Need help with Lathe Space Plane

[RedeyePete]

Hi all,

I am trying to build a Space Plane for Lathe.

It's 2 functions are to ferry crew (current version pictured = 8) into orbit to dock with an interplanetary shuttle and to supply the shuttle with fuel (no LOX).

I tried this with a modified version of Matt Lowne's Blunderberg 2. The stall speed for this craft on Lathe is about 120m/s and no matter how gently i touch down...

Well to quote Skipper from Madagascar 2:

"Touchdown gently, just kiss the ground, a little smooch"   ...... Kaboom!

So back to the drawing board, and now I'm modding and testing on Kerbin.

I have moved the wing tip Rapiers closer in thinking that the landing impact was snapping the wings.

Added more wings, bigger connards and more rear wheels.

So takeoff/stall speed is now about 80m/s (which I tested with less than 50% fuel load)

Is pretty stable in straight flight. Turning isn't the best and I need to concentrate or it will spin easily. Wet fish!

I have tried to land on the ground and not the runway many times and the result is always the same = Madagascar 2!

So any tip and pointers would be appreciated (that's "Tupps and Punters" if you're a Kiwi :)

If you know of an existing craft that fits the bill - I'm not too proud to pinch someone's design and mod to my liking.

I have been playing KSP (sandbox "Add more boosters!") for a few years now, but only recently started sticking wings on things.

Thank you in advance for any assistance, or ridicule!

https://imgur.com/sUj0qd8

 

[bewing]

Well, that thing is gigantic massive overkill, no matter what you are doing. And anything that big is gonna be really hard to land/ditch. I personally find it a lot easier to land in the water on laythe and then drive to shore.

Is this spaceplane also responsible for mining and converting the ore? How much LF are you requiring to transfer in a single trip?

And each additional kerbal that you add to the passenger list makes the task a lot harder.

So: are you willing to go with a much smaller spaceplane, that will be much easier to fly/land/ditch? With somewhat reduced passenger and other capabilities?

Would you be willing to go with a 3-kerbal design? What version of KSP are you on?

 

 

Edited April 29, 2018 by bewing

[steve_v]

3 hours ago, RedeyePete said:

I am trying to build a Space Plane for Lathe.

... supply the shuttle with fuel (no LOX).

To address the bigger picture: Where is your ore on Lathe?
If it's abundant at the polar ice shelf, you can land anything - even stuff that can't land on the KSC runway...

If, as in my current game, it's concentrated at the peaks, forget about landing aircraft that weigh more than 40t and can't VTOL or use 'chutes. Or be prepared to save-scum for a while.
If the resources are far from natural runways, I'd look for a better ISRU location. You have 3 other moons that are easier (and probably cheaper) for orbital refuelling.
 

Edited April 29, 2018 by steve_v

[RedeyePete]

To try and answer both posts, yes it is big, although I have seen videos of some ridiculously large planes with umpteen wings and engines fly and land - albeit on Kerbin. So I figured as long as I add enough wings, wheels and engines it will go. I tried putting floats on it but it was too heavy (I know I know)

Crew is 4 in the cockpit and 2 X 2 crew cabins in the cargo bay, which also houses a reaction wheel and big battery. No mining/refining equipment. The idea was to dock with the aquatic rover in the picture below - RHS. Both craft pictured have mining/refining onboard.

The ship to be refueled has a 10000 fuel tank. (Mk3 long,) 3 nuke engines and carries 4 + 16 Kerbals.

I do have a refueling setup on Pol. I just thought it would be nice to have one one on Lathe as well. I could also try using the smaller space plane in the picture to shuttle crew and some fuel and then top up at Pol for the trip home. It is easy to land and take off on land and water. Its purpose was to island hop and to visit the floating base, but I guess I can try to go into low orbit with it. However it has no docking port, so I would have to send up another one with a docking port.

KSP version = 1.4.3 on PC. Vanilla except for MechJeb.

Polar landings:

Is it easier to land at the poles? I'm not up on astrophysics much. If thats the case then I could land Mr heavy there. I could also land a mining/refining rover of a more basic type which I use on the other refueling planets/moons.

BTW the current location of everything is on the equator.

 

[bewing]

2 hours ago, RedeyePete said:

So I figured as long as I add enough wings, wheels and engines it will go.

That rule works for rockets ... but in general it doesn't work at all for SSTO spaceplanes. Getting moar payload to orbit with a spaceplane usually requires streamlining, simplifying, and eliminating -- rather than just moar boosters.

