Any Tips for Spaceplanes?

[CerpPad]

im a regular player of ksp, other than i have little knowlage of how to make SSTO's and space planes. Any tips? i know the basics but i do want to get better at building them.

 

 

 

Thanks, any help is appreciated !

 

[Snark]

Hello, and welcome to the forums!

Moving this question about how to play the game to Gameplay Questions.

[Mike Mars]

2 hours ago, CerpPad said:

im a regular player of ksp, other than i have little knowlage of how to make SSTO's and space planes. Any tips? i know the basics but i do want to get better at building them.

 

 

 

Thanks, any help is appreciated !

 

There are tons of helpful videos on Youtube.

Also, checkout the spacecraft exchange for examples of various designs that work well.

Have fun.

MM

[bewing]

Well, my #1 tip is to avoid MK2 parts. MK2 parts are very pretty -- but they are heavy for what they do, and they are exceptionally draggy. MK1 parts efficiently do everything that an MK2 part does (except for thermal resistance). MK3 parts will get a huge mass of stuff into space, for a huge amount of money.

My #2 tip is to not expect too much from your first 100 designs. Most SSTO spaceplanes ever designed just barely get to LKO. If you're thinking "ooh, I'll make an SSTO and fly it to Duna!" -- then you need a wishful-thinking-ectomy.

My #3 tip is to reduce mass and drag in your design. Then do it again. Then again. And again.  As I said in tip #2, a typical SSTO design from a non-expert will just barely fulfill its function. Or maybe not quite fulfill it. To make better designs, you need to be ruthless. You can't expect it to be pretty -- you have to chop off all the pretty parts. You can't expect it to have impressive performance -- you have to minimize the number of engines and control surfaces. Etc. Get used to doing more with less. And then with much less.

My #4 tip is to expect to spend several hundred hours practicing the landings. You need to learn the proper landmarks, speeds, and altitudes for your descent.

 

 

 

[Gargamel]

2 hours ago, CerpPad said:

Any tips?

Well, we can start with an aerodynamic nose cone:

Nice and round, makes a good tip of the plane...

 

There's also the Advanced nose cone, if your plane is little more techy:

Bit heavier, but still will lead your plane nicely through the air.

 

But if you have a small plane, the small nose cone will do nicely too!

 

[bewing]

As far as that tip goes, I'm going to recommend a shock cone or klaw.

[AeroGav]

i've written loads on this subject and posted two lengthy guides in the tutorials section,   though the first spends much of its time talking about how to get one working even if you went against common sense and used a mk2  fuselage, though i later added extra info to cover other types. 

   More recently i posted  a  guide on making low-ish tech career mode planes with mk1 fuselages and panther and nerv engines only.

Chemical fuelled designs, which is how most people start,  generally use  rapiers, which are very thirsty in rocket mode,  so they need quite a bit of fuel.   I tend not to build these any more so am not the best person to offer advice.

NERV only designs (no oxidizer) have much more efficient engines,  and can make orbit comfortably with a fuel mass fraction on takeoff of only 33%, similar to a commercial airliner.  But,  these engines are weak and heavy,  so in rocket mode it will have a thrust to weight ratio of between 0.3 and 0.6 to 1 - similar to a commercial airliner or supersonic transport/supersonic bomber.     Therefore, it follows that the designs that work best look less Kerbal and more like real airplanes.   Like a real airplane, it needs to have a lift to drag ratio of 3 to 1 or better.   NERV designs are much less sensitive to weight and fuel fraction,  but very sensitive to lift, drag and aerodynamic.

So my tips -

1.  Build a good airplane first.    Plenty of lift, low drag, and stable.  If you're fighting the controls and jerking around all the way up ,  that creates loads of extra drag.   

2.  Its centre of mass  must not shift as fuel burns off or the payload empties.   It needs to remain equally controllable throughout the ascent and the whole point of a spaceplane is that is is supposed to be re-usable.

3.  Most drag comes from fuselage, even skinny mk1 stuff. 

There are some mods that greatly reduce the trial and error nature of flying spaceplanes. 

1.  RCS Build aid, which you might already be using  since it helps with the zero fuel balance issue

 2.  Kerbal Wind Tunnel,   helps you know if your design has enough thrust

3.  CorrectCoL  (Correct Centre of Lift) much more accurate calculates your plane's blue centre of lift marker than the stock one..  It also shows a graph of nose up/down torque from aero forces vs pitch angle.  You can use this to tweak your airplane to hold a steady cruising  / climbing attitude with no input from the pilot,  and  it  warns you if your plane has a nasty tendency to go unstable and deep stall if your pitch up too much.

