single Vernor thruster replace the 6-8 monopropellant RCS I see on the nose ?  Would be less drag and lower part count

 

 

 

@sturmhauke  @Alchemist   

Re:  Wings falling off

My chemical fuelled version of the 225 seat Monstrosity suffers from this.   You have to pitch up VERY gently with trim ( ALT S) only on takeoff, or the wings come off.  If you pitch up too  much, the wings snap off, not enough, she goes into the water. 

The NERV version of this ship (the one i pictured above when discussing your engine mounts)  does not have this problem,  but they have the same fuselage.    The Liquid Fuel only version is actually lighter -  245 ton instead of 305 Ton  because of all the oxidizer the chem ship is carrying, though in orbit this switches around again as the oxidizer will have burned off while the NERVs are still there.    Also, the NERV version has 14 pairs of Big S wings,  the Chem version only 8,   so the amount of force each wing has to generate to take off is less,  which avoids overstressing the joint.

[Kerbalstar]

Wow, lots of great entries!

[TheFlyingKerman]

 

That's enough lumbering spaceplanes...

https://kerbalx.com/TheFlyingKerman/R-XA-NervWhiplash-LKO-Tourbus

 

Spoiler

Ascend profile:
1. Lift off at full thrust (with just jet engines), turn 10 degrees east when speed reaches 25m/s. Engage prograde lock.
2. Wait until the rocket stops accelerating, which occurs at around 20000m, turn on the NERV rocket engines.

3. Set throttle to zero when Ap is greater then 72000m and coarse.
4. Circularize at around 35s before Ap. Open the service bay to recharge the battery.

Reentry profile:
1. Retro burn at 1/3 orbit from KSC until Pe is zero. Then shutdown the NERV.

(The flag marks KSC)
2. Follow radial out until 50000m

3. Deploy aileron (AG2) and keep nose up at 10-15 degrees. The craft automatically keeps this angle with SAS off.

4. Glide to KSC. Use the jet if necessary. At this point the rockets flies like a very nose heavy aircraft.
5. Deploy parachute when over KSC and the service bay door (for additional drag). Perform a parachute assisted powered landing.

 

 

Edited October 6, 2018 by TheFlyingKerman

[Dark Lion]

1 hour ago, TheFlyingKerman said:

That's enough lumbering spaceplanes...

Ahem. I did not lumber, nor did I spaceplane!
But I did thunder, and I did space-- uh... plain... ly... 

Also, you used more wings than I did!
 

[AeroGav]

You know,  in all this scratching around for the most elegant 4 passenger design,   I never considered the obvious - stretching my original concept "Sparrow" 3 seater,  and simply mounting the wings to the outside of the NERV nacelles so as to not have worry about clearance issues.    THe thing is, in previous version of KSP,  issues with the physics engine meant that attaching wings to something other than the main fuselage stack would cause the plane to constantly roll to the left or right by 1 or 2 degrees per second throughout the flight - seriously annoying.       This bug does not appear to be active right now,  but in the past i have built craft in this way that were apparently free of the bug,  only for them to start rolling once KSP updated.   The only cure was to remove and reattach the wings in SPH,  which got pretty tedious.

 

Not only is this the simplest variant, it has the most delta V.

https://www.dropbox.com/s/tmv3lf1lot3ga82/sPARROW super.craft?dl=0

Are there any other craft out there people are working on ?   What's proving to be the sticking point,  drag,   controllability ?    I'm bored and would love to help !

 

 

[Dark Lion]

7 hours ago, AeroGav said:

THe thing is, in previous version of KSP,  issues with the physics engine meant that attaching wings to something other than the main fuselage stack would cause the plane to constantly roll to the left or right by 1 or 2 degrees per second throughout the flight - seriously annoying.

Time-warp does this to me all the time and re-attaching the wings doesn't seem to kill it. Strategic use(s) of auto-strut often has great benefits though. 

 

7 hours ago, AeroGav said:

What's proving to be the sticking point,  drag,   controllability ?

For me, it's aesthetics. I'm uber-picky about how my planes look, but KSP doesn't care how sexy Mk2 parts are, they're still generating far too much drag for a practical spaceplane approach. The line between dV and a perfect flight to orbit is just too fine for my design, no matter how over-powered and light I try to make them. I still end up needing just a short burst of oxi to kick out of the atmosphere. The moment I swap Mk2 for Mk1 parts, however... I'm pretty much already in orbit with the maiden flight.