For an example, this will easily get 3 kerbals and 5000 units of LF to orbit at laythe (and it's not too hard to fly and land, even on kerbin):

(note that I just slapped that together quickly -- it really should be optimized more)

2 hours ago, RedeyePete said:

Is it easier to land at the poles? I'm not up on astrophysics much.

The ice sheets at the poles are perfectly flat. It's not astrophysics -- just the terrain. Altitude = 10 meters.

 

Edited April 29, 2018 by bewing

[Lego_Prodigy]

As I have now repeatedly proved to myself: SSTOs and big planes in general don't really seem to appreciate having tons of boosters attached to them, so try to get it as streamlined and efficient as possible, that way you conserve that oh-so-precious fuel. RAPIERs and Nerv rockets are highly recommended by me for both their highly efficient thrust-to-fuel usage rates. Have RAPIERS for a very efficient atmospheric thruster, then when they get too high to operate that is where you switch on your Nerv rockets for efficient interplanetary travel.

Also, be careful upon reentry with huge planes, and try to do some simulations in your head beforehand as to save some time and kerbals. 

[steve_v]

17 hours ago, RedeyePete said:

Is it easier to land at the poles?

Large areas are absolutely dead-flat ice sheets. Compared to mountainous islands, yeah, it's easier.

[RedeyePete]

Ok it looks like I'm going smaller. Having said that, have you all seen Matt Lowne's 124 seat SSTO to Lathe? and it wasn't a pole landing. He then followed up with a 500 seat to Lathe, and then there are the monster creations of Bradly Wistance. So big things can land. Food for thought!

I don't think that the ground around the space centre is that bumpy. I'll do some speed tests to see what happens.

Lathe polar landings are also an option, although it would mean having to set all my craft in a polar orbit, or...."oh the plane matching burn!"

Re my landing attempts on the equator, yes some were slamming into the side of the mountain, but some were on the flats, so there must be invisible bumps me thinks.

Is there anything to gain by tweaking the 2 landing wheel settings? I can't remember what they are off the top of my head.

[bewing]

3 hours ago, RedeyePete said:

Is there anything to gain by tweaking the 2 landing wheel settings?

There are 3 settings, actually. Friction, springs, and dampers. For the springs and dampers in version 1.4.3, no -- there's not much point. You used to need those to fix bouncing issues, but bouncing is mostly gone in 1.4.3.

For friction, yes. Setting the front gear to be low friction and the back gears to be high can help a lot to make your plane drive in a straight line, rather than swerving right or left.

 

[foamyesque]

8 hours ago, bewing said:

There are 3 settings, actually. Friction, springs, and dampers. For the springs and dampers in version 1.4.3, no -- there's not much point. You used to need those to fix bouncing issues, but bouncing is mostly gone in 1.4.3.

For friction, yes. Setting the front gear to be low friction and the back gears to be high can help a lot to make your plane drive in a straight line, rather than swerving right or left.

 

 

As always, I maintain this is a kludge solution that avoids thinking about the aerodynamic/wheel loading interactions that are the actual root cause.

[Lego_Prodigy]

13 hours ago, RedeyePete said:

 

Lathe polar landings are also an option, although it would mean having to set all my craft in a polar orbit, or...."oh the plane matching burn!"

 

I would probably attempt to regain control of the craft as an airplane and attempt to get as close to a polar trajectory as possible, but then fly to the poles should be like flying onto a salt flat

[RedeyePete]

So after gong back to the drawing board, testing, crashing I came up with this:

Its the one on the Left. Yeah I know its big but I could not help myself. Dry weight = 56t. Fully fueled = 137t.

I landed it at Lathe equator in one go (no mods)! That deserves a medal!

I still have to refuel and get into orbit, so I don't know how much fuel I will have to spare. But I was able to get about 1900 into Kerbin orbit, I tried a few different tank combinations and this one seemed the best.

 

[AeroGav]

That airplane has a massive, heavy fuselage and relatively small wings, of course it will have a high landing speed, though as you've not shared the craft file i can't check if problems with centre of mass and control assignments are making the problem worse.     That front wing only has a small elevon on it, so you're either not going to be able to pitch up much,  or if you do achieve large pitch angles it will  be from the much larger elevons on the rear wings,  however these get the nose up by pushing the tail down, and actually subtract from total lift.