 

I cannot recommend these mods enough.    Everything I built using these mods can go to orbit the first time I launch it.    Of course, I usually discover minor annoyances with staging, action groups, or the landing gear and revert a few times because of these,  usually before the plane has gone above 200m.      But nothing that would prevent a successful flight.       Without these mods,  despite all my in game experience, i am likely to spend most of a day launching and reverting.

 

[nsgallup]

The problem I always have is bouncy landing gear, either it sags on takeoff to one side and causes a crash, or if I design it with overly large gear to prevent that it bounces like a pogo stick on landing.

[FrostedShoe]

I dont understand the mk2 hate. For the last year, mk2 planes are the only ones i could get into orbit - its only in the last month i have managed to get a mk3 to perform as well and i still can get a decent and useful mk1 into orbit.

But then again i might just be a bit odd.

I do have a tip though - give the plane one use (ie passenger shuttle) and build around that. Dont try and do everything. Im trying to build a mk3 VTOL refueling science SSTO and its almost done but its not worth the grey hairs.

[AeroGav]

The benefits of a high lift, low drag mk1 design 

https://kerbalx.com/AeroGav/Sparrow

[TheFlyingKerman]

10 hours ago, bewing said:

Most SSTO spaceplanes ever designed just barely get to LKO.

That is the most efficient use of a spaceplane... The spaceplane can then carry a transfer stage as cargo that goes everywhere.

[ZL647]

To echo the common mantra, less is more. 

I disagree with the mk2 hate since aesthetics are very very important to me and you can still get them to work fine. I've got a mk2 ssto that can take off to orbit, get to minmus, land, take back off back to kerbin, and land there. 

Dont expect to do much with a spaceplane ssto though when it comes to cargo, or making it past Kerbins SOI. To do that you'll usually need to do some orbital refueling. 

You can make one that can carry cargo, but it wont make it much beyond orbit. You can make one that goes farther, but you wont carry much useful cargo. Still fun though.

I built a docking ring like the star wars jedi fighters for interplanetary travel.

Main things to consider are drag, lift, and weight. The more lift you have, the weaker jet stage you can get away with. The lower your drag and weight, the weaker both stages can be and still push the craft to orbit.

Also, you're likely to lose the first many planes you build. Aerodynamics in ksp are a bit wonky and if you though rocket wobble was a challenge, well plane flipping is even more common when you first start. Planes are also much more prone to reentry burn up or g-force rapid unplanned disassembly  if you dont follow a correct flight path. 

Edited October 31, 2018 by ZL647

[AeroGav]

10 hours ago, TheFlyingKerman said:

That is the most efficient use of a spaceplane... The spaceplane can then carry a transfer stage as cargo that goes everywhere.

The counterpoint to  this, is that the cargo bay adds such a huge drag penalty to the space plane,   it can sometimes be easier to just send the  whole airplane to where you are going and leave off the anchor mk2 cargo bay

In the spacecraft exchange,  i shared a mid tech space plane with 2 droppable panthers and 3 nervs,  that reaches orbit with 4700 delta v left in its tanks.  You asked me to create a cargo ssto version of this craft which i did, by removing the passenger cabin,  some of the liquid fuel tanks and adding cargo bays.    The goal was to lift the equivalent of 3 mk1 sized fuel tanks.       The cargo ssto variant  ,  even when laden,   weighed only 41 tons vs 46.7 tons of the interplanetary variant,  but it suffers from more than twice the drag on account of those infernal cargo bays

compare this 

to this -

 

Same speed and height, look at the drag number in the data panel though... ouch !  The cargo version labors and labours against the drag, eventually running out of fuel about 50 m/s short of an orbit with the design payload.    The interplanetary one however...

Honestly, if i was looking to go beyond Duna with this airplane,  i'd probably look to replacing some of those mk1 tanks with the small resource converter and a small drill in a service bay, and have it mine itself some fuel on Minmus or Duna or wherever takes your fancy.    Next stop Eeloo, if that's your thing..

[Vanamonde]

My best advice would be simply to not get discouraged. I have been playing this game for 6 years, and most of my SSTO designs still fail. Badly. But it sure is nice when they do. 