This hereby concludes my Mk2 drag-level complaints. 

[AeroGav]

8 hours ago, Dark Lion said:

For me, it's aesthetics. I'm uber-picky about how my planes look, but KSP doesn't care how sexy Mk2 parts are, they're still generating far too much drag for a practical spaceplane approach. The line between dV and a perfect flight to orbit is just too fine for my design, no matter how over-powered and light I try to make them. I still end up needing just a short burst of oxi to kick out of the atmosphere. The moment I swap Mk2 for Mk1 parts, however... I'm pretty much already in orbit with the maiden flight.

This hereby concludes my Mk2 drag-level complaints. 

If you have a look in my KerbalX history, it is possible to make liquid only mk2 designs,  but you might say you have to do things that compromise their looks so much it's not worth it.

By that I mean

1.  The MK2 fuselage parts have to be kept to a minimum, so it ends up a stubby fuselage with a huge mass of Big S wings and strakes grafted on.   Definitely do not add mk2 parts for fuel storage  - keep all your liquid fuel in wing parts.   When you add mk2 fuel tanks to the design, it ends up getting to space with LESS space fuel than with no tank at all , due to all the drag.

2.  Pointy cockpit is at risk of overheating on the optimal liquid fuel ascent profile.   Sure , if you climb steeply, zoom above 27km at no more than 1000 m/s,   switch to RAPIER close cycle mode to get over 35km before the craft hits mach 5,  you won't see any heat bars, but you'll barely have any fuel left.     So,  you end up using the mk2 inline cockpit,  and none of the nose options are particularly great looking.

3.  Engines at the back looks sleekest, and will fly ok with full tanks, but becomes tail heavy with the fuel gone.  Especially so with lots of heavy NERVs.   

4.  Angling the wings up (adding an "Angle of Incidence") as they attach to fuselage enables you to get lift with the fuselage flying at smaller angle of attack, reducing the drag penalty (but it is still there).

That makes orbit with about 1600 delta V left , and takes a while to accelerate.  

NOT MINE -   this looks like a mk2, but is mostly mk1 parts... hmm  lemmie try something ..

Edit - Also, I just had a brainwave.   Is it just me, or are these Juno engines at lot better than I previously thought for getting a single RAPIER design to mach over ?

20kn static thrust for 0.25 ton - panther in a/b has 130kn for 1.2 tons...     panther is only 33% better TWR and a lot harder to integrate in small ships. hmm

Edited October 8, 2018 by AeroGav

[sturmhauke]

Well I make a lot of Mk2 SSTOs, personally. That one I mentioned a couple pages back technically qualifies, but it doesn't handle all that well. It was originally designed as part of a larger LF-only mission, and was used to recover the crew after returning from Duna: https://imgur.com/a/uhwRA

Spoiler

Anyway, I made a new one. I call it the Gyrfalcon. Full album: https://imgur.com/a/fasm1kk

Spoiler

 

[Kerbolitto]

1 hour ago, sturmhauke said:

Anyway, I made a new one. I call it the Gyrfalcon. Full album: https://imgur.com/a/fasm1kk
 

  Hide contents

 

Wow that's a load of engines, must be cool to fly, but did you tried a cargo variant with this arrangement?

[sturmhauke]

2 minutes ago, Kerbolitto said:

Wow that's a load of engines, must be cool to fly, but did you tried a cargo variant with this arrangement?

Yeah it's definitely an application of the "moar boosters" school of kerbal engineering. I haven't done a cargo version yet, I could probably launch a small probe though if I swap out the cabin.

[AeroGav]

1 minute ago, sturmhauke said:

Yeah it's definitely an application of the "moar boosters" school of kerbal engineering. I haven't done a cargo version yet, I could probably launch a small probe though if I swap out the cabin.

Biggest issue I suspect would be that when the cargo bay is empty, you won't have enough mass upfront to balance all those engines at the back.   You could offset the nukes forward, but that might spoil the craft's looks.   Or you could swap out some rapiers for some panthers, which will reduce the weight of the total engine pack.

You can see that the RAPIER gets a huge boost to its power once you get supersonic (thrust multiplier goes to 8x at 900 m/s!) but it really dies off after 1200 no matter what,  so if you swap one or two RAPIER for panthers you'll get almost the same airbreathing top speed, but will shave a couple tons off the back end and also have stronger thrust for breaking mach 1.    In terms of liquid only cargo,  it can be done..https://kerbalx.com/AeroGav/Andromeda

Spoiler