One other thing,  wings have a much . much better fuel capacity to drag ratio than fuselage tanks.     They also provide lift.

Whilst they have a bit more dry mass than cylindrical tanks of the same capacity, the lower drag means less engines, which means less weight overall.    With generous wing area you can climb subsonic after takeoff into thinner air before levelling off to bust the sound barrier, which allows you to reduce the number of engines still more.

Matt Lowne tends to make extreme delta V flights (unrefulled to Eeloo, Moho etc) with negligible payload.  Most of the fuel is burnt out of the atmosphere, and he usually has just a single nerv pushing the 100 ton ship around in space.   So his priorities are different.

Have a look at my crew shuttle, the Griffon.  https://kerbalx.com/AeroGav/MK1-Griffon-Deep-Space-Crew-Shuttle

Two NERVs, one rapier and one panther clipped together.  No oxidizer required.   Has 11 seats and makes orbit with over 3000dv when flown correctly.   Has an inline clamp o tron and extra reaction wheels, but as it lacks RCS you're probably best off treating it as the passive partner in the docking maneuver and letting your orbital crew transfer vehicle/fuel bowser do the maneuvering.

42 m/s stall speed with full tanks on Laythe.

Note that you can make large spaceplanes with good landing characteristics,  but part counts get very high as you'll need to join lots of small wing parts together.

Note 2 -  I'd not taken this design to Laythe before and as expected, it would work better with a few small changes.    Firstly, the trailing edge wing panels can bust off on landing if you pitch up any more than this.     Maybe fit one of the small retactable landing gears at the back of the fuselage to prevent tail strikes,  or a pair of them as outrigger wheels at the trailing edge near the wing tips.     Second,  there's not much sunlight out on Jool,  so instead of solar panels in the service bay, fit an RTG  (though in practice it has enough battery to handle re-entry , with the panels stowed and engines off, just fine.   But its nice to have  a bit of juice left to run the landing lights at the end of it)

 

[RedeyePete]

So I have been flying my creation for some time now and I have mastered landing, take off and turns ok.

And I can say that I created it from scratch rather than borrowing someone else's design.

 

Tweaking or trying something different: I tend to only play in short bursts daily (have to do real world stuff), so by the time I have built something, tested it on Kerbin and flown it to the outer reaches, can take a week or longer.

So by the time I land at Lathe and find that I would like to change some small aspect of the craft, I'm more inclined to put up with small imperfections.

I would like extra lift (bigger wings) and better control, but will live with what I have for now.

 

Fuel storage: The main reason I went with fuselage tanks is for ease of fuel transfer. Fueling up is not a problem because I dock my mining/refiner up and it loads up every tank at the same time. But when I transfer fuel in orbit to another craft I found that storing fuel in multiple wing parts/tanks meant clicking on umpteen parts to transfer fuel. So my current version (described above) has 6 tanks (2 x fuselage & 4 x wing), whereas Matt's creation which I started this thread with has 30! Plus more as there was always some fuel left over and I could not locate where. Argh!

For the same reason I decided to mount the outer engines on structural cylinders and not (yet more) fuel tanks.

Thank you for sharing your craft, I have downloaded it and will have a look at it in the future. (priorities/time=later).

There are a lot of wing parts (tanks) and that worries me a little bit.

 

Whilst writing this post, I decided to go looking for the missing fuel in Matt's creation.

And here it is, haha

PS: it is docked to another ship, but the bulk of these tanks are Matt's. So can you spot the fuel?

Where's Waldo!

[AeroGav]

15 hours ago, RedeyePete said:

Fuel storage: The main reason I went with fuselage tanks is for ease of fuel transfer. Fueling up is not a problem because I dock my mining/refiner up and it loads up every tank at the same time. But when I transfer fuel in orbit to another craft I found that storing fuel in multiple wing parts/tanks meant clicking on umpteen parts to transfer fuel. So my current version (described above) has 6 tanks (2 x fuselage & 4 x wing), whereas Matt's creation which I started this thread with has 30! Plus more as there was always some fuel left over and I could not locate where. Argh!

I hadn't considered that.      You could make the fuel depot itself have only one tank (lock any others and just click on the transfer OUT button,  but i agree it'd be easier with less tanks on the shuttle)

[bewing]

Depending on CoM issues, you can set the priorities on the wing tanks so they drain first. Then all 10000 fuel that you are transporting is in the full main fuselage tanks.