[Chel]

For spaceplanes, I would go with a combination of the Panther and RAPIER engines. Use both engines to get altitude quickly, and then shut down the Panther when you are leaving the atmosphere, switching the RAPIER to rocket mode. I've used it on most of my designs, and it works pretty well

[AeroGav]

21 minutes ago, The_Cat_In_Space said:

For spaceplanes, I would go with a combination of the Panther and RAPIER engines. Use both engines to get altitude quickly, and then shut down the Panther when you are leaving the atmosphere, switching the RAPIER to rocket mode. I've used it on most of my designs, and it works pretty well

RAPIER engines get an insane Ramjet boost effect once you go over mach 1,  it can cause their thrust to peak at around 8x what it would otherwise be at that altitude (the absolute value is capped i believe, somewhere around 400kn).  Also once switched to close cycle mode they kick out 180kn which is pretty decent too.    However, sea level static thrust is only around 110 or so.     So the problem is getting supersonic,  if you have enough engine and good enough aerodynamics/flight profile to get to mach 1,  after that you'll have far more thrust than you'll ever need, the only question is, will the fuel last?

This is why replacing half your rapiers with panthers can make sense.  Panthers have the highest twr of any jet engine up to about mach 1.6 , by using this combo,  you can get away with a lighter overall engine package.

I'm not sure why you need to worry about shutting them down though - in the stock game,  they just flame out and no harm is done.  Thtree are some mods that cause engines to overheat and explode if you take them beyond their design mach number ofc.

[Pecan]

SSTOs beyond LKO are pointless except for Laythe, where they can jet again.  Also, of course, except just for the fun of it.

Beyond LKO use and re-use transfer spacecraft - tugs and shuttles that never ever land - and specific landers for the planets/moons in which you're interested.
That way the only things that have to come up or down at Kerbin, by SSTO, are fuel and crew.  With ISRU that becomes only crew.
Passenger SSTOs are relatively easy and don't have to be particularly big (career tourist missions likely being the biggest demand).
Tanker SSTOs can just have over-large tanks as part of their design and transfer the excess when you dock - either with a station or with your reusable shuttles/tugs.  That way you don't need cargo bays as such.
Actual cargo SSTOs are best just for things you want to construct in orbit but can't get there themselves - which would be parts of stations and, probably, tugs.

What's left is one-off mission 'specials' and, since they're for one-off missions, there's not much point in making them reusable.

Now, I haven't built a single SSTO since the game's been in full release.  I really should ...

[bewing]

3 hours ago, Pecan said:

SSTOs beyond LKO are pointless except for Laythe

Gotta disagree with this. An SSTO landed on any moon is a rover, and a very nice stable one at that. Extremely useful for cruising around biomes and collecting experiments.

 

[Pecan]

17 hours ago, bewing said:

Gotta disagree with this. An SSTO landed on any moon is a rover, and a very nice stable one at that. Extremely useful for cruising around biomes and collecting experiments.

 

Then we shall have to agree to disagree.  A lander with wheels is a rover and should be both a lot more fuel-efficient and more stable than a tricycle carrying around excess sticky-out bits it doesn't need.  That said, if you aren't building a 'permanent' infrastructure and only want to go somewhere once or twice it's not worth making and hauling the station/lander stuff and a one-off SSTO is better.

[KevinSalyer]

Hahahah, I am also new and I think that avoiding MK2 parts is really a good suggestion.

[AeroGav]

@Pecan

A thing i've found in my career games, when i've been limited to the smallest retractable gear for a while,  is that 5 small  gears is much more stable than 3 medium.    One on the nose for steering , like on conventional tricycle, friction control set to low (we want understeer rather than oversteer - it's not  a drift car).             Two attached to the wing close to the centre of mass, as close to the wing tips as possible so it can't tip over onto either wing.    Then two towards the rear to prevent tail strikes, maybe attached to tailplane and with friction control set to max (again, to promote understeer).         Landing gear don't add much drag when retracted so fit more if this is a consideratoin.   Ground clearance can be an issue with the small ones,   that is the only problem.   Also you'll want to offset the rear ones upwards as much as possible so it sits on the ground with a slightly nose high attitude,   or takeoff speeds can be increased (unless you've got a really strong pair of canards or vernor engines that can lift the nose off the ground - the rear anti tailstrike wheels will prevent you pushing the tail down to get the nose up on rotation otherwise)